totm nov 2023 SpaceX Discussion Thread

[CatastrophicFailure]

26 minutes ago, sevenperforce said:

Alternately, what if it looks like this?

I wouldn’t doubt it ends up looking like that, but the parts we’ve seen don’t seem right. They’re not wide enough and too tall and sharp. Isn’t a sharp edge into the airstream hotter on reentry than a rounded curve?

[magnemoe]

1 hour ago, CatastrophicFailure said:

Musk did mention that the legs would be mounted such that there’s room created for an extra few engines. Definitely looks more like chines or such, seems the wrong proportion for a fin. 

Lower stage / superheavy will have engines in the leg blisters. starship will have 3 surface an 3 vacuum engines unless this is changed again. 
You could put one leg on each side of the vacuum ones for 6 legs. 
Rotating legs is one option they rotate out, lots of option. Note that for the prototype, safety / reliability, ease if building is primary and performance losses not so much. 
 Yes they might add blisters to the airframe for stuff they add and want to verify, think falcon 9 style legs with the foot behind an cover. 

[sevenperforce]

Elon confirms six legs: two leeward, two windward, one under each fin. No word on shape.

 

[tater]

 

[tater]

 

 

 

[tater]

 

[kerbiloid]

Why not covered with teflon?

[Xd the great]

1 hour ago, kerbiloid said:

Why not covered with teflon?

Teflon decomposes at 800K?

[sh1pman]

5 hours ago, tater said:

 

With this mass ratio it can’t get to orbit without the booster, even with Vac Raptors. So it’s more accurate to call Mk1 and Mk2 suborbital prototypes.

[sevenperforce]

So those triangular things were definitely the transitional element from the top of the wing to the raceway. They are longer on one side than the other.

Although it is not yet light in Texas, you can see that at least one of them was installed last night.

2 hours ago, sh1pman said:

With this mass ratio it can’t get to orbit without the booster, even with Vac Raptors. So it’s more accurate to call Mk1 and Mk2 suborbital prototypes.

Starship isn't meant to reach orbit without the booster. This is still an orbital prototype, even if it will initially be flown without the booster and thus suborbitally.

It's as if they had used Columbia rather than Enterprise for the initial Shuttle flight tests.

Edited September 26, 2019 by sevenperforce
I was wrong, trick of light

[tater]

3 hours ago, sh1pman said:

With this mass ratio it can’t get to orbit without the booster, even with Vac Raptors. So it’s more accurate to call Mk1 and Mk2 suborbital prototypes.

They are stage 2 vehicles, they can still be orbital with a booster.

I'm wondering if the steel sheet thickness increased after the first fairing flopped over, increasing mass.

They are talking about total mass dropping over build iteration to 120 tons dry now.

The question is what's SH giving the stack velocity wise. F9 S1 gives the stage ~2.1km/s, leaving around 6500 m/s for S2. If SH does the same, that's a 90 ton payload to LEO. If SH can get it to 2.3 km/s, then they get 100t to LEO.

Musk has said before that F9 forces the second stage to do too much work, so the question is how fast can SH get the stack and still RTLS.

[sh1pman]

7 minutes ago, tater said:

They are stage 2 vehicles, they can still be orbital with a booster.

Even with the booster, it can barely get to orbit. ~9700 m/s dV for the full stack without any payload, and certainly not enough to return and land. It needs Vac Raptors to be of any use for orbital testing. It's a prototype of orbital vehicle, at best.

[ThatGuyWithALongUsername]

1 minute ago, sh1pman said:

Even with the booster, it can barely get to orbit. ~9700 m/s dV for the full stack without any payload, and certainly not enough to return and land. It needs Vac Raptors to be of any use for orbital testing. It's a prototype of orbital vehicle, at best.

So? What makes you think they won't just add those Raptors before going to orbit?

[tater]

He says the total stack is 5000 tons. If the dry mass for the whole stack was called 1850 tons---1500 for SS with a 100t payload + 350 tons for SH with some reserve---then the booster could possibly give the stack about 3400 m/s. It needs boostback and landing props (though I gave it 40 tons for landing above).

SS with 100 tons has ~6500 m/s dv, so it can make orbit with 100 tons payload at F9 booster stage sep velocities (~2km/s), and it can loft more if they recover downrange and stage closer to 3 km/s.

Edited September 26, 2019 by tater

[sh1pman]

1 minute ago, ThatGuyWithALongUsername said:

So? What makes you think they won't just add those Raptors before going to orbit?

Maybe they will, but I haven't heard anything about Mk1 getting Vac Raptors. 

[sevenperforce]

Remember that SL raptors have a significantly-increased vacuum thrust. It's not 330 s all the way up.

[sh1pman]

Just now, sevenperforce said:

Remember that SL raptors have a significantly-increased vacuum thrust. It's not 330 s all the way up.

I use 350s for SL Raptors. Dry mass at 200t, wet mass 1400t. That gives 6680m/s with no payload or 5300 m/s with 100t payload. If LEO requires 9300 m/s and landing dV is 300m/s, then SS will need to stage at 2900 m/s with no payload (doable) or 4300 m/s with 100t payload (impossible). That's why I said it needed Vac Raptors to be useful for orbital launches.

[sevenperforce]

They plugged the dorsal hole in Starship overnight:

 

Looks like a connector for fueling, potentially?

[tater]

38 minutes ago, sevenperforce said:

Remember that SL raptors have a significantly-increased vacuum thrust. It's not 330 s all the way up.

I was using 350 as the average for the whole thing, actually (Elon said something about them being 350 at SL in a tweet a couple weeks ago, BTW).

32 minutes ago, sh1pman said:

I use 350s for SL Raptors. Dry mass at 200t, wet mass 1400t. That gives 6680m/s with no payload or 5300 m/s with 100t payload. If LEO requires 9300 m/s and landing dV is 300m/s, then SS will need to stage at 2900 m/s with no payload (doable) or 4300 m/s with 100t payload (impossible). That's why I said it needed Vac Raptors to be useful for orbital launches.

Yeah, I was using the 120 ton later Mk. The prototypes don't need any payload.

[Elthy]

Two things:

What happened to Mk2? All current updates are about Mk1 in Texas...

I realy wonder if they will be able to lower the dry mass from 200t to the proposed 85tons from the 2017 presentation. They need top add lifesupport and other interior stuff with that budget, too, it seems realy optimistic...

[Rakaydos]

4 minutes ago, Elthy said:

Two things:

What happened to Mk2? All current updates are about Mk1 in Texas...

I realy wonder if they will be able to lower the dry mass from 200t to the proposed 85tons from the 2017 presentation. They need top add lifesupport and other interior stuff with that budget, too, it seems realy optimistic...

Rumor is that workforce was transferred to texas to help meet the presentation deadline. Mk 2 wil speed back up once the workers go back to florida.

It sounds like they are aiming for 120 tons for the mk 4-5, so 85 tons will me, like, mk 10 or later.

[Ultimate Steve]

This is a concerning amount of mass growth. I know this is a prototype, but including the word "orbital" is a stretch as evidenced above. If it could do 150t maximum to orbit and 100t to a useful orbit and have enough to return, and Mk1 is 200 tons (might be more), assuming the 150 ton number was with an 85 ton dry mass, then it's lost 115 tons of capability, giving it 35 tons to orbit or -15 tons to a useful orbit.

[tater]

31 minutes ago, Ultimate Steve said:

This is a concerning amount of mass growth. I know this is a prototype, but including the word "orbital" is a stretch as evidenced above. If it could do 150t maximum to orbit and 100t to a useful orbit and have enough to return, and Mk1 is 200 tons (might be more), assuming the 150 ton number was with an 85 ton dry mass, then it's lost 115 tons of capability, giving it 35 tons to orbit or -15 tons to a useful orbit.

Even the 200t version can get a substantial payload to LEO with a ASDS landing for SH. Probably around 30t with SL engines, and 60t with vacuum engines. I'd assume they will shave mass with each iteration. I have to assume their current production method is cheap, but they pay with mass. They can make finer structures with proper tooling, support--a VAB-like structure so it doesn't have to survive constant wind, etc)

[Wjolcz]

Tbh even 50t to LEO with full reusability is a win imo

[sevenperforce]

They have tack-welded the chines on the windward side of the starboard aft fin.

15 minutes ago, Ultimate Steve said:

This is a concerning amount of mass growth. I know this is a prototype, but including the word "orbital" is a stretch as evidenced above. If it could do 150t maximum to orbit and 100t to a useful orbit and have enough to return, and Mk1 is 200 tons (might be more), assuming the 150 ton number was with an 85 ton dry mass, then it's lost 115 tons of capability, giving it 35 tons to orbit or -15 tons to a useful orbit.

This is a battleship version. Way heavier than it needs to be. And it can still get to an orbit and return, even if it's not a useful orbit. That's what prototypes are for.