totm nov 2023 SpaceX Discussion Thread

[Exoscientist]

 The SLS has public reliability estimates for each of its components. For the Merlins engines on the Falcon 9's we can estimate it as better than 99.9% based on the over 100 successful launches and 10 Merlins on each rocket. 

 But for the Raptor engine no such estimate has been publicly provided. Based on the number of engine failures or explosions on actual test flights, for the Starship during landing tests or the SuperHeavy/Starship orbital test launches, we can estimate it as quite low.

SpaceX should withdraw its application for the Starship as an Artemis lunar lander, Page 2: The Raptor is an unreliable engine.
https://exoscientist.blogspot.com/2023/12/spacex-should-withdraw-its-application.html

  Bob Clark

[tater]

16 minutes ago, Exoscientist said:

SpaceX should withdraw its application for the Starship as an Artemis lunar lander, Page 2: The Raptor is an unreliable engine.

The plan b lander has an engine that has never flown at all, launched by a rocket that has never launched at all, with engines that have never flown at all.

Just stop.

 

[Exoscientist]

On 12/27/2023 at 12:20 PM, Exoscientist said:

I’ve heard from someone who lives near the Starbase site that’s he’s heard scuttlebutt that SpaceX won’t be testing the Raptor at full thrust anymore. Anyone else hear that?

  Robert Clark

I should use his phrasing:

What I hear from the ground testing at the McGregor site (6 miles from my front porch) is no more Raptor starts at full power. I suspect they may have learned the hard way not to do that.

It’s possible he meant judging by the sound they are not doing full power testing. 

  Robert Clark

[Royalswissarmyknife]

42 minutes ago, Exoscientist said:

But for the Raptor engine no such estimate has been publicly provided. Based on the number of engine failures or explosions on actual test flights, for the Starship during landing tests or the SuperHeavy/Starship orbital test launches, we can estimate it as quite low.

Almost like it's an engine still under development.

I read your blog post (probably the worst mistake I have made in my life) and you use old hop test prototypes using Raptor V1 as evidence?

The full duration thing is hilarious too. They test the raptors at full duration at McGregor. Not at Boca Chica while on a ship.

Spoiler

Can someone please tell me how to block people?

 

Edited December 28, 2023 by Royalswissarmyknife

[Codraroll]

42 minutes ago, Royalswissarmyknife said:

  Hide contents

Can someone please tell me how to block people?

Click your profile pic in the top right. The menu for "ignored users" should be  in the dropdown menu.

 

[tater]

1 hour ago, Exoscientist said:

I should use his phrasing:

What I hear from the ground testing at the McGregor site (6 miles from my front porch) is no more Raptor starts at full power. I suspect they may have learned the hard way not to do that.

It’s possible he meant judging by the sound they are not doing full power testing. 

  Robert Clark

Which means he does not live near Starbase at all. McGreggor is ~450 miles from Starbase.

1 hour ago, Exoscientist said:

I’ve heard from someone who lives near the Starbase site that’s he’s heard scuttlebutt that SpaceX won’t be testing the Raptor at full thrust anymore. Anyone else hear that?

 

[tater]

 

[tater]

And Starlink in a couple hours (also from FL).

[tater]

 

 

[tater]

2 min

[Hotel26]

4 hours ago, Codraroll said:

Click your profile pic in the top right. The menu for "ignored users" should be  in the dropdown menu.

Normally, I'd stay out of any conversation about "blocking people" on this forum since we should all be able to just get along...

Just hover over the name tag of the offender in the top-left-hand corner of the offender's post found just above the offender's avatar and linger a moment or two until the menu with "Ignore [offender]" comes up.

@Royalswissarmyknife I reckon you were just being rhetorical

Edited December 29, 2023 by Hotel26

[tater]

Liftoff, MECO, sep, SES-1

Fairing... shaping up as another routine flight to space

Sad they have no idea what they are doing in every other spaceflight regime. Or something.

Entry burn

Landing

SECO

 

Edited December 29, 2023 by tater

[NFUN]

7 hours ago, Exoscientist said:

 The SLS has public reliability estimates for each of its components. For the Merlins engines on the Falcon 9's we can estimate it as better than 99.9% based on the over 100 successful launches and 10 Merlins on each rocket. 

 But for the Raptor engine no such estimate has been publicly provided. Based on the number of engine failures or explosions on actual test flights, for the Starship during landing tests or the SuperHeavy/Starship orbital test launches, we can estimate it as quite low.

SpaceX should withdraw its application for the Starship as an Artemis lunar lander, Page 2: The Raptor is an unreliable engine.
https://exoscientist.blogspot.com/2023/12/spacex-should-withdraw-its-application.html

  Bob Clark

At the risk of getting modded, can you please stop talking about the Raptor and its reliability all of the time?

[tater]

 

[tater]

 

[tater]

The ship is frosty right now. Maybe 2 static fires?

About the great image posted above:

 

[Exoscientist]

16 hours ago, Royalswissarmyknife said:

Almost like it's an engine still under development.

I read your blog post (probably the worst mistake I have made in my life) and you use old hop test prototypes using Raptor V1 as evidence?

The full duration thing is hilarious too. They test the raptors at full duration at McGregor. Not at Boca Chica while on a ship.

  Reveal hidden contents

Can someone please tell me how to block people?

 

 

 Engines on the booster and on the Starship both exploded on IFT-2:

https://twitter.com/rgregoryclark/status/1729867002226081845

The Raptor has been in development since 2016. That it is still exploding in flight suggests it is not a reliable engine.

  Robert Clark

Edited December 29, 2023 by Exoscientist

[tater]

10 minutes ago, Exoscientist said:

 Engines on the booster and on the Starship both exploded on IFT-2:

Only the ship is relevant. The booster was likely due to the flip and props not even making it into already running turbopumps (Bad Mojo™). Failure after sep is not an engine problem until demonstrated an engine problem (starvation seems far more likely) and speaks nothing at all to reliability in that case. Note it's also a test impossible to do on a stand.

The ship failure is more interesting, but we have little data to go by. The idea that it was a plumbing failure due to heating in the ship engine compartment is pretty plausible, the way to test it will be to fly the ship again. I have to assume they have updated some of their simulations as well with whatever telemetry they got.

 

Edited December 29, 2023 by tater

[Exoscientist]

9 hours ago, NFUN said:

At the risk of getting modded, can you please stop talking about the Raptor and its reliability all of the time?

 I’m making a serious charge here. I’m suggesting SpaceX knows the Raptor is unreliable and is obscuring that fact both from the NASA and the American public. For an engine that is supposed to power a craft carrying astronauts and for which billions in American tax dollars have been earmarked it should be essential that it’s reliability be established.

Note that the components of the SLS each have publicly available reliability estimates at 99.9%

 The Raptor has been in development since 2016 and no such reliability estimates are offered for it for an engine intended to power craft carrying astronauts and even civilian passengers.

  Robert Clark

[tater]

Also, what difference does it make? SpaceX will fly/iterate until they sort it out, or they will never sort it out (seems unlikely). It's not like it's costing the taxpayers anything, LSS only gets $ for milestones.

13 minutes ago, Exoscientist said:

 I’m making a serious charge here. I’m suggesting SpaceX knows the Raptor is unreliable and is obscuring that fact both from the NASA and the American public. For an engine that is supposed to power a craft carrying astronauts and for which billions in American tax dollars have been earmarked it should be essential that it’s reliability be established.

It's a fixed price contract, paid upon approval of milestones (and safety) by NASA.

It's not the same as SLS at all in that regard, where the taxpayers are on the hook for more than the total cost of 2 landings on the Moon for the contract SpaceX has—every single year, regardless of SLS flying or not.

If it doesn't work, SpaceX doesn't get paid.

Your claim is predicated on the notion that SpaceX is not sharing data with NASA, BTW. I'm confident NASA has more data than we have watching livestreams on NSF.

NASA has a lot of involvement per the HLS contract:

https://www.nasa.gov/wp-content/uploads/2023/01/80MSFC20C0034-P00010_Att_J-01_SOW_RIF_TAGGED.pdf

Edited December 29, 2023 by tater

[tater]

Static fire ship. subset of engines.

 

[Ultimate Steve]

Last I checked we didn't have a clue why stage 2 exploded, the only real things we know is that:

1. There was probably a LOX leak towards the end

2. The FTS was activated

While there isn't much to suggest it was engine related, there isn't much to suggest it wasn't engine related. But it is worth noting that the upper stage engines were (I think, double check me on this) an older model that still had hydraulic TVC and aren't really indicative of the current state of Raptor.

 

Stage 1, we still don't have any official word, but it is looking like it had something to do with extreme fuel slosh during separation casing either damage to the plumbing via fluid hammer or propellant starvation, which is a problem with the flight profile and/or fuel feed system and not with Raptor itself.

This is only as accurate as the public telemetry and this guy's CFD skills, but someone did run a simulation:

That does not look like it is healthy for the vehicle. A bit alarming that internal simulations did not predict this, or maybe a bad assumption was made here, but preventing this should be a relatively straightforward change in the stage separation profile once the causes behind their improper assessments are made clear.

It is also possible that the engine failures could be due to the effects of spinning up the turbopumps while in a weird angular rate and acceleration state, in which case the solution is to perform the flip slower and sacrifice a small amount of payload. It could have also been a large cascading failure, in which case Raptor, the failure detection software, and the engine shielding are to blame, but none of the IFT-1 failures caused obvious cascades (if I remember right). It could also be a lot of failures of Raptor due to the dynamic environment they hadn't been able to test at and analyzed incorrectly. This would indeed be a large scale failure of Raptor.

 

Yes, it is quite possible that there is a huge conspiracy to cover up the fact that Raptor is unreliable. That is, however, far from the first thing that crosses my mind with the available evidence. Why would there be a conspiracy when we can look at the public test flights and see with our own eyes that Raptor has a ways to go? Every aborted static fire, every failed ignition, every sound a Raptor makes on a test stand, and every single in flight failure are all the subject of public scrutiny. There is no other rocket engine development program that is livestreamed 24/7 by several different YouTube channels. We probably know more about Raptor reliability than any other privately developed and operated engine besides Merlin.

The part that seems to be missed by many is that Raptor is also obviously improving. A couple years ago, it was a struggle to light three engines at the same time on the ground, taking several attempts. Now they can ignite all 33 on the booster and all 6 on the ship first try, and have them work for minutes on end.

There being no detailed public safety estimates for Raptor like there are for SLS is likely down to the different levels of oversight the programs have been given. Such analyses have not been mandated, so they would not be run.

Such analyses would not have much point to them, as two Raptors produced six months apart are very different, and by the time a comprehensive safety report was completed, it would already be very out of date.

 

The fact that the engines might still be iffy two years before the proposed lunar landing date is less down to the engines themselves and more down to the government trying to start a lunar landing program less than five years before the proposed lunar landing date, which was never going to work with any of the bids, and the only affordable bid being the most ambitious launch vehicle project ever, a project that was very open about not adhering to traditional development practices.

Edited December 29, 2023 by Ultimate Steve

[Cuky]

53 minutes ago, Exoscientist said:

 The Raptor has been in development since 2016 and no such reliability estimates are offered for it for an engine intended to power craft carrying astronauts and even civilian passengers.

You are comparing still in development rocket engine with the one that has been in developing and flying (not competely without a glitch) since 1960s.

Merlin engines as well didn't work flawlessly but soacex improved on design until it got to the point that they are now where they more often scrub the launch or loose a booster due to bad weather for recovery than because of. technical issues.

I guess this SpaceX program has the same opposition as it was for when they were choosen for crew transport to ISS... it is best left to do for big government contractors because there is not place for a private company to develop the tools and know how. I think most still can't wrap their heads around someone willing to spend money building stuff and testing until failure i stead of running simulations for years without any tangible hardware to be seen. And that is then more fueled by smears against Elon that mainstream media is pushing around

[Terwin]

39 minutes ago, Exoscientist said:

 I’m making a serious charge here. I’m suggesting SpaceX knows the Raptor is unreliable and is obscuring that fact both from the NASA and the American public. For an engine that is supposed to power a craft carrying astronauts and for which billions in American tax dollars have been earmarked it should be essential that it’s reliability be established.

39 minutes ago, Exoscientist said:

 The Raptor has been in development since 2016 and no such reliability estimates are offered for it for an engine intended to power craft carrying astronauts and even civilian passengers.

  Robert Clark

Unless and until SpaceX takes money then fails to deliver on a Starship launch due to engine problems(this would be a commercial payload, as HLS only pays after a milestone is reached) Raptor has not failed.

Raptor is still in development and under the mantra of 'move fast and break things'.

Failures are *EXPECTED* and if they do not fail often enough, then they will take greater risks so that they do.

The two (probably) independent failures on IFT2 is likely a *better* outcome for SpaceX  than a nominal flight on a rocket with hidden problems, because they learned more and now have a better understanding of how to make the rocket better.

The earlier you find a problem, the less expensive it is to fix, and SpaceX just found 2 problems(probably) for the cost of 1 in their second launch attempt.

Falcon 1 failed its first 3 attempts (and those were clear failures because they had paying customers onboard), and now the falcon 9 delivers more payload to orbit than all other rockets combined, and the rocket is more likely to be destroyed in transit than during a flight or landing attempt(unless deliberately expended)

[Exoscientist]

37 minutes ago, tater said:

Static fire ship. subset of engines.

 

 

 SpaceX still not doing full thrust, full flight duration static fires for either stage.

  Robert Clark