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SpaceX SN9 Explodes on Landing

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Re: SpaceX SN9 Explodes on Landing

#172

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?

I don't know, but their reusable Falcon rockets went through a similar phase. They killed a lot of rockets before they got the landing right.

Re: SpaceX SN9 Explodes on Landing

#173

Earlier quoted context omitted.

I'm sorry, what? SpaceX are the undisputed champions of re-lighting engines. They've landed orbital rockets 73+ times, each of which involves multiple engine re-lights while falling through the atmosphere. Let alone gets it wrong "with regularity" — the Falcon 9 Block 5 is a remarkably reliable rocket. Anyway, landing Starship involves a bunch of things never before attempted: landing a fully-reusable second stage, l…

Today's crash was due to failure of one engine to restart. Briz and Fregat Russian upper stages are routinely restarted, with ~ 98 % success, same with Ariane EPS and Chinese Yuanzheng. It's doable, just not for Space-X.

You realize the Raptor engine is different from the Merlin used in Falcon rockets, right?

Re: SpaceX SN9 Explodes on Landing

#174

Earlier quoted context omitted.

Given two options 1. People doing analysis and hoping to check everything through engineering rigor and (hopefully) good assumptions 2. Test early and often, learning along the way until many positive tests have proven the system I'd prefer 2. Look at systems like SLS to see the schedule results of (1). No people were put on Falcon launches until almost 100 successful launches. I imagine a similar situation for StarS…

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 cargo shift from 1G towards the belly during the belly flop to a mix of gravity and pressure from the engines during the flip. While the view from the window would be "interesting" - the actual forces on the payload will remain a summed ~2G from these two axes (mostly from "down") during landing. This is similar to how the lift vector while rolling in an aircraft keeps you safely stuck to the floor (and not the walls) during jet flight.

Anyone flying an aircraft or space vehicle who doesn't secure their loads is going to experience some shifting of cargo. Of course that's why you have a small cargo compartment which physically restricts the movement of potential cargo. See how 747s secure cargo in large bins within a dedicated cargo hold for reference.

Re: SpaceX SN9 Explodes on Landing

#175
post #103

Earlier quoted context omitted.

That's likely to include the Nedelin catastrophe ( https://en.wikipedia.org/wiki/Nedelin_catastrophe ) - "The most recent estimated death toll, released by Roscosmos on the 50th anniversary of the accident and originating with agency engineer Boris Chertok, was that 126 people had died, but the agency qualified the number by saying that the actual number could be anywhere from 60 to 150 dead."

The Nedelin catastrophe was an ICBM test run of a rocket with hypergolic fuel that exploded on the launch pad; there was the 1980 launch pad explosion of a (military) sattelite launcher that killed 44 people and injured 43. The Russian version of the article says that hydrogen peroxide filters were produced with catalytic materials, this was later fixed after another launch almost failed in the same manner (it doesn'…

I've always loved Ignition![0] for the perspective it gives on working with the chemistry of this stuff.

[0] https://www.amazon.com/Ignition-Informal-Propellants-Univers...

Re: SpaceX SN9 Explodes on Landing

#176
Here is my favorite footage so far, by Cosmic Perspective: https://www.youtube.com/watch?v=Ep8XJanoFgw

This is 4k slow motion and it is gorgeous. The giant sheets of stainless steel floating down at the end are noteworthy, among other details.

Michael Bay has nothing on Cosmic Perspective + SpaceX.

Re: SpaceX SN9 Explodes on Landing

#177
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."

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/.

Re: SpaceX SN9 Explodes on Landing

#178

Earlier quoted context omitted.

I can't say I agree. They're developing this thing in stages; they've developed and tested the engines, they've developed and are testing launching the thing, they've developed and are testing the re-entry flop. They have partially developed the whole "landing" thing and if you're going to be testing the belly flop, you might as well put whatever you have with regards to landing through its paces as well. By having a…

You can't say a lot of things, so what! Giant team is not prerequisite for doing proper simulation before launching a gigantic rocket. I am being sincere. Nasa is in fact leading you on, to have some of their people wasting their time on this pseudo venture for optics. You seem to be using faith as your guiding light too rather than reason. It is not a prototype bicycle for experimental launch. It is all evident from…

You are so confident in your opinion and you are so incredibly wrong.

Pretty much every NASA engineer that has worked with SpaceX has been incredibly impressed by their methods. Literally every single one of their competitors, including nation states have started to change their who launch strategy because they saw no other way to compete with Spacex (and they are still failing) all of them have expressed how impressed they are with SpaceX.

You also seem to have a very trivial understanding of what SpaceX is doing and how it is different then what has been done before.

SpaceX is not just developing a the biggest rocket ever (double Satrun V lift-off thrust), or just the most advanced rocket engine ever, or just a new method of landing (very different from Shuttle), or a new type of heat shield (again different from Shuttle or SpaceX Pica), or a method of mass producing rockets. They are fully vertically integrated and they build and work on all of these and many other things at the same time.

Having one prototype explode is fine, because they are not just testing the prototype, they are testing the production of the rocket and optimizing the operations and everything mentioned above. The goal is to have the most advanced rocket of all time by a long margin, and be able to produce it cheaper then a current generation rocket, and operating it as cheaply as a airliner.

You can not simulate or plan anything so complex and get it right the first time. They are constantly learning and improving every single aspect. The engine team uses every test fire for new inputs and adjust their simulation and improve the design, the engine manufacturing team is trying to improve the cost per engine and the production quality, the rocket manufacturing engineers are constantly improving the way the rocket is built and later prototypes have these improvements, the materials team invents new materials and is measuring their performance on the prototypes, the operations team is trying to reduce the amount of work it takes set up a launch and I could go on and on like that.

Literally every prototype coming of the manufacturing line is a incrementally improved and usually cheaper then the one that came before it. The current SN8, SN9, SN10, SN11 are only small differences and with them they want to test the landing. They will be museum pieces once the landing is done, them blowing up generates real world data that can then improve their simulations. One of SpaceX 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. A test of a prototype is not just testing the design but also the manufacturing and quality control.

When you try to design something that has never been done before and is incredibly complex, and you have the requirement that it must be incredibly cheap and incredibly reliable there is no way you can simply design it on a white sheet of paper, simulate it and then simply have a mass production system of that vehicle. That is simply impossible.

And your claim that this is just 'cash burn' for no reason is equally wrong. SpaceX approach to engineering has routinely beat everybody in every single competition and usually by quite a lot. Nobody knows better how to develop something with a small budget compared to SpaceX. The whole Starship program so far, including new revolutionary engines, has cost less half of the much smaller Ariane 6, or less then a single year of the SLS program.

SpaceX is simply universally acknowledged as the most advanced rocket company in the world, and its not close. They are doing it this way for a reason, and they are a lot smarter then you.

Re: SpaceX SN9 Explodes on Landing

#179
post #126

Earlier quoted context omitted.

It's interesting to see that during Moon Race, in USSR there were 3 space design teams - Korolev's (later Mishin), Chelomey's and Yangel's - competing for resources, while NASA established centralized planning with everybody doing parts of the common project (with lots of money of course). It seems that "capitalistic" approach in USSR lost to more "communistic", central planning approach in USA.

Sure, but start of the "race" was pretty much the reverse - factions in the USA fighting for who will be allowed to launch the first satellite, resulting in the Vanguard fiasco. They had to bring in Von Braun in the end to do it, starting the centralization. And in the USSR Glushko also played along initially, designing R-7 engines that are in use till today basically. Only later he stopped and started demanding all…

> Glushko... started demanding all future engines to be hypergolic

I think Glushko owns a big share of Soviet problems with the Moon.

On the other hand, at the time the leading idea in USSR was that hydrogen is a rather advanced fuel (which, by the way, Glushko also supported at a time), and given good existing engines, rocket designers wished to use proven fuels. In general, and to compete with hydrogen in particular, Isp was an important goal, so rocket designers set goals to engine designers - make rocket engines with good Isp. There was created a conflict between high Isp/high pressure engines - as required - and large thrust engines, as was needed for big, Moon rocket. Glushko had the opinion that they won't have enough time to create large thrust high Isp engines with kerosene, only with UDMH/NO2 . Kuznetsov could only create relatively low thrust (1500 kN) high Isp kerosene engines, and those were late.

If Glushko tried, those engines could possibly work. At least Glushko experience with large thrust chamber of RD-270 helped later with large thrust 4-chamber kerosene RD-170.

Re: SpaceX SN9 Explodes on Landing

#180
post #50
post #6

When you look at the history of the space race between Soviets vs USA, one thing that is clear is the approach used by both countries to engineer their craft were very different. The Soviets would do design by testing and blow up many rockets and gather data vs the USA which would be more up-front about it's design and design testing before gong live. SpaceX clearly took the Soviet's approach to rocket design. EDIT:…

The Russians also were fond of “give it more gas”, which SpaceX has also embraced and Elon has called out before. The fuel is a real big piece of the launch cost but it’s far from the largest. If your rocket equation calls for a little extra fuel but in exchange you can use more reliable or at least less exotic parts, just do it.

The fuel isn't even "a real big part" of the launch cost. It's well under 1% even for SpaceX [0]. But rockets are already just about as big as we know how to make them: the expensive thing is not filling the tank 10% fuller, but building a 10% bigger tank.

[0] https://space.stackexchange.com/questions/8330/what-is-the-c...

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