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**KrazyHorse** · November 23, 2001, 01:15

Originally posted by GP
I don't see why the fundamental thrust equations make a launch rocket require multiple stages. Essentially the lighter you can make the fuel container, the less you need multiple stages. The issue here is fuel container weight, no?

Right. The fuel mass itself is what causes the the diminishing returns of additional fuel.

**TCO** · November 23, 2001, 01:34

Comments on the Orion document?

**KrazyHorse** · November 23, 2001, 01:55

Just read it. I don't know; first off, I have no idea how you'd build a 0.1 kT fission bomb. Secondly, I'm really surprised the pusher platewould withstand hundreds of detonations of size ~20 kT. Third, I wouldn't advocate launching a rocket using nuke explosions; this sounds sort of wacko. Maybe a few flights would be okay using this method, but it doesn't sound like a long term solution. Fourth, given that the chances of a catastrophic failure of any launch vehicle in existence is ~1/50, it seems sort of crazy to put...umm...~500 lbs of fissile material on board such a lunch vehicle. I really don't know what the impact would be on Earth. Would the module containing the bombs be left intact or scattered for a couple of thousand miles along its flight path?

That being said, it's worthy of furthe study at least. Dyson is sort of known as an incurable blue-sky optimist isn't he?

**Ramo** · November 23, 2001, 01:56

If the photon is absorbed rather than reflected all the energy is maintained on the craft, as well as imparting an impulse. If you have a solar cell absorbing the laser for powering the craft then you kill two birds with one stone. You power the craft and you propel the craft.

Ermmm.. how does that work? This kind of engine can't be too accurate (or effective). I suppose you need some trippy mirror design..

**KrazyHorse** · November 23, 2001, 01:59

Why not accurate? Thrust from this sort of thing is really low, though. Really low.

The have some really light reflective materials around. Stuff that will float on the air currents in a room.

**Ramo** · November 23, 2001, 02:05

Like what?

I was thinking that the impuse on the reflective materials would defeat the purpose of the impulse on the solar cell.

**KrazyHorse** · November 23, 2001, 02:07

Can't remember whast materials they were. Something's telling me they're really thin aluminum alloy sheets.

What do you mean by your second comment?

**Ramo** · November 23, 2001, 02:15

Well, you have these changes in momentum due to impulses on a certain area of the solar cell (I assume basically the entire surface of the shuttle would be solar cells), as well as the impulse on these aluminum alloy sheets. Seems like there would always be a significant error...

Hmmm.. I suppose it might work, but it would be one helluvan engineering problem.

**KrazyHorse** · November 23, 2001, 02:25

I think you have a central section "painted black"

with solar cells to get power+half thrust (thrust in direction of photon, no "tacking" possible) surrounded by mirror which gets full thrust (depending on which direction you want to tack in, thrust normal to surface of mirror).

We're thinking BIG. Square kilometers of sail.

**Rogan Josh** · November 23, 2001, 06:36

To shift topic a little it, I think it is all a matter of budget. I mean, I am sure we would all like to see enough money going to a complete and comprehensive Space Program, but since the US govt has a very limited budget for science spending what is it instead of?

For example, you may recall that the SSC (Superconducting Super-Collider) was being built in Texas -- they had dug 100's of miles of tunnel for it and everything -- when it was canceled for political reasons. This project would have provided as many spin-offs as any NASA project (remember one of the spin-offs of LEP in Geneva, was the WWW), but even more importantly it would have switched on last February. So now we would have probed energy scales up to 40 TeV (

) and would know why particles have masses, what symetries the laws of the Universe has, whether or not there are large extra-dimensions in our universe, and have hints towards Grand Unified Theories, String Theories and M-Theories.

So if you are really looking to back these NASA projects, ask first what you are throwing away to provide for them.

**Dauphin** · November 23, 2001, 07:39

Plus, this could just be taken as ***-for-tat

Thats the problem, we both have egos. Obviously I scored a hit, else KH wouldn't have been compelled to counter

On the technical matter:

You have to pitch at the right level.

Make it complicated and technical and some people look

.

Make it nice and simple and some people will "

That's not technically correct!"

**KrazyHorse** · November 23, 2001, 08:22

Originally posted by Big Crunch

Plus, this could just be taken as ***-for-tat

Thats the problem, we both have egos. Obviously I scored a hit, else KH wouldn't have been compelled to counter

Actually, you didn't. Your assignment now is to provide a semantic analysis of the phrase "as far as", noting most importantly whether this phrase gives any indication to direction or not.

**Dauphin** · November 23, 2001, 08:27

You mean you are tatting me for nothing?

Thanx for letting me now what injured you ego.

**KrazyHorse** · November 23, 2001, 08:30

Originally posted by Big Crunch
You mean you are tatting me for nothing?

Thanx for letting me now what injured you ego.

I like tatting.

**Dauphin** · November 23, 2001, 08:32

I prefer titting.

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