totm nov 2023 SpaceX Discussion Thread

[tater]

21 minutes ago, SOXBLOX said:

The whole coast is "South Texas" to a Texan. IDK how others might see it. An equally common division is to call nearly the entire coast the "Gulf Coast", or something similar, but that almost universally includes Corpus Christi.

https://gov.texas.gov/uploads/files/travel-texas/7_Region_South_Texas_Plains_2019.pdf

They have the Gulf Coast stay along the coast, and that inland area is "South Texas Plains" per the State of Texas.

<shrug>

 

 

[Hannu2]

On 6/22/2021 at 2:55 PM, SpaceFace545 said:

what’s gonna happen to superheavy if it misses the tower, like that’s a real possibility. Falcon 9 can at least splash down but superheavy is surrounded with concrete not water.

Answer is pretty obvious. SpaceX's bank account takes severe hit and metal workers get few months prolonged work contract. I think that only thing to do is to plan trajectory and building layout so that crashing rocket causes minimum damage to structures. It is impossible to save a rocket stage.

[Beccab]

Lots of Spacex news today:
- As per NSF, what was known as the mix between BN2 and BN3 and that Musk called Booster 2 has been renamed as Booster 3 (B3) and apparently BN2.1 has become Booster 2 (B2):

Quote

"Booster 2 (including BN3 parts) is now called Booster 3, we've been informed (and informed as in by people high enough for us to go with it despite that month old Elon tweet )."

- B2 (previously BN2.1) is being prepared for dismantling and moving it back to the build site, which means it has survived successfully this series of tests;
-Musk said that the hot gas thrusters are an unnecessary complication for now, and will be removed from B3 before launch:

- Finally, the LOX stack of B3 has been unhooked from the high bay crane, which means that the stacking of the CH4 section could start soon

[RealKerbal3x]

Orbital Launch Mount is getting some cross-beams:

 

[tater]

People say it's moving to the 28th.

[sevenperforce]

3 hours ago, RealKerbal3x said:

Orbital Launch Mount is getting some cross-beams:

It's happening!!

Seriously, though, this is really cool. The column structure is...interesting. I would love to see the maths that went into designing the load paths for that. It looks like these crossbeams handle a compressive load. The changing angle for each of these columns would make them want to buckle inward and so you need a lot of compressive loading capacity in the crossbeams.

If I had to guess I would say that the angle in the lower column serves to eliminate bending or leaning moments that would otherwise decrease stability. If they were perfectly vertical, then the entire platform would be much more prone to leaning or rotating. You could eliminate those with additional stability structures but a big part of this structure being the shape it is must be to reduce the overall footprint so that there's as little as possible for Superheavy's exhaust plume to interact with. 

Each of those columns needs to support about 850 tonnes, plus their own mass and the launch table. 

5 hours ago, Beccab said:

Musk said that the hot gas thrusters are an unnecessary complication for now, and will be removed from B3 before launch:

Actually seeing these hot gas thrusters is just incredible. I don't know why but I've really been anticipating seeing them and they are...cool.

Is that Ben Shapiro or Sheldon Cooper on the central thruster?

I suppose that based on Elon's tweet, cold gas thrusters will be sufficient to perform the flip and provide ullage for Superheavy's boostback burn. 

Curious, though, that there is no prograde nozzle shown. It shouldn't need retrograde authority for separation from Starship because the pusher rod(s) and Starship's own thrusters will handle that, but you'd need prograde for ullage, no?

<thinks for a moment>

Actually, wait -- I've got it, I think. Immediately after separation, these thrusters fire to rotate Superheavy back toward the launch site. Because these thrusters are quite hefty, this causes rotation around the center of mass. Because the center of mass is (at least slightly) above the engine cluster, this causes a centrifugal acceleration at the engine cluster, pulling propellant down toward the engines to provide ullage. The core engines ignite and gimbal to cancel the rotation, which provides all the ullage needed. Obviously no ullage is required for the landing burn since you have the air slowing you down at that point.

Looking more closely at the hot gas thrusters, it appears that the GOX and CH4 lines enter the engine near the top of the chamber, so there probably isn't any regenerative cooling going on. This is fine since they will be used in short bursts. 

I would really like to know whether the hot-gas thrusters are fed from an accumulator COPV (which in turn would be fed from the autogen press lines) or are tapped straight from the tank. I would assume the former. Tapping them straight from the tank ullage would be simpler, but would run the risk of liquid ingestion and would also be a waste of the nice high pressures coming off the autogen lines.

[Ultimate Steve]

10 minutes ago, sevenperforce said:

Is that Ben Shapiro or Sheldon Cooper on the central thruster?

Imo looks closer to that guy from "my disappointment is immeasurable and my day is ruined" but people have also suggested Junk Cortez and Linus from LTT. I don't think there's a dominant consensus yet, we would need more pixels to tell.

[RealKerbal3x]

2 minutes ago, Ultimate Steve said:

Imo looks closer to that guy from "my disappointment is immeasurable and my day is ruined" but people have also suggested Junk Cortez and Linus from LTT. I don't think there's a dominant consensus yet, we would need more pixels to tell.

It might just be a SpaceX worker, and we're seeing the product of some elaborate in-joke.

[Beccab]

BN2.1 (not sure anymore of the new naming) has been lifted

 

[CatastrophicFailure]

3 hours ago, Ultimate Steve said:

Imo looks closer to that guy from "my disappointment is immeasurable and my day is ruined" but people have also suggested Junk Cortez and Linus from LTT. I don't think there's a dominant consensus yet, we would need more pixels to tell.

Am I the only one thinking Frankie Muniz from Malcom in the Middle?

Y'know, cut that thruster is like... in the middle... 

[tater]

 

This suggests BN3 will go to the test stand, and BN4 will be the one that flies?

[RCgothic]

That's sure to set back the orbital launch attempt. Darn. 

[Beccab]

5 minutes ago, RCgothic said:

That's sure to set back the orbital launch attempt. Darn. 

Not really, booster construction has never been a bottleneck and they proved last year they can make a starship in basically three weeks. The only reason boosters are taking more right now is because they wouldn't have any use for it with the OLIT being built, so it's unlikely it would cause any problem

[Beccab]

Moar crossbeamsEdit: Also, OCISLY has entered the panama canal

 

Edited June 25, 2021 by Beccab

[tater]

Wonder if it's superstition, as the last time they launched on Elon's b-day it didn't go well.

[Beccab]

More news on the B3/B4 stuff:
"My current assessment of the situation is that following testing of BN2.1 test tank, whist it did hold pressure, some bulkhead overstress issues were identified. Since BN2 is of a similar design and now merged with BN3 (B3) it is likely that these issues may be inherited in the B3 booster. B3 will be carted off for testing on stand A to verify design and testing. If push comes to shove and B3 survives this testing, it may well be transported back for the remaining fitout for launch. B4 will be in production concurrently as a replacement. B3 may be a test to intended or accidental fail which would corroborate Elon's enigmatic statement that 'Next one will fly to orbit'. It is likely B3 will fail. Orbital launch would be extended another month, so we are looking at October."
by Acadene on reddit, a SpaceX insider

[RealKerbal3x]

52 minutes ago, Beccab said:

More news on the B3/B4 stuff:
"My current assessment of the situation is that following testing of BN2.1 test tank, whist it did hold pressure, some bulkhead overstress issues were identified. Since BN2 is of a similar design and now merged with BN3 (B3) it is likely that these issues may be inherited in the B3 booster. B3 will be carted off for testing on stand A to verify design and testing. If push comes to shove and B3 survives this testing, it may well be transported back for the remaining fitout for launch. B4 will be in production concurrently as a replacement. B3 may be a test to intended or accidental fail which would corroborate Elon's enigmatic statement that 'Next one will fly to orbit'. It is likely B3 will fail. Orbital launch would be extended another month, so we are looking at October."
by Acadene on reddit, a SpaceX insider

Where exactly was this posted? Could you send a link?

[Beccab]

7 minutes ago, RealKerbal3x said:

Where exactly was this posted? Could you send a link?

Was since edited, but it's basically identical to before

[Beccab]

...interesting

[RCgothic]

I really don't see everything being readied by end of July. There's still so much to go.

[Beccab]

14 minutes ago, RCgothic said:

I really don't see everything being readied by end of July. There's still so much to go.

Yeah, the follow up tweets note this:

 

Edited June 25, 2021 by Beccab

[grawl]

3 hours ago, Beccab said:

...interesting

They're only shooting for it. As the saying goes...

[tater]

Gwynne Shotwell conversation.

[tater]

 

[Beccab]

 

Edited June 26, 2021 by Beccab