You would think the “dozens of small engines” design would have gone completely out of fashion after the fourth N1 failure in 1972
There’s a degree of “challenge accepted” thinking in SpaceX. It’s worked out well that they have been willing to rethink design orthodoxy, especially if they can answer the objections that caused prior attempts to fail.
So Super Heavy can make 33 engines work pretty well when the N1 couldn’t make 30 work. The early bird may get the worm but it’s the second mouse that gets the cheese.
As to the ground engineering failures, I admit I have a hard time remembering that this entire venture is experimental. I believe they take adequate precautions for human safety. It’s just hard for an operations-oriented engineer like me to watch this without feeling like someone screwed up.
And we should be glad it didn’t, because Falcon Heavy uses 27 engines just fine. What the Soviets could do with 60’s era Soviet technology is not close to what we can do now. Modern computational fluid dynamics, modern materials, sensors, and computer controls make all the difference in the world.
It looked to me like the rocket was pretty nominal (aside from the flameouts) right until the point where it should have separated. It makes me wonder if loss of control was the result of the booster attempting its flip/boost manoever while still attached to Starship? If that was computer sequenced, It may have jist continued the sequence after the failed sepration. But that’s pure speculation, the failure could be due to a million things.
Congrats to SpaceX for getting the entire thing off the ground.
Regarding the separation sequence, how is it supposed to work? They don’t actually spin the entire thing 360 degrees to fling Starship forward, do they? That’d be a helluva ride for any passengers.
Also, considering they had 5-6 engines out, which means a loss of what, about 15% thrust, would it be safe to even try a separation at the speed and altitude they were at? It would seem they’d need to boost a lot longer with that loss of power or else risk Starship coming down far outside the safety ranges. Keeping it in one piece and hitting the destruct button seems a way to better control where the debris fell.
Not that much, but it does indeed “fling” the upper stage by inducing a rotation and releasing the stack. We don’t know all the details, but I doubt it spins by more than about 10 degrees before releasing the clamps. The booster would continue rotating to get into position for the boostback burn; the Starship would presumably stop its rotation via thrust vectoring.
Excellent analysis by Dr. Strangelove. Comments below:
Certainly it did the job of releasing the rocket properly. But a big part of its ‘job’ is to survive multiple launches per day. We’ll have to see how much damage it sustained before we’ll kmow if the design is up to it.
Yeah, this was critically important, and if it hadn’t worked it was a potential show-stopper. They retired a major risk item there. Unless, of course, the engine failures were due to problems with pressurization. But it doesn’t seem like it.
I was going to post that before you did. I never expected that huge rocket to stay in one piece while tumbling through the sky like that. Starship didn’t even break off from Superheavy. ‘Overbuilt’ was the first word that came to mind when I saw that.
Overbuilding makes some sense for a test campaign if you are not sure of all the forces involved. So that’s fine, but it also means they have room for performance improvement if necessary.
This is a big problem. I’m not even sure they can put a proper flame trench under there without dismantling the OLM. It may have been damaged anyway, looking at all the excavation sone by the rocket around the footings. And given how the thing absolutely destroyed the concrete pad, building a flame trench that can handle the energy might be difficult.
This looks like months of work. That maybe explains why Elon said they expect to try again in a few months, not a few days or weeks.
Well, system reliability around the Raptors at least. We don’t know yet if the Raptors themselves failed, or if there were plumbing/pressurization/fuel delivery issues, or whether, as you suggest, they suffered FOD damage.
Absolutely. While I’m sure we all would have loved to see Starship in space, this launch accomplished an awful lot. Autogenous pressurization, lighting all the Raptors, clearing the tower, making it through Max-Q and all the way to stage separation. There were a lot of unknowns up to that point that SpaceX now has great data on, and a lot of potential trouble areas that went through smoothly.
Too bad about the pad, though. That’s going to be a lot of work. I’ll bet there is significant damage to the tank farm and other infrastructure as well.
There were reports I’d read (sorry, don’t recall where as I’ve been reading a bunch of after-press) that some of the tank farm tanks suffered moderate to significant damage.
Eric Berger is probably the best space journalist around, and has been following SpaceX since the beginning. When I see space articles, I always check the author and will definitely read it if it was Eric Berger.
His book ‘Liftoff’ is an excellent telling of the early years of SpaceX right up to Falcon Heavy.
That’s one aspect of the design I haven’t looked at. Is it possible that whatever releases were supposed to separate the stages jammed because of the rotation? Getting clamps to release under the force of a hundreds of tons torquing them might not be easy.
The clamps would have been designed to operate under the intended rotational forces. Of course mistakes might have been made, but that seems a pretty easy thing to ground test and a pretty obvious thing to get right.
From the vid it seems at least plausible that the whole stack was already gyrating more than the nominal release maneuver at the planned time of separation that did not happen. If so, jamming under significant overload would not be surprising. But the stack was already doomed by then anyhow from the gyrations.
Heck, once the stack started gyrating maybe staging was inhibited by design. Better to blow the whole thing as a unit once it’s out of control.
All speculation on my part and darned early in the day.
No real opinion on that as of yet. The launch was hella early for me and I went back to sleep after it was over 
. I was planning on stepping through some of the video footage later to see if I could make more sense of it. I think LSLGuy is on the right track, though, in that it was already under some off-nominal forces and those either jammed up the clamps or just signaled the control systems to not release.
Thanks, trying to wrap my head around how that works.
So… it’d be like having a stick at that point with a very heavy weight on one end. Once you start the rotation and then separate Starship from the booster, Starship travels up in relation to the booster motion from the release point (it’s not picking up additional forward momentum, but upwards/angular from being so heavy and so far forward on what’s basically a long lever at that point) as the booster rotates around its center of mass and momentum carries it straight?
Yeah, I’m sorta separating the “stage zero” functions from the flame diverter ones there. The complicated mechanical bits worked fine. The concrete pad beneath did not. We’ll have to see if the mechanicals suffered any non-debris related damage; i.e., from the booster itself rather than stuff it kicked up.
Agreed that they have months of work ahead. It’s possible they have some redesigns ready to go, and were waiting for this first test before ripping things up–so it may not be entirely a matter of being caught totally flat-footed. But even with that, they just have a lot of work to do.
Something like that. I think of it more like a bola, i.e., two weights connected by a string. Get it spinning and centrifugal force keeps the string taut. Cut the string and the weights separate.
Unlike the bola, the orientation matters here–they need to cancel the rotation of the upper stage, while the booster needs to keep rotating. And they need to not collide, and the upper stage needs to not fire its engines until the booster is positioned to survive. So there will be some complicated gymnastics. But the basic idea is just that centrifugal force separates the two halves.
I suppose if you’ve got a rocket; part of it is supposed to go up, and part of it is supposed to go down, it makes some sense for them to push off of each other in the directions that both want to go.
But where does the energy come from? If you fire thrusters to start the rocket rotating, that gets things lined up correctly, but you’ve spent some energy (propellant) in order to do it. Are there compressed springs (stored energy) holding the two stages together? Even if there were, pushing the upper stage forward, as opposed to pushing it up, both help it achieve orbit. And the time spent with the rocket pointing off its velocity vector is going to increase drag, and bleed off some energy.
I wonder if there’s something else going on. The first stage comes back to the launch site, right? There may be a limit to how far downrange it can travel before it starts to come back. Maybe the off-vector rotation is to help the stages separate more quickly so the first stage can return.
Nope. That’s the traditional way. The Electron rocket uses springs; the Falcon 9 uses pneumatic rods. All sorts of techniques are in use in other systems, including little auxiliary rockets.
The spin is induced by thrust vectoring. Just point the main engines a little to the side and it’ll induce a rotation with very little loss (cos(10°) = 0.985).
No one depends on the stage separation for providing a significant amount of delta-V. It’s on the order of 1 m/s, not the several km/s you need for orbit.
Not just separate, but get into the right orientation. The booster needs to rotate at least 90 degrees in order to perform its boostback burn. The upper stage needs to continue on. So, the upper stage will cancel the induced rotation, but the booster will keep rotating around a significant amount.
So you have an object with a certain velocity vector. If it just separated into two pieces, each would inherit pretty much the same velocity vector as the original, except for any forces imparted during the separation.
But by using some fuel to induce a rotation, when it separates, the two pieces each have a different velocity vector that’s more beneficial to where it wants to go next. The sum of the two vectors will still be the same, though.
Clever, if they can make it work. The faster the rotation, the more difference they have between the two resultant vectors. How much leeway is there in when that separation takes place? In terms of rotation, if they’re 1° early or late can the upper stage still make it to the desired orbit?
Yeah; just before stage separation, the center of mass of the stack is going at, say, 2000 m/s. After separation, one piece is going at 2001 m/s and the other at 1996 m/s (say).
Note that despite being huge, the booster is much lighter than the upper stage at that point, due to being drained of fuel. It weighs 200-300 tons vs. 1300 t for the upper stage. So really, it’s more that the booster gets flung away vs. Starship.
I don’t think it needs to be nearly that precise. As I mentioned, if you’re off by 10 degrees, your effective thrust is still 98.5% of what it should be. And both vehicles should be able to fairly quickly orient themselves to the proper velocity vector, so they won’t spend much time even with that small loss.
A different view of the van that got clobbered:
A veritable field of cameras and antennas. I hope most of those survived. In any case, that looks like the spot that SpaceX carved out for all the streamers covering the event. Not all just from NSF.
Serious question — National Science Foundation, or something else?
(Is this how they incinerate all those rejected grant proposals? Not that I’m bitter or anything…)