sevenperforce

An exoatmospheric Crazy Ivan should have very little structural strain -- aerospace members are usually stronger in tension than they are in compression. Here's a crude gif: Remember that this is a top-down view, not a side view.

I... Excuse me? The flip was planned? They were going to do a supersonic hammer-throw with a building-sized rocket to avoid fitting a normal separation mechanism. The HELL? This is Philip Bono levels of far-out. SpaceX, you have flabbered my gast most thoroughly, and I salute you. I've since received updated information and I've updated the graphic accordingly. It's more like this: Note that all of this is in the yaw axis. So less Pugachev's Cobra, more Crazy Ivan. Except the stack yaws 90° to port before commiting to the Ivan, and the booster then does a 270° Crazy Ivan but releases the Starship a third of the way through.

I don't think so. There's no confirmation that the booster actually fully lost hydraulic power at any point, and latches seem like the sort of thing that would get redundant loops. If I recall, one Falcon 9 was lost because of a hydraulic loss on the grid fin drivers, so they put in a backup hydraulic to make the grid fins dual redundant. The latches probably operate off the same hydraulic system as the grid fins, which makes them independent of the engine hydraulic unit.

The description from those on the inside is that the separation WAS commanded but didn't happen for some reason. The Starship is already supposed to have an abort mode for Superheavy failures. Granted, it might not have been programmed in yet, but trajectory issues alone wouldn't have been a reason not to attempt separation. That's a huge assumption. FTFY. It's not an assumption; it's just one possible theory. Do you really think this would have been the case on all latches on all sides ? Visually there was no seperation happing at all. It may have been that the set of aerodynamic forces and torques and the type of latches involved caused only one of the latches to seize, but it was in a position where it acted like a hinge and thus kept the stack connected: The gray arrow is the direction of travel, and the blue arrows are wind. At the moment of commanded separation (when Starship is pointed straight down in my graphic) the separation latches on the leeward side of the interstage are under slight compression (somewhat balanced by centrifugal force), while the latches on the windward side are under tension only. If they're under too much tension (because of higher than expected drag) then perhaps they wouldn't be able to retract, and so they would remain seized. This could explain the split-second image of Starship after Superheavy FTS but before Starship FTS, when the remains of the Superheavy interstage appear to be dangling from the aft of Starship by a single latch: If this wasn't SpaceX, I would think anyone bringing up this manoveur as being completely nuts I showed the (secondhand) source this image, and he's said it's the right idea but without a complete flip -- going back to the drawing board.

Holy crap. This does not look good. Those pilings are 150 feet deep, but still -- that's absolute devastation.

This article is almost two years old now and has obsolete information. There is no pusher stage separation mechanism. There is, however, a separation mechanism -- latches holding the booster and the starship together. When it's time to separate, those latches open. That article talks about a "small but significant" flick. Apparently it's much more than that: Just before MECO, Superheavy gimbals hard left and places the entire stack into a flat spin, and the spin continues under full gimbal for almost 270 degrees before MECO and separation are commanded simultaneously. Once separation occurs, both vehicles continue to rotate and drift apart. Starship rotates for almost another 90 degrees before igniting its engines and straightening out, while Superheavy does another 270 degrees before starting the boostback. It's a really very aggressive maneuver. My working theory is that due to thrust shortfall, the attempted separation happened lower in the atmosphere than planned, resulting in significant aerodynamic torque on the stack during the flat spin, which in turn placed too much shear force on the latches for them to open properly. Separation and MECO happen simultaneously, but MECO is not commanded until latch release is confirmed, and so in this case latch release never happened and so the booster kept pushing through the flat spin because it didn't know what else to do. The other possibility is that the latches were just fine, but because of the higher drag, the rotation rate never got high enough for the computer to command separation at all.

From the NSF forums: Really fascinating. This is honestly what I initially thought, given that the flip started at the time planned for the separation, and I was sure I could see the engines gimbaling, but I doubted myself after seeing a lot of people arguing that the HPU had gotten fragged and all the Raptors immediately stopped gimbaling. It makes sense, though. There was already a thrust imbalance from engine-outs. If all gimbal authority was instantly lost, it would have instantly spun out of control a la Challenger. Additional commentary: God, what an amazing, beautiful thing it will be when we see that.

It may have been that all of their estimates were slightly off, but they were all off in the wrong direction, and there were some exponential variables that all ended up combining to produce a Bad Day. To take your "erosion unit" numbers, let's suppose that the equation for "erosion units" is (strength units)(time units) x (plume interaction units) x (cascade variable)(time units) x (sound pressure units)(plume interaction units). If combining all these units together gives you 80 erosion units, but it turns out that the actual numbers ended up being ~18% higher than expected on average, then it gives you 600 erosion units. My best guess is that there was some sort of cascade effect. When the first engines started up, tank pressure dropped just slightly faster than expected, and so the staggered start took just slightly longer than planned, and the plume impingement was just slightly more damaging than anticipated, and plume interactions as the second set of engines started was just slightly more violent than expected, and so by the time the third bank started up the debris blowback was already greater than expected, and so on and so forth until the pad was getting absolutely rogered before the last bank of engines had even started up, and so engines were being fragged before it even lifted off. And so it lifted off slower, and then this extended proximity to a much more damaged pad fragged more engines, and so forth.

And then started re-entry while still burning for orbit...

Holy mother of mackerel look at the debris hitting the ocean after it gets off the pad.

Very little of the propellant actually burned up in the explosion. The FTS is designed to "unzip" the tanks and dump them to ambient rather than allowing them to mix and burn. Absolutely amazing.

With the damage to the pad and that end-over-end tumble, this is giving me Ares I vibes to go with the N1 vibes.

You can see the engine-rich leak from the center and then that very very off-nominal plume on the right. Probably in the realm of 3 or 4. With 7 engines out, the T/W ratio was dangerously low. Impressive that it remained controllable though.

I saw it nearly hit the chopstick. I don’t know if that was planned. I'm guessing that debris took out multiple engines as it started to lift off the pad, causing a thrust imbalance, and it took a moment to adjust gimbal enough to bring it back to vertical. EDIT: On second thought, the view from Tim's camera shows an aggressive tilt directly away from the tower, which may have been entirely intentional:

That concrete didn't stand a chance. Seeing discussion that the launch pad environment was similar to pyroclastic flow in a volcanic eruption.

What was it Chuck Yeager used to say -- any landing you can walk away from is a good landing? From Hoppy's perspective, any launch where Hoppy is left still standing is a good launch.

To have come so far and learned so little.... Spoken in jest, of course. We obviously know far more than Korolev did. But it does seem like the same issue.

The concern with metal plates was that the spalling could be worse than with concrete because concrete disintegrates but metal can slough off like the shaped charge in an antitank missile. Clearly nothing could be worse than this, in terms of spalling. The concrete just got deleted out of existence. They may need to go to a super-heavy...uh...ultra-heavy?...steel diverter and just flood the hell out of it. Way, way more water.

That is not norminal. Maybe this whole "we don't need no flame trench" business was ill-advised.

That was on purpose. MECO doesn’t actually shut down all of the engines; it only shuts down the outer ring and some of the internal engines remain firing to initiate the kick flip around. Here, it just kept flipping. Assuming that the goal was to reduce risk of failure to clear the pad, it makes sense that they would shut down engines immediately upon any sign of a problem so as to prevent possible chain losses from one engine to the next. So some of those shut downs could have involved nothing more than a momentary bad sensor reading. Definitely giving some N1 vibes though.

For one brief moment the camera started shaking from the force and wobble back-and-forth and it looks like the rocket was bending at the center. I know they ran the engines at lower throttle than they could have, but it really crept off the pad slowly. I wonder what the damage to the pad looks like and I also wonder whether they are able to see if tiles were lost on lift off.

It’s just so damn big. I know we’ve seen starship execute hops before, but the plume is way clearer and less bright than I anticipated for that many engines.

Yep, I saw that too.

Timely.

Looked like it started with barrel rolls but ended up in a penguin roll.