Combined Speed And Direction Meter For Space Ship.

Isn't this more-or-less a laser gyro?

My thought, exactly!

I agree, when I was in college in the eighties, there were write-ups in technical journals using lasers properties for a gyro.

Hmmmm I thought this would be covered by relativity?

Surely as the light source is accelerating as well as the target the speed of light will, to the occupants, be the same speed as normal i.e. at rest. So no observable change in light level or direction would be measured.

Now if you used the light from an external stationary object then that would be different, you could measure the red shift etc... and get a decent measurement from that.

But in an enclosed system such as a space craft the light will always be at the speed of light inside the spacecraft....

Or would it?.... Where's Jorrie?

John.

"Surely as the light source is accelerating as well as the target the speed of light will, to the occupants, be the same speed as normal i.e. at rest. So no observable change in light level or direction would be measured."

true, true.

but if light from an external 'stationary' (I don't think that's possibly, as everything in space is moving relative to everyting else) is used, then you have THAT as your reference, which, by definition is excluded from the problem.

Also, by definition, if you are in an enclosed system with no reference to the exterior environment (assumeing there is no gravity, which, in itself would be a reference) then the ONLY way to know where YOU are is to have an observer tell you) You can not observe yourself, because anything you measure is only relative to your enclosed system. You MUST have an outside reference if you want to know your position relative to the outside world, whether it be gravity from a nearby star or planet or a light source.

AGAIN, have you never heard of celestial navigation???

You assume the speed of that light is altered by the travel of the space ship but is that true?

This would mean that ahead of the ship, the light will travel faster than light!

Go figure that?

I don't know where you're planning on going that ordinary navigation becomes impossible, but let's say you do. Just plug an accelerometer and gyro into your ship's computer and let it keep track.

That is called INS (Inertial guidance system). Original systems used a mechanical gyroscope. You need to account for precession with these systems.

To all that replied so far.

Yes and no. This is not basically a laser gyro apart from the fact I intend to use a laser as each directional beam. The laser gyro measures the interference of the 2 beams when they come together. This interference changes as the directions change. I don't exactly understand how but there seems to be a shift of phase when the 2 beams hit each other at different angles or times.

My system just measures the amount of light. The advantage of this would be, if it works, that it does not rely on this interference and therefor will not need compensation from what is known as "slow gyro lock". I am afraid I cannot even start to explain what that is but it seems to bugger the thing up at slow changes of direction so that you need to constantly change the pitch of the beam by turning it. This increases the mechanical parts and therefor makes it more vulnerable to breakdown.

With regards to the speed of light, I always learned it was constant no matter what. Now this is also my concern as if this was true, we maybe could not see the redshift as such. This, as we all know, detremines the speed of stars away or towards us as the light changes frequency due to the traveling source, a bit like dopler but then for light. I am just curious if this effect would undo my principle. I still think it could work but maybe we need more than one measuring point. If the redshift is not detected because the source is changing speed the same rate as the receiver disc, we need a longer distance tube, with repeated multiple receivers. This way we would be able to tell that one or more sets of discs are "out of phase" with the source.

You are right, we need Jorrie.

Not challenging your idea, but have you done any back-of-envelope stuff about what time differences you'd be trying to detect (ignoring relativistic stuff for the moment, and assuming there is a measurable change)?

Absolutely not, this is a discussion forum right?

Anyone who wants to disprove my idea better come up with the hard calcs

Only kidding, I am painfully aware that we are talking about many digits behind the decimal here with regards to the time measurement. I am also aware that, even if you are on top of all the technologies, you could still find yourself chewing "old hat" when it comes to electronics as they improve specs every minute of the day. In other words I am just hoping that by the time we are done arguing, they would have something on the shelf that can measure a trillionth of a second (unless we make a spaceship that is 200000 miles long and we could do it in a second (that calc is almost correct by the way))

Ever hear of a concept called "celestial navigation?" Every ICBM uses it!

We are now bound where no man has ever gone before, the unknown universe!

That much should have been clear

I know we should not make assumptions but you have my permission on this occasion.

Are you sure that is correct?

Celestial navigation will take you anywhere in the galaxy that you want to go.

But I'm still in my front room spherical trig and Celestial navigation give direction but no push. Beam me up Scotty I'm no longer intelligent life.

Brad

Laser Gyro, or laser ring gyro?

as in the this one.. http://www.nsd.es.northropgrumman.com/Automated/products/LTN-92.html

or

http://everything2.com/index.pl?node=Ring%20laser%20gyro

[quote]

A ring laser gyro is a device for measuring acceleration in a particular plane. The notable characteristic of the RLG is that it contains no moving parts, unlike early gyroscopic measuring devices which contain a surfeit of them. It works using techniques that are, to me, effing magic; however, they work, and are wicked cool besides, and they allow us to make solid-state INS systems.

[/quote]

There is your acceleration in 3-space and you'd use Stellar Cartography for plotting your course, with multiple cameras pointed at known references in the sky to triangulate your position, I think the Deep Space probes use this, Voyager and others ;o)

You could lengthen your tube by reflecting your laser back and forth from end to end. say mm steps till it lands on the receiver. Some effects would stay the same others would be amplified. Mirror absorption would limit your # of reflections.

2 more cents from

Brad

What about an odometer and an altimeter? I have gone this far and I am this high up. I think it's time we put on the kettle, what do you think Tensing?

Or he could just get out the Swiss Army knife and make a mark on trees periodically. Then he could, at least, find his way back.

Assuming you know your starting poimt, direction and delta Vee are easily determined using a simple household gyrescope. The sainted Admiral Robert Heinlein explains it in (IIRC) Destination: Moon, which I read at the ripe old age of 8. OK, I exaggerate a little. He wasn't REALLY an Admiral, and I may actually have been 9.

It sounds like a good one for 'Jorrie'.

Hi case491.

The easy way would be by taking the compass points of two relatively near objects in space and working it out by geometry or trigonometry. If after the first sighting is logged and a second sighting is taken after an hour, it would be a simple deduction using maths???

Spencer.

We do have other movements and speeds as well. Each object moves around and this creates absolute speed and relative speed depending where you are observing from. This would mean that you need to know this absolute movement before you could deduct your relative movement from this object to calculate your position. If we are in our universe fine. If we are neer the edge of the hubble field not so good.

We need something that is absolute all the time.

What you've invented is a variant of an Inertial Navigation System.

The basic working principal of an INS is that of a a spring-mounted mass: when the vehicle it's mounted in accelerates, the mass, because of its inertia, initially remains where it was (i.e. continues travelling at its original velocity). The displacement from its resting position is a measure of the acceleration of the mass's container.

A pair of such devices can measure the relative acceleration between the two (so long as the acceleration is perpendicular to the axis joining the two devices). The average acceleration of the two devices yields the linear acceleration; the difference yields the acceleration of one with respect to the other - taking the distance between them into account the rotational acceleration can be calculated.

Gyroscopes are another tool used to measure change, and rate of change, of heading (because they conveniently stay pointed in a constant direction).

Modern high-tech "gyroscopes" use laser light running through a circular fibre-optic tube, instead of moving mechanical parts. I suspect that they work on the very principle that you propose: when an optical "gyrosocpe" rotates, the light takes a little more, or less, time to reach a sensor - thus indicating the rotational speed of the loop.

Chris

Spring mounted masses are heavily dependend and/or influenced by gravity.

They do not work in both conditions. Due to this it also does not quantify the change of movement as it differs under a different gravitational field. It has to be calibrated for all possibilities which is a bit unpractical.

I already mentioned the short coming of the laser gyro. See above somewhere.

How's about super cooled conductor levitation?

Case491 was inquiring in and for comments. As I see it, many argue or suggest INS, and don't see much in the way of direct remarks as to his idea.

As I see it, there is a concept, maybe something I too thought about a long time ago. But when it comes to space travel, distance becomes an issue. At some point, despite placing certain "receivers" around our earth, they will tend to become rather finite and unusable (start with geometry). The position suffers the same difficulty. At least that's where our technology is today. In others words, and insofar as distance, the sender/spacecraft would only have +/- some uuMeter differential time differentials to extrapolate to determining distance and speed. Remember the term resolution. Technology today is limited for the time being.

On your reference of light: even with utilzing coherent light, as laser, transmitting back into space will diffuse. Otherwise, we are not there yet or maybe never will be. But (below):

One day, we will achieve, but likely on another plane of science for many theories as they may or not be now.

It is good that some of us think. Every once in a while, an idea could develop into an actual and viable concept. Given success, the inspirer should receive appropriate credit! Let's remember that!

I don't think you will see any increase or decrease in intensity by accelerating. The speed of light is a constant. If, for example, you go in a direction at 1/2 c, and shine a light in front of you, the speed of the light in front will still be c, and not c + 1/2 c.

As long as the tubes are in your inertial frame, the speed, intensity, and frequency should remain constant as far as you can determine.

Good morning vermin.

There is another problem which has as yet not made itself known in this blogg.

The latest discoveries are that the speed of light might not be constant!!!

Spencer.

Here you undo yourself dear vermin, I am not talking about the light speed changing but the receiver speed changing! This is a big difference.

As the light source is spewing light out at the same rate per second and this light is traveling at the same rate per second, surely a moving receiver at the other end of the tube should see a variation in received light per second.

Once the light has left the source( point in time we call time A)it travels at set speed and should receive the receiver disc at set time, let's call that time B.

While the light is traveling I am now going to speed up the tube and the disc is therefor moving faster away from the source. As the time it should have taken for the light to reach the disc is known, it concludes that after acceleration the receiver sees less light for the time frame where it should have received the light transmitted at point A. Therefor point time B is seeing less light as it is still traveling. It follows that in time point C, after deceleration again, the light that was "missing" from the receiver as it was speeding away from the source, gets received again which tells you about the deceleration, just as the missing light tells you about the acceleration.

This is the core of my theory and the principle of this device. If you accept that light travels at a set speed (till now not proven untrue, only speculated at) you have to accept that, as long as we can measure the small time amounts and small difference in light amounts, we can use this as a measure of accelaration and change of direction with far more accuracy and reliability than is possible with any known device in existence now.

If the gravity wave detectors get built this will be something they will have to account for as a matter of data collection.

If I understand the process correctly. Lasers I understand well, gravity especially at velocity .

Brad

I don't think there's any getting around the law. Your tube will undergo a Lorentz contraction in the direction of motion. I think this may cancel your proposed phenomenon out.

I still think we should have Jorrie check this... Hey, Jorrie!!!

Oh, and by the way... "Here you undo yourself dear vermin,"

What the heck is that all about?!

Oh, and by the way... "Here you undo yourself dear vermin,"

He's wrong of course. A vermin, once done, can never be undone.

Hi C491,

Sorry, I missed this one. I've only scanned through the all the replies and maybe I missed someone that should take the credit for what I'm going to contribute, but here goes.

Yes, this device as you described could work, but very inaccurately, I'm afraid. You effectively get a Doppler shift between the emitter and the receiver in the direction of acceleration, proportional to the change in spaceship speed during the light travel time multiplied by the length of the tube. This boils down to a fractional Doppler shift in wavelength, proportional to the acceleration, a, multiplied by the distance between emitter and receiver, L, of:

Δλ/λ = a L/c², with relativistic precision.

Plug in reasonable values like a = 20 m/s² and L = 100m and you get Δλ/λ = 2 x 10^-14, which is perhaps a tad small to measure accurately. That's why interferometers are used in practice.

To measure the amount of light falling on the detector, as you suggested, is even worse - it also depends on the tiny Doppler shift and how do you quantify the differences?

Jorrie

The truth shall set us free...

Thanks, Jorrie!

Thank you Jorrie, With regards to accuracy, will that perhaps get better with future technologies?

It is just down to the small difference and as said, that is sooooo small it is almost unmeasurable. Maybe in the future they will come up with some sensor that can in fact quantify all these small units and translate the lot into useable data.

Anyway, thanks for confirming it will work theoretically. They can quote wikipedia but they cannot take away the product of a great mind.

How about trying to redesign your device using interference (as per the laser gyro) for detection? I don't know if this is possible within the known constraints of relativity theory - perhaps Jorrie could advise () ?

Hi John, you asked: "How about trying to redesign your device using interference (as per the laser gyro ...?)"

No, I don't think interferometry will work well for accelerometers, because you need a two-way light signal to interfere with another coherent (normally orthogonal) two-way signal. For constant acceleration, the phase shifts will tend to cancel out. The laser accelerometer uses suspended masses with optical patterns on them and their movements under acceleration are measured by means of laser light.

Jorrie

http://en.wikipedia.org/wiki/Laser_accelerometer

case491,

I really gave this some thought... Could you pick a frequency where a 2 X 10^-14 power could be identified, but no matter what frequency I chose (even microwave) 2 X 10^-14 power just isn't observable. Let's hope that someday (as you say) this may be detectable.

Hi Vermin,

Isnt there a thing that measures the "amount" of light such as lux or lumen? If we could bring the sensed quantity to be dependend on a time period, it follows that the figure should temprarily alter due to the dopler shift.

Again the absolute difference will be small and may be too small for modern sensors to be picked up.

Still nice to see that in theory it is workable, all we need is better equipment

Well, the visible spectrum is about 400nm to 800nm. I don't think there's a diffraction grating or optical flat or interference generating system that could detect a 2X10^-14 change in the length of a few billionths of a meter.

At the microwave range, the waves are much longer, but I think the problem is the same in that the measuring equipment is incapable of detecting a 2 X 10^-14 change is say a 20 centimeter wavelength.

But it still must feel good to know that you got it right, at least in principle!

Hi Del,

What did your diffraction grate look like?

A B C D

a) You probably had 3 pints that night and did retrieve the keys but they looked like 3 sets.

b) You probably did drop the keys after 5 pints but you had to pick which of the 3 grates they fell in. Subsequently you were very relieved to find them right next to all 3 grates as they had just missed it.

c) You drank 7 pints and you did not drop them at all. You just were so late back that night that you made the story up of how you lost your keys in the first place , hoping Mrs Cat would believe you and be gentle on you.

d) Don't tell Mrs Cat you dropped them in that one as that one is in London Town and you told her you were in your friends local on the other side of Harlow.

I feel sorry for you Del, living in your perpetually confused state must be difficult at times.

Hahahahahaha!!!

"I feel sorry for you Del, living in your perpetually confused state must be difficult at times. "

Difficult? Yea, ask Schrödinger's cat - it had live not only in confused states, but also in a superposition of states...

I understood the cat was only observed when viewed. At other times the math suggested he was quite sublime.

cr3

I the meantime, while all the physicists were arguing, the cat was thinking. "GET ME OUTTA HERE!!!"

OR - it was the grate outside the pub, and not only did he retrieve his own keys, but the keys of two other poor sods, as well.

Maybe one of the other sets was stinky pete's!

Hey Pete, you can go back to your proper home man, just ask Del for the keys.

Stop it!!! You're driving me sane!!! - Peter Lorre

The only concern I have is this device need line of sight. So the receiver and transmitter need to point at each other all the time. The further away they're, the more difficult it will be. Also how do you reconnect them after the signal is lost? Say something fly between and blocked the light for a while. How about gravitational effect on the light? Like bending it so you get incorrect reading?

Providing the receiver can pickup the signal from all the background lights.

Pineapple

This is assuming that the Tx is at a point in space and the Rx is the ship flying away.

Unfortunatly, the original question said, "without a reference from a known object" so having the Tx outside the craft, this would be a "known reference"..

Having the Tx-Rx in the ship itself, then you would be using Doppler (as stated above) and then the red/blue shift would give your Accel/Decel, if something come in between, you may have a problem of a hull breach, or bend, or hand, or a critter taking up residence in the wrong place ;o)