totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

45 minutes ago, magnemoe said:

1 hour ago, RealKerbal3x said:

I don't know if they pressurise the forward section (I'd be inclined to think they don't), but it's not filled with propellant.

Forward section will be the cargo bay and its empty for the test flights.  It will have an huge door for the later cargo versions making it very hard to pressurize. 
The crewed version will have an internal pressure hull. They but the lox header tank at the front to move center of mass forward for landing. 

That's actually a really interesting question. The Falcon 9 fairing is pressurized to 1 atm at launch but vents slowly during ascent to match ambient, so when it is opened it's not, like, venting. However, it's not like the Falcon 9 fairing actually closes so the problem isn't considered in reverse. 

Pressurizing the cargo bay would help tremendously to strengthen everything on re-entry, especially because having the LOX tank and forward fins up there means you're bearing a significant load. The cargo bay of the Shuttle wasn't really load-bearing since it had an aerodynamic structure under it.

The Shuttle had vents along the sides of the payload bay (or maybe the vents were in the payload bay doors) to allow the pressure to remain equalized on the way up and on the way down.

[JoeSchmuckatelli]

31 minutes ago, sevenperforce said:

That's actually a really interesting question. The Falcon 9 fairing is pressurized to 1 atm at launch but vents slowly during ascent to match ambient, so when it is opened it's not, like, venting. However, it's not like the Falcon 9 fairing actually closes so the problem isn't considered in reverse. 

Pressurizing the cargo bay would help tremendously to strengthen everything on re-entry, especially because having the LOX tank and forward fins up there means you're bearing a significant load. The cargo bay of the Shuttle wasn't really load-bearing since it had an aerodynamic structure under it.

The Shuttle had vents along the sides of the payload bay (or maybe the vents were in the payload bay doors) to allow the pressure to remain equalized on the way up and on the way down.

@mikegarrison might have input.  I've read, but don't know for sure, that high-altitude airliners while pressurized are not actually holding sea-level pressure while in flight.  Perhaps there's a structural reason beyond keeping the minimum pressure required to keep the cargo alive.

[zolotiyeruki]

2 minutes ago, JoeSchmuckatelli said:

@mikegarrison might have input.  I've read, but don't know for sure, that high-altitude airliners while pressurized are not actually holding sea-level pressure while in flight.  Perhaps there's a structural reason beyond keeping the minimum pressure required to keep the cargo alive.

I can answer that.  Airliners are typically pressurized to about 8,000 feet.  That's a high enough pressure to keep everyone alive and cogent (10,000 ft is where some people start getting hypoxia), while decreasing how much pressure the fuselage has to maintain.  Atmospheric pressure at 35,000 ft is about 3.5 psi, at 8,000 ft it's about 10.9, and at sea level, 14.8.  Instead of withstanding (14.8-3.5 = ) 11.3psi, the fuselage only has to hold up to (10.9-3.5=) 7.4psi.

[mikegarrison]

34 minutes ago, zolotiyeruki said:

Airliners are typically pressurized to about 8,000 feet.

Older airliners.

The 787 increased its cabin pressure to 6000 ft, and the A350 matched that.

[tater]

1 hour ago, mikegarrison said:

The 787 increased its cabin pressure to 6000 ft, and the A350 matched that.

My house is higher than that, lol.

[tater]

And on topic:

 

[JoeSchmuckatelli]

New concrete work

 

Is that around the same launch platform we are used to seeing?

[tater]

That I think is "pad B."

[tater]

Those get put on the existing section that is there. Tower set to grow fairly quickly.

[mikegarrison]

2 hours ago, tater said:

My house is higher than that, lol.

As are some airports. The systems will, for instance, actually raise the cabin altitude during descent rather than lower it if the flight management computer knows the plane is landing in Mexico City.

[tater]

1 minute ago, mikegarrison said:

As are some airports. The systems will, for instance, actually raise the cabin altitude during descent rather than lower it if the flight management computer knows the plane is landing in Mexico City.

The lower alt pressurization possible is the result of CFC fuselages, right? I want to say that I read the humidity can also be kept at a better level as well. Very cool.

[SpaceFace545]

1 hour ago, tater said:

Those get put on the existing section that is there. Tower set to grow fairly quickly.

How are these photos taken, they look 3D somehow? Probably just the weird perspective.

Edited May 19, 2021 by SpaceFace545

[JoeSchmuckatelli]

4 minutes ago, SpaceFace545 said:

How are these photos taken, they look 3D somehow?

Drone.

Looks like noon from the shadows - so that makes stuff look a bit weird

 

Edit - more likely 11 or 1 at second glance.

Edited May 20, 2021 by JoeSchmuckatelli

[tater]

11 minutes ago, SpaceFace545 said:

How are these photos taken, they look 3D somehow?

Read the watermark. RGV Aerial Photography (Rio Grande Valley = RGV)

9 minutes ago, JoeSchmuckatelli said:

Drone.

Looks like noon from the shadows - so that makes stuff look a bit weird

 

Edit - more likely 11 or 1 at second glance.

Cessna.

 

[CatastrophicFailure]

SpaceX is officially summoning Metal Cthulhu.  

 

[SOXBLOX]

7 hours ago, tater said:

My house is higher than that, lol.

I envy you. I live at 380 ft.

[kerbiloid]

Lowlanders...

[tater]

Just now, kerbiloid said:

Lowlanders...

Spoiler

ObSpaceX:

The amount of work they are doing pretty much all the time is stunning. They're working on Starship like this is the movie When Worlds Collide:

(Starship is actually small compared to the space ark)

 

[RealKerbal3x]

4 hours ago, CatastrophicFailure said:

SpaceX is officially summoning Metal Cthulhu.  

 

This is what is really going on when you radially attach an unnecessary number of Vector engines to the bottom of a fuel tank.

[CatastrophicFailure]

9 minutes ago, RealKerbal3x said:

This is what is really going on when you radially attach an unnecessary number of Vector engines to the bottom of a fuel tank.

No wonder my frame rate goes stark raving mad. 

[SpaceFace545]

7 hours ago, SOXBLOX said:

I envy you. I live at 380 ft.

I live at 5 feet on the ocean, climate change is gonna screw me up one of these days.

[sevenperforce]

13 hours ago, CatastrophicFailure said:

SpaceX is officially summoning Metal Cthulhu.  

 

Okay, now THAT is an awesome sight.

Also, a quandry...

If Superheavy undergoes a benign failure at MaxQ, can all six Starship engines produce enough thrust to resist drag?

[SpaceFace545]

 

cReW SaFetY

[Spaceman.Spiff]

I wonder if that's with the SL and Vac Raptors.

I figure in an abort scenario you want as much thrust as possible, flow separation be damned.

[RealKerbal3x]

15 minutes ago, Spaceman.Spiff said:

I wonder if that's with the SL and Vac Raptors.

I figure in an abort scenario you want as much thrust as possible, flow separation be damned.

Technically, the RVacs (at least the current versions) can run at sea level without flow separation in return for a slight loss of efficiency. So they should be able to run all 6 Raptors in an abort scenario.

22 minutes ago, SpaceFace545 said:

cReW SaFetY

Starship is intended to be made safe for crew not through an abort system (which would be impractical for the large crews SpaceX eventually intend it to carry), but through being extremely reliable and fault-tolerant. As a result, crewed Starship is a long way off - it could be a thousand flights before it's trusted with a crew.

Of course, it'll probably never be as safe as modern commercial airlines for the simple fact that it's a rocket. But it might well be safe enough that you could fly on it without fearing for your life - perhaps comparable to the early days of passenger air travel.