27-11-2001 00:40									#181
	Support Apolyton, buy Civilization III: Complete

Interesting.

3000m/s is very slow. Are you sure, Krazy? a bullet moves at 3000 m/s. And 4% energy loss would be noticeable as a color shift. That implies I could easily construct some sort of apparatus at home to show light dopplering. Should we make it a design project for physics freshmen?

Does the energy transfer approach 50% or 100% as I move towards c? If I'm at 300,000 m/s what percent of photon energy is transferred?

	27-11-2001 00:43									#182
	Support Apolyton, buy Galactic Civilizations: Deluxe Edition

Crap! I mixed up meters and kilometers!

F*ck, why didn't anybody point it out?

I'd require 3000 km/s to do what I said.

So, assuming (more realistically) a speed of ~30 000 m/s, we'd get 0.04% power loss on each bounce. Therefore, it takes...

720 bounces for 25% power loss.

And yes, given v = 3*10^8, we get 100% loss on a single bounce.

	27-11-2001 00:50									#183
	Support Apolyton, buy Galactic Civilizations

Krazy, it doesn't add up.

You said within the clasical range the energy transfer is proportional to v. If I go to 300,000m/s (still well in the classical regime) I should get 400% energy transfer.

	27-11-2001 00:54									#184
	Support Apolyton, buy Alpha Centauri

Classical = non-relativistic.

I already mentioned this earlier in the thread

quote: Note that we can see why the constraints are necessary, since for v/c > 0.25 we have that the photon descends into a negative energy state with this approximation, and for v=0 we get "something for nothing" as the photon does not lose energy in the process

	27-11-2001 00:55									#185
	Support Apolyton or Terrorists Win

errr...I think I did.

(nice editing by the way.)

I had this really nice college physics demonstration figured out using a revolver, silver tipped bullets, a laser and a highspeed camera. You set it all up on a table to make sure that the laser beam intersects the bullet path and that the camera can get the bounce. Then You have the students look at the images colors to see visible doppler shift of light.

	27-11-2001 00:56									#186
	Support Apolyton, buy Call to Power 2

quote: Crap! I mixed up meters and kilometers!

KH, I'm dissapointed in you.

	27-11-2001 01:02									#187
	Got spare money?

quote: Originally posted by GP errr...I think I did. (nice editing by the way.) I had this really nice college physics demonstration figured out using a revolver, silver tipped bullets, a laser and a highspeed camera. You set it all up on a table to make sure that the laser beam intersects the bullet path and that the camera can get the bounce. Then You have the students look at the images colors to see visible doppler shift of light.

Are you sure you aren't just trying to kill werewolves?

	27-11-2001 01:02									#188
	Support Apolyton, buy Galactic Civilizations

quote: Originally posted by KrazyHorse Classical = non-relativistic. I already mentioned this earlier in the thread

Gotcha...my comment was made before you editted in the correction.

	27-11-2001 01:05									#189
	Support Apolyton, buy Galactic Civilizations

DP

	27-11-2001 01:05									#190
	Suffering from ads?

Huh? I didn't edit anything.

Unless you're trying to cover up your lack of reading skills...

	27-11-2001 01:11									#191
	Put an end to popups!

I thought you had a post in the 1453 slot that said "all of it". That you then edited to put in the correction.

Anyway. My comments were made using your earlier 3000m/s. The new figures seem to make more sense. If 3 *10^6 gives 4% than 100 times that is light speed and is 400%. So you start climbing up the wall, where you'd expect.

	27-11-2001 01:18									#192
	Got spare money?

Oh, that...

The "all of it" referred to your question regarding what happened at c

	27-11-2001 01:27									#193
	Get a bigger avatar today!

Anyways....moving along now.

Let's say that the craft is moving at KH's speed that gives us 720 bounces to get 25% energy conversion.

And lets say that the craft is the distance from the moon to the Earth. (could be a lot farther, right?) That is 3 light-seconds right. That means that the photon takes 36 minutes to do its work.

I really wonder if you can keep that kind of optical precision given: The changing geometry, keeping the mirrors rigid (especially the one on the craft), and physical imperfections on the mirror surfaces (even at the atomic level).

	27-11-2001 01:34									#194
	Suffering from ads?

Why does the geometry of the craft's mirrors have to be non-dynamic?

	27-11-2001 01:49									#195
	Support Apolyton

looking at it another way:

Assume the geometry issues (with keeping the beam "trained") are overcome (big ass assumption):

You just have problems of absorption and scattering. Let's assume space is a perfect vacuum (it's not) but let's say close enough so that the photon can cycle back and forth 720+ times without appreciable scatter on dust/hydrogen. (Needs to be checked but maybe a fair assumption.)

Then you just have the issue of mirror surface effects. If this is the major loss source than, you figure that means1440 bounces (two mirrors) gives you a loss of 75% of your photons. So about .5% of the energy is lost at each bounce. Or 99.5% is kept.

I think you can get a top-notch optical mirror may give you <.5% for diffuse scattering and absorption (need to check though...Krazy you cold ask some laser jocks what the loss factors are per mirror on their optical tables.) There's another form of loss that occurs becasue of beam spread after hitting the mirrors. You could ask the jocks about this, too Krazy. You need to keep that beam tight for a long ways...current laser would have issues there (without any mirrors...)

	27-11-2001 01:53									#196
	Browse Apolyton AD-FREE

quote: Originally posted by KrazyHorse Why does the geometry of the craft's mirrors have to be non-dynamic?

Oh it doesn't. I just figured it would be easier to have that kind of stuff kept on the ground station where you have people and rigid mounted arrays and micrometers and all that.

	27-11-2001 02:01									#197
	Remove this text

I think you will find this link topical, even if not wholly related

http://www.newscientist.com/news/news.jsp?id=ns99991603

quote: Artemis is located in a fixed, geostationary orbit 31,000 kilometres above the Earth, while SPOT 4 is travelling at 7000 metres per second at just 832 kilometres altitude. The laser link between the two is just a few metres wide.

	27-11-2001 02:05									#198
	Suffering from ads?

quote: Originally posted by GP There's another form of loss that occurs becasue of beam spread after hitting the mirrors

Why don't you use slightly concave mirrors that can change focal length?

	27-11-2001 02:09									#199
	Inflate your Upload Space

That's a very interesting link, BC.

	27-11-2001 02:13									#200
	Tired of ads?

quote: Originally posted by KrazyHorse Why don't you use slightly concave mirrors that can change focal length?

I guess you would. Would be interesting to think about the optics. What radius of curvature?

I think you still get some beam spread from the imperfections in the crystal surface, no?

	27-11-2001 02:17									#201
	Lose 30 kilos (of popups)

Yeah, but right now I really don't know what type of levels we're talking about.

Plus, has anbody else noticed that if you're reflecting those photons 720 times then you've got ~640 times the original beam intensity bouncing off these mirrors? That's a hell of a lot of energy, and any power loss whatsoever is going to be dangerous.

	27-11-2001 02:20									#202
	Browse Apolyton AD-FREE

quote: plus, has anbody else noticed that if you're reflecting those photons 720 times then you've got ~640 times the original beam intensity bouncing off these mirrors?

You wouldn't have the laser on 24/7.

	27-11-2001 02:24									#203
	Support Apolyton or Terrorists Win

No? You'd get more acceleration if you did, though.

	27-11-2001 02:32									#204
	Increase the size of your Attachments

Rephrase

You wouldn't need to have the laser on 24/7. If you started to have problems with the intensity of the beam you could the laser off.

I heard a suggestion of having a massive parabolic mirror on the craft (say a few hundred metres) and firing several hundred lasers at it. The explosive force on any object at the focal point would provide rapid acceleration to the craft.

	27-11-2001 02:46									#205
	Increase the size of your Attachments

Getting back to my baby...I could build that sucker for you. Just need some hard-working grad students, a patch of desert, heavy machine shop (Coors mining has a nice one) and few hundred small nukes and we could do it.

Anybody know some catalogs that have small nukes in them? Can't find them in McMastercar.

	27-11-2001 03:18									#206
	Put an end to popups!

Next time you're on a sub maybe you could swipe some.

	27-11-2001 03:19									#207
	Support Apolyton, buy Alpha Centauri

I just read something interesting from the JET propulsion labs in Pasadena.

At present technology we could send a 10kg satellite to Mars within ten days using lasers and solar sails. That shocked even me.

Also there was a comment on inter-stellar travel....

quote: A phased laser array we have designed to send a probe in 40 years to the nearby star Alpha Centauri would be 1,000 kilometers (621 miles) in diameter.

	27-11-2001 03:21									#208
	Help yourself to an AD-FREE life

quote: Originally posted by Big Crunch I just read something interesting from the JET propulsion labs in Pasadena

JPL iz 733t

	27-11-2001 03:49									#209
	Avatar Enlargement: We've got the solution

quote: Originally posted by KrazyHorse JPL iz 733t

You lost me.

	27-11-2001 14:23									#210
	Support Apolyton, buy Civilization: The Boardgame

Never mind...