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SpaceX SN9 Explodes on Landing

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Re: SpaceX SN9 Explodes on Landing

#181

Post by boxed »

new_realist wrote: post #165

Feynman on SpaceX’s “Big Bang” design approach. I don’t think he would have been a fan: The usual way that such engines are designed (for military or civilian aircraft) may be called the component system, or bottom-up design. First it is necessary to thoroughly understand the properties and limitations of the materials to be used (for turbine blades, for example), and tests are begun in experimental rigs to determine…

This is totally wrong. Feynman is correct obviously by you are totally wrong.

The big bang (your words) or the top down (Feynmans words) method is what the SLS is doing. Not spacex.

Re: SpaceX SN9 Explodes on Landing

#182

Post by [deleted] »

smattiso wrote: post #167

Is this a viable landing strategy in the long run? Both SN8 and SN9 landings have ended in total fatalities. What happens if the landing happens to occur during a 50 mph wind gust, etc. If this maneuver isn't designed to be 100% fault tolerant maybe they need to be thinking about an emergency eject? I like the simplicity of the Starship design. How much extra weight would a nosecone eject + parachute add?

[deleted]

Re: SpaceX SN9 Explodes on Landing

#183

Post by bacon_waffle »

naikrovek wrote: post #162
minikites wrote: post #159

Earlier quoted context omitted.

Why is SpaceX making the same mistakes 70 years later?

I don't recall NASA ever doing a rocket landing so I'm not sure which mistakes you are seeing repeated.

I was surprised to learn recently that NASA did do some rocket landings in the 90s: https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

Re: SpaceX SN9 Explodes on Landing

#184

Post by bryananderson »

cmoscoe wrote: post #52
rglover wrote: post #28

Love seeing these tests for two reasons: 1.) Experiencing history in the making, especially knowing that the SpaceX team will eventually get it right. 2.) Realizing that even the best of the best have repeated failures and need to rely on iteration to get "there."

On the 'repeated failures' piece, that's somewhat new for aerospace. Traditionally, things would be over-engineered, and losing a test vessel would be considered a bad thing. SpaceX seems very content to blow up a bunch of rockets on their way towards not blowing up rockets. This seems to have caused at least part of their recent issues with the FAA, who seem to be less ok with explosions. It will be very interesting…

It’s really a throwback to the old days of aerospace. From the 1930s to the early 1960s, the standard method was to iterate rapidly with relatively cheap hardware, to learn and fix problems as quickly as possible. The von Braun and Korolev teams operated this way, among others. They all blew up a ton of rockets. What changed was the necessity of completing Saturn V and landing on the Moon by the end of the 1960s. Apollo program head George Mueller recognized that, with the planned number of iterative tests, they were going to be too late. He made the gutsy decision to launch “all-up”: spend a ton of money up front to overengineer the crap out of the vehicle and cut out most of the iteration. It worked!

But alas, the aerospace world overlearned the lesson and has been cargo-culting it ever since. Mueller’s decision was purely a matter of expediency to meet Kennedy’s goal and beat the Russians. It wasn’t a statement that this was the best way to do engineering, absent those constraints. To make matters worse, all-up only works under the funding conditions of Apollo: a massive spike in funding to cover the up-front cost. Without that spike, the costly development phase has to be stretched out, and the whole thing ends up taking longer than iteration. In other words, you can save time this way when money is absolutely no object, but otherwise you lose time. See Boeing’s SLS: basically 15 years of development and they just static-fired it for the first time. Launch is maybe a year away.

We’ve all gotten used to the all-up style of development, and SpaceX’s rediscovery of rapid iteration makes it seem like a new and untested way of doing things. But I think the dominant narrative—that all-up is prudent and conservative while iterative is risky—is completely backward. All-up carries a massive amount of risk that fundamental design issues won’t become apparent until the tremendously costly development phase is done. Iteration allows assumptions to be tested and modified as quickly as possible. Most of SpaceX’s early ideas about reusability turned out to be wrong. If they had committed all the money and time to those early concepts before flight-testing, they would have never accomplished it. The early rocketry pioneers operated this way, and it’s why they accomplished the things they did. Maybe SpaceX will finally free the space industry from perpetually repeating what worked for Apollo, which after all operated under unique political conditions.

Re: SpaceX SN9 Explodes on Landing

#185

Post by GizmoSwan »

gridspy wrote: post #174
GizmoSwan wrote: post #161

Earlier quoted context omitted.

Don't get your hopes up. Since it is rotating on an axis while moving and twice, it has a huge degree of freedom for failure. Even if successfully returns 100 times, any untested change to its payload can change the parameters which are apparently unknown because they have not used any fancy simulation. Good luck. I will be watching and ready to say I told you so. The staff could be absolute geniuses by they will not…

The failures so far relate to the pressurization of the header tanks and the engine performance on re-light (hard problems). I imagine these will be well solved after 100 flights. The assumption that shifting payload is going to boggle the flight computers leading to loss of craft sounds unlikely. Both because the payload will be secured and the flight computers are more dynamic than that. Finally, the forces on the…

747 can not flip like that; it would stall and crash. The narrow bodied 737s crashed for less. Their fancy flight computer miscalculated because of center of gravity miscalculations. They crashed after 100s of flights.

I like your optimism. Good luck. I mean it. I would not fly in that thing even if they paid me a million.

Sorry for my lack of faith.

Re: SpaceX SN9 Explodes on Landing

#186

Post by hyperion2010 »

unanswered wrote: post #120
hyperion2010 wrote: post #56

For both SN8 and SN9 my brain is screaming at me "surely they need more than 3 engines?!" Is the ultimate expectation that the engines will never fail, because it sure seems like they can't deal with losing even a single engine. I'm sure this is completely incorrect given that the issue for SN8 was tank pressure.

> because it sure seems like they can't deal with losing even a single engine Define "deal with". This rocket did 100% of what any rocket was ever supposed to do, before SpaceX came along and redefined what a rocket is supposed to do: go up.

"Deal with" == "Not blow up" == "No RUD" in the event of a single engine failure.

Manned space flight kind of has this kind of important additional requirement that things like ICBMs don't, which is that they can't just "go up" the have to come back down and not end in a ball of fire.

Re: SpaceX SN9 Explodes on Landing

#187

Post by nickik »

I think one thing that people fail to appreciate about what SpaceX is doing is their core believe with this project is that the manufacturing system is 10-100x more difficult then the design of the rocket itself, and that their goals can only be achieved if these two things are co-designed.

Their goals are to design a rocket system capable of landing on Earth, Moon, Mars and possibly others. Is must be able to refuel in space. It must be able to rapidly reusable, as in the same day multiple times. It must be cheap to manufacture, and it must be cheap to operate.

Every prototype brings in lots of new changes, none is exactly like that before, every around 5 prototypes there is a major generation upgrade. Every new prototype does not just test the new design, but also the improved manufacturing process.

All the learnings from both the build and the launch flow directly back to the developers and engineers working on it, and the required changes to into the backlog and eventually make it into later prototypes.

What the outcome of this process is, who knows unknown. SpaceX has shown to be incredibly flexible and change to new things quickly and without making a big deal about it. The change from carbon to stainless steel for example is a case where SpaceX had already tested tanks, they had already ordered tools, they had already bought a location. Within one month they dropped that. Iteration speed to slow, material cost to high, performance gain when combined with heat shield not worth it anyway.

Only when you consider cost, heat-shield consideration and iteration speed is it clear that stainless steel beats carbon fiber by a large margin.

The heat shield has been changed multiple times. The fins have been redesigned multiple times. The legs are a hot issue right now. The header tank design has changed over time. And so on and so on.

SpaceX will move forward like that, produce more and more prototypes that are closer and closer to the almost impossible goal. Every prototype is a fully integrated test from materials, design, manufacturing and operations.

Re: SpaceX SN9 Explodes on Landing

#188

Post by bernulli »

bryananderson wrote: post #184
cmoscoe wrote: post #52

Earlier quoted context omitted.

On the 'repeated failures' piece, that's somewhat new for aerospace. Traditionally, things would be over-engineered, and losing a test vessel would be considered a bad thing. SpaceX seems very content to blow up a bunch of rockets on their way towards not blowing up rockets. This seems to have caused at least part of their recent issues with the FAA, who seem to be less ok with explosions. It will be very interesting…

It’s really a throwback to the old days of aerospace. From the 1930s to the early 1960s, the standard method was to iterate rapidly with relatively cheap hardware, to learn and fix problems as quickly as possible. The von Braun and Korolev teams operated this way, among others. They all blew up a ton of rockets. What changed was the necessity of completing Saturn V and landing on the Moon by the end of the 1960s. Apo…

I’m not sure 3200 full scale tests of Saturn V’s F-1 engine, 2000 in an iterative trial-and-error scramble to suppress combustion instabilities is what I would call “overengineered to cut out iteration” during Apollo http://www.yang.gatech.edu/publications/Journal/JPP%20(1993,...

Re: SpaceX SN9 Explodes on Landing

#189

Post by yellowapple »

imglorp wrote: post #177
ehsankia wrote: post #123

Earlier quoted context omitted.

SpaceX themselves made a failure montage for Falcon 9 https://www.youtube.com/watch?v=bvim4rsNHkQ It's easy to forget how many failures that had, but look how far it has come, at this point I don't think they've had any major failures in 5+ years. Maybe a couple sea drone ship booster landing issues but zero mission failures in a very long time.

Neat, seems pretty much any mistake results in a fireball. Scott Manley and daughter have a fun song about other failures, "You will not go to space today", https://www.youtube.com/watch?v=Ayu0GsrvKQA I'm guessing the title is probably an allusion to this https://xkcd.com/1133/ .

I was half expecting:

"If an O-ring gets a bit too cold, you will not go to space today"

...but I guess that's a bit too dark, eh?

Re: SpaceX SN9 Explodes on Landing

#190

Post by ekianjo »

cmoscoe wrote: post #52
rglover wrote: post #28

Love seeing these tests for two reasons: 1.) Experiencing history in the making, especially knowing that the SpaceX team will eventually get it right. 2.) Realizing that even the best of the best have repeated failures and need to rely on iteration to get "there."

On the 'repeated failures' piece, that's somewhat new for aerospace. Traditionally, things would be over-engineered, and losing a test vessel would be considered a bad thing. SpaceX seems very content to blow up a bunch of rockets on their way towards not blowing up rockets. This seems to have caused at least part of their recent issues with the FAA, who seem to be less ok with explosions. It will be very interesting…

> that's somewhat new for aerospace

Because NASA does not launch anything anymore. If they were doing hundreds of launches per year you can bet you'd see failures the whole time.

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