SpaceX is a go for April 30th: 1st commercial launch to space station

Discussion in 'Science and Technology' started by RAMA, Apr 17, 2012.

  1. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Dragon is cleared to dock. Orbital manoeuvres towards the station begin in seven hours. I hope I'm awake whenever they get to the docking.
     
  2. publiusr

    publiusr Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Safe and sound
    http://www.nasaspaceflight.com/2013/03/resilient-crs-2-dragon-pursuit-iss-sunday-berthing/

    In some ways, it has the kinds of problems you want to have, in that it shows how rugged your craft is--same with the engine that came apart in the last launch.

    Knowing you have redundant thrusters, engine-out, etc.--and that you can brute force your way into salvaging a mission is far better than having to have a lesser vehicle with no margin have to perform perfectly every time.

    There are good problems and bad problems.
     
  3. sojourner

    sojourner Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    The problem did highlight a single point of failure on Dragon. Using one helium tank to pressurize the oxy tanks for 4 sets of thrusters was not great thinking. My guess is they will go to a second He tank and have it pressurize 2 diametrically opposed thruster pods. There by if one tank fails they still have 2 opposing thruster pods to ensure control.
     
  4. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Hm? Wikipedia says Dragon uses nitrogen tetroxide, not oxygen? What am I missing?
     
  5. gturner

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    That when people talk about the "oxidizer tank" they're not necessarily referring to liquid oxygen.

    This is obviously a serious failure because it set their schedule back a whole day whereas having a main engine explode saw them arrive 30 minutes early.
     
  6. publiusr

    publiusr Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    It's always the little things, isn't it?

    Big first stage engine loss? No problem--we've engine out. Stuck thruster with not much more thrust than a can of Aqua-Net hairspray--you're done (almost).

    That was one of the reasons that I am so impressed with footage like this:
    http://www.viddler.com/v/b8fda424

    That thing is rock-steady in hover, something a KKV isn't even supposed to do--support it's own weight on a column of thrust. That's what billions can buy

    Now compare that with Carmak's contraptions.That is what millions buy.

    Small craft can be very hard to control, what with the computer often faster than the plumbing, as it were. Rather like getting your shower perfectly between scalding hot and freezing cold.

    Energia had time to gimbal even with dead-weight Polyus on its side. The smaller something is, the easier it is to get out from under you.
     
  7. sojourner

    sojourner Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Wait, you're saying a KKV doesn't need a high t/w ratio? Dude, you might want to think on that a little. That KKV is doing exactly what it's supposed to do.

    If Armadillo was actually trying to replicate the KKV's capabilities, I have no doubt they could. There's no billion dollar technology in that video. Just some hypergolic thrusters and a microcontroller.
     
  8. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Thing is, Armadillo's trying to construct a relatively large spacecraft that can make a controlled descent and landing on the surface of the moon. You can strap some model rocket engines to a gyroscope and make it hover for a few seconds, but that's a far cry from a functional landing craft (or, for that matter, a functional Dragon space capsule).

    There's also the fact that the multiple kill vehicle has effectively been scrapped because they couldn't get the smaller projectiles to synch up properly. Hell, they can barely get the one-shot version to work correctly; according to some reports, it doesn't work at all. But that's beside the point, because it's not designed to actually shoot down incoming ICBMs, it's designed to deter America's nuclear-armed enemies (whoever the hell that's supposed to be) from launching missiles at us.
     
  9. publiusr

    publiusr Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    No, it is launched by a missile to hit a warhead--not hover in place over a net really. It is supposed to have enough precision in its thrusters to hit a very small target. That it could hover is a plus.

    Now there was a rumor that the R-36M SATAN (Dnepr) derived from the SS-( (Cyclone) was an armored ICBM with an agile bus, so the kinetic kill vehicle itself would have to manuver more--rather like two people trying to side step each other in a hall(right to right, left to left) and colliding anyway, like Stockholm and Andrea Doria ;)

    The KKV is just a payload. It is coasting up when released and thrusting a bit out the sides to line up with the target. If the missile that launched it was itself agile, then the KKV doesn't need enough thrust to support its own weight really, if things are lined up well from the start.

    I'm thinking the guys who did this net test expected the actual KKV to use less thrust during an intercept than it did doing this hover. This was a way to show how precise their product was. I really doubt Armadillo could replicate it myself. BMDO has such a head-start and all. I seem to remember a similar test back in the 1980's

    Now the anti-missile defense arguements puzzle me a bit. They say striking a warhead with a KKV is all but impossible, and yet there are very complex Mars sample return missions that rely on a bus to scoop up a sample return package smaller than most any warhead--and in space near another planet even. So if I hear someone poo-poo missile defense then talk Mars sample return--its pretty much the same problem.

    Now if you can mass produce KKVs as easily as warheads, then you have effective missile defense against a smaller country at least.

    But that's an arguement for another time. My point was sometimes it's the little things that can cause the most trouble.
     
    Last edited: Mar 17, 2013
  10. sojourner

    sojourner Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    There are just so many things wrong with this.
     
  11. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    And in order to do that it has to be able to accelerate under very tightly controlled parameters, holding a relative position in the path of an oncoming target that is also moving very very quickly. From the seeker's point of view, it is stationary and everything else around it is moving; it is programmed to keep its target stationary in its field of view no matter where that target actually moves.\

    They did not. The specific point of the test was to see whether or not the MKV had enough precision to follow a pre-programmed test fire routine simulating an actual intercept (with a theoretically high divert trajectory). They performed a similar test with the KKV (which your video does not depict) in which they added a small thruster fed by a pressure hose because the smaller unit's thrusters weren't powerful enough to hover for any amount of time.

    The ideal test of the system, of course, would be for it to hold a stationkeeping attitude in freefall -- on a vomit comet or something -- but there's no way anyone's gonna let them actually test that thing on an airplane.

    Nobody says that. What they say is that the interceptors that currently exist can't quite pull this off under battlefield conditions because both their timing and their tracking requirements are infeasible under those conditions.

    It's a bit like saying it's impossible to do a kick flip on a skateboard during a hurricane. That statement tells you less about kick flips than it does about hurricanes.

    Put that another way: how would you assess the feasibility of a Mars Sample Return mission if the Martian government started shooting at your return vehicles?:vulcan:
     
  12. gturner

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    But compared to the normal battlefields where we use missile interceptors, the ICBM and LRBM battlefield is pristine, with vastly simpler trajectories (no hard aerodynamic maneuvering), no smoke, no clouds, no birds, and no nearby aircraft with 10,000 pounds of jamming equipment. It might as well be laboratory conditions. :)

    Which is why people who've mastered aerial missile combat in hurricanes shouldn't have any problem pulling it off in perfect weather with not only no wind, but no air.

    Exactly! Anti-missile missiles would make such a mission highly unlikely to succeed.
     
  13. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    Except that in laboratory conditions you know exactly where the missile launched from, exactly what it's trajectory is, and there's no actual risk involved if you intercept it too late or too low, plus there's usually only one target and you know for sure that's the one you're shooting at.

    Under battlefield conditions, you have uncertainties in the detection of the launch, the accurate determination of its trajectory and potential questions about whether or not the radar signature you're tracking is a signal object or multiple ones or whether there are others coming up behind it from other launch sites. Either way, you have between 15 and 30 minutes from the time of launch to the time of impact and you have to figure all of this out within a narrow launch window if you're going to really pull off the intercept.

    It's actually easier to intercept mortar shells and short range rockets, since the firing solutions and tracking data can be worked out by a single set of sensors and the only trick is positioning those sensors in the right place to direct the interceptor (IOW, not all that different from normal AA warfare).

    That's just it, though: hurricane conditions represent "battlefield" conditions, not merely short range. Put it simply, it's much easier to TEST a weapon system than it is to USE one in uncontrolled conditions. It isn't half as simple as you'd think, especially when the interceptor's infrastructure system is given virtually no warning at all before the actual attack.
     
  14. gturner

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    But for an ICBM intercept you don't need the launch location, just the range and vector range rate. You don't need to know the history of the trajectory, even though you'd know more about that than any conventional tactical launch where unknown aircraft are lobbing missiles on multiple incoming vectors, often from below the radar horizon. The problem is much simpler than warship defense where they have to expect a saturation attack from a variety of platforms and incoming angles simultaneously, possibly coming in with heavy jamming support, and where the warning and flight times are shorter. And with an ICBM intercept, you don't have to worry that some of the incoming missiles are friendlies returning to refuel.

    That's the actual battlefield environment we're used to. The battlefield environment for space is vastly cleaner, the sensor data is better, the background problems are gone, the targets have almost no ability to maneuver without creating an instantaneous and large IR signature, they follow a purely ballistic path in between maneuvers, and they're very, very fragile compared to conventional targets (a slightly damaged warhead isn't going to survive re-entry, but a flaming Kamikaze can still hit).

    It's a much easier targeting environment than the early Sidewinders had to cope with, and they could complete an intercept using just half-a-dozen vaccuum tubes for a control system, yet were able to distinguish targets from bright background clouds, adjust their control sensitivity for differing air-speeds and air-densities, and make off-angle lead intercepts.

    The difficulty with ABM intercepts is the massive delta-V required to get the terminal package into the target environment.
     
  15. Crazy Eddie

    Crazy Eddie Vice Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    You do if you're pre-positioning tracking radars with the intention of quickly obtaining an accurate firing solution for the interceptor. If the radars are in the wrong position or if the attack comes from an unexpected direction (say, someone launching a missile on a polar orbit that comes up from south to north) your sensors could give a false reading on its course and speed, or fail to detect it altogether.

    The last rounds of ABM tests were fired against targets whose exact launch points were known ahead of time so the tracking systems could be placed in an optimal position to acquire the target and guide the missile to a hit. You don't have the luxury of doing this in battlefield conditions, because you 1) Can't know ahead of time when someone's going to launch an ICBM at you and what launch site they're using and therefore cannot position your sensors to watch all likely approaches and 2) don't necessarily know what kind of missile is going to be launched at you or its flight profile. ABMs appear to be optimized for certain types of ground-based ICBMs like the kind China and/or Russia still use in their land-based silos, and they aren't particularly good at intercepting those anyway; they're virtually useless against SLBMs, which are often launched at closer range using much flatter trajectories.

    And much more complicated due to the fact that the thing you're defending is a thousand kilometers wide and the thing that could attack it could be just about anywhere. And that too ignores the fact that anyone who is going to fire an ICBM at the United States probably isn't going to fire just one, and probably isn't going to use one that'll be easy to intercept (even the older Russian missiles have decoy launchers and electronic warfare systems).

    No, the difficulty with ABM intercepts is the problem of scale. You're not shooting a missile at another missile in the same battlespace, you're shooting a spacecraft at another spacecraft half a world away on a path that will bring them into contact with one another at exactly the right moment in their respective flight profiles. Even when you have the timing down perfect -- which you can't in a battlefield situation -- the degree of uncertainty in both the target and interceptor's flight path is huge and grows exponentially larger the less accurate your targeting fix is.

    When you factor in the fact that the United States only has about 24 ABMs of capable of intercepting an ICBM for the more than 200 missiles possessed by both China and the Russian Federation, ultimately those missiles are more for peace of mind than an actual defense against ICBMs.
     
  16. YellowSubmarine

    YellowSubmarine Rear Admiral Rear Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    [yt]Ns0IHCj2q-E[/yt]

    Fun recent interview with Musk. I like how he has began to refer to the Mars round-trip reusability with more certainty now, and more confidence that he can bring the price down dramatically. In previous interviews, he was cautious even when talking about LEO reusability. I can't wait for that Falcon Heavy-Grasshoper hybrid he could be having in mind.
     
  17. RAMA

    RAMA Admiral Admiral

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    I noticed this too. Also since the last post the mission was a success...so congrats to all involved.

    Still pretty anxious about the SLS, a multi-tiered space race is really heating up. The video from the SLS tests remind me of the footage from Apollo's early days.

    RAMA
     
  18. gturner

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    They're talking about doing a first-stage flyback/return next year. :)
     
  19. sojourner

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    Re: SpaceX is a go for April 30th: 1st commercial launch to space stat

    They're going to try and soft land the first stage in the ocean on the next few flights as build up to land landings.