Re: Surface -- Orbit traffic

Thanks for all the replies so far, I'll try to roll a few into one,
because I don't have time tonight to answer each one separately.

First, don't be so quick to discount conversion air-rams.  Sure, you
get aerodynamic drag, but you also get thrust.  At high altitudes, you
get less thrust because you scoop up less air, but you also get less
drag, so the two effects should (to first order) cancel out, letting
you get up to the outer regions of the atmosphere without using any on-
board propellant at all.

Well, maybe conversion rams that don't rely on supersonic combustion
may be more versatile here, but I still remain skeptical. In the end -
so I think - it comes down to dynamic pressure, and if that's high
enough to give you thrust, it is probably also high enough to heat up
your hull (friction).

 Third, it is much more energy rich than chemical combustion,
leading to much greater thrust (and thus higher speeds at which drag
matches thrust).

Right, but we also get a certain waste heat problem - the airframe
must be sleek to minimize drag, so there can't be any cooling fins or
the like, and we only have the airflow itself to cool the engine.

 If you
are converting baryons in atmospheric nuclei, you end up with just a
bunch of alpha particles, deuterons, and He-3 - but maybe a small
amount of tritium.

Alright, here I need to ask, didn't you just say last week that baryon-
decaying light elements such as nitrogen or oxygen will release enough
energy to dissociate the entire atom into its individual protons and
neutrons? D, T, 3-He and 4-He would be all wonderful, but getting
neutrons would still be annoying.

Anyway, I had planned to use those partial conversion reactors
(decaying a single baryon out of a heavier element) only for
(interplanetary) thermal rocket engines, because of the thermal and
radiation problems involved. However, there would be also hydrogen
converters that are fed with protons and convert these to pions - I
think it was you who suggested the principle to me - for electrical
power generation. Maybe this type could also be made to work as
thermal core for a relatively "low-powered" rocket or ramjet engine.
The pions would strike metal targets, heating them up, and the metal
targets heat up the propellant (air/water). If the pions won't cause
further radiation troubles, I haven't checked on that. The specific
impulse is basically limited by the thermal tolerance of the engine -
the usual 3000K, give or take.

Also, you don't need to reach orbit, only get out of the atmosphere.
As Wayne pointed out, you have high acceleration drives on your
interplanetary/interstellar spacecraft.  One of these can easily get
into LEO, expend the 7.6 km/s to come to rest with respect to the
planet and rendezvous with a shuttle that has boosted out of the
atmosphere and has reached the top of its trajectory.  Then the
spacecraft puts out another 7.6 km/s to get back into orbit, either
carrying the shuttle, or dropping the shuttle but taking the cargo on
board.

I really like this idea, sort of like orbital circus artists playing
fly and catch. :)
Those torchships would probably be operated by the local authorities,
though, so as not to let any old hillbilly free trader take his
terawatt drive closer to the planet than absolutely necessary. Or
maybe that precaution is not necessary, as the catching ship would
have to be relatively slow anyway, and couldn't speed up to truly
destructive kinetic energies in such a short time.

laser station is powered by a big honkin' conversion reactor, and then
beams that power to shuttles as they boost out, either to heat the air
for a laser air-ram, or to give that last bit of boost with a laser-
water rocket.

Sorry if I sound dumb, but how would laser air-rams or laser water
rockets work? For the latter, I'm guessing the shuttle would get a
parabolic mirror stuck on its tail, into which propellant is injected
as a ground-based laser beam heats it up. (Wouldn't the laser beam
eventually be reflected to god knows where?)
But how the ramjet would work, I cannot fathom.

So much for now, thanks again.
.

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