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Science Forum

  1. Standard member sonhouse
    Fast and Curious
    30 Sep '13 08:32
    What a useful tool for a space station, no need to have a jillion different tools or gadgets as spares, just the design fed into the printer and a few pounds of material to feed the printer and lo and behold, a new wrench to solve a problem that can't wait till the next supply rocket. Make new valves or some such on the spot, designs worked over on the ground and just relayed up digitally to the printer.

    A very significant development for space travel.
  2. 30 Sep '13 09:22
    Originally posted by sonhouse
    What a useful tool for a space station, no need to have a jillion different tools or gadgets as spares, just the design fed into the printer and a few pounds of material to feed the printer and lo and behold, a new wrench to solve a problem that can't wait till the next supply rocket. Make new valves or some such on the spot, designs worked over on the grou ...[text shortened]... d just relayed up digitally to the printer.

    A very significant development for space travel.
    They obviously can only make things made with whatever material the printer uses, but still there is a lot you can do with them. I am hoping I can afford to get one one day. The big problem right now is the cost of the materials is quite high. I would probably have to make and sell quite a lot of stuff to pay for what I want for myself.
  3. Standard member sonhouse
    Fast and Curious
    30 Sep '13 09:27
    Originally posted by twhitehead
    They obviously can only make things made with whatever material the printer uses, but still there is a lot you can do with them. I am hoping I can afford to get one one day. The big problem right now is the cost of the materials is quite high. I would probably have to make and sell quite a lot of stuff to pay for what I want for myself.
    3D printing is still in its infancy. Improved plastics will make tools almost as strong as metal in the near future. They can make stuff with metal now in 3D printers but that technology is a bit out of reach for the average person for now at least. All that technology will come down in price.
  4. 30 Sep '13 14:42
    Originally posted by sonhouse
    Improved plastics will make tools almost as strong as metal in the near future.
    The lighter the better when it comes to space, so plastic is better than metal.
    The other great advantage is that in some cases you can reuse the material. So once you no longer need that wrench, you can reprint it into something else.
    You could also send up science experiments etc where most of the structural components are made of that material, then removed and reused when the experiment is over. You could even have major parts of the space craft made of it so that when they are no longer needed you can recycle them.
  5. Standard member sonhouse
    Fast and Curious
    30 Sep '13 15:01 / 1 edit
    Originally posted by twhitehead
    The lighter the better when it comes to space, so plastic is better than metal.
    The other great advantage is that in some cases you can reuse the material. So once you no longer need that wrench, you can reprint it into something else.
    You could also send up science experiments etc where most of the structural components are made of that material, then ...[text shortened]... parts of the space craft made of it so that when they are no longer needed you can recycle them.
    Recycling, maybe, not sure about that one. If the polymer was processed somehow one way, it may not be able to go back to the pristine plastic. Or I could be all wet. One thing is obvious, it would take energy to get the plastic tool back into printable plastic even if it was able to do so. It would have to be heated to its melting point and then shredded or liquified, not sure the exact process, just guessing. But it is clear it would have to be heated and that requires some energy. Could be solar and therefore no strain on the space craft power supply but not if you are in a craft a billion miles from home or halfway between the stars, say 2 light years out going to Alpha Centauri, 4.3 ly away. You won't get much in the way of solar energy there Well, you could have reflectors 10 miles across, maybe you would harvest a kilowatt That works out to about 75 nanowatts per square meter, and 10 miles= 16 kilometers, sorry guys, you need more than that! That array gets you 20 watts!
  6. 30 Sep '13 15:32
    Originally posted by sonhouse
    One thing is obvious, it would take energy to get the plastic tool back into printable plastic even if it was able to do so.
    I believe most plastic based 3D printers must heat the plastic while printing.

    .... if you are in a craft a billion miles from home or halfway between the stars, say 2 light years out going to Alpha Centauri, 4.3 ly away.
    Then you should have nuclear power.
  7. Standard member sonhouse
    Fast and Curious
    30 Sep '13 15:55 / 1 edit
    Originally posted by twhitehead
    I believe most plastic based 3D printers must heat the plastic while printing.

    [b] .... if you are in a craft a billion miles from home or halfway between the stars, say 2 light years out going to Alpha Centauri, 4.3 ly away.

    Then you should have nuclear power.[/b]
    Yes you would have to, just showing how useless solar power would be in space between the stars. Halfway to Alpha Centauri the amount of energy you collect from the sun goes down by a factor of 256 million. Reaching that minimum if you turn your cells around you then start collecting about the same amount from AC, but the energy collected gradually goes up to about the same as you would have gotten from Sol since the two stars have similar energy outputs. So at Earth's distance, that array would collect 250 odd Gigawatts, a healthy chuck of energy and it would build up to something like that coming in to AC.

    That energy could be the power needed to slow down the craft with some kind of rocket, like the Vasimir plasma rocket, low thrust but 24/7 operation. Besides the deceleration you would get just from the mirror reflecting the light from AC.

    The problem there would be applied rocket thrust could distort the shape of the mirror so it would require stiffness able to withstand whatever the thrust levels you have.

    Going to 0.5c at 1 g of acceleration would take about 6 months so doing the same at 0.1 g would take 60 months or 5 years. So if that was the thrust of the system, it would have to be able to take that amount of stress on the last leg of the journey. You would cover about 1/4 ly in that first 5 years, so that leaves about 4 ly to go and 3 3/4 ly at 0.5c or about 7.5 years plus ten years accelerating and decelerating so about 18 years for the whole journey. Say 2 years around AC and back, about 38 years total. At 0.5c there would not be much in the way of time dilution, about 15 % so for the portion spent at that velocity, about 15 years, the crew would be about 2 years younger than a twin, not much of a deal. So the whole trip would take 36 ship years but 38 years would have gone by on Earth.

    You don't get serious with that time dilation till you get to about 0.9c which would be about 2.2 to 1, so if the trip was at 1 g, it would take say 11 months to get to 0.9c and you would have covered about 1/2 ly so 1 ly at about 0.5c average means two years of acceleration and deceleration and 3 ly of coasting at 0.9c which would account for about 1.3 years of ship time so now the whole trip takes about 11 years, with say, 1.5 years at AC studying the place.

    Now you get about 2.3 to 1 ship time or roughly 5 years of ship time while 11 years goes by on Earth.

    I would do such a journey!

    It gets better both for longer trips at 0.9c and for more acceleration to get to say 0.999c where the ratio is 22 to 1, so a journey of 22 ly would mean 1 year of ship time so round trip, 2 years of ship time plus whatever time you spent at your goal, say 5 years, then Earth time would be 44 plus 5 years, or 49 years having gone by on Earth but the crew is only 7 years older. The world would be 42 years ahead of the crew, so if twins left, one on the journey and one left behind, at age 20, the crew member would be 27 coming back and the twin on Earth would be 62. Wouldn't that be something, to meet your twin brother or sister who is 42 years older.
  8. 30 Sep '13 17:47
    Originally posted by sonhouse
    Besides the deceleration you would get just from the mirror reflecting the light from AC.
    You cannot reflect light and use it for solar power. To use it for solar power you need to absorb it. I suppose some of it might get re-emitted at a different wavelength.
    However, absorbed light would only have half the acceleration/deceleration of reflected light.
  9. Standard member sonhouse
    Fast and Curious
    01 Oct '13 14:59
    Originally posted by twhitehead
    You cannot reflect light and use it for solar power. To use it for solar power you need to absorb it. I suppose some of it might get re-emitted at a different wavelength.
    However, absorbed light would only have half the acceleration/deceleration of reflected light.
    Actually you can get the best of both worlds. Solar sails use the photon pressure from the sun to tack its way around the solar system with no need for fuel. However, that does not stop one from having cells where the light is reflected to, the sails would be just like Earthbound sailing ships, they would have a concentrating effect so you could just have a bunch of cells at the focal point and get both acceleration and power.
  10. 01 Oct '13 15:47 / 1 edit
    Maybe the solution lies in figuring out how to somehow convert kinetic energy using some sort of field so that when random space junk collides with the space craft it harnesses it to move instead of being decimated.
  11. 01 Oct '13 16:55 / 1 edit
    Originally posted by sonhouse
    However, that does not stop one from having cells where the light is reflected to,
    Yes actually it does. If you reflect the light onto solar cells on the same spacecraft then the light hitting the solar cells has an equal and opposite impact on the spacecrafts motion. The total effect if the photons are entirely absorbed at the solar cells is that half the effectiveness of the sails is lost.
    Its like having a rocket then rigging up a blockade in front of your rocket nozzle.
  12. 01 Oct '13 16:58
    Originally posted by MISTER CHESS
    Maybe the solution lies in figuring out how to somehow convert kinetic energy using some sort of field so that when random space junk collides with the space craft it harnesses it to move instead of being decimated.
    There isn't enough random space junk to make it worthwhile. It might however be worth harvesting known space junk such as rocks off Saturns rings or small asteroids or comets as you could gather a large amount of mass without having to lift it out of earths gravity.
  13. Standard member sonhouse
    Fast and Curious
    01 Oct '13 17:46
    Originally posted by twhitehead
    Yes actually it does. If you reflect the light onto solar cells on the same spacecraft then the light hitting the solar cells has an equal and opposite impact on the spacecrafts motion. The total effect if the photons are entirely absorbed at the solar cells is that half the effectiveness of the sails is lost.
    Its like having a rocket then rigging up a blockade in front of your rocket nozzle.
    You don't make the mirror and the PV cells hooked together, you make them independent movers, then you can collect the energy, use a small portion of that energy to power a small rocket to keep up with the sail and you are in business.
  14. Standard member sonhouse
    Fast and Curious
    01 Oct '13 17:48
    Originally posted by MISTER CHESS
    Maybe the solution lies in figuring out how to somehow convert kinetic energy using some sort of field so that when random space junk collides with the space craft it harnesses it to move instead of being decimated.
    The nearest thing to that is the speculative work being done at NASA on warp drives, real warp drives. The only thing stopping them is they need to figure out a way to make a lot of negative energy, which right now you only get in one watt packages if that. They need gigawatts of negative energy, but the idea is you warp space ahead and behind in such a way as the craft is basically falling down a gravity well, propelling it forwards and possibly even ten times the speed of light.
  15. 01 Oct '13 18:08
    Originally posted by sonhouse
    The nearest thing to that is the speculative work being done at NASA on warp drives, real warp drives. The only thing stopping them is they need to figure out a way to make a lot of negative energy, which right now you only get in one watt packages if that. They need gigawatts of negative energy, but the idea is you warp space ahead and behind in such a way ...[text shortened]... ling down a gravity well, propelling it forwards and possibly even ten times the speed of light.
    That would be awesome if it happens in my lifetime. Beam me up, Scotty!