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I wouldn't take that phrase too literally. I take it to mean that she wants them to actually land a rocket (not necessarily on all feet with no bounce). The oth

I wouldn't take that phrase too literally. I take it to mean that she wants them to actually land a rocket (not necessarily on all feet with no bounce). The other attempts were "landings", but they blew up. Bounce or no, if they land the rocket upright, I think that's sticking it.

ethbro 11y ago
The problem as I understand it, and I think what smoyer was talking about, is that there are no other viable landing methods for the rocket than "feet" first. Sufficient thrust is only available from the main engines, and those only point in one direction. So if it starts to tilt off vertical then the rocket has no way to right itself after a point (and certainly no way to counteract gravity). Gravity + tall enough rocket + landing on side = boom (or crumple). So "stick it or bust"?
- ohitsdom 11y ago
  There are cold gas thrusters on top of the first stage that fire to keep its balance. If it lands in an uneven manner and starts to tip, those should be enough to maintain the landing. You can see them working in the video embedded in the link below. They only didn't work in that instance because the main rocket motor fired too long at it was too much for the small thrusters. http://www.spacex.com/news/2015/06/24/why-and-how-landing-rockets http://www.spacex.com/news/2015/06/24/why-and-how-landing-ro...
  - grinich 11y ago
    I think the bigger issue is that idle thrust of a single Merlin engine (which is used to land the first stage) produces more force than gravity on the vehicle. This means it can't "hover" so the final burn must be timed with exact precision to have ~zero velocity on impact. Doesn't give a lot of room for error.
  - ethbro 11y ago
    Thanks for the link! I was aware there were thrusters on top of the stage (otherwise the difficulty would seem impossible), but that description and the longer video were a lot better than what I'd seen previously. I couldn't dig up any specs on the cold-gas thrusters' actual output. I mean, how much tilt can they recover from on landing? Best I could find was this Musk response. "Q. In addition, can you talk more about the grid fins that will be flying tomorrow? How do they compare to maneuvering with cold-gas thrusters? The grid fins are super important for landing with precision. The aerodynamic forces are way too strong for the nitrogen thrusters. In particular, achieving pitch trim is hopeless. Our atmosphere is like molasses at Mach 4!"

ethbro 11y ago

The problem as I understand it, and I think what smoyer was talking about, is that there are no other viable landing methods for the rocket than "feet" first. Sufficient thrust is only available from the main engines, and those only point in one direction. So if it starts to tilt off vertical then the rocket has no way to right itself after a point (and certainly no way to counteract gravity). Gravity + tall enough rocket + landing on side = boom (or crumple). So "stick it or bust"?

ohitsdom 11y ago
There are cold gas thrusters on top of the first stage that fire to keep its balance. If it lands in an uneven manner and starts to tip, those should be enough to maintain the landing. You can see them working in the video embedded in the link below. They only didn't work in that instance because the main rocket motor fired too long at it was too much for the small thrusters. http://www.spacex.com/news/2015/06/24/why-and-how-landing-rockets http://www.spacex.com/news/2015/06/24/why-and-how-landing-ro...
- grinich 11y ago
  I think the bigger issue is that idle thrust of a single Merlin engine (which is used to land the first stage) produces more force than gravity on the vehicle. This means it can't "hover" so the final burn must be timed with exact precision to have ~zero velocity on impact. Doesn't give a lot of room for error.
- ethbro 11y ago
  Thanks for the link! I was aware there were thrusters on top of the stage (otherwise the difficulty would seem impossible), but that description and the longer video were a lot better than what I'd seen previously. I couldn't dig up any specs on the cold-gas thrusters' actual output. I mean, how much tilt can they recover from on landing? Best I could find was this Musk response. "Q. In addition, can you talk more about the grid fins that will be flying tomorrow? How do they compare to maneuvering with cold-gas thrusters? The grid fins are super important for landing with precision. The aerodynamic forces are way too strong for the nitrogen thrusters. In particular, achieving pitch trim is hopeless. Our atmosphere is like molasses at Mach 4!"