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starship-design: Hydrogen Recombination Jet

The Free Lunch - Interstellar External Combustion Turbojet

What if there were a chemical reaction which would be self-propagating,
remotely controllable, spectacularly energetic, and self-damping when we
remove our structural mechanism; which could provide thrust without
requiring a huge energy input on our part? What space is full of, is a low
density of monatomic hydrogen neutral gas. The most urgent thing atomic
hydrogen wants to do, is to recombine chemically with another atom just like
it, to form molecular (diatomic) hydrogen. It wants to do that bad enough,
to make it the most energetic chemical reaction possible. Simple
compression, while keeping it cool enough to stay tolerable by hydrogen
molecules, will ignite this reaction. I think the starship is about to
become conceptually simpler.

There is free energy to be gathered in space. Though everyone sneers at
using chemical propulsion in starships, for this one you don't have to carry
fuel, which is a big plus. That it's the strongest chemical reaction also
helps. It will provide thrust for your ship, if you shape it right; even a 1
g thrust, if you burn enough of it. Making the starship driven by an
external combustion engine, poetically a flaming whirlwind, technically an
external combustion scramjet, which is a "supersonic combustion ramjet" of
the atmosphere, but this is a spaceship. There is not really "combustion" in
this jet, for there is neither oxidation nor reduction chemically, but it
can get hot and noisy as you make it. Burning is a fair shorthand name for
an atomic hydrogen torch, hot enough to conquer any material.

The way I see to use this is with a twist, which must be compensated by a
complementary moment of torque thrust, to the extent its torsion affects the
stability of the starship's orientation. The decision to use an artificially
created vortex of interstellar gas was motivated by the argument, that
ultrascale machinery cannot be built with solids, because it costs too much.
A ramscoop can collect from a large frontal area cheaply, using a cyclonic
storm started far ahead. So if you know how to start a whirlwind, using
explosive fuel (recombining atomic hydrogen) to produce torque, you can
later apply pinch on the waist of that tornado, to ignite general
recombination of all the remaining atomic hydrogen downwind in the vortex.
You have constructed a large scale turbojet in the scanty winds of space.

You can expend a great deal of energy on rays, bullets, beams and fields,
supporting structures made of shock fronts, ion sheaths, acoustic standing
waves, vapor curtains and similar ephemeral constructions, to make your
ship's vicinity a geometric sculpture, without spending as much energy as if
you had to twist that cyclone yourself. When you burn the interstellar gas
for thrust, there's no need to be thrifty with it, so you can set the
acceleration level to whatever is most comfortable for you. Like 1 g. This
vortex engine is a one way design; I don't think there is any way to turn it
around. Lucky there are other ways to slow down.

Not bad for free, but I think I'll keep my tuned LINAC around, for when I
really want legs on my starship.

Johnny Thunderbird