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SpaceX SN9 Explodes on Landing
- d_silin 6y agoIllustration how "move fast and break things" in aerospace domain works.
- ericd 6y agoHonestly, my main takeaway from this testing and Falcon 9 dev has been that we should be doing a whole lot more of that than we have been, at least until there are human passengers. The contrast in rate of progress with eg SLS is stunning.
- api 6y agoAlso keep in mind that it's already doing what pre-F9 rockets did: go up. The RUDs so far are on landing attempts. Landing is a whole lot harder.
- unanswered 6y agoUnfortunately it seems like traditional aerospace now has a very big lever to pull to get SpaceX shut down: public opinion following the reasoning "rocket go boom. go boom bad. rocket bad".
- m4rtink 6y agoOr actually the other way around - what will be in the news, another successful Atlas V or Ariane 5 or a nice big powerful explosion during a test flight ? That can bring a lot of interest from people not to mention disseminate the news about Starship far and wide.
- api 6y agoIf that was going to work it would have already. SpaceX has been blowing up rockets for years.
- simonh 6y agoThere's a key difference though, Starship is intended to carry people. The correct comparison for this isn't landing Falcon 9 boosters, it's landing crew capsules.
- Cogito 6y agoFalcon 9 was also intended to carry people. Starship is a more capable upper stage then Crew Capsule, part of which means that it can launch itself (at least suborbital). They aren't trying to qualify these prototypes as human-rated, they have to finish the design work first! For this pase of testing it's much more accurate to compare to Falcon 9 than Crew Capsule.
- simonh 6y agoOh come on, the Dragon capsule brings people back to the ground, not the first stage booster and it's landing these things that is the issue so far, not launching them. All I am saying is that this vehicle, in it's final qualified form, will be landing human beings on the deck back here on Earth. That's the objective, so it's viability and reliability needs to be considered in that context. For an F9 first stage a failure rate of 1/10 is fine. One out of 20 is outstanding. For Starship, these things are intended to carry a hundred paying passengers or more. The failure rate needs to be lower than 1 in a thousand. Much lower.
- Cogito 6y agoI mostly agree with you, but I'm not sure on why you're focusing human passenger safety on this at this early development stage, as if it's somehow a reasonable thing to focus on. Launching these things IS the issue so far, by far the main objective of these tests. Landing them would be nice, but the primary objectives are to launch the whole thing (in particular including aero surfaces and multiple engines, as compared to previous prototypes) and test the various novel maneauvres that they are attempting. That almost all the objectives are being met in these tests is a testament to how good SpaceX is getting at launching flying water tanks, and how hard the entire flight profile is to achieve (launch, belly flop, landing flip, landing). In the anticipated human-rated version of Starship safety will be immensely important, but this is nowhere near being that thing! This was only the second prototype that even started to look like 'Starship'. We have no idea what a human-rated version would loook like, and a human-rated Starship is definitely not the objective of these tests. The Starship prototypes they are testing at the moment are much much much closer to a Falcon 9 than a capsule. Specifically the systems and processes they are testing all have fairly direct parallels in Falcon 9, and almost no correspondence to a capsule. For example, Falcon 9 and Starship both have: super chilled propellent tanks, multiple large rocket engines, active flight control systems, engine relight, active aero surfaces, and powered landing. Starship and the capsule both have... heatshields? Human passenger safety will be immensely important for Starship, but to focus on it at this stage of development would be immensely premature.
- codefreakxff 6y agoWell. Yes. It appears to be a fully functioning launch vehicle and just as reusable as its predecessors, don’t see much downside in making the landings more “interesting”. When they work out the dynamics of it then they really have something that will revolutionize launches
- Already__Taken 6y agoWe knew this since watching how much the Russians got done in the time they had for the resources. Put the engineers together with the manufactures, build often, test more.
- wp381640 6y agojust don't sit near the launchpad
- krisoft 6y agoAnd if anyone believes wp381640 is joking, this lesson seems to have been learned the hard way: https://en.m.wikipedia.org/wiki/Nedelin_catastrophe https://en.m.wikipedia.org/wiki/Nedelin_catastrophe
- Breza 6y ago"54–300 deaths (exact number not known)" Wow, I can't imagine a disaster happening in the United States where we barely even knew the order of magnitude of fatalities.
- kiba 6y agoThe way to make them more reliable is not to put human passengers while increasing the iteration rate and manufacturing speed. The two ways I heard to get really reliable products is to get good at manufacturing them reliably at scale or be really slow and really careful in making them one at a time.
- MR4D 6y ago‘We may crash, but at least we do it with style!” Somehow that should be an Elon tweet.
- jerf 6y agoIf you happen not to have seen it, "How Not To Land an Orbital Rocket Booster": https://www.youtube.com/watch?v=bvim4rsNHkQ https://www.youtube.com/watch?v=bvim4rsNHkQ from SpaceX.
- walrus01 6y agoThey landed a lot of falcon 9 first stages without legs on the water, vertically, to test the control system. And a number of attempted barge landings with legs failed, before the first successful landing. Now it's almost a routine thing.
- kevin_thibedeau 6y agoThat's probably what FAA was peeved about SN8. They might have been expecting a water landing and didn't like that an unproven rocket was sent back to dry land.
- simonh 6y agoNo, it was the last minute engine swap.
- twicetwice 6y agoIs there a source for that? I've heard tons of speculation & I'd be very interested to know if the mystery has definitively been settled!
- Laremere 6y agoThe Falcon landed on land before it landed on a barge. Obviously landing on a moving/swaying barge is harder, however they had to start with water landings because they hadn't proved they could aim at their target. Once they crashed into the barge a few times, the FAA was convinced they'd only blow up the landing pad and not drop it on something else in the launch complex. So they got clearance for landing on land. The early starhopper/starship flights proved what they needed to that they'd generally land on target.
- lrossi 6y agoYou could also call this TDD.
- tectonic 6y agoThis is why we test. (In this case, header tank helium pressurization and more thermal tiles.) At least they didn't hit SN10! Summary tomorrow in this week's Orbital Index (https://orbitalindex.com https://orbitalindex.com).
- Florin_Andrei 6y agoWell, they popped a bunch of Falcon 9s until they got those right.
- trasz 6y agoI wonder what's that tiny thing that seems to have broken off some two seconds before it hit the ground?
- bdamm 6y agoIndeed, there were two. Two objects broke off from the ship before impact, one just before the first swing of the pendulum and one just after.
- jansan 6y agoAlso, there was an unusually large flame at the end of the liftoff. Maybe that already sealed SN9's fate.
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- deleted 6y ago[deleted]
- Gh0stRAT 6y agoWatching it in slow motion, it looks almost like pieces of insulating foil.
- Diederich 6y agoFailure with one of the engines on re-light: https://twitter.com/MurkyWanders/status/1356703469986586626 https://twitter.com/MurkyWanders/status/1356703469986586626 "I bet they needed that." As others have noted, SN10 is standing by. Somewhat uncomfortably close by: https://i.imgur.com/F9rsBbD.png https://i.imgur.com/F9rsBbD.png It's so exciting to be a spectator of these events.
- _Microft 6y agoSN10, wenplop? The debris does not seem to come from next to the failing rocket engine but from the outer wall next to the engine that was not used in the landing attempt. It appears first shortly before the clock shows 6:21.
- Florin_Andrei 6y ago> SN10 is standing by. Somewhat uncomfortably close by That was my immediate comment at the end. Pretty confident they are.
- 2OEH8eoCRo0 6y agoThis was my thought even before launch. SN9 could explode on the pad.
- emteycz 6y agoI though they pump it with fuel shortly before start?
- nickik 6y agoNot sure why you got downvoted. When talking about 'explode on the pad' it usually refers a rocket blowing up right when the engines lights up before it lifts off. Or alternatively during fuelling, SpaceX had that issue during Amos-6.
- 6y ago
- mempko 6y agoWhen 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: This is not a negative thing. Soyuz is pretty darn safe because of the approach they took.
- the-dude 6y agoComrade! This is 2021, nothing positive about Mother Russia may be mentioned on this capitalist cesspool.
- mempko 6y agoIt's funny because the Soviets did it right, in that they funded smart people and gave them control. The Nasa's approach was to have people create proposals and get approval for funds. We have forgotten that the "fund smart people and let them do what they want" is the best approach. Look at Xerox Parc, Bell Labs, etc. Nasa's modern approach with SpaceX and other companies seems to reflect these hard learned lessons.
- the-dude 6y agoIIRC Zhe Germans were pretty hands-off with von Braun as well.
- PeterisP 6y ago"fund smart people and let them do what they want" - well, that's not exactly how it worked - for example, while Korolov was mostly able to get the resources he needed in the 1950s, in the early 1940s he did his engineering work on bomber design from a prison labor camp (which is a bit far from "let them do what they want" or "give them control") after losing most of his teeth from malnutrition during forced labor in a gold mine. This probably provided a perspective for him of what the limits of "do what you want" are in reality.
- Diederich 6y agoAnd that's why you have an assembly line for Starships: https://i.redd.it/dmr9bjhpcee61.jpg https://i.redd.it/dmr9bjhpcee61.jpg (SN9 lacking the RUD symbol in that image of course.)
- 6nf 6y agoAlso note that BN1 (which is the booster stage) is getting close to completion! I wonder when we'll see one of those fly?
- walrus01 6y agoI saw photos a few days ago that the base piece of the BN1, which will need to hold the weight of the entire thing and thrust mounts for the engines has been spotted at boca chica.
- batterylow 6y agoExplosion happens just after 12:45... I'm sure they've collected useful data.
- joshxyz 6y agoWoops unscheduled disassembly <3 SN10, we're waiting!
- Leparamour 6y ago>Woops unscheduled disassembly <3 The one where the front fell off? https://www.youtube.com/watch?v=3m5qxZm_JqM https://www.youtube.com/watch?v=3m5qxZm_JqM
- hikerclimber 6y agonice! hopefully we have more spaceships which explode and china and russia beat us to space.
- rglover 6y agoLove 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."
- cmoscoe 6y agoOn 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 to see if this iterative approach leads to more reliable rockets down the line!
- bondolo 6y agoThe FAA seems to be concerned with exploded bits falling on innocent people. You are welcome to blow up your rockets all day long if you aren't putting other people at risk.
- sneak 6y agoThe SpaceX rockets don't fly anywhere near people. Nobody is underneath any part of their flight path or within any possible destruction radii.
- elmomle 6y agoPlenty of American rockets failed, especially early on! https://www.youtube.com/watch?v=13qeX98tAS8 https://www.youtube.com/watch?v=13qeX98tAS8
- DennisP 6y agoAnd SpaceX has blown up ten Falcons on landing attempts.
- breatheoften 6y agoWas it camera angle that made it appear to be so perfectly flat (top and bottom of rocket at same altitude) when it was in free fall or was that actually the target free fall orientation?
- NortySpock 6y agoI presume it was the target orientation since they held it for so long, had they wanted to actively leave that orientation earlier I assume they would have done so. Especially subsonic I assume their orientation does not matter a whole lot when just trying to fall with max drag. Not sure how much energy they'll save doing the flip maneuver earlier though, seems like they want max drag as low as they can go, then flip to powered flight at the last moment possible -- and their problem seems to be keeping the engines lit.
- JshWright 6y agoYeah, it does a "belly flop" during descent, presenting as much area as possible to the airflow, reducing its terminal velocity.
- ashtonkem 6y agoI’m not sure if I’d call that a landing.
- gridspy 6y agoIt landed. It just can't fly again. ;)
- mongol 6y agoI am impressed by the camera angles. How do you think they filmed the last parts? With a drone?
- gridspy 6y agoThe initial star-hopper ("Water tower") is several stories high and covered with cameras pointed at the launch site. That would be my guess.
- 6nf 6y agoAnother amazing test flight! Can't wait for SN10. I understand they have already started the last step of construction which is fitting the Raptor engines to SN10. Should be ready to fly very soon.
- GizmoSwan 6y agoYou loved the quality of the explosion. Did you? Bigger the explosion, the more promising is the venture! NOT
- reasonabl_human 6y agoI loved the explosion. These guys get stuff done. Move fast and break things
- GizmoSwan 6y agoIt should not have been an experiment leading to explosion at this stage. You are not seriously willing to justify the explosion, are you? I hope that you are being sarcastic. The experimental flying of rockets of this size are the 1960s thing. They should have acquired proper specs by now.
- reasonabl_human 6y agoIt’s been a few days and other people above have already put you through the ringer on this, but funny enough the 1960’s work style, of the soviets specifically, is ideal for rapidly advancing rocket tech. Or any tech, for that matter! They iterated and flight tested early and often. The soviets only lost the space race because they ran out of resources, as this is an expensive approach, but SpaceX is back-stopped by Elon + the US gov via contracts + they already have production flight revenue and wildly successful products. I won’t be able to do the explanation much justice in a paragraph here but Google around about how the Soviet approach to rocketry was far superior than that of the US and you’ll uncover plenty on the topic. SpaceX is executing that same style of engineering development, marrying the ‘move fast and break things’ tech company ethos with aerospace engineering. That’s why they’re so revolutionary: aero is typically riddled with red tape and risk aversion... they take the Silicon Valley approach of moving fast and breaking things, along with keeping as much engineering in-house as possible to cut down on expenditure, lead time, quality control etc. etc. Source: used to work on SpaceX’s only commercial crew capsule competitor, Boeing’s Starliner, down at the Kennedy Space Center.
- hyperion2010 6y agoFor 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.
- walrus01 6y agoIt's my understanding currently that a 'production' starship will have three central engines optimized for sea level, and additionally three vacuum-optimized engines installed around its inside base perimeter.
- gridspy 6y agoIndeed. Those engines are currently missing partially because there's no reason to lose more engines than strictly necessary and also because they only need that much thrust when the fuel tanks are completely full. If they decide to lift the StarShip from sea level completely full they will need to use only sea level engines (not vacuum optimized) or risk engine damage. Of course in production the booster will put the StarShip (upper stage) well above sea level.
- tobmlt 6y agoBuilding anything that can deal with a catastrophic engine failure at powered landing time is probably out of scope for the foreseeable future. Caveat: Did I mistake the scope here? I’ve not checked to see at what point in the trajectory the engine actually failed as I am at work. *deal with - meaning land successfully anyway
- aeternum 6y agoThe issue is that the Raptor engines can only throttle down to 40% which represents a large thrust-to-weight ratio when you have basically just an empty tank. There is also a startup time for each engine, so if one fails Starship will likely hit the ground before they can light another. There are enough engines that a failure on ascent can be handled gracefully but landing is another story.
- phkahler 6y agoSoon after SN8 Elon tweeted that they knew the problem. So they quickly added Helium to pressurize SN9, which is a bandaid given their deliberate elimination of Helium and the fact there isnt any on Mars. Now we see what looks like even worse relight capability. I wonder if recent departures are related in some way. They failed plenty before, but this seems different.
- Me1000 6y agoThat's a lot of speculation. We don't yet know why one of the Raptor engines failed to relight. The Raptor is a very new engine with only a handful of minutes of flight time. Keep in mind they also replaced a couple of the engines before the flight. I imagine SpaceX still be considers them development engines. You can also see some debris fly off of the bottom of the rocket just as it's performing its flip maneuver. With SN8 Musk tweeted casually about it, but he's apparently taking a hiatus for a bit.
- phkahler 6y ago>> That's a lot of speculation. Yes it is, but I didn't speculate as to how that might be related. It is a bit of a stretch.
- omgwtfbyobbq 6y agoCan they relight sooner to improve their odds of landing successfully, or is the window for when they can relight relatively small? Or does it not matter because a few more seconds won't increase the chances they'll be able to relight?
- jacquesm 6y agoThat's a good question actually, given that they had another engine as well. Or maybe light up all three and then shut down the one they decide not to use. But these are all in the 'why don't they' category, SpaceX has some pretty clever cookies, experts in their field, the chances that anything we can think of has not been thought of by them are nil.
- yellowapple 6y agoI'm reminded of the story of two economists walking down the street. One sees a dollar bill on the ground, and the other decides "that can't be right; if there was a dollar bill on the ground someone would've picked it up already". Not saying that a bunch of random folks on HN are seeing dollar bills in this analogy, but I've never quite been satisfied with the "if we're thinking of it then they probably already tried it" explanation :)
- avmich 6y ago> but I've never quite been satisfied with the "if we're thinking of it then they probably already tried it" explanation :) Same here :) . I'm still unhappy with their decision to use toxic propellants on Crew Dragon - I'm sure they could use something much more benign.
- simonh 6y agoTo be fair they selected it quite some time ago now. There's a lot of very promising research now though, so hopefully they will have better options available down the line.
- notjustanymike 6y agoThese damn JavaScript powered rockets keep crashing on bootup!
- avmich 6y agoDon't worry, they also fly a-plenty in the meantime, see Falcon-9 list of flights.
- johnisgood 6y agoOn a serious note, what programming language do they use?
- skissane 6y agoSome years ago they said the flight software for Falcon 9 and Dragon is written in C++ https://old.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_software_engineers_we_launch/c8bpr00/ https://old.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_... It seems likely the Starship flight software is a derivative of Falcon 9’s, so it is probably C++ as well
- BurningFrog 6y agoI'm very impressed by how it's coasting on the fins down the atmosphere. I had never even heard that idea discussed before I saw SN8 do it. Of course, they'll have to land some other way on Mars or the Moon.
- gridspy 6y agoFortunately the force of gravity is much lower on both these bodies so I imagine the belly flop becomes less important. On earth it's also about spreading the heat of reentry over a larger area. Fortunately on Mars (I believe that) the heat of reentry is even less of an issue than here on Earth.
- onethought 6y agoIs that right... at orbital velocity I think Mars entry is a problem. Are they planning on landing starships on earth? with Orbital refuelling couldn't they just land it like a Falcon 9 (I mean I guess that'd be super inefficient)
- gridspy 6y agoYes, they plan to land "tanker" starships directly back on earth after they have transferred their fuel to another vessel. They plan to land passenger ballistic re-entry starships which fly without a booster directly to another city on earth in <30 minutes. These are going relatively slowly. They plan to land orbital starships, which is like landing the dragon capsule. These are going far faster than the falcon booster ever goes. The second stage (on top of the falcon) never lands, it's disposed of every mission. The StarShip (top half) is essentially a reusable second stage. The Starship mars or moon editions will remain in orbit and never land on Earth again after initial launch. These do not need hardware for an Earth descent and will rely on refuelling. The Moon edition will have no heat-shield tiles (no need for atmospheric entry) and special thrusters half-way up. You are correct that interplanetry velocities are very high, so yes... a Mars entry at Earth-Mars transfer velocities is likely to be quite ... exciting. I can't remember how exciting though.
- 6y ago
- jzer0cool 6y ago(1) I think that is a "hard" landing ;) I say it it the mark. (2) The Question: I ain't no rocket scientist, but even if the engine failure had turned on, did the engines all just turn on quite late? Just trying here some crazy college physics so not sure if this checks out but, here goes. Again, just for fun. If it takes X: (summation of thrust) to fly that high over x seconds, then it would take the X + some at the very last 4 seconds I saw engines turn on for soft landing. Are we capable of having enough thrust in the last 4 seconds? Maybe try earlier so there can be more lead way in case of failure? === Freefall: 11:06 (all estimates) 12:45 (still free fall, engines off and preparing for vertical) 12:48 (engine on, flipping for vertical) 12:50 (vertical) (4 seconds left to apply thrust) 12:54 (crash landing) I have about 104 seconds of free fall, and 4 seconds left when engine turned on. Is 4 seconds enough? Just intuition and genuinely wondering ... Just for fun - does my physics checkout (at freefall)? vf = 0 + (1/2) * at^2 vf = 9.8m/s^2 (108s^2) = 57153.6 m/s = 127848.9621 mi/hr (yea, ignoring at moment drag/terminal, physics ;) === vf = (1/2) (F/m)t^2, F=ma (vf2m) / t^2 = F (Thrust required) Again, just for fun. Don't kill me. Physics, it been a long time. If it's right, Elon, are you hiring? EDIT: SpaceX, Tesla to the -moon- mars!
- onethought 6y agoI think they are doing it the most efficient way (similar to the Falcon 9) - that is with 0 hover. The timing doesn't mean much because an entire engine didn't light... so it would have flipped up right faster and slowed down faster. Timing on a failure case doesn't really work. Also it was only 1 engine compared with two, they could gimbal independently and have one course correcting while the other decelerates
- gridspy 6y agoNice analysis. I can answer your question by illuminating two major points you missed. 1. The StarShip reaches a terminal velocity (in "the bellyflop") of about 200 km/h downwards and remains at that velocity until the "flip maneuver" at the end. That's essentially a free force vector upwards due to drag which is free thrust on descent. 2. The weight of fuel reduces drastically on ascent which is why less engines are required as the StarShip soars higher into the air (they shut down when one reaches the 40% min thrust) You'll see during the hover at the top that StarShip balanced on one engine for some time without moving. So that is the thrust required for station keeping. What we saw here was a combination of reaching a target location and burning excess fuel. --- So, landing burn is (supposed to be) done with two fully throttled raptors, which is essentially 4x the hover thrust. Here with SN9 you see what happens when only one of those raptors is actually working. Here is an Excellent SN8 (not SN9) video with carefully reconstructed telemetry (based on pixel counting video references) and you can see the velocities on descent. Rewind the video for full detail: https://youtu.be/XJZ7VWzqtJM?t=867 https://youtu.be/XJZ7VWzqtJM?t=867 [How to simulate a Starship launch!]
- hikerclimb 6y agoNice hopefully ever mission ever to space fails from the us
- chasd00 6y agoman, SN10 was a little close. Maybe they didn't have anywhere else to put it?
- shmerl 6y agoThey should make a new version of "How Not to Land an Orbital Rocket Booster" for Starship :)
- new_realist 6y agoFeynman 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 those. With this knowledge larger component parts (such as bearings) are designed and tested individually. As deficiencies and design errors are noted they are corrected and verified with further testing. Since one tests only parts at a time these tests and modifications are not overly expensive. Finally one works up to the final design of the entire engine, to the necessary specifications. There is a good chance, by this time that the engine will generally succeed, or that any failures are easily isolated and analyzed because the failure modes, limitations of materials, etc., are so well understood. There is a very good chance that the modifications to the engine to get around the final difficulties are not very hard to make, for most of the serious problems have already been discovered and dealt with in the earlier, less expensive, stages of the process. The Space Shuttle Main Engine was handled in a different manner, top down, we might say. The engine was designed and put together all at once with relatively little detailed preliminary study of the material and components. Then when troubles are found in the bearings, turbine blades, coolant pipes, etc., it is more expensive and difficult to discover the causes and make changes. For example, cracks have been found in the turbine blades of the high pressure oxygen turbopump. Are they caused by flaws in the material, the effect of the oxygen atmosphere on the properties of the material, the thermal stresses of startup or shutdown, the vibration and stresses of steady running, or mainly at some resonance at certain speeds, etc.? How long can we run from crack initiation to crack failure, and how does this depend on power level? Using the completed engine as a test bed to resolve such questions is extremely expensive. One does not wish to lose an entire engine in order to find out where and how failure occurs. Yet, an accurate knowledge of this information is essential to acquire a confidence in the engine reliability in use. Without detailed understanding, confidence can not be attained. A further disadvantage of the top-down method is that, if an understanding of a fault is obtained, a simple fix, such as a new shape for the turbine housing, may be impossible to implement without a redesign of the entire engine. The Space Shuttle Main Engine is a very remarkable machine. It has a greater ratio of thrust to weight than any previous engine. It is built at the edge of, or outside of, previous engineering experience. Therefore, as expected, many different kinds of flaws and difficulties have turned up. Because, unfortunately, it was built in the top-down manner, they are difficult to find and fix. The design aim of a lifetime of 55 missions equivalent firings (27,000 seconds of operation, either in a mission of 500 seconds, or on a test stand) has not been obtained. The engine now requires very frequent maintenance and replacement of important parts, such as turbopumps, bearings, sheet metal housings, etc. The high-pressure fuel turbopump had to be replaced every three or four mission equivalents (although that may have been fixed, now) and the high pressure oxygen turbopump every five or six. This is at most ten percent of the original specification. But our main concern here is the determination of reliability.
- smattiso 6y agoIs 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?
- andrewflnr 6y agoI 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.
- deleted 6y ago[deleted]
- avmich 6y ago> Is this a viable landing strategy in the long run? I prefer Dream Chaser's approach, but Elon Musk has his own ideas. Together with SpaceX team. Of course to fly to the Moon there are no such options.
- elihu 6y agoIt looks like both of these particular failures are engine-related, rather than air turbulence. (SN8: lost fuel pressure, SN9: failed to start one engine for unknown reasons.) These are engineering problems that probably have relatively straightforward solutions. It is a fair point though, that landing in less-than-ideal weather conditions should perhaps be thoroughly tested. Launches generally can be done when conditions are optimal, but it might not always be possible to defer a re-entry until weather improves. Ideally the lander would have real-time high-resolution air velocity data in the vicinity of the landing pad and would adjust its maneuvers to compensate. I wonder what SpaceX's current tolerances are for wind for Falcon 9 landings? I assume anything more than a light breeze and they put it off for another day, but maybe those rockets are heavy enough that the wind doesn't knock them around as much as one would expect. (Droneship landings are especially difficult with wind plus a rocking boat.)
- bemmu 6y agoHere's a better view of the explosion, along with reactions from Everyday Astronaut: https://www.youtube.com/watch?t=16259&v=l4-PwxnJimg https://www.youtube.com/watch?t=16259&v=l4-PwxnJimg
- consumer451 6y agoHere is my favorite footage so far, by Cosmic Perspective: https://www.youtube.com/watch?v=Ep8XJanoFgw 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.
- yborg 6y agoI love that small pressurized tank flying around after the RUD like it's trying to find the rest of the booster...
- WalterBright 6y agoThe sheets of stainless steel appear to have separated at the joints. This says the sheets are stronger than the joints, meaning they're overweight :-)
- laverya 6y agoI was thinking something similar myself (more on weld quality, "welds should be as strong as the rest of the material"), but then I realized that this doesn't matter, and having an unoptimized test vehicle a week earlier is always going to be the better option for SpaceX. 1. Is it light enough to fly? 2. Is it strong enough to not cause a failure? #shipit
- ew6082 6y agoA static weld is usually stronger than the base metal under static conditions (i.e. not undergoing dynamic shock loading). Welds are created at 3000 degrees C with 50-100C metal right next to it. By the time a weld cools there are always captive stresses, meaning during a failure the weld is the most brittle part. This can be alleviated with pre and post weld heat treatment, but there are always stresses built into a weld.
- iruoy 6y agoThey're experimenting with 3mm steel instead of 4mm steel. A test tank they've built already passed an initial pressure test on 26 Jan. One Starship requires 15 rings, a nosecone, a bottom and tanks. If they would all move from 4mm to 3mm then that would save a lot of weight. About 7-10 tonnes according to [1]. [1]: https://forum.nasaspaceflight.com/index.php?topic=52701.160 https://forum.nasaspaceflight.com/index.php?topic=52701.160
- nickik 6y agoI 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.
- Triv888 6y agoIt almost look like they didnt account for the extra weight or size of the rocket.
- modeless 6y agoI don't see how this could ever be as reliable as an airliner for passenger service as SpaceX has been talking about. An airliner can land safely with no engines and even no landing gear if necessary (and it sometimes is).
- Retric 6y agoIt’s total safety that’s important not individual aspects of safety. Clearly there are many disadvantages, but when comparing it to 15 hour flights there are several advantages. For example shorter flight times mean fewer chances for in flight human errors. Another is in flight medical emergencies can be more quickly reach a hospital. A few aircraft have been shot down which is again much less likely, etc etc. Initially it’s going to be risky, but give it say 50 years and it might actually end up being the safest option for ultra long distance travel.
- modeless 6y agoOne aspect can ruin the total safety. It can't be more safe than the least safe part of the trip. Sure, maybe in 50 years we'll figure out something better. But SpaceX is talking about flying long haul Earth to Earth routes with Starship, not a hypothetical future craft.
- Retric 6y agoA 747 built 1970 is very different than a 747 built in 2020. Barring PR issues etc, SpaceX could be using an ever improving version of Starship for a very long time.