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SpaceX Starship rocket explodes minutes after launch from Texas

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Re: SpaceX Starship rocket explodes minutes after launch from Texas

#861
post #61

People want to see 100% success in all things. But that isn't very economical. Compare the SLS to Starship. SLS has had a 100% success rate. One launch, one success. But it costs $2B per launch (and climbing) and has taken 12 years to get here. Plus, it's stealing pieces of the Space Shuttle, which was developed in the 70s over a long period of time. Starship will launch a half a dozen "failures" before they achieve…

>> People want to see 100% success in all things. But that isn't very economical. That sounds logical, but isn't really a thing in aerospace/space. Complicated high-energy systems have thousands of failure points. So to have any chance of success each failure point needs to be engineered below, by way of example, a 0.0001% chance of failure. That costs lots of money. But say one decides to accept more risk for less c…

What you've missed here is that failure points can only be guessed or simulated prior to testing. That analysis is often more expensive than the cost of a test and test article.

So SLS does a LOT of analysis and manages to find and rectify failure points prior to flight. They pay a lot in analysis and inflexible design to do this.

SpaceX does some analysis, but then flies to confirm the analysis early. That way they identify actual failure points and can use sensors to see how close they got to failure.

For instance today I'm sure they learnt a lot from each failed engine, parts on the booster that stopped working, detailed telemetry on ship behavior on flight and sensors for the non-separation of booster from ship.

SpaceX builds to the same high tolerances as other rocket manufacturers, but they don't try to avoid testing through overly rigorous analysis. They also don't gold-plate their manufacturing, instead making tradeoffs to allow cheaper volume production with recovery instead.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#862

Earlier quoted context omitted.

>> People want to see 100% success in all things. But that isn't very economical. That sounds logical, but isn't really a thing in aerospace/space. Complicated high-energy systems have thousands of failure points. So to have any chance of success each failure point needs to be engineered below, by way of example, a 0.0001% chance of failure. That costs lots of money. But say one decides to accept more risk for less c…

That doesn't really apply here. The dynamics of stage separation on Starship are orders of magnitude more complex than anything used on any previous rocket. If you want to look at what failure looks like for a super large rocket compare it to the failed Soviet N1. This flight demonstrated better performance in a single test flight than every N1 test flight over years. The N1 suffered catastrophic failure after catast…

I feel like the N1 is unfairly demonized. They didn't have the benefit of modern closed loop computer flight controls that we have now. Detailed fluid dynamics simulations. Modern manufacturing techniques and production accuracy.

N1 might have simply been before its time.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#863

One of the new graphics that showed up on the dashboard was that of the engines lit. There were at least 2 on the outer ring that were fed from TO, and a few more winked out during the flight. I’m curious how many off engines the system tolerates. How many do they anticipate regularly? I’ve never noticed if Falcon 9s periodically run as a Falcon 8 or 7? All and all, ‘‘twas an awesome sight. Kudos to all those cheerin…

How many engines can be of depends heavily on when the go off. Even 10s of flight can make a huge difference.

Generally Merlin engines on the Falcon 9 are incredibly reliable. In over 200 flights there were only a couple of engine failures. Some worked nominally on accent but had some failure during landing.

> How many do they anticipate regularly?

The vast majority flights should never have an engine out. This is something that should generally never happen. I think SpaceX would hope that far less then 1% of flights have an engine out issue. Anything else I don't think they would consider acceptable.

SpaceX will redesign the Raptor engine as often as they have to to get the reliability to Merlin levels.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#864

Earlier quoted context omitted.

>That massive hole in the ground should not have happed, and I suspect that was not an expected possibility. Interestingly, this post predicting exactly this kind of damage was flagged on HN just days ago: https://news.ycombinator.com/item?id=35590279 I think it's unlikely that SpaceX wasn't aware of the damage that would be caused. They have a pretty good engineering team, and that aspect didn't involve an anomaly,…

I wonder whether all that debris was a factor in the engine failures?

Hopefully the data will work that out. Raptor 1 seemed to have quality control issues in that some percentage of engines would fail, hopefully this isn't also the case for Raptor 2 or at least can be worked out.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#865
post #534
post #119

Earlier quoted context omitted.

My guess was for this flight it was "once off the pad, we will fly as long as it doesn't leave the envelope" since it's all about data collection.

Isn't that a safety risk with such a huge rocket?

The envelop is designed with safety in mind. If it leaves the envelop it has a certified self destruct system on board that will trigger and destroy the rocket.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#866

Earlier quoted context omitted.

Exactly, the two untested things were stage zero (all the new ground infrastructure) and stage one (booster). I think it's clear one of their biggest lessons is that the construction of the launch mount is wrong, and it REALY needs a flame diverter. Take a look at this photo: https://mobile.twitter.com/LabPadre/status/16490627841670307... That massive hole in the ground should not have happed, and I suspect that was…

>That massive hole in the ground should not have happed, and I suspect that was not an expected possibility. Interestingly, this post predicting exactly this kind of damage was flagged on HN just days ago: https://news.ycombinator.com/item?id=35590279 I think it's unlikely that SpaceX wasn't aware of the damage that would be caused. They have a pretty good engineering team, and that aspect didn't involve an anomaly,…

Surely considering what the Saturn V launchpad used - a rather huge hole in the ground lined with concrete and an insane amount of water being released to dampen sound and damage ???.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#867

I'm really interested to see the hole it dug under the launch mount. The NASA SpaceFlight van took a direct hit from a fast moving chunk of concrete. https://twitter.com/JerryPikePhoto/status/164905272269878477... https://twitter.com/LabPadre/status/1649053476276797440 Edit: it really did dig a crater (this was flat concrete under the pad before): https://twitter.com/LabPadre/status/1649062784167030785

NSF on their stream did talk that this is the only launch that will be done without water system - my understanding is that it would be used during launch to reduce damage to the pad.

Yes, they have a water deluge system, but that might not be enough, and they also need a flame diverter.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#868

I'm really interested to see the hole it dug under the launch mount. The NASA SpaceFlight van took a direct hit from a fast moving chunk of concrete. https://twitter.com/JerryPikePhoto/status/164905272269878477... https://twitter.com/LabPadre/status/1649053476276797440 Edit: it really did dig a crater (this was flat concrete under the pad before): https://twitter.com/LabPadre/status/1649062784167030785

The liftoff video at https://twitter.com/SpaceX/status/1649097087248891904 shows some clear debris hitting the ocean.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#869

Did the range officer destroy the rocket because it wasn't going to separate, or did the tumble destroy the rocket?

I think SpaceX rockets don't have a traditional range safety officer anymore. That function was replaced by software. I suspect the software has certain conditions that will cause destruction.

But it might also have been manual intervention.

Re: SpaceX Starship rocket explodes minutes after launch from Texas

#870

Earlier quoted context omitted.

I agree with this assessment and probably the biggest problem in the test. After that, they still have a fair way to go on Raptor reliability; I was a bit disappointed with the number of engine outs: clearly the engines have not arrived. I think the big win of the day was the overall resilience of the vehicle. It seemed to handle (what looked to be) possibly explosive engine failures and kept going and stayed intact.…

> I was a bit disappointed with the number of engine outs Who knows if they were controlled tests, you need failures to understand the reliability domain. Engineering is about handling failure, not success. You learn very little from success, esp with so many free variables.

Reminds me of the flash memory cells SSD's are made of - overprovision them because some are going to become/or is bum anyways.
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