totm nov 2023 SpaceX Discussion Thread

[magnemoe]

11 minutes ago, tater said:

The proper test stand is a launch pad. They have what, 17 acres to play with?  Any flame diverter they build would need to be under the pad anyway.

Digging a trench at ~1m above sea level is not a thing, BTW. They'd have to first build a hill, then they'd need the space to have a workable slope for transporting the vehicles, which I doubt fits in the small property (the road is owned by the state).

As for proper launch sites, there are not many places to build any—all proper launch sites are on a coast, and there is limited coastal real estate.

Yes SpaceX selected an tower over an trench since Starship and superheavy can be lifted up on it who is unique for large rockets. 
Most transport their rocket vertical on an stand who also is launch mount or horizontal with an trolley who also lift the rocket up like Soyuz or Falcon 9. 
Height above ground is equivalent to the flame trench depth at pad 39 a.
The problem is that concrete did not stand up to the launch forces
 

[darthgently]

8 hours ago, magnemoe said:

A valid point, now you have engine gimbal and differential trust but I guess this has some lag especially on such an large rocket, think steer an large ship. 
Now you could gimbal while holding, but I don't imagine they will launch an operational Starship with an engine out at launch. 

I say its a bit strange they used an starship with heat tiles for first launch, more so with 90% trust. First reach orbit and get data for superheavy boost back and landing simulation as in water landing. 
You might sacrifice starship for superheavy data and you don't need an serious boost back burn, just stay inside the crash zone.
That is unlike they assumed they would reach orbit. 
 

I figured the tiles were on just to get data on the fastening strength through launch and ascent and maybe, fingers crossed, reentry

[tater]

6 hours ago, kerbiloid said:

Iirc, these nerds are launching military and spy sats.
In 1940s the land was owned, too, but in never made a problem with removing a rocky planet from the highway to be built.

***

https://texasfarmcredit.com/resources/texas-land-pricing-guide/#:~:text=The average price per acre,%244%2C297%2Facre average in Q2

2 000 000 000 / 5 000 = 400 000 acres ?

Bezos bought over 400,000 acres in TX for his facility. But it's inland, so useless for launching rockets. Coastal land is far more expensive. Looks like on the order of a few hundred grand per acre. More importantly, it's nearly all built up.

4 hours ago, kerbiloid said:

While it's on paper.

Once it starts flying, it will be a military project as well.

Orbital lasers, orbital maneuvering sat depots, orbital hypersonic maneuvering reentry vehicles.

Nothing such capable can be just civilian.

LOL.

 

 

[magnemoe]

5 hours ago, tater said:

Bezos bought over 400,000 acres in TX for his facility. But it's inland, so useless for launching rockets. Coastal land is far more expensive. Looks like on the order of a few hundred grand per acre. More importantly, it's nearly all built up.

US has lots of areas not even suitable for grassing. This is cheap land, coastal areas are expensive outside of Alaska. 
Grabbing lots of land was much cheaper back the the air force rocket base was set up in Florida. Florida was not an primary tourist destination for one  And Holiday homes or an house for after you retired was something for the  0.1%. 
And Starship is obviously an private project. Yes the military will be very interested then it works out. But even if the military want an Starship bomber for rods of god strikes it would be an modified starship the same way some tankers and command and control planes are modified civilian planes. 

[Nuke]

incidentally the coast line is less than 50 feet away from where i live and this is subsidized housing. a lot of these southeast alaska towns are long and skinny, barely two roads in from the coast, so live anywhere and its oceanfront property or pretty close to it. 

Edited May 7, 2023 by Nuke

[darthgently]

32 minutes ago, Nuke said:

incidentally the coast line is less than 50 feet away from where i live and this is subsidized housing. a lot of these southeast alaska towns are long and skinny, barely two roads in from the coast, so live anywhere and its oceanfront property or pretty close to it. 

Surf's Up!  (brrrrrr)

[Nuke]

21 minutes ago, darthgently said:

Surf's Up!  (brrrrrr)

hypothermia isnt for me. 

[JoeSchmuckatelli]

16 hours ago, magnemoe said:

military will be very interested then it works out.

I suspect the jury is still out on that.   We ran a lot of scenarios up thread - and it's cargo capacity, while impressive for space, is kind of negligible for military operations.  IIRC, it could carry the equivalent of three 40' shipping containers to a safe rear area. 

 

[sevenperforce]

On 5/7/2023 at 5:42 AM, kerbiloid said:

On 5/7/2023 at 4:43 AM, Hannu2 said:

Starship is civilian project.

While it's on paper.

Once it starts flying, it will be a military project as well.

On 5/7/2023 at 4:43 AM, Hannu2 said:

Starship will be ready before there will be military payloads which need Starship's capacity.

Orbital lasers, orbital maneuvering sat depots, orbital hypersonic maneuvering reentry vehicles.

Nothing such capable can be just civilian.

Your Kremlin is showing.

[sevenperforce]

On 5/7/2023 at 1:35 AM, kerbiloid said:

How about at least building a proper test stand for the full engine assembly, digging an exhaust trench like others do, and probably not putting so many engines in a cramped skirt where they burn each other (square-cube law?) ?

A launch pad is a proper test stand. Why would you need a separate facility to do the exact same thing?

The pad at Boca Chica does have an exhaust trench. A milkstool creates an open-air exhaust "trench" in place of a physical one. That's what the Apollo Milkstool did for the Saturn 1B and that's what the OLM does for Superheavy.

Engines won't burn each other due to proximity when they are actively cooled. These aren't RS-68s.

On 5/7/2023 at 6:31 AM, RCgothic said:

Short of putting the launch site at the tip of Florida in Southern Glades Wildlife & Environmental area, there's basically no eastern seafront that isn't densely populated.

Boca Chica was an ideal location and it's frankly miraculous they got a site as good as they did.

I'm reminded of From the Earth to the Moon by Jules Verne. Tackled this exact problem and came up with almost the exact same result.

[kerbiloid]

1 minute ago, sevenperforce said:

The pad at Boca Chica does have an exhaust trench.

Now it does. The exhaust has dug it.

Now it doesn't. They have filled it with concrete.

 

[sevenperforce]

Just now, kerbiloid said:

Now it does. The exhaust has dug it.

Now it doesn't. They have filled it with concrete.

The milkstool creates a circumferential flame trench. They just need to make sure the surface underneath doesn't go all pyroclastic rock tornado like it did last time.

Interested in running some numbers on this upside-down showerhead idea.

Raptor yeets 650 kg/s of exhaust out the back end at 3,210 m/s. Assuming all the exhaust plumes generally merge under the 10.3-meter base of Starship, that's a dynamic pressure of 3.71 megapascals. Really quite shockingly low if you think about it -- less than the water pressure in the output of your typical coin-operated car wash spray nozzle. The coolant loops in a pressurized water reactor run 4-5x higher.

I wonder if the holes at the center of the showerhead will be larger than the holes near the circumference, to create a sort of virtual cone of water. That kind of design might also help relieve internal pressures that could otherwise cause it to expand in the center. 

Water fountains have been built with higher pressures than this already. King Fahd's Fountain in Jeddah, built in 1985, continuously pumps sea water through a single nozzle at 4.2 megapascals to almost twice the height of the OLT. Building something at slightly lower pressure which fires for only a few seconds should be straightforward despite the much higher flow volume.

[kerbiloid]

The empirical engineering is whispering to us, that if the ground is deformed, the pad should be lifted at least by this depth value up, but better enough high to stop deforming the ground.

That's how the exhaust trenches were invented.
The engineers were tired by cleaning the mud from their faces.

Edited May 8, 2023 by kerbiloid

[sevenperforce]

46 minutes ago, sevenperforce said:

I wonder if the holes at the center of the showerhead will be larger than the holes near the circumference, to create a sort of virtual cone of water. That kind of design might also help relieve internal pressures that could otherwise cause it to expand in the center. 

Looks like some possibility of differently-sized spray holes:

I cracked up when I saw someone calling it a "launch bidet". 

[Hannu2]

1 hour ago, sevenperforce said:

Raptor yeets 650 kg/s of exhaust out the back end at 3,210 m/s. Assuming all the exhaust plumes generally merge under the 10.3-meter base of Starship, that's a dynamic pressure of 3.71 megapascals. Really quite shockingly low if you think about it -- less than the water pressure in the output of your typical coin-operated car wash spray nozzle. The coolant loops in a pressurized water reactor run 4-5x higher.

3.71 MPa is very high pressure if it affects on large surface. Water nozzle has a diameter around 1 mm. Starship has 9 m. Force is proportional to surface area, i.e. square on ratio.

Larger structures able to handle that kind of pressures are very thick walled metal structures. Like gas cylinders, hydraulic cylinders or high pressure parts of powerplants. Concrete is very brittle in those conditions and temperature of exhaust does not make concrete's work easier.

[kerbiloid]

L - Launchpad.

Spoiler

 

[magnemoe]

7 hours ago, JoeSchmuckatelli said:

I suspect the jury is still out on that.   We ran a lot of scenarios up thread - and it's cargo capacity, while impressive for space, is kind of negligible for military operations.  IIRC, it could carry the equivalent of three 40' shipping containers to a safe rear area. 

 

I was thinking orbital missions not P2P, Hubble is an spy satellite pointing outward.  Web is 6.5 meters, so you could expand it no need for the complex mechanism for unfolding, just have an inflatable  trunk who become rigid because of the inflating gas like oxygen  change the material. 

For P2P I say it make more sense to make an updated cargo plane version of something like the  valkyrie supersonic heavy bomber, launch from standard runways, you can refuel in air, cruise at mach 3 and you can air drop bombs, cargo or special forces and fly away. Or all but order is kind of important.  

[darthgently]

Not just heat and pressure, but the low sound frequencies of the pressure waves may also have helped the concrete sonically disassemble.  The sound suppression of the deluge system might help quite a bit with this also

[CatastrophicFailure]

7 hours ago, sevenperforce said:

I wonder if the holes at the center of the showerhead will be larger than the holes near the circumference, to create a sort of virtual cone of water. That kind of design might also help relieve internal pressures that could otherwise cause it to expand in the center. 

Water fountains have been built with higher pressures than this already. King Fahd's Fountain in Jeddah, built in 1985, continuously pumps sea water through a single nozzle at 4.2 megapascals to almost twice the height of the OLT. Building something at slightly lower pressure which fires for only a few seconds should be straightforward despite the much higher flow volume.

Confirmed, SpaceX is building the world’s largest bidet. 

[FleshJeb]

1 hour ago, CatastrophicFailure said:

Confirmed, SpaceX is building the world’s largest bidet. 

Maybe they can finally clean the giant butthole that owns the place.

[kerbiloid]

Probably, it was already asked here, but I can't see.

Did they set this on?

Spoiler

[ x ] Indestructible Facilities

 

And also decreased the debris limit down from 250?

 

Edited May 10, 2023 by kerbiloid

[tater]

4 hours

 

[CatastrophicFailure]

Mildly interesting:

!

 

[Brotoro]

And another booster successfully lands. Nice booster shadow during landing.

[CastleKSide]

On 5/8/2023 at 10:41 AM, sevenperforce said:

Raptor yeets 650 kg/s of exhaust out the back end at 3,210 m/s. Assuming all the exhaust plumes generally merge under the 10.3-meter base of Starship, that's a dynamic pressure of 3.71 megapascals. Really quite shockingly low if you think about it -- less than the water pressure in the output of your typical coin-operated car wash spray nozzle.

Ok so i didnt finish my engineering degree but im not really sure that comparison holds up. Ur considering the system as a constant force. It would be one thing if the flow was consistent but it's decidedly not. The sonic loads resulting from the turbulent mixing of all the raptors are the problem. Water is also incompressable, air is not.. the average pressure may be around 3.71 megapascals but it's not going to be a constant thing. Again, repeated loading with each sound wave.

My guess is ur dealing with a pneumatic jackhammer missing the metal tip more than a car wash.