Propulsion Isn't Just Everything, It's The Only Thing

spacedaily ^ | 6 Nov 01 | Rick Fleeter

[tim politicus]

Squeeeeeek!

[boris]

You'd fail the exam.

Hint: the failure of this classic argument is "equivocation".

--Boris

[mercy]

I don't know about the arguement you pose. Have you heard of this one? An animal brain evolved such as we may suspect we have and indeed have some evedence bespeeking such evolution, could not concieve of something beyond animal evolution. There would be no evolutionalry force to fire such 'thinking'. Therefore the near universal proclivity exhibited by man in postulating spiritual beings and spiritual existence is not of this world. It is wholly unnatural and at least evidence for implantation of such thinking from an 'outside force'.

[AFreeBird]

bump for later read

[aruanan]

Thanks for an interesting read. Where does something like cubane fit in in power yields between nuclear and ordinary chemical rockets? Could it employ the same technology as the nuclear-pulse driven ships?

[tim politicus]

Thank you for the reply. Please do tell me where you think either I or Anselm are being equivocal in our ***meaning***. Also, did you read what I wrote? Do you have any thoughts about it other then, "failed"?

_Any_ argument can be deconstructed by construing its terms as being equivocal. Perhaps you _intend_ the terms of the argument to be equivocal.

But neither I nor Anselm, who's argument it is, do so. We have an exact and consistent meaning for each of the terms.

boris, would you deal with a technical question or dispute you had with a colleague by launching unlistening assertions at him or would you sit down and actually try to reason, to discuss the issue with him. I'm not saying that you or I are acting unreasonably toward one another, but I fear that unless we move towards more directly addressing what each other is ***saying*** that we will mearly be talking at or past one another.

Isn't all language equivocal? But meaning is not. I think if you understand my and Anselm's ***meaning*** you will see that we are not, even though some textbooks say otherwise, being equivocal.

[tim politicus]

I was thinking the exact same thing.

A linear accelerator of any sort would seem to me to be essential. A "gun" of some type would, in fact, work, if the propellant reaction could be tightly controlled, that is, slowed down enough.

I'm thinking of a reaction more like one gets when shaking a bottle of soda pop or a child's mixing of vinegar and sodium bicarbonate. If contained in a long enough vessel, or "gun", the chemical reaction could, I think, accelerate gradually enough.

I'd imagine a complex computer control of the entire chemical event-- alternatively dampening or boosting the strength of the reaction based upon realtime measurment ***and computer modeling*** of the reaction [and where it is heading]. The problem is designing an entirely new technology. Or has this been done already? boris, would know.

[freefly]

Good reading in this thread.
We have some SHARP people on FR!

[mrsmith]

An adjunct to the "propulsion is the only thing" argument:
I wonder how much the "risk" of advances in propulsion deters investors?

Present schemes for space profit envision 20 to 30 year payoff periods.
Any project built at 10k per KG wouldn't be able to compete against one built at say, 1k per kg.

An intra-solar nuclear rocket is an all-around good idea.

[boris]

"Whatever became of the space 'gun',i.e. a long barreled artillary piece capable of firing projectiles into LEO."

A fellow named Bull was a big advocate of this. He also was a large gun expert and went so far as to sell his services to the highest bidder--in this case Saddam Hussein, who tried to build a "Super Gun" up the side of a mountain with a fixed point of aim: Tel Aviv.

So, a fellow walked up to Mr. Bull as he was putting his key in the lock of his home, placed a .32 caliber gun against his medulla oblongata, and blew his brains out. Ironic, that, such a small caliber. Everyone knows it was the Mossad's doing, but nobody will admit it. Big surprise.

Any way, a big gun could launch small, high-gee-resistant payloads "almost" to low orbit. You'd need a small rocket to circularize.

I saw a proposal for a "light gas gun" (using helium or hydrogen). One proposal was: dig a hole into the ground, and a big spherical chamber at the bottom. Put an atomic bomb in the chamber; fill the entire thing with helium, and close the hole with a freely-sliding piston. Put heavy payloads on top of the piston, like pig iron, glass, any cheap stuff you want in orbit and which you don't care how comfortable it feels while getting there. Dirt. Congressmen. You know, that sort of cargo.

BOOM!

--Boris

[RightWhale]

Present schemes for space profit envision 20 to 30 year payoff periods.

I would call them business plans rather than schemes, but your estimate of time to payoff is reasonable. First delivery of material mined from asteroids would be 20 years from project start if all goes well. Would your credit union would be interested?

[RightWhale]

oh nevermind, you wouldn't believe me anyway

What's the plan? Lay it on us. Pretend we are potential investors.

[RightWhale]

A linear accelerator of any sort would seem to me to be essential. A "gun" of some type would, in fact, work,

Rail guns have won the race for preferred launcher from the moon. Once an appropriate critical mass of our act has been placed in space the rate of space development should accelerate so rapidly that mid-level government space planners would want to throw their white papers into the back of the third drawer down of the file cabinet and finish the career mastering Civilization III.

[mrsmith]

LOL! My bad, my very, very bad!

It is because of your intense interest in space commercialization that I hoped you would have some insight into how investors viewed the "risk" of improved propulsion!
And yet I used an obvious "hot-button" word like like "scheme" :-(

[tim politicus]

Yes I agree, if the process can only be "jump-started" it will eventually grow exponentially of its own momentum. The problem is that darn HUGE startup. The first investrors in both the Panama canal and English colonies in North America lost everything, I think. But once there are accelerators like that in LEO or the moon or in-between...

What really attracted my attention on this thread is a lot of what boris and others were saying about the astronomically (ha ha) better efficiency of chemical over 'electromagnetic propulsion. That got me thinking about railguns as well. Darn problem is the limited acceleration time, even with a vast system.

Are railguns or guns of any significant use at all beyond about a lunar orbit?

To me all what this shows is that it is going to take _a lot_ of work and time and organization and inspiration to get where we need to go. I'd think we need some cultural and social changes before we could pull much of this off.

[UnChained]

Looking at the way the universe is designed, it almost seems to have been deliberately arranged to prevent interstellar travel and interactions between (presumed) intelligent species...

Once upon a time, I was waching the JPL animation "Mars the Movie" and I had a striking revelation. I realized that watching that animation was as close to exploring Mars as I was ever going to get. In many respects it was better that really being in a spaceship and making the flight in person. I was able to fly through the Valis Marinaris trench at 200,000 miles per hour making high G force manuevers that would had killed me and destroyed my ship.

I saw a similar movie of a flyover of Venus' terrain and that settled it. Venus is covered with clouds. If I were to actually go to Venus I would be forced to view the surface on computer screens that display images built up using data from my spaceship's synthetic aperture radar as it peered through the hot dark sulphuric acid atmosphere.

In "Venus the Movie" I was able to experience the same thing minus the G forces.

If I were to travel to a typical nebula and look at it with my naked eyes through a window, a lot of detail would be too faint to see. I would need some sort of image intensification and would get my best view of it by looking at a computer screen. There are computer flythroughs now of the Orion Nebula. That's 3600 LY away!! How many lifetimes would it take to travel there? And, once I was there, why did I bother? I get my best view of it looking at a data set on a computer.

Unless we develop a way to wherever we want to go instantly, we will never be able to explore much of the universe by physical space travel. Space is just too big. Most science fiction has people tooling around in the Milky Way galaxy. There are billions of galaxies visible to us though. Those galaxies are seperated by distances that even fantasy writers don't want to cross.

It's inevitable\ that most space exploration will be done by telescope. There's no way around it. We will always be able to see farther that we can physically reach. But that's actually good enough. Why should we go to another star? You can't touch it, you can't even look at it.

It all boils down to this:

What we are doing now is about as good as it gets.

I always looked forward to a time when mankind would build a vast fleet of spacecraft and we would really get down to the business of space exploration. The future is now. We ARE exploring the universe. It won't be much different than now. We can travel faster and farther by building better telescopes. Faster than light travel won't take us to the distant galaxies we see. If there is an inteligent life in any neighboring star systems, we will be able to count the suckers on their hands by looking at them from earth long before we could travel there.

[UnChained]

Interstellar travel doesn't make much sense to me. But travel within the solar system would be pretty cool. It would be possible to commercialize space if there were a way to cheaply get to low earth orbit. I'd love to see that topic discussed . I have an idea that I need to get shot down by someone who knows physics better than me. New thread perhaps? Or somewhere besides FR?

[IronJack]

Generally agree with you Ill, but this time, I gotta take an exception. Sure, Columbus was motivated by greed -- the Northwest Passage and all that hooey -- but even if he hadn't, even if the dollar had never been invented, someone still would have struck out for foreign shores.

Man's spirit is restless, and our sole reason for living seems to be to push back boundaries.

"That a man's reach exceed his grasp, else what's a Heaven for?"

[tim politicus]

An earth gun shooting a reverse meteor. A great idea because you get the power of nuclear reactions while leaving the dirty part underground!

But what about deceleration or guidance of the payload? It seems it might take as a very large amount of energy to "catch".

Why not a long ‘slow’ burn? [Would it have to be directed at the horizon?] The channel tunnel and some others might show the basic tech. Perhaps you could get pretty vertical using a mountain. What are the theoretical lower limits on the size of nuclear explosives? If they are concieved as able to drive pistons, perhaps eventually a series of these pistons tangent to, and feeding a long linear tunnel system could drive a payload at least as well as current rockets, nuclearly, while leaving the mess below.

If such a system could develop with enough tolerance in the system, then there may be no limit to how far it could be built horizontally. I think you could get a good head of steam after a couple hundered miles or so. Could a limit be the atmospheric friction?