totm nov 2023 SpaceX Discussion Thread

[Nuke]

2 minutes ago, CatastrophicFailure said:

Paige, No! ... 

it was a hemispherical array of srbs pointing inward with the command chair placed at the epicenter of thrust. 

Edited August 26, 2023 by Nuke

[Brotoro]

That Falcon 9 booster sure was coming in hot and squirrelly. I'd want to check that one over really well before reusing it.

[tater]

41 minutes ago, Nuke said:

they must play kerbal like i do, i cant remember the last time i killed a kerbal, unless it was on purpose. one paige kerman comes to mind. 

Yeah, I was never one to wantonly kill kerbals—even playing with life support I made sure they had contingency supplies, etc.

[Exoscientist]

8 hours ago, tater said:

They have no idea what they are doing, they're just like people blowing up stuff in KSP, they have no models where 50% tests give them useful data.

Later today:

Also them (tomorrow):

 

 Actually, I think they should go back to the approach they took with the Falcon 9. 

 First, make a smaller rocket with, say, 9 Raptors such as the Starship but used as the booster, with a smaller stage, call it a mini-Starship, as the upper stage. Test the heck out this vehicle at full up, full thrust, and full flight duration static tests. Just they like did and still do for the Falcon 9, before they do a test launch. 

 Only after multiple full static tests where all engines successfully pass do they send this up for a test flight. Such a two-stage rocket could do 100 tons to LEO. That is sufficient to do single-launch lunar and Mars missions.

 Now, make money on that rocket made from the start to be reusable. Fly that rocket very many times all the while making profit with it. THEN after flying so many times you accumulated like over a 1,000 successful firings of the Raptor on full actual, operational flights then form your superheavy lift vehicle by using triple cores, like what happened with the Falcon Heavy. That is if you still want the superheavy lift vehicle. My guess is you’ll be making money on the smaller version and be able even to make both single-launch Moon and Mars missions with it, there will be little incentive to continue on with the larger vehicle.

  See:

The Missed Lesson of the Falcon Heavy.
https://exoscientist.blogspot.com/2023/02/the-missed-lesson-of-falcon-heavy.html

 

  Bob Clark

Edited August 26, 2023 by Exoscientist

[tater]

14 minutes ago, Exoscientist said:

 First, make a smaller rocket with, say, 9 Raptors such as the Starship but used as the booster, with a smaller stage, call it a mini-Starship, as the upper stage. Test the heck out this vehicle at full up, full thrust, and full flight duration static tests. Just they like did and still do for the Falcon 9, before they do a test launch. 

Literally against the entire point of Starship.

Launch Falcon 9s for decades, or slightly bigger methalox version, die with humanity progressing no farther than we have in the last 50 years (those of us around Elon's age—the younger one then hope for a new Elon in 40 years to actually try something different).

We could be having this discussion on sci.space back in the day about ways to leverage existing stages like Centaur for cislunar/Mars/etc—same ^%$#^%#! stages as now!—using Shuttle. Then 40 years pass and we have exactly nothing to show for it.

 

Edited August 26, 2023 by tater

[Nuke]

the best analogue for elon musk is howard hughes. you need someone who is a little bit nuts and obsessed about one thing, but good at many. such an individual comes around about at 60-80 year intervals. 

Edited August 26, 2023 by Nuke

[tater]

https://www.spacex.com/follow-dragon/index.html

^^^this is cool, shows orbital path of both vehicles.

 

1 hour ago, Brotoro said:

That Falcon 9 booster sure was coming in hot and squirrelly. I'd want to check that one over really well before reusing it.

Looked OK to me. I looked at the stream just now, and maybe it's the ability to see so many reference points (lights in FL)? Dunno, might have to compare another night LZ-1

[mikegarrison]

13 hours ago, RCgothic said:

The new foundation isn't going to fail again. It's over two meters thick reinforced concrete capped with steel and with many more support pilings than previously.

Even absent the deluge system it wouldn't be going anywhere.

That's what they thought the first time....

[magnemoe]

16 minutes ago, tater said:

Literally against the entire point of Starship.

Launch Falcon 9s for decades, or slightly bigger methalox version, die with humanity progressing no farther than we have in the last 50 years (those of us around Elon's age—the younger one then hope for a new Elon in 40 years to actually try something different).

We could be having this discussion on sci.space back in the day about ways to leverage existing stages like Centaur for cislunar/Mars/etc—same ^%$#^%#! stages as now!—using Shuttle. Then 40 years pass and we have exactly nothing to show for it.

This, part of the purpose of Starship is that its so large and cheap to use it will redefine spaceflights. 

Yes a bit skeptically to some options like trying to catch super heavy on first landing. Not seen an plan to recover Starship. As in there to do it. Starbase and they have to overfly Mexico at most elevations and Texas else. I thought converted oil rigs could be an catch location but they sold them. 
And the lack of an abort system who will make it much harder to get NASA to accept it. At least plan for it in case they need it. Now I say its probably that they looks into it. 
Moving both the fuel and oxidizer tanks to the nose makes it easier. 
But starship landing is still an issue. 
 

[mikegarrison]

8 hours ago, tater said:

They have no idea what they are doing, they're just like people blowing up stuff in KSP, they have no models where 50% tests give them useful data.

That level of sarcasm is pretty strongly undercut by the very public failure of their reinforced pad the first time.

I'm sure they will get it right eventually, but this rush to defend their untested (at full power) new pad design, after the failure of the previous untested (at full power) new pad design, and after the failure of the initial pad design, seems pretty defensive.

Edited August 26, 2023 by mikegarrison

[darthgently]

8 minutes ago, magnemoe said:

This, part of the purpose of Starship is that its so large and cheap to use it will redefine spaceflights. 

Yes a bit skeptically to some options like trying to catch super heavy on first landing. Not seen an plan to recover Starship. As in there to do it. Starbase and they have to overfly Mexico at most elevations and Texas else. I thought converted oil rigs could be an catch location but they sold them. 
And the lack of an abort system who will make it much harder to get NASA to accept it. At least plan for it in case they need it. Now I say its probably that they looks into it. 
Moving both the fuel and oxidizer tanks to the nose makes it easier. 
But starship landing is still an issue. 
 

I'm guessing crew starship launches and landings are not a priority given F9 + crew dragon can do that taxi work to and from orbiting starships after refueling without crew present etc

[tater]

18 minutes ago, mikegarrison said:

That level of sarcasm is pretty strongly undercut by the very public failure of their reinforced pad the first time.

I'm sure they will get it right eventually, but this rush to defend their untested (at full power) new pad design, after the failure of the previous untested (at full power) new pad design, and after the failure of the initial pad design, seems pretty defensive.

Will they do another test at a similar (or greater) thrust level? No idea. Course no one here on this forum knows that.

Is the vehicle stacked on the pad for launch? No. Will SpaceX do a test at >50% before launch? I have no idea—nor does anyone else not at SpaceX.

I can only assume they are looking at the 50% test data, and deciding how it comports with their modeling. I'm unsure if a >50% static fire is something that is possible without Starship on top (depends on hold downs I would expect). So maybe we have to wait for a full stack, then a static fire. Given that such a stack is just as dangerous as a launch, the question becomes one of where the risk/reward is.

Regarding the old pad—they were expecting to add the deluge anyway. I think they were certainly surprised by the extent of the damage, and a full-power static fire would likely have created all the same damage—with a fueled rocket still sitting on the pad. There are some failure mode trade offs for full-thrust static fires here vs liftoff I think. A pad failure at full thrust creates the possibility of FOD/GSE interactions that might be concerning. I have no idea what the exact trade offs are, but it seems like they must be there.

I'm not defending their pad being untested at 100%, I just know what I don't know. I don't know what their modeling looks like—though I assume they have people doing that (maybe they don't?).  At some level I have to assume that they are making a some effort to understand what's going on.

Edited August 26, 2023 by tater

[mikegarrison]

36 minutes ago, tater said:

At some level I have to assume that they are making a some effort to understand what's going on.

Of course. That's why they are testing.

But it's pretty annoying to see people in this forum apparently smugly saying "SpaceX knows what they are doing" when the observed reality suggests that they do *not* actually know what they are doing. Yes, that's why you test. I have no problem with test failures (other than easily predicted, dangerous but unmitigated test failures). I have a problem with the sarcasm levels.

Sometimes when you try something new that goes against all the conventional wisdom, you find out that the conventional wisdom no longer applies (or maybe even never did). But sometimes you find out that the conventional wisdom (like water deluge) was was hard-won and there for a reason.

 

Edited August 26, 2023 by mikegarrison

[tater]

10 minutes ago, mikegarrison said:

But it's pretty annoying to see people in this forum apparently smugly saying "SpaceX knows what they are doing" when the observed reality suggests that they do *not* actually know what they are doing. Yes, that's why you test. I have no problem with test failures (other than easily predicted, dangerous but unmitigated test failures). I have a problem with the sarcasm levels.

You need to also look at what the response was actually to. Arianespace is clueless, they need to do what they are not doing. SLS needs to add alternate stages—either from another US company, or from Arianespace. FAA approves test launches that literally include a full stack explosion/deflagration, but an event that is not even in the same ballpark than that is then proof FAA needs to re-eval, etc, ad nauseum.

 

I'm perfectly fine with wondering what the actual problems are (Raptor problems, or 33 Raptors at once?).

[mikegarrison]

11 hours ago, Exoscientist said:

Sorry, SpaceX used up their “because SpaceX says” so cred, by their no flame trench, poor FTS, bad stage separation mistakes. If they think this water deluge system will work at 100% thrust, then prove it by actually testing it at full thrust.

Testing it first at half thrust is the prudent choice. If it fails at half thrust, then they know it will fail at full thrust, without the danger and expense of a full thrust test. If it does not fail at half thrust, then they can move on to a full thrust test later, which we all know they are going to do in the flight test if not before.

[magnemoe]

35 minutes ago, tater said:

Will they do another test at a similar (or greater) thrust level? No idea. Course no one here on this forum knows that.

Is the vehicle stacked on the pad for launch? No. Will SpaceX do a test at >50% before launch? I have no idea—nor does anyone else not at SpaceX.

I can only assume they are looking at the 50% test data, and deciding how it comports with their modeling. I'm unsure if a >50% static fire is something that is possible without Starship on top (depends on hold downs I would expect). So maybe we have to wait for a full stack, then a static fire. Given that such a stack is just as dangerous as a launch, the question becomes one of where the risk/reward is.

Regarding the old pad—they were expecting to add the deluge anyway. I think they were certainly surprised by the extent of the damage, and a full-power static fire would likely have created all the same damage—with a fueled rocket still sitting on the pad. There are some failure mode trade offs for full-thrust static fires here vs liftoff I think. A pad failure at full thrust creates the possibility of FOD/GSE interactions that might be concerning. I have no idea what the exact trade offs are, but it seems like they must be there.

I'm not defending their pad being untested at 100%, I just know what I don't know. I don't know what their modeling looks like—though I assume they have people doing that (maybe they don't?).  At some level I have to assume that they are making a some effort to understand what's going on.

I agree, they need to add an fully fueled Starship on top as the hold down clamps probably require it.
As I see it the only problem is the engine star and ramp up and fails. 

[darthgently]

22 minutes ago, magnemoe said:

I agree, they need to add an fully fueled Starship on top as the hold down clamps probably require it.
As I see it the only problem is the engine star and ramp up and fails. 

This is the line of thought I'd went down also.  Then I tried imagining SpaceX having a fully-fueled booster+SS stack to do proper full thrust test of the deluge and *not* simply doing a second launch and stage separation test at that point as everything would be in place.  It was hard to imagine this.  No one knows, this is just my wetware LLM trained on previous SpaceX decisions spitting out a prediction

[RCgothic]

Space is hard and even people who know what they're doing won't get it right 100% of the time.

Has there ever in history been a case of rocket thrust so great it breaks a foundation before now? No. That was pretty unexpected. Have they fixed that problem? By all observations they've taken the problem seriously and rebuilt the pad so that won't happen again.

[mikegarrison]

11 minutes ago, RCgothic said:

Has there ever in history been a case of rocket thrust so great it breaks a foundation before now? No.

Pretty certain the answer must be yes, or otherwise why all the designs with flame trenches and water deluge? I would guess those designs came about due to experience.

[Nuke]

6 hours ago, tater said:

Yeah, I was never one to wantonly kill kerbals—even playing with life support I made sure they had contingency supplies, etc.

i sometimes find my lack of empathy disturbing. sometimes.

[Nuke]

2 hours ago, RCgothic said:

Space is hard and even people who know what they're doing won't get it right 100% of the time.

Has there ever in history been a case of rocket thrust so great it breaks a foundation before now? No. That was pretty unexpected. Have they fixed that problem? By all observations they've taken the problem seriously and rebuilt the pad so that won't happen again.

aviation has gotten to the level of safety it has by studying every incident in extreme detail. they didn't do it by having a moratorium on air travel until the technology was "proven". they let people fly and be flown and got better at it with each new aircraft and various procedures and systems. 

Edited August 27, 2023 by Nuke

[RCgothic]

6 hours ago, mikegarrison said:

Pretty certain the answer must be yes, or otherwise why all the designs with flame trenches and water deluge? I would guess those designs came about due to experience.

Flame trenches are primarily to direct the exhaust away from the vehicle and to prevent damage to the vehicle. 

Although there are examples of the refractory brick lining of flame trenches being damaged by rocket exhausts, that's an example of the sort of scouring effect SpaceX were expecting and prepared to put up with for one launch.

The Russians don't to my knowledge use deluge systems, even for the large rockets N1 and Energia. The pads at LC39 only had a minimal system for Saturn V, and it was upgraded for shuttle because of damage to the vehicle. The exhaust didn't seriously threaten the flame trench which was built for Nova, and the OLM at Boca Chica is taller than the flame trenches at LC-39 by a long way.

A large rocket had never before now cracked and excavated its own launch pad foundation through weight of thrust.

[Exoscientist]

 I am dismayed by the level of unreliability of the Raptor. In this latest static fire test two of the Raptors had to be shut  down for only a 5 second test and 50% thrust level. But this is the same number that had to be shut down in the earlier static fire test prior to a test launch for only a 5 second test at 50% thrust level. Does anyone really believe the Raptor is more reliable than before? 

 At this point I don’t think anyone doubts that if there is another test launch in like two weeks there will be engine failures like before. The only question is how many. Will it this time be only four or six instead of eight? Or this time will it be 10 or 12 or more instead of eight? Nobody not even SpaceX knows the answer to that.

  Bob Clark

[tater]

What we don't know regarding the engines is what if any problems are attributed by SpaceX to be GSE related (the outer engines are fed from the OLM for startup), what problems they think are cluster related (engine/engine interactions), and what issues are unknowns.

They test fire singleton engines a great deal at McGreggor, so I have to imagine it's more likely to be GSE/cluster related.

 

[tater]

Crew aboard ISS now.