totm nov 2023 SpaceX Discussion Thread

[JoeSchmuckatelli]

15 minutes ago, sevenperforce said:

I feel like something along these lines could work well.

Big steel "dance floor" hung from the legs, so that they can still service the booster from underneath. Three giant steel triangles on hydraulics that translate inward and outward and fold up and down.  

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!)

[kerbiloid]

48 minutes ago, tg626 said:

was dictated by the size of a standing factory.

And what had dictated the size of the standing factory?

[tater]

53 minutes ago, sevenperforce said:

Big steel "dance floor" hung from the legs, so that they can still service the booster from underneath. Three giant steel triangles on hydraulics that translate inward and outward and fold up and down.  

That's pretty cool.

[darthgently]

One thing I can state with near 100% certainly: The 540 degree booger flick maneuver will never be used on a human rated Starship. 

But it may end up useful in cargo launches with appropriate payload.   I mean the booster has to turn around anyway and it is a very long lever, so I can fully understand an intense desire to at least try it once.   

If I were a doubledigit+ rocket billionaire I'm about sure I could not resist the temptation to try it once the idea had been floated

[K^2]

29 minutes ago, tater said:

a ditch in the Pacific is not likely a survivable event

It sucks that depending on weather conditions it can be a dice roll even under perfect execution by the pilots, sure, but even so, I'll take a slim chance over none. The psychological factor of that should not be undervalued. People aren't always rational. Perceived safety is more important than actual for this to work from the business standpoint. It's unlikely you'll have people trusting the space flight is safe if you don't make it so in fact, but that's not in itself sufficient.

34 minutes ago, tater said:

VTHL is a nonstarter for civlians

I disagree. You can always pivot the passenger seats. I would expect orientation consistent with HL to be more viable for longer flights as well. If you're going to coast to Mars, you better have something more convenient than Starship's HT orientation for the passengers. Ideally, I would expect a horizontal arrangement of rows and a tethered counterweight several kilometers away providing for centrifugal gravity on board.

But that's just one more thing that Starship isn't built for. So it's kind of an academic discussion, I guess.

[Ultimate Steve]

3 minutes ago, darthgently said:

One thing I can state with near 100% certainly: The 540 degree booger flick maneuver will never be used on a human rated Starship. 

But it may end up useful in cargo launches with appropriate payload.   I mean the booster has to turn around anyway and it is a very long lever, so I can fully understand an intense desire to at least try it once.   

If I were a doubledigit+ rocket billionaire I'm about sure I could not resist the temptation to try it once the idea had been floated

There (likely) is no 540 degree flip, just 180. The 540 was (likely) a misunderstanding of the description.

[darthgently]

3 minutes ago, Ultimate Steve said:

There (likely) is no 540 degree flip, just 180. The 540 was (likely) a misunderstanding of the description.

But a 180 would toss it retrograde.  360 would leave the booster facing the wrong way.  That is why the 540 seemed somewhat plausible to me (though much higher up in much thinner air where we saw it).

I've seen diagrams showing separation early in the rotation as the booster is < 45 degrees AoA which could make sense also, but not much of a toss; more of a controlled shearing 

 

[FleshJeb]

Disclosure yet again, I'm a civil engineering/land surveying technician without a degree and licensure--I'm making some minimally-educated guesses here. I happen to have some rudimentary understanding of adjacent disciplines because I have to communicate with them and produce work that interfaces with theirs. I also have to collect much of the data they need before they can start, and then translate their finished product back on to the ground to be built.

8 hours ago, Exoscientist said:

   Thanks. That’s very relevant because of the ground water issue at Boca Chica. Another relevant question is how much total weight had to be supported, bridge plus cars?

No recollection, I didn't design it, I just studied the structural plans so I could show them where to build it per the design. Structural engineering above a certain scale is usually dominated by "live load" rather than "dead load". This means wind, water, or seismic forces are going to set the minimums for the design. (On this one, the water forces vastly exceeded everything else--which is why it was $5M to build rather than $500K.) It's also why bridges and buildings can sustain significant structural damage and remain serviceable for a long time when not experiencing extreme conditions. I'm not even going to speculate on what magnitudes of loads that rocket blast imparts, but I bet it's fun!

9 hours ago, JoeSchmuckatelli said:

@FleshJebCan they repair the table in the condition it's in?  Enough to put some kind of diverter system in and try again in a reasonable time?

The only limiting factor in engineering is money. My bridge project took two years of intermittent construction work, because public infrastructure is typically very cost-focused. People are making a lot of jokes about free digging, but the site cleanup and prep alone could easily be a month. See my diagram below, but I think those big horizontal tubes are post-tensioning ducts, and the cables in them are shot. There might be easy access to the end anchors, or they might have to jackhammer them out and find a way to bond new ones in to the structure.

If the piles or caps took flame damage, they'll have to support the structure on some falsework, cut out the damaged portion, and find a way to splice new rebar and concrete in.

One of the things that confuses me about this image is that while there's a fair amount of steel on the ground, there should be a web of rebar thick enough to walk on in that hole. It can't all have vaporized or blown into the ocean, so maybe they went really cheap on the reinforcement.

Absolute bare minimum time with on-call engineers and construction crew might be four months. Tying rebar cages takes time, even if you prefab them offsite, and concrete takes 28 days of curing to meet design strength, and they can't do this all in one pour. Six months would still be a rush job. (Of note, I'm renowned for underestimating time, so you could double these numbers and not be unreasonable.)

EDIT: This is in the neighborhood of a $10M repair, I'd be willing to believe $15M-$20M of effort for a rush job and premium prices on materials. Anything much less than that is a lie or involves chattel slavery.

Just by way of illustration, this is what the site might look like partway through the repair process. All those steel beams and wood are temporary, and take a long time to set up (and are done in a fairly precise manner).

Spoiler

 

Edited April 24, 2023 by FleshJeb
COSTS

[Ultimate Steve]

25 minutes ago, darthgently said:

But a 180 would toss it retrograde.  360 would leave the booster facing the wrong way.  That is why the 540 seemed somewhat plausible to me (though much higher up in much thinner air where we saw it).

I've seen diagrams showing separation early in the rotation as the booster is < 45 degrees AoA which could make sense also, but not much of a toss; more of a controlled shearing 

 

There was a gif a few pages back that showed it. Booster first turns to about -45 degrees, then comes back to 0 degrees (engine cutoff here), ship gets yeeted and ignites it's engines and corrects at about 45 degrees. Booster continues on to 180 degrees.

[tg626]

2 hours ago, kerbiloid said:

And what had dictated the size of the standing factory?

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. 

Now if you are angleing at tye factory matched the rockets abd the rockets matched the railroads or aircraft or barges etc. 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. 

[RCgothic]

New pad for SX at Vandenberg.

 

 

[AtomicTech]

18 hours ago, FleshJeb said:

I have nothing nice to say about it.

Well, wasn't the LEGO set neat? 

1 hour ago, RCgothic said:

New pad for SX at Vandenberg.

 

 

Fingers crossed that this will continue to remain a reusable launchpad.

[Nuke]

13 hours ago, JoeSchmuckatelli said:

@FleshJebCan they repair the table in the condition it's in?  Enough to put some kind of diverter system in and try again in a reasonable time? 

 

depends on how much damage the structural components took. the upper steel superstructure may be easy to take down and inspect but if your pilings are fractured, you got a problem. id hate to see the rocket topple during stacking. so at minimum they will need to break down and inspect the superstucture and pour new pilings, and put in the deluge system while they are at it. 

[JoeSchmuckatelli]

8 minutes ago, Nuke said:

depends on how much damage the structural components took. the upper steel superstructure may be easy to take down and inspect but if your pilings are fractured, you got a problem. id hate to see the rocket topple during stacking. so at minimum they will need to break down and inspect the superstucture and pour new pilings, and put in the deluge system while they are at it. 

My concern was the pilings themselves - if the base structural components are compromised... can such a thing be fixed/ patched?

[CatastrophicFailure]

@sevenperforce

 

 

[Nuke]

45 minutes ago, JoeSchmuckatelli said:

My concern was the pilings themselves - if the base structural components are compromised... can such a thing be fixed/ patched?

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). 

Edited April 25, 2023 by Nuke

[FleshJeb]

38 minutes ago, Nuke said:

depends on how much damage the structural components took. the upper steel superstructure may be easy to take down and inspect but if your pilings are fractured, you got a problem. id hate to see the rocket topple during stacking. so at minimum they will need to break down and inspect the superstucture and pour new pilings, and put in the deluge system while they are at it. 

I'm actually presuming the piers have most of their original strength. The above-ground portions were steel-jacketed--They're fine.

I have to revise my earlier estimate and say this is the equivalent of a seismic retrofit. They can jacket the existing piers with more concrete and rebar, and add some shear structures between them if necessary. Any post-tensioning cables can go outside all that. So we're down to 2-3 months and $5M.

[tater]

 

9 minutes ago, FleshJeb said:

So we're down to 2-3 months and $5M.

Is the 2-3 months related to cure time on the concrete to reach full properties?

[sevenperforce]

1 hour ago, CatastrophicFailure said:

@sevenperforce

 

 

Interesting reversal of my idea. 

[JoeSchmuckatelli]

I must have missed it - but I don't recall seeing the water deluge system going off before launch.

Did it?

[Jacke]

13 hours ago, tater said:

This is just wrong-headed. While I think that early versions should certainly have a LES of some form, given the goal, it simply impossible. Either human spaceflight becomes reliable enough that LES is unnecessary, or humans never leave Earth as more than a stunt.

F-22s have ejection seats. 787s don't.

The 787 doesn't need ejection seats because it's not a high-performance combat aircraft.  It's the culmination of a century of utility aircraft design that has evolved and improved.  It's built reasonably ruggedly so that total airframe failure possibility is miniscule.  There are 2 pilots, 2 engines, and other redundancies so that even when having failures, performance degrades slowly.  And if both engines fail, the aircraft can still glide and have a chance of landing with minimal injuries.

Launch vehicles are all high-performance and the tasks demanded of them push all of them close to their limits.  Reliability and performance can't be wished into being but must be designed, tested, and measured to see what is reality.  The best LVs still have a major abort rate of around 1%.  Failures often lead to rapid and serious performance degradation and aborts.  It doesn't matter what is wanted, it's what can be achieved.  And new designs of radical departure are test vehicles and not at all likely to be optimal.  These are all the problems that the Shuttle had and I would think it was a solid enough lesson not to repeat its mistakes.

The rest of your post you nitpick but it comes down to this:  Is it realistic engineering and operations?  Clean slate doesn't matter because the challenges remain the same.  A different approach still has to deal with the same challenges.  Use the painful lessons and the basics of the subject matter, plan, prepare, practice, perfect, in war or rocketry.  Short-cuts are gambles and need to be limited.  Gamble enough at bad odds leads to failure.

I've watched this all happen since Gemini 12.  Things evolve facing great challenges and demand care, attention, and knowledge of the field to make the right choices.  Giving in to hubris in war and rocketry kills.

[tater]

2 hours ago, Jacke said:

The 787 doesn't need ejection seats because it's not a high-performance combat aircraft.  It's the culmination of a century of utility aircraft design that has evolved and improved.  It's built reasonably ruggedly so that total airframe failure possibility is miniscule.  There are 2 pilots, 2 engines, and other redundancies so that even when having failures, performance degrades slowly.  And if both engines fail, the aircraft can still glide and have a chance of landing with minimal injuries.

The point is that the reliability in the case of aircraft is airworthiness. The same aircraft (individuals and of a type) have flown many thousands of hours. The same engine types have operated for millions of hours, so the chance of failure is well understood. Airline travel when I was a kid (60s and 70s) was safe, but not nearly as safe as now. So a dual engine failure hundreds of miles from land is understood to be extremely unlikely—none the less, it is nonzero, and depending on the route, 0% survivable (high latitude sea states are not easy to ditch in, and even if you did, everyone is dead within minutes anyway of hypothermia).

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.

The point is that unless rockets have air/spaceworthiness at some point demonstrated, humans will only ever go to space as a stunt. And yeah, Shuttle had effectively no survivable abort options except during incredibly limited parts of a flight.

 

2 hours ago, Jacke said:

The rest of your post you nitpick but it comes down to this:  Is it realistic engineering and operations?  Clean slate doesn't matter because the challenges remain the same.  A different approach still has to deal with the same challenges.  Use the painful lessons and the basics of the subject matter, plan, prepare, practice, perfect, in war or rocketry.  Short-cuts are gambles and need to be limited.  Gamble enough at bad odds leads to failure.

Clean slate does matter. We didn't pick the best standards to codify as "the" way to make rockets—I'd argue that Shuttle/SLS are a prime example. The approach learned was what? Put your rocket parts in all 50 states? Following the tried and true designs means small capsules. Forever, apparently. 20 years from now a new 100% reusable VTVL design appears—did they not read the memo to not take shortcuts? Better ditch it and build another capsule I guess.

And "clean slate" is relative. Many of the basic concepts here were talked about in the 60s (Stoke is somewhat closer to many of those). Had some been tried back then, they would have blown up some rockets, and we'd marvel at the old footage of failures, then maybe success.

In this case failures don't matter. They're not putting people on this any time soon (not from/to Earth), and their model is probably not to bother until they've flown many, many times. If they flew 10 uncrewed successes in a row, then flew people? Still safer than STS-1. 68 uncrewed in a row? Safer than Shuttle loss rate. 91 in a row with no problems, then crew? Safer than Shuttle was considered at the end of the program.

Edited April 25, 2023 by tater

[FleshJeb]

2 hours ago, tater said:

Is the 2-3 months related to cure time on the concrete to reach full properties?

Site evaluation, design and calcs for the retrofit, prepping the site, formwork, and then pouring concrete. After the cure they can backfill, compact and start working on the slab. All those steps take time, and you can only fit so many men and machines in that hole. They might only be able to get two excavators working concurrently, and they have thousands of cubic yards of material to move. Remember they have to make the hole bigger and get it controlled before they can make it smaller again. I've worked on a few landslide repairs, and they have to pull out ALL the loose stuff and then some.

This is all assuming that everyone and everything they need is on-call and working overtime.

Edited April 25, 2023 by FleshJeb
lulz

[tater]

1 hour ago, FleshJeb said:

This is all assuming that everyone and everything they need is on-call and working overtime.

They seem to work 3 shifts.

[Beccab]

6 hours ago, RCgothic said:

New pad for SX at Vandenberg.

 

 

Sounds like the VIF problem solved itself, lol