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Elon and the SpaceX team are kicking ass! 2 months ago they hovered at 250m: http://www.youtube.com/watch?v=xUvbh-Z8Abk http://www.youtube.com/watch?v=xUvbh-Z8

Elon and the SpaceX team are kicking ass! 2 months ago they hovered at 250m: http://www.youtube.com/watch?v=xUvbh-Z8Abk http://www.youtube.com/watch?v=xUvbh-Z8Abk 6 months ago they hovered at the height of a 12-story (40m) building: http://www.youtube.com/watch?v=Zz-NYeH-CEY http://www.youtube.com/watch?v=Zz-NYeH-CEY These guys are on a very fast learning curve. These near-ground tests are the hardest. Elon said that they will be using a fully reusable first stage in 2015, only 18 months away: http://allthingsd.com/20130530/tesla-ceo-and-spacex-founder-elon-musk-the-full-d11-interview-video/ http://allthingsd.com/20130530/tesla-ceo-and-spacex-founder-... [http://en.wikipedia.org/wiki/SpaceX_reusable_rocket_launching_system#Falcon_9_booster_post-mission.2C_controlled-descent_tests http://en.wikipedia.org/wiki/SpaceX_reusable_rocket_launchin...]

bpicolo 13y ago
Not sure I would call them the hardest. Stabilizing while traveling thousands of miles per hour in atmosphere to get to the point you can land like this seems much harder.
- mikeash 13y ago
  Isn't that more or less a solved problem, at least? Maybe there are aspects of it that I'm unfamiliar with which make it much harder for a rocket than for a capsule, but it seems similar, and SpaceX already has that down for Dragon.
- grinich 13y ago
  ICBMs already do this, and we've been precisely deorbiting satellites for decades. Landing safely is the really tricky part. During the Corona spy satellite days, they used to catch the parachuting pods with a plane+hook. http://upload.wikimedia.org/wikipedia/commons/7/76/Keyhole_capsule_recovery.jpg http://upload.wikimedia.org/wikipedia/commons/7/76/Keyhole_c...
  - InclinedPlane 13y ago
    ICBM warheads have about a 90% chance of landing within a circle with a radius of about half a kilometer, at least according to declassified info, the actual accuracy is likely higher. Even so, that hardly compares to a precision landing on a small landing pad.
    - mikeash 13y ago
      I think your info on ICBM accuracy may be a bit out of date. Some searching around shows modern American missiles with a CEP of 100 meters or better. I'm not quite sure how to translate a CEP (50% chance of landing in the circle) to a 90% figure, but I wouldn't think it would be a factor of 5. (I specified American because the Soviets and Russians have historically lagged behind here, and it looks like that's still the case. I don't know what the story is for other ICBM-equipped powers. The Soviets compensated for their lesser accuracy by fielding larger bombs.) Also keep in mind that the major factor limiting ICBM accuracy these days is the need to be completely self contained, since they're intended to operate in the middle of World War III, and no external navigation sources can be counted on. Slap a JDAM guidance system on the warhead and your ICBM can deliver it to within whatever square meter you're most interested in. ICBMs armed with conventional bombs have been considered, since accuracy can be enough for that to work now. As far as I know, the only reasons these haven't been deployed are cost (using up an entire ICBM to deliver a chemical bomb seems wasteful) and, probably more importantly, the fact that there's no way to tell whether a given ICBM is carrying a nuclear warhead or not, thus the strong possibility that using such a weapon could trigger a nuclear war by accident. See: http://en.wikipedia.org/wiki/Prompt_Global_Strike http://en.wikipedia.org/wiki/Prompt_Global_Strike
      - InclinedPlane 13y ago
        The Minuteman III (the backbone of the US ICBM fleet) has a listed CEP of 200 m. The Trident D5 has a CEP of as low as 90 m, but it's an SLBM not strictly an ICBM, and it varies depending on range. The CEP figure represents the radius of a circle where there is a 50% chance of the bomb landing within that circle. The CEP figure is basically 2/3 of a standard deviation.

bpicolo 13y ago

Not sure I would call them the hardest. Stabilizing while traveling thousands of miles per hour in atmosphere to get to the point you can land like this seems much harder.

mikeash 13y ago
Isn't that more or less a solved problem, at least? Maybe there are aspects of it that I'm unfamiliar with which make it much harder for a rocket than for a capsule, but it seems similar, and SpaceX already has that down for Dragon.
grinich 13y ago
ICBMs already do this, and we've been precisely deorbiting satellites for decades. Landing safely is the really tricky part. During the Corona spy satellite days, they used to catch the parachuting pods with a plane+hook. http://upload.wikimedia.org/wikipedia/commons/7/76/Keyhole_capsule_recovery.jpg http://upload.wikimedia.org/wikipedia/commons/7/76/Keyhole_c...
- InclinedPlane 13y ago
  ICBM warheads have about a 90% chance of landing within a circle with a radius of about half a kilometer, at least according to declassified info, the actual accuracy is likely higher. Even so, that hardly compares to a precision landing on a small landing pad.
  - mikeash 13y ago
    I think your info on ICBM accuracy may be a bit out of date. Some searching around shows modern American missiles with a CEP of 100 meters or better. I'm not quite sure how to translate a CEP (50% chance of landing in the circle) to a 90% figure, but I wouldn't think it would be a factor of 5. (I specified American because the Soviets and Russians have historically lagged behind here, and it looks like that's still the case. I don't know what the story is for other ICBM-equipped powers. The Soviets compensated for their lesser accuracy by fielding larger bombs.) Also keep in mind that the major factor limiting ICBM accuracy these days is the need to be completely self contained, since they're intended to operate in the middle of World War III, and no external navigation sources can be counted on. Slap a JDAM guidance system on the warhead and your ICBM can deliver it to within whatever square meter you're most interested in. ICBMs armed with conventional bombs have been considered, since accuracy can be enough for that to work now. As far as I know, the only reasons these haven't been deployed are cost (using up an entire ICBM to deliver a chemical bomb seems wasteful) and, probably more importantly, the fact that there's no way to tell whether a given ICBM is carrying a nuclear warhead or not, thus the strong possibility that using such a weapon could trigger a nuclear war by accident. See: http://en.wikipedia.org/wiki/Prompt_Global_Strike http://en.wikipedia.org/wiki/Prompt_Global_Strike
    - InclinedPlane 13y ago
      The Minuteman III (the backbone of the US ICBM fleet) has a listed CEP of 200 m. The Trident D5 has a CEP of as low as 90 m, but it's an SLBM not strictly an ICBM, and it varies depending on range. The CEP figure represents the radius of a circle where there is a 50% chance of the bomb landing within that circle. The CEP figure is basically 2/3 of a standard deviation.