totm nov 2023 SpaceX Discussion Thread

[Lewie]

4 minutes ago, tater said:

If you look at the underside images of SN20 you will see 6 slots. On B4 there are 3 tabs with a rod, presumably a latch on SS grabs those. There are likely 3 tabs in the other 3 on SS such that they can be deployed for a 180 degree rotation rail to tail docking for prop transfer.

Ohh, thanks!! It’s crazy...it’s just SO BIG!!

5 minutes ago, cubinator said:

Elon said that they are gonna tilt up the booster just before shutdown and use the angular momentum to separate the Starship and start the boostback, much like the Starlinks.

The booster will use the normal venting of the gas inside the main tanks as RCS. It's about 6 bar and would work about as well as dedicated thrusters. Dragon thrusters are about 8-9 bar.

Holy.....

are they trying to make this as crazy as possible??

Did Elon confirm hot gas thrusters are out of the equation?

[cubinator]

12 minutes ago, Lewie said:

Holy.....

are they trying to make this as crazy as possible??

Did Elon confirm hot gas thrusters are out of the equation?

Yup, hot thrusters are out, on the booster at least. It's just strategic venting. And, on Tim's suggestion, Elon said they might try that on the ship too.

[Lewie]

58 minutes ago, cubinator said:

Yup, hot thrusters are out, on the booster at least. It's just strategic venting. And, on Tim's suggestion, Elon said they might try that on the ship too.

Man, that’s kind of a bummer! Would have been neat to see ‘em in action. Another case of the best part is no part, or probs too complicated/unnecessary?

[tater]

I was misremembering rods, but the tabs have an undercut for a latching mechanism.

Oh, and:

 

[mikegarrison]

3 hours ago, RCgothic said:

It actually makes you wonder how they managed to add an engine and two booster segments to SLS and still omehow end up with 15t fewer to LEO.

Engine weight. We're counting the engines as part of the payload weight for the orbiter, but we're not counting the engines as part of the payload weight for SLS.

[CatastrophicFailure]

2 hours ago, Lewie said:

I’m rather bummed, I was at work for the entire stacking!! You lucky ducks got to see t live! 

If it’s any consolation, they stacked AND unstacked it all while I was sleeping. 

[tater]

5 minutes ago, mikegarrison said:

Engine weight. We're counting the engines as part of the payload weight for the orbiter, but we're not counting the engines as part of the payload weight for SLS.

Heck, the whole sustainer core.

Like the Shuttle with the External Tank, the core could make it to orbit, it's left with a low perigee for disposal. I suppose if wet labs were a thing, they could leave it in orbit. Or send a ship to uninstall the engines and take them back.

Since this is the SpaceX thread... A SS with crew could salvage the 4 SSMEs, and maybe leave a small remotely operated deorbiting vehicle attached to it. At ~$100M each, it would be worth it, lol. Get SLS some "SMART" reuse.

[mikegarrison]

It's not that any of these methodologies for calculating payload mass to LEO are wrong per se -- it's just that some of them make sense with some kinds of architectures and others make sense with different kinds of architectures. Just because they all have the units of kg does not mean they are all apples being compared to apples.

@tater's proposed definition of "payload = stuff in orbit that you want to use or keep" mostly makes sense. That would be a reasonable definition of the payload to LEO of the booster.

[JoeSchmuckatelli]

In @tater's photo post above, you can see the support structure for one of the grid fins (2d photo).  Comparing it to the pics with the people - it looks like the ring is about 5' in diameter.

Is the housing shown large enough to contain the actuators for the grid fins - or are the motors likely to be below what we can see? 

[RCgothic]

14 hours ago, tater said:

They are counting not Starship. 
 

Cargo, or more likely, residual propellants.

If the dry mass is 100t, 100t payload means 200t got to LEO.

Actually that’s not far off Shuttle if the orbiter was 110t. Add in 25t cargo, and technically it could have taken the empty main tank as well…

 

I very much doubt the shuttle could have taken the ET and a 25t payload to LEO. Pretty sure it would be either or.

[tater]

4 minutes ago, RCgothic said:

I very much doubt the shuttle could have taken the ET and a 25t payload to LEO. Pretty sure it would be either or.

Dunno, the normal launch trajectory was designed for disposal, seems plausible with a trajectory optimized for “not disposal” might buy a little margin. At the very least it gets to LEO with something between orbiter+tank and orbiter+tank+25t, how many tons of cargo it loses? 

Tank was separated at just a few hundred m/s below orbital velocity.

[sevenperforce]

2 hours ago, JoeSchmuckatelli said:

In @tater's photo post above, you can see the support structure for one of the grid fins (2d photo).  Comparing it to the pics with the people - it looks like the ring is about 5' in diameter.

Is the housing shown large enough to contain the actuators for the grid fins - or are the motors likely to be below what we can see? 

The actuators are inside.

1 hour ago, tater said:

Dunno, the normal launch trajectory was designed for disposal, seems plausible with a trajectory optimized for “not disposal” might buy a little margin. At the very least it gets to LEO with something between orbiter+tank and orbiter+tank+25t, how many tons of cargo it loses? 

Tank was separated at just a few hundred m/s below orbital velocity.

I am with @RCgothic on this one. IIRC they seriously considered the wet lab proposal but found that they would essentially be taking the tank to LEO as a payload. They would need an adapter to convert the tank into a workshop, which would take up the additional payload capacity and be located in a fairing on the nose of the external tank.

[tater]

 

26 minutes ago, sevenperforce said:

I am with @RCgothic on this one. IIRC they seriously considered the wet lab proposal but found that they would essentially be taking the tank to LEO as a payload. They would need an adapter to convert the tank into a workshop, which would take up the additional payload capacity and be located in a fairing on the nose of the external tank.

Looks like the OMS-2 burns were under 100 fps much of the time.

I think it is more than plausible that Shuttle could take the ET and some cargo in the payload bay all the way to some stable orbit. Doesn't have to be ISS, just, "makes it around the Earth at least once."

[magnemoe]

38 minutes ago, sevenperforce said:

The actuators are inside.

I am with @RCgothic on this one. IIRC they seriously considered the wet lab proposal but found that they would essentially be taking the tank to LEO as a payload. They would need an adapter to convert the tank into a workshop, which would take up the additional payload capacity and be located in a fairing on the nose of the external tank.

This, also you don't want steel hab modules because of radiation as I understand. 
Wet workshop become more interesting on moon or mars, you will cover it with regolit so radiation and insulation is much less an issue. Here the tank can land under own power and bring cargo, then getting laid down in an ditch.
Don't see it used as an habitation module more like an hangar or storage, cut away the top dome and its an second bulkhead with an huge hatch, you have smaller hatches you can access the same way. it came with an floor and some other stuff like overhead rails for an crane. 

[Beccab]

46 minutes ago, tater said:

 

Looks like the OMS-2 burns were under 100 fps much of the time.

I think it is more than plausible that Shuttle could take the ET and some cargo in the payload bay all the way to some stable orbit. Doesn't have to be ISS, just, "makes it around the Earth at least once."

Important parts:

• In orbit refueling might be side to side, not "butt to butt". Not currently working on refueling. Delayed until it's actually needed (for Moon/Mars)

• Raptor v2 will be much more streamlined and cleaner looking.

• Work on the payload doors is stopped for now. All focus is on getting to orbit.

• First few (Musk says 10) Starships probably won't be reflown, or only once or twice. Rapid iteration and improvements for the foreseeable future.

• Dry mass of S20 hopefully around 100 tonnes. They needed to measure it to actually know.

• Starship will be fueled via quick disconnect arm. Saves mass on booster.

• The tiny arms next to the grid fins are indeed intended for the catch mechanism.

• Launch tower will have additional arms for stabilizing the booster during stacking with "Mechazilla" (the primary catch/lift arms)

• First few catch attempts might easily go wrong. They'll get it working eventually.

• They built a first "new and improved" nosecone with stretched full-height sections instead of 3 rows of plates.

• Starship will launch from the Cape as well. The florida facility is later planned to become a full, Boca Chica-like starship factory to support those

• First launch primary goal is just getting to orbit. Not blowing up on launch is already a success.

• Where did the Shuttle go wrong? => No room for iteration due to humans being on board for every launch. Lead to stagnation and fear of changing anything.
  
  Ready for part three?
  
  Edit: also look at this, it is very relevant https://everydayastronaut.com/starbase-tour-and-interview-with-elon-musk/

Edited August 7, 2021 by Beccab

[tater]

Shuttle could take a normal cargo mass (20-25t) to a 185km circular orbit. The upper range (95% confidence) is 32t per the launch vehicle performance calculator. The Super lightweight ET was ~26.5t.

Chandra was the heaviest payload at over 22t, and the Orbiter flew to 280km alt. I assume that at a lower alt, and trajectory optimized for not disposing the 26.5t tank, Shuttle could certainly have brought the tank to some parking orbit. How long it could remain, or what the max alt would be is another story.

I was NOT suggesting wet workshops, I don't think they are super useful personally, the fitting out, etc is too complex might as well make a station—the point was about the total mass a vehicle could take—including tanks, etc if someone had some reason for that—to orbit. Comparisons otherwise being odd—counting just cargo or propellants, but not counting the Shuttle Orbiter (or Starship itself)

[Meecrob]

15 hours ago, Lewie said:

Yes, I am a teen. No, I do not think smoking weed is a good idea. Cool? Heck no! Is it a ‘meme number?’

you betcha!

Do I think a bunch of pot heads built starship? ‘Course not. 

I’m just saying it’s a ‘funny number’ y’know...Elon IS a meme lord...

Bingo

but ya

I’m rather bummed, I was at work for the entire stacking!! You lucky ducks got to see t live! 

I think one of the things that really impresses me about SS/SH is the decoupling...how on Earth did those SpaceX engineers devise a system to hold a 1200 ton Starship on a booster?? (Seriously does anyone know anything about this?) I didn’t finish watching Tim Dodd’s interview with Elon, so....whoops. Gonna have to do that soon! 

Haha, I'm glad you made this post...I woke up and read what I wrote, and wish I could delete it. Nobody here needs a lecture...least of which from me. Let me have an old man moment and ignore me. I'll shut up.

[DDE]

Milk stool?

[JoeSchmuckatelli]

Working from a cherry picker at that height has to be...

Exciting 

[magnemoe]

1 hour ago, Beccab said:

Important parts:

• In orbit refueling might be side to side, not "butt to butt". Not currently working on refueling. Delayed until it's actually needed (for Moon/Mars)

• Raptor v2 will be much more streamlined and cleaner looking.

• Work on the payload doors is stopped for now. All focus is on getting to orbit.

• First few (Musk says 10) Starships probably won't be reflown, or only once or twice. Rapid iteration and improvements for the foreseeable future.

• Dry mass of S20 hopefully around 100 tonnes. They needed to measure it to actually know.

• Starship will be fueled via quick disconnect arm. Saves mass on booster.

• The tiny arms next to the grid fins are indeed intended for the catch mechanism.

• Launch tower will have additional arms for stabilizing the booster during stacking with "Mechazilla" (the primary catch/lift arms)

• First few catch attempts might easily go wrong. They'll get it working eventually.

• They built a first "new and improved" nosecone with stretched full-height sections instead of 3 rows of plates.

• Starship will launch from the Cape as well. The florida facility is later planned to become a full, Boca Chica-like starship factory to support those

• First launch primary goal is just getting to orbit. Not blowing up on launch is already a success.

• Where did the Shuttle go wrong? => No room for iteration due to humans being on board for every launch. Lead to stagnation and fear of changing anything.
  
  Ready for part three?
  
  Edit: also look at this, it is very relevant https://everydayastronaut.com/starbase-tour-and-interview-with-elon-musk/

I say its very unlikely they move to sideway docking for fuel. Bottom is pretty solid and all the engines are protected by the shield. It also has clamps there.
They will load propellant at ground from the side rather than trough the first stage but orbital refueling can not use that system anyway at least not on the extending (male plug) side. starship has the clamp lock down anyway you want some clamps for the male but this can simply be holes in the superheavy or something you extend its for micro gravity anyway. 
RCS to settle fuel, you use pressure difrence in tanks to move it. 

Cargo bay doors, makes sense, now they might want to deploy starlinks with it if reentry and landing is an hard problem but reaching orbit is easy. 

To refly starship they need to land them so they can be recovered in the first place and harder than just landing them who is easier to find an spot there you can recover. 

My guess is that the tiny hard points is the aspiration goal. Catch with grind fins should work but might easy damage them. 

Extra arms for this makes sense more so if they lift starship with the arm. 

Shuttle was also not an design who was easy to change, worse they build them and shut down the production line. 
No not an assembly line but factories making part for it. 
It had been pretty easy to let the shuttle fly unmanned but then it was relevant the launches who could be unmanned used other rockets. 
And yes today its easier to do changes and starship is less complex in structure. 

[Meecrob]

37 minutes ago, JoeSchmuckatelli said:

Working from a cherry picker at that height has to be...

Exciting 

Just imagine every joint has to move a couple millimetres, and add up the total...those things sway in the wind to say the least.

[Lewie]

2 hours ago, Meecrob said:

Haha, I'm glad you made this post...I woke up and read what I wrote, and wish I could delete it. Nobody here needs a lecture...least of which from me. Let me have an old man moment and ignore me. I'll shut up.

No harm done! We’re all friends here

[mikegarrison]

5 hours ago, JoeSchmuckatelli said:

Working from a cherry picker at that height has to be...

Exciting 

I have done a fair bit of mountaineering, and heights per se don't bother me (especially when I'm anchored). But I hate ladders. It wouldn't bother me that the thing was so high up. It would bother me that (unlike a mountain) it probably sways a little (or worse, a lot).

[JoeSchmuckatelli]

8 minutes ago, mikegarrison said:

I hate ladders

That is so funny - I'm the same way: I've free climbed in the the Alps, Rockies and Sierra Nevadas... But ladders? 

Nope. 

I'm a big baby when it comes to ladders - and as a one-time carpenter building houses... That phobia was often on display.  

Had completely forgotten about it until your post! 

 

[tater]

3 hours ago, mikegarrison said:

I have done a fair bit of mountaineering, and heights per se don't bother me (especially when I'm anchored). But I hate ladders. It wouldn't bother me that the thing was so high up. It would bother me that (unlike a mountain) it probably sways a little (or worse, a lot).

Does looking down off an edge give you the creeps, standing? I'm fine roped, going UP, and I'm even OK rappelling, but standing at an edge and leaning over gives me the willies. A buddy of mine just walks to the edge of stuff and leans over that I would literally lay on my stomach to look down from.