totm nov 2023 SpaceX Discussion Thread

[tater]

 

[Admiral Fluffy]

You can see what i think is booster 4 on the google maps street view.

https://www.google.com/maps/@25.9855254,-97.1861413,3a,75y,295.54h,99.82t/data=!3m6!1e1!3m4!1s162yHYVm2UDWMfPHyI4mEw!2e0!7i16384!8i8192

[tater]

 

And they rolled it back in, lol

[RCgothic]

 

 

[Beccab]

 

 

 

 

[Beccab]

 

[RCgothic]

Annoying but not unexpected.

"This is the fault of all those letters people wrote!"

That excuse only worked once. Consultation period is closed. It's not an excuse for month on month slips.

Also:

"Don't worry, SpaceX aren't ready anyway."

Putting on a rush is expensive. There's no point rushing if the end date isn't secure. But no doubt they could have made ready with a solid end date! 20/4 was basically ready months ago. 21/5 also could be in launch flow right now . 24/7 are ready for proof testing. Mechazilla is ready.

Edited March 25, 2022 by RCgothic

[darthgently]

42 minutes ago, RCgothic said:

Annoying but not unexpected.

"This is the fault of all those letters people wrote!"

That excuse only worked once. Consultation period is closed. It's not an excuse for month on month slips.

Also:

"Don't worry, SpaceX aren't ready anyway."

Putting on a rush is expensive. But no doubt they could have made ready with a solid end date! 20/4 was basically ready months ago. 21/5 also could be in launch flow right now . Mechazilla is ready.

My gut still thinks that some bureaucracy politics are a factor; not sure how big.  The big flag was when all EV manufacturers but Tesla were invited to DC for a meet-up.  But who knows?

[RCgothic]

I'm not yet willing to ascribe to malice that which incompetence adequately explains.

Edited March 25, 2022 by RCgothic

[Ultimate Steve]

 

 

In other areas of the internet I frequent, the reaction to this has been overwhelmingly negative. Normalization of deviance is part of what lead to the Challenger disaster. They have stopped short of saying that the entire system should be redesigned, so far at least, though.

 

Thoughts?

 

[Beccab]

4 hours ago, Ultimate Steve said:

 

 

In other areas of the internet I frequent, the reaction to this has been overwhelmingly negative. Normalization of deviance is part of what lead to the Challenger disaster. They have stopped short of saying that the entire system should be redesigned, so far at least, though.

 

Thoughts?

 

So far, I don't see the problem - the fourth chute has always opened, only a little later; if it did not open, then *that* would be a problem that needs fixing, but the crew wouldn't be hurt by landing that way either. It's not like an SRB's o-rings opening and being closed by the pressure right before a disaster happens, cause nothing happens if this fourth chute ends up not opening

[Beccab]

 

[RCgothic]

Psyche will be a 2x RTLS mission.

 

 

[Beccab]

12 minutes ago, RCgothic said:

Psyche will be a 2x RTLS mission.

 

 

Dual RTLS and expended core,now that's a weird configuration 

[mikegarrison]

9 hours ago, Ultimate Steve said:

In other areas of the internet I frequent, the reaction to this has been overwhelmingly negative. Normalization of deviance is part of what lead to the Challenger disaster. They have stopped short of saying that the entire system should be redesigned, so far at least, though.

Normalization of deviance is a major concern, yes, but non-simultaneous  filling of a multi-chute parachute system is a known phenomenon that has been investigated for a long time now. It's not like this is some unknown issue.

It is a problem if you say "well, it's OK if one chute doesn't fill because we have redundancy", because if one chute doesn't fill then actually you don't have redundancy anymore. But that's not exactly what is happening here, is it? All four chutes fill eventually.

4 hours ago, Beccab said:

So far, I don't see the problem - the fourth chute has always opened, only a little later; if it did not open, then *that* would be a problem that needs fixing, but the crew wouldn't be hurt by landing that way either. It's not like an SRB's o-rings opening and being closed by the pressure right before a disaster happens, cause nothing happens if this fourth chute ends up not opening

No, that's a pretty dismissive attitude. That really would be normalization of deviance.

Something *does* happen if that fourth chute fails to fill: you lose your safety margin. Anything can happen that would collapse or cut one of the chutes that did fill, and then you would have only two filled chutes.

Edited March 26, 2022 by mikegarrison

[Beccab]

25 minutes ago, mikegarrison said:

Something *does* happen if that fourth chute fails to fill: you lose your safety margin. Anything can happen that would collapse or cut one of the chutes that did fill, and then you would have only two filled chutes.

Absolutely, and as I said, if that happens it *does* require fixing. But it isn't happening

Edited March 26, 2022 by Beccab

[JoeSchmuckatelli]

2 hours ago, mikegarrison said:

Normalization of deviance is a major concern, yes, but non-simultaneous  filling of a multi-chute parachute system is a known phenomenon that has been investigated for a long time now. It's not like this is some unknown issue.

It is a problem if you say "well, it's OK if one chute doesn't fill because we have redundancy", because if one chute doesn't fill then actually you don't have redundancy anymore. But that's not exactly what is happening here, is it? All four chutes fill eventually.

No, that's a pretty dismissive attitude. That really would be normalization of deviance.

Something *does* happen if that fourth chute fails to fill: you lose your safety margin. Anything can happen that would collapse or cut one of the chutes that did fill, and then you would have only two filled chutes.

I remember from my airborne days that a 'cigarette roll' (failed chute deployment) was a particularly bad thing; not only wouldn't the failed chute save your life - it could rob your secondary of lift. (That's why you throw a reserve away from yourself, and don't just pull the cord). We were also trained to 'pull in' (i.e. try to climb) the failed chute.  The cigarette roll was often the result of bad packing and tangled lines. 

Cigarette roll, however, doesn't describe the partial deployment / expansion of the 4th chute on the capsules.  To me it looks like the first 3 to fill do their jobs too well, making the 4th redundant.  IOW - once 3 fill, there is not enough airflow to expand a 4th chute. 

Which suggests that the system needs to be redesigned with 4 lesser capable chutes - thus requiring all 4 to work (the first 3 don't slow down the craft as well as they currently do, allowing the 4th to deploy) - or we accept that 3 is 'good enough' and they can keep the 4th as a reserve. 

[darthgently]

7 hours ago, Beccab said:

So far, I don't see the problem - the fourth chute has always opened, only a little later; if it did not open, then *that* would be a problem that needs fixing, but the crew wouldn't be hurt by landing that way either. It's not like an SRB's o-rings opening and being closed by the pressure right before a disaster happens, cause nothing happens if this fourth chute ends up not opening

Exactly, given that one of the chutes is going to open last and being last, the other chutes will have already slowed the relative airspeed so that last chute will open slower if only for that decreased flow, but also might open slower because the other chutes will be putting more turbulence into the stream I'd think.  If the 3rd chute to open is slower than the 2nd and faster than the 4th then it could support this theory.  I'll have to look closer

[tater]

4 minutes ago, JoeSchmuckatelli said:

Cigarette roll, however, doesn't describe the partial deployment / expansion of the 4th chute on the capsules.  To me it looks like the first 3 to fill do their jobs too well, making the 4th redundant.  IOW - once 3 fill, there is not enough airflow to expand a 4th chute. 

Which suggests that the system needs to be redesigned with 4 lesser capable chutes - thus requiring all 4 to work (the first 3 don't slow down the craft as well as they currently do, allowing the 4th to deploy) - or we accept that 3 is 'good enough' and they can keep the 4th as a reserve. 

This seems like what might well be happening.

 

[sevenperforce]

On 3/19/2022 at 4:06 AM, Beccab said:

This puts the Starlink v1.5 at about 306 kg each

Presumably this gives us new benchmarks and data about Falcon 9 capability.

[CatastrophicFailure]

7 hours ago, Beccab said:

Dual RTLS and expended core,now that's a weird configuration 

Down range recovery is harder on the boosters, and the core has always been iffy to begin with. I wonder if it’s a case of, “better to have reduced stress on two easily recovered boosters and lose one than stretch the envelope and possibly lose/damage all three?”

Either way, I know they won’t, but they absolutely should give us footage from the booster all the way down. 

[sevenperforce]

16 hours ago, Ultimate Steve said:

 

 

In other areas of the internet I frequent, the reaction to this has been overwhelmingly negative. Normalization of deviance is part of what lead to the Challenger disaster. They have stopped short of saying that the entire system should be redesigned, so far at least, though.

 

Thoughts?

The fourth parachute is essentially a backup. It was designed to land optimally with three chutes. So a design which functions with three parachutes and then opens a backup afterward is fine…even if you don’t know which chute will act as the “backup” in advance. 

[sevenperforce]

7 hours ago, Beccab said:

Dual RTLS and expended core,now that's a weird configuration 

Why is that weird? It’s one of the many possible configurations in the Falcon family, each with gradually increasing payload capacity:

1. F9, booster RTLS
2. F9, booster boostback to ASDS
3. F9, booster to ASDS (no boostback)
4. FH, side boosters RTLS, core boostback to ASDS
5. F9, booster expended
6. FH, side boosters RTLS, core to ASDS (no boostback)
7. FH, side boosters RTLS, core expended
8. FH, side boosters boostback to ASDS, core expended
9. FH, side boosters to ASDS (no boostback), core expended
10. FH, all boosters expended

The only thing I’m unsure about is exactly where an expended F9 (#5) fits in this progression. It may be more capable than tri-core-recovery FH without core boostback. But apart from that, each of these configurations has higher capacity than the last, and each of these configurations costs more than the last. So if the desired payload can’t be delivered with configuration #6 but can be delivered with configuration #7, then you pick #7 because there is no need to spend more money on #8.

23 minutes ago, CatastrophicFailure said:

Down range recovery is harder on the boosters, and the core has always been iffy to begin with. I wonder if it’s a case of, “better to have reduced stress on two easily recovered boosters and lose one than stretch the envelope and possibly lose/damage all three?”

Well presumably FH doesn’t have the dV to do it while recovering the core. And presumably Psyche doesn’t need the extra dV that would be gained from ASDS recovery of the side boosters.

[RCgothic]

Point to point starship can do a full half-circumference by using lift to skip off the atmosphere. Normally ballistic suborbital trajectories can't do a full half-circumference.

The earth's circumference is 40000 km.

 

 

Also the OLP has the thrust simulator installed in 33-engine config:

 

 

Edited March 26, 2022 by RCgothic

[mikegarrison]

3 hours ago, sevenperforce said:

The fourth parachute is essentially a backup. It was designed to land optimally with three chutes. So a design which functions with three parachutes and then opens a backup afterward is fine…even if you don’t know which chute will act as the “backup” in advance. 

No, this is a bad take.

It's subtle, but the 4th chute is not a "backup". The system has no backup -- if it fails, you have a fatal event. But there is some redundancy -- only 3 of the 4 chutes need to work. However, filled chutes can fail. The system is not successful until the capsule is all the way down at a safe speed.

This is why I think that if they investigate this and discover that the 4th chute is still opening correctly, just slower, it's OK. But if they find that there is a serious risk of it not opening at all, this is a massive safety issue. Because at that point you no longer have redundancy, and your safety design was based on having redundancy.