5 ms·
Seems like it adds a lot of risk I'm actually wondering about that. If I understand correctly, the arms can move up and down, and pivot around the tower. Thi
by rkagerer 2y ago
Seems like it adds a lot of risk
I'm actually wondering about that. If I understand correctly, the arms can move up and down, and pivot around the tower. This allows them to correct for some error in the rocket trajectory and also (presumably) "soften" the final contact. Between the nozzles and the arms, it gives SpaceX a lot of degrees of freedom in the final seconds (you can see how the booster kind of "hovered" right at the end) and in certain respects might even offer more forgiveness than the hard ground.
Could it smash into the tower? For sure. Would that be more dangerous than smashing into the pad? I don't know.
It's a new technique with which we don't have a lot of experience.
- ChuckMcM 2y agoMy thought (admittedly not well developed) is that smashing into a landing pad of concrete can damage that pad but it can be quickly repaired without affecting the ability to launch future rockets. If you damage the launch tower significantly you're going to have to suspend launches from it until you fix it. So the "higher risk" is more critical assets offline in the event of a non-optimal return.
- rkagerer 2y agoUnderstood, although weren't they out of commission for a really long time anyway the last time they damaged their launchpad?
- ocdtrekkie 2y agoApparently they are heavily investing in having multiple towers ready to go to be able to do multiple successive launches. Presumably with that approach, one being damaged for a while will be annoying but not project-stopping.
- creer 2y agoThere are already 2 launch towers (2nd one not quite complete but getting there.)
- creer 2y agoHeh Plus one at Kennedy in Florida, LC-39A
- generuso 2y agoIt helps enormously that unlike Falcon-9 this rocket can dial down the thrust of its engines low enough to be able to actually hover or to move arbitrarily slowly in the final meters before touchdown. It can arrive to the designated intermediate point with some already good accuracy, and then take some time to trim the remaining errors to the noise level more slowly, possibly with feedback from the ground sensors. The chopsticks also include rails with shock absorbers, the action of which can be seen in the view from the tower during the landing [1], so the required accuracy is probably relatively modest, provided one plans the maneuver carefully. [1] https://youtu.be/Ysx4t7ICO58?t=678 https://youtu.be/Ysx4t7ICO58?t=678
- TechDebtDevin 2y agoThe main takeaway from Scott's commentary is that the chopsticks allow the ommission of landing legs and all their subsequent systems and saves a ton of weight. The added risk to dial this technique in is likely worth it in the long run from a sustainability stand point.
- kibwen 2y agoExcept that the landing legs allow you to land anywhere with a flat pad of concrete, whereas this requires comparatively enormous infrastructure investment.
- sagarm 2y agoYou'd still have to recover the rocket. I imagine the number of places you could land and economically recover the rocket is pretty small.
- swagasaurus-rex 2y agounless it can be refueled from a truck and reused without inspection.
- 2y ago
- restalis 2y agoTo me, it's not risk reduction that they're after with that booster catching mechanism, but weight reduction. Those landing legs that we've seen before (and the mechanism related to them) are costly weight that is absolutely necessary only on the rocket itself, because that is expected to land on its own somewhere on a bare rock. For booster however, it makes sense to have as much of such launch and landing weights externalized, considering booster's reduced use-case of starting from a spaceport and very soon ending up back there too.
- thot_experiment 2y agoThe way the trajectory is designed is that it has to scoot over to the tower at the last second, and it only does that if it's really really sure it can make it, otherwise it crashes off to the side.
- db48x 2y agoA good explanation of how it works, from before the catch: https://www.youtube.com/watch?v=ub6HdADut50 https://www.youtube.com/watch?v=ub6HdADut50
- JoachimS 2y agoYes, we should probably assume that the SpaceX engineers have considered all of the risks HN readers are able to come up with in a few hours. And that they have evaluated alternatives like the added weight etc of having foldable legs on the booster. The catchzilla solution is an example of their amazing ability to think out of the box. This solution, and things like the rapid evolution of the Raptor engine (see picture, story here: https://medium.com/@futurespaceworld/the-evolution-of-spacex-raptor-engines-228a4df8837a https://medium.com/@futurespaceworld/the-evolution-of-spacex...), dynamic engine configuration (33, 13, 3, zero, up again) and control is almost magically impressive. This is the stuff of Sci-Fi, brought to life.