SpaceX launch webcast: Orbcomm-2 Mission [video] • Hacker News Board

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#441

Post by lmm » Wed, Dec 23, 2015, 9:37 PM UTC

rdancer wrote: post #439

lmm wrote: post #341

Earlier quoted context omitted.

Can the first stage land with a failed center engine?

It has eight other engines to fall back on, and engine restarts are already normal part of the return flight. Centre engine failure before the final burn starts would certainly be survivable. It's just a question of the software using two or three engines in a symmetrical pattern for a 1/2 or 1/3 of the length of the 1-engine burn. I'm not sure if they could also fire one engine asymmetrically and use momentum and th…

Landing is already severely constrained by the minimum thrust of the engine though. At a minimum using two would make the tolerances much, much tighter. Remember it wouldn't be double the thrust but rather several times the net thrust, since the downward thrust from gravity would stay the same.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#442

Post by gozur88 » Thu, Dec 24, 2015, 12:36 AM UTC

mikeash wrote: post #182

gozur88 wrote: post #151

Earlier quoted context omitted.

Depends on the procedure they ultimately decided to use for the prep. Originally the the shuttle main engines had to be taken apart, with every part inspected before the next launch. If they have to do something like that there's not much point. But if they can get it to point where it's a matter of gassing it up for the next flight, that's a huge savings. Fuel is a few hundred grand for a rocket that costs sixty mil…

Hopefully it won't be anything like the Shuttle. The Shuttle was bleeding edge in a dozen different ways. The engines were extremely high performance and that made them fragile. SpaceX seems to build things a lot more low-key. They don't use fancy propellants, their engines aren't particularly efficient, and overall they seem to go more for robustness and simplicity. (Simplicity doesn't really apply for a crazy-ass l…

Yes, I expect you're right about that, and furthermore I expect SpaceX will be willing to make substantial design changes in support of that effort.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#443

Post by andygates » Tue, Dec 29, 2015, 10:14 AM UTC

foxylad wrote: post #143

Anyone know how accurate the first-stage landing was? Obviously delta v is most important, but hitting the bullseye would just top off the accomplishment.

GPS-limit type accurate on the X on the centre of the pad. 5-10m off.

Re: SpaceX launch webcast: Orbcomm-2 Mission [video]

#444

Post by andygates » Tue, Dec 29, 2015, 10:17 AM UTC

hackuser wrote: post #205

What changed that made this cost-effective? 1) The companies pursuing this, SpaceX, Blue Orgin, etc., can't be the first to think of it. If the first stage accounts for 75% of the cost of a launch, as one article I read says, I'm sure many have considered, going back to the first launches decades ago, how to reuse it. 2) The technology to land rockets vertically has existed for a long time, going back to the lunar la…

A lot of people have tried to retrieve boosters. The Shuttle approach is suboptimal (solid boosters can't be throttled/relit/extinguished easily, the sea is evil, turnaround times are huge). ESA and the Russians and NASA have all thought about glide-back boosters and got mired in complexity. The new-space approach of "just the rocket, plus better control systems" is paying off, but it does take modern kit and thinking.