zolotiyeruki

1) You don't know that a Raptor failed on the boostback. All we know is that it didn't start. We have zero reason to believe that there's something wrong with that particular Raptor. In fact, since it fired up just fine for the landing burn, we have evidence that the Raptor worked just fine, and the failure-to-relight during boostback was due to something else. 2) You don't know that a Raptor failed catastrophically on SS. All we know so far is that it RUD'ed, and Musk's tweet about a leak above the false ceiling. Was it inside a Raptor? It's possible, but we have no evidence to support the conclusion you consistently jump to. 3) How is that "standard industry practice" working out these days? How well did it work for SLS? How well did it work for New Glenn? Both of them had second-stage issues, didn't they? All three are at a similar stage of development. BONG started in 2013, similar to Starship's early concept. SLS started in 2011, with a huge head start on propulsion. Starship (effectively re-)started development in 2017, when it was shrunk to a 9m diameter. Money spent so far? SS/SH: ~$7B. New Glenn? I'm not sure. SLS? hehe...$23 Billion and counting. Between the three, it's pretty clear that the "standard industry practice" isn't bringing the benefits you imagine it does.

I'm glad I'm not the only one who noticed flames coming from the hinge at T+07:55. No flames at that same location at +04:45. That's right near the engines. Yup, something blowed up good.

Was any reason given for the no-go on the catch?

In addition to everything else, I'm stoked about the idea of reusing stripped-down starships in space as the foundation for a space station. Picture a bunch of stripped-down (no tiles, ablative, or even flaps) Starships docked to a central hub like wheel spokes. The amount of volume for science or even space tourists would be spectacular.

I just noticed that one of the ten engines in the second ring isn't glowing and flaming like the other nine. The graphics on SpaceX's feed show all 10+3 engines running nominally for the landing burn, but something is different about this one:

Well, hello there, new wallpaper!

The California Coastal Commission has denied Space Force + SpaceX's application for 50 launches next year: https://www.politico.com/news/2024/10/10/california-reject-musk-spacex-00183371 It sounds like the commission didn't like a few things: --sonic booms --disturbance of wildlife --Musk's politics --SpaceX's labor practices

Well, so much for the "b-b-b-b-but they didn't do a full-duration static test fire!" nonsense.

So here's my take on it: Short version: SpaceX have the most to lose here, and I'm inclined to think that they're confident in their fixes to the earlier problems. Given SpaceX's rapid pace of development and iteration, and that regulatory approval seems to consistently stand on the critical path, it makes sense to test as many things as possible with each launch. In other words, if the FAA/EPA/FWS are going to drag their feet for months for every launch, you'd want to maximize the amount of test data you get with each launch. Longer version: A successful chopsticks-catch relies on all the various bits working correctly--engine relight, flaps, engine gimbals, control system, radar altimeter, GPS, etc. And all of that is moot unless the launch, separation, and boostback are nominal. Rather than take an overly-simplified perspective on it ("they haven't had a flawless soft ocean landing yet"), it's important to get into the details. First, you have to define the actual Bad Thing that could happen. Let's call it "damage to the tower." Second, you have to figure out what failures on the booster could cause that. Third, you have to eliminate (or accept the reduced risk from) those failures which have mitigations in place. For example, several of those failures (failed relight, GPS, a few others) are mitigated by having an initial trajectory that sends it offshore. Several others may be mitigated by FTS. Fourth, you look at the ask-yet-unmitigated failure modes. It appears that SpaceX have already proven out most of the systems--the aerodynamics, engine gimbals, control systems and GPS/altimeter stuff is fine, based on the previous launch. The propulsion systems appear to be the last piece (at least for the booster) that haven't had a perfect performance. SpaceX have surely addressed (or attempted to address) the issues that caused the engine fire on the last SuperHeavy, which means that the last known unmitigated failure modes have been addressed. Besides, you could make the argument that the successful water landing proved that the existing mitigations (e.g. throttling the other engines up to compensate) already work. And lastly, you have to evaluate the consequences of a failure. At this point the Bad Things that are left are some sort of failure in the chopsticks, and a fuel leak and fire at the engine end of the booster, with a potential structural failure and spectacular-but-brief fire. SpaceX have to test the chopsticks at some point, and I'd be willing to bet that SpaceX have a solution to the engine fire thing. So yes, they could do one more soft water landing to prove that all the systems work. At that point, however, they'd be chasing unknown unknowns, i.e. now-we're-just-guessing-what-might-go-wrong.

I'm pretty sure the Falcon 9 booster landing burns still start with a trajectory that misses the ASDS, with the landing burn adjusting the trajectory toward the ship. Compared to RTLS, the difference between the two trajectories can be pretty small. I don't recall--how many successful water landings did SpaceX perform before they started attempting to land on the droneships? It seems like it wasn't very many, certainly not a dozen. Just to add to this: if the relight succeeds, not only will the rocket be moving slower, but it will also have a lot less fuel in it when it gets to the chopsticks, in case something *does* go wrong after relight.

Keep in mind that when Superheavy (or Starship, for that matter) are being caught, there's not a whole lot of fuel left for any explosion. Sure, if the arms miss the catch, there'll still be quite a mess to clean up, but we're not talking Russian-ammo-dump levels of kaboom here.

From a quick google search, it appears that orbital velocity at a low Mars orbit is about 3.3km/s, so it might be an option. The trick is with the later aerobrakes, where your orbit spends longer and longer in the atmosphere. At least, that's what I learned in KSP.

There's a heavy implication here that SpaceX owes the public this information about exploding engines and stages, and by not divulging it, they are somehow trying to hide it or deceive the public or the FAA. I'm not terribly concerned about an explosion during a landing catch. After all, SpaceX has more incentive than *anybody* to make sure it's safe. It's their money at stake. As for the public or the environment? Meh, the area is cleared anyway, and the only thing they'd be scattering into the environment is steel, water, and CO2. Perhaps my reading comprehension is failing me, but I'm not seeing anything in the quote that supports the claim that the FAA is protecting SpaceX (or from what).

Also, because the arms are actuated (and not just a rigid structure), the PID control loop for their movement can be tuned to prevent and/or mitigate that oscillation.

I have to wonder how much attention NRO is paying. The size of the optics you could put on a spy satellite that fits inside Starship must surely have some folks salivating.

SpaceX have tried *lots* of things that haven't worked, from various landing legs, to landing burn sequences, to repurposing offshore oil rigs, to carbon fiber for Starship/Superheavy. And yet....somehow, they're still succeeding. If/when an idea doesn't work, they learn what they can, and move to another solution. Besides, are you *sure* that the flip-to-separate was Musk's personal idea? Or that chopsticks were his?

Just to be clear, what "mistake" is SpaceX repeating over and over again? If it's "not doing a full duration burn," then you have to justify why that qualifies as a mistake. If the qualification is "because raptors are unreliable," then you're wrong, because today's raptors are not the same as the ones that failed. Besides, failures are expected in SpaceX's development process, and therefore not doing the type of test burn you think they should do no longer qualifies as a mistake. If by "mistake," you mean "not following industry standard procedure (whatever that is)," then we should all be overjoyed that they're making that "mistake," because it sure seems to be working pretty well for them.

C'mon, man. The whole "SpaceX isn't doing what's standard" concern has already been VERY thoroughly discussed and invalidated in this thread. Many of the constraints of 60 years ago that resulted in "standard practices" no longer exist, and it would be foolish for SpaceX to slavishly follow them. We can see the results of such uncritical thinking in the performance of the SLS program: decades late, billions over budget, and still not 100% working, even though they started with their engines and boosters already designed. Why on earth would SpaceX want to follow such a path? "Standard practice" has morphed from a solution into the problem. I'm reminded of a quote: "Contradictions do not exist. Whenever you think that you are facing a contradiction, check your premises. You will find that one of them is wrong." You have as a premise that "standard practice" is the only (or at the very least overwhelmingly most likely) way to achieve success in the space launch industry. SpaceX is not following standard practice, yet they are wildly successful, while their rivals, who are following standard practice and have decades more experience, are achieving mild success or are floundering. This appears to be a contradiction, and should prompt a reexamination of your premises. In any case, I have a more sincere question: Starship's SL raptors are there to provide sufficient TWR after MECO stage separation, and for landing. At what point during the second-stage burn would the vacuum raptors provide enough TWR that the SL raptors could be shut down? How much efficiency could be gained by doing so?

Six weeks? Dang, they're not sitting around, are they?

I'll bet we can pretty reliably predict Exoscientist's next dozen concern trolling posts. Can I try a few? "SpaceX have got it to space, but they haven't demonstrated they can control SS enough to safely deploy satellites!" "SpaceX is successfully deploying satellites, but they haven't demonstrated SS controllability through reentry!" "SpaceX solved the controllability issue, but they shouldn't be launching until they can reliably demonstrate (with some sort of ground test) that the heat shield tiles won't fall off!" "SpaceX have solved the landing burn relight problem, but they haven't demonstrated sufficient accuracy for the chopsticks!" "SpaceX have captured the booster safely, but they haven't demonstrated reliable Raptor reuse!"

There's an assumption here that a longer boostback burn would/could have caused loss of vehicle. What's your rationale there? Keep in mind that these engines are designed to be reused, so the duration of the burn is pretty irrelevant. The relights for boostback aren't a reasonable analog for relights for a landing burn. They just really aren't comparable. You've typed a lot of words about how SpaceX need to be testing Raptor more before flying them. How do you propose they test the "light the engines while moving backwards at mach 3 at 35,000 feet and decelerating at 5g's" scenario?

I'm a bit skeptical about slosh causing the control issues on Booster during reentry and the landing burn. At that point, there's very little fuel left. Although....I suppose it's possible that even the small amount of sloshing force might be enough to mess up the PID control loops...

My impression is that the exhaust gases from SS don't cause SH to *decelerate*, since the core engines stayed lit during separation. Rather, they reduce SH's acceleration. I also think they've got the flip maneuver itself figured out. But that's a really big tank doing a pretty radical maneuver with little acceleration to settle the fuel except for what the still-burning engines provide, so I imagine there's a lot of slosh going on. Maybe they just need to wait a few moments longer after the flip before relighting the engines for boostback?

It'll be interesting to see how they've addressed the issue of the boostback burn on SH

Rats! I'm here with the family today, and we were hoping to watch it. Oh, well. KSC is a lot of fun anyway