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SpaceX Falcon rocket explodes on landing after delivering satellite to space

bbc.com

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Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#61

Post by dkbrk »

Grue3 wrote: post #30
bantunes wrote: post #25

Could someone explain to me why they attempt this? Wouldn't inflating a set of floating devices when it goes down the ocean an easier way of retrieving it? Or something other than this REALLY HARD TO PULL OFF maneuver? Genuinely interested.

Yeah, I don't understand why they won't keep landing them on the ground like everyone else does. It's not like there's not enough space on Earth.

> like everyone else does

Nobody else does this. I have absolutely no idea what you could possibly be referring to. SpaceX lands on land preferably when it is an option.

> I don't understand why they won't keep landing them on the ground ... It's not like there's not enough space on Earth

As a general rule, you not understanding the reason for something does not mean there is not a good reason. For reference, see the Dunning-Kruger effect. Furthermore, I honestly do not understand how you could even contemplate "SpaceX does not think there is enough space on land" as a serious argument and treat its dismissal as legitimate support for your beliefs. This is some of the most egregiously lazy reasoning I have ever seen on the internet.

SpaceX launches rockets in the direction of water so that an accident won't threaten property or people on land. To return to land after staging the first stage of the Falcon 9 must perform a burn—the "boost back"—to point its lateral velocity back to land; this is the first of three burns required for landing and the most expensive in fuel by a considerable margin. If the first stage is travelling too quickly (greater than approximately 1.6 km/s lateral velocity) it does not physically have enough fuel to return to the launch site and perform the landing. In this case, a far more mild burn can put the booster on a re-entry trajectory and it can land on an autonomous barge in the ocean. As the rocket trajectory is chosen to put the ground path well away from land, the choice is between either returning to the launch site or landing in the ocean. If a return to the launch site is prohibited by the rocket's capabilites and physics then an ocean landing is the only option.

In the case of Jason-3 a barge landing was the only option as SpaceX does not yet have permission to use their landing facility at Vandenberg Air Force Base. In the future, the central core of the Falcon Heavy will almost certainly have to land in the ocean due to its velocity at separation.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#62

Post by ceejayoz »

ck2 wrote: post #45

Would it be possible to have locking mechanisms directly in the dock itself? ie. maybe the rocket descends several feet INTO the dock into a hole which then locks around the body of the rocket? || || ==||== dock (which opens wide for decent and then closes) || ^^

I'd imagine that'd be even more complex and prone to failure.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#63

Post by lmm »

ck2 wrote: post #45

Would it be possible to have locking mechanisms directly in the dock itself? ie. maybe the rocket descends several feet INTO the dock into a hole which then locks around the body of the rocket? || || ==||== dock (which opens wide for decent and then closes) || ^^

To be clear it's a barge, not a dock.

It might be possible, but we're talking about a rocket descending from hypersonic spaceflight; the accuracy is always going to be +/- a few metres. And the rocket would still have to have some kind of "hardpoints" that were strong enough to absorb the landing impact (you don't want to land smack on the delicate engine nozzles). A (relatively) big flat landing field and legs on the rocket itself seem like the smart approach (and Musk wants whatever technology they use to be usable for landing on Mars too).

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#64

Post by ck2 »

lmm wrote: post #63
ck2 wrote: post #45

Would it be possible to have locking mechanisms directly in the dock itself? ie. maybe the rocket descends several feet INTO the dock into a hole which then locks around the body of the rocket? || || ==||== dock (which opens wide for decent and then closes) || ^^

To be clear it's a barge, not a dock. It might be possible, but we're talking about a rocket descending from hypersonic spaceflight; the accuracy is always going to be +/- a few metres. And the rocket would still have to have some kind of "hardpoints" that were strong enough to absorb the landing impact (you don't want to land smack on the delicate engine nozzles). A (relatively) big flat landing field and legs on th…

Yeah but if a rocket can so easily explode just by falling over, I'm not sure there are any legs I trust it to land on.

I mean what if the legs were damaged during launch somehow, how exactly would it get back down safely other than just dropping it in the ocean completely?

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#65

Post by dchesterton »

el_zorro wrote: post #39
dchesterton wrote: post #28

Earlier quoted context omitted.

They want to use this tech to eventually land rockets on other planets so the rocket needs to be able to land upright. Short term it might be easier to land on inflatables but they're looking at the bigger picture.

The utility here is not really landing on other planets, but instead the order of magnitude decrease in launch costs if they don't have to build a new first stage for every launch.

This could theoretically be achieved by either means. The question was specifically why a vertical landing is favoured over a cushioned inflatable landing.

Musk has stated in the past that they're looking to eventually use this tech to create rockets which can be used on Mars, hence why parachutes and inflatables are out of the question.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#66

Post by pjc50 »

ck2 wrote: post #45

Would it be possible to have locking mechanisms directly in the dock itself? ie. maybe the rocket descends several feet INTO the dock into a hole which then locks around the body of the rocket? || || ==||== dock (which opens wide for decent and then closes) || ^^

Part of the problem is that the rocket walls are very thin and only suitable for vertical loads. You'd practically have to surround it with giant airbags to make that work.

They'll fix the landing leg problem somehow.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#67

Post by martindevans »

ruffmuff wrote: post #46
bantunes wrote: post #25

Could someone explain to me why they attempt this? Wouldn't inflating a set of floating devices when it goes down the ocean an easier way of retrieving it? Or something other than this REALLY HARD TO PULL OFF maneuver? Genuinely interested.

Two main reasons I can think of: 1) Sea water is extremely corrosive. If your booster takes a dunk in the drink, it's going to be very hard to refurbish for another launch. Lots of components (electronics, valves, etc) would need to be replaced and the structural integrity of the tanks themselves may be compromised by rust. 2) Flotation devices attached to the booster = extra payload. It would be the canvas/dinghys A…

In addition to that the vehicle is extremely weak when lying on its side. I should think there's a good chance the tanks could be damaged by waves bending the vehicle.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#68

Post by lmm »

Medox wrote: post #29

The landing could be made safer by something like cushioned walls that deploy towards the rocket after touchdown, to avoid such explosions. Think of a giant Christmas Tree stand like this: http://www.christmastreeland.co.uk/product_images/v/428/761_... . but with cushioned hooks on the barge. You can't always hope for all 4 legs to be in perfect condition, or that there aren't high waves in the ocean. That rocket is…

Bear in mind how large the rocket is, and that anything you put on the barge has to withstand being scorched by rocket exhaust.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#69

Post by ethbro »

ceejayoz wrote: post #52
Medox wrote: post #29

The landing could be made safer by something like cushioned walls that deploy towards the rocket after touchdown, to avoid such explosions. Think of a giant Christmas Tree stand like this: http://www.christmastreeland.co.uk/product_images/v/428/761_... . but with cushioned hooks on the barge. You can't always hope for all 4 legs to be in perfect condition, or that there aren't high waves in the ocean. That rocket is…

Here's a side-by-side comparison of their three barge landing attempts: https://www.youtube.com/watch?v=IA7RzJckvQ4 I don't think big, over-engineered solutions really look necessary with the amount of progress they're making. Plus, there aren't any cushioned walls on Mars, which is SpaceX's eventual goal - use this sort of tech to touch down there.

Also, if you deployed mitigation methods prematurely, then it stops the drive for improvement and tuning of the core landing functionality.

Quick deploy cushions or other "Oops" enhancements might feature into the final version of the barge, but for now I think they're still trying to maximize the landing success rate. Better not to split engineering resources when the most important problem can still benefit from optimization.

Re: SpaceX Falcon rocket explodes on landing after delivering satellite to space

#70

Post by rtkwe »

smoyer wrote: post #44
marvin wrote: post #8

SpaceX actually got very close to sticking this landing. Sea conditions were reasonably rough, with 3-meter waves. It's also the first time SpaceX launches in fog, IIRC. Everything about the landing except the stuck leg seemed to be perfect. So IMHO, the fact that the rocket exploded is not the most pertinent fact about this experiment. The main piece of news is that SpaceX is exceedingly likely to be able to recover…

As a former gymnast, I like the sticking the landing analogy but a human (even on an unstable mat) has far more control over their balance point (we do much of our balancing by bending at the waist - if only the rocket had one). In any case, I agree that this was very close. I've also spent a reasonable amount of time on "big water" and was specifically watching the attitude of the landing deck with respect to the ho…

The Falcon 9 isn't totally reusable not does it plan to be. It still has a non-recoverable second stage so it's not quite to the point of a SSTO.
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