totm nov 2023 SpaceX Discussion Thread

[Deddly]

2 hours ago, darthgently said:

first reusable and disposable rocket engine with zero, or very near zero, maintenance

Excuse my ignorance, but is maintenance of a disposable rocket engine an actual thing? Like, they have to do refurbishments between test fires or something?

[darthgently]

1 hour ago, Deddly said:

Excuse my ignorance, but is maintenance of a disposable rocket engine an actual thing? Like, they have to do refurbishments between test fires or something?

“Disposable” after N reuses or out of spec.  Disposable in the sense that repair is not cost efficient.  If that makes sense.

Edited Thursday at 09:37 PM by darthgently

[AckSed]

1 hour ago, Deddly said:

Excuse my ignorance, but is maintenance of a disposable rocket engine an actual thing? Like, they have to do refurbishments between test fires or something?

Working off old, third-hand info from USENET, the answer is yes, for the reason you're thinking. Anything with an ablative nozzle or liner, or pyrotechnic starter is truly fire-once, but you don't scrap an engine after test-stand and hold-down firings.

[darthgently]

I probably confused things as most would consider single use engines as being the normal meaning of disposable engine but I meant it in the mostly maintenance free sense. Like cell phones with non-accessible batteries and so much glue they aren’t meant to be repaired.

[magnemoe]

2 hours ago, Deddly said:

Excuse my ignorance, but is maintenance of a disposable rocket engine an actual thing? Like, they have to do refurbishments between test fires or something?

Its some benefit to have an rocket engine who can be test fired then fitted to an disposable rocket. Who is most rockets with a few exceptions. 
This was an problem with the N1 as the engines could not be test fired. 
Its true for solid fuel rockets but they are much simpler than an high performance liquid fueled one. 

[darthgently]

SpaceX Starlink revenue now almost double SpaceX launch revenue.  Total $13.1B

https://payloadspace.com/estimating-spacexs-2024-revenue/
 

[tater]

48 minutes ago, darthgently said:

SpaceX Starlink revenue now almost double SpaceX launch revenue.  Total $13.1B

https://payloadspace.com/estimating-spacexs-2024-revenue/
 

Starlink revenue has more room to grow than launch services as well.

[darthgently]

‘Ere we go, damn the torpedoes

 

[Superpluto126]

BATTEN DOWN THE PAYLOAD DOOR! 

 

We're gone starhopping

[darthgently]

 

[tater]

 

 

[Ricktoberfest]

On 1/30/2025 at 8:34 AM, Exoscientist said:

 Thanks for that impressive review of the Raptor tests. I can say confidently that nobody outside of SpaceX has examined the data on the Raptor tests firings in that detail. In fact, probably many in the propulsion division at SpaceX would find this data review useful. You should definitely post it to the NSF forum and that Discord server on Starship you mentioned.

 You raised a possible explanation for the lack of testing in this data specifically of the actual 3-burn times of an actual mission that perhaps they were done earlier than in this data set. Perhaps. But that would mean they would be on Raptor 1’s. But Raptor 2 and the upcoming Raptor 3’s operate at higher pressures and thrusts. It would be essential to run these tests as well on the later incarnations.  

 Another possibility you mentioned is perhaps they found if a engine ran successfully for a short time that is sufficient to qualify it for running at the full burn time times. I can’t rule that out. But also we need to consider the possibility that the reason some of these static tests were at short burn times was because indications were the engines were getting so far out of nominal that they had to be shut down. This happened multiple times during the flight tests for instance.

 When I say SpaceX is giving an inaccurate portrayal of Raptor reliability I don’t mean they are providing invalid telemetry. I mean in a more basic sense. We know in at least one case in the later test flights, IFT-4, that a Raptor exploded during a landing burn. But SpaceX has not acknowledged it or explained it. Given the prior instances such as during the tests of the SpaceX landing procedure of Raptors leaking fuel and catching fire leading to subsequent explosions, it seems quite likely that leaks and fires also occurred on the IFT-4 flight before that engine exploded.

 Since the Raptor does have this known tendency to leak and catch fire, the possibility still obtains that the plumes seen shooting up the sides of the booster during the landings burns could be due to such leaks and fires. In this regard it is quite notable in the ocean landing of the Starship in IFT-5 flames were seen shooting out of the side as well. See at about the 12 second point in this video on the right side:

https://youtu.be/t-2Wj0NyKQY?si=9KJ-r16nmbfjpoek

 Previously, SpaceX made the argument to the FAA that mishaps investigations were not necessary if no danger to the public was involved. But now we have an instance in IFT-7 that potentially a danger to the public could have arisen from a Starship explosion. SpaceX has made a preliminary appraisal the explosion was due to a failure in the plumbing, not the engines. Perhaps. But given the Raptors tendency to leak and catch fire, the FAA should require SpaceX to release any and all videos of the engine bays in both stages when their engines are firing to be sure.

    Bob Clark

 

I think you’re in a dream world where you think your opinion on the issues with a private rocket matter. Go ahead and ask the air force for black box data and video from in cockpit on the f35 that crashed in Alaska while you’re at it. Unless you happen to work for spacex (haha) or a government agency that would handle an investigation into the crash of a prototype rocket- you’ll only ever see what they want to be seen. Nothing abnormal about that at all.  The fact that you keep complaining about this makes everyone assume you must be trolling. No one else would even consider that they have a right to access such information. 

[Exoscientist]

12 hours ago, Ricktoberfest said:

I think you’re in a dream world where you think your opinion on the issues with a private rocket matter. Go ahead and ask the air force for black box data and video from in cockpit on the f35 that crashed in Alaska while you’re at it. Unless you happen to work for spacex (haha) or a government agency that would handle an investigation into the crash of a prototype rocket- you’ll only ever see what they want to be seen. Nothing abnormal about that at all.  The fact that you keep complaining about this makes everyone assume you must be trolling. No one else would even consider that they have a right to access such information. 

 That would be true if there were no issues of a danger to the public. But with the IFT-7 explosion public safety issues have arisen. 
 

A hypothetical scenario: suppose during the IFT-7 investigation the FAA finds Raptors commonly leak and catch fire during their landing burns, but SpaceX is able to contain the fires with fire shields and fire suppression. Do you think the FAA would keep that information from the public? Do you think the FAA should keep that information from the public?

 By the way, with so many airplanes having to be diverted after the IFT-7 explosion the NTSB may get involved in the investigation. The NTSB is much more hands on with their investigations than the FAA, which commonly let the companies themselves do the investigating. 
 

  Bob Clark

[darthgently]

Crocodile Dundee:  That’s not a traveling block.  This is a traveling block!

 

[Meecrob]

On 1/17/2025 at 11:52 AM, 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

 

  Robert Clark

 

Look Robert, the N-1 failed because they couldn't test their engines before flying them, and thy didn't have the advanced computer controls that we do here in the west.

Let them flight test. And its not like NASA is up to speed

[magnemoe]

9 hours ago, Meecrob said:

Look Robert, the N-1 failed because they couldn't test their engines before flying them, and thy didn't have the advanced computer controls that we do here in the west.

Let them flight test. And its not like NASA is up to speed

As I understand they could not test the engines without rebuilding them who negate most of the benefit of test firings outside of statistic over reliability. Kind of like you do with ammo. 
And yes if one engine failed they had to shut down the opposite one, not sure if this was control?