SpaceX's Grasshopper

Discussion in 'Science and Technology' started by Wanderlust, Sep 22, 2012.

  1. gturner

    gturner Admiral

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    We're in agreement, arguing the same points. The SuperDracos have vastly more than enough through for the mission, but the Dragon doesn't carry nearly enough fuel to give a mass ratio to carry it out without adding a lot of external tankage. The reason the cosine losses are significant is that it's much more efficient to just reorient a nozzle than add all the extra fuel mass to compensate for the inefficient mounting, in both the descent stage and the ascent stage, which itself would require a larger descent stage tank.

    And on top of those losses, as you mentioned, the SuperDraco's nozzle is probably underexpanded even for sea-level operation.

    What the Dragon needs for a lunar landing is a dedicated, fully expanded SuperDraco (or cluster of Dracos) aligned with the thrust vector, along with the removal of the eight unnecessary SuperDraco abort engines and the heat shield, the addition of landing legs, an airlock, vastly more fuel, a high-gain antenna, and either windows or external cameras for visibility during the landing phase.

    We've probably done something like this before, slightly altering the Apollo command module into the LM by removing the GNC computer and some solenoid valves and attaching them to a different vehicle.
     
  2. sojourner

    sojourner Admiral Admiral

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    So, basically, rip off everything and start with the inner pressure vessel from a Dragon. Might as well do it right and just clean sheet it.
     
  3. gturner

    gturner Admiral

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    Yep. That seems like the best approach in terms of schedule, perhaps leaving the attitude thruster system completely intact just because it's already adequate (I think) and thus would save lots of mounting and software changes. However, if the thruster exhaust is going to impinge on the tanks then maybe they'd repeat Grumman's idea of mounting the attitude thrusters on struts. If the schedule isn't critical then further optimizing is probably a good idea (visibility, entry/exit, internal tankage, small breakfast nook, etc).

    On the flip side, leaving the thermal protection and parachutes in place would give you a lifeboat useable all the way to splashdown, and if you did just add extras to an existing Dragon you could probably execute the mission with one craft, but with severe performance penalties because your Earth Orbit Insertion fuel would also have to ride all the way down to the moon and back up, unless left in lunar orbit, in which case you've not saved any lunar rendevous requirements.

    Given the Falcon9H payloads, you're not going to execute the mission in one launch, so you might as well use most of the Apollo mission profile with multiple launches and LEO rendevous.
     
  4. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    Not really. Of course that a Moon lander based on the Dragon will be a completely new vehicle. That goes without saying. I was contemplating the Dragon landing on the Moon as-is because it's good food for thought.

    However, the know-how is there, and SpaceX have already done their homework in building such things. Designing a new moon lander for them will be significantly less difficult than building a capsule from scratch.

    Guidance systems – done.
    Major engineering hurdles – solved.
    Propulsion – only little rework required.
    Interior – I'm pretty sure that they'll nearly CC it.

    I'm not sure about the figures, but if I remember correctly, designing Dragon costed $300-400M*, building one vehicle costs $100M, and designing the SuperDraco cost a couple hundred million at most. My bet is that the moon lander design will be in the SuperDraco price range. At worst.

    I'm also willing to speculate that expansion to landing on Solar system bodies has been considered in the design and it might require a lot less work than we're thinking, but maybe I'm giving them too much credit here.

    * Or was it $600M? I'm not sure if $600-700M was the price for the Dragon and Falcon 9 combined or for each one of those. I don't remember in which interview Elon said that to check. :(
     
  5. gturner

    gturner Admiral

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    If they're going to do a clean-sheet design then I think we'd all have some suggestions. Large solar panels would greatly extend surface missions, and the capability to have a crew of more than two would be nice (can you imagine what a millionaire would pay to walk ON THE MOON?!) as would a slightly more comfortable sleeping area. And in lunar gravity they can eat normal food, cooked normally, so a little stove (powered by the solar panels) where they could flip an egg in 1/6th G would probably be the most-watched egg flip in the history of live television.

    Another thing I think we would all agree on is a better moon-buggy, perhaps with both fuel cells and solar/batteries so that it doubles as a tele-operated rover after the astronauts leave. Perhaps the greatest omission of Apollo was putting something as big and robust as the moon buggies on the moon, fully equiped with cameras and high speed uplinks, and not having each of them creep around for a few more years, covering hundreds of times more area than the astronauts reached.
     
  6. sojourner

    sojourner Admiral Admiral

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    Their not. Elon has no interest in the moon. So unless NASA contracts them to go to the moon, this is just spitballing.
     
  7. gturner

    gturner Admiral

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    Elon says he has no interest in just going to the moon, because we've already done that and reruns are never as good, but he does say a lunar base would be significant.
     
  8. Gary7

    Gary7 Rear Admiral Rear Admiral

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    If a space vehicle production company decides to launch one of their products, are they by law required to send them off from a government certified and operated installation?
     
  9. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    Hell no. Just take the landing mechanism from the grasshopper (and probably adapt some of its control software too) and put nine tons of hydrazine on it. Then put four SuperDracos underneath it with gimbals and expansion nozzles, and attach that module to a Dragon's heatshield.

    Of course, at that weight and that propellant level it wouldn't be able to take off again. I kind of expect that would be half the point.
     
  10. sojourner

    sojourner Admiral Admiral

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    Launches are regulated by the FAA if over a certain altitude. Launch sites do have regulations that must be met, but do not have to be government run.

    Example: SpaceX plans to launch Grasshopper (to a certain altitude) on test flights from it's McGregor, TX facility.
     
  11. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    Holy shit. We're getting there. Slowly but steadily.

    [yt]https://www.youtube.com/watch?v=B4PEXLODw9c[/yt]
     
  12. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    SpaceX continues to reinvent the wheel, with spectacular results. Seems they're a little more than halfway to where the DC-X was when it was cancelled, which -- this being SpaceX -- probably puts them two to three years away from an operational test flight.
     
  13. sojourner

    sojourner Admiral Admiral

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    It's a great flight! I can't wait to see them do an "end over end" maneuver.
     
  14. publiusr

    publiusr Rear Admiral Rear Admiral

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    Lands the way God and Robert Heinlein intended.

    That's taller than DC-X ever was, right?
     
  15. Unicron

    Unicron Continuity Spackle Moderator

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    We should build one of these, just for fun. :biggrin:
     
  16. Hyperspace05

    Hyperspace05 Commodore Commodore

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    Today GrassHopper made its final(?) and perhaps dramatic flight, to a height 744 meters - although the amazing point of view in this video is was makes it truly spectacular!
    [yt]http://www.youtube.com/watch?v=9ZDkItO-0a4&feature=youtu.be[/yt]

    The next VTVL test flights will be made by the next follow up vehicle (being assembled and tested now) which is much closer to an actual flight configuration - taller and with leaner legs.

    BTW, the flight before this (didn't see it linked here) made a very impressive lateral/sideways movement:
    [yt]http://www.youtube.com/watch?v=HXdjxPY2j_0&feature=youtu.be[/yt]
     
  17. publiusr

    publiusr Rear Admiral Rear Admiral

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  18. Hyperspace05

    Hyperspace05 Commodore Commodore

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    Now? That was two years ago, and a lot smaller than this vehicle. I'm excited about Blue Origin as well, but they still haven't flown their follow-up vehicle. (As far as I know)

    Anyway, the follow-up of GH will fly soon - and it will be much closer to the final booster stage. 30% taller, folding light-weight legs, capable of reaching 100km altitude. It might make its first test hops around new year. :bolian:
     
  19. Hyperspace05

    Hyperspace05 Commodore Commodore

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    FYI - Recently some images surfaced of the next "Grasshopper" test bed, named "F9R-Dev1": (click for higher resolution)
    [​IMG]

    Here is a comparison picture to illustrate how much larger the new vehicle is than Grasshopper:
    [​IMG]

    And the next Falcon 9 launch - this weekend - will be the first one flying with legs attached. The idea is to test a water soft landing, to build experience towards land landings:
    [​IMG]
    Now that is a sexy rocket! :drool:
     
  20. sojourner

    sojourner Admiral Admiral

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    It's too bad it's a night launch. Will be pretty difficult for them to get good images of the water landing.