Optical Levitation, Space Travel, Quantum Mechanics and Gravity 82
An anonymous reader writes "Light doesn't just make things brighter; it can also push things around. Normally this "radiation pressure" force is so small you don't notice it. But if you get a really big mirror then you could use it to power a space ship to the stars. This is the idea behind solar sails. The impact of light is more obvious on small things. Scientists are thinking about levitation of a mirror that would be large enough to see with the naked eye. If this turns out to work, the motion of the floating mirror could be used to probe the physics that connects quantum theory and general relativity."
Re:That's quite a leap (Score:5, Interesting)
The propulsion system should use extra-solar system harvested hydrogen atoms (they are like 1 H atom per cubic mile or something like that), accelerating it to near speed of light through special cyclotrons, then as the relativistic mass takes over and things get out of sync, special coiled linear accelerators continuing it, and you can get almost any kind of mass out of each atom, and get a great propulsion kick, impulse out of each, for rotation and speed control, or for further accelerating, being mindful that halfway through the trip you have to start decelerating, and such propulsion would still beat the simple light propulsion by orders of magnitude, because the impulse per energy expanded ratio is much better than with simple light. It's true that you're creating mass out of energy as you build the mass of each proton up, and shooting off pure energy as mass is equivalent to shooting off pure light as mass, so there is an optimum velocity, optimum ejection speed dependent on the economics of harvesting each atom from the really thin galactic vacuum vs. economics of not building up too much relativistic mass into it and wasting energy as mass, as in case of a light propulsion. You may have to resort to pure light propulsion in case you cannot find any hydrogen atoms whatsoever within 100 cubic miles or so, such as intergalactic space.
In closer quarters, on rotating cylinder space modules near Earth orbit or Lunar orbit, such propulsion, including light propulsion is pure absolute economic waste, compared to specific impulse gained per size (mass, volume) of the drive, as we have plenty of matter to waste, if nothing else, solar wind close to the Sun is pretty matter rich, visible with things like Aurora Borealis. In particular even a cyclotron drive on a rotation cylinder station may not be the economic optimum to align solar panels and control orientaton, rotation speed and orbit, but instead a liquid oxygen/calcium metal energy cash could be used near the Moon and on the Moon's surface. See life down here on Earth uses ATP (high energy adenosine tri-phosphate) as the energy cash, and all processes within all lifeforms respect the resource limit of energy cash, and all processes either generate ATP with food or light energy from ADP (low energy adenosine di-phosphate) plus P, phosphoric acid, APP + P + energy ---> APPP, or APPP ----> APP + P + energy. So, similarly, near
Re:That's quite a leap (Score:2, Interesting)
Re:That's quite a leap (Score:4, Interesting)
As nitrogen is scarce, but hydrogen and helium are abundant in outer space, diluting oxygen harvested from comet rocks could be done, but not with hydrogen that forms an explosive mixture with oxygen, but with helium. The helium might have to be fusion generated from the harvested hydrogen, if nothing else, through cyclotron or energy inefficient portable neutron generator bombardment. And everyone would get used to the chipmunk sound of helium balloon inhalation you can hear down here on Earth.
Also, communication with the speed of light would take a few years to go back and forth, to exchange hello's, draining quite a bit of power from the ship for dish/antenna use, and in case the crew on this ship messes up and ends up in deep doo doo sending out an SOS to us, we can reply to them with the phrase/video transcript from Mad TV's Dolla Bill Montgomery's Real Motherf****in Talk Mother's Day episode, "Talk to the hand, you're on your own, motherf****!" https://www.youtube.com/watch?... [youtube.com] We can give them advice, but not much else, advice they have to wait 4-8 years for to arrive. For psychological reasons, a reality show transmitted from them and programming transmitted to them would be neat, each without waiting for a reply to arrive, at least not reacting to one for the few years it takes to transmit the message. Their internet ping timeouts would have to be set to the corresponding few years, if
Re:That's quite a leap (Score:4, Interesting)
Four replies to oneself. I think it's a new slashdot record for a non-AC poster.
More importantly, you need to review some of the things that you wrote, because they don't pass the smell test. An example is the suggestion of using beryllium. There are less than 100 kt of mineable beryllium in the world, and most of that is needed for other applications (nuclear, ceramics, etc.). Beryllium exposure also does very nasty things to human biology. 0 points for practicality.