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Re: starship-design: We need to get on the same (pellet) track first

Hmmm, I sent this letter 2 hours ago, but didn't receive a copy from SD yet.
If anyone else got this letter already, then you can throw away this one
because it is identical except for these sentences.


>>I suppose a black hole as stardrive does comply with the rocket equation?
>Well, it would be bizarre, but you could theoretically build a
>"rocket" around a black hole.  For instance, it could be a large
>sphere with a hole.  It absorbs Hawking radiation from the black
>hole, except for that hole (which is where thrust comes from).
>This black hole is kept from evaporating away by feeding it extra
>mass from the fuel storage.
>A really bizzare starship, considering how much better it would be
>to just use the black hole as a highly effective anti-matter producer
>(in a fixed anti-matter factory).

Hmmm yes, I guess as long as you are a selfsufficient ship, you will comply
with the rocket equation.
I doubt though that you can get enough antimatter for these high exhaust
velocities. Likely you have to feed much more matter to the blackhole than
that you will get antimatter in return.
Your energy/mass ratio may be worse then for a chemical fuel.

>>>If you'd like, I can rehash my calculations on the potential muzzle
>>>velocities and other limitations of mass drivers.  The overall
>>>conclusions are actually pertinent to this discussion, since EM mass
>>>drivers would be used to fire pellets from the fuel packets in my
>>>stardrive proposal.
>>Any numbers with calculations are welcome. What I'm most interested in, is
>>how much mass you will need (and thus how much effort one has to do to put
>>it in a pellet track).
>I should recalculate things and type them up on my web page.
>Anyway, the important factor to keep in mind is that for any
>useful muzzle velocity, the acceleration occurs essentially
>instantly for purposes of rejecting waste heat.
>For a pellet launcher meant to fire frozen DT pellets, this
>would seem to be disastrous.  The solution, as I see it, is
>to use a "pusher plate" of plasma pushing a frozen DT sabot
>which sacrificially melts, leaving a core frozen pellet which
>leaves the muzzle.  Beyond the muzzle is a cylinder which
>looks a little like a large gun silencer.  It is rotating
>quickly and has a series of conical baffles; its only openning
>is through the center, which the frozen pellet passes through.
>Gas pressure expansion forces most of the waste gas into the
>conical baffles, where centrifugal "force" funnels the gas to
>reclaimation pumps along the outer surface of the cylinder.
>Thus, most of the pusher plate and plasma material can be

You say the gun silencer has series of conical baffles, but you don't
mention how these baffles are attached to the "silencer".
You suggest the acceleration of a pellet happens almost instantaniously by
some plasma expansion. I wonder, won't the launcer blow apart?

>>>When it comes to exhaust velocity, the harshest fact of rocket design
>>>is that the limiting factor is _availability_.
>>True, but I wonder, is a ramjet of the size that we need physically
>This ramjet isn't supposed to scrounge around for interstellar
>hydrogen, so its diameter is determined by how accurate the
>pellet tracks can be laid and followed.

To Kelly you wrote "TV tubes don't have to be many times longer than they
are wide", you already noted that protons need 1000 times more energy.
I think that the amount of protons/electrons will make a difference too.
A TV has to move around less than picograms of matter, compared to the
kilograms that we need. That's a difference of rougly 15 magnitudes.
Luckely, we won't have to supply that power since the particles will give
back their energy as soon as they leave the magnet. The fieldstrength should
not alter too much when the particles fly through the field of the
superconducting magnets.

>>It may be so inefficient that the power losses melt it away the
>>instant that it starts to produce 1E16 Watt of power.
>The coolest thing about ramjets is that using superconducting
>coils and an aneutronic fusion reaction _no_ waste heat is
>absorbed by the starship.  Superconductors aren't just almost
>lossless, they are _entirely_ lossless.

OK, the magnets aren't giving losses, but isn't there still a lot of
uncontrolable heat from the thermal radiation from the hot particles?

A more practical question: How are the superconducting magnets kept from
blowing up? The charged particles that fly trough the magnets will create a
magnetic flux. Normally as long as the particle flies trough without
velocity gain, the superconducting magnets will have the same current before
and after the particle flew trough. But in the ramjet design the particles
will exit faster than they arived and thus will leave a non-zero flux.
I do know little about how superconductors are given a current and a
magnetic field, so the above question is more likely a result of not knowing
then of doubting the design.


P.S. If you reply, would you mind not to "reply to all"? As a default you
will reply to the author and to Starship Design. The result is that the
person you reply to will get your message in duplicate.