totm nov 2023 SpaceX Discussion Thread

[JcoolTheShipbuilder]

Just now, Delta dart said:

They cant even use SN7.2 anymore because I'm 90% sure that I saw a piece of SN9 go straight through 7.2.

Yikes

[Brotoro]

Hopefully nothing hit SN10.

[Flying dutchman]

engine fault or low fuel pressure again?

[YNM]

1 hour ago, tater said:

Natural gas and methane are commodity items, routinely stored in tanks sitting outside at ambient temp. I have a propane tank at my house (we're not on the natural gas grid), and it never vents at all that I can tell, sitting in the blazing NM sunlight in July with an ambient temp in the shade that might be >38°C.

There isn't gravity to hold all the remaining liquid together for an interplanetary vehicle. Presumably this would increase the surface area, therefore exacerbating boiloff... Idk if that's an issue or not however.

________

 

WRT the test, did they expect single-engine landing or two-engine landing ? Was that a completely failed ignition for the 2nd engine ?

Also dang the shrapnel looked like it'd go towards SN10.

Edited February 2, 2021 by YNM

[Delta dart]

Engine fault because one worked perfectly and the other one just spat fire.

[CastleKSide]

There def was fire repeatedly spat out of engine no 2, but no thrust

[tater]

Given their landing methodology, clearly Raptor needs to be substantially more reliable.

[Flying dutchman]

i was actually pretty condifent sn9 would stick the landing, what a bummer..

[Delta dart]

Raise a glass to SN9.

[Clamp-o-Tron]

Imagine putting 30-something of those on a booster and expecting it to work with current reliability levels.

 

[tater]

The flip maneuver comes so very late (to minimize props) that there seems to be zero time for redundancy (they have 3 engines, only light 2).

I wonder if they could sacrifice some payload, up the header tank volumes, and then do the flip earlier, and with 3 engines. Then shut down engines as needed?

[CastleKSide]

1 minute ago, tater said:

Given their landing methodology, clearly Raptor needs to be substantially more reliable.

I think its fair to say that its not a traditional engine reliability issue here. Trying relights in the flip means the fuel systems have to be extremely will ironed in the entire vehicle

[tater]

1 minute ago, Delta dart said:

Raise a glass to SN9.

Later this evening

 

[Clamp-o-Tron]

Looking frame-by-frame, there looks to be a tiny bit of debris fly that flies off at T+6:21. Not sure if it is a rogue cloud of GOX, but its release from around the failed Raptor seems to coincide with the failed ignition.

Edited February 2, 2021 by Clamp-o-Tron

[Flying dutchman]

1 minute ago, Delta dart said:

Raise a glass to SN9.

i did

[tater]

Just now, CastleKSide said:

I think its fair to say that its not a traditional engine reliability issue here. Trying relights in the flip means the fuel systems have to be extremely will ironed in the entire vehicle

Fair point, I mean as a complete system in this case.

[sevenperforce]

1 minute ago, tater said:

Given their landing methodology, clearly Raptor needs to be substantially more reliable.

I really only worried about two things: aerodynamic control authority during unpowered descent and the engine plumbing reliability at relight. At least the first seems to be a non-issue.

My best guess is that there’s another propellant flow issue. With the 1-2 relight they do, it almost looks like the torque from the first engine startup might have introduced unexpected slosh in the lines to its companion.

Fluid management is hard. 

[Elthy]

In the NSF stream there were two pieces of debris when the tried to start the engine, seems to be a hardware issue.

[MinimumSky5]

Just now, Clamp-o-Tron said:

Looking frame-by-frame, there looks to be a tiny bit of debris fly that flies off at T+6:21. Not sure if it is a rogue cloud of GOX, but its release from around the failed Raptor seems to coincide with the failed ignition.

I've just gone through the video frame by frame, and it's one of the landing legs.

[Clamp-o-Tron]

The SpaceX stream has 403,000 views on YouTube since it was put up 20 minutes ago. I'm sure that breaks some kind of record.

[tater]

Just now, sevenperforce said:

Fluid management is hard. 

Yeah.

Still, per my other comment, it seems like from a redundancy standpoint it would be better to have, well, more time. It's sad to have a bunch of engines on the bottom, but if 2 particular ones MUST work every time, there is not in fact any redundancy.

1 minute ago, MinimumSky5 said:

I've just gone through the video frame by frame, and it's one of the landing legs.

Which video?

 

[Delta dart]

There is indeed a hole in sn7.2.

[MinimumSky5]

The SpaceX official livestream, this is the best view that I can make out of it.

 

Edited February 2, 2021 by MinimumSky5

[tater]

2 minutes ago, MinimumSky5 said:

The SpaceX official livestream, this is the best view that I can make out of it.

Yeah, 2 legs possibly came off. the first when it was trying to restart, and the second closer to impact.

[paul_c]

8 minutes ago, tater said:

The flip maneuver comes so very late (to minimize props) that there seems to be zero time for redundancy (they have 3 engines, only light 2).

I wonder if they could sacrifice some payload, up the header tank volumes, and then do the flip earlier, and with 3 engines. Then shut down engines as needed?

That's my thought too - why not relight 3 engines at 2/3 throttle? It must be more consistent to throttle them from 2/3 to full; rather than rely 100% on engine relight. 

Or....a tin of this: