SpaceX Starship Prototype Finally Aces Pressure Test (extremetech.com) 46
The Starship SN4, a prototype of a SpaceX ship meant to one day take humans to the moon and Mars, has remained intact during pressure testing. ExtremeTech reports: Last year, SpaceX successfully tested the "Starhopper" prototype with one of the company's new Raptor engines. However, the full-scale prototypes haven't fared well in pressure testing. SN1 blew its top in February, and both SN2 and SN3 suffered similar fates during the "cryo" testing phase, which simulates a full-pressure tank in the vacuum of space. SN4 is the first version of the rocket to survive that test.
The success of the SN4 prototype is a big step forward for the Starship program. The next step is to set up a static fire test with a single Raptor engine on the SN4. That could happen as soon as next week. Assuming it's still in one piece, SpaceX will then conduct a brief flight up to 500 feet (150 meters) before setting down. Elon Musk says that the next variant (predictably called SN5) will feature the full-scale tank and a trio of Raptor engines. The final design calls for six Raptor engines on the Starship and a further 37 of them on the Super Heavy stage.
The success of the SN4 prototype is a big step forward for the Starship program. The next step is to set up a static fire test with a single Raptor engine on the SN4. That could happen as soon as next week. Assuming it's still in one piece, SpaceX will then conduct a brief flight up to 500 feet (150 meters) before setting down. Elon Musk says that the next variant (predictably called SN5) will feature the full-scale tank and a trio of Raptor engines. The final design calls for six Raptor engines on the Starship and a further 37 of them on the Super Heavy stage.
Would be great to know what the problem was (Score:2)
I'm really curious what seemed to be the problem that took out a few prototypes before they arrived at a working tank... was it just about the welding? Does this test basically mean they will be all sound moving forward, or is there yet more to get stable in the manufacturing process....
Re:Would be great to know what the problem was (Score:5, Informative)
From what I understand, SN3 broke because of bad testing methodologies... They filled the top tanks without the bottom tanks filled and the bottom tanks crumpled because no pressure to keep them rigid. So maybe not tons of actually difference between 3 and 4... Besides that, just getting better at welding and such probably.
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So what happens with a payload on top of the tanks? Is there extra structure to take the weight bypassing the tanks, or can the payload only be integrated after fuelling?
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Not sure, but these are also just testing prototypes... I also bet that the payload weighs less than the fuel. May be as simple as keeping a certain min pressure in the tanks with nitrogen before final fueling also.
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I also bet that the payload weighs less than the fuel. .
Yup. Payload c 100 tons, fuel and oxidiser about 900.
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Your car is not tasked with flying into orbit. Flying vehicles have a strict weight budget, and orbital vehicles have the strictest weight budget of them all. Most flying vehicles use structural members as part of the tanks. For example, most airplanes use the wing skins and spars as the walls of their gas tanks.
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Neither are Grain Silos
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"Is the pressure vessel structural?"
Yes, from what I understand virtually all liquid fueled rockets utilize pressure in their tanks as some level of structural component. I think I remember reading an article a while back about how the Falcon 9 first stage was one of the few rockets that could be moved around with it's tanks unpressurized, extra important I'd imagine since they transport them on roadways (see video). While I think they've gotten away from full fledged balloon tanks for most applications t
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Wow, I hadn't even thought of that.
It's especially surprising since the Falcon 9 first stage is the one that's supposed to come down in one piece, and must be fairly empty for most of the descent and practically dry by the time it clinks down on the landing pad.
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So what happens with a payload on top of the tanks?
SpaceX likes to "load and go” , fuelling just before launch so the propellant is still super-cold. So payload will be on first.
But payload is much lighter - planned to be 100 ton initially, with 1200 ton of propellant.
I reckon that in the test, they just forgot that liquid nitrogen is heavier than liquid methane :-)
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I reckon that in the test, they just forgot that liquid nitrogen is heavier than liquid methane :-)
Someone must've put a decimal point in the wrong place or something. I always do that. I always mess up some mundane detail.
Re:Would be great to know what the problem was (Score:5, Informative)
It was apparently a little more subtle than that- they did not take into account the higher density of LIN vs LOX, and the reduction of pressure in the gaseous lower tank as it cooled caused by the cryogenic upper tank.
As for payload... it is small relative to the weight of the fuel.
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The rapid prototyping is being welded by human welders, but I believe they plan to move to more automated fabrication techniques once the design has been proven. Compared to Boeing who computer-tested and built the entire fabrication rig before even building their first test rocket. Both will get you to where you want to be, but the latter is the more cautious approach.
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Re:Would be great to know what the problem was (Score:4, Interesting)
This test was only to 4.9 bar [twitter.com]. They apparently decided they want to be able to test some other things with this one. 4.9 bar is good enough to do a hop. I'm sure we'll get many more blowups, including some with real fuel, before it gets to orbit.
One thing that I'm really curious about is the reusability aspect of the tanks at this point. I'm pretty sure they are pushing the tensile strength (even the cryogenic tensile strength which is much higher) of the current steel very close to if not past the point where some of the deformations will not undo themselves when the pressure is removed. So, multiple pressurizations to the higher levels required for orbit may be in question. Later, they're going to switch to their own tailored blend of steel. I think this is part of the reason.
Re: Would be great to know what the problem was (Score:4, Informative)
The reason the goal is to reach 8.4 bar is because they need to run the thing at 6 bar in practice. The 1.4x multiplier is because it gaurentee that at 6 bar there wonâ(TM)t be any significant fatigue wear over multiple reuses.
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Re:Would be great to know what the problem was (Score:5, Informative)
Mk1: Blew its top [twitter.com] during pressure testing, apparently inconsistent welds caused by outdoor assembly in the wind. Windbreaks and indoor welding implemented.
SN1: Thrust puck failure [twitter.com] during cryo testing, design improved
SN2: Test of new thrust puck design succeeded, prototype retired
SN3: Implosion [youtu.be] during cryo test, due to tank pressure configuration issues
SN4: Passed cryo pressure test, single-engine static fire and 150m hop test expected
SN5: Readying for assembly, aim is for three-engine 20km flight
List of prototypes [wikipedia.org].
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"was it just about the welding?"
Yes.
Aren't they blowing them up on purpose? (Score:2)
I thought Elon was intentionally blowing them up by pushing them past their designed pressure thresholds to see exactly when they would fail, and which part would fail first.
Good engineering in my opinion.
Go Elon go!!!
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There is good precedent for that .If you want to know where it will break, you need to test it.
https://www.youtube.com/watch?... [youtube.com]
Welding (Score:2)
I don't know if this was the problem, or not, but welding up these huge thin-wall structures with is still a very difficult issue. This was a pacing issue with the Saturn V (as documented in this excellent book):
https://www.history.nasa.gov/S... [nasa.gov]
Stainless is probably easier than aluminum, but for a low-experience outfit like SpaceX, they likely have to re-learn a lot of stuff.
Re:Welding (Score:4, Interesting)
Re:Welding (Score:5, Informative)
Re: Welding (Score:4, Informative)
This is precisely why they are currently setting up planishers at their production facility - to be able to cold work the welds after the fact.
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Before somebody says "Low-experience? They've built a huge number of rockets!" consider that their Falcon 9 and Falcon Heavy rockets use friction stir welding, they don't actually have as much experience with regular welding.
Finally? (Score:3)
What's with the "finally" in the article headline? From what I see this development is proceeding at a breakneck pace.
How long would it take to get a modern airliner from concept to this stage? I think it would be longer.
Re:Finally? (Score:4, Interesting)
It gets better.
Musk has been hesitant to put a date on that with the recent setbacks, but previous reports pegged 2023 for the launch.
This author really dislikes SX &/or Musk. The fact is, that Musk KNOWS that this is R&D and that it will take time. Personally, I thought that he was being very generous on time with 2023.
duh, Agile Methods (Score:5, Insightful)
Does anyone else find it weird that SpaceX is rapidly advancing toward domination of the commercial space launch industry using extremely rapid design/test iterations but that Boeing, which has the most to lose, its still using antiquated waterfall instead of agile methods?
Why is it evident to everyone except Boeing that Agile, Scrum or whatever flavor of rapid prototyping and testing which Musk uses at Tesla, SpaceX and the Boring Company gives him a massive advantage over his competitors? Musk is quite vocal about it. He's like, I am totally kicking your asses and I am explaining to you how I am doing that. Meanwhile Boeing has no idea how they are getting beat or what to do about it. Question: How much are the clowns who run Boeing paid to to mismanage the company? Answer: So much that they don't care what happens to it. Is there any hope of them being replaced before Boeing's overly-expensive rockets are priced out of the commercial space launch business by SpaceX, Blue Origin and probably some younger innovative upstarts such as Relativity Space?
The really weird thing is that if you Google "Boeing Agile" results are a mix of scary agile stories, job advertisements at Boeing for scrum masters and accounts of their corporate failures (e.g. 737 max). No evidence that Being is actually rapidly prototyping/testing, but instead merely updating their management-speak vocabulary for 2001 in 2020.
Boeing can still sell aircraft, but if that industry hits a disruptive innovation curve with pilotless automated navigation and flight of mid-range electric commuters when battery performance improves further, then Boeing will take another big hit. It could be the next Atari, Sears, or Eastman Kodak; All once dominant businesses in their respective industries and now insignificant bit players and vestigial trademarks. Like Boeing, the corporate culture cultivated by market dominance prevented adaptation necessary for survival under changing market conditions and with advancing technology.
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Resting on your laurels only works for so long...
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I think you are totally right. As to the differences between SpaceX and Boeing. Musk is a man with a mission and with passion. For him it's a personal goal. He has the resources and he wants to make it happen. Whereas with Boeing, people get payed to be smart-asses and exactly as you say, they couldn't care less as long they got payed.
To change this wouldn't be trivial. Bonuses have a bad reputation because they are usually only expressed in short term goals and calculated using money, not results, as prima
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Boeing doesn't have much to do in the launch vehicle space right now. They're building SLS, which is a huge expensive mess, but that's basically a government run project without competition, so no surprise there.
ULA (United Launch Allian
Re:duh, Agile Methods (Score:4, Informative)
While you're right that a comparable ULA launch is only around 40-50% more expensive than a new Falcon 9 launch, and with a higher reliability too, that's not the whole picture.
First of all, that's only for a NEW Falcon 9. Since the first stage is reusable, a re-launch is substantially cheaper. How much cheaper? We don't know. SpaceX is a private company, so we don't really know what their internal financials are like. We know they charge 20% less for a relaunch, so it's at least that much cheaper. It's probably closer to 50%-60% cheaper, since the first stage is the majority of the cost, but they've also been pulling them apart for analysis each time, so currently it's probably on the more expensive side, but will get cheaper as they put more effort into making a cheap launch pipeline rather than supporting their R&D goals.
Speaking of SpaceX's financials being private, we don't know how much profit SpaceX is making. We do know it's a lot because programs like Starship and Starlink aren't cheap and that money is coming from somewhere. The figures we were talking about earlier were all the retail costs, not what SpaceX is paying. We also know that SpaceX has some amount of price-setting power, because they can more or less set the price as long as they outbid companies like ULA. Since their costs are radically lower, they are in a position to ask for huge profit margins, both in terms of pure profit they can pour into programs like Starlink and more expensive processes that give them long-term benefits, such as pulling apart their rockets after flight for analysis instead of being worried about the margin on a launch. Frankly I'm surprised their retail launch costs are so low, since they could probably charge 80% of what ULA and other competitors do and still get most of the launch market. We also know they're pouring essentially all that profit into improving the company, so their long-term performance is likely to be stellar.
Speaking of their long-term performance, once Starship is complete it will have a profound effect on the launch market. Each launch of Starship will be equivalent to somewhere between 6 and 25 Falcon 9 launches (the ambiguity is because the current plan is to launch the Starship's 100 metric ton cargo "to anywhere", but lets be pessimistic and go with 6). Since it's completely reusable, rather than just partially reusable, it will be a lot cheaper to launch too. It's very difficult to do a proper analysis of the launch costs of a system that doesn't exist yet, but the $2 million per launch figure that SpaceX has cited is not outrageous in the long run (and even if it cost the same as a Falcon 9 to launch it would still be profoundly cheaper). Assuming $2 million per launch, spending the $110 million that a ULA launch would cost on Starship launches would allow the buyer to launch approximately 5.5 million tons of cargo into orbit, which is equivalent to 366 Falcon 9 or Atlas V launches, so each Starship launch would cost around 0.2% of what an Atlas V launch would cost (or around 0.4% of what a current Falcon 9 launch costs). It's 13 International Space Stations worth of payload...for the cost of one Atlas V launch. There's simply no competition on price there, and unless ULA has something lined up in the next 5 years that is going to have an equally profound impact, they aren't going to have any customers, beyond possibly some extremely niche things like launching nuclear material safely.
Even there, I think the solution for launching nuclear material is going to change. Having 100 metric tons of cargo capacity is such a game changer that it opens up all sorts of new possibilities that are currently absurd. For instance, perhaps you could launch nuclear material inside of an extremely heavy armored container, one which could sustain the ship exploding and crashing into the ground at high speeds without leaking radioactive contaminants. Even if such a container weighed 99 tons, you could still launch 1 ton of material safely for a fraction of the cost (366 tons for
Passenger Starship to orbit? (Score:2)
Wow! I never heard the numbers broken down that way - at 2million dollars per 100 tons that opens up a whole lot of possibilities. Including passenger service to Earth orbit.
Breaking out the envelope to do some calculations I started with an empty 747 at around 180 tons. That carries 660 passengers. Assuming that is about right for a passenger to spacecraft weight ratio to orbit (pretty rough estimate), we get under 600 pounds of spacecraft per passenger. Take that together with passenger and luggage
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Indeed, it may still be very expensive compared to travel on Earth, but such a massive price drop per passenger is going to have a profound effect on human access to space.
I think in the earliest phase, it'll be somewhat similar to today but with a lot more people in orbit, on the moon, etc. More or less everyone in space will be there either as an employee or researcher, or as a relatively rich tourist (no longer just billionaires, and anyone can conceivably save up for it eventually).
However, once we buil
Re: Slashdot Bias (Score:4, Informative)
Funny way to "Ace a test" (Score:1)
Funny way to "Ace a test" - Fourth time lucky sounds more like it.
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Not to nit pick, but ... (Score:1)
Last year, SpaceX successfully tested the "Starhopper" prototype ...
Shouldn't it have been called "Planethopper"? The other name sounds like the joke re-name after a serious navigational error.
Single data point? (Score:1)
So they have a single case of it succeeding,
and many cases of it failing badly . . .
That doesn't exactly sound like the six sigma statistical reliability I would like to see from something that goes on top of a controlled bomb that carries me to a place with no air and massive radiation, now does it? ;)
Re:Single data point? (Score:4, Insightful)
What do you mean, "it"? The previous prototypes were older designs, some manufactured under worse conditions and certainly tested with less-mature processes. It's not like SpaceX built N identical vehicles and then tested each one until one worked. They built one, tested it until they found the flaws, changed things, and tried again. They repeated that process four times, until they got to the current vehicle, which passed a test none of the others had. So, now they'll do more tests, probably run into further problems (and even if they don't, this one is only intended for a short, single-engine hop), and incorporate what they've learned into the next one.
It's iteration, not just trying the same thing over and over again until it works. This isn't a production model, it's an early prototype that they're still researching and developing. In R&D, if you aren't getting failures, YOU AREN'T TESTING HARD ENOUGH.
I take it you've never created anything significant from the ground up in your life? You sure as hell don't achieve "six sigma statistical reliability" on your first few attempts at something this complicated!
Re:Single data point? (Score:4, Funny)
In R&D, if you aren't getting failures, YOU AREN'T TESTING HARD ENOUGH.
Just a slight correction. This is "aerospace R&D". If you aren't getting failures, you overbuilt the damn thing and need to remove some metal somewhere, 'cause it's too heavy.