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Is this one of their Grasshopper rockets? Apparently the name Grasshopper was just the name of the rocket during the tests, because I can't find that term used

by dm2 13y ago

Is this one of their Grasshopper rockets? Apparently the name Grasshopper was just the name of the rocket during the tests, because I can't find that term used anywhere. http://www.nasaspaceflight.com/2014/02/spacex-crs-3-landing-legs-plan-first-stage-recovery-ambitions/ http://www.nasaspaceflight.com/2014/02/spacex-crs-3-landing-...

fit2rule 13y ago
I think you're referring to this rocket: http://www.space.com/23193-spacex-grasshopper-rocket-highest-hop-video.html http://www.space.com/23193-spacex-grasshopper-rocket-highest...
- deleted 13y ago
  [deleted]
InclinedPlane 13y ago
No, this is a fully operational regular launch which will deliver cargo to the ISS. But it will have sufficient extra payload capacity to allow for this test (which will test some but not all of a reusable flight profile of the first stage including a controlled deceleration and hover burn but only over the ocean).
- dm2 13y ago
  So this rocket is fully capable for vertical landing, they're just doing it over the ocean for safety reasons? That's awesome. Such a short time from initial testing to actual use. I wonder if they have a buoy or something for it to target.
  - mscarborough 13y ago
    Not fully capable, they say 30-40% chance of success, but that it in any case, it will provide good data for future work.
    - JshWright 13y ago
      Well, it has a 30-40% chance of being fully capable, in that case ;)
  - InclinedPlane 13y ago
    Precisely so. SpaceX has been enormously aggressive in developing reusability. The Falcon 9 v1.1, which has flown to orbit 3 times already, is fundamentally capable of reusability, it just requires addition of landing legs and then flying a reusable flight profile. In software terms it's as though they have deployed reusability but kept it behind a "feature flag" which keeps it turned off for most uses, for now. Once they gain more confidence in actually flying reusable flight profiles using stages that include landing legs then they will eventually work their way to returning to land at the launch site.
    - dm2 13y ago
      The landing legs are attached, just folded up. https://pbs.twimg.com/media/BlL4V42IYAAgZ1J.jpg:large https://pbs.twimg.com/media/BlL4V42IYAAgZ1J.jpg:large
      - InclinedPlane 13y ago
        Sorry for being ambiguous, this flight has legs, most don't. The only major requirement for reusability is the legs. Every "expendible" flight makes use of reusable equipment that gets thrown away.
  - smackfu 13y ago
    They did 8 test flights in 2012 and 2013, and they were pretty successful, so I'm not sure what else there was to test at this point.
    - lutorm 13y ago
      The Grasshopper test flights didn't really expand the envelope to anything nearly like the conditions the first stage experiences at entry (max altitude and speed <1% of the real thing) so I'm sure there's no shortage of things to test.
  - arrrg 13y ago
    Considering where they launch I don’t think landing anywhere but in the ocean is an option. They launch from the coast to the east (taking advantage of the Earth’s rotation), meaning when the first stage shuts off it will be somewhere over the Atlantic, on a ballistic trajectory further eastward. Since the goal is to be re-useable without losing too much payload capability I really don’t think they can have much fuel to spare at that point. To decelerate and come to a hover, sure, that’s the goal, but to actually decelerate, accelerate in the opposite direction, decelerate again and come to a hover? That would be ridiculous. SpaceX will need to launch from somewhere else to end up over land when the first stage shuts off.
    - Crito 13y ago
      I believe that the idea ultimately is indeed to thrust back to to land after taking off from the east coast. Earth's rotation helps them again, as the rotation is such that the land will be be rotating toward the rocket, reducing the distance that it must cover. This self-post on /r/spacex describes how it could/would work. Basically the guy modded KSP to hell for realism (realistic fuels, more realistic aerodynamics, realistic earth and launch site inclination, etc) and managed to fly the first stage up and then back to the launch site: http://www.reddit.com/r/spacex/comments/1z6vyt/boostback_demonstration_video/ http://www.reddit.com/r/spacex/comments/1z6vyt/boostback_dem... @mikeash (posting is throttled for me at the moment): The rotating earth isn't providing any sort of mechanical advantage for the returning first stage (unlike during liftoff). However it does move the launch site closer to the rocket. Very rough numbers: earth rotates at about 1000mph at the equator, so if we fudge florida down to the equator and assume stage separation is at t+3:00, then in the elapsed time between launch and stage separation, the launch center has moved 50 miles to the east. In the subsequent minutes up until first stage touchdown, it will move even further to the east. Consider that just launching from the equator straight up to 35,786km would not put you into into a geostationary orbit; you would fall back down to the west of your launch site. If you went straight up, while initially moving at the same horizontal velocity as the ground from which you launched, you would not maintain the same surface-relative velocity; you need to speed up going east to do that. The outside of a record moves faster than the inside of a record.

by dm2 13y ago

fit2rule 13y ago

I think you're referring to this rocket: http://www.space.com/23193-spacex-grasshopper-rocket-highest-hop-video.html http://www.space.com/23193-spacex-grasshopper-rocket-highest...

deleted 13y ago
[deleted]

InclinedPlane 13y ago

No, this is a fully operational regular launch which will deliver cargo to the ISS. But it will have sufficient extra payload capacity to allow for this test (which will test some but not all of a reusable flight profile of the first stage including a controlled deceleration and hover burn but only over the ocean).

dm2 13y ago
So this rocket is fully capable for vertical landing, they're just doing it over the ocean for safety reasons? That's awesome. Such a short time from initial testing to actual use. I wonder if they have a buoy or something for it to target.
- mscarborough 13y ago
  Not fully capable, they say 30-40% chance of success, but that it in any case, it will provide good data for future work.
  - JshWright 13y ago
    Well, it has a 30-40% chance of being fully capable, in that case ;)
- InclinedPlane 13y ago
  Precisely so. SpaceX has been enormously aggressive in developing reusability. The Falcon 9 v1.1, which has flown to orbit 3 times already, is fundamentally capable of reusability, it just requires addition of landing legs and then flying a reusable flight profile. In software terms it's as though they have deployed reusability but kept it behind a "feature flag" which keeps it turned off for most uses, for now. Once they gain more confidence in actually flying reusable flight profiles using stages that include landing legs then they will eventually work their way to returning to land at the launch site.
  - dm2 13y ago
    The landing legs are attached, just folded up. https://pbs.twimg.com/media/BlL4V42IYAAgZ1J.jpg:large https://pbs.twimg.com/media/BlL4V42IYAAgZ1J.jpg:large
    - InclinedPlane 13y ago
      Sorry for being ambiguous, this flight has legs, most don't. The only major requirement for reusability is the legs. Every "expendible" flight makes use of reusable equipment that gets thrown away.
- smackfu 13y ago
  They did 8 test flights in 2012 and 2013, and they were pretty successful, so I'm not sure what else there was to test at this point.
  - lutorm 13y ago
    The Grasshopper test flights didn't really expand the envelope to anything nearly like the conditions the first stage experiences at entry (max altitude and speed <1% of the real thing) so I'm sure there's no shortage of things to test.
- arrrg 13y ago
  Considering where they launch I don’t think landing anywhere but in the ocean is an option. They launch from the coast to the east (taking advantage of the Earth’s rotation), meaning when the first stage shuts off it will be somewhere over the Atlantic, on a ballistic trajectory further eastward. Since the goal is to be re-useable without losing too much payload capability I really don’t think they can have much fuel to spare at that point. To decelerate and come to a hover, sure, that’s the goal, but to actually decelerate, accelerate in the opposite direction, decelerate again and come to a hover? That would be ridiculous. SpaceX will need to launch from somewhere else to end up over land when the first stage shuts off.
  - Crito 13y ago
    I believe that the idea ultimately is indeed to thrust back to to land after taking off from the east coast. Earth's rotation helps them again, as the rotation is such that the land will be be rotating toward the rocket, reducing the distance that it must cover. This self-post on /r/spacex describes how it could/would work. Basically the guy modded KSP to hell for realism (realistic fuels, more realistic aerodynamics, realistic earth and launch site inclination, etc) and managed to fly the first stage up and then back to the launch site: http://www.reddit.com/r/spacex/comments/1z6vyt/boostback_demonstration_video/ http://www.reddit.com/r/spacex/comments/1z6vyt/boostback_dem... @mikeash (posting is throttled for me at the moment): The rotating earth isn't providing any sort of mechanical advantage for the returning first stage (unlike during liftoff). However it does move the launch site closer to the rocket. Very rough numbers: earth rotates at about 1000mph at the equator, so if we fudge florida down to the equator and assume stage separation is at t+3:00, then in the elapsed time between launch and stage separation, the launch center has moved 50 miles to the east. In the subsequent minutes up until first stage touchdown, it will move even further to the east. Consider that just launching from the equator straight up to 35,786km would not put you into into a geostationary orbit; you would fall back down to the west of your launch site. If you went straight up, while initially moving at the same horizontal velocity as the ground from which you launched, you would not maintain the same surface-relative velocity; you need to speed up going east to do that. The outside of a record moves faster than the inside of a record.