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Accumulate Fuel at Space Station?
I would like to know why we don't travel to Mars by first lifting many
loads of fuel to the space station. The actual spaceship would be assembled in space, at the space station, from parts that are lifted there the same as the fuel is lifted, by conventional rockets. Perhaps 20 to 50 trips would be necessary to finally have a suitable ship with lots of fuel. However, the payload to fuel ratio of this ship would be far greater than a ship launched from earth, since it has already escaped most of earths gravity. Also, the thrust required might be only 1/20 of what it would be if launched from earth, so a small propulsive system will do the job. I'm assuming a human crew; they would be taken to the space station at appropriate times by conventional rockets or the space shuttle. This is not my idea; It has probably already been studied, but since I never hear about it I assume there must be some catch to this idea. If anyone knows something about the status of this idea I would very much like to read about it. Mitchell Timin -- "Many are stubborn in pursuit of the path they have chosen, few in pursuit of the goal." - Friedrich Nietzsche http://annevolve.sourceforge.net is what I'm into nowadays. Humans may write to me at this address: zenguy at shaw dot ca |
#2
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Accumulate Fuel at Space Station?
I would like to know why we don't travel to Mars
by first lifting many loads of fuel to the space station. The actual spaceship would be assembled in space... 20 to 50 trips would be necessary... Perhaps something like that will be done someday, but there are some disadvantages. For one thing, storing tons of flammable fuel at a space station might be somewhat dangerous. Also, assembling things in space is a slow, difficult process. And the cost of making 20 to 50 trips would be huge. James |
#3
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Accumulate Fuel at Space Station?
HOST Comp JimS wrote:
I would like to know why we don't travel to Mars by first lifting many loads of fuel to the space station. The actual spaceship would be assembled in space... 20 to 50 trips would be necessary... Perhaps something like that will be done someday, but there are some disadvantages. For one thing, storing tons of flammable fuel at a space station might be somewhat dangerous. Also, assembling things in space is a slow, difficult process. And the cost of making 20 to 50 trips would be huge. But how does the cost, and time, compare with making one trip with 20 to 50 times the total mass? Can we even do it? It needs a detailed systems study, which probably has already been done. If not, why not? If so, I would like to know the results. I think the fuel danger is not excessive. The fuel containers could be kept at a considerable distance from the station, on a wire heading toward the earth. Tidal forces would keep the wire taught. That might be necessary if they were solid fuel, which could explode if hit by a micro-meteorite. OTOH, if the fuel was two components, say oxygen and hydrogen, then neither oxygen tanks not hydrogen tanks are explosive on their own. To keep them cold in space mainly requires sheilding from sunlight. m -- "Many are stubborn in pursuit of the path they have chosen, few in pursuit of the goal." - Friedrich Nietzsche http://annevolve.sourceforge.net is what I'm into nowadays. Humans may write to me at this address: zenguy at shaw dot ca |
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Accumulate Fuel at Space Station?
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#5
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Accumulate Fuel at Space Station?
The actual spaceship [for Mars] would be assembled
in space... 20 to 50 trips would be necessary... the cost of making 20 to 50 trips would be huge. But how does the cost, and time, compare with making one trip with 20 to 50 times the total mass? Are you asking if we could build a rocket that could carry the equivalent of 50 shuttle payloads? I guess it's theoretically possible, but I doubt if it's practical. Your original question asked about the practicality of a Mars mission that required a *massive* amount of mass being lifted into orbit and then assembled in orbit, and I'm just saying that it would probably be too expensive to get funded. NASA will need to find cheaper ways of getting there. James |
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Accumulate Fuel at Space Station?
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Accumulate Fuel at Space Station?
JRS: In article , seen in
news:sci.space.science, nafod40 posted at Wed, 11 Feb 2004 08:30:18 :- wrote: I think the fuel danger is not excessive. The fuel containers could be kept at a considerable distance from the station, on a wire heading toward the earth. Tidal forces would keep the wire taught. That might be necessary if they were solid fuel, which could explode if hit by a micro-meteorite. OTOH, if the fuel was two components, say oxygen and hydrogen, then neither oxygen tanks not hydrogen tanks are explosive on their own. To keep them cold in space mainly requires sheilding from sunlight. We could send up water, then just let solar array-powered electrolysis slowly do its magic to make the fuel. Two years for a bag of fuel? No problem, no rush. That way no volatile components in the launch. You could freeze the water, and use it as part of the structure of the launch vehicle to reduce weight. Alternate launch techniques such as rail guns? The payload would certainly tolerate the G's. To do a reasonably useful mission requires, give or take an order of magnitude or so, enough fuel to accelerate a ton by 10 km/s, putting 0.5 * 1000 * 10000^2 = 5E10 joules into the payload; given the way a rocket works, the energy in the fuel must be significantly greater - say double, giving 1E11 joules. The solar constant is about 1400 W/m^2; assume solar panel efficiency about 35% which means 5E2 W/m^2 available, 5E2 J/s/m^2. A year is 3E7 s, giving 1.5E10 J/yr/m^2. On that basis, a modest 6 m^2 panel allows for a mission per year. That's well-enough placed with respect to the ballpark to justify a calculation using better figures. The efficiencies above are intentionally generous. Load momentum is 1E7 units; to get that in a year needs a thrust of about 0.3 N. What Isp can an 0.3 N H-O rocket give? I think of the electrolysed gases being fed directly to an engine, so producing a continuous-thrust mission running on sunlight and water. -- © John Stockton, Surrey, UK. Turnpike v4.00 MIME. © Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; some Astro stuff via astro.htm, gravity0.htm; quotes.htm; pascal.htm; &c, &c. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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Accumulate Fuel at Space Station?
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#10
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Accumulate Fuel at Space Station?
Rick Jones writes:
wrote: OTOH, if the fuel was two components, say oxygen and hydrogen, then neither oxygen tanks not hydrogen tanks are explosive on their own. To keep them cold in space mainly requires sheilding from sunlight. Wasn't it an O2 (LOX?) tank that detonated on the Apollo 13 mission? Only because certain electrical components within the tank were overloaded and caught on fire. A fire burning inside a liquid oxygen tank burns =VERY= enthusiastically. The abrupt release of heat by the fire cause the tank pressure to rise very, very rapidly, which caused the tank to _RUPTURE_, not explode. The rupture of the tank releasing its pressurized contents into the equipment bay very rapidly, and propelling fragments at high velocity through nearby equipment. The effects produced by the rupture of the overpressurized, overheated tank were _SIMILAR_ to an explosion; however but there is nothing =INTRINSICALLY= "explosive" about liquid oxygen per se. -- Gordon D. Pusch perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;' |
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