sevenperforce

I guess we could compare the descent rate between SN10 and SN5/6 to get a feel for it. I don't think they have any "change your thrust rate by X if the landing legs don't fully deploy" programming. So if it shut down the engine as if the landing legs had deployed, that alone would have dropped it a meter or so (however long the legs are). Yes, I believe they are very close -- probably only 20 cm or so. I remember looking at the closeup on the SpaceX feed and thinking it was odd how close the flaperons seemed to the ground: For any fans of Doctor Who we have this lovely comment by John Insprucker: GERONIMO! We need better legs, now. But it does look like better legs may be in the works. From the DearMoon update: Definitely a different design than before. How large are these exactly? It looks like they have reduced to just four legs, mounted externally. But they are REALLY wide now. Wreckage photos show that the Raptors are at least not completely crumpled.

Well it basically was another rocket engine. The ruptured thrust puck probably acted like a nozzle throat. Do we have word of Elon that there was landing engine underperformance? It looked like a landing leg issue to me.

What are we thinking in terms of actual mechanism? My best guess is that when the legs failed to lock out properly, it came down hard on the engine bells and damaged the thrust puck. The impact probably ruptured the methane downcomer, allowing the remaining liquid methane from the methane header tank to mix with residuals in the main oxygen tank. The oxygen tank was basically a fuel-air bomb. Of course, no big deal...until the fire outside the skirt made its way underneath and up to the thrust puck. And then, kablooey.

All three raptors successfully relit for the flip, so I really don’t think they were having any serious problems. Differences in color on ascent were likely related to mixture ratios and deep throttling. The only “testing” they are doing during flight is figuring out how Raptor performs with the force and pressure transients of actual flight. I understood Elon’s tweet a little differently: there was something a little wrong with the amount of thrust being produced, but it wasn’t wrong enough to be a reason not to fly.

Yeah, you can barely make them out in one of the other feeds. It looked like the engine didn’t quite manage to zero out all velocity. This stuff is tricky. And those legs don’t have much of a crumple zone. Not like Falcon 9.

Yes yes yes yes Elon you crazy son of a gun, you did it! Congratulations starship, congratulations SN10, congratulations SpaceX!

Answer: yes, because of course you do. Tweak that thrust.

Nope, not even close. They had multiple redundant explosive bolt sections because if the clamps didn't sever at precisely the time that the solids ignited, the solids would have ripped the launch pad out of the ground. Those nuts look like two sections but they are really single-piece steel with threads cut into them and they screw around the hold-down bolts. The two holes are drilled out and filled with detcord. Norminally both detcords fire and split the bolt in half at the same time the SRBs ignite, but if one fails to blow the booster will just rip it into pieces safely.

Obviously not quite true but funny nonetheless.

So it did look like the thrust was slightly higher than expected and they are going to go for it anyway. I wonder if they were able to see that the startup transient was tapering off over the thrust limit rather than spiking.

"Out of expected bounds" can be in either direction. If Raptor ignites and throttles up to 80% but it's only producing 70%, that's "out of expected bounds" in the negative direction.

According to John Insprucker they do have time for a recycle. Depends on what we see from Raptor, though.

FINAL VENT YESSSSS LIGHT THAT CANDLE noooooooooooooooooo abort

That's what I assumed. Makes more sense to me. Frost line now visible on the main LOX tank but I can't see it on the header tank yet. I wonder if people have estimated the prop load from the lower frost line.

Does anyone know if the propellant used for the engine chill is still flowing from the GSE, or is the prop load closed out at this point?

THERE'S THE TRI-VENT

Right. I mean what we see visibly, the tri-vent, corresponding to what is happening, the engine chill. One step.

Methane vent! Next step: engine chill and tri-vent. Then...launch.

Propellant loading underway.

He means that a naked FHe can reach LEO with enough propellant to boost 32 tonnes to TLI "assuming the 32t makes its own way to LEO"

Looks like we are back on track.

SuperDraco would actually be massively overpowered.

How am I already out of reactions

No, New Glenn is quite big but it is dwarfed by SLS and Starship.

That sounds untrue. I'm pretty sure SLS is more expensive than Saturn V. Not in constant dollars. I mean, it depends on your math. The total cost of the Apollo program in real dollars was $283 billion. That got us six moon landings for a cost of $47 billion per mission. But of course SLS has not gotten us any moon landings, nor will it for some time. Nor will its first launch be crewed. Apollo had a total of twelve Saturn V launches (thirteen if you count Skylab, which you should because this is about rocket development). And a lot of that $283 billion had more to do with the lunar sorties themselves; development cost and launch vehicle cost came to $125.5 billion (and that includes the cost of the Saturn 1Bs which I'm not counting in the total number of launches). So that's $9.7b per rocket. As of 2020, total project cost has reached $18.6 billion, and we haven't even gotten a single launch out of it. We spend an average of $2.5 billion per year on it regardless of whether it flies, so by the time Artemis 1 launches (next year, realistically) it will have given us one uncrewed launch at a pricetag of $21 billion. By the time Artemis 2 launches in 2023 (if we're lucky) the total project cost will be at $26 billion, which at least lowers the per-launch cost to $13b. If Artemis 3 actually manages to launch at the end of 2024 (which is highly doubtful) then our total per-launch price will finally get down to the same per-launch cost as the Saturn V. And remember that the development costs I quoted for Apollo included all lunar mission development, too. Agreed.