Comets and asteroids hitting Earth

The key thing is justification. Try justifying the effort needed 'just in case' something happens. Try getting all interested parties buying-in to the scheme and contributing a fair share. If such a hazardous object were to crash into, oh let's say for the purposes of illustration, a desert in Namibia, would communities across the world be as interested in underwriting it as they would be if it were to impact upon Johannesburg, Paris or Beijing (no offence intended - question intended for illustrative purposes only)? The idealist would have a go now, perhaps. The realist would start assessing the risk and do it, or not as the case would be, should the risk become significant at some point in the future.

http://en.wikipedia.org/wiki/Near-Earth_Objects makes interesting reading, as does http://en.wikipedia.org/wiki/99942_Apophis.

There are threats more significant, and more immediate, than a risk of impact with a near-earth object. http://archives.cnn.com/2001/TECH/science/08/29/tidal.wave/ points out that La Palma presents a significant threat. But the television programme wasn't about that, was it?

I may be mistaken, but I seem to recall a near miss a few years ago, of a sizable chunk, of like 30,000 or 60,000 miles that would not have been catastrophic. But then how bad does it have to be if it hits the spinning marble in your back yard and ONLY takes out one minor city. So the sky is a bit hazy for a couple of months. We'll get over it.

If this was discussed on the show, forgive me. I was having a weak bladder during the show.

It's a good idea - but it requires a government with vision. And there just aren't any of those around right now.

Just tell Congress that asteroids are like the hemorrhoids they've developed after all these years of sitting on their collective butts, excepts they hurt a lot more!!!

There was just something on the news about this and that there is an action plan in motion to prepare for this issue.

So, it is in the works.

Whose news? It didn't cross the 'pond'.

Didn't see it in the "nightly news" on this side of the pond either.

As long as it hits Wickford instead of Basildon, who gives a stuff? <Splutter>

"action plan "

When I first heard of the term action plan, I though that was a good phase,..... sounds like things are moving along,....... I'm on it,........ stop asking me questions I don't have answers for........

The way the environment or humanity is abused in some places on earth it is even more scary that an object from space is most probably not going to strike there.

Where would you drop an asteroid if you could?

What about one (coming in at an angle) to open a new bigger waterway between the Red sea and the Mediterranean. The flow of water may flush out the pollution in the Med.

Nice to see you were paying attention in the one ton meteor class

Well, look at the sunny side. Lets say that someone miscalculated and that the orbital velocity of Apophis at earth orbital radius is less than the escape velocity at the passing range. Result - global warming goes away?

Makes the rest of your problems seem less important doesn't it.

As for we vermin, we've survived them before and we'll survive them again.

Very True Vermin (by the way you have stopped bouncing again)

But as we down on the underneath side should be alright as anything falling down would get you guys up there first and then maybe bounce of

If you can find a way that a few people can get really rich on it, maybe get the oil companies in on the deal, then I'm sure we could develop serious interest in the project.

Otherwise we are to busy destroying the planet and killing each other to worry about saving it.

It is my understanding that a metallic asteroid one quarter of a mile in diameter has an estimated 20 metric tons of the gold and platinum group in it.

Not to mention the tailings (metal) cost $10,000 US federal reserve notes to get into orbit from Earth.

If some one had a feasible plan, greed will motivate the politicians and their lobbing cronies.

Brad

Now we're talking!

Is that the Hindenburg in your avatar? That gives me some ideas for my next animation!

Avatar looks like a Led Zep cover.

Yep, right off of the Led Zepplin II album cover.

Brad

Won't work unless it puts money in to the politicians pockets and I don't see how it would. Might could sell it if you can fiqure out how to accomplish lining their pockets.

Just give the recovery contract to Haliburton!!

Gee!! I thought I was the only one that disliked politicians and power mongers. Perhaps we should all join forces to figure out how to defeat the bas--rds. Maybe not working on science that can destroy the planet might be a start.

It's time to run up all my credit cards and party like there's no tomorrow. YEEE HA!!!

If you going to have a big Party come down to Fiji we realy know how to party. And we will let you pay the bill

Tonights top story, the end of the World. Film at 11:00.

Fiji? No. Make it Basildon. Pleeeeeeeeeeeeeze? <Cough>

"The chance to see anything comparable again is very small. If necessary some of the existing ICBMs can easily be reconfigured with a much smaller warhead to give a big impulse to the oncoming threat."

What? Thats wishful dreaming. Oh and 50 meter object incinerating Europe? Not.

So please tell us how a small warhead is going to impart significant impulse on a body thats rotating. And by the way, Apophis is closer to 300 meters in diameter than 50.

What is it that imparts that impulse? Please share the mechanics with us. I just can't wait for the enlightenment.

We have doable options with a reasonable chance of success , nuclear explosive deflection is not one of them.

I've read the congressional report AND the NASA internal report on which it is based. It well serves the interests of the status quo; but it leaves our children very vulnerable.

Until the "Pioneer Anomaly" is solved and factored into the orbital predictions for Apophis, nobody has really got a good handle how close it's coming, or if its coming close at all, this time. What is known is its orbital plane, and that sir, clearly indicates we WILL deal with Apophis or take the hit at some time in our future.

"Its been 13 million years", Ya. You betcha.

"the geologists that probed the crater are claiming that any object this size will penetrate the earths crust down to around 10km and then explode with an incredible explosion. Most of the explosion crater will be filled up soon by downcoming stone, pebbles and small debris."

Based on what entry angle? Based on what relative velocity? Based on what makeup?

A probability of 1 for a Yellowstone super eruption?

Numbers fail to impress me without showing the math.

We can do asteroid deflection and in doing so develop technologies that can serve our species or we can focus on next years 4th fiscal quarter.

JAXA and the Muses C program shows how far we have come. We can do this.

Hi Gavilan, you wrote: "Until the "Pioneer Anomaly" is solved and factored into the orbital predictions for Apophis, nobody has really got a good handle how close it's coming, or if its coming close at all, this time."

I don't think the 'Pioneer Anomaly' is a factor - Apophis does not go far enough from the Sun. What is a worry is that it could go into 'orbital resonance' with Earth, which will significantly increase the impact probability in the future.

I think we have the technology to deflect an object of ~10¹⁰ kg enough to save us, provided that we know it's trajectory very accurately, long enough in advance. Then a very small deflection makes one big difference in the miss-distance, but it is still a very expensive mission. That's why the planetary society is campaigning for a tracking device to be put on Apophis. You can't spend that kind a money unless you are sure of the effect and that you won't just alter it so that it will then hit us.

Jorrie

Thanks for the great reply Jorrie.

The orbital plane of Apophis appears to be clearly defined as is evidenced by the value given for "width" at http://neo.jpl.nasa.gov/risk/a99942.html.

The value for the "Stretch LOV" indicates an uncertainty in either its orbital eccentricity or orbital period.

If you could spare a few moments, please consider the following as a deflection strategy. It eliminates the need to carry rocket fuel to the asteroid; using electrical power from a nuclear power source to provide power for a field reaction propulsion scheme or the orbital energy of the asteroid itself as the prime energy source through the process of dynamic braking. In the case of dynamic braking the Sun's Magnetic Field serves as the excitation field and the asteroid velocity cutting that field at near the optimum induction angle provides the rate of change for induction. The dynamic braking energy is dissipated by radiative cooling (the amount of power dissipated increases as the 4th power of the temperature of the grid), used to power a electromagnetic field reaction system, used to power a mass driver that uses the asteroid body as a source of reaction mass, or any or all of these in combination.

Remember that Apophis doesn't go away with a simple small imparted delta V, because of its orbital plane; it only puts it off until later. It's orbit crosses earths orbital radius twice every orbit with an earth orbit intersect on plane once each period. A reasonable and quite possible permanent fix is to change its orbital eccentricity so that it would impact Venus on its next close approach. It appears to be coplanar with Venus which means there is no need for an energy intensive orbital plane change. It also appears we may still have time to do that mission if we get started now.

What are the limits to power generation/dissipation in a dynamic braking approach?

Page down to the "Electro-dynamic Braking:" section of the essay and please look at the section dealing with "Orbital Station Maintenance and Altering Eccentricity." The last paragraph sums up the deflection strategy.

Any chance you would be willing to comment on this?

Electro-magnetic Propulsion and Electro-dynamic Braking in Space Applications. – By Mark J. Carter

Space propulsion has changed little since mankind took its first tentative steps into space. Even with the incremental advances in the efficiency of chemical fuels; the basic nature of rocketry is still defined by the basic Delta V Rocket Equation with all its limitations; be it the powerful boosters used to obtain orbital velocity or the low impulse Ion Thrusters used to power deep space missions. This Neanderthal approach to propulsion limits both the potential flight parameters of deep space missions and the life span of earth orbiting satellites.

In earth orbiting satellites, the electronics of the satellite may last indefinitely; but the usable lifespan of that satellite is limited by the availability of on-board propellants used for orbital maintenance. Once the chemical propellant is exhausted, the satellite no longer has the capability of maintaining proper station.

The International Space Station is dependent upon chemical propellants to offset orbital decay. The need and use of these chemical propellants increases the potential for catastrophic accident, increases the cost of operational maintenance, and requires the commitment of launch capacity for that purpose.

Interplanetary and deep space missions face similar limitations inherent to dependence on chemical propellants. Although gravitational assist has been a regular tool used in both navigation and imparting changes in specific orbital energy; obtainable velocities, launch windows, and other flight parameters remain severely limited by dependence upon the same Newtonian Propulsion methods used by the ancient Chinese to power their rudimentary rockets. Even Ion Propulsion, which uses electro-magnetic acceleration of the ion fuel to achieve impulse, is still a type of Newtonian Propulsion where the total energy imparted is limited by exhaust velocity and total available fuel mass as defined by the basic rocket equation. Newtonian Propulsion may have gotten us to earth orbit and beyond; but it will be Electro-magnetic propulsion that will carry us to the stars. In the mean time, its development will allow us to achieve flight parameters unimaginable when considering only chemical propellants.

The Ampere Defined As Magnetic Force:

Prior to 1948 the ampere was defined, based on Faraday's Law Of Electrolysis, as the amount of unvarying current, that when passing through a solution of silver nitrate, deposits silver at a rate of .00111800 grams per second.

The ampere was redefined in 1948 as the amount of unvarying current, that when being carried by two infinitely long conductors separated by one meter, would generate a magnetic force between the conductors of 2 X 10-7 Newton per meter of length. This is the Standard International definition of an Ampere.

Electro-magnetic Propulsion and it's inverse, Electro-dynamic Braking, when combined with the now and near term future technologies related to super conductivity, dielectric capacitance, and other related technologies; will introduce a new paradigm in space propulsion.

The Fundamentals Described As A Space Based Experiment:

A simple space based experiment to demonstrate the basic principles of electro-magnetic propulsion is easily imagined. In this experiment a simple coil, a number of accelerometers, a polarity reversing switch, power source, and radio telemetry is used to determine the earth's electro-magnetic field strength at the range of the experimental package. It would be most advantageous if the coil length is as great as possible. The coil is circuited in series with the polarity reversing switch and the power source. The accelerometers serve to activate the polarity reversing switch. The experiment is then suitably packaged and conventionally launched to a low inclination orbit. The experimental package is then positioned so that the field coil of the package is aligned so the coil will be at maximum repulsion with earth's electro-magnetic field when the coil circuit is initially energized.

So positioned, when the switch is initially closed and power is applied to the coil there will be two vector forces acting on the coil.

Since the coil is aligned in repulsion with earth field, one force will be acting along a line that is perpendicular to the earth's North/South polarity (approximating the line of orbital radius) and will translate to an acceleration vectored along the orbital radius converting circuit energy to increased gravitational potential.

The other force acting on the field coil will translate to torque causing the field coil to begin to rotate about the central axis of the coil length as it begins to align towards the magnetic equilibrium position relative to earth field; that being one of maximum attraction and 180 degrees relative to the maximum repulsive position. In doing so, some of the electrical energy supplied to the field coil will be converted to kinetic rotational energy of the package. As the field coil rotates towards the equilibrium position, the accelerometer reading acceleration along the line of the orbital radius will sense zero acceleration as the angular relationship between the field coil and the earth's North/South polarity reaches 90 degrees relative to the maximum repulsion or attraction position. The coil polarity control circuit is designed to reverse the polarity of the field coil at this position, thus maintaining a repulsive relationship as the rotational inertia carries the coil package through the 90 degree position.

The timing of the polarity reversing switch is critical for maintaining repulsion; avoid dampening the oscillation, or allowing the package to continue increasing its spin velocity.

As power is applied to the circuit, energy begins to be converted thru linear and rotational acceleration to the gravitational and rotational energy of the package. Without empirical proof, I suggest that the applied coil circuit energy will be the sum of the energy translated to gravitational potential and rotational kinetic energy. That the linear force acting along the line of orbital radius will vary as the cosine of the relative field angle while the force translated to torque about the center axis of the coil will vary as a sine function of the relative field angle. The linear force will approximate the force at 0 degrees (maximum repulsion) times the cosine of the relative field angle. The force imparting torque about the center axis of the field coil will approximate the force imparting torque about the center axis of the field coil at 90 degrees (maximum torque) times the sine of the relative field angle.

Where the moment of inertia of the experimental package is known, Earth's Electro-Magnetic Field Strength can be derived from acceleration and circuit power.

Attitude Determination and Control Applications On Board Earth Based Satellites:

Using the Earth's magnetic field as a reaction field in attitude determination and control of earth orbiting satellites was first proposed in the early 1960's. Current applications include the sensing of relative field angle to determine satellite attitude and the use of electro-magnets to maintain and change satellite attitude. The author believes that widespread application may be limited by the orbital perturbation that would result from earth field/satellite field interaction. Electro-magnetic attitude control, without an Electro-magnetic orbital maintenance regime, would require expenditure of thruster fuel to maintain orbital station. To make electro-magnetic attitude determination and control a viable application, a means of offsetting the orbital perturbation using electro-magnetic propulsive technology rather than chemical thrusters must be developed. Also, the mass and volume fractions of electro-magnetic attitude determination and control technologies must be brought to values where the advantages of the technology offset the mass and volume fractions required. A primary advantage of Electro-magnetic propulsive methods for this application is that it can be accomplished without mechanical components as required in momentum and reaction wheel technology or the fuel and valving required for thrusters. This resulting increase in reliability will serve as further incentive to apply electro-magnetic technology to attitude control.

Increasing Hyperbolic Excess Speed in departure from Earth's sphere of gravitational influence:

By definition, for an Earth orbital escape mission, the Hyperbolic Excess Speed is the residual speed that remains as the space craft climbs out of the Earth's gravity well. Simply stated, it approximates the rocket burn out velocity minus the escape velocity at the range of burnout.

It may be possible to increase the Hyperbolic Excess Speed by using magnetic repulsive force generated by propulsion coils aboard the spacecraft acting against Earth's electromagnetic field. The repulsive force would offset the deceleration of gravity as the space craft moves out of the Earth's gravity well. This offsetting force would leave more residual or "Hyperbolic Excess Speed" as the space craft leaves the gravitational sphere of influence. If the magnetic repulsive force exceeds the gravitational force, then this force would continue to accelerate the space craft, imparting additional mechanical energy. The additional specific mechanical energy conserved or imparted would approximate the applied circuit energy calculated as applied power times time.

By thoughtful design, repulsion can be maintained without using an oscillating polarity strategy (as described in the Space Based Experiment), thus maintaining constant space craft attitude.

Increasing Hyperbolic Excess Speed in Gravity Assist Maneuvers:

A number of deep space missions have used Gravity Assist to either increase or decrease the mechanical energy of the space craft. Although such maneuvers use the gravitational acceleration of the assisting planet to increase or decrease the specific mechanical energy of the space craft, the Hyperbolic Excess Speed of the space craft relative to the assisting planet remains unchanged. The reason for this is the relative velocity between the space craft and the assisting planet gained by the acceleration of gravity on the approach trajectory is lost to that same gravitational force on the departure trajectory.

By using Electro-magnetic propulsion, additional hyperbolic excess speed can be imparted when the assisting planet has a significant magnetic field. In this application the propulsion coil(s) are used in attraction polarity on the approach to the assisting planet. This increases the acceleration above that imparted by gravity alone. As the space craft begins its departure trajectory from the assisting planet the relative polarity is reversed and maintained in repulsion; offsetting the deceleration imparted by gravity, thus conserving the Hyperbolic Excess Speed of the spacecraft relative to the assisting planet by adding the energy imparted by the electro-magnetic system to the specific mechanical energy of the space craft.

Orbital Station Maintenance and Altering Eccentricity:

By using properly timed Electro-magnetic Impulse, in repulsion and in attraction, possibly combined with Electro-dynamic braking; total orbital energy and eccentricity of orbit may be altered. Conceptualization of this regime involves both magnetic impulse and dynamic-braking at specific points in the orbit including using the induced dynamic-braking energy to produce vectored magnetic impulse.

Total Orbital Energy, often referred to as Specific Mechanical Energy, has two components. The kinetic energy per unit mass and the gravitational potential per unit mass. The sum of these two variables equals the specific mechanical energy. In an orbiting object, when not acted on by any other force other than the gravity of the prime focus object, this Specific Mechanical Energy remains constant. In elliptical orbits this energy translates between kinetic energy and potential energy as described by Kepler's second law.

Introductory texts on Astro-dynamics teach that in most cases, a change in the Specific Mechanical Energy of a satellite is accomplished by imparting impulse along the velocity vector. This change in velocity translates to a change in the radius of orbit. By imparting impulse along the velocity vector the Specific Mechanical Energy can be either increased or decreased with the timing of the impulse relative to periapsis or apoapsis determining orbital eccentricity. Changes in apoapsis are made by imparting impulse at periapsis while impulse to change periapsis is imparted at apoapsis.

In both cases, the impulse either increases or decreases the total orbital energy by imparting a change in orbital velocity. This change in velocity is then translated to a change in gravitational potential by altering the semi-major axis.

It is proposed that changes in the orbital energy of the space craft can be made using Electro-magnetic technology; increasing the orbital energy by increasing the semi-major axis directly through repulsive interaction with earth field or decreasing orbital energy by electro-dynamic braking.

In a low inclination orbit, generating a magnetic field in repulsion with earth field will begin to impart impulse along the orbital radius, increasing the semi-major axis, thus directly increasing the gravitational potential component of the total orbital energy (Specific Mechanical Energy). By imparting magnetic impulse during the entire orbital period, or applying bit impulse relative to apoapsis and periapsis, the orbit can be stepped up and eccentricity controlled. If using conventional chemical propellants, stepping up the orbit is accomplished by increasing the velocity component, translating to gravitational potential, with the impulses timed relative to apoapsis and periapsis to control eccentricity. Experimentation with generating magnetic field in attraction to earth field may yield some surprising results. How will the circuit energy be conserved?

Electro-dynamic braking of the space craft will impart a braking force along the vector of orbital velocity, decreasing the orbital energy, and translated a reduction in gravitational potential. By timing the Electro-dynamic braking inputs relative to periapsis and apoapsis the orbit can be stepped down and eccentricity controlled. Using chemical propellants stepping down the orbit is accomplished by impulse opposite the velocity vector, slowing the spacecraft. The timing of braking impulse relative to periapsis and apoapsis will allow control orbital eccentricity.

Electro-dynamic Braking:

All electro-magnetic induction processes are composed of three primary components; the excitation field, the inductor, and rate of change. The rate of change can be supplied by velocity of the inductor relative to the excitation field, the oscillation of the excitation field in the presence of the inductor, or combination of the two.

For those of you who may have had the opportunity to empirically experience the fundamental physics of induction through experimentation with a simple hand crank generator, that lesson showed the relationship of circuit load to cranking force, and can be extrapolated to the inductive braking of a satellite or asteroid.

In the hand cranked generator, the permanent magnet supplied the excitation field for the induction process. The rotor, turning a coil through that excitation field, supplied the "Rate of Change" required for induction. The faster the rotor was turned the higher the voltage that was developed across the leads of the generator. When there was no "load" across those leads the generator was very easy to crank even though the "potential" or "voltage" was still being developed across the leads. But when a load, such as a light bulb, was placed in a circuit across the leads of the generator, that bulb created a "load" in the circuit. That "load" was the energy being dissipated in the bulb through resistive heating and light production. Supplying the circuit load with energy required greater force in cranking the generator. The force applied to the handle of the generator was converted to torque by the lever arm (handle) which spun the inductors (coils) at near right angles relative to the magnetic field (excitation field) of the stator. The energy required to spin the rotor was nearly equal to the energy being dissipated by the circuit "load".

In Electro-dynamic braking applications the solar or planet field will provide the excitation field while coils aboard the spacecraft, or the spacecraft/asteroid body itself, serves as the inductor. The spacecraft/asteroid velocity cutting the flux lines of the Solar or Planet field will supply the rate of change component. This induction process will generate a braking force as is inherent in any electro-magnetic induction process. The induced energy will then be dissipated through circuits designed to generate heat for radiative dissipation, conversion to vectored propulsive impulse, or stored for peak power/subsystem applications. Applications of Electro-dynamic braking will include adjustments in semi-major axis and eccentricity; as well as braking to orbit in planetary missions.

Because the orbital velocity of a satellite or asteroid is so high, significant voltage can be developed even though the excitation field may be very weak. The "tether" experiments flown on the space shuttle clearly indicate the validity and potential application of this technology.

Imparting Orbital Escape Energy:

Escape speed, as given in reference material, gives the escape speed at the surface of the body referenced. This escape speed decreases as the radius of orbit increases. If an orbiting spacecraft is given continual magnetic impulse to step up the orbital radius, at some point, the orbital velocity of the spacecraft will approach and then exceed the escape speed at range, thus allowing the spacecraft to "escape" the gravitational sphere of influence of the prime focus body (planet or Sun). Using such a method, a satellite may be given Excess Hyperbolic Speed, not by imparting additional velocity, but by imparting additional gravitational potential until the Specific Mechanical Energy of the spacecraft exceeds that needed to escape the gravitational sphere of influence of the prime focus body.

By initiating high power Electromagnetic impulse in low earth orbit, very high Excess Hyperbolic Speeds may be obtained.

Braking to Orbit:

A space craft approaching Jupiter, or other target body, may have too much energy to establish orbit. By using Electromagnetic Propulsive methods it may be possible to alter both the magnitude and vector of the approach velocity; thus giving an alternative to using chemical propellants or atmospheric braking as the sole methods of reducing the energy of the spacecraft so that it can be captured by the intended prime focus body.

Deep Space Propulsion and Navigation:

In propulsion and Navigation, Electro-magnetic Propulsion will use electrical energy generated by an on-board power source to generate electromagnetic field(s) which will impart impulse through combined interaction with the magnetic fields of the Earth, Sun, Planets, and eventually, galactic fields.

Force vectoring will be obtained by very precise control of field strength, field angle, and action time relative to those reaction fields. Vector control, when within the magnetic sphere of influence of multiple field sources; will utilize the relationship of reaction field range, reaction field angle, and time span of power input to sum the force vectors from two or more reaction fields to obtain the desired net force vector. An example would be to act in repulsion of earth field for a fixed time at a fixed power and then act in attraction to Sun field for a fixed time at a fixed power. The net vector force would be the vector sum of the two forces. Because of the cosine relationship of repulsion/attraction force to the relative angle between the propulsion coil(s) and fields of the Sun, Earth, Jupiter, or other reaction fields, and if those fields are offset at a substantial angle relative to each other; effective impulse vectoring can be accomplished.

In Closing:

The Delta V imparted by a chemical rocket is limited by the attainable exhaust velocity of the rocket and total fuel mass available. In an Electro-magnetic Propulsion System capable of generating extreme field strength, the Delta V imparted will be limited only by the amount of available applied electrical power and the time span that power is made available.

In all cases, the minute field strengths of the reaction fields at range become usable when the propulsion system is capable of generating extremely strong fields or, in the case of dynamic braking, the induction circuit is capable of maintaining extremely high acceptance when dissipating high power.

The use of Electro-magnetic Propulsion may negate the requirement of waiting for opportune alignment of Jupiter and Saturn for use in Gravity assist maneuvers. The launch windows now continuously open by the ability to use Solar Field in repulsion to give the space craft the kick up that would otherwise require a gravity assist trajectory or maneuver.

A most important ramification of Electro-magnetic Propulsion and Electro-dynamic Braking in Space Applications may be the fundamental change in the logistics of asteroid deflection. This technology will negate the need to carry chemical fuel mass to the asteroid for the purpose of supplying impulse. It will allow mankind to use the orbital energy of the asteroid itself as the prime source of energy for deflection through an integration of Electro-dynamic braking, vectored electro-magnetic impulse, and to power Newtonian Propulsion Systems that use scavenged mass from the asteroid and accelerate it using propulsion coils. Perhaps, it will cause a re-evaluation of the decision to use nuclear explosive deflection and fractionation as the preferred approach to this impending challenge.

Hi Gavilan.

I don't have the time at present to respond to your whole extended article, but one thing immediately popped up as a problem. You wrote:

"In a low inclination orbit, generating a magnetic field in repulsion with earth field will begin to impart impulse along the orbital radius, increasing the semi-major axis, thus directly increasing the gravitational potential component of the total orbital energy (Specific Mechanical Energy)."

Adding an impulse in the radial direction is extremely inefficient when compared to adding that same impulse along the orbital direction. The reason is that the higher v, the more effect a specific Δv has, if in the right direction. For tangential, the new KE=½m(v+Δv)² = ½m(v² +2vΔv + Δv²). If that same Δv is applied in the radial direction, the new KE=½m(v²+Δv²), which is vastly less for the same Δv, if v is large. That's why escape impulses are normally imparted at periapsis and in the direction of movement where the velocity is highest.

If magnetic field propulsion is feasible (which I doubt somewhat), it will be far better to impart the impulse along the orbital path, rather than radially.

Jorrie

Jorrie,

Thank you for your reply.

You stated "Adding an impulse in the radial direction is extremely inefficient when compared to adding that same impulse along the orbital direction. The reason is that the higher v, the more effect a specific Δv has, if in the right direction. For tangential, the new KE=½m(v+Δv)² = ½m(v² +2vΔv + Δv²). If that same Δv is applied in the radial direction, the new KE=½m(v²+Δv²), which is vastly less for the same Δv, if v is large. That's why escape impulses are normally imparted at periapsis and in the direction of movement where the velocity is highest."

My reply:

The impulse being imparted at periapsis alters the semi-major axis by altering the radius of apoapsis. To reduce the eccentricity of the transfer orbit, impulse is then input at apoapis.

Instead of considering only the kinetic component of the total orbital energy let us consider both components.

First, it is important to agree that the total orbital energy is the sum of the kinetic and gravitational potential. Also, that any change in orbital velocity translates to a change in gravitational potential. I think on this we can agree.

Also, electromagnetic propulsion is already and applied technology in satellite attitude control.

In electromagnetic propulsion, when stepping up the orbit the purpose of imparting impulse along r is not to alter the kinetic component. It is to alter the gravitational potential component directly without having it translated through the kinetic component.

In the case of dynamic braking, as in conventional propulsion, the impulse is naturally imparted along the velocity vector translating to a change in gravitational potential.

The conventionalist's arguments are based on the Newtonian Laws of Conservation of Momentum. That there must be some type of mass momentum exchange before impulse can occur. It is after all, how impulse is defined.

I ask you to consider this simple scenario and question.

If a ferromagnetic marble is placed near an uncharged electromagnet and the circuit of the electromagnet is then powered up, the marble will accelerate towards the magnet. There will be an increase in the momentum of the marble.

Where is the mass momentum exchange?

Your time and expertise is greatly appreciated,

Sincerely;

Gavilan

Hi Gavilan.

"First, it is important to agree that the total orbital energy is the sum of the kinetic and gravitational potential. Also, that any change in orbital velocity translates to a change in gravitational potential. I think on this we can agree."

I agree, but my point is that the most effective way by far is to add trust to the total energy is along the orbital path and not radially. This raises the apoapsis of the orbit far more than by thrusting radially. Even solar sails, where the solar wind pressure is radial, are tilted so that the major component of thrust is along the orbital path, due to the vastly improved energy increase. I can do you the sums if you do not believe me…

"In electromagnetic propulsion, when stepping up the orbit the purpose of imparting impulse along r is not to alter the kinetic component. It is to alter the gravitational potential component directly without having it translated through the kinetic component."

Can be done, but it's silly – why not capitalize by directing the electromagnetic thrust in the direction of travel. As said above, you get much more for the same input.

"I ask you to consider this simple scenario and question. If a ferromagnetic marble is placed near an uncharged electromagnet and the circuit of the electromagnet is then powered up, the marble will accelerate towards the magnet. There will be an increase in the momentum of the marble. Where is the mass momentum exchange?"

If that magnet is in free space, there will be an equal and opposite change in the momenta of the marble and the magnet, while the total momentum of the system will remain unchanged. If the electricity source is external to the magnet-marble system, then the total energy of the system will increase. If the energy source is part of the magnet-marble system, then total energy will remain unchanged.

Obviously, if the marble is much less massive than the magnet, the marble will pick up a lot more speed than the magnet. But you can't avoid the Newtonian reaction momentum – the magnet will recoil if you shoot your marble away electro-magnetically. Likewise, if you can make use of a planet or star's magnetic field, the plant or star will recoil, but due to the large mass, not noticeable. There the planet is your 'magnet' and the spacecraft your 'marble'.

Jorrie

Hey, Jorrie!

One thing for beginners (as if I'm not one) to keep in mind is that where the energy of an interaction is stored and released is sometimes missed.

For example, you cause a splash in a swimming pool that hits the opposite side of the pool and is reflected back to you. To some, it might seem valid to think that the wall of the pool absorbed the energy, then returns it to the water. However, what really happens is the water rises up the side of the pool and is stored in the lift of the water, and is returned back as the water falls through the gravitational field in which it was suspended. A small point.

Jorrie;

My goal is to learn, and your expertise is greatly appreciated.

In your post you wrote - "I agree, but my point is that the most effective way by far is to add thrust to the total energy is along the orbital path and not radially. This raises the apoapsis of the orbit far more than by thrusting radially. Even solar sails, where the solar wind pressure is radial, are tilted so that the major component of thrust is along the orbital path, due to the vastly improved energy increase. I can do you the sums if you do not believe me…"

If you were going to step up a circular orbit to a circular orbit of greater semi-major axis the conventional inputs will be first at periapsis to increase apoapsis, increasing the orbital energy but also increasing the orbital eccentricity. An input would then be made at apoasis to bring the orbit back to circular.

It is not a matter of "believing you", what I lack is understanding, not trust. I trust your expertise but blind trust is still blind, it doesn't enhance my understanding. I also understand that it is not your responsibility to assist me in my learning goals; however, it is greatly appreciated.

Lets ignore eccentricity for a moment and consider only the specific mechanical energy. I understand the relationship of velocity to energy. I am trying to wrap my mind around the concept that in order to change the specific mechanical energy of the orbiting body that the most efficient way is to impart a change in the kinetic component instead of the gravitational component directly. A small incremental change in kinetic energy will translate to a change in gravitational potential in the relationship of delta V = sqrt(2g (delta r)). I know this is only an approximation because g varies inversely as the square of r where r could be the semi-major axis of an elliptical orbit.

The next thing you stated- "Can be done, but it's silly – why not capitalize by directing the electromagnetic thrust in the direction of travel. As said above, you get much more for the same input."

Again it is important to differentiate between the Lenz braking force in dynamic braking (which would translate along the velocity vector) to Field Reaction Propulsion where the force along the approximate r vector. I believe that there will only be two possible vectors in Field Reaction Propulsion when in action with a single planetary or solar field; both along the r vector, one being in attraction and the other in repulsion.

Perhaps increasing the specific mechanical energy of the orbiting body can be done just as efficiently by imparting a change in the gravitational component as the kinetic component. The change in the kinetic component will translate to a change in the gravitational component anyway.

Again I understand that the energy increases as the square of the velocity but energy is energy, if I contribute to the specific mechanical energy directly by increasing the semi-major axis or indirectly by increasing the kinetic component which will THEN translate to a change in semi-major axis; what difference does it make?

You go on to state - "If the electricity source is external to the magnet-marble system, then the total energy of the system will increase. If the energy source is part of the magnet-marble system, then total energy will remain unchanged."

Yes, in nuclear electric field reaction propulsion the law of conservation of energy will indeed apply, relatively.

Gavilan

Here is a little tid bit. Ignoring relativity at speeds much less than the speed of light. It would take about 39 gigawatts of continuous power to accelerate 1000 kg of mass from 0 to 1/4 the speed of light in one year. In perspective - 1/2 of a megawatt would accelerate the same mass to voyager speed in about 3 days.

Hi again Gavilan. You wrote:

"Perhaps increasing the specific mechanical energy of the orbiting body can be done just as efficiently by imparting a change in the gravitational component as the kinetic component. The change in the kinetic component will translate to a change in the gravitational component anyway."

Let's do some practical sums for an orbiting vehicle at 300 km altitude, with circular orbital velocity Vo = √(GM/r) ~ 7.6 km/s. Now suppose we want to boost this vehicle to escape velocity, Ve = √(2GM/r) ~ 10.8 km/s. In the tangential direction, we already have 7.61 km/s, so we only need 3.2 km/s deltaV. However in the radial direction we need to have √(deltaV² + 7.6²) ~ 10.8 km/s, requiring deltaV ~ 7.6 km/s. This is more than double the deltaV required for transverse boost or more than four times the delta-energy required.

It seems that "energy is energy" does not hold if you apply the energy differently. Think of what would happen if you apply the deltaV in the direction opposing the orbital movement. You have spent the same amount of energy and fuel, but you have less total energy than you started with. Whichever way you look at it, the direction matters…

"The change in the kinetic component will translate to a change in the gravitational component anyway."

The simplest is to again look at the above escape velocity case. Applying 3.2 km/s in the direction of the orbit achieves escape velocity, meaning the apoapsis essentially reaches infinity. Apply the same 3.2 km/s in the radial direction and escape velocity is not reached, resulting in a closed orbit. So the statement you made cannot be correct.

Jorrie

Thanks for the great reply Jorrie:

Please be patient with me.

You stated in your post - "Let's do some practical sums for an orbiting vehicle at 300 km altitude, with circular orbital velocity Vo = √(GM/r) ~ 7.6 km/s. Now suppose we want to boost this vehicle to escape velocity, Ve = √(2GM/r) ~ 10.8 km/s. In the tangential direction, we already have 7.61 km/s, so we only need 3.2 km/s deltaV. However in the radial direction we need to have √(deltaV² + 7.6²) ~ 10.8 km/s, requiring deltaV ~ 7.6 km/s. This is more than double the deltaV required for transverse boost or more than four times the delta-energy required."

My reply: A very good argument, but I am understand that escape speed varies inversely with r. Intuition tells me that if I continue to increase the gravitational component the mechanical energy will exceed that needed for escape speed. Using the term "speed" because escape speed is a scalar quantity.

Further you stated:" It seems that "energy is energy" does not hold if you apply the energy differently. Think of what would happen if you apply the delta V in the direction opposing the orbital movement. You have spent the same amount of energy and fuel, but you have less total energy than you started with. Whichever way you look at it, the direction matters…"

My reply: The Force vector does indeed matter. In the above case I believe the change in the kinetic component will translate to a smaller gravitational component. (Reduced semi-major axis.)

Jorrie finished; "The simplest is to again look at the above escape velocity case. Applying 3.2 km/s in the direction of the orbit achieves escape velocity, meaning the apoapsis essentially reaches infinity. Apply the same 3.2 km/s in the radial direction and escape velocity is not reached, resulting in a closed orbit. So the statement you made cannot be correct."

My reply: We want more than escape speed; we want Excess Hyperbolic Speed. Again, the proposed method would boost the total energy of the satellite by increasing the gravitational component without significant effect on the kinetic component.

Intuition tells me, that when beginning with a stable circular orbit, escape speed would be reached as soon as the gravitational component begins to increase; providing the kinetic component remains constant. The Excess Hyperbolic Speed should approximate the square root of (2PT)/m where P = applied power and T= time in application and m= mass of the object.

"Note: when the flight path angle is positive there would also be a slight increase in the kinetic component as well."

The increase in the specfic mechanical energy would approximate (Power X Time)/mass.

Comparing the energy imparted by 6,000 kg of mass reaction fuel with an exhaust velocity of 6000m/s to a 100kw RTG operating over a 30 day period and the advantages of such methods of propulsion become clearly evident.

Again, it appears escape speed can be attained by increasing the gravitational component without increasing the kinetic component.

Gavilan

Jorrie,

As I am sure you picked up on immediately; I erred here. "escape speed would be reached as soon as the gravitational component begins to increase; providing the kinetic component remains constant. The Excess Hyperbolic Speed should approximate the square root of (2PT)/m where P = applied power and T= time in application and m= mass of the object."

Also, I forgot to thank Jorrie for introducing the gravitational parameter. u=GM

Since escape speed varies inversely as r, and the kinetic component of total energy remains constant by inputting energy along r, perhaps the escape speed would be reached when the change in gravitational potential equals the energy needed to accelerate the satellite to escape speed. Vescape - Vorbital = Delta V. Change in a (semi-major axis) required to reach escape from a stable orbit with a constant kinetic component would approximate u/delta V squared?

The arguments being made here:

That escape speed varies inversely as r.

That energy input along the r vector would increase the semi-major axis if the kinetic component remained unchanged.

That from a stable orbit, with the kinetic component remaining constant, a continuous impulse along the r vector would eventually impart enough energy to exceed that needed for escape.

Gavilan

Hi again Gavilan; you wrote: "... escape speed varies inversely as r."

Don't forget that it's actually varying with the inverse square root of r, i.e. Ve=√(2GM/r).

Jorrie

Hi again Gavilan, you wrote:

"Intuition tells me, that when beginning with a stable circular orbit, escape speed would be reached as soon as the gravitational component begins to increase; providing the kinetic component remains constant. "

I'm afraid your intuition is 'dropping' you seriously here. Orbital mechanics is quite counter-intuitive, to say the least. I have done approximate simulations for a small continuous force being applied firstly radially and then tangentially to a craft in circular obit around Earth. The results are staggering, to say the least.

I applied a small constant force that caused an acceleration of 0.01 m/s^2 to the craft in free space. When applied radially for 5 full orbits (taking 27,560 seconds), the 300 km altitude orbit was raised by just over 3 meters, with a total orbital energy gain (kinetic + potential) of about 14 Joule per kg of orbital mass. Because of the small altitude gain, the orbital velocity stayed roughly constant at 7612 m/s. It does however gradually drop as more altitude is gained.

I then restarted from the 300 km circular orbit and applied the same constant force, this time with the tangential orbital movement. After 27,560 seconds, the orbit was raised by over 500 meters, with a total orbital energy gain of over 2 Mega-Joule per kg of orbital mass. This is a factor 150 thousand times more than the gain for radial application of the force. The bottom line is, forget about applying a feeble force against gravity. Apply it with the velocity!

In the latter case (transverse thrust), the orbital velocity dropped by around 276 m/s, because of the higher altitude. The kinetic energy lost there was however compensated thousands of times over by the potential energy gain.

So, Gavilan, despite what your intuition suggests, the math suggests you start working on a way to turn your magnetic propulsion vector through 90 degrees. You may eventually attain escape speed by radial thrusting, but what a waste of energy!

Jorrie

I wrote: "I then restarted from the 300 km circular orbit and applied the same constant force, this time with the tangential orbital movement. After 27,560 seconds, the orbit was raised by over 500 meters, with a total orbital energy gain of over 2 Mega-Joule per kg of orbital mass."

There's a serious typo in there: it must read 'over 500 km', not 500 meters!

Yes, that's correct: that 'feeble' but 'long-playing' thrust yielding just .001g of acceleration, raises the orbital height from 300 km to 800 km in about 7.6 hours (about 4.7 orbits). Amazing!

If all this sounds too good to be true, consider this: In free space, an acceleration of 0.01 m/s^2 for 27,560 seconds will give a ΔV of 275.6 m/s. Now let the craft have a coordinate velocity of 7,612,000 m/s in free space and calculate the kinetic energy gain if the two velocities are added. It is about 4.3 MJ/kg.

Compare this with the potential energy gain for the 500 km increase in orbital height, which is about 4.2 MJ/kg. Not all of this energy goes into total orbital energy, of course. Due to the lower orbital speed at 800 km altitude, the total increase in orbital energy is only 2 MJ/kg.

Jorrie

Jorrie;

"Now let the craft have a coordinate velocity of 7,612,000 m/s in free space and calculate the kinetic energy gain if the two velocities are added. It is about 4.3 MJ/kg."

My reply: Do you sum the two velocities or do you calculate the difference in the Initial KE and the Final KE?

If you are using Newtonian Mass Reaction Propulsion equate that to fuel mass. How much fuel mass did it require? Plug it into the basic rocket equation. Go ahead and use the high values for ISP found for ion propulsion.

Hmmmm.

Now vector that force radially and instead of using Newtonian Mass Reaction Propulsion and calculating the energy change as a function of fuel mass and exhaust velocity calculate it as a function of power and time. Now equate that time and power to gravitational potential. AND, if you are using an RTG as your prime energy source, how much fuel mass have you used? Relatively speaking that is.

Now what do the numbers look like?

I'm a simple fella that can only understand things at the simplest of levels.

The higher the initial velocity the much higher the required energy to impart the same value for delta V. Becoming imparted E= ABS (KEi + KEf). Example it requires much much more energy to impart a 2 meter/sec change in velocity with a constant mass at an initial velocity of 10 m/s that at an initial velocity of 100 m/s. About 100 times as much, that translates to considerable fuel mass. Even as the mass of the rocket decreases as it expends mass it requires proportionately more fuel mass for each incremental increase in velocity. Why? because the energy is a square relationship with velocity and only a directly as mass.

It is not possible to impart constant acceleration at constant power. Power = Force * Velocity. At constant power, as the velocity increases the force decreases and therefor the acceleration.

Now lets say that we simply can't come to an agreement on the efficiency, how about fuel mass fractions. My RTG powered field reaction propulsion against the BEST ion propulsion system?

You are a patient and kind man Jorrie.

Thank You,

Gavilan

Hi Gavilan,

the idea is good but the magnetic field strength is much too low or the necessary current and its associated energy losses are much too big.

The earths magnetic field is around 1 Gauss or 10^-4Tesla at the surface, declining with altitude - I don't know how fast.

If a flux density of 1T is crossed (at right angle) by a current of 1A then a force of 1N is generated. (Any loudspeaker or DC-Motor is using this.)

The force is at right angle to the flux and to the current.

If you think about a copper coil - made of 1mm square wire, or roughly 1.2mm diameter including some insulation - made of a length of 10km to generate this 1N? This will be 10l or 80kg of copper and have a resistance of 200Ohm and need a voltage of 200V to push the required 1A. (Aluminum would be a better choice)!

How long do you have to wait for a considerable acceleration or velocity change by this small force? and may be much smaller magnetic field? and a very big mass of an asteroid?

And the energy that is needed to bring this into a low altitude orbit.

Interesting new developments may result from the VAZIMIR experiments, a 3-stage ion thruster that can be adapted to different needs (high thrust to high exit velocity).

You are right that chemical propulsion is somewhat outdated but it is really difficult to do better.

RHABE

Thanks for the great reply RHABE!

RHABE stated that "the magnetic field strength is much too low or the necessary current and its associated energy losses are much too big."

First related to propulsion:

First "too low" is a relative statement. As stated in the essay, even the smallest of fields can be used as an action field if the field generated by the propulsion system is strong enough.

Related to Dynamic Braking. As stated in the essay, the three components of induction are excitation field, inductance, and Rate of Change. All the components are there. The laws of physics are universal.

Although argument can be made that induction circuits capable of maintaining high acceptance while dissipating high power is quite problematical, but there are solutions.

Also, remember the fundamental difference between electromagnetic field reaction propulsion and dynamic braking.

RHABE further states "If you think about a copper coil - made of 1mm square wire, or roughly 1.2mm diameter including some insulation - made of a length of 10km to generate this 1N? This will be 10l or 80kg of copper and have a resistance of 200Ohm and need a voltage of 200V to push the required 1A. (Aluminum would be a better choice)!"

Excellent point. Now lets change some circuit values. Lets feed ten turns of a cryogenically cooled super conductor from the highest regulated voltage that can be supplied by four 100KW RTGs. Providing the power source can maintain the required power, what would the estimated current be? Since the ampere is defined as magnetic force independent of area, what is the magnetic field strength?

Ion propulsion is just another Newtonian Propulsion System where the exhaust velocity of the action mass is very high. Since the efficiency of the propellant increases as the square of the exhaust velocity, yes, Vasimer has a very high ISP. But it is still a mass reaction scheme.

Field reaction propulsion is the next step in space propulsion. Its evolution is going to require overcoming a tremendous amount of engineering inertia. But, it is going to come, or the species won't be going anywhere very fast.

Gavilan

Our planet is like a small fragile spaceship; where there is no other refuge for its passengers. We can dream of colonizing the moon and planets, but given the limits and demands of human physiology; there remains but one Gaia, one home, one chance.

How about power requirments.

10 CLS
20 CLEAR
25 PRINT" The Relationship between Delta Velocity, mass, power, and time. by Mark J.Carter"
30 PRINT"Choose an option."
40 PRINT" 1. Delta Velocity as a function of initial velocity, power, time, and mass."
50 PRINT" 2. Time to new velocity as a function of desired velocity, power, and mass."
60 PRINT" 3. Power as a function of desired velocity, time, and mass."
70 PRINT" 4. To end."
80 INPUT A
90 IF A=1 THEN 190
100 IF A=2 THEN 380
110 IF A=3 THEN 480
120 IF A=4 THEN END
130 CLS
140 PRINT"You have to enter 1, 2, 3, or 4"
150 FOR PAUSE=1 TO 5000
160 NEXT PAUSE
170 CLS
180 GOTO 30
190 REM Delta velocity as a function of power and time loop.
210 GOSUB 580: REM Initial Velocity Input sub-routine.
220 GOSUB 610: REM Mass Input sub-routine.
240 GOSUB 620: REM Power Input sub-routine.
260 GOSUB 630: REM Time Input sub-routine.
280 DELTAE= POWER*TIME
290 INITIALE=.5*MASS*IV^2
300 NEWE= ABS (INITIALE+DELTAE)
310 VELOCITY= SQR ((NEWE)/(.5*MASS))
330 PRINT:PRINT POWER;" watts of power acting for ";TIME;" seconds will accelerate ";MASS; " kilograms from"; IV; "meters per second";" to "; VELOCITY; "mps."
350 PRINT "Hit any key to return to menu."
360 DUMMY$= INPUT$(1)
370 RUN
380 REM Time to New Velocity
382 GOSUB 580 : REM Initial Velocity Input Sub-routine.
383 GOSUB 590 : REM Final Velocity Input Sub-routine.
390 GOSUB 610: REM Mass Input sub-routine.
410 GOSUB 620: REM Power Input sub-routine.
450 DELTAE=ABS((.5*MASS*IV^2)-(.5*MASS*FV^2)): REM Change in Energy
452 TIME= DELTAE/POWER
460 PRINT;" It takes ";TIME; " seconds to accelerate "; MASS;" kilograms from ";IV; " meters/sec"; " to "; FV; " using "; POWER; " Watts."
470 GOTO 350
480 REM Power as velocity, time, mass.
482 GOSUB 580 : REM Initial Velocity Sub-routine
483 GOSUB 590 : REM Final Velocity Sub-routine.
490 GOSUB 610: REM Mass Input Sub-routine.
530 GOSUB 630: REM Time Input Sub-routine.
542 DELTAE= ABS((.5*MASS*IV^2)-(.5*MASS*FV^2)): REM Change in Energy
543 PRINT DELTAE; " Change in energy"
550 POWER= DELTAE/TIME
560 PRINT:PRINT:PRINT "It takes "; POWER;" watts to accelerate "; MASS;" kilograms from ";IV; " meters/sec to ";FV; " mps in " TIME; " seconds"
570 GOTO 350
580 PRINT:PRINT " Enter Initial Velocity in meters per second": INPUT IV
581 RETURN
590 PRINT:PRINT " Enter the Final Velocity in meters per second": INPUT FV
600 RETURN
610 PRINT:PRINT " Enter Mass in Kilograms": INPUT MASS
611 RETURN
620 PRINT:PRINT " Enter the power in watts": INPUT POWER
621 RETURN
630 PRINT:PRINT "Enter the time in seconds": INPUT TIME
631 RETURN


Hi Gavilan,

you are right with the superconduction possibility but beware of the current density limits of superconductors.

High temperature superconductors would not need any cooling in space, but current limiting and weight will be a problem.

A big problem will be the energy in the coil that has to be stored in a capacitor or wasted to heat at current reversal. This can be big as inductive energy is Eind=LxI²/2

But with simple radiation cooling it is possible to go down with temperature to 2 to 4 K.

This will lower the resistivity of copper dramatically. At room temperature the TC of resistivity is as in many pure metals near 0.4%/K. This is giving a factor near 10 that the resistivity should be lower. This value is realistic but actual behaviour is very much dependent on impurities and thermomechanical treatment.

Do you know the magnetic field strength around earth and sun and interstellar?

I agree to your arguments that in future there may be a propulsion system for deep space missions.

But at the moment we have to stay chemical and only first steps towards ion thrusters.

Magnetism:

The magnetic flux density - to be measured in Tesla or T = Vs/m² (or in Gauss in earlyer systems)- can be thought as the number of magnetic field lines that penetrate 1 square meter. Symbol is B.

The magnetic field strength - to be measured in A/m - can be thought as the driving force per length that is generating the field lines and drives these across the magnetic resistance in the loop. Symbol is H.

If you think the earth as a magnet (regardless if permanent or electromagnet) the field lines exit the surface in the northern hemisphere - most concentrazed around the magnetic north pole, the field lines curve through the near earth space and return to the southern hemisphere.

The total flux in such a sytem is constant, so at diverging field lines further from earths surface the flux density goes down.

This is the first magnetic law: constant flux in the system.

The magnetic potential is the fieldstrength times the length to be integrated along any field line. The magnetic potential that is generated inside the magnet is used to magnetise the space outside the magnet. This is totally equivalent to an electric voltage generator and a distributed attached conductor - except that the magnetic potential is measured in amperes. As the voltage along one current line in an electric generator and conductor system (both distributed) is zero if integrating one full loop of the line the same is true for the magnetic potential in a magnetic circuit.

This is the second magnetic law: the ring integral along any field line is zero.

The third lmagnetic law is the material law that combines Field strength H and flux density B: B = µ₀ x µ x H, where µ₀ is a universal constant (8.8 x 10^-6Vs/Am) and µ is the relative permability of the material. µ is a constant very near 1 for our ordinary "nonmagnetic" materials: air, wood, plastics, aluminum, copper, µ is a function of H for the ferromagnetic materials: iron, nickel, cobalt and alloys of these and some other metals and for permanent magnets.

This function is the magnetic hysteresis curve. If B plotted at the vertical axis and H at the horizontal then there are two horizontal parts of the hysteresis at large +-H values the Bsat or saturation flux densities. (At values between 0.7 and 2.3 Tesla.)

The curve crosses the horizontal line at the +- Hc points, the coercive magnetic field strength with a slope of µ₀.

Soft magnetic materials have low Hc values (some A/m) hard magnetic materials have high Hc values up to above 1 MA/m.

With these three equations (Faradays laws of electromagnetism) you can calculate either very simplified by hand or with much better accuracy by FEM MagnetoCad the magnetic Flux density anywhere in the system.

If you try to calculate with a simple first approach: 1 permanent magnet ( or this substituded to a current loop) 1 soft magnetic structure and one airgap to be magnetised you will find the first trial difficult but subsequent refinement and other systems easy.

RHABE

RAHBE:

Your posts are great! It forces considerable processing out of my old and rudimentary bio-cpu. (They encourage be to think.)

Is there anybody out there that could help me calculate the force between two parallel coils. I have seen some stuff pole to pole on the net but I can't find the calculations for parallel bar magnets. Is the force going to decrease as the square of the distance like a point charge?

My wife drove took her new 07 Mazda MX-5 into the piney woods of East Tex at about 65 mph Friday night. She was trying to dodge a retread from a truck tire. Pretty irresponsible of the companies and truckers who use those tires. But hey, its all about the money, they could care less about the few folks who get killed or injured.

Thanks to some great automobile engineering she only broke her tibia near the knee. Thank you Mazda.

Anyway, my study time just shortened up a big bit for the next 14 to 16 weeks.

Gavilan

RHABE:

This stuff confuses me terribly. I think I am getting too old.

I have always thought that the energy stored in an inductor was stored in the form of magnetic potential. That if this field were to collapse at a rate of 1 ampere per second through a circuit of 1 henry then an EMF of 1 volt would be induced.

That if I introduced capacitance into this un-rectified circuit then the circuit would begin to oscillate at a frequency that corresponds to Square Root of the reciprocal of l X C where l is the inductance in Henry's and C is the capacitance in farads. That this circuit, if at very low resistance would continue to oscillate until the resistive losses of the circuit dissipated the energy. But this is not going to be a factor since the circuits in both braking and propulsion will be DC.

It would be easier for me to wrap my mind around this if I fully understood the "Weber" in relation to the "Tesla". I think the Weber is best described as the strength of the field and the Tesla as the flux or Rate of Change of the field per square meter. What variables would I have to consider in calculating the power dissipated through a flat copper plate of one square meter being exposed to a flux of one Tesla? Perhaps the resistivity (the reciprocal of conductivity).

We shall relate this to the topic of Comets and asteroids hitting the earth as a potential deflection strategy. Ignoring field reaction propulsion for now and focusing on dynamic braking.

We could begin by calculating the Lentz braking force of a large coil of defined inductance (or the asteroid body itself if properly circuited) , moving at 32,000 meters per second at near the maximum induction angle through a field of X Weber's where the induced circuit power is dissipated as RF and IR energy. Somehow I think the Tesla unit will factor as a function of the sun field strength at r, the coil area, and velocity. I think once that is known then the the induced voltage can be calculated by defining the circuit inductance according to one of Faraday's Laws. Once the induced potential is defined we should be able to calculate power dissipation as a function of circuit resistance. Perhaps we can agree that since there is no oxygen available we will be able to heat our resistors to near the melting point and that the IR energy dissipated will be proportional to the 4th power of the operating temperature. (Stefan's Law).

Once that is accomplished we can with confidence calculate the rate change in orbital energy of the object we are attempting to brake, confident also that the vector of the applied force will be opposite the orbital velocity vector. (How confident are the militarists in the ability to calculate the sum force vector in the nuclear explosive deflection schemes congress appears to have bought into?)

Once that is determined, we can optimize the technology by incorporating field reaction propulsion, powered by the linear induction process, to further enhance our ability to control the orbital intersect time of Aten objects with our little space ship called earth. Or, for the case of one of the most threatening Aten objects, let Venus take the hit for us.

But before we can do ANY of this we must first and foremost overcome the engineering inertia that prevents us from taking a few more steps from the cave. An inertia that protects the specialization and trough of the status quo.

Gavilan

Hi Gavilan,

Weber is Tesla times squaremeter of area perpendicular to the flux direction.

if there are long times (compared to the L/R time-constant) you are right that acceleration and braking will be mostly DC.

But as you will have to switch large currents into large inductances the current changes may be quite difficult giving high Uind as you stated.

A flux density of 1 Tesla through an area of 1 square meter is a flux of 1 Weber.

This will not affect at all the conductive plate.

As soon as you have a rate of change in the flux you will have an induced voltage as you stated U_ind=-L*dI/dt

This voltage is driving a (circular) current in a closed loop of electrically conducting material or plate conductor as your suggested copper plate.

This current times the voltage is the resistive loss that is heating the loop.

I do not see how you want to impart force on the asteroid by this action as the magnetic field in the environment is supposed to be more or less constant over long distances, or am I wrong with this?

So I think the only interesting way may be braking by a current loop that is fed into the loop coil with a +- switchable DC generator that has to have an adjustable voltage to overcome the voltage drop because U1=(current times resistance) plus U2 the induced voltage as discussed above. And it has to have a suitable current capacity to drive the current. If superconducting additional circuitry would be necessary as to start a current in a superconducting loop is not the same as to switch on a resistive plus inductive conductor.

So first of all we need the magnetic field and its distance dependence of earth and sun.

Then we take a coil and a voltage generator, orient the coil with its axis parallel to the magnetic field lines, generate current in the coil and get the force .

At suitable times we have to switch the current direction and may be consider the stored energy if useful to store or dangerous to the switching process.

I did blow the fuses in my house with a simple 1KVA transformer and after being able to switch it on I destroyed the switch at switching off because of high induced voltage and enough stored energy to melt the contacts in the switch.

It is not a good idea to go up with temperature if you have a heated conductor as with temperature the resistance will go up and thus the current go down. Dissipated power can be rewritten as U²/R, so a low R is giving a high power. How to get rid of it may be difficult.

So please get some information on the magnetic fields existing and the function of distance from the earth or sun.

RHABE

RHABE:

Again, thank you for your very informative posts.

In your post you said "But as you will have to switch large currents into large inductances the current changes may be quite difficult giving high Uind as you stated."

In dynamic braking there MAY be no need for switching. I will explain in a moment. Also, the braking force is the Lentz force that develops as power is being induced in the braking circuits. The energy is dissipated through radiation of high temperature resistance.

Further you said "This voltage is driving a (circular) current in a closed loop of electrically conducting material or plate conductor as your suggested copper plate."

I muddied the water with the flat plate. I used it to draw a picture of a flat plate moving through a magnetic field with the power being dissipated only through the natural resistance (1/conductivity) of the material. I believe this may explain the "Pioneer Anomaly" but let us not go there right now. I've muddied the water enough.

Let us get back on topic.

Asteroid deflection using a combination of Field Reaction Propulsion and Orbital Dynamic Braking:

I ask to limit it for now to Orbital Dynamic Braking where the Sun field provides the excitation field, attached apparatus as the inductor (or the asteroid body itself if it is made of the right stuff and then circuited), and the tremendous orbital velocity giving the induction process the required "R.O.C." or rate of change.

Let us pick an object to impart a change in the orbital components. Let us make it Apophis MN4 2004. Why, because of its orbital plane it crosses earth orbital path on plane once every 324 days and sooner or later we either deal with it or take an impact of somewhere between 400 and 800 MT, not including the geologic input energy triggered by the impact. Not a planet killer, but the single most energetic natural event in recorded human history. It's also easy to get to without requiring an energy expensive orbital plane change to intersect, pace, and land on. (See how JAXA did it with another object with a much more problematical orbit with Hayabusa mission. http://www.isas.jaxa.jp/e/enterp/missions/hayabusa/index.shtml.)

The orbit of Apophis appears to cut the field lines of Solar Field at near the optimum angle for induction.

Its average orbital speed is about 30,000 m/s. That gives it plenty of velocity for induction providing we have high value for our inductance. Enough on our target body, let us return to the basics of induction.

You said; "It is not a good idea to go up with temperature if you have a heated conductor as with temperature the resistance will go up and thus the current go down. Dissipated power can be rewritten as U²/R, so a low R is giving a high power. How to get rid of it may be difficult."

Well, we have a couple of opportunities here. I think you are using the symbol U for voltage, which tells me the circuit power increases as the square of the voltage but decreases only in direct proportion to resistance.

It may be that we will not have to switch the dissipation circuit in and out of the induction circuit. If we can design in this way, we do not have to deal with inductive reactance because once the induction circuit branch is feeding the dissipation branch the value for the current will not be changing, so there will be no reactance.

The braking force is developed by the fact that the current flowing in the inductor will set up a magnetic field that opposes the magnetic field producing it. Look at Lentz's law and see if you can agree with that. What I believe will end up happening is that the braking force X velocity will approximate circuit power. That the braking force vector will be opposite the velocity vector. That the delta -V imparted will be in relationship to circuit power as ΔV=√(2pt/m) where p is dissipated power, t is the applied time, and m is the asteroid mass.

That power can be dissipated in frequencies from the Infra Red down to and including low frequency RF.

Let us look at radiative dissipation. You said that as the temperature of the dissipation resistors increases, the circuit resistance increases in direct proportion to the temperature; but I understand Stefan's law as stating that the rate of dissipation will be a function of the 4^th power of absolute temperature. It appears, in terms of dissipating power through radiative cooling that it is most advantageous to operate at the highest possible voltage. What does this mean in terms of the ability of the circuit to dissipate power?

Since we are dissipating power through radiation perhaps if we used the asteroid body as a heat sink we could benefit from its large surface area in radiative dissipation?

Also, how much power could we dissipate in a very broad bandwidth RF? How about if we used some of that power to melt, ionize, and accelerate mass from the asteroid body it self in a Newtonian Mass Reaction Process? How about feeding another inductor that pushes or pulls against Solar Field?

We can dissipate the power.

Now let us look at some design parameters for the induction coils(s). From your posts it appears that optimizing the area of our coil(s) will increase the total flux. Also, it is known that the more turns in our coil the higher the induced voltage. The asteroid orbital energy will act as a natural voltage regulator so that when we start to load the circuit the voltage across the leads of our coils will remain constant, at least at the power we could conceivably be dealing with.

Stopping the axial rotation of the asteroid doesn't seem to be that problematic when using coil field/Sun Field interaction. The system will naturally seek the magnetic equilibrium position.

We can derive acceleration from circuit power and magnetic force from acceleration if Sun Field is known.

Can you help us with a simple circuit.

Can you give us the formula for the induced voltage across a coil with a length of L, radius of r, number of turns as N, core permeability of e, moving through a field of B at a velocity of V at the maximum induction angle?

I refer to the last paragraph of my original essay on post number 36 – "A most important ramification of Electro-magnetic Field Reaction Propulsion and Electro-dynamic Braking in Space Applications may be the fundamental change in the logistics of asteroid deflection. This technology will negate the need to carry chemical fuel mass to the asteroid for the purpose of supplying impulse. It will allow mankind to use the orbital energy of the asteroid itself as the prime source of energy for deflection through an integration of Electro-dynamic braking, vectored electro-magnetic impulse, and to power Newtonian Propulsion Systems that use scavenged mass from the asteroid and accelerate it using propulsion coils. Perhaps, it will cause a re-evaluation of the decision to use nuclear explosive deflection and fractionation as the preferred approach to this impending challenge."

Gavilan

Our planet is like a small fragile spaceship; there is no other refuge for its passengers. We can dream of colonizing the moon and planets, but given the limits and demands of human physiology, there remains but one Gaia, one home, one chance

Hi Gavilan,

to give a good example how to calculate acceleration or deceleration I would need the data of the suns magnetic field: flux density or field strength at a known point (may be at the distance from the sun where earth is) and its dependence on distance.

And it would be necessary to have the orbit data (the two axis of the ellipse) and the mass of the asteroid.

Else the calculation is only Force = (B x I)*L

B x I is the vectorial cross product, I is the current in the coil (amps times turns), L is the length and B is the flux density of the magnetic field that is related to the field strength (in vacuum) by B=µ₀*H. So knowledge of the field strength would suffice also.

RHABE

Hi RHABE, you wrote: "And it would be necessary to have the orbit data (the two axis of the ellipse) and the mass of the asteroid."

Why not use Apophis, which (calculated from Wikipedia) gives the following values: mass ~ 2×10¹⁰ kg, aphelion = 1.64x10¹¹ m, perihelion = 1.12x10¹¹ m, speed at aphelion as 26.27 km/s and at perihelion 38.7 km/s, with average speed 30.73 km/s.

Jorrie

RHABE:

At Earth Radius

The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth. If space were a vacuum, then the Sun's 10^-4 tesla magnetic dipole field would reduce with the cube of the distance to about 10^-11 tesla. But satellite observations show that it is about 100 times greater at around 10^-9 tesla.

I also read an estimation of 1 Gauss for the Sun Field Value but it did not give the range.

Could you show me how to do the calculation?

Thank You

Gavilan

Hi Gavilan and Jorrie,

thank you for the data.

I did the following:

The impulse of this chunk of material is mass x velocity = m x v

The change of impulse is (if mass is constant) m x Δv = F x Δt

Delta-v is the change in velocity, F is the force acting for delta-t time increment.

m x Δv is better written as m x v x Δv/v

Δv/v I estimate to be 0.1% is enough for sufficient braking (or acceleration) to prevent a hit, the change in mean radius will be two times this relative velocity change so if the mean radius is 140 million kilometers then 1 promille will change this by 140thousand kilometer - more than enough, a factor of 10 less may be critical.

We want to brake or accelerate in the direction of the velocity (thank you Jorrie for making this clear), so we need a tangential force with a radial magnetic field, this can be done only with a current that is oriented vertical to the orbital plane.

So my idea in another post - to use a circular coil - is not working as the one side of current going down together with the other side of current going up is adding to a torque but not a force.

So what is necessary is a linear current path vertical to the orbital plane without current return - this is not possible, so we have to eliminate the force that is generated by the current return path (thought to be parallel to the acting part of the conducting rectangular loop with two long and two short sides.)

To eliminate the force from a current in a wire is requiring magnetic shielding, let us see later if this is possible with a soft iron shield.

The force F from a current I of length L vertical to a magnetic flux density B is F=BxIxL

If we put this into the above stated F x Δt =m x Δv and reaarange then we get:

I x Δt = (m x v)x(Δv/v)x1/(BxL)

the impulse is 600 x 10¹² kgm/s

the relative velocity change shall be 0.1%

the length of the current bar is set to 1000m

the magnetic flux density is assumed to be 10^-9T

so we need a current x time of 0.6x10¹⁸As

so we would need 10¹²A and 10⁶seconds for example, may be 10¹¹A and 10⁷s is ok too. 10⁶s is near 12 days. 10¹²amps seems to be out of reach.

The flux density is much too low. But as I have no knowledge of superconduction may be somebody else can comment on this.

Magnetic shielding: the magnetic fieldstrength H around a conductor with current I acting in a circular path of length C around the conductor is: H x C = I

The flux density B that is generated by the field strength H is in vacuum B = µ₀ x H as µ₀ is 1.2X10^_-6 the flux density is at a diameter of 32cm or a circumference of 1m and the above current of 10¹²A, field strength H=10¹²A/m (10⁶A/m is achievable with modern permanent magnets), flux density B is 1.2 x 10⁶T.

This is very far from any possibility.

The Sandia Lab z-machine can reach for a short time near 70 T.

As iron will magnetically saturate at 2 T we would have to extend the shield to 2000km thickness where the mean flux density is near 2 T.

So forget about this "possibility".

I cannot calculate today the other may be possible scheme of a radially pointing coil to generate a magnetic dipole field that would generate a force as any two magnets that are aligned either repulsive or attractive.

The third discussed possibility will not work at all: a conducting plate will see a constant magnetic field and thus not giving a decelerating force.

So think about brute force: nuclear or chemical explosives, chemical- or ion-thrusters.

Last remaining question: why can the magnetic field of the sun be amplified by any ion current?

RHABE

Gavilan replies: Jorrie had argued that the energy to cause a change in v was independent of initial velocity. I simply can't wrap my mind around that. If the impulse is along the velocity vector; the energy input required is (KE initial) – (KE final). If using a chemical propellant where the mass of the object is much greater than fuel mass then the equation simply becomes Δ E = .5 (Δ m)V^2_ex and

ΔV= (√2((Δe)/m.))

In the case where the fuel mass is not negligible relative to total system mass then it becomes ΔV_ke= V_ex ln(M_o/M₁) http://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

RHABE states: "Δv/v I estimate to be 0.1% is enough for sufficient braking (or acceleration) to prevent a hit, the change in mean radius will be two times this relative velocity change so if the mean radius is 140 million kilometers then 1 promille will change this by 140thousand kilometer - more than enough, a factor of 10 less may be critical."

Gavilan replies: ".1% is 30 m/s!! In the case of Apophis using a rocket exhaust velocity of 6000 m/s would require 9 million kg of fuel mass to impart a change in velocity of .25 m/s. That is ¼ of one meter per second."

RHABE states: "We want to brake or accelerate in the direction of the velocity (thank you Jorrie for making this clear), so we need a tangential force with a radial magnetic field, this can be done only with a current that is oriented vertical to the orbital plane."

Gavilan replies: "First off, you cannot impart a force along the velocity vector using generated field reaction. You can however, generate braking force acting opposite the velocity vector using Lentz braking. (http://en.wikipedia.org/wiki/Lenz's_law) Using Lentz inductive braking the impulse will be opposite the velocity vector. emf=BL(V cos ∂). ΔV can then be calculated as √(2Pt/m) where P is the dissipated power (V/z), t= process time, and m is object mass.

RHABE states:"So my idea in another post - to use a circular coil - is not working as the one side of current going down together with the other side of current going up is adding to a torque but not a force."

Gavilan replies: Why would you even consider a toroid ?

RHABE states: "So what is necessary is a linear current path vertical to the orbital plane without current return - this is not possible, so we have to eliminate the force that is generated by the current return path (thought to be parallel to the acting part of the conducting rectangular loop with two long and two short sides.)"

Gavilan replies: Get yourself 2 long bar magnets and empirically determine the relationship of force to angle. What is required in field reaction propulsion is that the action field be polarized either in attraction or repulsion to the reaction field as explained in the essay "Field Reaction Propulsion" - subpart – "A Simple Space Based Experiment." http://www.bestsyndication.com/?q=072407_solar-power-sailing-in-outer-space-extend-long-distance-travel.htm

Further; it appears that RHABE fails to understand the fundamental difference between Lenz braking and field reaction.

RHABE states: "To eliminate the force from a current in a wire is requiring magnetic shielding, let us see later if this is possible with a soft iron shield."

Gavilan replies – You are making very thick mud here.

RHABE states: "The force F from a current I of length L vertical to a magnetic flux density B is F=BxIxL

"If we put this into the above stated F x Δt =m x Δv and reaarange then we get:"

I x Δt = (m x v)x(Δv/v)x1/(BxL)"

the impulse is 600 x 10¹² kgm/s

the relative velocity change shall be 0.1%

the length of the current bar is set to 1000m

the magnetic flux density is assumed to be 10^-9T

so we need a current x time of 0.6x10¹⁸As

so we would need 10¹²A and 10⁶seconds for example, may be 10¹¹A and 10⁷s is ok too. 10⁶s is near 12 days. 10¹²amps seems to be out of reach.

Gavilan replies: Yes RHABE, imparting a change of 30 m/s in 12 days seems absolutely impossible. Perhaps if we reduced the delta V to a more realistic value of .25 m/s and used high power, high voltage RTGs acting through a time period of lets say, 5 years, perhaps the current densities become more manageable?

RHABE states: "The flux density is much too low. But as I have no knowledge of superconduction may be somebody else can comment on this.

Magnetic shielding: the magnetic field strength H around a conductor with current I acting in a circular path of length C around the conductor is: H x C = I

The flux density B that is generated by the field strength H is in vacuum B = µ₀ x H as µ₀ is 1.2X10_-6 the flux density is at a diameter of 32cm or a circumference of 1m and the above current of 10¹²A, field strength H=10¹²A/m (10⁶A/m is achievable with modern permanent magnets), flux density B is 1.2 x 10⁶T.

This is very far from any possibility."

Gavilan replies: It appears we are returning to the mud hole with toroids.

RHABE states: "The Sandia Lab z-machine can reach for a short time near 70 T.

As iron will magnetically saturate at 2 T we would have to extend the shield to 2000km thickness where the mean flux density is near 2 T.

So forget about this "possibility"."

Gavilan replies: It is indeed a good thing to crawl out of that mud hole.

RHABE states: "I cannot calculate today the other may be possible scheme of a radially pointing coil to generate a magnetic dipole field that would generate a force as any two magnets that are aligned either repulsive or attractive."

Gavilan replies: You wouldn't radially point it at anything. When was the last time you played with two bar magnets? Was the only time you were able to generate a force when you put the magnets pole to pole? I think not!

RHABE states: "The third discussed possibility will not work at all: a conducting plate will see a constant magnetic field and thus not giving a decelerating force. "

Gavilan replies; First, the flat plate was to introduce the idea of Lenz Braking being the solution to the Pioneer Anomaly. BUT, take a "flat plate", suspend it like a pendulum and allow it to swing between the poles of a horse shoe magnet. The braking is quite dramatic indeed wouldn't you agree?

RHABE states: "So think about brute force: nuclear or chemical explosives, chemical- or ion-thrusters."

Gavilan replies: And your brute force will be vectored in what direction? What will the net sum vector impulse be? I've done the math on chemical propellants. As I stated earlier, about 9 million KGs of fuel mass with an exhaust velocity of 6000 m/s for a delta v of ¼ of one meter per second. Although brute force may be the specialization and economic interest of the status quo, it in no way represents a calculable or confident deflection strategy.

RHABE states: "Last remaining question: why can the magnetic field of the sun be amplified by any ion current?"

Gavilan Replies: OK, let us hear it.

Hi Gavilan, you wrote: "Jorrie had argued that the energy to cause a change in v was independent of initial velocity. I simply can't wrap my mind around that."

Have you followed my "Free energy puzzle" thread? I think most respondents eventually agreed with my view.

Jorrie

Hi Gavilan,

nature is sometimes complicated but we shall try to understand and after some thinking the difficulties may vanish.

1. Your problems with energy arises because you are thinking in energy terms instead of impulse. Thinking in impulse related equations: mass times velocity is the impulse, if differentiated at constant mass it yields (F=force, Δt=time increment, m=mass, Δv=change in velocity): F x Δt = m x Δv

2. Lentz braking is not working in an environment of constant magnetic field. The induced voltage is U_ind=n x dΦ/dt, n is the number of turns in a coil, Φ is the magnetic flux or flux density times area of the coil. So to get a voltage you need changing flux or area. The flux is more or less constant unless you wait for a quarter turn in orbit - too long a time and too slow a change. There will not be an induced voltage (may be microvolts or millivolts) so there will not be braking. If you have a small magnet magnetising a part of a large area disc and move the disc or the magnet in the plane of the disc the situation is different: there is a large flux density (1T) and the region of the disc that is magnetised is changing so the induced voltage can drive current loops that in turn dissipate some heat that is drawn from the energy of the moving plate.

3. The problem of the 2 bar magnets is that you have one of only only nanotesla flux density. And you cannot push the other one above some (10 would be gigantic) tesla.

4. Do the big mud calculations with your proposed 0.25m/s and you will see that this is still far from realistic for any time coming.

5. Good thing that you calculated that chemical propulsion is also out of reach.

6. I am convinced that only nuclear explosion is a today existing possibility.

7. Long term acceleration with a nuclear power source will use ion thrusters , in near environments the mass may be transported with the spacecraft in far environments it will be necessary to collect some (enough is existifg out there).

RHABE

Me Gusta Jorrie! You wrote "I don't think the 'Pioneer Anomaly' is a factor - Apophis does not go far enough from the Sun."

Unless of course, it is related to the small induced power as Pioneer moves through the Sun's magnetic field at the near optimum induction angle. Although there may not have been a completed braking circuit, the minute dynamic braking power dissipated in the spacecraft mass itself may be the fundamental cause of the anomaly. If this is the case then it would be an even greater factor in extrapolating Apophis's position out 30 years.

Gavilan

Hi Gavilan,

a medium size thermonuclear warhead has 2 megatons TNT equivalent, a big one up to 50.

1kg TNT is roughly equivalent to the energy of 100g coal if burnt.

1kg coal is near 10,000kcalories.

1 kcal is 428mkp or 4.2KWs.

So 1kg coal equals 42MWs. (1Ws equals 1 Nm)

0.2 megatons of coal is equivalent to 8.4 x 10¹⁵ Ws

If you let fall down a hammer of 1kg from a height of 10m (or 10kg from 1m) this is equivalent to an energy of 100Ws and can easily crush 100g to 1kg hard rock.

So we can crush 8.4 x 10¹²kg with the 2 megaton warhead. If the asteroid is of density 3 or near this value (most stones are) this will be equivalent to 2.8 x 10⁹ cubic meters. Or a cube of 3000 m sidelength.

No known asteroid that will be near the earth has this size.

Any arguments that in this calculation the total energy has to be transferred can be waived by the fact that there is only the necessity to break the asteroid up into minimum two pieces.

The "only" problem that exists is to impart a considerable fraction of this energy to the incoming object.

The first possibility is to use the "penetrator" technology that is developed since some time to smash deeply buried bunkers but is said to be unreliable if hitting hard and solid rock. With this technology the nuclear warhead will penetrate some meter deep and then explode and impart a considerable impulse and braking into pieces the whole thing.

It is very unlikely that these pieces will pose any more a threat.

If the penetrator is not possible with solid stony or metallic asteroids there will be the necessity to bring along some considerable mass to explode the warhead between this mass and the asteroid. This too will smash the asteroid to pieces.

Third possiblity is to first have a small explosion to form a crater and then explode as deep as possible inside this crater the bigger device.

To be debated should be where to ignite the explosion: head on, on the rear or on the side?

RHABE

(I have to think about your question why a 50m object can destroy half of Europe, this will take some time.)

(I have to think about your question why a 50m object can destroy half of Europe, this will take some time.)

If Ii hit you with a baseball it may not hurt. But if Roger Clemens hits you with a 102 mph fastball it might kill you.

The estimated impact energy of Apophis has been downgraded from 800 MT to 400 MT. Compare that to the equivalencies of some major volcanic eruptions in recorded history.

It is quite likely impact events have been a factor in not only the geologic history of the planet, but the evolution of our species.

Gavilan

Hi Gavilan,

back to the energy of a 50m Asteroid:

for simplicity thought as a 50m cube of iron-nickel.

Volume is 125,000 cubic meter.

Weight is 10⁹ kg.

Velocity is estimated 32km/s (from 20 to 60 is possible, earth has a velocity around sun of near 30km/s, an elliptical orbit of an asteroid coming from outside the earths orbit will have more than 30.)

Energy is velocity squared times half the mass: E_kin = 0.5 x 10^₁₈Ws

As I calculated in a post above the energy release of a 2 megaton thermonuclear bomb to be 8.4 x 10¹⁵Ws, this is near 120megatons.

I have no idea how much of Europe will be destroyed by this directly and how much of the woods burnt but as 2 megatons is sufficient to destry a big city 30km diameter) the damage will be really big.

And may be the velocity was higher (60km/s ?) and likely the diameter was bigger? factor of? So in total the energy may have been well above 1 gigatons.

Impact angle was between 30 and 45 degrees coming from northwest, this is documented by the tectites, glass pebbles found in czech republic 300km distance from the crater, squeezed out by the first milliseconds of the impact..

RHABE

I agree that there are more calculable concerns for calamity when we consider volcanoes, landslides, polar ice caps, earthquakes etc.

It is the incalculable nature of asteroids that causes many to consider safety measures such as ICBMs. How many? What if one collides with a nearby moon, or our own moon and showers down etc, etc.

When you say easily reconfigured - let's assume you are right. The problem now is so why don't we have something already 'pointing' in the right direction instead of waiting for a scramble?

an aside: we should on this forum perhaps make note of meteorite vs. asteroid. Most agree that there is a difference.

All in all I agree with you completely - I feel there should be prudent consideration AND action given to the likelihood of all the above mentioned issues.

cr3

There is a greater chance that they will guide the thing in to some unsuspecting non-target that was long ago targeted and direct it to the bulls-eye. of course Hellaburnin and other companies will just happen to be doing some work situated nearby for ready response.

cr3

Sad, but all to true

An interesting article in the Scotsman today.

Interesting article but focusing on a moving target with the target possible rolling in multiple axis's, would present quite a challenge

True, maybe a job for the Playstation generation?

Who says that the playstation isn't already hooked up to the real thing.

And we are not only fending off asteroids but also battling wars, aliens, and conflicts in real life that the government does not want the public to find out.

Phoenix911

somewhere in an alternate universe there IS a little Italian man running through the sewers!

One of the things that have to be taken into consideration when determining what would happen if we were hit by a asteroid is what's it composition. There are both light and heavy types of asteroids.

Currently, I an holding a 5" X 4" X 4" piece of the El Campo Del Cielo meteorite in my hand, and it is insanely heavy for its size! I think we would rather be hit by a carbonaceous chrondrite than something that weighs in like this thing!

P.S. It's also highly magnetic!!! It took me forever to pry it off my 1000 lb lift Neodymium magnet!!!

The chances of the April 13th 2029 event becoming an Earth impact are rather small, and being recalculated regularly. Another possibility is impact with the Moon, with even smaller odds due to the face area of the Moon relative to the Earth. However, because of the Moon's lower mass, there is the possibility of a slight shift in the Moon's orbit following such a collision. Is anyone looking at the outlook following this possibility?

From what I can tell, we have no problem hitting an asteroid provided we have enough info about its orbit. The problems are time and energy. We have to launch the rocket in time to deflect or destroy the asteroid, and the weapon has to have enough energy to do the job.

Let's say we have the capability to hit an asteroid on short notice. Can we build a warhead strong enough to do the job? That seems to be the major sticking point.

Instead of explosion or propulsion, why not corrosion? What I am thinking of is some kind of chemical that will react with the elements in the asteroid and vaporize material in the asteroid, or break it up structurally . Then the question would be, can we deliver enough of the chemical and make sure it will either reduce the size of the asteroid or weaken it structurally so that it will burn up if it should enter the Earth's atmosphere?

I can't say for sure if this is possible. We are talking about chemical reactions taking place in the relative vacuum of space, and I don't think chemists are used to dealing with such processes. Most likely, we would have to have a warhead that could penetrate the surface of the asteroid to some depth before it releases the chemicals. Maybe the best approach would be a cluster of such chemical bombs.

In the relative vacuum of space? Woof!!!

Chemicals will either freeze instantly or vaporize before any reaction can take place. Also, penetrating an asteroid could take some doing. In number #58, I describe a piece of the El Campo Del Cielo meteorite. By just this small piece that you would be hard-put to penetrate an asteroid of this type.

Jorrie is right. The best strategy is to learn as much as we can about the orbits of Earth-crossing asteroids, compute into the future as far as possible, and send something that can give the rock a little nudge, which over time will be a major miss.

It's either that or 500 chimpanzees in space suit wielding jackhammers!!! That could work, too!

3Doug,

3 Doug says - "I can't say for sure if this is possible. We are talking about chemical reactions taking place in the relative vacuum of space, and I don't think chemists are used to dealing with such processes. Most likely, we would have to have a warhead that could penetrate the surface of the asteroid to some depth before it releases the chemicals. Maybe the best approach would be a cluster of such chemical bombs."

I love people who think outside the box.

Since I haven't worked chemical equations for many years, and those the most basic I should ask one question.

What would be the mass or velocity reduction in such a reaction? If I remember right the mass remains about the same in any chemical reaction. Without the change in mass or velocity the impact energy doesn't change. At least in the chemical approach the stuff that does hit isn't radioactive like the nuclear deflection and fractionation that is the current accepted approach.

The nuclear approach does a number of things for status quo. It doesn't interfere with face in the trough in the short term and further promotes the current specialized technologies inherent in the Military Industrial Complex. If of course, such a thing exists.

Gavilan

I think we should install this on it.............

Compared to the recommendations in the March 7, 2007 report to congress on deflection; it looks pretty darn good.

Gavilan