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SpaceX Reusable Mega-Rocket Plan Is Simplly Amazing

Discussion in 'Fred's House of Pancakes' started by bwilson4web, Jan 29, 2015.

  1. bwilson4web

    bwilson4web BMW i3 and Model 3

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    #1 bwilson4web, Jan 29, 2015
    Last edited: Jan 29, 2015
  2. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Concur.
    I think that Elon said that our current technology is like throwing away the 747 after each transatlantic flight....
     
  3. bisco

    bisco cookie crumbler

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    how do they get it to hover like that?:confused:
     
  4. FL_Prius_Driver

    FL_Prius_Driver Senior Member

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    Two methods. One set of balancing thrusters are at the top of the boosters for keeping the top of the rocket balanced above the engine. The second method involves vectoring the engine outputs so the rocket can scoot sideways (much like how a Segway keeps a person upright and moving in the desired direction). If you look closely at most rocket engines, they are gimbaled to vector the thrust. The amount of gimbaling is very small, so the difference between a fixed rocket engine and a gimbaled rocket requires looking very close.
     
  5. fuzzy1

    fuzzy1 Senior Member

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    Isn't that the reason NASA dumped the single-use Saturn launch vehicles of the Apollo era, and designed the reusable Space Shuttle for all future manned flight? Each Shuttle was to be reusable hundreds of times, with quick turnarounds of a couple weeks, and very comparatively cheap, about $100 per payload pound.

    Oops, it didn't quite meet those goals. OK, not even close. OK, not even within sight.
     
  6. bwilson4web

    bwilson4web BMW i3 and Model 3

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    There were several things about this approach that pique one's curiosity:
    • Strap-on return to KSC, first stages - this makes sense as even the old, solid rocket boosters were within camera range of Kennedy. Essentially flying a more vertical path, their mission is to get the remaining stages and payload above the atmosphere so they can continue to accelerate to orbit . . . within limits. So once free of the upper stages, the strap-ons only need enough fuel to reverse course momentum; use re-entry drag to slow down, and; final maneuvers to land. This is practical with a small fraction of fuel. Less fuel if a ballistic path can be followed to a down-range, landing point.
    • Center return to KSC, second stage - this is a lot harder because the center stage and the upper stage(s) needs to achieve a significant fraction of orbital velocity. The kinetic energy increases by the square of the velocity as does the amount of fuel needed to return to launch site. Worse, this stage has significantly more kinetic and potential energy so it needs to fly a 'soft' re-entry path to avoid excessive heat. But if this stage can land on a barge down range, significantly less fuel is needed. Better still, launch from the Southern tip of Texas and land the center stage in Florida or a Gulf of Mexico platform. Hummm, even the strap-on stages might land on another pair of Gulf platforms.
    • Upper stage(s) - by now the potential and kinetic energy are so high that re-entry energy exceeds ordinary, light-weighting. But this is a much smaller vehicle so single use is 'less bad' and a solid fuel stage makes sense.
    So if the center and outer stage modules are identical, the flight paths can be modeled with an optimum distribution of landing sites that minimize offsets from down-range distances. Use the down-range, distances to pattern match for optimum locations. Land based, coastal positions approached from the ocean are best; platforms in shallow water near land are next, and; overflight of populated land is least desirable. Flying along the coastal areas of the Gulf of Mexico would be nice but then there is the population on the Florida peninsula.

    Bob Wilson
     
  7. Trollbait

    Trollbait It's a D&D thing

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    What makes a splash down in the ocean undesirable? The boating logistics?
     
  8. GregP507

    GregP507 Senior Member

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    Anything is amazing compared to a government-run enterprise.
     
  9. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    I could take a swipe at 'government efficiency' but that would be a cheap shot WRT the Shuttle. The program was hideously expensive but it was a good bridging technology between MILSPEC and COTS, and we needed the lift capacity. I remember being somewhat inconvenienced in the Atlantic during the Cold War after Challenger Disaster.

    I (now) think it was a good decision to Canx the program and finish the transition to COTS for pickup truck missions....necessity (and greed) being excellent motivators.
     
  10. GregP507

    GregP507 Senior Member

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    Are you saying that some good always comes out of disaster?
    I agree.
     
  11. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Not always.
    Defecation will always occur.
    The trick is to learn from tragedy.....something that humans don't always do.

    I was putting the cost of the shuttle program into context.
    People don't always noodle out that the program lasted almost 40 years, and although you can never say that it was a cheap way to put satellites into LEO, that's not all we used the Shuttle for.
    We now have the ability to do resupply missions to the ISS but the Shuttle programme was pretty important in building the ISS, and also for lofting the GPS constellation and other military communications and....ah.....GIS missions.
    One could also mention satellite repair, but that was always a NASA "play pretty" although the Hubble repair and upgrades contribute to the Shuttle's ROI.
    You can do a lot with de-milled ICBMs, but there were many experiments throughout the 80's and 90's that were performed before the ISS started spooling up in 98 that you could only do in MIR or on a shuttle.
    Sometimes you need humans doing the stick and rudder thing up there.

    Then?
    There's the welfare aspect of NASA.
    I know it's not as groovy to spend money on beans, bullets and gas as it is to load up 142,345,384 food assistance cards, or build bicycle trails but there is an ROI to the space programme that does not always get its due credit.
    The Shuttle's external fuel tank (ET) costs about $50,000,000, (about $775/lb) and it's the biggest part of the orbiter that we threw away. That's about 7 Gigabuks for the whole programme, and there was always people yammering about spending a little more in fuel and parking them in orbit, but that's not the point.
    We didn't throw that money away.
    It's like any other government spending program.
    In addition to purchasing exotic metals, sensors, transportation infrastructure, R/D, etc.....those 7 billion bucks also bought home mortgages, paid taxes for schools and roads, and bought college degrees and braces.
    If you've never spend any time at P-Can, or Houston you might not know that most NASA personnel and contractors are not white collar workers....(believe me!)
    Just a little extra food for thought.
    If you insist on deficit spending...
    Why not get an iconic orbiter programme out of the deal? :)


    Do we need it now?
    Naaaah, and the absence of the United States to put beans into space is being addressed more efficiently with COTS technology.

    Did we need it in 1982? 1992?
    Oheckyeah!!
    I think so.
    I think that the people who ran the country in 1982 thought so too.

    YMMV
     
    #11 ETC(SS), Jan 30, 2015
    Last edited: Jan 30, 2015