SpaceX 2023

[brovane]

Cleared for Friday launch attempt. Launch window opens at 7am CST.

https://www.spacex.com/launches/mission ... p-flight-2

[gtg947h]

And now it's been pushed to (at least) Saturday, they are prepping to de-stack for some reason. (Edit: replacing a grid fin actuator on the booster)

Crazy to think that any other rocket, de-stack would be a Really Big Deal. SS/SH it's "we can be re-stacked tomorrow".

[Kunkmiester]

Watching the live stream on Twitter now.

[gtg947h]

Now that was cool! Successful staging and the ship made it almost to scheduled shutdown. Got a lot closer this time and hopefully didn't wreck the pad in the process ..

[Kunkmiester]

Judging by the cloud at launch the pad is probably fine. Looks like they might want more engines on at separation to give them better control.

[brovane]

The 2nd stage flight termination system activated about 8 seconds before 2nd engine cut-off. Might be because of a off-nominal exhaust plume. Pad looks to have survived in good shape and the Super Heavy had all 33 engines running on lift-off. No concrete tornado this time. The Super Heavy booster got through staging and then did the flip around and then something happened that resulted in the FTS activating.

IMG_1627.jpeg

[Kunkmiester]

Looked to me like the separation kicked it out hard, and it couldn't recover. It struggled for a bit but after they couldn't get more engines started they blew it up.

Apparently starship got blown up too.

[brovane]

Looked to me like the separation kicked it out hard, and it couldn't recover. It struggled for a bit but after they couldn't get more engines started they blew it up.

Apparently starship got blown up too.

The FTS worked really well on the Super Heavy this time. The FAA didn't like that on the first flight test it took about 30 seconds after FTS activation for the booster to come apart.

https://youtu.be/081a5Thjl5g?si=k3dnI4VWqRdhCLss

The trajectory that SpaceX was going for with Starship was to go over the Atlantic and then Africa and land Starship in the water off Hawaii. This required a velocity that was just sub orbital to achieve that flight path. It looks like the upper stage engines start misbehaving late during the burn which would have resulted in the velocity coming up short so the FTS prudently destroyed the vehicle so it would come down in the Atlantic and not over Africa.

[Bernard Woolley]

I’m certainly no rocket scientist, but 33 seems an awful lot of engines. The SLS and the historic Saturn V managed with a smaller number of more powerful engines. Seems like there would be a potential for a lot to go wrong.

[Belushi TD]

I think the engine thing is that they've got a proven engine, and it would take a lot of time/money/engineering (but I repeat myself) to prove and attach a smaller number of stronger engines.

I could be wrong.

Belushi TD

[brovane]

I’m certainly no rocket scientist, but 33 seems an awful lot of engines. The SLS and the historic Saturn V managed with a smaller number of more powerful engines. Seems like there would be a potential for a lot to go wrong.

SLS and the Saturn-V where never designed for a full propulsive landing of the 1st Stage for reuse. You burn off so much mass with the fuel that when you come back to land you need engines that have low enough thrust they can land the 1st stage. So you either need a separate set of engines just for landing or you use many smaller engines. This also let's you have the same type of engines for both 1st and 2nd stages. From a thrust perspective the Raptor isn't a low powered engines, it is 1/2 Million Pounds of thrust which is the same as the thrust of each of the four RS-25 engines on the SLS core.
I heard this same theory about to many engines many years ago with the F9 and it's 9 Merlin engines. The F9 has become a extremely reliable launch vehicle despite the 9 engines. Who would argue the F9 isn't a reliable launch vehicle?

[gtg947h]

Really big engines have (even more) trouble with combustion instability. Raptor is in a "sweet spot" for sizing that works well. And assuming you can keep the failure of one engine from taking out more, a greater number of engines makes for engine-out redundancy.

[Bernard Woolley]

Did say I was no rocket scientist!

I’m also guessing using lots of engines is better than a parachute?

[kdahm]

I think the launch went great. The main objectives of the launch were met easily, some of the stretch objectives were met, and it ended with not one by two Kablooeys. Pity the second one wasn't that visible.

It looked to me as well like the booster simply couldn't get upright after separation. The RCS system was seen to be going like crazy attempting to shift it. SpaceX may need to look at the aerodynamics before the next launch. I'm guessing not more than two months.

The Starship termination was just a bit weird. It was going, seemingly on nominal trajectory, then boom. What may have happened is that the parameters on the flight termination system were tightened a bit too much to satisfy the FAA requirements, and so a slight deviation triggered it. Or it was using more fuel than expected and didn't have the trajectory to get across Africa. The tight parameters of the FTS may have also affected the booster.

As far as the 33 engines, remember that Falcon Heavy has 27 flying in formation. The big difference now is the the computer power to control those engines and to model the dynamic behaviour of them is far in advance of the N1.

[brovane]

I think the launch went great. The main objectives of the launch were met easily, some of the stretch objectives were met, and it ended with not one by two Kablooeys. Pity the second one wasn't that visible.

It looked to me as well like the booster simply couldn't get upright after separation. The RCS system was seen to be going like crazy attempting to shift it. SpaceX may need to look at the aerodynamics before the next launch. I'm guessing not more than two months.

The Starship termination was just a bit weird. It was going, seemingly on nominal trajectory, then boom. What may have happened is that the parameters on the flight termination system were tightened a bit too much to satisfy the FAA requirements, and so a slight deviation triggered it. Or it was using more fuel than expected and didn't have the trajectory to get across Africa. The tight parameters of the FTS may have also affected the booster.

As far as the 33 engines, remember that Falcon Heavy has 27 flying in formation. The big difference now is the the computer power to control those engines and to model the dynamic behaviour of them is far in advance of the N1.

On theory is that the 1st stage flip around by the Booster resulted in greater than expected fuel slosh which then resulted in the engine fuel intakes taking in air instead of fuel which is really bad for rocket engines. Those are really big tanks and I could easily see the fuel sloshing around during that flip maneuver.

[Rocket J Squrriel]

This blog has some data one where the fragments of the 2nd stage might've ended up. There is also a link to video on X that might show a fragment on reentry. According to them the 2nd stage was near engine shut down for its coast period when it went BOOM.

https://sattrackcam.blogspot.com/2023/1 ... nd-up.html

The staging also uses 'hot staging':

“In hot-staging, we throttle down and shut down most of the booster engines, then we light the Starship engines. It's one of the most efficient ways to do stage separation,” he said. “I'd say that's the riskiest part of the flight.”

[JBG]

I learned a new phrase watching this on the news this morning: "Rapid Unscheduled Dismantling"!

Jonathan

[brovane]

Good article by Eric Berger on the 2nd flight of Starship.

https://arstechnica.com/space/2023/11/h ... nts-page=1

[brovane]

8 years ago today, SpaceX successfully landed an orbital class rocket for the first time. SpaceX has now landed Falcon rockets 250 times and counting.

https://twitter.com/SpaceX/status/1737931955306697065

[gtg947h]

The Starship termination was just a bit weird. It was going, seemingly on nominal trajectory, then boom. What may have happened is that the parameters on the flight termination system were tightened a bit too much to satisfy the FAA requirements, and so a slight deviation triggered it. Or it was using more fuel than expected and didn't have the trajectory to get across Africa. The tight parameters of the FTS may have also affected the booster.

From the boss-man...

"Flight 2 actually almost made it to orbit (...) The reason it didn't quite make it to orbit is we vented the liquid oxygen (...) ultimately led to a fire and explosion (...) we wanted to vent the (LOX) because we normally wouldn't have had that (LOX) if we had a payload. Ironically if it had a payload it would have reached orbit"

So it sounds like the decreasing LOX levels folks thought they saw (myself included) was accurate, but it was deliberate rather than a failure. Oops

Apparently the plan for Flight 3 is to actually go straight to orbit (instead of the "just barely suborbital so we know it comes back down" plan for 1 and 2) and then do a deorbit burn off the header tanks. Supposedly the vehicle will be ready in a couple weeks and FAA license expected in February...