totm nov 2023 SpaceX Discussion Thread

[Flavio hc16]

So, as I predicted, we are going to see also a SH stretch.

[CatastrophicFailure]

30 minutes ago, Exoscientist said:

 I’d like to see them get some actual payload to orbit, even if it’s inert like water or liquid nitrogen.

  Bob Clark

They should follow precedent and send a Cybertruck to Jupiter. 

[tater]

Said ideally internal cost to LEO for SS3 would be $2-3M per launch.

[Flavio hc16]

Also:

 

Raptor 3 thrust:

SL 280 tons

Vacuum: 306 tons

Raptor boost: 330tons

 

Compared to raptor 2:

SL 230

Vacuum 258

 

Raptor 1

 

SL 185

Vacuum 200

 

[Kartoffelkuchen]

1 hour ago, tater said:

Said ideally internal cost to LEO for SS3 would be $2-3M per launch.

Hmm not really a fan of that stretching tbh. Sure it makes sense from a performance perspective, but it will also make the stack much more susceptible to weather and winds again I'd assume, which a SH/SS stack with a lower height/thickness ratio would probably not be. Especially with the aero devices.

Also, it makes Starship landings on another planet even more challenging as to not make it tip over, terrain will absolutely need to be flat and touchdown performed with very little to none horizontal velocity, as long as the leg design doesn't change. It probably  wouldn't be able to take the more "sloppy" F9 booster landings we've seen with the bounces. Especially since the COM will be even higher with the header tank being used for landing too. Astronaut boarding / cargo unloading on other bodies  will also get interesting.

Edited April 6 by Kartoffelkuchen

[tater]

Just now, Kartoffelkuchen said:

Hmm not really a fan of that stretching tbh. Sure it makes sense from a performance perspective, but it will also make the stuck much more susceptible to weather and winds again I'd assume, which a SH/SS stack with a lower height/thickness ratio would probably not be.

Also, it makes Starship landings on another planet even more challenging as to not make it tip over, terrain will absolutely need to be flat and touchdown performed with very little to none horizontal velocity, as long as the leg design doesn't change. It probably  wouldn't be able to take the more "sloppy" F9 booster landings we've seen with the bounces. Especially since the COM will be even higher with the header tank being used for landing too. Astronaut boarding,m / cargo unloading on other bodies  will also get interesting.

Given he talks about most Mars vehicles staying on Mars, I wonder if the stretch could be more of a LEO thing? Dedicated space versions could in fact be different in many ways assuming they are open to specialization.

[tater]

 

[tater]

Prop volume is on the order of 1700 m³ (just assuming 27m height, 9m dia, feeling lazy) for current ship (chime in if there's a better number). I wonder what the max dia a ship could be, if configured more like a fairing? A 13m dia ship could hold the same prop volume with only 46% of the height (~13m). The entire craft could be half the height, and 13m in dia (legs sticking out more when deployed).

Obviously it could be taller.

Or closer to F9 fairing proportions. Obviously they'd then need to rig up larger diam jigs, etc. 13, 14, however many m diameter they want. This for space-based vehicles.

I left the tiles on out of laziness, obviously lunar has PVs—though a tug/ferry version could keep a tile side to do aerobraking to LEO from cislunar.

[darthgently]

47 minutes ago, tater said:

Prop volume is on the order of 1700 m³ (just assuming 27m height, 9m dia, feeling lazy) for current ship (chime in if there's a better number). I wonder what the max dia a ship could be, if configured more like a fairing? A 13m dia ship could hold the same prop volume with only 46% of the height (~13m). The entire craft could be half the height, and 13m in dia (legs sticking out more when deployed).

Obviously it could be taller.

Or closer to F9 fairing proportions. Obviously they'd then need to rig up larger diam jigs, etc. 13, 14, however many m diameter they want. This for space-based vehicles.

I left the tiles on out of laziness, obviously lunar has PVs—though a tug/ferry version could keep a tile side to do aerobraking to LEO from cislunar.

I can only see advantages to LSS being shorter and fatter 

[tater]

14 minutes ago, darthgently said:

I can only see advantages to LSS being shorter and fatter 

With 3mm steel (vs 3.6mm), and giving it LOADS of slop (considering the stage a cylinder), the steel is ~26.5t. Assuming it still needs 6 engines, that's ~9t. So we're at ~37t. Add some wide legs (use the LSS ones shown), that's a few tons—but makes the stance now 21m across, and much less tippy. I think with fitting out, it's maybe in the mid 40t range? Thinner steel also possible—this is a spacecraft. Call it 45t. Full it has 12.3 km/s of dv. A 100% propulsive round trip from LEO to the lunar surface and back to LEO is 12.2 km/s. This vehicle could crew up in LEO, do a lunar mission and return home. 3 expended Starship 3 stacks could fill it—or probably 4 with partial reuse (expend ship, keep booster).

Each 0.11mm reduction in 304L thickness drops the vehicle mass by about a ton. A larger version could also work for a dedicated Mars vehicle, and would have more crew volume. for the same prop load and mass as the current vehicle.

 

 

Edited April 6 by tater

[tater]

 

 

[Meecrob]

14 hours ago, CatastrophicFailure said:

They should follow precedent and send a Cybertruck to Jupiter. 

Thats what the water and the liquid nitrogen is for. Water...for water and also oxygen and hydrogen, and the liquid nitrogen is to cool our beverages on the trip inside the cybertruck. If there are only Kerbal Snacks^TM I swear I'm out right now. Or wait, lets see if Elon would let us put some meat out by the gridfins, so at staging we get some nice barbecue action going. Actually, we could probably rig up a purpose-built gridfin cooker. We're already dealing with titanium so its not like the mass will be huge. Seriously screw space food. Like if we are going interplanetary, we gotta have at least coach airline food or something. Nine months of babyfood? I don't mind pooping in a bag if need be, but gimme something good to poop out, lol

Edited April 7 by Meecrob

[darthgently]

8 hours ago, Meecrob said:

Thats what the water and the liquid nitrogen is for. Water...for water and also oxygen and hydrogen, and the liquid nitrogen is to cool our beverages on the trip inside the cybertruck. If there are only Kerbal Snacks^TM I swear I'm out right now. Or wait, lets see if Elon would let us put some meat out by the gridfins, so at staging we get some nice barbecue action going. Actually, we could probably rig up a purpose-built gridfin cooker. We're already dealing with titanium so its not like the mass will be huge. Seriously screw space food. Like if we are going interplanetary, we gotta have at least coach airline food or something. Nine months of babyfood? I don't mind pooping in a bag if need be, but gimme something good to poop out, lol

I'm picturing the Firefly episode where they are hauling cattle now

[tater]

1 hour ago, darthgently said:

I'm picturing the Firefly episode where they are hauling cattle now

Mars needs steaks.

[Stevie_D]

I'm always intrigued as to how SpaceX is planning to land an ever-taller Starship on a planet without levelled terrain, landing legs, or landing pad infrastructure. I mean, basic physics states that the taller and thinner something is the harder it is to balance. Isn't there a massive danger that one shift in the dirt or a slight incline in the terrain when it lands and Starship topples over? (And I don't mean for the Moon, which obvs the concept showed landing legs, I mean Mars.)

Edited April 7 by Stevie_D
typo

[CatastrophicFailure]

1 hour ago, tater said:

Mars needs steaks.

How many spherical cows can fit in a 13m ShawtyStarShip?

 

Also keep in mind, they are still planning for ≈18m SS/SH in the long future…

I see it like this: the first Starships to Mars (or a proper lunar colony) will be one-way, with wide, one-use LSS-style legs under heat shields (Martian EDL less demanding?). They’ll carry robots that will build level, solid, Mars-crete landing pads for the next, reusable Starships with stumpy-legs, which will bring the crews to finish assembling the mini-Mars-Mechazillas (MMMs) catch towers, 3D-printed in situ, to start using “standard” Starships. 

[darthgently]

1 hour ago, CatastrophicFailure said:

How many spherical cows can fit in a 13m ShawtyStarShip?

This would depend on the cow radius and whether inflated or deflated 

[tater]

Another flight while driving.

[PakledHostage]

3 hours ago, tater said:

Another flight while driving.

You said I-40 was bad, but... maybe slow down?

[Meecrob]

14 hours ago, tater said:

Mars needs steaks.

How is Elon gonna stay fat without mars steaks? The man clearly loves a good cut of meat

 

12 hours ago, Stevie_D said:

I mean, basic physics states that the taller and thinner something is the harder it is to balance.

Yeah, but all the mass will be concentrated at the bottom with a combination of the engines and fuel to make the centre of gravity low enough that the danger of a tip-over is minimized.

Edited April 8 by Meecrob

[darthgently]

31 minutes ago, Meecrob said:

How is Elon gonna stay fat without mars steaks? The man clearly loves a good cut of meat

 

Yeah, but all the mass will be concentrated at the bottom with a combination of the engines and fuel to make the centre of gravity low enough that the danger of a tip-over is minimized.

A taller rocket, while less stable once landed, may be easier to land for the same reason it is easier to balance a broom vertically on your fingertip than a sphere of the same mass and density.  Inertia and lever arms and such

[Meecrob]

1 hour ago, darthgently said:

A taller rocket, while less stable once landed, may be easier to land for the same reason it is easier to balance a broom vertically on your fingertip than a sphere of the same mass and density.  Inertia and lever arms and such

This guy gets it!

[AtomicTech]

Hello,

I'm just getting back into the whole SpaceX-verse; I haven't really been following much since the first Starship test. I know it's a lot but what have I missed (other than the awesome IFT-3)?

Edited April 8 by AtomicTech

[Spaceception]

1 hour ago, AtomicTech said:

Hello,

I'm just getting back into the whole SpaceX-verse; I haven't really been following much since the first Starship test. I know it's a lot but what have I missed (other than the awesome IFT-3)?

IFT-2, which nearly made it to SECO, and was a mostly smooth launch (can't say the same for the recovery attempt).

96 Falcon launches in 2023, with 5 of those being Falcon Heavy, and one of those launching NASA's Psyche probe (FH will launch Europa Clipper this October). 148 planned this year (on track for more than 125 so far) https://www.nasaspaceflight.com/2024/04/spacex-quarter-1/

Booster 1058, which flew the first crewed Dragon, tipped over on the way back after its 19th landing due to high winds (rip in pieces).

Polaris Dawn is picking up, they're getting ready to test Dragon soon in a vacuum environment to simulate the conditions during the spacewalk. The EVA suit will be revealed in a few weeks.

SpaceX has launched 50 people to orbit to date, 2 crewed missions this year.

Falcon 9 launched 3 times in 20 hours in March. And 12 times overall (not including IFT-3).

Starlink was breakeven last November, and has over 2.6 million subscribers, it's estimated to rise to over 3.8 million before the end of the year. So it'll likely start making SpaceX money they can use on other endeavors https://payloadspace.com/predicting-spacexs-2024-revenue/

That's not nearly all of it, but that's off the top of my head.

Edited April 8 by Spaceception
Links

[Exoscientist]

On 4/6/2024 at 3:05 PM, tater said:

 

 

 

 About 31 minutes in Elon suggests the current version V1 would be capable of 40 to 50 tons to orbit. This is bad because SpaceX sold NASA on the idea the Starship HLS could serve as an Artemis lander based on 150 tons to orbit reusable  and “10ish” refueling flights. If the capability is max 50 tons, then it would take “30ish” refueling flights. 

 If they intend to use version V2 then this is bad because it would require further qualification flights for the larger version and more importantly further qualification of the more powerful Raptor 3 engine needed.

 This last is doubly bad because I’d be willing to bet dollars to donuts that they never informed NASA that the current version couldn’t do it and further development would be required for the larger version.

  Bob Clark