Re: Space warfare- fighter ship design
- From: "IsaacKuo" <mechdan@xxxxxxxxx>
- Date: 6 Sep 2005 07:39:33 -0700
Logan Kearsley wrote:
>I think I have come up with a fairly good design for
>defensive ship/drone for space warfare.
>Tell me what you think:
I think you've started with the wrong priorities.
If the design of military equipment so far is any
indication, a space warship will be first and
foremost a spaceship, and a weapons platform
a distant second.
The dominant design requirements will be those
which any spaceship will require--the drive systems,
power systems, thermal regulation systems, radiation
management, and life support (if manned). In
particular, the drive system will impose the
fundamental design of the spaceship.
>For purposes of packing the most stuff into the
>smallest cross-section, the hull would be spherical.
This may be entirely impractical due to the nature
of the drive system and/or the thermal radiator system.
>The weaponry would consist of a phased array of
>laser diodes covering nearly the entire surface of
>the sphere.
It may be impossible to acheive coherence in the first
place, but even assuming the technology is acheived,
it may be impossible in practice to maintain coherence
while under enemy laser fire.
Personally, I'm highly skeptical about the acheivability
of the idea in the first place. I doubt diodes can be
packed tightly enough to acheive such a phased array
effect (not for wavelengths small enough to have useful
space combat ranges).
In any case, if you're operating a weapons grade high
energy laser, you need some sort of serious heat
rejection system.
>but usually everything would fit together into a
>continuous surface of laser diodes, broken in only
>five places. One opening for an engine, and four
>for four (whooo, weird word choice there) fish-eye lens
>cameras arranged in a tetrahedral pattern to give
>the targeting computers an all-around view.
You're missing a big one--the heat rejection system.
But let's ignore that for the moment...
Fish-eye lens cameras would be of dubious value, since
they'd have low resolution and sensitivity. Large
aperture telescopic optics would give you high resolution
and high sensitivity. Sure, it takes time to scan all
around, but distances in space are very very big, and
as such it takes a long time for stuff to move across
one's field of view.
Of course, if you're going to have the bulk of a large
sensor mirror, you might as well use that volume for
your laser's main mirror.
>One only needs a single engine, because inside are mounted
>four heavy rings (fitted right against the walls, so they
>take up very little space),
In real life, attitude adjustment flywheels tend to be
small and compact, so as to minimize the space and weight
used. However, we're talking about satellites which
carry little/no on board propellant.
For an interplanetary spaceship, there are going to be
large propellant tanks--some sort of internal circulation
propellers could provide attitude adjustment as long as
high precision isn't required.
>For cooling purposes, I was thinking of carrying a tank
>of something with a very high heat capacity (probably
>just water- which could also double as radiation shielding)
>and pumping as much excess heat as possible into that
Every time we run heat rejection numbers here on
r.a.sf.science, high power equipment simply can't
be run for a significant time on an internal heat
sink.
>The engine, however, could itself be used as an active
>cooling system, by running the propellant pipes
>around/through the heat sink or whatever components
>need cooling before injecting the propellant into the
>engine.
This suffers from the same problem as internal heat
rejection--the only difference being that you are
throwing the heat sink overboard while you're at it.
Also, you're probably reducing the Isp of the propellant
down to chemical rocket levels...but the point is moot.
The vibrations from operating the rocket in the first
place plausibly spoil your beam coherence and your aim
anyway.
>I'm not entirely sure what sort of powerplant or
>engine would be best- I'm up for suggestion here.
This is actually issue number one! First, figure out
the propulsion system--all else is secondary. Think
about real life warships. Sailing warships looked
like sailing ships. Paddlewheel warships looked like
paddlewheel ships. Piston warships looked like
piston steamships. Turbine warships look like turbine
ships. The propulsion system can't just be some
afterthought in the design.
>I was thinking perhaps either a gas-core nuclear
>rocket or a VASIMIR engine,
For there to be any point to either, you need a
high power heat rejection system. You can't just
try to use the waste heat to preheat your propellant.
This was a mistake I myself made, and it was pointed
out to me that enthalpy limitations would reduce
the Isp of such an engine down to the levels of a
plain old solid core engine (i.e. low enough to be
self cooling).
>and probably some form of nuclear reactor for
>power (maybe a thorium-fueled amplifier reactor?).
Space fission reactors in general, including nuclear
rockets, are best mounted externally. You regulate
a fission reactor by controlling the neutrons. In
nuclear power plants, this means heavy shielding and
control rods to absorb the neutrons. In a space
reactor, you can save a lot of weight by simply
"venting" neutrons. The heavy shielding and control
rods can be replaced with lightweight rotating "mirrors"
on the outside of the reactor which either bounce the
neutrons back into the reactor or rotate to let them
"vent" into outer space. This reduces the waste heat
that needs to be rejected, also.
Note that for a modest increase in volume/mass/complexity,
a solid core nuclear thermal rocket can be designed to
be a dual mode reactor (either a thermal rocket for thrust,
or a power reactor recycling "propellant" through a
condenser/radiator).
>On a completely different note, though, as long as
>I'm talking about high-tech weaponry, how does this
>sound for producing a coherent neutron beam: get a
>slug of fissionable/fertile material and cool it to BEC
>temperatures. Trigger a nuclear reaction in the usual
>way, by injecting a small number of excess neutrons
>in one end, and the whole slug should decay at the same
>time, in the same direction, throwing out a huge flux of
>coherent neutrons, right?
I am unaware of any sort of "lasing" effect with the
neutrons of a fission reaction.
Isaac Kuo
.
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