totm nov 2023 SpaceX Discussion Thread

[kerbiloid]

8 hours ago, tg626 said:

Well by standing I mean it existed in the early 60s when these decisions were being made. For the era, ot was probably built to make Jupiter or Redstone rockets or one or more of their brethern. 

Redstone and its modification Jupiter were based on A-4 which had been developed even earlier, and was matching trailer size standards which were defined by railroad standards, to let both trucks and truck cargo fit the railroad transport. As well, the battle tanks of XXI still match the railroad standards of XIX.

8 hours ago, tg626 said:

Thats fine, but the C-5 was choosen based on it being the biggest they could build in an existing factory. They didn't want to loose precious time building a new factory to accodate the larger Nova designs. 

The factory was based on standards developed long before Novas, Saturns, V-2s, and even dinosaurs.

https://en.wikipedia.org/wiki/Albert_Kahn_(architect)
(H. Ford's personal architector.)

The silver bullet of quick industrial construction of early XX. Highly standardized industrial architecture units based on a sequence of standard form factors, which let to develop and build a typical factory in several weeks by combining ready-to-use geometrically compatible units. Allowed to put the building on conveyor, like cars.

The smallest of them was fitting the railroad standards. Bigger ones were fitting the smaller ones.

***

Wherever you go, the Ancient Roman horse width is inevitable, lol.

[RCgothic]

4 hours ago, CatastrophicFailure said:

@sevenperforce

 

 

Two structural engineers on Twitter informed me this structure would act like a boat rising and falling on the tide of the water table. It'd make the whole launch pad super unstable.

4 hours ago, Nuke said:

if they can remove the superstucture as a single piece or in sections that can simplify the process of rebuilding the launch mount.

They can't do that. It took one of the largest mobile cranes in the world to lift the OLM deck up there and they've added too much mass to it since then.

[JoeSchmuckatelli]

4 hours ago, RCgothic said:

They can't do that. It took one of the largest mobile cranes in the world to lift the OLM deck up there and they've added too much mass to it since then

Cabling to the arms of Mechzilla? 

[RCgothic]

Mechzilla has similar capacity to the LR11350 (1350t) crane that installed the OLM table. It's very unlikely that even an LR13000 (1600t) crane could lift it down intact. It's had a lot of mass added to it since it was installed.

Edited April 25, 2023 by RCgothic

[tater]

 

[Kerballlistic07]

Not sure if this has been discussed already, but does anyone know what the next Starship stack will be? I know the booster will be B9, but what ship? I see in some places that Ship 25 is retired, but in other places I don't. Will the next Starship stack be 9/25 or 9/26? Cast your bets now! 

[RCgothic]

I believe B9/S27 are next up, but given likely delays for launch pad reconstruction and upgrades it could easily end up being later prototypes.

We know both are advances on B7/S24.

If they were to skip B9/S27 it would probably be to the next block upgrade, but not sure whether that would be B10/S28 or later.

[sevenperforce]

7 hours ago, RCgothic said:

Two structural engineers on Twitter informed me this structure would act like a boat rising and falling on the tide of the water table. It'd make the whole launch pad super unstable.

Correct -- concrete floats when you least expect it.

[Nuke]

7 hours ago, RCgothic said:

Two structural engineers on Twitter informed me this structure would act like a boat rising and falling on the tide of the water table. It'd make the whole launch pad super unstable.

They can't do that. It took one of the largest mobile cranes in the world to lift the OLM deck up there and they've added too much mass to it since then.

well then, call the welders.

[magnemoe]

15 hours ago, Nuke said:

i dont know. my understanding about reinforced concrete structures is that they are very difficult to repair. if you can get an engineer on the ground to sign off on them, you might be able to use them again, but any damage and you are better off scraping and pouring new ones. however if they are salvageable i can see space-x reusing them. otherwise you are looking at more than 2 months of delays. i wonder if elon had a structural engineer look at things before he made his 1-2 month announcement. 

if they can remove the superstucture as a single piece or in sections that can simplify the process of rebuilding the launch mount. i think it was designed such that any structural steel components were behind blast shields and thus thermally insulated. so long as its not bent or deformed or something you should be able to hammer out most of the dings (sort of like what you would have to do on a naval vessel that saw action). 

I don't think the pillars are damaged past fixing, that would require them getting hit by an large boulder head on. The steel structure are probably also mostly fine. 
Most of the piping has taken an serious beating  and need to be replaced, even if looking intact its hard to know the status inside the ruined insulation.  No idea about the tower systems but guess lots of it also took an beating. 
Luckily the can work upside in the tower and on fixing the hole at the same time. 

[magnemoe]

22 hours ago, JoeSchmuckatelli said:

If they also trench out the spaces between the legs and allow to fill with water (b/c of water table is literally right there) - would that help?  I look at your design and the amount of damage done to the legs themselves and wonder if they don't want to get some of the force into an area below the legs in a way that's not directly blasting everything past them.  Guessing water should reduce some of the energy - although I don't know what happens when it flashes to steam - but I'm guessing there's some measure of dissipation of energy that is going to go the path of least resistance.

Something like this?

(Thanks, MS Paint!)

They definitely need some structure outside of the mount. Musk talked about water cooled steel plate so  I imagine two plates with water in middle or plate with pipes welded on below. Might well be perforated so water come out on top and no chance of over pressure  from boiling water in the void. I would extend this outside a lot like here, either dug down some meters or on surface. 
Might add some jumps at the end to direct flames up in the air and definitely away from the tower.  Water on the surface would be blown away but guess it would be some as they start this cooling system before ignition. 

But an removable pyramid build from parts between launches would probably be to flimsy.  I expect a flat deck, if that don't work they probably add an pyramid. 
Perhaps an separate test stand for superheavy pressure testing who let them work on engines.  Or get in with an cherry picker. 

Edited April 25, 2023 by magnemoe

[CatastrophicFailure]

Interesting read: 

 

 

 

[tg626]

It is interesting. I wonder if "Gagarin's Start" was built with that in mind or just coincidence? I always thought the R7 flame trench looked overly huge (both depth and width), but given this info, perhaps not.

[Jacke]

18 hours ago, tater said:

Combat aircraft have ejection seats not because of performance, but because the risk of catastrophic failure is far higher—because someone else is actively trying to cause catastrophic failure in your aircraft.

I'd actually like to see relative numbers of the number of ejections out-of-combat versus in-combat.  I'd suspect that out-of-combat is greater because these are high-performance aircraft operating much closer to their limits much more often.  Combat aircraft designs also have features like near neutral stability even before computer controls were added, now even moreso with it.  Of course, the high-performance design and its features are because they fly in combat, so even the out-of-combat failures are due to their role demanding that performance.

 

18 hours ago, tater said:

And yeah, Shuttle had effectively no survivable abort options except during incredibly limited parts of a flight.

I've wondered about the real survival chances for the various Shuttle abort modes, even the ejection seats in the first few flights.  There was some revision of them in light of more serious analysis later in the Shuttle's life.  Especially considering that it's now considered that the Gemini ejection seats may have had a low survival chance as well.

 

18 hours ago, tater said:

The point is that unless rockets have air/spaceworthiness at some point demonstrated, humans will only ever go to space as a stunt.

Space rocketry and flight are things that aren't quite like anything else we do, although high-performance combat aircraft come close.  It will develop as its own thing.  There shouldn't be glib talk about becoming just like commercial aircraft flight because that ignores how challenging going to space and performing there is.

I think space travel went far beyond being a stunt through the 1970's and 1980's.  We have a workable system now with two groups of launch vehicles:

• Uncrewed LVs for cargo to orbit (and perhaps for a future vehicle, for return) which balance cost versus accepting a failure rate with work to minimize that failure rate.
• Crewed LVs for human transport which are specialized at greater cost to push that reliability along with launch escape systems and other abort modes to handle when things fail.

Beyond LEO missions are similar in design, though more challenging.  As an example, the original Mars Direct (with first the uncrewed Earth Return Vehicle followed by the crewed Mars Habitat Unit) had abort modes for failures of the MHU that got it back to Earth.

It comes down to the fact that all space rockets and craft are high-performance and push much closer to their limits that common utility craft that operate on Earth.  We desire better performance and safety but these will likely only improve over the current best slowly.  Each new vehicle design is to a degree experimental and should be revised in light of knowledge from their operation.  New LVs and craft for various missions, both evolutionary and revolutionary, should be part of this.  One of the big mistakes of the Shuttle was that revised craft with revised handling wasn't developed in the 1990's.

[tater]

2 minutes ago, Jacke said:

I'd actually like to see relative numbers of the number of ejections out-of-combat versus in-combat.  I'd suspect that out-of-combat is greater because these are high-performance aircraft operating much closer to their limits much more often.  Combat aircraft designs also have features like near neutral stability even before computer controls were added, now even moreso with it.  Of course, the high-performance design and its features are because they fly in combat, so even the out-of-combat failures are due to their role demanding that performance.

Fair enough, I would imagine peacetime ejections are more common since far more hours—but the performance is a function of combat requirements, so if the vehicle didn't need to have pilot survival a thing while actively having harm aimed at them, it would not be as likely to have peacetime harm, chicken and egg

 

2 minutes ago, Jacke said:

I've wondered about the real survival chances for the various Shuttle abort modes, even the ejection seats in the first few flights.  There was some revision of them in light of more serious analysis later in the Shuttle's life.  Especially considering that it's now considered that the Gemini ejection seats may have had a low survival chance as well.

While the SRBs operating, no abort, and given they'd have to eject "forward" to get away on the pad (cause forward there is up), not on the pad, either.

I think the post SRB glide back was to get closer to FL, then eject (and later bail out though the hatch after the seats were removed). The rest I think were all pretty much PR. bottom line is that I think they said the early flights were at ~1:9 for a LOC estimate overall.

 

2 minutes ago, Jacke said:

Space rocketry and flight are things that aren't quite like anything else we do, although high-performance combat aircraft come close.  It will develop as its own thing.  There shouldn't be glib talk about becoming just like commercial aircraft flight because that ignores how challenging going to space and performing there is.

I'm not trying to be glib, I think safe travel to space to and from Earth is shockingly difficult—where "safe" is defined as any level of commercial air travel safety, even historical commercial air travel (safety levels of the 1930s, whatever era you would like to choose). That said, until it's something like that level of safety, space travel, or people meaningfully living/working in space is not a thing.

 

2 minutes ago, Jacke said:

I think space travel went far beyond being a stunt through the 1970's and 1980's.  We have a workable system now with two groups of launch vehicles:

• Uncrewed LVs for cargo to orbit (and perhaps for a future vehicle, for return) which balance cost versus accepting a failure rate with work to minimize that failure rate.
• Crewed LVs for human transport which are specialized at greater cost to push that reliability along with launch escape systems and other abort modes to handle when things fail.

By "stunt" I guess I mean something that a tiny fraction of people would ever be able to do, even if they dearly wanted to. As long as it is something for astronauts, or the fraction of people who can buy their own Dragon flight (or whatever crew vehicle), it's a "stunt" IMO.

 

2 minutes ago, Jacke said:

Beyond LEO missions are similar in design, though more challenging.  As an example, the original Mars Direct (with first the uncrewed Earth Return Vehicle followed by the crewed Mars Habitat Unit) had abort modes for failures of the MHU that got it back to Earth.

It comes down to the fact that all space rockets and craft are high-performance and push much closer to their limits that common utility craft that operate on Earth.  We desire better performance and safety but these will likely only improve over the current best slowly.  Each new vehicle design is to a degree experimental and should be revised in light of knowledge from their operation.  New LVs and craft for various missions, both evolutionary and revolutionary, should be part of this.  One of the big mistakes of the Shuttle was that revised craft with revised handling wasn't developed in the 1990's.

We can keep spending large billions of projects like SLS/Orion, or ESA can work their own gov crew vehicle, but someone needs to push the envelope or people >50 years from now will be having the same conversations. The first Soyuz flight was 56 years ago, and that is still flying. I'd not want my kids to still see an evolved Dragon flying in 56 years.

[StrandedonEarth]

4 hours ago, CatastrophicFailure said:

Interesting read: 

 

 

 

Hmm, yes, I can see how a covered flame trench for several meters would lessen acoustic loads on the rocket

23 minutes ago, tater said:

I'd not want my kids to still see an evolved Dragon flying in 56 years.

Oh, I dunno, they'd be perfectly fine as a station taxi, when the Optimus production line is churning them out...

[tater]

21 minutes ago, StrandedonEarth said:

Oh, I dunno, they'd be perfectly fine as a station taxi, when the Optimus production line is churning them out...

I don't see longevity at the scale of a handful of people in a capsule as a sign of quality, I see it as an abject failure (sorry, Soyuz). I found the Shuttle a failure for the same reason. Knowing it worked, they should have made a new one every few years, really pushing the margin of what was possible, both within the basic design (Shuttle C, etc), and pushing the system harder (flyback booster, etc).

[mikegarrison]

3 hours ago, tater said:

We can keep spending large billions of projects like SLS/Orion, or ESA can work their own gov crew vehicle, but someone needs to push the envelope or people >50 years from now will be having the same conversations. The first Soyuz flight was 56 years ago, and that is still flying. I'd not want my kids to still see an evolved Dragon flying in 56 years.

The first 737 flew 56 years ago, and it's still one of the best-selling, most widely flown airplanes in the world. It's a bit like the Ship Of Theseus, because I'm not sure there is a single part from the original 737s that is still in a new 737, but the airplane is still recognizably a 737.

[kerbiloid]

On 4/25/2023 at 7:08 AM, tater said:

Combat aircraft have ejection seats not because of performance, but because the risk of catastrophic failure is far higher

They have it because they are supersonic. The pilot can't just bail out.

Concorde and Tu-144 were, too. Were.

Starship is supersonic as well.

On 4/25/2023 at 7:08 AM, tater said:

91 in a row with no problems, then crew?

The passenger planes don't fail every 100 flights.

  

9 hours ago, CatastrophicFailure said:

Interesting read: 

 

 

Quote

The problem is when LV sits on the launchpad and exhaust is redirected sideways: sound is directed more towards vehicle.
Yep, contrary to the popular belief, redirecting exhaust flow sideways increases acoustic load on the vehicle

Boca-Chica, three years later.

Spoiler

Proper pit for proper N-1 Starship.

Look! Even Mechazilla is there!

Edited April 26, 2023 by kerbiloid

[AtomicTech]

12 hours ago, tater said:

Knowing it worked, they should have made a new one every few years, really pushing the margin of what was possible, both within the basic design (Shuttle C, etc), and pushing the system harder (flyback booster, etc).

One word: money.

[tater]

5 minutes ago, AtomicTech said:

One word: money.

They got a few billion a year for 30 years.

Also, live in ~20 min:

 

[Royalswissarmyknife]

Just a quick Question when do you think they will start production at Florida for Starship/Superheavy?

[AckSed]

Oh dear, it's a tad foggy.

[Royalswissarmyknife]

Just now, AckSed said:

Oh dear, it's a tad foggy.

Vandenfog

[AckSed]

Man that drone-ship pad is actually rusty.