Oh Crap, an Asteroid is Coming Our Way! But Wait....

a sail can be configured to push instead of pull...

essentially the sail is split into two annular segments, a donut reflector and a "hole" that is the actual sail. the donut is furled BEHIND the "hole" and reflects light to the back side of the sail. the areas of the two are such that the hole has more area than the annular donut

There is little question that there is ice in the asteroid belt. It is really a question of how much, and where it came from. What we think we know comes from reflectance (called Albedo) and that is why the scientists say it is metallic, due to a high reflectance.

There are other stories of the creation of the asteroid belt, which would ensure that the a massive amount of ice is in the asteroid belt, as well as every other constituent of earth.

http://en.wikipedia.org/wiki/Asteroid_belt#Formation
http://en.wikipedia.org/wiki/Asteroid_belt#Evolution
http://en.wikipedia.org/wiki/Asteroid_belt#Main-belt_comets
http://en.wikipedia.org/wiki/Albedo#Astronomical_albedo

Chris

Even trickier to do!

Now you really are playing celestial billiards. That would be like pushing one car into another to push that one out of the ditch.

If you are going to apply anergy to something, it might as well be the object you intend to move.

All that predisposes that you have time to do all this. There are still many objects we don't even know about and as I discussed in post # 34. You just can't see all the bullets coming at you in time to put together a plan to nudge the object, by which time it is much too close to do anything anyway.

My point being you need to have many different type of arrows in your quiver for problems like this.

The good news is that the problem is getting more and more attention and there are brighter minds than mine working on detection and solutions to protect us.

"there are brighter minds than mine working on.."

I didn't know you felt that way.. but thanks!

Here's another thought.. however unfounded.

If we get advanced notice,
If we can get significant metallic mass into space,
If we get enough fuel to get there,
If we have accurate enough guidance system,

We could make a Baton shaped and weighted craft that would drive to the asteroid on an arc, and then just before impact, rotate slightly off axis such that he asteroid strikes the body of the vehicle on the rigid super-strong reinforced spine, which would create a deflection by the interaction of the baton weights and the body of the asteroid.

To deal with conglomerate asteroids, then nets or large steel plates can be added to the spine, or both, which will help insure impact and deflection.

Of course the spacecraft will be completely destroyed in the process, but I'm thinking that the effect of the long axis can help change the geometry of the plain old straight line impact. good steering is of course, critical.

Chris

The first problem is always detection. I think we should start sending robotic vehicles to the asteroid belt. where they will attach to an asteroid and start looking for incoming objects. Over a period of time we can get enough of them that we can be certain of not missing an incoming object that is in the plane of the solar system. Once an object with a troubling trajectory is found the nearest robotic ship can maneuver its asteroid to contact the incoming object and deflect it. By being as far out as the asteroid belt the found objects are far enough out the they won't need an excessive amount of deflection. I know we have the technology now to do this but I doubt that the resources will be available for a long time. Yes there are a lot of details that need to be worked out but this can all be done.

What are "orbital elements?"

Which of those "orbital elements" can be altered in order to avoid orbital intersect?

How can those relevant "orbital elements" be altered? Which approach is the most "efficient" approach?

Is it important that we be able to estimate the effective impulse of what ever technique we use?

Are the energies required manageable using Newtonian Impulse?

If the probability of mission success varies inversely as systems complexity; what methods require the least complex systems and processes.

Is Nuclear Deflection and Fractionation really the simplest approach?

Here is a link to the NASA Report To Congress. It appears the approaches we are debating here have already been decided.

http://www.spaceref.com/news/viewpr.html?pid=22088

Also; What is a "sling shot maneuver" and how is the orbital energy of an object changed by such gravity assist maneuvers? Isn't the speed gained on approach lost on the outbound trajectory?

Gavilan

there are a couple different ways in which one can utilize a slingshot maneuver. the first two maneuvers are unpowered and use only the angular momentum of the rotating larger body to impart a boost/braking to the approaching body. a close approach to a rotating body in the direction of rotation will add some angular velocity to the the approaching object and will subtract the same (relatively speaking, infinitesimal) amount of angular velocity from the rotating body. the same maneuver done in reverse will slow the approaching body and subtract the angular velocity from both bodies.

There is a variant of the first maneuver in which the approaching body fires it's rocket at the point of closest approach, adding both the angular momentum from the rotating body as well as the energy from the rocket to the approaching body. mathematically speaking, the propellant essentially gains energy as it falls into the gravity well and burning it at the bottom of the well releases that energy back into the system at the most opportune time.

There is a powered variant of the second maneuver as well but the rocket is fired facing the direction of travel at the moment of closest approach.

Actually, I don't think that the planet needs to be spinning and in theory, an approach can be made in any direction.

Good point, if the slingshot is to be done in order to simply change direction then that is true, if the intent is to gain or lose velocity, then the body must be either rotating or the maneuver must be under power, or both. Usually slingshots are used for a gravity boost when the spacecraft does not have enough power to reach the desired velocity under it's own power. But in theory they can be used for simple directional control as well.

I am not so sure of that.

My understanding is it is a trade of momentum. It is actually called Gravitational Assist. The larger object slows down a tiny bit and the small spacecraft speeds up.

I seem to remember a post about this and the rotational vector of the planet and the trajectory of the spacecraft have nothing to do with it.

Now, there is a special case where you can gain even more speed if the object is a rotating black hole. Besides the normal exchange of momentum there is another effect. I can't remember the name exactly, but I think it is called frame dragging or some such thing. Basically, it takes advantage of the relativistic effects of a rotating black hole if the trajectory is aligned with the spin of the black hole.

However, even solar slingshots do not use this phenomenon and any angle should do relative to the direction of spin.

Do you have a link for anything that says different? My celestial mechanics is a little rusty.

Now that I think about it, Marcot's answer makes sense. You may be right.

Frame dragging occurs in ANY gravity well, it is just most pronounced if the well is very deep. I seem to recall that NASA lauched a satellite into earth orbit and proved frame dragging occurred even in earth orbit.

I'm not sure where "Orbital Elements" came from... I searched this thread, and yours is the only result.. unless it got pinched by the thought police.

anyway.. A slingshot is a reference to the ancient weapon of a sling, used by David against Goliath, which used centrifugal force to accelerate a projectile. In this case, it refers to using a planetary body to change the path of a spacecraft. Different penetration into the gravity well produces a different angle of turn.

Good answer. The third point is also important.

So you gain the speed of the planet's angular momentum? I always thought was something to do with escape velocity, you would fire rockets pushing you toward the planet but miss the atmosphere thus increasing your velocity with gravity and thrust until velocity was sufficient. I always thought I was missing something.

Drew

Thanks for the clarification Jorrie, we can always count on you to keep us honest. =b

Hi Jorrie, thank you for coming.

With the Ion Engine, is that where particles are accelerated to relativistic velocities, and become more massive in the process, thus making better terminal velocity rocket exhaust?

Nope, an ion engine utilizes an electrically charged working fluid/propellant that is electrostatically accellerated out the back of the engine. there are several variations on this concept. most use heavy elements like cesium or osmium as the propellant. Some use the Lorenz force instead of the Coulomb force to accellerate the working fluid. It generates very low thrusts but since it is such a miser in the propellant department and the propellant is ejected at speeds much higher than those of chemical rockets, the specific impulse of the engine is very high.

thank you.

de nada.

Hi Jorrie,

thank you for clarifying!

Remaining questions: Ion-thruster, ok, but to my knowledge only some milli-Newtons thrust. So let us extrapolate and think about 1N thrust.

1N thrust (F) for 1year (dt) is roughly 40*10⁶ Ns impulse.

Mass (m) of a 1 km diameter sphere of density 4 will be 0.5*10⁹ m³ or 2*10⁹ tons.

This will give a delta-velocity of 40*10⁶/(2*10¹²) Ns/kg or 20*10^-6 m/s

So mean velocity change will be 10 micrometer per second.

Achieved additional movement (if thrusted sideways) is 400 m.

A factor of 20,000 is needed to move this big ball! With 40,000 I would feel a little bit comfortable.

Anything wrong? So what to do? That's why I prefer the nuclear explosive as an alternative. risks too, but within reach.

RHABE

Ion thrusters, like Solar Sails, generate very small thrusts (although Vasimir engines can generate thrusts that approach that of a chemical rocket, it is still limited by available power and propellant stores.) but they can do so continuously for very long times (years!) and the thrust is cumulative of course. the resulting velocities can make chemical or even nuclear (NERVA type) rockets look like child's toys. Solar sails can theoretically keep it up until the universe experiences heat death, but in reality can't really due to sail damage over time. but it is believed that spacecraft with solar sails can eventually achieve velocities that are significant fractions of the speed of light under the right circumstances.

So a lot of this is dependent on how much time you have to react to the problem. But that is true of ANY such intervention. that makes the skywatch programs all the more important. we'll need all the time we can get to work the problem and why putting such a intervention in the hands of a body like the UN is such a bad idea. They'll fritter away all of the early warning we'll be able to get and in the end we'll end up being toast.

"They'll fritter away all of the early warning we'll be able to get and in the end we'll end up being toast."

And overcharge us.

we can just put it on our visa cards and let them wait for reimbursement....

Net 30 BABY!

Hi RHABE,

Like Rorschach said, with the tiny thrust, we need lots of time. Also remember that orbital mechanics allow a very small change to make a huge difference over time. Even 10 meters will make a huge difference over a few orbits of the asteroid. I have not worked it out for this case, but I know from previous simulations that a gravity assist that is off by 100 meters altitude can make a probe miss its destination planet completely, unless course corrected later on. And that is over only part of an orbit around the Sun.

If we do not have time, my guess will also be that nuclear 'rocket propulsion' (of the NERVA type) is the best current technology available (well almost available...)

-J

"relative to the Sun" -- Thank You Jorrie!!!!!

So can we now conclude that the gravitational potential converted to speed relative to the assisting planet gained on approach will be given up on departure?

In the case of gravity assist - what is "turn angle" and why is it relevant to increasing heliocentric orbital energy? So is the specific heliocentric orbital energy gained in the gravity assist maneuver gained by a change in speed or heliocentric relative velocity? Why does the change in heliocentric "flight path angle" have relevance here?

When we consider system and process complexity; why is the ion tractor a more viable approach than Electro-dynamic Braking? (EDB)

Even if the magnetic field of the sun WAS "entrained" would that make solar field unusable as an excitation field?

Using estimated solar field strength at mean earth orbital radius, what would the induced voltage be in a coil wound with 1000 meters of conductor? I understand the induced voltage will be function of the angle in which the coil is moving relative to solar field and I am confident that in most objects of interest the relative velocity is near the optimum angle for induction. Attaching the coils and power dissipation circuits to the asteroid becomes quite easy IF it is an iron-nickel object. It becomes more problematic if it is a "rubble pile"; one more reason to study these objects.

The Aten objects seem to be the greatest challenge we face; but because of the mechanics of their orbits they are most suitable for EDB.

Even if the induced voltages are only a few millivolts, meaningful orbital braking can be achieved in consideration of the enabling technology of superconductivity. If the chosen method of power dissipation is the production of RF energy then the challenge of circuit acceptance can be met by keeping the circuit at the natural resonance of the circuit. If that can be accomplished then the total circuit impedance becomes a simple function of circuit resistance. (Can nickle-iron be heated using RF energy?)(If so why does the Stefan/Boltzmann law come into play?)

The total delta V can then be derived from simple kinetic and power equation.

Where the delta V = sqrt(2Pt/m) where P=Induced Circuit Power, t=process time, and m=system mass.

The greatest advantage to this method is that it will require no fuel mass for deflection. Secondary advantages include that the braking vector will always be opposite the orbital velocity, the impulse can be easily and accurately extrapolated from circuit power, and the process is simplistic with a natural tendency of the process being to stop the rotation of the object.

We have some experience with ion propulsion - we have VAST experience with electro-dynamic braking applications.

Gavilan

Hi Gavilan, you wrote:

"So can we now conclude that the gravitational potential converted to speed relative to the assisting planet gained on approach will be given up on departure?"

Nope. We are not talking about converting gravitational potential energy to kinetic energy here. This also happens, but all kinetic energy gain is given up on departure. Gravity assist works by permanently transferring some of the mechanical orbital energy (orbital angular momentum) of the planet to the probe. It is similar to throwing a ball head-on at an approaching bus. The ball comes flying back past you at a greater speed than what you threw it at, while the bus has lost a little speed.

"In the case of gravity assist - what is "turn angle"..."

I don't know that term. The flight path angle relative to the planet determines whether gravity assist will decrease or increase the orbital momentum and by how much. It is a matter of vector summation, as shown in this Wikipedia diagram.

I do not know much about the Electro-dynamic Braking (EDB) idea. If you can find someone to calculate the energy you can extract, I can however help with the orbital calculations. Take note that a spinning asteroid may pose orientation problems if you attach the coil to the object. Maybe an ion-rocket in a fixed position relative to the spinning object, with a huge EDB coil on board might work...

-J

Hi Jorrie!!

Glad to see you back.

From "Spacecraft Attitude Determination and Control – Ed. By James Wertz" – page 60.

"The magnitude of the velocity change, delta V, that will be produced in a flyby trajectory is a function of the turn angle between the two asymptotes of the hyperbola."

I am giving the equation as I would write it in basic.

Abs(DV)=(2*Vh)*(sin(angle/2))

That is – The absolute value of the delta V (DV) equals 2 times the hyperbolic approach velocity (Vh) times the sine of ½ the turn angle(angle).

The gravitation parameter is factored into the last component of the above equation as

Sin(angle/2)=sqrt(1+((Vh^2)*q)/u) where q= perifocal distance = distance of closest approach and u is the gravitational parameter of the assisting planet.

You said that you favored the ion propulsion tug method.

What is the specific impulse of a modern ion propulsion unit?

How much ion propellant is required to induce a usable change in velocity on an object of 2.7e10 kgs moving at 30 km/s?

I wonder what a miss distance of 30,000 km with 3 years lead time would require in terms of ion fuel mass and electrical power.

Gavilan

Hi Gavilan. Thanks, I now see what you meant by 'turn-angle'. It is exactly the same as what I would have called the 'deflection angle' during the flyby.

The equations that you quoted for flyby is correct for course changes, but as they stand they do not give the delta-energy in heliocentric coordinates, because it can be positive, negative or anything between. For that one has to take the vector dV and vector sum it with the planet's orbital velocity vector at the point of flyby.

The specific impulse of ion engines are very high, normally exceeding 1,000 seconds, or 10⁴ N.s per kg fuel, so they are very fuel efficient. Single experimental Xenon thrusters have produced more than 1N of thrust, so let's take these figures as ballparks. The acceleration by 1N thrust on your 10¹⁰ kg rock would obviously be a = 10^-10 m/s². Applied over 3 years (t ~ 10⁸ seconds), it gives a distance of s = 0.5 a t² = 0.5 x 10^-10 x 10¹⁶ = 5 x 10⁵ m. That's 500 km, so if my sums are right, we will need 60 such ion engines to move that rock 30,000 km in 3 years.

How much fuel? The total acceleration is a = 60 x 10^-10 m/s². The total velocity change is dV = a t = 6 x 10^-9 x 10⁸ = 0.6 m/s, resulting in a total momentum change of 6 x10⁹ kg.m/s on the rock. Divide by the 10⁴ kg.m/s specific impulse and I get 6 x10⁵ kg (600 tons) of thruster fuel. That's heavy, about 10 tons for each of the 60 ion thrusters (if my sums are right - someone please verify). Tough, but maybe possible.

Note: this is completely ignoring the effect of this thrust on the orbital parameters of the rock around the Sun - maybe we need a lot less than the 'brute force' of 60 engines for a 'safe' change...

-J

The ABS used in the equation is the absolute value of the speed change. The speed change is the change in hyperbolic excess speed.

Wouldn't the net change in the solar system barycenter relative angular momentum be a function of both the change in speed AND the final flight path angle relative to a line running from solar system barycenter to the spacecraft?(the r vector)

On to changing the speed of an asteroid.

The amount of average power that would have to be induced and dissipated in a EDB process would approximate (.5*m*(VI^2)) – (.5*m*(Vf^2))/t where the final change in velocity is .6 m/s and the average change over t =.3m/s (delta v= 1/2at) where t = 3 years. The change in displacement = 28401 km. That's cutting it close.

If I did my numbers right that would require an average power dissipation of about 5 megawatts given an initial speed of 30km/s and a mass of 2.7E10kgs!! (Also the approximate power needed for the ion grids?)

This is no easy nut to crack. But at least both the Ion Tractor and EDB methods have calculable impulse.

Given an average induced voltage in each 1000 meters of conductor of .3 volts and a total of 10 coils with 1000 meters of conductor each the average resistance in each coil would have to be maintained at about 1.8 micro ohms.

So you would have 5 megawatts of power to drive the subsystems to keep the coils superconducting at 1.8 micro ohms. What if any was left over would have to be dissipated by some other method. An imaginative method of maintaining that low of a circuit impedance would have to be used. I have some ideas in that regard.

The .3 volts is a shot in the dark at approximating average induced voltage in each inductor where the object is an ATEN object with aphelion approximating the orbital radius of Earth, a perihelion approximating the orbital radius of Venus, and an inclination approximating that of earth orbital plane.

Gavilan

Hi Gavilan, you wrote:

"Wouldn't the net change in the solar system barycenter relative angular momentum be a function of both the change in speed AND the final flight path angle relative to a line running from solar system barycenter to the spacecraft?"

This is roughly what I said in my prior post: "... take the vector dV and vector sum it with the planet's orbital velocity vector at the point of flyby." dV is a function of the original orbit (no planet to swing around) and the flight path after the flyby.

You wrote: "If I did my numbers right that would require an average power dissipation of about 5 megawatts given an initial speed of 30km/s and a mass of 2.7E10kgs!!"

Like other commentators, I'm not convinced that anywhere near this amount of power can possibly be generated by movement of a coil in the Sun's weak magnetic field.

-J

Hi Jorrie:

You stated "Like other commentators, I'm not convinced that anywhere near this amount of power can possibly be generated by movement of a coil in the Sun's weak magnetic field."

E=Blv sin@

Things are relative Jorrie. Although the excitation field (B-sol field) of the induction process is very weak the velocity component (v)is very large. The challenge is maintaining circuit acceptance. Superconductivity is the enabling technology in this type of process.

The problem is not the weak excitation field - it is maintaining a non-fluctuating current in the inductors in order to maintain the extremely low circuit impedance required to extract usable power at such low voltages. There is plenty of potential energy to work with (the orbital energy of the PHO) its just a matter of extracting it.

Gavilan

Hi Gavilan,

As I have it, V = BLv sin@, where V is the voltage difference between the two ends of the linear conductor of length L. Unless there can be a current flow by means of plasma around the conductor, there is no energy being converted. In deep space there is little plasma, so how do you propose to convert the voltage to energy?

-J

I get the same voltage drop. But I think that there's an implication here you started Jorrie, but didn't finish here. To complete the circuit for current to flow and power to be drawn to create this brake, the return path must follow the same length but the current must flow in the opposite direction. This is the fundamental effect known in motor design as back EMF. I do not see this being useful.

Hi RF,

At low-earth orbit (LEO) height, my understanding is that the circuit is completed via the plasma available there. This return circuit is not via a 'same length circuit' (a conductor), which cannot work, because the same voltage with the same polarity will be generated in it, resulting in no current flow in the circuit.

AFAIK, the NASA tethers effectively worked like lightning - some of them even got 'fried'...

-J

Hi Gavilan,

solar field strength is said to be near 20 nT (nano-Tesla) out there near Mars orbit.

Electro-motors use near 1 T! So forget about using this.

There is no optimum angle for a coil as the coil has to be rotated in order to alternate the induced voltage. Only a change in the flux through the area of the coil is inducing a voltage. Flux (Vs) = flux-density (T) x area (m²)

Iron-nickel is good for inductive heating but as temperature is rising the resistance is going up and the dissipated power going down (if constant voltage).

The "tether voltage cannot be used unless you make an electron spray (by high voltage) at one side. Only this will let some current flow. And will use most of the generated energy. I will think about braking capacity.

RHABE

Hi Rhabe:

Thanks for the reply. Field induced drag has been recognized as one of the limiting factors to orbital life span in low earth orbit for decades. (See - Satellite Attitude Determination and Control - Wertz) I am mentioning this only to make the readers aware that electro-dynamic braking in space applications is nothing new.

The easiest empirical demonstration of Electro-dynamic braking is to suspend a piece of aluminum on a pendulum and swing it between the poles of a horse shoe magnet. The very dramatic effect of electro-dynamic braking becomes quite apparent.

There is no need to "spin" a coil. The coil cutting the sol field will work just fine. (See - any basic physics text) The power is a function of circuit impedance composed of both reactance and resistance. The induced voltage would be DC. This induced DC voltage would be used to pump a RF circuit where the circuit is operated at the tuned resonant frequency of the circuit the reactance becomes 0 and total circuit impedance becomes a simple function of resistance. If the circuit can be made superconductive very significant power can be induced even at very low voltages. Also, the induced voltage is a trigometric function of the velocity vector angle relative to excitation field in ANY electro-dynamic induction process.

I understand that in most materials conductivity (the reciprocal of resistance) varies inversely as temperature. I also understand that the body of the asteroid will dissipate power in the form of IR energy as approximately the 4^th power of its absolute temperature. (See Stefan – Boltzmann Law). Because of this the decrease in its ability to absorb the energy would be negligible. Also; RF heating of the asteroid body is just one of many means of dissipating the induced power.

The objects of greatest concern are the ATEN objects; specifically those objects whose orbital inclinations are close to that of Earth. The aphelion of these objects is just beyond earth orbital radius with most of the orbit inside the orbital radius of the earth.

I am not confident in the field strength given at Mars radius of orbit which is far beyond the aphelion of most objects of concern. I am confident that the Sol Field Strength is a cube function of the distance from Sun Center of Mass.

Electro-dynamic Braking is the only means of orbital braking that uses no consumables. It is simple and reliable in operation and is well understood with decades of terrestrial and LEO applications.

In consideration of complexity and reliability Electro-dynamic Braking is by far the most reasonable approach when dealing with objects where there is adequate lead time.

Gavilan

Hi Gavilan,

You are obviously well versed in this magnetic field stuff, and brilliant. makes me curious what you do for work. (don't feel you have to answer)

But I have a question. You mentioned superconductors, which I'm assuming you would coil around or mount on the asteroid. If ED braking is to be accomplished by passing a coil through a magnetic field (sol, earth, mars) then is the inertial energy of the asteroid not converted to heat through the resistance of the coil? Therefore I'm wondering just how the superconductor part works? Is the electrical resistance of the conductor not a requirement in this application?

Chris

Yes, the resistance of most materials increases as temperature; but unfortunately the inductive acceptance of the circuit will be an inverse function of that temperature also. This means that some of the power to be dissipated will be used to power the subsystems used to maintain superconducting temperatures in the induction coils. The lower the temperature that can be maintained (and therefore the resistance) the higher the induced power and the less energy the cooling system will have to handle for any given power. I have not looked at the permeability of liquid nitrogen but perhaps it would be suitable to use as the coil(s) core? If the nitrogen can be re-cooled and reused then it would not be considered a consumable.

The purpose of the process is to convert the velocity component of the orbital energy to dissipated energy through any means possible.

That means powering the subsystems, including but not limited to, producing RF for heating the body of the asteroid (a huge area for dissipating the energy as IR), producing field to use as an action field in field effect propulsion, or scavenging mass from the asteroid body to use in Newtonian propulsion where the power is used to power a mass driver.

By changing the orbital velocity the orbital intersect time is changed to make it a miss. If enough energy is dissipated then the semi-major axis; and/or if the power input is at the proper time in its orbit, the eccentricity or other orbital elements can be changed so that the PHO no longer crosses Earth's orbital path. On sure way to deal with the problem is to bring it to impact with Venus or another planet.

The concept uses the orbital energy of the object itself to power all primary and secondary processes. It requires no consumables and no nuclear or other auxilary power production systems.

The delta V = sqrt(2Pt/m) where P=Induced Circuit Power, t=process time, and m=system mass.

Here is a short basic algorithm to play with. I think its right but no guarantees.

10 CLS

20 CLEAR

25 PRINT" The Relationship between Delta Velocity, mass, power, and time. by Gavilan"

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

Gavilan

Hi Gavilan,

I still do not understand how a magnetic field that is not varying with time or location can be used to induce drag.

""The easiest empirical demonstration of Electro-dynamic braking is to suspend a piece of aluminum on a pendulum and swing it between the poles of a horse shoe magnet."

This is quite clear but depends on the magnet being smaller than the piece of aluminum.

Thus an area beneath the poles of the magnet have a high concentration of field lines. If the magnet is moved (or the plate) then there is a movement of this field concentration according to the velocity of movement. Thus at the place where the magnet was there is induced an eddy current that maintains the former magnetic field for a while and at the new location there is an eddy current with opposite direction that opposes the buildup of magnetic field. These eddy currents have to be closed else only voltage and no current so no braking action.

So from this I deduct that any constant (with time) magnetic field that is homogeneous within the size of the conducting "plate" does not induce any currents.

There is simply no dΦ/dt or change of magnetic field with time. So no induced voltage nor current. So where shall a braking action come from?

Also no dΦ/dx that translates with velocity into a change of magnetic field with time.

The coil that is cutting the solar field with a given velocity will see a potential (voltage) on one side equal to the voltage at the other side, so once more no current!

Please help or clarify.

RHABE

Hi Rhabe:

"This is quite clear but depends on the magnet being smaller than the piece of aluminum."

Are you proposing that there must be a "field gradient" in order to induce voltage?

I will suggest that the magnet could be infinitely large and the piece of aluminum infinitely small and electro dynamic braking would occur according to Lentz's law.

"There is simply no dΦ/dt or change of magnetic field with time. So no induced voltage nor current. So where shall a braking action come from?"

What you have defined is the Rate Of Change or ROC. The ROC is a function of the field and velocity of the inductor through that field. The braking action comes from the magnetic field produced by the current which opposes the field inducing it. That current (field) is induced in the structure of the aluminium itself.

"Also no dΦ/dx that translates with velocity into a change of magnetic field with time."

I don't understand what you mean "that translates with velocity."

E=BlV sin@

Where B is the field, l the length of the inductor and V sin@ the velocity component of the inductor.

In this equation the ROC is a function of the velocity - another way of inducing current is to oscillate B.

The dimensional size of the object producing the field in relation to the the inductor is irrelevant. Your premise that the induction process "depends on the magnet being smaller than the piece of aluminum" is incorrect. Again I will refer to the empirical evidence provided by the Space Shuttle Tether Experiments, the Electro-dynamic Orbital Braking that occurs in LEO as a result of Earth's Electro-magnetic field acting as the excitation field in an electro-magnetic induction process where the inductor (space craft) is dimensionally MUCH SMALLER than the magnetic field, and the aluminum pendulum swing.

Gavilan

Hi Gavilan,

Are you proposing that there must be a "field gradient" in order to induce voltage?

Yes indeed, a gradient either with location (if there is a velocity of the object) or with time. The induced voltage is Uind = dΦ/dt or ROC of magnetic flux. Only if this voltage can generate a current then is braking possible. If the field is uniform within the geometry of the metallic piece then there is no change no voltage no current.

"E=BlV sin@" ok, I prefer E=B x V or U (voltage) = B x V * Length (of conductor).

So if you have a loop (necessary to have a current) you need voltages that add up on going around the loop. But a loop inside a homogeneous field has a minimum voltage at one location and a maximum voltage opposite to this. So no current.

Think about 2 parallel wires with a small distance apart. In both wires there is the same E = B x V. So if you connect the ends: no current, simply paralleled voltages.

"another way of inducing current is to oscillate B." OK, that's why I wanted to rotate the whole loop in order to generate an AC current by turning a coil in a constant magnetic field. As the velocity vectors of the coil are opposite to each other the voltages around the loop will add in this example.

"empirical evidence provided by the Space Shuttle Tether Experiments"

I do not have the details so I cannot comment on these experiments. but if there was one tether = wire, so a voltage gradient along that gave a high voltage at the end. If this end is sharp (pin-like) then there will be field-emission of ions or electrons or sucking of charged particles from around. This can give some current so some braking action.

"Electro-dynamic Orbital Braking"

I have no idea how this might work. One possible explanation would be the donut shape of Earth's magnetic field and the satellite moving at an inclination to the equator, so there is a varying field minima at high latitudes, maxima near equator?

Once more pendulum: try to sketch the electrical potential and voltages by this potential if moving with constant direction and orientation. How to get the current loop?

Once more with changing magnetic field (with time) and cross section of pole smaller than aluminum plate : circular current path around center of pole.

Once more with velocity of plate (velocity vector parallel to plate): 2 counter-rotating currents, 2 circles deformed to a near ∞.

So how to deflect the asteroid? Tether coupled with ion-drive?

RHABE

"Electro-dynamic Orbital Braking" I have no idea how this might work. "

Maybe I'm misreading you, but here is my humble opinion. I don't think you need a varying field. You simply need a coil (conductor) to pass through the field, or a field to pass through the conductor. When the conductor passes through the field, the field interacts with the electrons of the atoms of the conductor and this induces current flow, which is converted to heat by the electrical resistance of that conductor.

Because there is this interaction between the atoms of the conductor and the magnetic field, the magnetic field is deformed by the conductor, like the wake of a boat passing in water. The field has a 'drag' effect on the coil because of the electrical resistance. That effect is the 'braking'.

maybe I'm misunderstanding what the question is? I'm not certain a circuit is required. If the electrons are pulled from their sockets and there is no where to go, they will have to return and thereby polarize the conductor, or be expelled into the vacuum of space. A circuit would be better so electrons are not lost, but is it absolutely essential? maybe. experiments will tell.

Chris

Hi Rhabe:

Your premise - "Yes indeed, a gradient either with location (if there is a velocity of the object) or with time."

Are you suggesting that a moving conductor through a uniform and non-varying field field will not induce voltage?

Gavilan

Hi Gavilan,

voltage: naturally yes.

But no current as no loop with voltage around the loop.

RHABE

Hi Jorrie,

I agree to your thrust-time statement.

But do we have the time (years)?

In my thinking these objects may be coming in with highly eccentric trajectories from outer parts of our solar system.

If coming any 200 to 2000 years? We would not have any information in advance.

So if (unlikely but possible) the first approach will be a hit - what then?

And if the second turn is changed by the unknown masses out there so that the originally estimated trajectory is changed considerably?

So I would strictly prefer a system that can do its work within days to weeks!

Vasimr: yes, this should be pushed into reality. Undoubtedly it will need a nuclear reactor if beyond Mars - but is this a big obstacle?

"Nuclear rocket propulsion": I would bet that this will never happen. Would be fine to shrink the whole NIF system into a transportable payload.

So for the moment: stay with existing technology, chemical rockets, nuclear warheads, some modification in triggers and mass distribution. Test this with the next near-miss object at a distance that won't disturb us. (Distance to Moon may suffice.)

In parallel: further develop this Vasimr ion-thruster - would be great for many other missions too.

Have a nice Easter (to everybody)

RHABE

nuclear rockets have been statically tested out at jackass flats back in the late 60's, they were also considered by NASA for the '90's Mars mission that got defunded, so they should be considered "near-existing technology". Mechanically they are pretty simple devices, they are essentially a hydrogen cooled reactor with a graphite fuel bundle support frame with a rocket bell in the coolant path. From the Wikipedia article:

"...All test objectives were successfully accomplished, and the first NERVA NRX operated for nearly 2 hours, including 28 minutes at full power. It exceeded the operating time of previous KIWI reactors by nearly a factor of two.^[2]

The second NERVA engine, the NERVA XE, was designed to come as close as possible to a complete flight system, even to the point of using a flight-design turbopump. Components that would not affect system performance were allowed to be selected from what was available at Jackass Flats in order to save money and time, and a radiation shield was added to protect external components. The engine was reoriented to fire downward into a reduced-pressure compartment to partially simulate firing in a vacuum.

The NERVA NRX/EST engine test objectives now included:

1. Demonstrating engine system operational feasibility
2. Showing that no enabling technology issues remained as a barrier to flight engine development.
3. Demonstrating completely automatic engine startup.

The objectives also included testing the use of the new facility at Jackass Flats for flight engine qualification and acceptance. Total run time was 115 minutes, including 28 starts. NASA and SNPO felt that the test "confirmed that a nuclear rocket engine was suitable for space flight application and was able to operate at a specific impulse twice that of chemical rocket system [sic]."^[3] The engine was deemed adequate for Mars missions being planned by NASA. The facility was also deemed adequate for flight qualification and acceptance of rocket engines from the two contractors.

The Rover/NERVA program accumulated 17 hours of operating time with 6 hours above 2000˚K. Although the engine, turbine and liquid hydrogen tank were never physically assembled together, the NERVA was deemed ready to design into a working vehicle by NASA, creating a small political crisis in Congress because of the danger a Mars exploration program presented to the national budget. Clinton P. Anderson, the New Mexico senator who had protected the program, had become severely ill. Lyndon B. Johnson, another powerful advocate of human space exploration, had decided not to run for a second term and was considerably weakened. NASA program funding was somewhat reduced by Congress for the 1969 budget, and the incoming Nixon administration reduced it still further for 1970, shutting down the Saturn rocket production line and cancelling Apollo missions after Apollo 17. Without the Saturn S-N rocket to carry the NERVA to orbit, Los Alamos continued the Rover Program for a few more years with Pewee and the Nuclear Furnace, but it was disbanded by 1972."

The most elegant mission flown to date related to this topic is the Muses C Mission (now known as Hayabusa) flown by the JAXA.

What a great mission! Regardless of the final outcome - NOBODY has come close to this mission in applying the technologies needed to address the issue.

This was cool.

Gavilan

do you have any links for us master?

I personally like the " move the earth" movement. Something to do with politicians and maybe a temporary time shift like daylight savings. We could mandate all the clocks be turned back a couple of hours so the earth shifts out of the way until the danger is passed.

Don't be surprised if that doesn't play with some and why not?

I just listened to some US official publicly state to some admiral that he was concerned that overpopulation on Guam might cause the island to tip over and sink.

Kinda says something about the intelligence level of our elected officials doesn't it?

Dunno if it is true or not, but our own local embarrassment, CongressWOMAN Shiela Jackson-Lee (that is how she says it),was said to have asked the controllers out at JPL to have the Mars Rovers roll over to where Neil Armstrong planted the flag and take pictures of it..... They had to explain to her that the flag and the LEM was on the MOON, not MARS...

I gotta hit snopes and see if that is really true, she has stuck her foot in her mouth a number of times over the years so it wouldn't surprise me if it were a true account.

We can't all be smart...

Just hit Snopes looking for that one and could not find it, so the veracity is unconfirmed at this juncture. (not that Snopes hasn't made mistakes themselves a time or two.) but I did find this link:

http://www.seds.org/archive/spaceviews/970915/cap.html

TECHNICALLY any slingshot maneuver that uses the earth IS moving the earth by an infinitesimal amount....

Just Saying....

I've been reading the thread and am very thankful to Chrisg for remembering last years April Fools Day Transcendian Speech.

AH, Bhankii, Rhabe, and now even Jorrie have weighed in. Mostly the delivery systems are discussed. Capture and steer, or deflection systems are not as discussed.

It does appear that some work on the International Space Treaty is called for.

I am grateful for the GA concerning my post here in this revival of last years speech subject. Last year we reviewed much of the problems and options.

This year it would appear that there is more evidence of engine works that was not as completely available, as last year. Over the last year there has also been more information readily available as concerns water on the Moon.

To turn nations from throwing rocks at each other to protecting the rock we live on from other rogue rocks will be a big trick.

It would appear that there are technologies developed to points of near to possible for the three delivery system engine needs. Those are for the 3 day warning, the 3 year warning and then the 100 year warning.

I suggest that for all the delivery systems one steerage system be used for simplification that will work on the minimum to maximum sized tumbling threat that AH points out cannot yet be fixed with beams.

What the hell will stick to any asteroid and burn on it for steerage or deflection?

Accleration times for Solar Sails are long. Ion Rocket accleration times are long. The nuke rocket engines offer some quik response time possibilities, but then we have gotten some fast chemical rockets to go.

Last year Bhankii said it would take 10 years and 100 billion to do the system up to running. What's changed now, this year?

T-man, the 10 years/$100 Billion number is if a governmental entity is allowed within 100 miles of the project.

You'd be amazed at what Lockheed or Boeing or Dick Rutan could pull outta their arse if they were told "get 'er done, money is no object" and then left to their own devices. After all, the people of Boeing/Lockheed/Scaled Composites (now part of Boeing) are stuck on this rock too and have just as much to lose as you or I. NASA is it's own worst enemy sometimes. Look at what Lockheed's Skunk Works came up with in the 60's! The U-2 and then the SR-71!

A lot of the time and money goes into the beauracracy and all the environmental regulations and testing and such. If NASA had to operate with the same safety margin today that Alan Shepard faced when he climbed aboard that Redstone, or John Glenn when he climbed aboard that Atlas (which had a near perfect record of blowing up on the pad previously!) they would be crapping their pants. Attempting to launch a NERVA rocket, even as a second or third stage, would have Greenpeace screaming their lungs out. Someone would have to simply bust heads and keep them out from underfoot in such a situation. After all, what good does it do us to worry about nuclear contamination from a failed launch if the alternative is death from above?

Just remember we have three Saturn IV's sitting on the ground in various states of repair that we could if we had to refurbish (even cannibalizing the other two to make one flyable one if we had to.) and fly if push come to shove. And we still have three shuttles that we could loft pieces to LEO for later assembly as long as they don't go and destroy too much of the tooling to make the SRB's and the tanks and such.

We have pieces that we could throw together in a relatively short time frame if we were willing to take the risks involved. And a lot of them could be lauched under automated control if need be to minimize some of the risk.

The problem is not that we don't have the tools or the technology to deal with asteroids. most of the technology has been around for years in one form or fashion. We simply have not had the political will. Like Jim Lovell said to his wife the evening of the first moon landing, in his book "Lost Moon", "It isn't that we didn't know how to go to the moon, we just never decided to until now."

Have we finally decided to do something about this problem? No we haven't, and that is a shame.

Off topic score ten is right extreme. Possibly some of you don't remember or weren't around for the important discussion concerning the war with asteroids, and comets prior to last years April Fools Day Speech.

Agreed! I gave you a no vote to bring it back down a little. =b

I can top that, I made a little joke that included a Monty Python link on the single phase to three phase thread. I thought I made it OT which would make it 10 OT but now it's at 1000 OT.

Wow, 1000, OT! I'm reminded of the student who succeeded in getting a 0 on the SATs.

Anyway as far as the continuing war on Asteroids, I have considered that the order of response may be best if concentrated on the most dangerous threat first. The most dangerous threat is the Rogue for which there is short notice. To me this implies a fast delivery system capable of direct targeting and deflection or steerage.

Good thing about that strategy is that it would offer protection from the known, suspected, and unknown threats, therefore being cheapest.

"...To me this implies a fast delivery system capable of direct targeting..."

like an interplanetary Phalanx gun, but with relativistic bullets.

Naw, just a coil gun firing anti-matter iron projectiles.

I had a GA disappear yesterday entirely.. no idea which one it was.

"What the hell will stick to any asteroid and burn on it for steerage or deflection?"

Heres a quote from the movie "Saving Private Russell"

"...Sticky Bombs... Its in the field manual... take a standard G.I. sock, fill with as much Comp-Nuke as it can hold, and cover it all with axle grease... Sticky - Bomb!"

Has anyone rung Bruce Willis yet?

Chris, Have you considered, rather than firing a big mass at it, attaching a parachute to it?

"parachute" meaning "solar wind sail".

Might be a fair bit lighter to get up there.

Kyzine

Hi Kyzine,

I've seen the little solar whirligigs move in the sunlight, but I've yet to see a solar sail. I don't know if they work, but if it does, and if the loose conglomeration can be encapsulated, and if there is enough time, then I'm all for it.

I think ultimately that studying Harmonics and methods of inducing and controlling vibrations in matter is what will lead us to understand matter (space-time-inertia-gravity) and by mastering that, we will be able to get the jump on situations like this. I think that ultimately again, that we are dealing with a quantum binary oscillation of the most minute bits of potential, flicking between two points in space-time, of which, the last one will be the past... so matter is hard and inertial, because it is 'yesterday'. that's my story and I'm sticking to it.

All we have to do is to learn to control this process by synchronizing with it, and then beating upon it a signal which will amount to a slight change in the orientation of the signal, and subsequently a change in inertial direction. If every quantum of energy or particle within a body changes its inertial path slightly, it will solve this problem. Of course you can also call this 'antigravity, but it isn't really anti-anything. better to call it modified inertia. The ancients were reputed to be able to lift stones to the sound of music. If that is a clue, then sound is the means by which atoms can be beat upon. I know there is no sound in space, but in this case, the sound would be in matter, so it would work.

but hey I can't prove any of it. so I'm just another wishful thinker.

Pump up the volume!

Chris

Hi AH, thanks for the pre-warning!

In a 'hit-case' similar to this one, there is probably nothing we can do but run for shelter...

-J

This one is about 1/2 the size of the Tunguska Event of 1908, which was believed to be an airburst.

Although, a lot depends on velocity and angle of impact, the actual potential damage from a rock this size still could be pretty significant.

Actually AH, it looks like this one is going to give us 64 years worth of warning. It is expected to POSSIBLY impact the Earth on April 6, 2074.

So this may no longer be a hypothetical exercise.

Exactly the scenario I mentioned in the Apothis asteroid discussion. The probability that a impactor striking Earth on it's first noticed approach is a lot less than people think.

Thing is, we are not sure when the first approach was!

We have no idea if this thing has passed this way before.

My whole point has been that nature can easily pull a surprise out of the blue (or black) without much, or any, warning.

It is folly to believe that we will always have years to derail an event like this. We have, on a very short relative cosmological scale, begun to open our eyes to the probabilities and we are still are just getting our arms around the scope of the problem.

AH, that is why Scotch was invented!

You all know that I can be a stickler for details. I said the first noticed approach would not be the actual impact trajectory. My idea is that it will be just as difficult for the Earth orbit crossing object to hit us on the first path as we will have hitting the object with our kinetic impactor.

You guys know quite a bit more than I do in some of these areas. Still I can read and have some experience with getting things done.

More than once the guy I was working directly under would ask me to do something in a round about way, and I would say, "This won't work." I would say, this on the basis of the instruments on hand, and time involved. Still they were in charge, and I was to work with them as an aid. So, I would say what my suggestion was, but hey I'll do it your way! Now I am not without tact and sometimes here in the interest of brevity will not go into whether or not I looked them in eye, or raised ever my voice, for somethings don't matter. Not going to kill anybody, just going to waste some time...

More than once I've had people I was second to, and made suggestions too at the start, get a bit on, and turn and say, "That idea you had, lets try it now."

As as quick an example as I can give, the DP said, "Want you to bounce some light into the pool for this shot of the women in the pool." I said, the lights we have are not strong enough to give you the exposure you need. Direct light will work.

"Well I want some softer light."

Okay, it all pays the same. I'm just the Electrician, the Gaffer, still it didn't work out that with what we had, his wants could be satisfied in the time available.

"Ah, well, you were right." I just turned the lights around for direct lighting of the subject. Only 35 to 45 minutes wasted. Thats only about 475 dollars of crew time. Talent infront, well, not my department.

Far as Asteroid Wars and Planet Defense I'm for the Direct approach, with what we got, that will work for Rogues and long known threats. All other approaches may have other benefits eventually, but for example, a cannon in the house or drug behind my car, isn't of much use when dealing with a carjacker, whereas a pistol or a shotgun might well be the best answer to the problem.

Friend of mine was out delivering papers in the early morning in a car before the sun was up. Couple of guys came running up yelling, "Give us your wallets and all your money!" Friend put his pistol towards them and said, "I've got a better idea. Give us your money and we'll give you a f-king newspaper."

Now they apparently didn't want any newspapers and ran away, but my point is that asteroids that hit Venus or Saturn or are not to be of any surprise, are okay to think about, but short term real short notice, well you need to have something that works fast and directly that changes the situation.

QUACK! I mean DUCK!

Just adding to the font of fun: Solar Furnace Could Save Earth _{(sorry if this has been covered already; I haven't kept up)}

...should a meteor be spotted approaching earth then a spacecraft equipped with a system similar to that of the [White Sands Missile Range] solar furnace could be launched to intercept the meteor.

Once it arrives at the meteor the spacecraft would deploy its system and use the power of the sun to superheat a spot on the meteor. The heat would cause that spot on the meteor to melt and fracture, throwing off small bits of debris; the force of which would act like a small rocket slowly pushing the meteor and changing its course.

I think it has been covered, and the problem is what if the asteroid is spinning? True you could heat the polar axis, but it may not be pointing in a direction that is best for moving it.

Drew

Actually, if you realized that the thermal mass would be such that the surrounding rock would draw off the heat quickly, you could treat it as a constantly moving force moving opposite the spin and the recoil vector would continue to point towards the center of rotation.

Hi,

did you check the mass of this solar furnace?

and ejection velocity, mass flow, ...

RHABE

Why? If Bruce Willis can't put it in his pocket, then the CGI guys can just add it in after the filming. Wait a minute, at the temperatures this thing can produce why don't they just use this to burn off the oil floating on the Gulf of Mexico water? Oh wait a minute, that's another thread.

That image kinda looks like a planet failed to form from the rubble, or perhaps one was destroyed by a giagantic collision.Perhaps the remnant was the one that hit the Earth during it's formation period, and the remnant from that is our moon.?

Just speculation, but interesting where that idea could lead.

The problem I see with impacting an asterois with a projectile is the composition of the asteroid itself.It may be solid,semi-soild,loosely compacted, or any combination in between.To scatter it would be worse that leaving it alone.A gentle push over a long time period would result in a large change in it's final path.Such has been proposed by beaming a concentrated sunbeam at the surface,and allowing the resultant boiling vapor act as an engine to push it into a different path.
As previously stated, detection is the key, and money is the lock.We have politicians that cannot see past the end of their nose, much less into space or the future.The future looks grim for any type of government funded detection system.

We are no better off than the dinosaurs, and may suffer a similar fate.

Keep your fingers crossed .

Impact, Standoff Nuclear, and Laser deflection have the same drawbacks - It is impossible to even roughly estimate the impulse. Without a close approximation of the impulse it is impossible to estimate the net change in orbital energy.

In consideration of this topic; the change in orbital energy or eccentricity due to the energy inputs will be the defining variables in calculating orbital path intersect time. It is orbital path intersect time that we would be attempting to change.

Since eccentricity is independent of orbital energy; I have often wondered if changes in eccentricity are less energy intensive than changes in orbital energy. Perhaps there is an expert out there who can answer that question.

An attempt to change the orbital plane of the target, although a possible method of eliminating orbital intersect completely, is probably too energy intensive to be considered as a viable alternative.

Again I refer to electro-dynamic braking as the preferred method where the di-pole solar field is used as the excitation field and the orbital velocity of the target provides the rate of change components in the induction process. It requires no other input other than the orbital energy of the target itself. (I have read the expert gobaldy gook about sol field not being dipole in nature; on solar system scale it is both dipole and well defined.)

This process allows for very exact calculation of energy input which translates to very exacting calculation for change in orbital energy and/or eccentricity which results in an accurate prediction of the change in time of orbital path intersect.

We can do this but in order to be considered it MUST come from a vetted source; something I will never be.

A side note -Hayabusa was the defining mission that shows intersect and landing on an asteroid can be accomplished. The most elegant mission ever flown by human kind; the Little Space Ship that Could - DID! And I have the T Shirt!!

WAY TO JAXA!!!!!

Gavilan

an upcoming committee meeting in Boulder Colorado. July 8 & 9 2010

http://edocket.access.gpo.gov/2010/2010-14408.htm

Boy I sure ought to go to that and do my war on asteroids speech of a couple of years ago. The current issue of The Week in The Last Word on page 44 says the good news is that over the next 200 years we can only expect a city or two to be wiped out by asteroid strikes. In conclusion the bit says evacuation of the city expected to be obliterated by small asteroids is the recommended response.