Re: Self-contained interstellar vehicle
- From: "IsaacKuo" <mechdan@xxxxxxxxx>
- Date: 7 Nov 2005 08:20:11 -0800
Logan Kearsley wrote:
>Despite the advantages of bombtracks, magsails, lasersails,
>and other proposals that require home-system support or
>otherwise are only good for one trip before you need a
>whole industrial complex to relaunch... I don't
>like the fact that you need a whole industrial complex
>to re-launch.
With bombtrack propulsion, the bombbots required for
relaunch can be sent from the home system, and used
directly without a need for matching velocities.
Is that close enough?
>And so I have been pondering self-contained propulsion
>ideas that could still go reasonably fast.
>The biggest problem I know of with a standard bussard
>ramjet is that the maximum compression of the incoming
>protons is limited by the kinetic energy of the ship,
>or if we take the ship as the rest frame the kinetic
>energy of the incoming protons.
It's limited by the latter, not the former.
Think of the proton as a small bullet, and the ship as
a big elephant. The energy of the impact will be
roughly the kinetic energy of the bullet in the frame of
reference of the elephant, no matter how big and heavy
the elephant is.
But in any case, this isn't really the biggest problem.
It's a problem which can be "solved" by first getting
the ramjet up to a sufficient speed.
The big problem with a bussard ramjet is MAINTAINING
that speed. For that, you look at the balance of drag
vs thrust, and what the plausible losses would be.
>Without an on-board power source (or even with one,
>I suppose), we're going to want to cool (or otherwise
>remove energy from) the plasma a bit so that it can be
>further compressed to the point where it can fuse.
I don't see how that HELPS things at all. It seems to
be the exact opposite of what you want to do.
Compression alone doesn't get you fusion.
>Otherwise, maybe we can allow the plasma to be
>compressed a little bit by moving through the
>ramscoop, converting kinetic energy into heat as usual,
>up to the point where there is just a enough heat energy
>left in the plasma to make it fuse if it can be made
>dense enough, but then run it through a
>magnetohydrodynamic generator to get rid of the excess.
You're looking at the problem from the wrong end. The
problem isn't the intake end--the great majority of
the kinetic energy in the incoming plasma is going to
turn into heat that heats up that plasma, which is
perfectly fine. It's still kinetic energy.
The problem is the nozzle end. You've got this hot
plasma and you want to use the rocket nozzle to
"straighten out" the random velocity vectors of the
hot particles into a beautiful parallel stream of
particles. This is what a traditional chemical rocket
bell nozzle does, and they do a very efficient job of it.
Unfortunately, when your ultimate nozzle velocity is
supposed to be relativistic, it's not so easy to do
efficiently.
That's why one of the proposed "fixes" for the Bussard
ramjet concept tries to avoid slowing down the incoming
interstellar medium in the first place.
>So, here's my proposal for a self-contained interstellar vehicle:
[a concept involving anti-matter]
>Now, to launch again, the ship just needs to be supplied
>with antimatter. Since one can produce antimatter with
>just a particle accelerator and a dense target, which can
>easily be included on the ship, although it would take a
>*very* long time the ship could re-fuel itself via solar
>power.
This requires a nearby star, of course. I think if you're
going to rely on the resources of a star in the first place,
you might as well directly use the star's resources more
efficiently. In particular, you can use a solar powered
satellite to scoop up fusion fuel from the outer layers
of the star or the solar wind.
My gut feeling is that you could do well with this sort of
thing to refuel an anti-matter catalyzed fusion rocket.
Isaac Kuo
.
- References:
- Self-contained interstellar vehicle
- From: Logan Kearsley
- Self-contained interstellar vehicle
- Prev by Date: Acheiving .5c with Bombtrack Propulsion?
- Next by Date: Re: What practical jokes would you pull w/time machine?
- Previous by thread: Self-contained interstellar vehicle
- Next by thread: Re: Self-contained interstellar vehicle
- Index(es):
Relevant Pages
|
