Space and Science BS Thread

It uses exhaust gas to supply pressure to the tankage. The amount of fuel onboard should not matter in how fully pressed the tanks are. They had some issues where as a quick fix they added some COPVs with helium as well.

 

Exactly, the inner 13 aren’t yet spun up by the OLM supply though that is supposed to end up being the case so the problem might be in the COPV system on board. Lots of prototype issues with both the booster, the tower, and the OLM yet to find and be ironed out. They’re designing much of this on the fly.
I mention max Q not in reference to engine performance but in regards to the structure of the booster when the tanks are partially depleted. I haven’t seen a can crusher test on a fully stacked booster yet, only on individual tank sections. Granted the can crusher rig should be able to simulate the load of everything above against the thrust from below but it’s a semi static test, not dynamic as the real thing will be. This size/shape has never flown so it’s impossible to know what the live stresses will be in order to simulate them.

 

I thought the Boosters had internal bracing in the tanks and transfer tubes after the B7 transfer tube crumpled?

 

I can't help wondering if the SpaceX heavy will ever succeed. The Soviets developed a booster with 30 engines in the first stage and it failed on each of at least 4 launch attempts. The complex plumbing needed to feed all those engines is a major concern- lots of opportunity for water hammer which will cause engines to explode, lots of potential cracks and mechanical failure points.

I expect SpaceX will forge ahead and keep trying until they have 1 success, then declare the system operational. Kind of the hare to NASA's tortoise.

 

That could happen, sure. But this is the Russians you're talking about. In addition, the N-1 was in development in the late 60s and early 70s.

 

The FH has 27 engines….
The Soviets also tried and failed at making a full flow staged combustion engine…

What makes you think they’d be so reckless as to declare operational after one flight? What in their history indicates that?

NASA isn’t gonna put one astronaut on it unless there’s a lengthy track record of success.

 

That would help. It’s all very exciting and way more out in the open than we’ve ever seen before I just don’t know what the actual timeline will be since there hasn’t been any scale up between the hopper and SH and nothing even suborbital using raptor II.

 

They didn’t have the capability to run static fire tests on the whole rocket and were up to the neck in the arms race to boot. Musk has a personal commitment and unless he sees no way forward I don’t see him giving up that easily. As long as Spacex remains privately owned he won’t be pushed aside by a board of directors either. Methane and LOX are well understood and neither is as difficult to handle as Hydrogen. Not as easy as RP-1 but also cleaner burning so no need to worry about coking. They’ve avoided much of the complexity of the mobile launchers by dividing tasks between the more easily constructed towers, ROV crawlers, and the OLM’s. Chopsticks increase that but it still seems way more efficient than the mobile launchers since they also eliminate the need to climb a hill before launch.

 

Unlike NASA Spacex develops by putting something together then trying to fly it with very limited testing. Case in point Starship had several failures before landing successfully. Starship has far fewer engines, yet it took several tries to get it up to 30,000 feet and land. It has yet to go into space, yet to fly at the xtreme speeds required.

 

If you think that all they're doing is building tubes, strapping rocket engines on them, and then trying and fixing failures, you're naive. SpaceX has done thousands and thousands of simulations both digital and small scale, just like NASA does. The REASON that SpaceX moves at speeds so much faster than NASA is that they don't require a committee every time a revision needs to be made.

When NASA makes a revisions to parts I make, the parts sit on the shelf waiting for those revisions for months and months. When SpaceX or rocketlab make a revision we usually have them in under a week.

And yes. Starship has had failures. And falcon 9 had landing failures. Technically however, falcon 9 was originally not designed to land. And here we are, 8 YEARS later and no other company is landing commercial rockets with orbital insertion.

Every starship to fly this far has been using raptor 1 engines and an altitude limit they could not exceed. Not to mention they all left the ground without a booster to get it started like most rockets. But in the end you missed the entire point of their tests, which were to test the aerodynamic drag and control.

 

FIFY

 

It might be better to say that they don’t spend an excessive amount on vehicles that aren’t expected to survive. But it’s also true that the flights were tests in themselves so those should be counted as such and not disregarded. Spacex has had far more to learn to catch up in some areas and break new ground in others and they do it differently. It’s certainly true that they have much more to do to prove the Starship concept flight worthy. It’s hardly even off the ground as various prototypes so all that stuff about high speed and high altitude is true not to mention reentry testing of the bellyflop and heat shield concepts regardless of why that’s so. It’s a remarkable show to watch being so completely different from all other US aerospace companies, I’m certainly enjoying it.

 

I do see what you mean by scale up, but I think Musk would rather spend the money on computer sims to help get the real world product as close as they can to what they believe will work. It's much cheaper and efficient to do that than have 17 different iterations fail and have to scrap the super expensive stainless.

 

I think they learned what they could from those which probably led to raptor II as well as the HLS contract. Not sure if they’d learn much from a half sized booster anyway but now the cost of rapid deconstruction begins to include damage to infrastructure rather than just a spent, poorly welded can. Simulations can’t tell you everything unless your programming is omniscient so they’re going to have to put one up at some point. I just happen to think that point is still a bit farther off. Everything at the launch site is essentially a prototype so it’s not just the engines and flight software now. And no matter how soon they’re ready at Starbase II NASA won’t be letting them launch SH from there until there’s another authorized launch site for crewed ISS support whether that’s crew dragon or some other vehicle, preferably in another state that wouldn’t be at risk from the same weather conditions.

 

This is why they are building a Stage 0 at KSC.

Maybe I'm just impressed with the absolute unit that is Stage 0 at Starbase, but it looks like the structure could survive an RUD of a nearly empty Booster or Ship. If it happens to RUD on the OLM however....

 

Let's put it this way - if EDL doesn't work the first dozen tries, nbd. There's a limit to simulation and sometimes ya just gotta do it live once you have a fair degree of confidence. The problems with raptors so far have been relights. Postulate the first dozen starships as 'expendable' and you're still ahead of SLS (and everyone else), tbh. They have a revenue generating payload (starlinks) that has a fair degree of failure tolerance (if it blows up there's literally an endless stream in production) and pretty much it's a fast moving project anyway. Starship expendable might be more expensive than F9/F9H but there's a ceiling. Now say there's a fatal flaw in the Ship TPS they can't engineer around - it still reduces the cost over F9, until they can redesign it.

Super cheap, you mean - welded together by some water tank welders in texas. The 'expensive' stuff was the carbon fiber they initially tried to go for.

 

Right, but stainless still isn't exactly as cheap as rice.

 

Stainless steel - $3/kg back in 2019..

White Rice - $4.89/kg in Los Angeles 2022

 

I understand that the tests were limited in scope. My point was that it's an enormous leap going from 30,000 feet to orbit. Both the ascent and entry are extremely stressful and the orbital environment poses several challenges of its own. So, for Spacex to succeed in its contribution to Artemis, they have to successfully fly a few starships to orbit and return and that requires the heavy to work. Both are major challenges. Do I hope they succeed? Yes. Do I think they will meet a 2024 or 2026 schedule? Unlikely

 

They’ve done pretty well up there so far. Sending a skeleton up and refueling it in orbit will be quite a feat in itself. After that they’ll need to get one fitted out inside for extended habitation and not for just a short hop to the ISS. The toilet will have to work.