totm nov 2023 SpaceX Discussion Thread

[RCgothic]

57 minutes ago, tater said:

 

300t of thrust per Raptor... Wow that's ridiculous!

 

Edit: Ooh, page 1000!

Edited September 1, 2020 by RCgothic

[sevenperforce]

With a 10-meter skirt, four legs, and 28 engines, I wonder if we end up with a configuration that looks like this:

Just now, RCgothic said:

300t of thrust per Raptor... Wow that's ridiculous!

Congrats on having the first post of page 1000!!!

[RealKerbal3x]

10 minutes ago, sevenperforce said:

With a 10-meter skirt, four legs, and 28 engines, I wonder if we end up with a configuration that looks like this:

Perhaps, but I think the legs would be wider than that (Musk mentioned a while back that while there would be only four legs, they would have a wider stance).

[sevenperforce]

2 minutes ago, RealKerbal3x said:

Perhaps, but I think the legs would be wider than that (Musk mentioned a while back that while there would be only four legs, they would have a wider stance).

Yeah, I truncated the leg length intentionally shorter for the sake of showing more detail on the inner engine arrangement.

My larger curiousity is whether they will inset four engines in order to place the reinforcement for the legs further inside the skirt. He referenced an "outer ring" but the above configuration would certainly qualify as a ring, I think. 

I also wonder whether the inner engines will be in a pure ring a la N-1 or a configuration more like the one above. He said they will only need two engines for the initial hop tests, which suggests it can land on 2-3 engines easily enough, so you'd think they would put them as close to the center as possible. Also, it has more gimbal range than a pure ring.

They could also do a 2+6 configuration, with two inline engines at the center and six in a ring around them.

[RCgothic]

I was just looking at engine config.

I can fit 28 in 8m diameter without any TVC, so I think you're probably right about a skirt. The most I can fit in 8m with any space for TVC is 24.

I think 10m may be unlikely though - that's a lot of unused space.

I think 875-900mm diameter is probably the minimum space to fit 

Edited September 1, 2020 by RCgothic

[sevenperforce]

2 minutes ago, RCgothic said:

I was just looking at engine config.

I can fit 28 in 8m diameter without any TVC, so I think you're probably right about a skirt. The most I can fit in 8m with any space for TVC is 24.

I think 10m may be unlikely though - that's a lot of unused space.

Starship is 9m standard and I believe the official renders show a 10m skirt. 

He says the outer ring are fixed and do not gimbal at all. So you only need space for TVC in the middle. They want a LOT of control authority on Starship, so we could conceivably be looking at 10 degrees or more in any direction, and they wouldn't do different engines on the booster.

2 minutes ago, RCgothic said:

I think 875-900mm diameter is probably the minimum space to fit 

Do you mean centimeters? Or are you talking about something different?

[sevenperforce]

14 minutes ago, RCgothic said:

For a perfectly circular ring of twenty 1.3m engines that are welded bell-to-bell, you need an outer diameter of at least 9.58m. You can, as you show above, reduce the diameter by insetting the engines.

If SpaceX forgoes the skirt altogether there MIGHT be enough room for gimbal at the center but it would be super tight.

[Entropian]

I managed to fit 42 engines with 2 having enough space to gimbal in a 10 meter diameter circle:

I'm pretty sure I can change it to have more gimballing engines, but fewer fixed engines.

 

[sevenperforce]

25 minutes ago, Entropian said:

I managed to fit 42 engines with 2 having enough space to gimbal in a 10 meter diameter circle:

I'm pretty sure I can change it to have more gimballing engines, but fewer fixed engines.

I think he's given up on doing 42 engines. And that's not enough gimbal space.

If SpaceX drops the skirt altogether they might still be able to make it work with 28 engines:

The example on the left has better control authority on the two central engines, which I know is desired, but less overall gimbal space. The example on the right is more symmetric and has broader gimbal on all central engines.

[tater]

Center engines can hang down for gimbal room...

[Codraroll]

Can't we just sit back and admire how cool it is that we're having a conversation about fitting dozens of engines on a 10m thrust plate, in a fully serious discussion about the configuration of a rocket they're actually going to build?

Also, I wanted a post on page 1000.

[sevenperforce]

6 minutes ago, tater said:

Center engines can hang down for gimbal room...

Agreed. With only 28 engines I don't see how they need any skirt at all.

[tater]

15 minutes ago, sevenperforce said:

Agreed. With only 28 engines I don't see how they need any skirt at all.

Actually, they need no skirt because it's the booster. S2 (SS) needs a skirt for EDL, and because it has to have an interface with S1 (though an interstage would work if not for EDL protection). Oh, and for tail to tail refilling.

S1 has zero need for any skirt.

[magnemoe]

2 hours ago, sevenperforce said:

With a 10-meter skirt, four legs, and 28 engines, I wonder if we end up with a configuration that looks like this:

Congrats on having the first post of page 1000!!!

Unlikely still think they do the more compact 1+6 engines in the center and two rows outside. Good chance the four engines will be moved out into the leg structure as shown with 6. with 1+6 engines in center they can burn with 1,2 or 3 with an center of mass trust.

Outer engines are not stearable and either on or off, Good chance they start to shut down some of them before separation. 

[Dirkidirk]

49 minutes ago, Codraroll said:

Also, I wanted a post on page 1000.

same.

[RealKerbal3x]

Here's a few different options for a 28-engine Super Heavy...

 

[kerbiloid]

59 minutes ago, tater said:

Center engines can hang down for gimbal room...

But need the expanded safety margins, like on the photo.

Upd.
They should put other engines around the rocket, in layers, tilted outside.

Edited September 1, 2020 by kerbiloid

[SOXBLOX]

I like the second one and the last one...

Also, is this the largest thread in the forum? I mean, 1000 pages...

[RealKerbal3x]

2 minutes ago, SOXBLOX said:

Also, is this the largest thread in the forum? I mean, 1000 pages...

'What did you do in KSP today' is the largest. This might be in second place.

[tater]

3 minutes ago, RealKerbal3x said:

'What did you do in KSP today' is the largest. This might be in second place.

It's slightly faster to build new rockets in KSP than SpaceX can manage, hence more posts.

[SOXBLOX]

Ah. I should have checked...

Also, is Dragon XL still a thing? Or would Musk cancel it and move its tasks to Starship?

Edited September 1, 2020 by SOXBLOX

[tater]

Course the previous SpaceX renders have a skirt, so...

[sevenperforce]

1 hour ago, tater said:

Actually, they need no skirt because it's the booster. S2 (SS) needs a skirt for EDL, and because it has to have an interface with S1 (though an interstage would work if not for EDL protection). Oh, and for tail to tail refilling.

S1 has zero need for any skirt.

Official renders show a flared 10m skirt even though it doesn't come down to cover the bells:

32 minutes ago, RealKerbal3x said:

Here's a few different options for a 28-engine Super Heavy...

 

That last render is exactly what I think is most likely. 

Would fit in a 9m circle if you welded the fixed bells together.

[Spaceception]

56 minutes ago, SOXBLOX said:

Also, is Dragon XL still a thing? Or would Musk cancel it and move its tasks to Starship?

As far as we know, yes. It's contracted for Cargo delivery, and until NASA accepts Starship for Gateway operations, D-XL will be the intended vehicle. If they get the next contract for their Lunar variant, that would point to a higher confidence in Starship from NASA, and D-XL may have a short lifespan.

[sevenperforce]

43 minutes ago, Spaceception said:

As far as we know, yes. It's contracted for Cargo delivery, and until NASA accepts Starship for Gateway operations, D-XL will be the intended vehicle. If they get the next contract for their Lunar variant, that would point to a higher confidence in Starship from NASA, and D-XL may have a short lifespan.

Also, Starship likely will not be able to dock directly to LOP-G due to transverse loading limits on the docking port. After the ISS was constructed, the Shuttle could only dock to the end node for this reason.

However, DXL and Orion would both be able to dock to Starship and ferry cargo/crew between both.