Obama Space Plan: Return to Moon: "No Go"

Discussion in 'Science and Technology' started by Johnny Rico, Sep 8, 2009.

  1. Lindley

    Lindley Moderator with a Soul Premium Member

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    That's exactly what they're doing.
     
  2. sojourner

    sojourner Admiral Admiral

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    Yes, but SpaceX only got paid that $300million for reaching agreed upon milestones. Kistler failed to reach milestones. This is wholly unlike the X-33 venturestar program for example where LockMart was just given more money to keep working despite setbacks.

    NASA does, the problem is that Ares I is such a mess that they have had to constantly redesign Orion to reduce weight. Orion is not the problem, Ares is.

    Alot of people decry a capsule over a plane here. You have to remember that a capsule is more efficient at getting a useable payload to orbit. Wings are just dead weight on the ride up that reduce payload weight. Until technology reaches a stage (and no, it's not there yet) where an SSTO spaceplane is feasible, the best way to get crew to orbit is in a no nonsense capsule.
     
    Last edited: Jan 30, 2010
  3. ConRefit79

    ConRefit79 Captain Captain

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    The wing span can carry fuel.

    I don't like capsules for putting people in LEO. Space junk is already a big problem. Now if all the stages and the command module fall back to Earth, that is resolves the junk issue. I would still prefer a system that if almost completely reusable. That is why I prefer having a smaller version of the shuttle. at the top of the stack. It would have what would be service module built in.
     
  4. Marc

    Marc Fleet Admiral Admiral

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    which can ad complexity to your design
    - fuel system to carry get the stuff to the engines,
    - the need to insulate it unless you're able use something other than liquid hydrogen etc.
    - a venting system to make sure the tank is totally empty before re-entry
    - the possibly that the design changes to make use of wing fuel tanks results in a weight penalty such that you end up having to burn fuel to carry fuel.
     
  5. RobertVA

    RobertVA Fleet Captain Fleet Captain

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    The problem with reusable spacecraft for lunar and interplanetary missions is slowing down to return to low Earth orbit. Earth's gravity would accelerate such spacecraft to about 25,000, but low Earth orbit needs to be much slower. The deceleration whould require heavy amounts of propellant that would have to be lifted from Earth or the Moon (easier - but still requires a additional propellant to lift the propellant for decelerating into orbit). Aerobraking might reduce the deceleration propellant needs somewhat, but would probably require heat shielding and propellant to adjust the spacecraft's orbit after the aerobraking maneuver (to rendezvous/dock with other orbiting facilities).

    Any weight/mass required for the end of the mission is multiplied several times getting the initial launcher off the ground, even if crew and fuel are launched in separate vehicles. Thus the Apollo and Constellation programs' small re-entry vehicles and repeated abandonment of equipment like the upper launcher stages, descent modules (used as lunar launch pad), ascent modules and service modules. All that reduces the demands on re-entry shielding and propellant needs leaving the moon's surface, leaving lunar orbit.
     
  6. Lindley

    Lindley Moderator with a Soul Premium Member

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    That's true presuming a (more or less) straight-line course. Orbital dynamics being what they are, other options are available; but they require far more time.

    Whatever orbit you're in, you can raise yourself to a higher orbit by speeding up slightly, and you can lower yourself to a lower orbit by slowing down slightly. Since lower orbits have shorter periods, this leads to the counterintuitive fact that in order to overtake someone else in orbit, you need to first slow down, and then pass them, and then speed up again to return to their orbit.

    On return to Earth, you could arrange a trajectory which allowed you to decelerate gradually over a long time with something like the VASIMR drive, rather than needing a standard rocket. But that trajectory would necessarily take longer, perhaps much longer, to get you into LEO.
     
  7. sojourner

    sojourner Admiral Admiral

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    Not very well. most of the space will be taken up by structure, so the wing does not get ripped of during reentry. Dead weight.

    I'm sorry, how does a winged vehicle magically avoid the space junk problem? Who said the capsule would not be re-usable? Just because it has wings does not mean it won't contribute to space junk and just because it's a capsule does not mean it won't be reusable. Wings add considerable mass in regards to mission profile. They are dead weight.

    A "small version" of the shuttle on top of a booster stack would hardly be reusable. The orbiter might be, but that stack isn't. The closest thing to reusable boosters right now is the SpaceX Falcon-9. The first stage of which they would like to make reusable, the second stage they wish to make reusable and the dragon capsule which is designed to be reusable. Alas, none of which has yet to fly so they don't know how many of those goals they will make. Still, it's better than NASA is doing in-house currently.

    Also, there are regulations these days to keep space junk to a minimum by de-orbiting spent boosters and retired satellites. Most of the junk in orbit is legacy stuff and the odd "lost tool".
     
    Last edited: Jan 31, 2010
  8. Jetfire

    Jetfire Guest

  9. RobertVA

    RobertVA Fleet Captain Fleet Captain

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    Rockets with high efficiency (through high exaust velocity) but low thrust might be good for shortening the transit time for interplanetary spacecraft but aren't going to be of much use rendezvousing with a space station. Most of the speed an interplanetary spacecraft accumulates approaching Earth would be building up in as it travels the last few tens of thousand miles. The velocity would build up much faster than a low thrust engine could counter it.

    As distance increases the effects of gravity fall off pretty rapidly. While Earth's gravity has relatively little effect at half a million miles it accelerates approaching objects at a much higher rate when they swing within a range where a space station would be. This applies as much to a spacecraft (or asteroid for that matter) that would be in a trajectory passing the Earth as it would for an object plummeting at a steep angle into the atmosphere.

    Traveling through a series of very elongated orbits might be compatible with the low trust generated by many of the high efficiency/high exhaust velocity engine concepts. On the first approach past Earth the spacecraft would enter an elongated orbit that would take weeks to complete. Each time the spacecraft goes through the lower part of its orbit it would operate its engine for several days to lower the orbit's high point. It might take several weeks or a month to circularize its orbit enough to rendezvous with a space station though. That procedure would probably still require significant amounts of propellant and consume a significant part of the time saved running the high efficiency engine through much of the interplanetary transit.
     
    Last edited: Jan 31, 2010
  10. Alpha_Geek

    Alpha_Geek Commodore Commodore

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    Governments push back the frontier. Private enterprise follows.

    While private enterprise moving to LEO is indeed part of that pattern, governments should continue the outward push, like say... to the moon, Mars, and beyond. The cancellation of Constellation will do nothing but keep us stagnant, lose jobs, lose chances at new amazing technology, and be one less circus to amuse the plebs.
     
  11. Lindley

    Lindley Moderator with a Soul Premium Member

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    That's why Obama is increasing NASA's funding to develop a new heavy-lift capability. It's one step towards pushing out further.

    Everything I've read about this decision suggests that it is strongly aligned with the recommendations of the Augustine Commission.
     
    Last edited: Feb 1, 2010
  12. Squiggy

    Squiggy FrozenToad Admiral

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    NASA will be getting other people into the LEO game so they can focus on other things. Unless you want to double the budget of the agency (and given how your name has the word "geek" in it, I'm probably preaching to the choir), NASA can't do both.

    The idea of going to the moon is great. But it costs money. NASA never got what it was promised and now has to make up for the past 5 years of being underfunded. We can't spend a billion dollars every few months to taxi a astronaut to the ISS and develop a next gen spacecraft and do everything else Congress wants NASA do to. This is just the natural course of evolution. Hell, by this point private enterprises were supposed to be involved in space anyway.
     
  13. Neopeius

    Neopeius Admiral Admiral

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    And let me just say.. one more time.. I predicted all of this back in 2004 :) If there are live archives, I can prove it.

    Good riddance, Constellation.
     
  14. Alpha_Geek

    Alpha_Geek Commodore Commodore

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    Yeah, but Constellation was the keystone to beyond LEO. (Need Atlas V Heavy to go man rated though!) They could build fewer, go farther, and let private enterprise service ISS and do other LEO things. Bigelow Aerospace is already on that like stink on a monkey, not to mention the other efforts.

    And yes, you are preaching to the choir. As a kid, there were two times that I stood on the grass in view of the firing room shutters and felt 100% liquid fueled thunder. :)
     
  15. sojourner

    sojourner Admiral Admiral

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    Constellation was a broken keystone. The HLV they will be developing now is much more likely to succeed.
     
  16. Alpha_Geek

    Alpha_Geek Commodore Commodore

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    Yeah, but the HLV is not the spacecraft. It's back to the drawing board (once funded, if ever), for the vehicles that will take humanity to the moon and beyond, because none of the private LEO jobs will.

    Hey Rutan, hurry up with Tier 6, willya? LOL
     
  17. diankra

    diankra Commodore Commodore

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    I'm with Sojourner here. Constellation was never going to work without a bigger budget. If it was politically possible to get it the bigger budget, then why not go for a budget that's a bit bigger than that, and produce something that's more than an updated Apollo (not an entirely bad idea) stuck on top of the worst aspects of the Shuttle system?
    But the bigger budget wasn't there. Better to cancel it than commit NASA to another few decades of another system that's been sabotaged on day one by underfunding.
    How the alternatives will work work... I can only hope well.
     
  18. Alpha_Geek

    Alpha_Geek Commodore Commodore

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    The only upside I see to this is that somewhere, Jake Garn is crying over Thiokol not making any more SRB segments.
     
  19. Squiggy

    Squiggy FrozenToad Admiral

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  20. John Picard

    John Picard Vice Admiral Admiral