SpaceX Plans to Land Next Falcon 9 on Solid Ground • Hacker News Board

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#71

Post by TeMPOraL » Thu, Apr 16, 2015, 6:08 PM UTC

jsolson wrote: post #68

TeMPOraL wrote: post #26

> "Just purely the boat moving, even in a low sea state, it's hard to imagine that vehicle is going to stay vertical," Shotwell said. "That vehicle is big and tall, compared to the itty-bity-greater-than-a-football-field-size ship." Is this a new development? This contradicts both a lot of things I read over the Internet (granted, those were not official SpaceX statements) and the apparently still ongoing plans to bu…

If it's actually that serious a problem (and I'm not a rocket scientist, so I don't know), it suggests a solution: stabilize the landing bed on the ship relative to the sea. Perhaps have the bed float above the ship electromagnetically such that you can control the field strength applied to any part of the platform dynamically as the ship bucks underneath it. There might be a reason that people don't let me design la…

> There might be a reason that people don't let me design large mechanical systems...

Naah, I can totally see this working in Kerbal Space Program...

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#72

Post by jccooper » Thu, Apr 16, 2015, 6:14 PM UTC

hahamrfunnyguy wrote: post #60

Instead of moving the rocket to meet the platform, would it be feasible to employ some stabilization mechanism so that the barge stays relatively level and the rocket doesn't have to correct as much?

It does that. The barge has four thrusters for stabilization. The problem is not the barge moving, but rather control problems. They would have happened on land too--unless by landing on a larger area you have a simpler control problem, which may be true.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#73

Post by jccooper » Thu, Apr 16, 2015, 6:16 PM UTC

kllrnohj wrote: post #20

sergiosgc wrote: post #12

Earlier quoted context omitted.

I never read anything that pointed towards that objective. Note that the first stage gets a lot of horizontal velocity, so bringing it back to the launch pad is expensive (fuel-wise). It is better to just cancel out the horizontal vector, follow a parabolic trajectory and land east of the launch pad.

https://www.youtube.com/watch?v=4Ca6x4QbpoM http://www.space.com/13140-spacex-private-reusable-rocket-el... "After separating in orbit, the two stages of the rocket would come back to Earth and land at the launch pad." They've always intended both the boosters and the second stage to return to the launch site.

Recent statements indicate that they've given up on second stage recovery for the F9. Just too hard given current margins. That'll be in some future architecture.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#74

Post by tjradcliffe » Thu, Apr 16, 2015, 6:16 PM UTC

TeMPOraL wrote: post #26

> "Just purely the boat moving, even in a low sea state, it's hard to imagine that vehicle is going to stay vertical," Shotwell said. "That vehicle is big and tall, compared to the itty-bity-greater-than-a-football-field-size ship." Is this a new development? This contradicts both a lot of things I read over the Internet (granted, those were not official SpaceX statements) and the apparently still ongoing plans to bu…

As has been pointed out almost endlessly over the past day, almost all the mass in the rocket is in the lower end by the time it hits the pad, so despite what anyone can imagine it isn't that hard to keep it vertical.

The hard part is landing it softly enough and vertically enough that it won't break or fall over due to residual velocity. Once it's down, in low seas, the few degrees wobble of the barge won't have an effect.

Or in other words: I can't imagine SpaceX engineers haven't worked all this out in detail, and I can't imagine SpaceX would be trying this if they didn't have good reason to think it would work, and I can't imagine that SpaceX engineers aren't professionally competent, so, based on the standard "what I can't imagine can't be true", Shotwell is spouting irrelevancies.

This is the problem with imaginary arguments: if anyone thinks that what they can or can't imagine is relevant to what is true, they have to yield the argument to me, who can't imagine there is anyone in this day and age who still beleives that.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#75

Post by godgod » Thu, Apr 16, 2015, 6:18 PM UTC

This to me seems like a logical idea. Water attempts are what we will have to have but why not test it on a stable platform first to gain knowledge before shooting for the real end goal. Musk is brilliant.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#76

Post by jccooper » Thu, Apr 16, 2015, 6:20 PM UTC

jayfuerstenberg wrote: post #32

Land the rocket on some flame-proof air bags. It doesn't have to land vertically does it? Let it fall over gently if need be.

The dang thing is a couple mm thick and ten stories tall. There's no "gentle" option available for tipping over. The solution is to land it right. It'll happen.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#77

Post by jccooper » Thu, Apr 16, 2015, 6:22 PM UTC

0xffff2 wrote: post #17

sergiosgc wrote: post #13

Does this mean they'll be launching from another facility? Right now, the trajectory goes over to the sea, and bringing the first stage back to dry land is expensive. They'd have to launch far away from the east coast.

Two factors: 1. Yes, they will eventually be launching elsewhere. SpaceX is currently building its own launch facility in Brownsville, TX, which would indeed permit landing at the cape. 2. Elon Musk seems to think that despite the expense, they can fly the rocket back to the launch pad for lighter payloads.

Florida's an awful long way from Brownsville. Take a look at the launch danger zones chart; first stage recovery is just off the coast. Maybe you could finagle a second stage recovery in Florida from Texas, but only from very specific inclinations. Doesn't seem likely to be useful.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#78

Post by grecy » Thu, Apr 16, 2015, 6:25 PM UTC

daeken wrote: post #38

harshreality wrote: post #24

Earlier quoted context omitted.

They need to be able to stabilize the rocket's landing in all sorts of conditions if they want to have any hope of landing it on another planet. It's not like interplanetary launches will be able to schedule launches to choose optimal weather conditions for the landing. Maybe, if they're lucky, they'll be able to orbit briefly to avoid bad weather at the landing site, but moderate winds and wind gusts are going to be…

> They need to be able to stabilize the rocket's landing in all sorts of conditions if they want to have any hope of landing it on another planet. Well, not really. Dragons (and Red Dragons, for interplanetary travel) are way, way less sensitive to the whims of weather. The issue with the first stage is that you have a very large, very fragile, very bottom-heavy tin can that you're trying to balance on a moving platf…

If Dragon lands on some other planet, how does it get back without a stage 1 also landing on said planet?

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#79

Post by TeMPOraL » Thu, Apr 16, 2015, 6:26 PM UTC

tjradcliffe wrote: post #74

TeMPOraL wrote: post #26

> "Just purely the boat moving, even in a low sea state, it's hard to imagine that vehicle is going to stay vertical," Shotwell said. "That vehicle is big and tall, compared to the itty-bity-greater-than-a-football-field-size ship." Is this a new development? This contradicts both a lot of things I read over the Internet (granted, those were not official SpaceX statements) and the apparently still ongoing plans to bu…

As has been pointed out almost endlessly over the past day, almost all the mass in the rocket is in the lower end by the time it hits the pad, so despite what anyone can imagine it isn't that hard to keep it vertical. The hard part is landing it softly enough and vertically enough that it won't break or fall over due to residual velocity. Once it's down, in low seas, the few degrees wobble of the barge won't have an…

Well, the point is, Shotwell is the COO of SpaceX, which makes this whole thing weird.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#80

Post by jccooper » Thu, Apr 16, 2015, 6:27 PM UTC

netcan wrote: post #58

netcan wrote: post #57

Earlier quoted context omitted.

I'm not sure... Is Miami important to our overall goal of becoming a multiplanetary civilization? I don't see what Miami adds to the mission and I am quite sick of everyone being so precious about it. I have an ex girlfriend from Miami and honestly, I think we would all be better off if we stopped making excuses for her, defending her, covering for her and just let Elon give her what's coming to her!

wow. I guess I overstepped a line. *I don't really have an ex from Miami. Never been there. No ill wishes for the city. ..just to be clear.

HN does not take well to joke comments. It's not specifically mentioned in the guidelines, but falls generally under "off-topic". Feeling is "this isn't Reddit."