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Dust Drive

Solar powered rocket system
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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 is achieved.

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.

noblea, Apr 09 2014

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       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.
Vernon, Apr 09 2014
  

       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.
8th of 7, Apr 09 2014
  

       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.
Voice, Apr 09 2014
  

       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.
the porpoise, Apr 09 2014
  

       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.
scad mientist, Apr 09 2014
  

       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.
bungston, Apr 11 2014
  

       //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...
not_morrison_rm, Apr 11 2014
  
      
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