h a l f b a k e r y
I think this would be a great thing to not do.
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This uses the available resources on the planet for
launch - the "Dust Drive". On earth it would be sand, on
the moon it would be moon dust and on Mars martian
sand. As a rocket
is simply the ejection of mass at high speed this would
be used as the 'fuel', but without the explosive capability
of current rockets to eject the mass.
Instead, the rocket would have a solar powered magnetic
mass ejection system that would soak in focused
sunlight to heat a large section of salt that would
concentrate and hold the solar energy until sufficient
power was available to be able to transfer the heat
energy in to a converter that would magnetically eject
the mass (the planetary dust) at high speed until launch
The separation of energy and mass would allow any
available mass to be ejected once the mass ejection
system was at full power. Obviously this technology
currently does not exist and would require a number of
inventions before feasible (the magnetic ejection system
comes to mind) but this is a high level vision of what is
possible given available resources.
On all planets, a launch station would need to be
established that used mirrors to focus sunlight on the
salt reservoir of the rocket which could also be
refocussed from the planet to incoming rockets to slow
them down for landing. The PS10 solar power tower could
be used as an example of this.
||You may need to study the meaning of the phrase
"energy density" and see how that applies to
ordinary rocket fuel, vs the system you are
describing. I think you will find yours to be woefully
inadequate even for Mars, much less the Earth,
although it might work on the Moon.
||Water is better as simple reaction mass. It's a safe, easily handlable
liquid, it's widely available, and if you launch in a rainstorm noone will
notice the exhaust.
||The only advantage to using dust in this manner is
the great quantities in which it can be found in
certain environments. That's not enough.
||This is a complicated system just to fling dead mass. A 1.0 kg block of stone (compressed dust, if you will) would have to be hurled at 9000 m/s to obtain the impulse attainable from 1.0 kg of gasoline. Uranium-235 is 2,000,000 times more energy dense than gasoline.
||Yes, wouldn't it be nice to have a rocket system that could use pretty much any available material for reaction mass and the sun for energy, but you'll need something better than molten salt for storing your energy. It's fine for a stationary solar tower because it's cheap and this application doesn't care about size and weight. For a rocket, mass is enemy #1, and size tends to increase the mass of the structure.
||But the Mars Leeches will be terrified of this. Although during the decade that it sits still soaking up adequate focused sunlight, they may overcome their fear enough to come up and tip it over with a stick.
||//they may overcome their fear enough to come up and tip it over with a stick.
||Who is to say our own species did not learn tool usage this way, and those travellers are still wondering why the light went out...