totm nov 2023 SpaceX Discussion Thread

[KSK]

Oh man - that is a thing of beauty.  We are truly living in the future.

Godspeed SN8.

[Flying dutchman]

Sn8 looks to be taller than mk1, has anyone done a comparison?

Edited October 23, 2020 by Flying dutchman

[RealKerbal3x]

31 minutes ago, Flying dutchman said:

Sn8 looks to be taller than mk1, has anyone done a comparison?

They look pretty much the same height, I think it's just the stand that SN8's sitting on making it seem taller.

[sevenperforce]

13 hours ago, tater said:

 

So damn beautiful.

[cubinator]

This is gonna work.

[RealKerbal3x]

Full view of SN8's stacking as well as some Raptor juggling:

Seems like they pulled SN39 out, were ready to put SN36 in to replace it but then put both of them on a truck and carried them back to the shipyard.

[sevenperforce]

All the cranes hanging around as it comes together reminds me of the early Iron Man suit up scenes...except instead of machine arms putting it together, it's cranes with people, and instead of Tony Stark getting wrapped in armor, it's a spaceship.

I wonder how they are attaching the downcomer...I would have imagined someone would be inside to line up the piping?

[magnemoe]

11 minutes ago, sevenperforce said:

All the cranes hanging around as it comes together reminds me of the early Iron Man suit up scenes...except instead of machine arms putting it together, it's cranes with people, and instead of Tony Stark getting wrapped in armor, it's a spaceship.

I wonder how they are attaching the downcomer...I would have imagined someone would be inside to line up the piping?

Yes they will need to send some inn to line up and weld the downcommer. Now it should be more piping, you need one to top off the header tank, this might also be return pipe to header. Add pipe for pressurization and power and control. 
Surprised they don't have an raceway between lower and upper fin mounts. 

[CatastrophicFailure]

51 minutes ago, magnemoe said:

Yes they will need to send some inn to line up and weld the downcommer. Now it should be more piping, you need one to top off the header tank, this might also be return pipe to header. Add pipe for pressurization and power and control. 
Surprised they don't have an raceway between lower and upper fin mounts. 

There’s a couple pictures over on NSF as well as some chatter that the nose might indeed be bolt-on.  The structures inside seem far too substantial for mere alignment jigs, they look meant to hold significant force. If that’s the case, the assorted plumbing inside could be some sort of quick-disconnect fittings, or just short sections of flex pipe with bolt-together flanges.

[JoeSchmuckatelli]

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

[Clamp-o-Tron]

1 minute ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

I think they will retract them during flight- if not then super heavy's fins will be enough

[Deddly]

2 minutes ago, JoeSchmuckatelli said:

What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

Even bigger wings at the bottom.

[RealKerbal3x]

9 minutes ago, CatastrophicFailure said:

There’s a couple pictures over on NSF as well as some chatter that the nose might indeed be bolt-on.  The structures inside seem far too substantial for mere alignment jigs, they look meant to hold significant force. If that’s the case, the assorted plumbing inside could be some sort of quick-disconnect fittings, or just short sections of flex pipe with bolt-together flanges.

The Starship payload user's guide does mention that Starship payloads are intended to be integrated into the payload section while it is separate from the rest of the vehicle, with the payload section later being installed on the launch pad. Having a payload section/fairing that can be easily and quickly be installed/removed would certainly seem to work with this plan.

Edited October 23, 2020 by RealKerbal3x

[CatastrophicFailure]

15 minutes ago, Clamp-o-Tron said:

I think they will retract them during flight- if not then super heavy's fins will be enough

Also, SpaceX has a much better version of MechJeb. 

[Guest]

20 minutes ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

The bottom wings might not be that large, but considering they'll have a greater lever arm in relation to the "canards" that's likely the minimal size required to stabilize it

[sevenperforce]

16 minutes ago, RealKerbal3x said:

The Starship payload user's guide does mention that Starship payloads are intended to be integrated into the payload section while it is separate from the rest of the vehicle, with the payload section later being installed on the launch pad. Having a payload section/fairing that can be easily and quickly be installed/removed would certainly seem to work with this plan.

Yep.

"Payloads are integrated into the Starship fairing vertically in ISO Class 8 (Class 100,000) cleanrooms. Then the integrated payload stack is transferred to the launch pad and lifted onto the Starship vehicle, while maintaining the same vertical orientation throughout the entire process. Conditioned air is delivered into the fairing during encapsulated ground processing while in the processing facility and on the launch pad."

25 minutes ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

The fixed fin-legs on Superheavy definitely help keep the center of pressure back. More importantly, though, a computer-programmed ascent typically flies prograde all the way through the atmosphere, with virtually no deviation beyond the initial pitchover. If the angle of attack stays at zero relative to the airstream, the forward wings never "bite" into the air and cause torque on the vehicle.

Finally, the Raptors boast 15 degrees of gimbal which is a LOT of control authority to maintain that heading.

[RCgothic]

44 minutes ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

IRL flight computers are much more capable and engine gimbal is capable of defeating quite substantial aerodynamic forces.

E.g. Falcon 9 has no rear fins and a fairing that is larger than the main body. In KSP that's a no-no, but it's actually not that big a deal.

[StrandedonEarth]

52 minutes ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

I agree with all the other answers here. I’ve launched many draggy, hammerhead payloads in KSP; you just need even bigger fins at the bottom. I mean, I’ve used FAT-455 wings as fins to stabilize an un-fairinged (that’s probably not a word, but it was too big to fit anything) station hub during launch. 

[Meecrob]

3 hours ago, cubinator said:

This is gonna work.

I can be sure about death, taxes and the fact that the first Starship flight will not go according to plan. The reasoning is simple. Its a prototype. It would be operational if they knew it would not crash.

Edited October 23, 2020 by Meecrob

[Meecrob]

1 hour ago, CatastrophicFailure said:

There’s a couple pictures over on NSF as well as some chatter that the nose might indeed be bolt-on.  The structures inside seem far too substantial for mere alignment jigs, they look meant to hold significant force. If that’s the case, the assorted plumbing inside could be some sort of quick-disconnect fittings, or just short sections of flex pipe with bolt-together flanges.

What is the issue with bolt on aside from slightly increased weight...This is roughly a thousand(? hundred?) kilograms on a ship classed in hundreds of tonnes? This is a prototype. The issue is rapid debugging, not efficiency right now.  In all honesty, this ship (or a subsequent SN) WILL crash and the real question is "how much refinement do we pay to make this wreckage more efficient, or should we save it for SN 30(-ish)?"

1 hour ago, JoeSchmuckatelli said:

Okay - KSP question time:  Every single attempt at putting even a small spaceplane at the top of a large rocket ended up in horrible failure.  My 'best guess' to this is that I had wings way up high.  What is Starship doing IRL that keeps the 'wings' at the nose of the spacecraft from flipping the rocket during launch?

The difference is that you are calling them 'wings" but they are not. Wings provide lift based on their angle of attack to the relative airflow. These fins are aligned with the airflow and yes, they will give a bit of drag, but if angled parallel to physical motion, they will provide exactly zero lift. You can check me by looking at a cross section of them compared to an actual wing. Or you can check in KSP...toss on some passive fins in 2x symmetry and aim up...then tell me how those fins changed your trajectory without your input. Remember that these fins move perpendicular to the fins you imagine in KSP. They "tilt" rather than "rotate." So I guess the next question is as the gravity turn is executed, don't the fins provide lift from their angle of incidence? aside from the fact that the "grip" on the atmosphere lessens with altitude, they can simply fold the fins. Wings don't work pointing down kinda thing.

I can't find the "strike-through" button, but I didn't answer your question with what I said and I am factually wrong that zero lift is created by the fact that a gravity turn is needed. The best answer with regards to not typing a novel is that you need to screw around with those aerodynamics for probably 90% more time than you built the rest of the rocket...there is an angle that they generate zero lift during the gravity turn and it is dynamic. There is no one solution...you can optimize the rocket for certain trajectories though. An extreme example would be launching straight up, then 90* over at the Karman line. In atmosphere though, there is a bunch of mathematics way way above my level that predicts this behavior...so the question is really "how much percent efficiency do we sacrifice in this stage of the launch to gain efficiency at this other stage? We lost say 5% overall, but we can launch three times the mass that our competitor can do...and not need to literally build a new one to do it again.
I think we are on the exact same page as far as thinking "there's no way they are launching with that aerodynamic stability...a gust of wind will love it up" but it will only love up if those lift vectors are aligned in a certain direction. Again, a KSP example...mess around with a craft with the centre of lift display on, then change the fins' angles...you will be sure to find an angle where the fins cancel eachother out. Mathematically we can jump to 90* and it turns into an issue of how strong do the fin mounts need to be to counteract the outward force, and not detach from the body. Of course, drag and weight is in play here, but the simple answer is that its still cheaper to re-use a rocket than to gain like 2% in fuel burn efficiency. ULA might disagree with me on that last point haha.

Edited October 23, 2020 by Meecrob

[RealKerbal3x]

 

[tater]

 

Those are replies to the Austin Barnard tweet @RealKerbal3x posted.

[tater]

Cool render:

 

 

[Clamp-o-Tron]

Just now, tater said:

Cool render:

 

 

The perspective freaked me out for a second until I realized that the payload bay door was extending under the body and aero surfaces.

The lift capacity and payload space is truly massive. I wonder what will happen to the launch market if Elon gets his way and it's flying at least once a week for <20 million. I can see a niche for Rocket Lab, Firefly, Astra, heck even Virgin Orbit, but what about the rest of the launch market, especially if DoD bites the bullet and gets rid of Vulcan?

[tater]