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ISS NASA Space Science

Dragon Capsule Could Be 1st Private Craft To Dock With ISS 178

thomst writes "Space News reports that NASA has given tentative approval for SpaceX to combine the two remaining flights designed to prove the Hawthorne, Calif., company can deliver cargo to the international space station, according to William Gerstenmaier, NASA's associate administrator for space operations, although formal approval for the mission is still pending. If NASA does approve the plan, SpaceX's Dragon capsule would be the first civilian spacecraft actually to dock with the International Space Station. According to NASA spokesman Joshua Buck, the current plan calls for SpaceX to launch a Dragon capsule aboard a Falcon 9 rocket on Nov. 30, which would then rendezvous and dock with the space station on Dec. 7 — a day that would live in spaceflight history."
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Dragon Capsule Could Be 1st Private Craft To Dock With ISS

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  • by tp1024 ( 2409684 ) on Tuesday July 26, 2011 @09:30AM (#36882604)
    Proving reliability will be the main task of cargo delivery. 13 unmanned flights of the Dragon would be enough to do that. For perspective: that's twice as many unmanned test flights as the Shuttle, Apollo and Gemini had among them. However, first SpaceX must deliver. (That doesn't mean that none of those flights must fail. But they better come up with some very good analysis if one does. Especially, whether the crew could have bailed out or not.)
    Reuse is a non-issue both in terms of cost and material. First of all: The Dragon is as reusable as the Shuttle. But: it requires a much smaller (probably non-reusable) rocket to get into space. What you see under the bottom line is not what you reused, but what you didn't.

    Launching an 80t Space Shuttle (plus fuel and payload) wastes 2x90t in solid rocket boosters (plus fuel). Those could in theory be reused 20 times, but weren't (it's too costly to do). But even if those numbers had been reached, it would amount to 9t per flight. (In practice, it's on the order of 40t per flight). Then, you have to account for the external tank - 26.5t. The empty Falcon 9 weighs on the order of 30t - including tanks and engines to launch a 3t (or so) Dragon (plus fuel and payload).
    So yes, the reuse quota is worse - but the amount of waste is less.

    The shuttle also wasn't exactly maintenance free. Especially the SSME (main engines) had its turbo pumps replaced regularly and the engines themselves as well. 46 SSME were produced for 135 flights at a cost of $45mio per engine or $15mio per flight (plus cost for spare parts, disassembly, reassembly, check-ups of the engines after each flight etc. - no idea how much that cost, but given the labor-intensity of those tasks, it must have been millions for each flight). Add to that the cost of the solid rocket boosters, handcrafted tiles to replace the old ones etc ...

    But worst of all: The shuttle weighs 100t (with max payload) and carries only minuscule amounts of fuel itself. It can't reach higher orbits. In fact, the orbit that the Shuttle can reach is so low that the friction of the atmosphere necessitated regular lifting maneuvers that can now finally be reduced by 70-80% (fuel comprised a large part of the payload that the ISS has required so far) - by lifting the whole station into a 100km higher orbit (which is a trivial orbit to reach for any spacecraft, except for the Shuttle).
    It's even worse for Hubble. It's in such a low orbit, that observations with it have been described by astronomers as akin to riding a bicycle over a cobble-stone road while trying to hold a telescope steady. And that's before you consider that it regularly has to deal with a huge planet getting into its field of view during observations. It could never reach its full potential (and you've seen what it did despite that!) And that wasn't at all necessary. The KH-11 spy satellites that have very similar dimensions and exactly the same optics as Hubble were flown into space using a Titan IIIE missle - which could have brought the telescope into a much higher and reasonable orbit.

    For any regular rocket reaching a somewhat higher orbit is no problem because you get rid of the 2nd stage when you're in orbit. You can even replace the payload by a 3rd stage(*) - but the Shuttle itself is the second stage (minus the external tank, weighing about 1/3 of the shuttle) and has a hard time getting rid of itself.

    (*) Yes, you can do that with the shuttle, but the results are laughable compared to the insanely huge rocket you're launching to do that. What's the point of launching a 2600t Shuttle in order to place the same amount of payload into a geostationary orbit as a 300t Soyuz rocket? Most of all: what's the point of risking the lives of 7 people to do what is regularly done with unmanned rockets?

Prototype designs always work. -- Don Vonada