Well, better luck tomorrow. I’ll be on a plane from DC to LA, or maybe on layover in Philly, but I might be able to see it on my tablet on the plane.
Well, better luck tomorrow. I’ll be on a plane from DC to LA, or maybe on layover in Philly, but I might be able to see it on my tablet on the plane.
Musk described the issue as a hydraulic pin failing to disengage. I thought they were trying to avoid hydraulics in favor of electro-mechanicals. Too slow, maybe?
WD-40…
I may be the only one who is happy about last night’s scrub. I was at an important meeting with terrible cell phone reception, so I couldn’t even get an update during the countdown. I’ll be watching live if they try again tonight. Over on one of the forums at NASASpaceflight.com (a good site with IMO a poor name), someone pointed out that Texas law prohibits blocking a beach on a holiday weekend including the Friday before unless given permission.
Agreed that NASASpaceflight.com is a name that has aged badly. On the other hand, the site dates from well before there was any US spaceflight except NASA’s so one must make allowances. Changing the domain name now would inflict an instant major epidemic of link rot on the Web to no good purpose.
They could come up with a more appropriate domain name and just redirect the poorly aged one to the new one. This will prevent link rot.
Back in the 1990s, I worked for MCI for a couple years. When founded, MCI was an acronym for Microwave Communications, Inc. When technology advanced to fibre optics, they just changed the name to MCI. It was no longer an acronym. We used to joke that MCI stood for Many Changes Instantly or Money Coming In. I preferred Making Chaos an Institution.
NASA Spaceflight uses the NSF acronym already. They could just do what MCI did and make that their name.
Me too. Traveling. Hey maybe I’ll see you Philly. Likely not.
They made it to orbital velocity with an engine out. Losers ain’t going nowhere… 😉
Watching it now on flight to Indy. Impressive.
The pitch-over after stage separation seemed kind of fast to me, but perhaps that’s how it’s intended. Perhaps the giant downcomer had issues with slosh, water hammer, or other dynamic forces.
I read somewhere recently that a faster flip for boostback was intended. I think keeping five, instead of just three, booster engines running during hot-staging was in service of that goal.
The only partial boostback engine relight followed by a too-early all-engine shutdown was not a good look, though at least some of the engines relit just prior to booster splashdown. That suggests that you are likely right about plumbing dynamics being the problem with the abortive boostback.
Losing an outer-ring booster engine and a ship Rvac on ascent after initial successful starts was also a bit ragged, but we’ve seen equivalent issues before on previous flights and the vehicle compensates well for these.
Definitely some more homework to do before the next test flight, but everything else seemed to go quite well. I’d give this test an overall grade of B+.
The boost back burn itself might be the problem. If Super heavy weighs about 350 tonnes and has 400 tonnes of fuel at stage separation (both guesses by Google AI), it weighs 750 tonnes. If it lit all the engines it would have about 20 million pounds of thrust, so the acceleration would be 12.2 G’s, with a rapid onset, and during a rapid rotation. If anything is going to break loose internally, that’s when it would happen.
AFAIK the outer ring of booster engines are not restart able in flight. This may have been a V3 change though.
I believe the Raptor 3 no longer incorporates igniters of any sort, relying on propellant pressure, in some diesel-ish fashion, to kick off ignition. That would seem to allow any Raptor 3 to be restarted in flight, but might also explain why restarts were both ragged and short-lived on the boostback if propellant dynamics were not within reasonable bounds of nominal.
I did a bit more math, yet still based on some things Google A.I.tossed out, which could always be garbage.
Assuming Super heavy has 400 tonnes of propellant at stage separation, and its empty weight is 350 tonnes.
With a 3.6:1 O/F ratio, it would have 313 tonnes of LOX and 87 tonnes of methane. If the sub-chilled methane density is 460 kg/m^3, then that’s 189 cubic meters.
On Superbooster V2, the methane downcomber was 3 meters in diameter, with a cross sectional area of 7.07 square meters,so 189 cubic meters would be 26.76 meters tall (head), which is 87.8 feet. It lit thirteen V2 engines at boostback, and if it weighed 700 tonnes then it would’ve accelerated at 4.8 G’s. The head pressure at the bottom of the methane downcomber would’ve been 84 psi. Google says the tanks on Superheavy are pressurized to 87 psi.
On V3, if the methane downcomer is 3.7 meters (12 feet) in diameter, like the Falcon 9, then the cross sectional area is 10.75 square meters, and 189 cubic meters of methane would only be 17.6 meters high (57.7 feet). If it managed to light all 33 V3 engines, and weighed 750 tonnes, it would accelerate at 12.1 Gs and the head pressure at the bottom of the enlarged downcomer would be 139 psi. Could that extra pressure cause a problem? I don’t know. I doubt it, because they would have designed for that. But it might compound with some hammer and slosh issues.
In the video of the boostback, the center engine flashes brightly before everything shuts down. If something is mechanically failing with the downcomer, I suppose the center would be the most logical place for the problem to extermally manifest.
Hopefully SpaceX will fill us in fairly soon.
Scott Manley speculates that some of the problem was the booster deflecting in the wrong direction at hot stage. You can clearly see some of the Starship’s exhaust gases impinging on a grid fin that under a different deflection wouldn’t have been there. It did appear to induce excessive roll. In general booster stability didn’t return until it hit dense enough atmosphere for the grid fins to stabilize.
Are they still using autogenus pressurization or is it all liquid nitrogen these days? If the former maybe they should consider keeping more Raptors spinning at hot stage for ullage thanks to the new downcomer?
37 out of 39 engines on the first ever flight of the Raptor 3 is pretty good, considering the teething pains with Raptors v1 and v2, I’d say.
Definitely looking forward to the next flight!
That was my thinking as well. The SpaceX announcers on X said the staging would involve all three vacuum engines. They were also going to use one sea level engine to accelerate the flip maneuver. I’m not sure, but my guess is they also used the thrusters. Perhaps the result was faster than they anticipated. The announcers said they intended to use all 33 engines for the boost back, but only a small number actually lit, and they only remained lit for a short time. I suspect the flip may have caused propellant sloshing in the giant downcomer. If that’s the case, then perhaps the solution is as simple as slowing the flip next time, possibly by delaying the ignition of the sea level engine, not using the thrusters, or actually using counter thrusters. Of couse, I could be completely wrong on what happened.
Just to add, I remember reading about the severe pogo oscillations on Apollo 6. NASA found a solution and implemented it. The next Saturn V flight was Apollo 8, which launched astronauts to orbit the moon. If some form of propellant interruption during the flip maneuver is determined to be the cause, it’s possible SpaceX will press on aggressively on Flight 13.
My flight left Philly just about 2 mins after SS/SH launched and they managed to almost reach Australia and beat me to Indy by about 20mins. As I asked my friend Gary afterwards. When can I buy a ticket?
They done real good! Didn’t see any part of the spacecraft look like it was burning off, very little sparking.
They skipped the orbital relight test, probably because it was one of the vacuum engines that failed and they were probably more interested in how the ship handled reentry. But I am pretty sure they won’t put the ship into an orbit until they are confident in their orbital relight ability.
As it is, their flights have all been suborbital – no matter what happened, the ship would come down in a particular zone. My guess, without any particular insight, is that they will want two succesful tests of relight before they go orbital.
‘You’re only supposed to blow the bloody letters off!’
https://x.com/AJamesMcCarthy/status/2057987981642735627
Any word on the condition of the pad?