4 ms·
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
by 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 agoI 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 agoThanks 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!"