totm nov 2023 SpaceX Discussion Thread

[darthgently]

3 hours ago, Exoscientist said:

I consider it likely the flames seen shooting out the sides of the booster during both tower catches actually arose from Raptor fuel leaks.

Nope.

The jet of flame observed running up the side of the Super Heavy booster moments before it is caught by the launch mount is primarily due to methane (CH4) burnoff. This phenomenon occurs because the booster lands with excess fuel, specifically more methane than can be acceptably dumped into the atmosphere. As the booster approaches the landing phase, it vents fuel to avoid overpressurization, and this methane can ignite, creating the visible flame. This process is part of the landing burn strategy, where the booster slows down using its engines, and the venting and subsequent ignition of excess methane contribute to the visible flame and smoke.

https://www.adastraspace.com/p/spacex-super-heavy-catch

 

[zolotiyeruki]

4 hours ago, Exoscientist said:

  Agree or disagree: it was a mistake for SpaceX to follow the failed N-1 approach to testing Starship. A Raptor failed both on the booster and on the ship, and on the ship one failed catastrophically. How many total test flights needed now just to make orbit with high payload? 10? A dozen? How many total to prove Raptor reuse reliability? 15? How many total to prove orbital refueling? 20? In contrast standard industry practice is to construct a separate, full test stand to do full up, full thrust, full duration testing. Done this way at least Starship could be doing expendable flights already by now, and with paying customers. Even Raptor reuse reliability could have been tested on the full test stand, providing a faster route to Starship reuse.

The comparison of the Superheavy/Starship to the N-1 rocket has been claimed invalid as N-1 rocket engines could not be tested individually, whereas the Raptor engines are. But note a key fact: even when tested, Raptor engines still fail at high rate:

SpaceX should withdraw its application for the Starship as an Artemis lunar lander.
It is my contention the attempt of SpaceX trying to reach a 2025 deadline to have the SH/SS flying and with multiple successful test flights completed puts undue pressure on its normal safety procedures. For that reason my opinion is it should withdraw the Starship for consideration as a lander for the Artemis III lander mission.
http://exoscientist.blogspot.com/2023/08/spacex-should-withdraw-its-application.html

1) You don't know that a Raptor failed on the boostback.  All we know is that it didn't start.  We have zero reason to believe that there's something wrong with that particular Raptor. In fact, since it fired up just fine for the landing burn, we have evidence that the Raptor worked just fine, and the failure-to-relight during boostback was due to something else.

2) You don't know that a Raptor failed catastrophically on SS.  All we know so far is that it RUD'ed, and Musk's tweet about a leak above the false ceiling.  Was it inside a Raptor?  It's possible, but we have no evidence to support the conclusion you consistently jump to.

3) How is that "standard industry practice" working out these days?  How well did it work for SLS?  How well did it work for New Glenn?  Both of them had second-stage issues, didn't they?  All three are at a similar stage of development.  BONG started in 2013, similar to Starship's early concept.  SLS started in 2011, with a huge head start on propulsion.  Starship (effectively re-)started development in 2017, when it was shrunk to a 9m diameter.  Money spent so far?  SS/SH: ~$7B.  New Glenn?  I'm not sure.  SLS?  hehe...$23 Billion and counting.  Between the three, it's pretty clear that the "standard industry practice" isn't bringing the benefits you imagine it does.

[GuessingEveryDay]

I think I found a map for what the NOTAMs looked like for the IFT-7's launch plan.

Turk and Caicos is very helpfully labelled on the map.

[K^2]

12 minutes ago, JoeSchmuckatelli said:

Had something unforseen or injuries to a third party - I'd agree with you 

I think that's the crux. It's a rocket test. Everyone involved in it should at least have been prepared for it to go spectacularly wrong. And investigation is primarily for the benefit of the team building the thing, so they might as well be the ones to do it.

If safety concerns are raised, these should be investigated separately, but even then, access to actual debris and establishing cause of the accident might be entirely unnecessary. Again, outside of SpaceX and these curious, nobody really cares why it blew up, and it wasn't a surprise to anyone that it could. So safety precautions would have to be built on that assumption, and if they were insufficient, the investigation would be into why proper safety procedures weren't followed or if there is a reason why these were not enough. These kinds of investigation happen in aviation all the time, and that's how it gets to be a safe industry.

There is a question of costs due to disruption to normal traffic and environmental impact and how the company conducting the test should be recompensing all these impacted. But again, in this particular case, it's probably on airline companies to sue SpaceX if they believe their time tables were sufficiently delayed. Given that the impact on traffic was that of a moderate thunderstorm, I doubt anyone will want to waste the effort. If such disruptions happen often and without proper warning, I can see it being escalated, though.

I'd also complain more and louder if this was a hydrazine rocket. MethaLOx gets a 'meh' from me. It's not that dumping rocket debris of any kind into the ocean is great for the environment, but as far as I'm aware, it's all pretty benign. A shipping vessel crossing the ocean will dump more hazardous materials (through leaks, corrosion, and accidents) during its voyage than what ended up in the ocean from Flight 7, if I had to hazard a guess. (I'm happy to stand corrected.)

I have general concerns about the program as mentioned earlier. And everything I was able to find on procedurals and hazard zones before the explosion makes me feel uncomfortable, as the traffic exclusion zones got activated only after the breakup. I haven't flown in nearly a decade, though, and even if there were deficiencies, it's on FAA to figure them out, and amend how they work with SpaceX going forward. Either way, it's not really a complaint about Flight 7.

[darthgently]

5 hours ago, Exoscientist said:

The comparison of the Superheavy/Starship to the N-1 rocket has been claimed invalid as N-1 rocket engines could not be tested individually, whereas the Raptor engines are. But note a key fact: even when tested, Raptor engines still fail at high rate

The failure rate of Raptor you come up with is horribly vexed by lumping v1 and v2 together and making fantastic counterfactual connections between phenomena both observed and imagined as always being rooted in an often hypothetical Raptor failure.  

Additionally you harp on industry standards that do not exist as standards.  Your methodology is not methodological.

Finally, your most fervent posts here always contain a link back to your blog.  Given these public forums are indexed by Google and other search engines one logical conclusion would be that these fervent posts are planted here purely to drive traffic to your blog from people cherry-picking the internet for sour SpaceX takes.  If I’m reaching, it isn’t nearly as far as you are reaching with the Raptor disphoria

Edited 2 hours ago by darthgently

[Ultimate Steve]

3 hours ago, Exoscientist said:

I agree with him that an engine not starting or not completing its burn counts as an engine failure.

If that's the one thing you took away from that post then you might need to read it again.

It is not a reasonable position that Raptor is unreliable because on flight 1 none of the 33 Raptors got to the end of their burns, therefore Raptor is at 0/33 and had 33 engine failures.

I took the widest possible definition of engine shutdown for the sake of argument and then pared that down to failures that were conclusively or likely the fault of Raptor by removing failures confirmed to be caused by something else. If I remember right I only ended up with a few actual suspected Raptor failures.

If you are curious as to how I would rate this flight, to my knowledge, the current indication is that the upper stage engine shutdowns were all related to the fire above the engines (likely caused by leaks in the newly redesigned fuel feed system) because of that compartment exploding/bursting.

The booster engine not restarting during the boostback is an open question. I think this is most likely the engine saying "Hey I probably can't restart given these conditions but I don't think I'm broken" and the flight computer decided to play it safe and not send the ignition command. This tracks with it being seen working just fine later.

This is hard to classify as to my knowledge this hasn't really happened before, as having a vehicle with enough engines to do this with is a very new thing.

However I must steel man this in your favor as we do not have any official indication, putting flight 7 at 58/59 until the time when we receive further indication.

Quote

How many total test flights needed now just to make orbit with high payload? 10? A dozen? How many total to prove Raptor reuse reliability? 15? How many total to prove orbital refueling? 20? In contrast standard industry practice is to construct a separate, full test stand to do full up, full thrust, full duration testing. Done this way at least Starship could be doing expendable flights already by now, and with paying customers. Even Raptor reuse reliability could have been tested on the full test stand, providing a faster route to Starship reuse.

(emphasis mine as to what I'm currently responding to)

 

I think you are misunderstanding the short/medium term goals of this program. Starship is not the product of a typical scenario, where a company needs to start flying customer payloads ASAP to start generating profit.

They could have focused on delivery of customer payloads immediately. However here is a list of Starship's current launch contracts and launch plans:

 

Confirmed contracts (note that some of the Lunar payloads are expected to rideshare):

• HLS and all of the test/flight/refueling launches that requires
• Astrolab's FLEX rover, to be delivered to the Moon, requiring refueling
• Superbird-9, a geostationary communications satellite to be launched to GTO by Starship, possibly with and possibly without refueling, that is unknown. Scheduled for 2027.
• Starlab LEO station, no earlier than 2028
• Lunar Outpost's Eagle rover, to be delivered to the Moon, requiring refueling

Other plans without (public) signed contracts yet:

• OffWorld's Lunar ISRU demo (to the Moon, needs refueling, though will likely rideshare with something else)
• JAXA's Lunar Cruiser rover (though does have a statement of intent from NASA specifying delivery to the Moon in 2032 via Starship, needless to say with refueling)
• Polaris 3 if that is still happening, requires ability to land on Earth
• VAST Haven-2 core is planned for Starship with no contract yet, this is going to be very late 2020s at best. If Starship does very well in the cost department, some of the other modules could switch from long-fairing Falcon Heavy to Starship.
• All of the internal Starlink Stuff, does not strictly require reusability but Starlink is banking on cheap launches so if they don't do this reusably it is very bad for Starlink
• All of the internal Mars stuff, requires refueling and the ability to land on Mars

(I am also assuming here that refueling is not economical without reusability)

 

The entirety of Starship's contracted and planned mission set that can be accomplished by an expendable non refuelable variant is... 3 missions. Superbird-9 (assuming expendable Starship can push it to GTO), Starlab (assuming it is selected for CLD), and one (though possibly more) module of Haven-2, assuming it is actually built. And they have somewhere around 2-3 years until they have their first relevant launch contract depending on when in 2027 they want to launch Superbird-9.

For the sake of argument, I will point out that Superbird-9 was originally supposed to launch in 2024. No clue if the delay there is because of the satellite or because of the launch vehicle. But for the sake of Steel-Manning this, I'll assume Superbird-9 has been sitting finished in a Hangar since December 2023 and 100% of the blame falls on SpaceX.

In that case, SpaceX missed out on a grand total of 1 commercial launch by not choosing to go expendable at first.

 

To get to the point, SpaceX effectively has 2-3 years with little obligation besides getting re-entry, reuse, and refueling ready for all of its other launch contracts. And as such that is what they are doing.

A rapidly reusable, cheap, and reliable heat shield has never been built before. From what I can tell, that is the long pole that is currently driving the schedule. It is a prerequisite for:

• Cost effective refueling at all
• High cadence refueling (generally required for boiloff sensitive missions, or if you want to do more than 1 moon mission per year)

And therefore it is also a prerequisite for most if not all missions that require refueling, which is the majority of their current contract roster.

Thus it makes complete sense why SpaceX has been focused on proving reusability/heat shield functionality while neglecting payload delivery. They do not want to build a payload delivery system and then retrofit in reusability. They want to build a reusable system and then they will use it to carry payloads.

 

In that case, 10-12 and more flights to prove high payload delivery is completely acceptable, as these early flights are not looking to prove that, that will come later.

 

Quote

How many total to prove Raptor reuse reliability? 15?

Considering it took Falcon 9 until flight 33 to do full Merlin reuse, doing it in 15 would be amazing. Though let's be generous, they didn't even start attempting supersonic retropropulsion until flight 6, so 28 flights.

I'm currently about 50/50 on whether they will wait until booster v2 to reuse a booster or if they are going to go full send and reuse the booster that was just caught. So there is a world in which this is <10.

 

Quote

How many total to prove orbital refueling? 20?

This I am less sure of. This demo must absolutely happen this year to protect against a stupid amount of delays in every other planned mission. However (and I could be wrong or maybe this person misspoke or maybe the person I got this info from is wrong), I think someone at NASA recently said that Ship V3 is going to be required for the refueling demo. If this is accurate, refueling could be a ways away, as it would shift pretty much all of V2 towards early catch/reuse/heat shield testing. This is one thing I am actually somewhat concerned about.

 

Quote

In contrast standard industry practice is to construct a separate, full test stand to do full up, full thrust, full duration testing.

Of the western(-aligned) rockets (as I'm unlikely to find anything about the Chinese rockets) to debut since 2020:

• Ariane 6 did a full duration static fire of the core but without the boosters, a configuration that results in a thrust somewhere near 10% of liftoff thrust in the 4 booster configuration, and is such, not a full up, full thrust, full duration test. Points for at least doing it with boosters, upper stage, and fairings attached though. I cannot find good sources but I think that "proper" sort of testing might have been done for the second stage.
• H-3 did not do full up, full thrust, full duration testing as far as I can tell. At best the core stage was fired for ~25 seconds without the boosters, though I cannot find any information about the upper stage.
• SLS did do a full duration test of the core stage, but without the boosters, and without anything above the core attached (if my memory is correct). This is about 25% of the liftoff thrust of SLS. Unsure if the ICPS had been static fired, but given that it has a lot of flight heritage there wouldn't have to be any SLS specific static fires.
• Vega C might count as its first stage as test fired, though horizontally, and not with the rest of the stages attached. But I'll give it a point.
• Firefly Alpha did at least a 42 second static fire of its first stage, If it did a full duration firing, it went under my radar.
• Starship does not do full duration static fires.
• New Glenn did a 24 second static fire.
• Vulcan to my knowledge never completed a full duration static fire of the core stage, only short duration static fires, and with no boosters.

Might have missed a few and I definitely got lazy on checking upper stage tests. But it does not appear that this is the industry standard any more.

When all up stage testing was done, it was typically done on sustainer type rockets, with a small to moderate percentage of the total liftoff thrust active.

The rocket that gets the closest to the type of testing you desire appears to be Ariane 6.

I don't see you dragging Vulcan or New Glenn through the mud for only doing partial duration partial thrust static fires on the launch pad like Starship does.

 

There's more but I've spent enough time on this for today.

[tater]

That bogus N-1 comparison is still a thing? Yeesh. In the 60s their ability to simulate, well, anything, was near 0, so the choice was run ground tests they could, even if not really applicable to flight—because it was the tool they had—or fly. These days once the engine is steady state, real life data is there, and for flight, simulation is far better than a long, useless static fire. Note that all telemetry, including engine states feeds their simulation model for the engines. Each flight test lets them know how their model compares to actual flight characteristics—which allows the model to be refined.

 

[Codraroll]

2 hours ago, tater said:

This is true for every rocket incident.

How would FAA possibly lead an investigation? Tap one of the many highest level rocket engineers they employ? Use their massive infrastructure to test rocket components? Good thing the very best and brightest aerospace engineers graduate and immediately apply to FAA, then SpaceX, BO, etc get the dregs.

I work in building inspection for the local city planning office, and we use a somewhat similar approach. If a building is found to have a flaw beyond the legal tolerance upon inspection (and we see a lot of those), the first step is always to ask the people who built it to clarify what's going on, and present their improvements. After all, they know the project, they know the process, and they are overall the best positioned to find out what went wrong. Our mandate is not to perform any fault analyses, but to mandate that they are performed. Often, it can even be documented that what we saw was within the legal tolerance, after all. But our job is to ask, and if necessary hold back the certificate of completion until we've received a satisfactory answer.

I would presume that the logic is the same here. FAA isn't doing the investigation themselves, but they know what an investigation must include to be satisfactory, and they can mandate SpaceX to present those relevant documents. In the meantime, they can hold back launch licenses or impose other sanctions.

What would be truly worrying, though, is if the FAA was pressured from above not to follow due procedure in the case of SpaceX. That they were required to grant launch licenses despite serious mishaps, because their CEO is chummy with the President, and also running a Department of Loyalty with the mandate to dissolve governmental bodies believed to be interfering with the whims of the Pepelord, or whatever he calls himself these days.

[tater]

9 minutes ago, Ultimate Steve said:

There's more but I've spent enough time on this for today.

Yeah, it's old man yelling at the sky nonsense you're dealing with.

My own take would be that "industry standard" is meaningless. First principles, you'd want to test what you can test on the ground, simulate what can be simulated—and testing should be designed in part to calibrate simulations, then fly for what cannot be adequately tested on the ground. SpaceX famously tests things end to end on the ground. They built an entire F9 control package that they can test on the ground—the sort of thing that would have caught the clock issue with CST-100 on Atlas V. This allows them to swap in new elements, and test on a simulated flight. They do the same I am sure with SS/SH.

A "full duration static fire" contains some substantial multiple of the risk of an actual launch, and gives real world data that mirrors flight for just the first few seconds. The rest of the fire would be effectively useless. No loads on the vehicle, no maneuvering (slosh, etc). Pointless—but dangerous! They don't do it because it's idiotic to do it.

[Codraroll]

19 minutes ago, Ultimate Steve said:

There's more but I've spent enough time on this for today.

By the way, I appreciate seeing new in-depth explanations like this, even if it doesn't sink in with the intended audience, who takes away from i.e. this paragraph ...

19 minutes ago, Ultimate Steve said:

It is not a reasonable position that Raptor is unreliable because on flight 1 none of the 33 Raptors got to the end of their burns, therefore Raptor is at 0/33 and had 33 engine failures.

... the following message:

19 minutes ago, Ultimate Steve said:

It is ... a reasonable position that Raptor is unreliable because ... none of the 33 Raptors got to the end of their burns, therefore Raptor ... had 33 engine failures.

Edited 1 hour ago by Codraroll

[K^2]

17 minutes ago, tater said:

That bogus N-1 comparison is still a thing? Yeesh. In the 60s their ability to simulate, well, anything, was near 0, so the choice was run ground tests they could, even if not really applicable to flight—because it was the tool they had—or fly. These days once the engine is steady state, real life data is there, and for flight, simulation is far better than a long, useless static fire. Note that all telemetry, including engine states feeds their simulation model for the engines. Each flight test lets them know how their model compares to actual flight characteristics—which allows the model to be refined.

I agree with the broader sentiment, and the situation is very different between the tech and knowledge we have now and back when N-1 was developed. However, there are problems we can't address with simulation, because they are due to an interaction with other systems of nearly infinite complexity. Flight 7 is a good example. Simulating one engine and proving it to be perfectly stable wouldn't have prepared you for how it failed in concert with the rocket. And when you add more engines, you increase the number of potential points of failure that you did not foresee in a simulation.

So instead of the problem with N-1, where you multiply failure rates of individual engines, you are multiplying factors that have nothing to do with an individual engine. The outcome is still an exponential growth. One you have better control over, but not one you can eliminate entirely.

Naturally, building a small number of giant engines also has issues, especially in context of reusability. And the pros vs cons of Saturn V vs N-1 approach are on a completely different set of scales now because of history, technology, manufacturing processes, the economies involved and so on, and so on. But neither is it fair to say that the inherent problem of N-1, that, "More engines = more things that can go wrong," has disappeared. It's not something you get to just ignore and pretend it doesn't matter now, because the simulation tells you that the engine is 100% reliable, and all tests show that when running in conditions identical to the test, that really is so. Because the engine will never run in conditions identical to simulation in a real mission. Nothing we invented lets you take that risk factor to zero, which is the only case where you could claim that comparisons to N-1 are bogus.

That said, without taking this risk, I'm not sure we'd be getting a super heavy at all. So they either get it to work and fly safely, or they don't, and it's not so much about the road not taken.

Just so long as nobody pushes for a crewed launch before the system has been properly tested. The biggest risk of Starship due to above mentioned problems with the booster and the shifts in company culture is that when Starship is "done" and has undergone a few successful flights, we won't have nearly the certainty that the rest of them will fly safely until we launch enough for a statistically significant sample. And if the corporate types at SpaceX try to convince the regulators that the Falcon and Soyuz safety records are an indicator that Starship is ready, I only hope there are people in whatever admin's in charge at the time that will call them out on this BS. We need to see dozens of flight in a row without failure to declare the Starship safe enough to even start running crewed tests.

[tater]

Love posts dropped that should not have been posted (because they break the rules in the way only 1 side of a multiside political system ever does here), but you can't reply to without violating the same rules that were violated in the first post that you really want to reply to.

But I can reply to this post at least...

 

3 minutes ago, K^2 said:

Flight 7 is a good example. Simulating one engine and proving it to be perfectly stable wouldn't have prepared you for how it failed in concert with the rocket. And when you add more engines, you increase the number of potential points of failure that you did not foresee in a simulation.

What engine failure? The one on the SH boostback that failed to restart, then restarted just fine on landing? Nothing about either of those burns would be simulated in a static fire at all—a static fire is a sort of analog simulation, after all. We have no idea why it didn't restart for boostback, maybe more teething issues with slosh/ice? Clearly it didn't matter (they have loads of engines, and engine out capability is a good thing).

8 minutes ago, K^2 said:

Just so long as nobody pushes for a crewed launch before the system has been properly tested. The biggest risk of Starship due to above mentioned problems with the booster and the shifts in company culture is that when Starship is "done" and has undergone a few successful flights, we won't have nearly the certainty that the rest of them will fly safely until we launch enough for a statistically significant sample. And if the corporate types at SpaceX try to convince the regulators that the Falcon and Soyuz safety records are an indicator that Starship is ready, I only hope there are people in whatever admin's in charge at the time that will call them out on this BS. We need to see dozens of flight in a row without failure to declare the Starship safe enough to even start running crewed tests.

I would assume this would be the case. Course the retroactive assessment of early Shuttle flights was that the LOC probability was 1:9, so if anyone is brave enough to take that sort of risk who am I to say no?

Related to the part of my reply that is NOT a reply to you, what's with "will call them out on this BS"? This BS? Some current BS regarding crew safety? I'm confused, SpaceX is no where near launching crew on Starship (and the risks for lunar ops are different (better in some ways, worse in others I imagine).

[K^2]

4 minutes ago, tater said:

I would assume this would be the case. Course the retroactive assessment of early Shuttle flights was that the LOC probability was 1:9, so if anyone is brave enough to take that sort of risk who am I to say no?

Generally, I'm on board for letting people put themselves at a risk they fully understand on a voluntary basis. When Mad Mike Hughes was building his steam rockets I had zero objections - he clearly knew what he was doing and how it can end.

I start liking it less when large corporations are paying a crew to take on a risk, because now we're getting into significant power disbalances. It's worse if the crew is under military service or another obligation. Even so, this is a limited concern. If SpaceX says, "Hey, we have conducted enough tests, and can honestly conclude that there is a 10% chance it will blow up, but we want to try anyway," my ethical concerns stop at making sure the crew understand the gamble and are prepared to play Russian Roulette for whatever prize money is on the table.

The thing I'm afraid of is SpaceX instead declaring that the Starship is safe when their tests do not fully support that conclusion. Consent to risk cannot be built on a lie.

And yes, this hasn't happened yet. My fear is based entirely on how Tesla has done this exact thing with their "autopilot," lack of 3rd party testing on Cybertruck, and so on, and still standing on PR that their vehicles are safe. SpaceX has started as a very different company, but they have lost a lot of people who got SpaceX to where it is and built hat safety and transparency into the Falcon program. Current leadership seems to be going for a Boeing and Tesla approach instead.

And yes, this is all hypothetical, and if none of it happens, great. I was worried over nothing. I'll take that gladly. But if in a couple of years we see SpaceX leadership stand there and declare that "Starship is safe," after it managed ~5 complete test flights, do think back to this discussion.

[AckSed]

In the end, this is a very human issue: trust. How much do we trust the major shareholder of SpaceX? How much do we trust the COO, the project manager, the engineers, the welders, the ground-support staff that they are all doing their jobs behind the scenes?

[tater]

25 minutes ago, K^2 said:

The thing I'm afraid of is SpaceX instead declaring that the Starship is safe when their tests do not fully support that conclusion. Consent to risk cannot be built on a lie.

I don't see them "declaring it safe" being a thing with few flights. I also don't see the incoming NASA Admin hopping aboard as a private citizen in the next 4 years—and he was presumably the volunteer, though not paid, he'd actually pay for the ride. So far the 2 SpaceX engineers that flew Dragon seemed pretty amped to do so, I doubt offering Dragon rides would require corporate pressure. The original Boeing astronaut bailed on CST-100 as I recall...