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Open Source Space Linux

Hackers In Space: Designing A Ground Station 95

Posted by Unknown Lamer
from the dod-responds-with-orbital-defense-platform dept.
An anonymous reader writes with some new information on the happenings of the Hacker Space Program. From the article: "At the Chaos Communication Camp 2011 Jens Ohlig, Lars Weiler, and Nick Farr proposed a daunting task: to land a hacker on the Moon by 2034. The plan calls for three separate phases: Establishing an open, free, and globally accessible satellite communication network, put a human into orbit, and land on the Moon. Interestingly enough, there is already considerable work being done on the second phase of this plan by the Copenhagen Suborbitals, and Google's own Lunar X Prize is trying to spur development of robotic missions to the Moon. But what about the first phase? Answering the call is the 'Shackspace,' a hackerspace from Stuttgart, Germany, who've begun work on an ambitious project they're calling the 'Hackerspace Global Grid.'"
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Hackers In Space: Designing A Ground Station

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  • Re:these guys.... (Score:3, Interesting)

    by Anonymous Coward on Tuesday February 21, 2012 @05:24AM (#39108037)

    If they're trying to push a large amount of bandwidth through small, cheap low earth orbit satellites I believe they're going to run into some fundamental engineering constraints (satellite power budget, shannon limit, the fact that two axis tracking antennas are expensive).

    They're not. At this point they aren't even looking at bi-directional communication. Stuff like simple downlinks of textual data (news, emergency info, etc). There are already a few satellites that do very similar tasks, like the FUNcube.

    Nobody is suggesting or attempting satellite internet access.

  • Re:Money (Score:4, Interesting)

    by sFurbo (1361249) on Tuesday February 21, 2012 @05:46AM (#39108115)
    The question to answer that question is, will it cost billions of dollars? Copenhagen Suborbitals [copenhagen...bitals.com] are proving* that space travel can be a hobbyist project. Granted, there is a long way from suborbital to the moon, but just getting where they are now would have been called impossible twenty years ago.

    Another point is that hacker space activity usually is more about the process than the goal. So what if they never put a man on the moon, if they put one in LEO and have fun on the way, that's a win.

    *Pending their actual succes, and assuming the capsule will not burn on reentry.
  • Re:Lunar cable car? (Score:4, Interesting)

    by tragedy (27079) on Tuesday February 21, 2012 @08:44AM (#39109207)

    The moons orbit is oblong, so you'd have to have some method by which the cable length could change. You need a cable strong enough to support its own weight. Gravity drops off as altitude increases by the formula g = 9.8 m/s^2(r/r+h)^2 (r is the radius of the earth and his your height), so it's 100% at the surface (very slightly less if you're at the equator), 96.937% 100 km up, 94.012% 200km up, 85.990% 500km up, 74.730% 1000 km up, 57.955% 2000 km up 37.770% 4000 km up, 19.678%. 8000 km up and so on. Even at geosynchronous orbit altitude (which may or may not be relevant depending on how this cable is being managed) where gravity is 2.287%, the average weight of the 35,800 km of cable to that point is about 15.172% of its Earth weight. Out at 325,000 km, which is about the distance of the L1 point between the Earth and the moon the gravity is .037% of what it is on Earth (not at the actual L1 point where it's cancelled by the moons gravity, this is just an approximation, not taking all forces into account) the average weight of the 325,000 km of cable is still about 1.932% of its Earth weight. So, if you need to stretch a tether out to Geosynchronous orbit, it needs to be strong enough to hold 15.172% of the Earth weight of 35,800 km of material. If the tether masses 1 kg per kilometer, that means it has to be strong enough, at that thickness, to hold the Earth equivalent of .15172*35,800=5431.576 kilograms. Tapering the tether can help, of course, but we still don't have any materials strong enough. For the L1 point, it's equivalent to holding 6279 kg on earth with that size cable.

    Then there's the problem that the moon isn't in a geosynchronous orbit, so you can't tether the cable at a stationary point on earth. The poles aren't stationary, so the best you can do is anchor to tower, built on a train on a huge circular track around one of the poles.

    Of course, the cable doesn't actually need to be a straight line to the moon. If you could make a tether to geosynchronous orbit, you could then have another tether from there to the moon. For that matter, you might be able to build a 60,000 mile tether that circles the earth at slightly greater than orbital speed (maintained by propellant brought up from earth on the space elevator) then attach multiple secondary tethers that loop around the earth towards the poles where they connect to smaller tether rings suspended above each pole with a station suspended in a web in the middle and a variable length tether that need only be a 100 km long or so (and could be supported by dirigibles through a good portion of the atmosphere) that tethers to a polar base station. You could take an elevator up at the pole, then down along one of the loops to the equatorial ring. From the equatorial ring, you could suspend another ring further out, or perhaps just spokes out to additional stations. From one of those, you could potentially even build a tether all the way to the moon and set it up on an orbit that jump ropes the Earth. Of course, the tether all the way to the moon would hardly be necessary. Once you're out to the orbital ring, if it's fast enough, you can just drop off and fall toward the moon, it would be a heck of a lot faster than pulling an elevator car along 400,000 kilometers of tether. At the moon end you could have another space elevator. The one at that end could use the same equatorial ring with polar elevator trick, but the moons smaller size and lower gravity mean that you could actually have a plain old space elevator right to the surface.

    Of course, the above idea might have a lot of problems. Getting that giant orbital lasso trick to actually work might be next to impossible. Also, such a long tether going around the entire Earth is going to have to be carefully designed. It could run into some really interesting electrical effects that could instantly fry it. On the other hand, they could also be used as a method of powering the whole thing. In any case, it's a massive endeavour. You would have to start

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