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Orbital Mill

what goes up... stays up. Use a solar mirror array to recycle rocket boosters etc. into new spacecraft and stations.
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Take the entire rocket up to orbit and, using a solar mirror array, melt it down into differentiated blobs of metal which is then reshaped as needed into structural and casing material for satellites, probes, ships, stations, etc.

It's a matter of math. Sure, multistage rockets are good for the short run because they don't use as much fuel, but wouldn't it be better to not waste the accumulated delta-v of discarded boosters and just send the entire thing up ? That way when you wanted to launch a probe or satellite, you just send up the innards and have the frame and skin built and attached in orbit.

"Solar Mirror Array" sounds complicated, but it's pretty much just a hectare's worth of aluminum foil (say 350 rolls from the supermarket) and a bale of coat-hanger wire, assembled with duct-tape, using a protractor to measure the angles.

Other stuff:

Spherical Space Station: now that we're not encumbered by the need for panels and stringers to fit inside a Shuttle, a sphere is pretty obviously the best design for a space station, barring a donut or something if you want artificial gravity.

Mass driver in orbit: there's still quite a bit of velocity that has to be tacked on in order to go anywhere else in the Solar System, so why not save propellant weight and add the velocity in orbit from a Solar PV charged mass driver. Yes you need twice as much energy (because when you're done you have to move the mass-driver back where it was) but it's free.

FlyingToaster, Aug 10 2012

Windy Miller http://www.youtube....watch?v=EGfxyXBqIzU
[not_morrison_rm, Aug 11 2012]

[link]






       Orbital industry will happen, but the main feedstock is probably not going to be terrestrial.   

       And, most likely, a cylinder is the best design for a space station, since it allows uniform gravity when spun.
MechE, Aug 10 2012
  

       That's the next stage from this (which is a step ahead of what we've got now). The current space station looks to be at the point where if another module or two gets added on it'd take less material to build as a concentric sphere for the same internal space.   

       //cylinder// hmm... true... what about a rotating paraboloid or ellipsoid for artificial gravity? looks sorta like an M&M candy. But they have to be really big in order to fool the inner ear.
FlyingToaster, Aug 10 2012
  

       Apparently about 550 meters (dia) for full earth gravity, with no risk of inner ear problems. If you can get away with 1/2g you can cut it to more like 220. If you're going to accept that some people have difficulty adapting, you can get it down to about 70m for a full g. Combine the two, and you can push it fairly small maybe 35m.
MechE, Aug 10 2012
  

       What if you could surgically drain the fluid from the semicircular canals and put it back in after the mission? That would negate some inner ear problems but might make balance difficult.
DIYMatt, Aug 10 2012
  

       If you want centrifugal "gravity", swing your habitat around at the end of a cable. The counterweight can be another habitat, or maybe your atomic power-generation system.
baconbrain, Aug 10 2012
  

       Waste not, want not is a pretty good engineering principle, and one that’s been given a lot of thought by spaceflight folk, mainly (as far as I know) around the “wet workshop” idea, which von Braun pushed for hard in the 1960s, and was given serious consideration for 1973’s Skylab. In the end, the “dry workshop” idea (building the inside of you spacecraft on the ground, rather than building it inside the empty fuel tanks of a spent booster) won out, I think because of justified lack of confidence in the safety of 1970s astronauts building stuff in space.   

       Recycling spent spacecraft – melting down their metal for casting into new parts - certainly makes sense. Most, if not all rocket upper stages for the past 50 years, could have been put into orbits, but were intentionally not, to avoid producing big, dangerous space junk. If one or more orbiting “recycling facilities” (with “solar smelters”) were flown, spent upper stages (or lower, if and when SSTOs are flown) could be routinely navigated to them (or vice-versa) and recycling commenced in pretty routine fashion.   

       Here’s where, I think, economics smacks such plans in the face in a chicken vs. egg manner. At whatever (likely very high) cost, you’ve got your space recycling plant, a steady input stream of what used to be worse-than-useless trash (though how cheaply you could buy it from the folk who launched it involves the logic and psychology of capitalism, which has baffled me since I was a youngling), and the ability to produce whatever your factory can, but the big, needy consumers of such stuff are where they’ve always been, on the ground, where much cheaper sources of whatever you can make already rule the market. Your market are the people and machines in orbit and beyond (with some ingenuity, and aided by the lucky presence of the Earth’s faint but useful magnetic field, you should be able to fly your goods out of orbit if needed), a market that, with the exception of a handful of folk at the ISS and the odd serviceable satellite, doesn’t yet exist.   

       Restating the old chicken and egg riddle: which must come first: the space colony full of consumers, or the space factory? I’ve a suspicion this subject has a “why did the chicken cross the road” parable in it, too, but’ll leave that that to the pros.
CraigD, Aug 10 2012
  

       //Mass driver in orbit: ... Yes you need twice as much energy (because when you're done you have to move the mass-driver back where it was) but it's free.// High school physics to the rescue on this. You don’t need as much energy to “reset” any sort of “launch cannon”, because: 1) (hopefully) most of the mass it threw isn’t returned to the starting position 2) even if most of it is, the force required to move it is much less, practically zero.   

       Energy = Work = Force * Distance =/= Mass * distance   

       The big practical problem with space cannons is that, because they must throw projectiles much faster than ordinary ones – something in the vicinity of Mach 30 - they must be really, really big. Coupled with the trouble of throwing anything at such speeds in the thick lower atmosphere, and you find you need your cannon to be on the order of 20 km long, hold a vacuum inside, and have its mouth at about 20 km altitude.   

       While not in principle impossible, this is colossal engineering, dwarfing anything ever before built. So serious discussion of systems like this have been limited to launch assist systems, systems on less massive bodies (such as the Moon), or discarded completely in favor of ones like launch loops.
CraigD, Aug 10 2012
  

       // //twice as much// not// ah, right right.   

       //chicken vs. egg// not really.   

       It's not just a matter of putting a factory in space (albeit a rather simple one) to build satellite/probe bodies and structure, nor simply a matter of "recycling = good". If you're recycling booster rockets in orbit into satellite superstructure it means that the weight of aforementioned satellite parts don't have to be shipped up from Earth, just the innards. That means cheaper satellites and probes.   

       Those booster stages were already well on their way to orbit when they got tossed. All that KE down the tubes.   

       //fuel tanks// I actually don't like the idea; not just because I think this one's better, but because it means either compromising the design of a fuel tank or the design of a spacelab.   

       IMHO a spherical station is far superior to the tin-cans+duct-tape we've got up there now. Just build onion shells and hold them to each other with bungee cords. Crew quarters in the middle, then labs, then storage, then observation/egress/antennae in the outermost.
FlyingToaster, Aug 10 2012
  

       I thought this was going to be some kind of windmill in space?   

       cuts to ...Windy Miller putting on his space suit and going out the watch the solar wind propelling the huge foil blades, as it grinds the wheat...
not_morrison_rm, Aug 11 2012
  
      
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