SpaceX Breaks Down Its Rocket Landing Attempts

An anonymous reader writes: Twice now, SpaceX has attempted to land one of its rockets on a barge in the ocean after it delivered a payload to orbit. Each attempt came very close, and provided some fascinating imagery. In a new post on their website, SpaceX explains where they're at with rocket landing technology, and what went wrong with the earlier trials: "That controlled descent was successful, but about 10 seconds before landing, a valve controlling the rocket's engine power (thrust) temporarily stopped responding to commands as quickly as it should have. As a result, it throttled down a few seconds later than commanded, and—with the rocket weighing about 67,000 lbs and traveling nearly 200 mph at this point—a few seconds can be a very long time. With the throttle essentially stuck on 'high' and the engine firing longer than it was supposed to, the vehicle temporarily lost control and was unable to recover in time for landing, eventually tipping over." They believe they've solved the issues that cropped up in the earlier tests, and they're looking forward to the next attempt, which will happen on Sunday if the weather cooperates.

Comments

Re:Since they are on the ocean...

[cjameshuff]

Rockets are fragile, they can't take much mistreatment. A net would at most catch some debris...they don't want debris, they want a rocket. And in normal operation, they should be able to soft land upright on the platform, so a net would be an unnecessary complication in the best case...in the worst case, the net system gets in the way and causes a landing failure.

Fine, I'll explain again

[cbhacking]

I'm going to assume you've been doing the /. equivalent of living under a rock, since this question comes up (and gets answered) every single time this topic is discussed, and that's a lot. But what the hell...

Landing on solid ground is, generally, preferable. However, unlike the ocean where you can tell all the boats to get out of a safety zone, land has these inconvenient things like buildings and infrastructure that can't simply be told to stay away for their own safety. Until it was clear how precisely SpaceX could bring the rocket down - and remember, we're talking about something returning from the edge of space, at supersonic speeds, with barely any fuel remaining, in a maneuver that had never been attempted before - it would have been foolish to bring the rocket down anywhere near any inhabited regions. Given the geography around the launch sites they use, that means the ocean is the best bet by far.

Also, sometimes they may not have a choice. The rocket *really* doesn't have a lot of fuel left as it returns, and it's going really, really fast in a direction that is decidedly away from the launch site (but not fast enough to make it all the way around the world, or the second stage wouldn't be needed to actually achieve orbital velocity). SpaceX pulls a lot of cool tricks to guide the rocket's return, like using the stage as a lifting surface (with a truly abysmal lift/drag ratio, I assume, but they're also trying to scrub speed) while controlling it with little folding grid fins (which are quite effective at those speeds). However, at the end of the day, even Falcon 9 may not have the fuel margin to return to the spaceport after launches even though it has enough fuel to launch *somewhere*. The center core of the Falcon Heavy - which flies for much longer than the F9 first stage - will be much too far downrange to boost back to the spaceport in most cases. Thus, for FH's center core, the barge may be the only landing option. Landing on a ship may be harder than landing at a conventional spaceport, but the ship can be almost anywhere there's ocean, while land-based spaceports are not noted for their mobility.

Now, with all that said, the goal is to, eventually, be able to land at the spaceport. The next F9 launch after this one will, according to a cool site called SpaceX Stats, attempt to return to the launch site and land there. This presumably demonstrates that SpaceX has been found to have sufficient precision in the first-stage landing attempts so far for it to be safe to land near people and expensive buildings. I wish them the very best of luck!