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Is SpaceX A Viable Option in Space Exploration?

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  1. Jan 19, 2015 #1
    Hey guys, I'm not sure if this would really fit into any specific area of the site. But I guess I was just wondering your opinions on SpaceX, and private spacefaring corporations in general. I'm not even going to get into Virgin Galactic or Mars One. :P
    In terms of technological advancements and the future of humans in space, do you think that companies like SpaceX are going to lead the way, or are NASA, the ESA, and other publicly-funded programs still the answer?
     
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  3. Jan 19, 2015 #2

    Bystander

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    Is there enough "disposable income" to support sufficient "novelty revenue" to cover the upfront investment? No. "Be the first in your neighborhood to host a super bowl party in outer space," just isn't going to be a long term seller. Zero-g manufacturing and materials processing? Nah.
     
  4. Jan 21, 2015 #3

    mheslep

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  5. Jan 21, 2015 #4

    Evo

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  6. Jan 21, 2015 #5

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    They're trying to bring it down a la Flash Gordon?
     
  7. Jan 21, 2015 #6

    mheslep

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    Far as I know, until now everyone else disposes of their first stages post launch. Little to lose by trying.
     
  8. Jan 21, 2015 #7

    mheslep

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    Aye, and they've done it near ground.

     
  9. Jan 21, 2015 #8

    Evo

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  10. Jan 21, 2015 #9

    mheslep

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  11. Jan 21, 2015 #10

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    Okay, invest in the extra fuel to recover a high-dollar engine, rather than using a disposable solid fuel booster at (presumably) lower cost. Gain the advantage of rebuilding the high-dollar engine for somewhat less than original cost, and gain maybe a second or third flight per engine. This is preferable to dropping it in the water by parachute and using a flotation device while towing it back for rebuild "how?" I'm having difficulties seeing the economic advantage.
     
  12. Jan 21, 2015 #11

    mheslep

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    From googling, advantages of liquid fuel over solid:
    • Greater efficiency of liquid fuels, e.g. Isp 286 for solid like ammonium perchlor and 452 for liquid H2/O2
    • No throttle for solid. I gather, in order for a vehicle to obtain orbit efficiently it must delay max thrust until after maximum dynamic air pressure.
    • Longer fueling time for solid, especially, I suppose, if its been in the ocean, and so is a disadvantage for high volume reuse.
     
  13. Jan 21, 2015 #12
    They have become a significant player in the launch services industry with no signs of going away. In addition to this SpaceX seems to be attempting real practical space innovation with their recent landing attempt.
     
  14. Jan 21, 2015 #13
    Even parachuted, I think a 14 story rocket could damage itself crashing into the water, and a chute system also carries weight and complexity I suppose. I'd be curious to know more about the chute vs. powered decent tradeoff as well.
     
  15. Jan 21, 2015 #14

    mheslep

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    Shuttle dropped its SRBs by parachute into the ocean for years and recovered them for reuse. With a simple engine, no fuel mix and turbo pumps that would not like sea water, an SRB sounds like a good candidate for sea recovery. There are videos of shuttle SRB descent all the way to splash.
     
  16. Jan 21, 2015 #15

    phinds

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    As I understand it this has zero to do with space exploration and 100% to do with giving Google new ways to get people connected to the internet.
     
  17. Jan 22, 2015 #16

    cjl

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    There are also some reliability benefits, as well as benefits to the launch environment. Solids are unstoppable once started, so if a problem is detected in the moments before liftoff (as has already happened with SpaceX), you can't really do anything about it other than lose the vehicle/payload. They also can't be test fired (and SpaceX likes to test fire their stages prior to each flight).

    In addition, solid motors generate substantially more vibration than liquid motors for a given thrust level, which is hard on payloads and structure, and their burn time tends to be rather short (so they don't tend to be particularly good for imparting a lot of delta v, though they are good for getting a heavyish rocket off the ground that would otherwise have a mediocre thrust to weight ratio).

    Interestingly, your second point isn't a particularly big deal, since solid fuel motors can be tailored to give any thrust profile you want (and with knowledge of the vehicle ascent profile, you can delay peak thrust until after max q).
     
    Last edited: Jan 22, 2015
  18. Jan 22, 2015 #17

    cjl

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    And those were thick, ultra high strength steel and weighed 200,000 pounds each (empty), and they still had to be checked for roundness and carefully refurbished after each landing. The Falcon 9 first stage is much weaker (it doesn't have to hold 800+PSI inside of it), much lighter (~40,000 pounds empty), and much more prone to buckling.
     
  19. Jan 22, 2015 #18

    mheslep

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    After rewatching an SRB recovery, that is no surprise. I thought ocean impact would be max stress, but now I think the aerodynamics on descent before 'chute and the temperature shock from the water would be most likely to do damage.
     
  20. Jan 22, 2015 #19

    mheslep

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    If SpaceX masters 1st stage retro descent and reuse, it occurs to me they can afford to use more sophisticated materials for structural support and engines. For example, carbon fiber may make sense for a first stage that is not fated to disintegrate or find the ocean bottom. Then the SpaceX payload-mass/orbit increases, cost/launch decreases, and all at once they have large competitive jump on the rest of the industry.
     
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