totm nov 2023 SpaceX Discussion Thread

[Minmus Taster]

18 minutes ago, darthgently said:

 

Confused, has it been pushed to Tuesday or is this just timezone shenaniganery?

[darthgently]

38 minutes ago, Minmus Taster said:

Confused, has it been pushed to Tuesday or is this just timezone shenaniganery?

I think the latter.  TBH I’m a bit bored with the time zone math combined with all the changes and decided to just check in around Sunday and Monday and figure it out when more is settled 

Edited Wednesday at 10:03 PM by darthgently

[darthgently]

I wonder if the shifting NET may be somewhat due to the bomb threat.  Idk  ¯\_(ツ)_/¯

[Vanamonde]

A digression about solar power has been moved here. 

 

[darthgently]

It now appears that the NET for FLT-7 Starship is:

4pm CST Jan 14

with 15th, 16th, and 17th alternate windows at same time

Splash landing in Indian Ocean 42 minutes later

 

[tater]

 

[JoeSchmuckatelli]

Not satisfied with flying rockets, now SX is launching the TOWER?!? 

!8o

Edited Thursday at 05:08 PM by JoeSchmuckatelli

[tater]

Ba dum tiss!

[darthgently]

4 hours ago, JoeSchmuckatelli said:

Not satisfied with flying rockets, now SX is launching the TOWER?!? 

!8o

Should this be in the Dad Joke topic?  Lol

[Exoscientist]

 There appears to be only two possible reasons for this: either the Raptor is not as reliable for reusability as thought or it was damaged during the landing burn.

  Bob Clark

[grawl]

31 minutes ago, Exoscientist said:

There appears to be only two possible reasons for this: either the Raptor is not as reliable for reusability as thought or it was damaged during the landing burn.

Let me add a third one :

- It's a piece of outdated garbage compared to next iterations, better used as recycled scrap material than... Than what actually ?

[Nuke]

or its a test subject and this is the autopsy. fly it again you may lose valuable data.

Edited Thursday at 11:51 PM by Nuke

[tater]

Everything being flown right now is a few versions back from their current state of the art. Nothing is a fixed design for them, they iterate on every vehicle.

[Exoscientist]

2 hours ago, grawl said:

Let me add a third one :

- It's a piece of outdated garbage compared to next iterations, better used as recycled scrap material than... Than what actually ?

 But the one being now flown is essentially the same as flown last time. It would be a great proof of of reusability if the same engines were used.

  Bob Clark

[.50calBMG]

They are, Raptor 314. That said, those are still Raptor 2s, and they are about to be replaced by Raptor 3s, and the new Raptors are arguably a new engine with how much different they are from the 2s, so not really much to gain there. Keep trying though

[Ultimate Steve]

As for the current topic, while it would have been really cool to see an immediate reflight, the expectation was thorough inspection and then either display or dissection. For a historical point of reference, the first and third Falcons to successfully land were not reflown. Of everything to successfully land before Block 4, none flew more than twice and several did not refly. Those that did never turned around faster than 160 days. So the current performance is still Falcon comparable in that regard.

While I would also say that the warped nozzles during re-entry also preclude reflight, I can't, as the engine being reflown on flight 7 was on the outer ring (though I'm not sure if it was one of the warped ones).

But while I'm in the mood, let's do another Raptor reliability tally for the fun of it:

Spoiler

Flight 1

I am straight up going to skip most of this one, partially because it is the oldest and is more or less irrelevant to modern Raptor stats, and secondly, there is a LOT of ambiguity as to how many engines failed, why they failed, and how many (if any) in flight engine restarts were attempted (there is an okay amount of evidence for at least one). There is a shot from NSF convincingly (but blurrily) showing 8 engines out. The icon on the SpaceX stream is inaccurate, as to be expected with a fire in the engine bay severing the connections between the engines and the flight computer. Official SpaceX camera views only ever show a maximum of six engines out, and any engine failures after the tumble would not have been caught. The fire could have also caused the engine failures rather than the engines themselves, and last I checked we don't know for sure if the three engines out at liftoff were pre-emptively disabled or attempted ignition and failed.

It is folly attempting to draw any conclusive numbers from flight 1 with current information unless SpaceX comes out and gives us a timeline showing us every notable engine event and why it happened. The only thing we can for sure say is that at least six engines went out at some point, likely more.

Flight 2

49 attempted engine burns (I will only count burns scheduled to occur before loss of vehicle)

30 engine burns successfully completed

Of the 19 failures:

• 1 boostback burn ignition failure
  • Possibly as a result of the clogged liquid oxygen filter
• 12 boostback burn failures
  • These have been attributed to a clogged liquid oxygen filter starving the engines of liquid oxygen. A few gradually failed, and then one went boom, and then the rest of the vehicle rapidly went boom.
  • I would not call these failures Raptor's fault
• Six second stage engine burns did not reach completion
  • This was caused by a liquid oxygen vent setting stuff on fire, causing communications wires to be severed and the vehicle to self destruct, so 100% not Raptor's fault

All of the failed burns except for 1 have either hard-confirmed or soft-confirmed non Raptor causes, with the only outlier being the one that did not restart for the boostback burn. I believe this is also due to LOX filter clogging as it is in the same area as the engines that started failing almost immediately afterwards.

I don't know what I would call this reliability. 48/49 and 48/48 are reasonable, or if you don't want to count Raptor burns that were cut off early for non Raptor reasons (as Raptor could have failed later in the burn and including partial burns would inflate the statistics), 20/20 is also a reasonable number.

Flight 3

63 engine burns planned (that the vehicle made it to timeline wise)

56 engine burns attempted

36 engine burns successfully completed

Of the 27 engine burn failures:

• 6 engines failed due to a clogged LOX filter during the boostback burn (not Raptor's fault)
• 7 engines "benignly shut down early," completion of the boostback burn was aborted likely due to the earlier failures. This is a simultaneous shutoff of engines that were later commanded to ignite, and is likely not a Raptor issue. This is speculation, but I would guess that the vehicle deemed itself not healthy enough to safely continue with the full boostback and did a kind of "offshore divert" similar to what we saw on flight 6.
• 6 engine ignitions for the landing burn not attempted as those were the 6 that got clogged during the boostback and were deemed to be unhealthy
• 5 Raptor ignition failures during the landing burn. This might also be LOX filter clogging, but is likely something unexpected with Raptor in that high dynamic pressure and g force startup environment. SpaceX says "And utilizing data gathered from Super Heavy’s first ever landing burn attempt, additional hardware and software changes are being implemented to increase startup reliability of the Raptor engines in landing conditions." I am content to call these Raptor failures, though I will note that assuming these failures were related to these conditions specifically, they would not endanger any hypothetical payloads.
• 2 Raptor burns were not completed as the booster slammed into the Ocean or broke up just above the surface before landing burn cutoff (not Raptor failures, though the other 5 Raptor failures caused the situation that caused the burns to be cut short)
• In space engine restart was not attempted/was skipped due to the vehicle losing attitude control (not a Raptor issue)

I would call that 51/56 but other numbers are reasonable.

Flight 4

65 engine burns planned (see note)

63 engine burns successfully completed (see note)

Of the 2 failures:

• One engine failed shortly after liftoff
  • Cause unknown
• One engine did not ignite
  • Cause unknown

Note: The engine indicator was not functioning for Starship's landing burn, but SpaceX confirmed that three Raptors ignited in a post flight update, so we can be reasonably certain that three successful Raptor burns took place.

63/65, could possibly change if failure details are made public.

Flight 5

65 attempted burns

65 successful burns

No failures

Same note from flight 4 applies, engine indicator was not functioning for the landing burn.

65/65

Flight 6

66 attempted burns

66 or 53 successfully completed burns

• I believe that the offshore divert was called out after the completion of the boostback burn, but internally it could have been before, which would mean 13 Raptor burns were cut short for non Raptor reasons.

Thus, 66/66.

 

 

 

If I count from flight 2 onwards, counting partial Raptor burns that were cut short for non Raptor reasons as successful Raptor burns, I would count it as 293/300, but there are a *lot* of more or less valid ways you could count it. That puts the reliability at 97.67%, which is, well, not the greatest. RS-25 is indeed about 99.76%, but the RS-25 is, well, the RS-25. Anything against the RS-25 is going to look unreliable.

And it is worth noting that up to 6 of those 7 failures are correlated to the intense landing burn environment (and I don't think we have detailed information on any of those 7). I point that out not to say that "It's actually 99.66% reliable!" but to point out that the RS-25 has to start up once per flight on the launch pad at 1 G, in one orientation (well, 2 slightly different ones considering the shuttle and the SLS), at one atmosphere, at a time where ignition failures (and there were several) could be aborted.

Meanwhile, Raptor has to start up in the following environments:

• On the launch pad (1g 1atm)
• Maybe arbitrarily throughout ascent (variable g, variable atm) (An emergency inflight engine restart may have happened during flight 1 but this is not certain)
• During hot staging (<1g, <1atm, at a large gimbal angle, and nearly up against a solid wall)
• During boostback (>1g for the later engines, in a near vacuum, with a somewhat sideways acceleration vector, with fuel inlet pressures that might vary a decent amount)
• During landing (Significantly more than 1g, a stupid high dynamic pressure, with a decent amount of atmospheric heating)
• In space (0g, 0atm)
• During ship landing (1g sideways, high gimbal angle, subsequent unique acceleration vector and gimbal profile)

Raptor's job is significantly harder than the RS-25's, and it has to operate in some environments that can really only be tested in flight, so the landing burn failures aren't completely unexpected. There's a bunch of comparisons you can do here, Raptor burns in a typical RS-25 profile, counting only Raptor burns that the payload cares about, but those aren't really valid comparisons IMO so I won't make them.

There's also the "Rolling average" argument which would help offset early developmental failures, but is not especially valid as we don't yet have enough later flights for it to be anything other than "If you ignore the ones where it failed, its reliability is pretty good!"

The only somewhat valid metric coming to my mind is that if we get through the next three flights and liftoff of the fourth flight without any further engine failures (Which I don't think is particularly likely at this point in time), Raptor will beat the RS-25's streak for consecutive successes (which I believe to be 352 flight firings, counting from after the STS-51F failure through Artemis 1).

TLDR: Let it cook.

 

[tater]

Meanwhile, the steamroller continues:

 

[tater]

 

[Exoscientist]

43 minutes ago, Ultimate Steve said:

As for the current topic, while it would have been really cool to see an immediate reflight, the expectation was thorough inspection and then either display or dissection. For a historical point of reference, the first and third Falcons to successfully land were not reflown. Of everything to successfully land before Block 4, none flew more than twice and several did not refly. Those that did never turned around faster than 160 days. So the current performance is still Falcon comparable in that regard.

While I would also say that the warped nozzles during re-entry also preclude reflight, I can't, as the engine being reflown on flight 7 was on the outer ring (though I'm not sure if it was one of the warped ones).

But while I'm in the mood, let's do another Raptor reliability tally for the fun of it:

  Reveal hidden contents

Flight 1

I am straight up going to skip most of this one, partially because it is the oldest and is more or less irrelevant to modern Raptor stats, and secondly, there is a LOT of ambiguity as to how many engines failed, why they failed, and how many (if any) in flight engine restarts were attempted (there is an okay amount of evidence for at least one). There is a shot from NSF convincingly (but blurrily) showing 8 engines out. The icon on the SpaceX stream is inaccurate, as to be expected with a fire in the engine bay severing the connections between the engines and the flight computer. Official SpaceX camera views only ever show a maximum of six engines out, and any engine failures after the tumble would not have been caught. The fire could have also caused the engine failures rather than the engines themselves, and last I checked we don't know for sure if the three engines out at liftoff were pre-emptively disabled or attempted ignition and failed.

It is folly attempting to draw any conclusive numbers from flight 1 with current information unless SpaceX comes out and gives us a timeline showing us every notable engine event and why it happened. The only thing we can for sure say is that at least six engines went out at some point, likely more.

Flight 2

49 attempted engine burns (I will only count burns scheduled to occur before loss of vehicle)

30 engine burns successfully completed

Of the 19 failures:

• 1 boostback burn ignition failure
  • Possibly as a result of the clogged liquid oxygen filter
• 12 boostback burn failures
  • These have been attributed to a clogged liquid oxygen filter starving the engines of liquid oxygen. A few gradually failed, and then one went boom, and then the rest of the vehicle rapidly went boom.
  • I would not call these failures Raptor's fault
• Six second stage engine burns did not reach completion
  • This was caused by a liquid oxygen vent setting stuff on fire, causing communications wires to be severed and the vehicle to self destruct, so 100% not Raptor's fault

All of the failed burns except for 1 have either hard-confirmed or soft-confirmed non Raptor causes, with the only outlier being the one that did not restart for the boostback burn. I believe this is also due to LOX filter clogging as it is in the same area as the engines that started failing almost immediately afterwards.

I don't know what I would call this reliability. 48/49 and 48/48 are reasonable, or if you don't want to count Raptor burns that were cut off early for non Raptor reasons (as Raptor could have failed later in the burn and including partial burns would inflate the statistics), 20/20 is also a reasonable number.

Flight 3

63 engine burns planned (that the vehicle made it to timeline wise)

56 engine burns attempted

36 engine burns successfully completed

Of the 27 engine burn failures:

• 6 engines failed due to a clogged LOX filter during the boostback burn (not Raptor's fault)
• 7 engines "benignly shut down early," completion of the boostback burn was aborted likely due to the earlier failures. This is a simultaneous shutoff of engines that were later commanded to ignite, and is likely not a Raptor issue. This is speculation, but I would guess that the vehicle deemed itself not healthy enough to safely continue with the full boostback and did a kind of "offshore divert" similar to what we saw on flight 6.
• 6 engine ignitions for the landing burn not attempted as those were the 6 that got clogged during the boostback and were deemed to be unhealthy
• 5 Raptor ignition failures during the landing burn. This might also be LOX filter clogging, but is likely something unexpected with Raptor in that high dynamic pressure and g force startup environment. SpaceX says "And utilizing data gathered from Super Heavy’s first ever landing burn attempt, additional hardware and software changes are being implemented to increase startup reliability of the Raptor engines in landing conditions." I am content to call these Raptor failures, though I will note that assuming these failures were related to these conditions specifically, they would not endanger any hypothetical payloads.
• 2 Raptor burns were not completed as the booster slammed into the Ocean or broke up just above the surface before landing burn cutoff (not Raptor failures, though the other 5 Raptor failures caused the situation that caused the burns to be cut short)
• In space engine restart was not attempted/was skipped due to the vehicle losing attitude control (not a Raptor issue)

I would call that 51/56 but other numbers are reasonable.

Flight 4

65 engine burns planned (see note)

63 engine burns successfully completed (see note)

Of the 2 failures:

• One engine failed shortly after liftoff
  • Cause unknown
• One engine did not ignite
  • Cause unknown

Note: The engine indicator was not functioning for Starship's landing burn, but SpaceX confirmed that three Raptors ignited in a post flight update, so we can be reasonably certain that three successful Raptor burns took place.

63/65, could possibly change if failure details are made public.

Flight 5

65 attempted burns

65 successful burns

No failures

Same note from flight 4 applies, engine indicator was not functioning for the landing burn.

65/65

Flight 6

66 attempted burns

66 or 53 successfully completed burns

• I believe that the offshore divert was called out after the completion of the boostback burn, but internally it could have been before, which would mean 13 Raptor burns were cut short for non Raptor reasons.

Thus, 66/66.

 

 

 

If I count from flight 2 onwards, counting partial Raptor burns that were cut short for non Raptor reasons as successful Raptor burns, I would count it as 293/300, but there are a *lot* of more or less valid ways you could count it. That puts the reliability at 97.67%, which is, well, not the greatest. RS-25 is indeed about 99.76%, but the RS-25 is, well, the RS-25. Anything against the RS-25 is going to look unreliable.

And it is worth noting that up to 6 of those 7 failures are correlated to the intense landing burn environment (and I don't think we have detailed information on any of those 7). I point that out not to say that "It's actually 99.66% reliable!" but to point out that the RS-25 has to start up once per flight on the launch pad at 1 G, in one orientation (well, 2 slightly different ones considering the shuttle and the SLS), at one atmosphere, at a time where ignition failures (and there were several) could be aborted.

Meanwhile, Raptor has to start up in the following environments:

• On the launch pad (1g 1atm)
• Maybe arbitrarily throughout ascent (variable g, variable atm) (An emergency inflight engine restart may have happened during flight 1 but this is not certain)
• During hot staging (<1g, <1atm, at a large gimbal angle, and nearly up against a solid wall)
• During boostback (>1g for the later engines, in a near vacuum, with a somewhat sideways acceleration vector, with fuel inlet pressures that might vary a decent amount)
• During landing (Significantly more than 1g, a stupid high dynamic pressure, with a decent amount of atmospheric heating)
• In space (0g, 0atm)
• During ship landing (1g sideways, high gimbal angle, subsequent unique acceleration vector and gimbal profile)

Raptor's job is significantly harder than the RS-25's, and it has to operate in some environments that can really only be tested in flight, so the landing burn failures aren't completely unexpected. There's a bunch of comparisons you can do here, Raptor burns in a typical RS-25 profile, counting only Raptor burns that the payload cares about, but those aren't really valid comparisons IMO so I won't make them.

There's also the "Rolling average" argument which would help offset early developmental failures, but is not especially valid as we don't yet have enough later flights for it to be anything other than "If you ignore the ones where it failed, its reliability is pretty good!"

The only somewhat valid metric coming to my mind is that if we get through the next three flights and liftoff of the fourth flight without any further engine failures (Which I don't think is particularly likely at this point in time), Raptor will beat the RS-25's streak for consecutive successes (which I believe to be 352 flight firings, counting from after the STS-51F failure through Artemis 1).

TLDR: Let it cook.

 

 IF it is scrapped would that include the engines? That would not speak well toward Raptor reusability. 
 

  Bob Clark

[Cuky]

2 hours ago, Exoscientist said:

 IF it is scrapped would that include the engines? That would not speak well toward Raptor reusability. 
 

  Bob Clark

Those Raptors on recovered Booster are already old news, Raptor 3 has already been designed and ia in production. So whatever they do with Raptor 2 engines, wether they melt them to make a molten engine puddle, uae them as Chriatmas tree ornaments or just throw them in the bin, speaks nothing about reusability of the Raptor.

[Shpaget]

14 hours ago, Exoscientist said:

There appears to be only two possible reasons for this: either the Raptor is not as reliable for reusability as thought or it was damaged during the landing burn.

Come on, give that imagination some wings. I'm sure you could think of at least another 5 reasons to dissasemble it that have absolutely nothing to do with reliability of Raptors.

Your needle is so stuck in that groove that it will cut that vinyl all the way through.

[tater]

Spoiler

 

[tater]

[darthgently]

12 hours ago, Exoscientist said:

 IF it is scrapped would that include the engines? That would not speak well toward Raptor reusability. 

Looks like you found your favorite squeaky toy again

[tater]