totm nov 2023 SpaceX Discussion Thread

[darthgently]

2 hours ago, Mikki said:

bet that SpaceX will review their flipping maneuver, because this is physically just madness to the machinery.

Or they scrap the idea of 33 single engines in favor of a few bigger ones or shared pump assemblys to save on complexity alltogether.

I think you bring up good points about the gyro effects but doubt they'd go to bigger engines.  I'm guessing maybe only having the 3 center vectored engines share larger pumps along the lines you describe perhaps and only having those engines running during the flip?

5 hours ago, Exoscientist said:

Congrats to SpaceX in getting the booster to successfully fire all 33 Raptors during the ascent portion of the flight. I admit I didn’t have confidence this would be accomplished on this 2nd test flight given the Raptors history of leaking fuel and catching fire. The failure after stage separation probably had something to do with the recovery part of the flight, and I’m confident that can be fixed.

 However, I have to say I think the failure of the 2nd stage probably had to do with the engines. I’m guessing likely it was the vacuum Raptors since the sea level Raptors worked fine.

  Robert Clark

But the vacuum engines were burning continuously  from stage separation on, so not sure about your conclusion.

[JoeSchmuckatelli]

2 hours ago, mikegarrison said:

If STS had blown up on the first launch in the first stage, and then had blown up again on the second launch in the second stage, absolutely no one would be claiming these were great tests and a great learning experience.

 

Because that is not the design process of STS. They're on the 'zero defects' with public money train. 

 

2 hours ago, mikegarrison said:

 

The goalposts are different for SpaceX -- among the SpaceX fans, anyway. 

Partly because before SX started this whole thing they announced 'move fast and break things' and then along the way rebuilt domestic rocket capabilities that are both innovative and regularly functional. 

2 hours ago, mikegarrison said:

. But among the general population, don't expect the "whatever happens, we learn something" thing to be a popular viewpoint.

 

I can't even get the general population interested in space or rockets at all - to them it's background noise.  But, yeah, if STS tried this with public funding they'd be liquided. 

OTOH - if the companies that make up the STS team paid for rapid iterations and then sold a finished product to the US?  Might be a different take 

[darthgently]

8 hours ago, Brotoro said:

Super Heavy seemed to flip pretty fast. Maybe if they go a bit slower on the flip, they might be able to avoid propellant feed issues.

The failure of the Starship to reach SECO was more of a surprise, considering that it was ticking along fine for several minutes.

And put less gyroscopic forces on the pump blades as Mikki pointed out.  Could be a win in both ways

[Minmus Taster]

3 hours ago, darthgently said:

FTS on SS may have been incomplete.  I'm wonder if something like integrating an off the shelf (or custom probably) black box on the second stage could over time make situations like this, and Rocket Labs recent situation, less mysterious.  Of course they'd need to be very tough and recovered.

Not sure how to feel about that, on the one hand the ship was effectively destroyed and even surviving chunks would burn up shortly afterwards. On the other hand this could be grounds for another months long investigation which wouldn't be good for the program given previous delays.

Also: It's possible more pieces survived because the fuel tanks were nearly empty, without the extra help only the installed system would be tasked with the termination (B9 clearly still had a lot of fuel inside it's tanks when it came apart)

[JoeSchmuckatelli]

8 hours ago, Brotoro said:

failure of the Starship to reach SECO was more of a surprise, considering that it was ticking along fine for several minutes

I'm betting that whatever caused the 'LOX started dropping faster near the end' situation will be the interesting thing to watch. 

What caught my attention was commentary about losing signal and hoping to test connectivity via Starlink on the SX stream.  Because of that I assumed for hours that it was an intentional / automatic destruction based on inability to control the vehicle. 

But after smarter folks than I pointed out the changed tank expenditures... Something mechanical / structural clearly happened 

Edited November 19, 2023 by JoeSchmuckatelli

[Mikki]

34 minutes ago, darthgently said:

And put less gyroscopic forces on the pump blades as Mikki pointed out.  Could be a win in both ways

I just re-read Alemberts gyroscopic theory and it states that fast rotating bodys exert unusual very high counterforce (torque) tangential to a second applied rotation (force vector), which are unpredictable and surely very uneven on complex shapes like pumprotors.

You can calculate this force on a fast rotating straight rod, but a pumpshaft with curved blades and impellers  is just structural chaos. 

Edited November 19, 2023 by Mikki
Typos:) and stuff

[tater]

2 hours ago, Minmus Taster said:

Not sure how to feel about that, on the one hand the ship was effectively destroyed and even surviving chunks would burn up shortly afterwards. On the other hand this could be grounds for another months long investigation which wouldn't be good for the program given previous delays.

This is true of every single rocket that detonates—which is why they have NOTAMs, marine warnings, etc. It's not a big deal.

[Exoscientist]

2 hours ago, darthgently said:

I think you bring up good points about the gyro effects but doubt they'd go to bigger engines.  I'm guessing maybe only having the 3 center vectored engines share larger pumps along the lines you describe perhaps and only having those engines running during the flip?

But the vacuum engines were burning continuously  from stage separation on, so not sure about your conclusion.

 

  On the 1st test flight some booster engines worked fine at launch, but failed later on in the flight. The same could have happened with the vacuum Raptors, in regards to failing later in the flight. I have no information to confirm that, though. Whenever a rocket stage fails, the engines are the first thing focused on. Since the sea level engines worked fine, that leaves the vacuum engines to be scrutinized.

  Robert Clark

2 hours ago, Minmus Taster said:

Not sure how to feel about that, on the one hand the ship was effectively destroyed and even surviving chunks would burn up shortly afterwards. On the other hand this could be grounds for another months long investigation which wouldn't be good for the program given previous delays.

Also: It's possible more pieces survived because the fuel tanks were nearly empty, without the extra help only the installed system would be tasked with the termination (B9 clearly still had a lot of fuel inside it's tanks when it came apart)

 

 Is it known where reentry occurred?

  Bob Clark

[tater]

21 minutes ago, Exoscientist said:

 Is it known where reentry occurred?

There's literally a map/image of it up the thread a page or two.

 

[Exoscientist]

16 hours ago, AckSed said:

Oh wow. Astronomy Live processed raw footage captured off the Keys and found that the front half of StarShip was relatively intact and tumbling:

The front really did fall off!

 Can you say where in the video the payload section only is apparent after FTS?

  Robert Clark

[Royalswissarmyknife]

1 hour ago, Exoscientist said:

Since the sea level engines worked fine, that leaves the vacuum engines to be scrutinized.

The engines on the ship are much older then the booster so the sea level engines could still have been a issue for the ship.

[tater]

53 minutes ago, Exoscientist said:

 Can you say where in the video the payload section only is apparent after FTS?

That video is stream of consciousness (it was live at the time) From the moment he caught the explosion on the finder cam (not the main camera), the vehicle was split with the payload section intact. Makes complete sense since FTS is designed to open the prop tanks, and cause them to likely deflagrate. Tearing open the payload section would do nothing at all at 149km altitude unless there was enough explosives to shatter it as there are effectively no aero forces.

It then mostly burned up (as expected). Any stage that comes off with a suborbital trajectory does the same, only without FTS going off.

[tater]

 

[Deddly]

6 hours ago, Mikki said:

I just re-read Alemberts gyroscopic theory and it states that fast rotating bodys exert unusual very high counterforce (torque) tangential to a second applied rotation (force vector), which are unpredictable and surely very uneven on complex shapes like pumprotors.

You can calculate this force on a fast rotating straight rod, but a pumpshaft with curved blades and impellers  is just structural chaos. 

Don't/can't they have booster rotation on the same axis as the pump rotors? 

[Flavio hc16]

I truly hope they start to push hard for a December launch, as they are limited by 5 test/year.

 

[SunlitZelkova]

15 hours ago, tater said:

Sorry, I think I just find the N1 comparison tedious is all.

Yeah, lots of engines. Other than that? Meh, it's not the 60s.

Being a fan of the Soviet space program, I compare the two out of respect. I can understand how others compare the two in a negative light though.

The N1 was supposed to take humans to the vicinity of Mars in 1971 in its original conception, and then later was redesigned for the Moon, Earth orbital stations, and Mars landings. I don't really view the Soviets as having been competitors in the Space Race, but rather as fellow humans who had great dreams that did not come true.

Starship is going to avenge those who worked on the N1 and dreamed of conquering space with it, whose hopes were dashed by the Soviet system.

If anything I'd say the fact that the N1 exploded on the pad in 1969 but had slightly more successful flights afterwards should be treated as proof the design isn't crazy, rather than used as ammunition to argue against Super Heavy. But people tend to get caught up in the word "failure".

[magnemoe]

4 hours ago, tater said:

There's literally a map/image of it up the thread a page or two.

 

I assume this is first stage?

Second was flying at almost orbital velocity at +150 km with an AP of 250 km, blowing it up in vacuum would not affect the trajectory a lot, yes it will spread out the debris field quite a lot over the distance so would drag from the air. 
But if this is debris field from starship the telemetry was an obvious lie. 

[tater]

8 minutes ago, magnemoe said:

I assume this is first stage?

Second was flying at almost orbital velocity at +150 km with an AP of 250 km, blowing it up in vacuum would not affect the trajectory a lot, yes it will spread out the debris field quite a lot over the distance so would drag from the air. 
But if this is debris field from starship the telemetry was an obvious lie. 

Starship. Not "an obvious lie."

 

 

Literally the authority on these matters estimated the reentry point based on the streamed telemetry.

Edited November 19, 2023 by tater

[mikegarrison]

The ship was not headed for an orbital trajectory anyway, even if it had completed its burn.

[Ultimate Steve]

I can't wait until Starship deploys a Starlink, then this silly suborbital vs. Atmospheric unstable orbit vs. Orbit debate can end.

[magnemoe]

3 minutes ago, tater said:

Starship. Not "an obvious lie."

Literally the authority on these matters estimated the reentry point based on the streamed telemetry.

Now I assume this in the Caribbean, if somewhere like the Indian ocean ignore rant. Else can someone explain there 15-20.000 km/h went and let it fall down so fast as orbital mechanics don't work like that. Starship should continue on its path even if blown up. I think all here agree on it.

This leaves some options: 1) the guy talking mixes up superheavy and starship fields 2) SpaceX lied on the telemetry, I see this as very hard to do, for one other was watching this including NASA and other powers. 
3) they somehow cheated, say generate a lot of drag in 150 km attitude or somehow.
1) is the simplest answer, yes its much more east than I would expected from superheavy but it did not do an braking burn like F9 does.

No it was not an orbit and they missed more than I imagined, its 27000 km/h and they only reached 24, but it should still reach much longer? Again easy to use KSP to test this, it reached 88% of orbital velocity with an AP clearly in space.
And yes KSP is not accurate but here +-100% does not matter. Will you clear the ocean east of KSC? Gone try this myself. 
 

[tater]

1 minute ago, magnemoe said:

This leaves some options: 1) the guy talking mixes up superheavy and starship fields 2) SpaceX lied on the telemetry, I see this as very hard to do, for one other was watching this including NASA and other powers. 

He's cataloged pretty much every orbital object for decades as a hobby when he's not at work at the Harvard–Smithsonian Center for Astrophysics (or Chandra Observatory).

He's mixing up nothing at all, the telemetry was fine.

[CatastrophicFailure]

 

18 minutes ago, Ultimate Steve said:

I can't wait until Starship deploys a Starlink, then this silly suborbital vs. Atmospheric unstable orbit vs. Orbit debate can end.

I'm betting the first "true orbit" flight is S27 as a cryo-transfer demonstrator, snag some quick contract payouts.

11 minutes ago, magnemoe said:

Now I assume this in the Caribbean, if somewhere like the Indian ocean ignore rant. Else can someone explain there 15-20.000 km/h went and let it fall down so fast as orbital mechanics don't work like that. Starship should continue on its path even if blown up. I think all here agree on it.

This leaves some options: 1) the guy talking mixes up superheavy and starship fields 2) SpaceX lied on the telemetry, I see this as very hard to do, for one other was watching this including NASA and other powers. 
3) they somehow cheated, say generate a lot of drag in 150 km attitude or somehow.
1) is the simplest answer, yes its much more east than I would expected from superheavy but it did not do an braking burn like F9 does.

No it was not an orbit and they missed more than I imagined, its 27000 km/h and they only reached 24, but it should still reach much longer? Again easy to use KSP to test this, it reached 88% of orbital velocity with an AP clearly in space.
And yes KSP is not accurate but here +-100% does not matter. Will you clear the ocean east of KSC? Gone try this myself. 
 

Starship was around 3000kph/830m/s short of orbital speed. Doesn't seem like much on the surface but that's a LOT of difference in the shape of an orbit. Gonna plug this into RSS right now out of curiosity. 

[Flavio hc16]

19 minutes ago, magnemoe said:

.

No it was not an orbit and they missed more than I imagined, its 27000 km/h and they only reached 24, but it should still reach much longer? Again easy to use KSP to test this, it reached 88% of orbital velocity with an AP clearly in space.
And yes KSP is not accurate but here +-100% does not matter. Will you clear the ocean east of KSC? Gone try this myself. 
 

Then you haven't  played KSP enough: try to reach 88% of orbital velocity in KSP, and you will see that you will cover less than 20% of the planet. It's the last few hundreds m/s that makes you go places. And this is eve more pronounced with a bigger Kerbing, aka Earth.

[magnemoe]

19 minutes ago, tater said:

He's cataloged pretty much every orbital object for decades as a hobby when he's not at work at the Harvard–Smithsonian Center for Astrophysics (or Chandra Observatory).

He's mixing up nothing at all, the telemetry was fine.

Add some extra information from an fast google. 
An minuteman ballistic missile has an maximum velocity of 24000 km/s who was the velocity Starship had at cutoff.  has an max range of 6000 miles or 9600 km, it however has an ceiling of 1,120, this improves accuracy as less time in the atmosphere and Starship AP was 250 km, but ignore this and focus on 9600 km  who is around 1/4 of the earth diameter. 
https://www.atomicarchive.com/almanac/forces/minuteman-III.html

Note I does not discredit source, but people make mistakes making posts. Myself did not know they blew up Starship until reading it here. 

 

Edited November 19, 2023 by magnemoe