totm nov 2023 SpaceX Discussion Thread

[tater]

6 minutes ago, JoeSchmuckatelli said:

Just wondering, given the speed of the iteration's production vs launch attempts and lessons learned whether they can do much more besides software / easily accessible exterior equipment. 

Yeah, they are limited on production rate because they don't want to "fire for effect" on a design that might need rejiggering. They have loads more data than we see, obviously.

[Minmus Taster]

 

[darthgently]

1 hour ago, JoeSchmuckatelli said:

Spoke too soon 

Puerto Rico

 

 

https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd.it%2Fbooster-and-ship-weather-radar-debris-clouds-from-re-entry-v0-or8dmedi151c1.jpg%3Fwidth%3D1826%26format%3Dpjpg%26auto%3Dwebp%26s%3D84968b88c0b6af7d978b238a20a74ff1163f6322

 

(debris track) 

 

[AckSed]

2 hours ago, tater said:

One thing I notice with the drone view is the soot plume... does it vent CH4, or something else going on?

Something else: the exhaust is hot enough to make orange-brown nitrogen dioxide as it blasts the atmosphere. Very lean-burning internal combustion engines have the same trouble, expelling nitrogen oxides as the oxygen is consumed.

Although I also thought it was running fuel-rich at the start.

Edited November 18, 2023 by AckSed
Dupe

[lemon cup]

Just saw the footage and wanted to ask about one thing I noticed.

At launch, water deluge kicks in and the whole pad lights up, then you see dozens of visible rapid shockwaves emanating from the pad.

Does this mean the blast mitigation problem is still not solved? Was that a goal of this launch, or have they said they aren’t even worried about that yet?

[darthgently]

21 minutes ago, lemon cup said:

Just saw the footage and wanted to ask about one thing I noticed.

At launch, water deluge kicks in and the whole pad lights up, then you see dozens of visible rapid shockwaves emanating from the pad.

Does this mean the blast mitigation problem is still not solved? Was that a goal of this launch, or have they said they aren’t even worried about that yet?

The mitigation worked fine.  The exhaust is coming out at supersonic speeds so shockwaves are unavoidable, but not doing any real harm now.  

[Kerb24]

3 hours ago, JoeSchmuckatelli said:

Spoke too soon 

-video removed-

I'm concerned with how it seems that a large part of the ship survived flight termination (at least until re-entry). 

Edited November 18, 2023 by Kerb24

[tater]

2 minutes ago, Kerb24 said:

I'm concerned with how it seems that a large part of the ship survived flight termination (at least until re-entry). 

?

It all has to reenter, FTS doesn't vaporize steel.

[JoeSchmuckatelli]

13 minutes ago, Kerb24 said:

I'm concerned with how it seems that a large part of the ship survived flight termination (at least until re-entry). 

 

9 minutes ago, tater said:

?

It all has to reenter, FTS doesn't vaporize steel.

Smaller pieces burn up more easily, too.  So FTS really only needs to cut it into chunks. 

Whole thing was moving abt 24k kmh when it went boom - so all of the little pieces, especially not particularly shaped to reduce drag pieces, get nice and hot 

Edited November 18, 2023 by JoeSchmuckatelli

[AckSed]

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!

[Ultimate Steve]

Not that surprising, iirc the FTS is mainly intended to unzip the tanks to disperse the propellants, stop the vehicle from producing thrust, and create a small boom in the air instead of a big one on the ground. The front would likely survive this and I don't think it necessarily has to be a problem.

[tater]

35 minutes ago, Ultimate Steve said:

Not that surprising, iirc the FTS is mainly intended to unzip the tanks to disperse the propellants, stop the vehicle from producing thrust, and create a small boom in the air instead of a big one on the ground. The front would likely survive this and I don't think it necessarily has to be a problem.

FTS necessarily produces different results at 148km alt than 14.8 km. In the latter case, aero forces tears it to pieces. In the former, it's much bigger pieces. <shrug> FTS can't be designed to break a huge spacecraft into pieces no larger than X meters, the whole thing would have to be covered with explosives (creating new failure modes and dangers).

[tater]

 

[SunlitZelkova]

12 hours ago, Brotoro said:

First stage kept all engines running during boost, and second stage fired and burned quite a while… so it has already surpassed the N-1

I said “four flights with various levels of success but still failing” not “four flights with an unsuccessful first stage.”

It has yet to surpass N1 in that it hasn’t made it to orbit.

I believe there will be two more failures prior to a successful orbit. Successful Starship EDL is another question.

[Brotoro]

21 minutes ago, SunlitZelkova said:

I said “four flights with various levels of success but still failing” not “four flights with an unsuccessful first stage.”

It has yet to surpass N1 in that it hasn’t made it to orbit.

I believe there will be two more failures prior to a successful orbit. Successful Starship EDL is another question.

As I recall, the N1 never made it to staging. SH/SS has done that.

[SunlitZelkova]

22 minutes ago, Brotoro said:

As I recall, the N1 never made it to staging. SH/SS has done that.

I never said it would have failures identical to the N1. Just that it would be similar to the N1 in that some failure happens prior to reaching orbit.

[Pthigrivi]

Funny to see all the news stories calling this a big failure for Elon. I have made no secret here that Im not an Elon fan but this was a pretty solid 2nd launch. Really glad to see hot-staging work, deluge appears to be doing its job, even SS progressing nicely toward orbital velocity. Still some obvious concerns about Raptor reliability and  heat tiles but for this stage of the game it's good progress. I still hope Elon gets the help he needs but SS as a project seems on track. 

[tater]

The SH booster did not fail (as a booster). Failure of booster recovery will likely happen various ways for a long time—as it did for F9.

The N1 booster failed 4 times. So by flight 2 it has surpassed the N1 booster. The failure of SS (the upper stage, not the whole stack) has to be mapped to the failures of the upper stages of N1... which never got a chance to fail or not fail at all.

The booster issue might not be fixed for a few flights—assuming they want to use the existing couple that are already done. If Manley is right (seems a plausible explanation) then maybe they can fix the existing SHs enough to try boostback again—but they can always be expended.

Solving the SS failure depends on what the actual cause was. We'll have to wait and see on that—but it was very close to a nominal MECO.

Edited November 19, 2023 by tater

[Brotoro]

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.

[SunlitZelkova]

46 minutes ago, tater said:

The SH booster did not fail (as a booster). Failure of booster recovery will likely happen various ways for a long time—as it did for F9.

The N1 booster failed 4 times. So by flight 2 it has surpassed the N1 booster. The failure of SS (the upper stage, not the whole stack) has to be mapped to the failures of the upper stages of N1... which never got a chance to fail or not fail at all.

The booster issue might not be fixed for a few flights—assuming they want to use the existing couple that are already done. If Manley is right (seems a plausible explanation) then maybe they can fix the existing SHs enough to try boostback again—but they can always be expended.

Solving the SS failure depends on what the actual cause was. We'll have to wait and see on that—but it was very close to a nominal MECO.

Again, I never said the booster would have an identical test record to the N1. I said the whole vehicle would be similar in that it fails to get to orbit four times and then succeeds on the fifth (the fifth of the N1 has been deemed highly likely to succeed by both the project participants, men who cancelled it, and historians).

The N1 “booster” encompasses more than just the first stage. The other stages were static fired due to them being smaller and worked fine. In that sense it could be said that up until IFT-2, the N1 and Starship were at a similar level of completion in that the first stage had failed but the upper stages succeeded in other independent tests.

Now, Starship has surpassed N1 in that the first stage successfully flew.

But, it is also tied with N1 in that it hasn’t reached orbit.

My original statement didn’t have anything to do with a particular stage or trying to connect the dots between the different milestones. I’m simply saying until Starship reaches orbit, it is tied with the N1 in that regard (reaching orbit). And I think it will take two more tries before a successful orbit.

I’m just sharing my guess and don’t want it to be distorted. I’d be pleased if I was wrong about how many flights it takes to get to orbit.

[tater]

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.

[Exoscientist]

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

[darthgently]

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.

 

 

4 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.

Yeah, comparing apples to oranges mostly.  But still interesting in passing

5 hours ago, tater said:

Solving the SS failure depends on what the actual cause was. We'll have to wait and see on that—but it was very close to a nominal MECO.

This total loss of telemetry with no black box to recover seems unnecessary.  Some type of hardened data recovery element as part of a test payload really seems worthwhile at this point.  But I'm not an expert so am curious why this isn't "normal".  Is it a concern that, or even regulations regarding, the black box could be recovered by the wrong parties?

Edited November 19, 2023 by darthgently

[Mikki]

...I just want to mention from RL work with high pressure (1000+ bar liquids) machinery and containments that the raptor engines chamber combustion pressure surpasses 270 bar with all the known  issues of backpressure waves through the turbopump assembly. The turbopump rotors used to pump and pressurize the fuel and oxygen reach speeds of several hundred m/s (above the speed of sound at sea level) at their circumference and have a quite sturdy (and heavy) shaft attached to HD precision bearings and fittings.

From my (frozen) lawnchair i would guess that flipping SH at that momentum literally shredds some of the spinning pump assemblys on the edge of their intended specifications due to inertia of their own weight and absolute unwillingness to change their orientation in space while going around with  multitons of side- and topload on their bearings and pumphousings all together. (I cannot imagine that they stop the pumps and respin them again seconds later...)

The sovjets reached with the RD-180 a chamber pressure of slightly above 200  260 bar without flipping any pumps mid flight... 

I 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.

 

Edited November 19, 2023 by Mikki
260 bar

[mikegarrison]

7 hours ago, Pthigrivi said:

Funny to see all the news stories calling this a big failure for Elon.

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.

The goalposts are different for SpaceX -- among the SpaceX fans, anyway. But among the general population, don't expect the "whatever happens, we learn something" thing to be a popular viewpoint.

If the third try works, people will no doubt point to the first two and say, "See? Learning by experimentation works." If the third try fails, people will no doubt be saying, "Three times! This rocket is a disaster!"

At least they didn't have the same failures twice.

Edited November 19, 2023 by mikegarrison