totm nov 2023 SpaceX Discussion Thread

[magnemoe]

34 minutes ago, sevenperforce said:

The payload was just very heavy. At 6.6 tonnes, first-stage recovery would have necessitated an orbit with an apogee lower than a proper GTO (compare the Galaxy 33/34 mission back in October, where the 7.4-tonne payload could only be lofted to around 20,000 km; the same was true for SXM-7 and SXM-8). 

Usually, GTO launches have an apogee even higher than the 35,800 km of GEO. A higher apogee allows for a bi-elliptic transfer, which saves propellant on the payload and thus increases the lifetime of the satellite.

The customer paid extra to expend the booster

Thanks, that explains it. 

17 minutes ago, darthgently said:

Quite a few F9 video streamed show this effect, but you have to find one with an extended 2nd stage burn and not bail out on the video after meco, 2nd stage ign like most do, ha ha.  I haven't noticed if it always happens but I think I saw it last with the recent FH launch

Don't think its outside design limit, falcon heavy second stage has extended flight time as it can do an circulation burn into GEO. You don't want to run the tanks dry as the turbo pump might blow up. 

[darthgently]

32 minutes ago, magnemoe said:

Thanks, that explains it. 

Don't think its outside design limit, falcon heavy second stage has extended flight time as it can do an circulation burn into GEO. You don't want to run the tanks dry as the turbo pump might blow up. 

Let me rephrase the question.

What causes the green one can see in the plume of long running Merlin vacuum engines?

[sevenperforce]

2 hours ago, darthgently said:

What causes the green one can see in the plume of long running Merlin vacuum engines?

You'd have to give an example; I don't think I've seen it.

3 hours ago, darthgently said:

I haven't noticed if it always happens but I think I saw it last with the recent FH launch

That might be difficult since the recent FH didn't have any views of the upper stage after staging.

[darthgently]

1 hour ago, sevenperforce said:

That might be difficult since the recent FH didn't have any views of the upper stage after staging.

You are correct. It was a recent launch though, I'll find a vid link and time offset.  I recall it was non-Starlink

[mikegarrison]

This vaguely reminds me of back when I used to work for an engine company. I was told by an older engineer that they had bid on a contract to build some small engines for a cruise missile. The design they came up with would run for about 1000 hours or something like that. They lost the contract to another company whose design would only last for less than 100 hours, but was cheaper. Of course, this was for a cruise missile, so....

[Beccab]

 

Static fire preps are starting up

[Beccab]

Looks like they're going for it

I still expect a spin prime round before they go for the static tho

 

Siren!

[tater]

Static fire

[Pthigrivi]

Woo big flamey!

[tater]

Literally not been in front of the computer for about an hour, switched to starbase tab, static fire, lol.

[Beccab]

WOW! If it was at higher than 90% throttle overall and with 16 engines, that was the most powerful static fire in history*

*because the N1, despite having more thrust than 16 raptors at liftoff, never did a static

[tater]

 

[CastleKSide]

Looks like progress is being made nice

[sevenperforce]

So much sheer kablooey

If those 14 engines are at full throttle, that's about 50% more thrust than Falcon Heavy and almost as much thrust (though not quite) as SLS block 1.

[tater]

1 hour ago, sevenperforce said:

If those 14 engines are at full throttle, that's about 50% more thrust than Falcon Heavy and almost as much thrust (though not quite) as SLS block 1.

Yeah, the 20 outer ones will beat SLS in thrust if they do that test. Completely nuts.

[RCgothic]

It's 20 for N1 I believe. 16 for SLS?

Fewer if you count power as thrust * exhaust velocity.

I believe the pad needs some sort of flame diverter upgrade though. Apparently there was concrete debris raining down everywhere after the test.

[Beccab]

 

[RCgothic]

I'd hope either of the next two firings is with 33 engines. Wouldn't really want to go into a launch attempt without having fired them all at once!

I've heard that a full LOX tank is sufficient mass to hold down a full 33 engine firing though, so maybe the autogenous pressurisation test has a decent chance of going full send and firing all 33.

[Beccab]

7 minutes ago, RCgothic said:

I'd hope either of the next two firings is with 33 engines. Wouldn't really want to go into a launch attempt without having fired them all at once!

I've heard that a full LOX tank is sufficient mass to hold down a full 33 engine firing though, so maybe the autogenous pressurisation test has a decent chance of going full send and firing all 33.

Most definitely we're going to see a 33 engines one, yeah

 

Interesting to note that both tanks on B7 were nearly completely empty yesterday, so it was also a stress test for the hold down clamps; we can now be sure that holding it down with more fuel and 33 should not be an issue

[RCgothic]

Needs ~3400t of propellant adding for an additional 19 engines at full throttle so that the force in the clamps we saw this time isn't exceeded in that case.

~1750t if the extra engines are fired at 40% throttle.

 

[sevenperforce]

9 hours ago, RCgothic said:

I believe the pad needs some sort of flame diverter upgrade though. Apparently there was concrete debris raining down everywhere after the test.

Yikes. Source?

7 hours ago, Beccab said:

 

So, two more static fires, removal from the launch mount to make minor repairs and updates, three more static fires, some on-pad work, another static fire, and then orbital launch attempt.

[RCgothic]

18 minutes ago, sevenperforce said:

Yikes. Source?

 

 

[sevenperforce]

Here's a comparison for 14 and 33 Raptor 2s at minimum thrust and at full thrust.

[RCgothic]

That doesn't seem right?

14x2.3MN = 32.2MN, not over 40?

[sevenperforce]

31 minutes ago, RCgothic said:

That doesn't seem right?

14x2.3MN = 32.2MN, not over 40?

Oh, shoot, Excel stacked min on top of max rather than showing them on the same scale. My bad.

That's corrected.