A Conversation for The Bussard Ramjet - an Interstellar Drive?

factual error

Post 1

xyroth

Although you might be right about the use of deutirium making these drives inefficient, in practice, you would use tritium (h3) instead. this can be mined on the lunar surface, or collected using magentic fields inspace, and is a significant fraction of the solar wind.

tritium is much more efficient, and thus makes some of your conclusions based upon the inefficiency of deutirium unlikely.


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Post 2

Hoovooloo

I think this is in danger of being one of those "angels on the head of a pin" conversations...

You could mine tritium on the lunar surface - but the whole point of the ramscoop is you don't carry your fuel with you, you scoop it up as you go along.

And the fact that the solar wind is rich in the stuff isn't much help in interstellar space where this kind of drive is really useful. In where there's enough tritium to make it concentrated enough to be worth separating from the deuterium, let alone the hydrogen, wouldn't you be better off just using a solar sail?

I think I did mention that the objections based on efficiency of deuterium reactions could, in a century or two, sound like the musings of the IBM chairman in 1947 who speculated that there may, one day, be a world market for as many as four or five computers. We couldn't build one now for all sorts of reasons, theoretical and practical. But by the time our practical methods have improved, the theories may have moved on too to the point where something close to the scoop is possible.

smiley - offtopicHow much tritium is there on the lunar surface? Would it be worth mining for power generation for a base?

H.
thanks for reading!
smiley - cheers


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Post 3

xyroth

I have heard talk bout doing exactly that.


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Post 4

Scottish Guy

I'm still hoping for a warp drive, or worm holes at the very least. And they'd better hurry up with the cryonic suspension too! I'm not that keen on teleportation though, unless the physics involved mean that it's actually >me< that gets teleported, and not just some duplicate that calls itself me. The future lies in the very fabric of space (possibly dennim). It's all to do with quantum you see.


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Post 5

Hoovooloo

"Eddies in the space-time continuum"
"And this is his sofa, is it?"

H.


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Post 6

xyroth

there are a whole host of "space-time irrelevance" drives allowed by physics. Warp drive has recently become a lot closer to reality, by finding a short cut which droped 10^60 of the energy needed for it to work. still too expensive of energy though.

The basic idea of all of these space-time irrelevance drives is that pushing something through space-time is very expensive, so if you can find a way of avoiding having to do so, things suddenly become much easier.

There area lot of people who hope that due to the current lack of knowledge about gravity fields, it might be possible to manipulate them in some way, so that you are actually moving past the normal field, rather than through it.

wormholes are also possible, but again it is the energy budget that is the problem.


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Post 7

Scottish Guy

It would need some way to suck in hydrogen from ahead of it and expell it forwards, or deploy an ionised gas bubble or solar sail to increase drag and slow it down. What's the maximum speed of a Buzzard ram-jet, and what is the time dialation factor at that speed? If it was combined with cryonic suspension technology, could it be used to cross the inter-galactic gulf, even the universe itself?


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Post 8

Hoovooloo

There's no theoretical limit to the speed of a Bussard ramjet, other than lightspeed. I could go on at great length about the fact that you don't need to bother with cryonics, as time dilation does all that for you, but at the risk of repeating myself, go out, tomorrow, and buy "Tau Zero" by Poul Anderson. It will answer all those questions, a few you didn't mention, is a cracking read and undoubtedly one of the top sf stories of all time.

Go to it!
(and thanks for reading/asking) smiley - cheers
H.


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Post 9

Mookie- thingite arbiter of infinite wisdom and justice

Is it fision or fusion that cant be reproduced? other than that while the pilot may age 20 years the rest of the universe will age the full amount of time which means that it would only be useful for colonization or transport of thing that grow more valuable with time (wine, books, art....). and it might be that technological advances will have rendered everything obsolete by the time it arrived anyway. a fairly common scifi theme isnt it?


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Post 10

Hoovooloo

Not sure what you mean by "reproduced"?

Fission is what happened at Hiroshima and in every nuclear power station in the world.

Fusion is what happened at Bikini atoll, in the sun and every other star in the sky, in hugely expensive, complicated and inefficient toruses in research labs around the world and as far as I'm able to tell NOT in a test tube belonging to Fleischmann and Pons in 1989.

Both reactions are "very easy" to reproduce, where "very easy" means it only requires the military industrial complex of a major developed country working for about a decade to achieve it reliably.

Absolutely correct, ramjets are no good for round trips - you go and you'd better be damn sure where you're going is hospitable because you're not coming back. See most of Larry Niven's "Known Space" stories, especially "Rammer", "A World Out of Time", "Protector", and "Tau Zero" by Poul Anderson for sf takes on this. "A World Out of Time" in particular envisages a ramjet pilot going to the centre of the galaxy, then returning to a shattered and almost sterile earth, MILLIONS of years after his birth, after less than 100 years of his own subjective time.

smiley - cheers Thanks for reading! (btw, how did you find this?)

H.


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Post 11

Mookie- thingite arbiter of infinite wisdom and justice

was that "how did you find this?" directed at me? and by reproducable i mean able to be controlled when it happens


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Post 12

xyroth

a common mistake that has just been made here is to say that cold fussion doesn't work.

While strictly speaking this is true, as most people use it, it is false. The cold fusion experiments have proved that they are highly sensitive to initial conditions (hence the number of labs that couldn't get any energy out), that you don't get any extra energy out if you put it ina properly shielded radiation laboratory, and that you get a lot of extra energy out if you can get it set up right.

So while it isn't fussion (else it would probably work in the shielded lab), it does produce excess energy.


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