totm nov 2023 SpaceX Discussion Thread

[tater]

14 hours ago, AckSed said:

What shape would it be? Double door vs. single-door? Where would you put the hinge(s)?

Decades ago the Boeing "Big Onion" had this:

This maintains the inherent strength of the ring construction (with bracing, obviously). The downside of this type of bay door for SS would be that it separates through the heatshield. This seems to me to be the lowest mass option—but the heatshield issue is serious.

Any system they come up with will require substantial bracing to deal with loads on the vehicle during ascent and descent. It's doable, like everything else it will be a mass trade—large opening will eat into payload mass due to substantial bracing.

 

[magnemoe]

16 hours ago, AckSed said:

A question for Exoscientist, because that alt. Shuttle brought it to mind: how would you design the payload bay doors of Starship?

Assume that, no matter what, the stretched version with heatshield will be built; I don't think SpaceX's course will be changed no matter the merit of an expendable version.

What shape would it be? Double door vs. single-door? Where would you put the hinge(s)?

I imagine the double-door with longitudinal split might retain some of the stiffness.

I would go for an single hinged door but hinge it on one side rather than double doors like the shuttle as two doors would be less rigid and harder to close. 
Closing the doors is pretty straight forward.  You rotate it to close and then use rotating cams who interact with latches who both tighten the doors and then lock it in place. 
Its used on stuff like nose and rear doors on cargo planes and is air thigh who is not needed on cargo starship. 
Benefit of dual doors is that its easier to open on ground and it take up less space then integrating payload. 
The whale mouth is an bad idea, hinge surface would be tiny compared to side hinges, it makes it hard to load payload on ground unless open it 180 degree. +90 degree is also needed to launch satellites sideways rather than kind of forward. 

[magnemoe]

43 minutes ago, tater said:

Decades ago the Boeing "Big Onion" had this:

This maintains the inherent strength of the ring construction (with bracing, obviously). The downside of this type of bay door for SS would be that it separates through the heatshield. This seems to me to be the lowest mass option—but the heatshield issue is serious.

Any system they come up with will require substantial bracing to deal with loads on the vehicle during ascent and descent. It's doable, like everything else it will be a mass trade—large opening will eat into payload mass due to substantial bracing.

Not very practical, heat shield is one thing, piping to the header tanks is an much harder nut to crack as this has to be flexible or be able to seal and unseal. 
Now I think you could have significant force on doors with enough bracing. Cargo planes with nose and tail doors comes to mind, they are also air thigh.  

It might be multiple versions here, first will be the starlink dispensers, moonship and tankers. For satellite services 100 ton to leo is overkill.  But an 3rd stage to take stuff up to GTO or GEO would be nice more if if you can reuse it who require returning to an starship and dock, it does not need to be the same starship but need to be one it can dock with. 
This is an free business idea 
 

[darthgently]

HLS tidbits

Tom Bickmore:

”Inside the HLS prototype there are 5 bedrooms (ISS style, but horizontal), and a picture showing that you can fit 20 in one ring around the ship.
Being inside makes it SO clear that it's stupid big, and there will be no lack of space with any size crew. 
They only have 2 floors so far:
One with very laid out life support, all clear to see (& in use). 
The main one with the bedrooms, a storage area, 4 control seats, and a 40ft ceiling.”

Edited November 1 by darthgently

[Terwin]

21 minutes ago, darthgently said:

The main one with the bedrooms, a storage area, 4 control seats, and a 40ft ceiling.”

Makes me think back to family road-trips where the back of the van was packed with coolers, bedding, etc. until it was roughly even with the back seat.

If that room has a 40' celling, they will probably have so much stuff packed into that room that they do not see the beds until they get back to earth orbit.(not even then if it is half-filled with surface samples)

[darthgently]

Possible Moon scenario (in my mind):  All SpaceX HLS stay on surface as permanent base, all astronaut return from surface is via other smaller landers brought down autonomously

Edited November 1 by darthgently

[AckSed]

I've always thought that Starship HLS is 'pay for lander, gain a free moon base'.

[darthgently]

I’m shocked this topic didn’t get TOTM oct 2024.  Which one did?

[cubinator]

3 hours ago, Terwin said:

Makes me think back to family road-trips where the back of the van was packed with coolers, bedding, etc. until it was roughly even with the back seat.

If that room has a 40' celling, they will probably have so much stuff packed into that room that they do not see the beds until they get back to earth orbit.(not even then if it is half-filled with surface samples)

I can't WAIT to see one of these things come back to Earth filled to the brim with well-packaged, organized and labeled lunar rocks.

Edited November 1 by cubinator

[Terwin]

19 hours ago, darthgently said:

I’m shocked this topic didn’t get TOTM oct 2024.  Which one did?

It already got TOTM for Nov 2023, is it even eligible for more than one?

[CatastrophicFailure]

On 11/1/2024 at 11:33 AM, Terwin said:

If that room has a 40' celling, they will probably have so much stuff packed into that room that they do not see the beds until they get back to earth orbit.(not even then if it is half-filled with surface samples)

This first unit will mostly be a tech demonstrator, it’s meant for two people on the surface for a week. Further iterations to support longer stays with more people will make better use of that space. I doubt they’d put much up there right now, wouldn’t want it falling on your head if the landing was a bit hard…

Speaking of such, for the math wizards out there: if you climbed all the way to the ceiling and let go in lunar gravity, how fast would you be moving when you hit the floor, and what height drop would that be comparable to on earth? Y’know, for… reasons… 

21 hours ago, cubinator said:

I can't WAIT to see one of these things come back to Earth filled to the brim with well-packaged, organized and labeled lunar rocks.

Keep in mind, any samples coming back any time soon are gonna have to fit in Orion. That nice boulder is gonna have to stay where it is for a while. 
 

Spoiler

 

[tater]

17 minutes ago, CatastrophicFailure said:

Speaking of such, for the math wizards out there: if you climbed all the way to the ceiling and let go in lunar gravity, how fast would you be moving when you hit the floor, and what height drop would that be comparable to on earth? Y’know, for… reasons… 

~6.3 m/s at the ground—about like a 6-7 ft drop on Earth.

[darthgently]

3 hours ago, Terwin said:

It already got TOTM for Nov 2023, is it even eligible for more than one?

Don’t know

[Hotel26]

8 hours ago, CatastrophicFailure said:

how fast ... what height

v = at and s = at² / 2 and both are linear with a (acceleration) and lunar a is 1/6th of earth.  So a 40' fall on the Moon would be equivalent to about 6' earth.  (Just a guess: I never double-check my work.)

 

Edited November 3 by Hotel26

[Flying dutchman]

Will the combination of slighly stretched tanks and the use of raptor 3 fix starships payload margins?

[tater]

 

[AckSed]

I don't know.

It might, to a point... if I knew exactly how heavy the current structure was, and we see Raptor 3s being produced at scale.

Activate data-mining...

I'll bring up the Ars article: https://arstechnica.com/space/2024/04/elon-musk-just-gave-another-mars-speech-this-time-the-vision-seems-tangible/

Quote

We do know that a kilo of saved mass on a second stage like Starship directly translates to payload. Going by the rule of thumb in the Eager Space video "Why Starship Loves Stainless Steel", six kilos saved on the booster translates to 1 kilo of payload.

Quote

Raptor 1 (sea level variant): Thrust: 185tf; Specific impulse: 350s; Engine mass: 2080kg; Engine + vehicle-side commodities and hardware mass: 3630kg

Raptor 2 (sea level variant): Thrust: 230tf; Specific impulse: 347s; Engine mass: 1630kg; Engine + vehicle-side commodities and hardware mass: 2875kg

Raptor 3 (sea level variant): Thrust: 280tf; Specific impulse: 350s; Engine mass: 1525kg; Engine + vehicle-side commodities and hardware mass: 1720kg

Raptor 3, taking into account the reduced support equipment like heatshields, will apparently save 38 metric tons on the booster. Plug in that 6:1 ratio and it's an extra 6.3 tons of payload. Not great, but it's something.

With three SL R3s on Starship, you save a further (2875 - 1720) * 3 = 1155 *3 = 3.46 tons.

In total, that's 9.76 tons of extra payload. Which might be washed out by the stretched tanks and the 3 extra Vac R3 in Version 3, but not entirely.

I'm nowhere near awake enough to calculate how much mass fractions improve with stretched tanks, but all things considered... it might help the most?

You'll note that Superheavy has barely grown, while Starship has grown the most in proportion, more than doubling the thrust and almost doubling the propellant.

Last year at the IAC 2023, Musk dropped three pieces of info:

SpaceX is shifting more of the delta-V burden to Starship;

Propellant ratio between Superheavy and Starship trending towards 2:1;

Staging time is trending towards 100 seconds.

This is because the lofted trajectory Superheavy takes to enable RTLS means even more of the work in getting to orbit is being pushed off on Starship; it is staging earlier and has a lot of thrust. All info taken from ES's "Starship Optimization - New Rocket, New Tradeoffs".

In the back-of-the-envelope analysis he made, he notes that if you want the staging to be that early, you can either carry less propellant, or burn it faster.

It seems this year SpaceX is leaning towards the "Full Stretch", because there's always room for more propellant, and with more engines and more thrust, you gain engine-out capability and the ability to stage earlier and travel faster.

Again, I'm not awake enough to properly calculate how much benefit this will be to payload.

[tater]

Most payload mass is gonna be propellant anyway.

[softweir]

8 hours ago, tater said:

Most payload mass is gonna be propellant anyway.

Most Launch organisations don't count propellant as payload unless you are talking about a propellant tanker refuelling another, orbiting vessel. Normally, the payload mass is exclusively the stuff somebody is paying to go into space - the satellite(s), the astronauts, the space station module and so on. Hence "Payload".

[tater]

33 minutes ago, softweir said:

Most Launch organisations don't count propellant as payload unless you are talking about a propellant tanker refuelling another, orbiting vessel. Normally, the payload mass is exclusively the stuff somebody is paying to go into space - the satellite(s), the astronauts, the space station module and so on. Hence "Payload".

With Starship, if the target orbit is LEO, everything above the mass of the vehicle (and reserved props for EDL) is payload. The majority of SS launches will in fact be for refilling ops, many per HLS or Mars flight. Since that's a capability they need to demonstrated sooner rather than later for HLS milestones, it makes sense to get it there soon. There's loads of stuff they need to do to actually refill a ship.

There are no very massive payloads for SS, honestly, even with a 9m dia, payloads will in fact be volume, not mass limited. Starlink 2 (3?) will be designed to maximize packing in SS, and will still be nothing like hundreds of tons per launch.

[tater]

This is interesting:

https://ntrs.nasa.gov/api/citations/20230013972/downloads/CrewLogistics Lander for Common Hab Architecture.pdf

The sorta thing we've talked about here.

 

[darthgently]

When I see the nebulous 200t payload mentioned I can’t help but think that even the small Prufrock 4 12’ diameter tunnel boring machine weighs at least twice that probably.  Need a Prufrock 4B (breakdown model, ships in two pieces).  Or just have the Optimus crew assemble a TBM from parts on site, ha

11 minutes ago, tater said:

This is interesting:

https://ntrs.nasa.gov/api/citations/20230013972/downloads/CrewLogistics Lander for Common Hab Architecture.pdf

The sorta thing we've talked about here.

 

Very cool.  Better than ditching in the ocean or using for lunar seismic research 

Edited November 5 by darthgently

[tater]

49 minutes ago, darthgently said:

When I see the nebulous 200t payload mentioned I can’t help but think that even the small Prufrock 4 12’ diameter tunnel boring machine weighs at least twice that probably.  Need a Prufrock 4B (breakdown model, ships in two pieces).  Or just have the Optimus crew assemble a TBM from parts on site, ha

yeah, if it's heavy eqp to the lunar or martian surface I suppose dense stuff is possible. Generally spacecraft (as payloads) don't tend to be, though.

 

 

[darthgently]

31 minutes ago, tater said:

yeah, if it's heavy eqp to the lunar or martian surface I suppose dense stuff is possible. Generally spacecraft (as payloads) don't tend to be, though.

IFT-5 was a watershed moment, but still has a dreamlike quality to it.  It hasn’t been fully banked yet, but I have to keep reminding myself that massive, large, budget-friendly payloads are going to become possible, then normal.  Good times

[tater]