Originally posted by sonhouseWell.. hopefully I didn't go totally wrong somewhere.
So a rail service has started on the moon in lunar equatorial region and the train is solar powered, 10 meters wide and 1000 meters long. At the time, solar cells have reached 75% efficiency and last practically forever. The train wants to keep itself at local lunar noon so it the sun is always straight up for maximum solar power and stops and picks up pass ...[text shortened]... much power does the train generate and how fast does it have to go to stay at local lunar noon?
Originally posted by talzamirSpot on except you said 10Gw for the power, it should be 10 Mw.
Well.. hopefully I didn't go totally wrong somewhere.
The radiation from the sun at 1 AU distance is about 1,400 W / m^2. As there are 10,000 square meters on the train to radiate on, that's a power of 14,000,000 W. Given the 75% efficiency and these being ballpark figures, 10 GW seems a sufficiently accurate figure to represent the power generated.
T ...[text shortened]... . So the train needs to travel at a pace of about 400 km / day, or 16.6 km/h, or about 10 mph.
Originally posted by talzamirCan be a magnetic sling also, like a linear electric motor. If you confine the acceleration to 1 g, it looks like you need 289 odd Km long runway. 10g, 28.7 Km, 100g, 2.8 Km. I divided 2375 m/s by 9.8 which gives a time of 243 seconds or so to get to that velocity at one g, then the old S=(AT^2)/2 (9.8*243^2)/2= 289340 meters or 289 km or about 180 miles. Sound about right?
Oopsie. 10 MW of course.
The moon's mass is about 7.36 x 10^22 kg and the gravitational constant is 6.673 x 10^(-11) m^3 kg^(-1) s^(-2), and moon's radius as said before 1.7374 x 10^6 m. Liftoff happens when the centrifugal force exceeds gravity.
m v^2 / r > m M G / r^2
v^2 > M G / r
v > (M G / r)^(1/2)
Which is about 1,680 m/s, or Mach 5, not th ...[text shortened]... il in the first place and keeping it clear and safe of space debris presents some challenges.
Originally posted by talzamirThings are looking up in that regard. The latest is the finding of 22% water inside at least one crater on the south pole of the moon where they are in constant shadow of the sun so the temperature inside the crater could be 100 degrees Kelvin or so, so no water ever escapes. The idea there is to use the water for drinking, industrial processes and using solar energy, to split the H2 and O2, giving the best chemical rocket fuel or for use in fuel cells for power. Once you have a city on the moon with industrial capacity you don't need to haul crap up from the Earth so often which saves tons of money and makes it much more viable.
With the track record of humanity in using inventions that could be beneficial to everyone, I expect that the slingshots would end up used as a sort of field artillery. But yes, the peaceful applications sound fascinating and plausible. Obviously getting to the moon in the first place to build the thingy won't be easy or cheap, but then, according to a site needs to be deccelarated so it won't burn in the atmosphere.
Interesting times for sure.
Originally posted by talzamirIt's not space shrapnel we need to worry about, it's radiation from solar flares and ions from those flares. It can be deadly if you are caught out in a solar storm aimed at Earth and moon. The moon does not have a magnetic field to deflect solar storms like the Earth does so the nasty stuff slams right down on the surface, so you better have about 10 meters of dirt between you and the outside.
Underground housing on the moon would make sense anyhow, as it would probably be to be bombarded with space shrapnel in near-vacuum 24/7 no matter how much kevlar one has on the roof.
The odds sound good that we'll get to see people living on the moon for prolonged periods of time - and with exit from the moon fairly easy and energy issues straight-forwa ...[text shortened]... to cut the water molecules to pieces.. there's hope. We shall hopefully see how this goes. =)