totm nov 2023 SpaceX Discussion Thread

[sevenperforce]

1 minute ago, RealKerbal3x said:

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.

The question is whether running all six Raptors at full throttle at MaxQ would produce a thrust be greater than the magnitude of aerodynamic drag.

I feel like it would be?

[RealKerbal3x]

1 minute ago, sevenperforce said:

The question is whether running all six Raptors at full throttle at MaxQ would produce a thrust be greater than the magnitude of aerodynamic drag.

I feel like it would be?

Maybe? You do have to take into account how massive Starship is when full of propellant, though. Isn't it like 1200 tons fully loaded?

[Spaceman.Spiff]

1 minute ago, RealKerbal3x said:

Maybe? You do have to take into account how massive Starship is when full of propellant, though. Isn't it like 1200 tons fully loaded?

Could it emergency vent and fire the engines at the same time?

[YNM]

26 minutes ago, sevenperforce said:

The question is whether running all six Raptors at full throttle at MaxQ would produce a thrust be greater than the magnitude of aerodynamic drag.

I feel like it would be?

My real question honestly is more with whether Starship itself is designed beyond the MaxQ - running away from the booster at MaxQ exposes you to higher forces than MaxQ. Capsules are small simple things but an entire thing with whole engines and cylindrical fuel tanks and flaps under it is not that practical IMO.

Still betting that the crew compartment will have to be deployable if we want to assume worst-case scenario... Using the rest of the rocket as crumple zone (granted with explosives in it) perhaps we could get away with something that's barely running away from the rest of the rocket. In Challenger Accident the cockpit (crew compartment ? crew cabin ?) actually remained intact all the way to landing, but there was nothing to slow it down.

Either that or extremely reliable design that means it's more like an aircraft than any rocket that came before it.

Edited May 20, 2021 by YNM

[SpaceFace545]

1 minute ago, YNM said:

Either that or extremely reliable design that means it's more like an aircraft than any rocket that came before it.

But it isn't. Its a rocket. A tiny payload strapped to a couple thousand tons of highly explosive gases. I don't care if this flies every single day, a single error would destroy the entire rocket. Its not like a plane that can "glide back" in an engine out scenario or even fly with portions of it's wings ripped off. Even a single bolt coming undone has a strong possibility to shred it. And if the goal is "Rapid Reusability" then we can be prepared to see some catastrophic failures resulting in the tragic loss of life for the entire crew just because of ground crew oversight when they failed to tighten that nut.

[Spaceman.Spiff]

1 minute ago, SpaceFace545 said:

But it isn't. Its a rocket. A tiny payload strapped to a couple thousand tons of highly explosive gases. I don't care if this flies every single day, a single error would destroy the entire rocket. Its not like a plane that can "glide back" in an engine out scenario or even fly with portions of it's wings ripped off. Even a single bolt coming undone has a strong possibility to shred it. And if the goal is "Rapid Reusability" then we can be prepared to see some catastrophic failures resulting in the tragic loss of life for the entire crew just because of ground crew oversight when they failed to tighten that nut.

Which is why it won’t operate with crew for a loooooooooooooong time. 

[YNM]

7 minutes ago, SpaceFace545 said:

But it isn't. Its a rocket. A tiny payload strapped to a couple thousand tons of highly explosive gases.

So ? Have you seen the B777 that had it's engine exploded and it remained flying ?

You only have to safeguard against catastrophic failures. Make sure you shut things down rather than explode it. Make sure the control is a lot more reliable than anything else.

Now yes we'd probably never reach airliner safety. But ejection seat actually still comes with a chance of injuries at minimum and death at maximum if you ever have to use it. There's a good reason why the average civilians don't fly fighter jets all the time (other than that they don't know stuff). But if you want to be arranged for (or is arranged to) a flight with one ? That exists, albeit a very tiny chance.

Edited May 20, 2021 by YNM

[RealKerbal3x]

2 minutes ago, SpaceFace545 said:

But it isn't. Its a rocket. A tiny payload strapped to a couple thousand tons of highly explosive gases. I don't care if this flies every single day, a single error would destroy the entire rocket. Its not like a plane that can "glide back" in an engine out scenario or even fly with portions of it's wings ripped off. Even a single bolt coming undone has a strong possibility to shred it. And if the goal is "Rapid Reusability" then we can be prepared to see some catastrophic failures resulting in the tragic loss of life for the entire crew just because of ground crew oversight when they failed to tighten that nut.

Aircraft are rapidly reusable, and they have certainly had tragic losses of life because of ground crew error. 

With the volume of flights planned, these things are bound to happen. They just have to make those events as improbable as possible, and the best way to do that is just fly a load of times and fail a load of times before they put crew on it.

[tater]

11 minutes ago, SpaceFace545 said:

But it isn't. Its a rocket. A tiny payload strapped to a couple thousand tons of highly explosive gases. I don't care if this flies every single day, a single error would destroy the entire rocket. Its not like a plane that can "glide back" in an engine out scenario or even fly with portions of it's wings ripped off. Even a single bolt coming undone has a strong possibility to shred it. And if the goal is "Rapid Reusability" then we can be prepared to see some catastrophic failures resulting in the tragic loss of life for the entire crew just because of ground crew oversight when they failed to tighten that nut.

If it flies 270 times in a row with no catastrophic failures, it then meets the Commercial Crew 1:270 LOC requirement. They can also get to that level without flying, but by demonstrating the reliability using the math that rocket manufacturers use for that purpose. SLS/Orion has such a rating, and it has never flown.

If an airliner has the V-stab fall off, everyone dies (AA flight 587). Some failures are not recoverable.

A SS could presumably still land if an engine blew up. I'm not one that sees SS reaching even commercial crew safety levels for a while.

31 minutes ago, sevenperforce said:

The question is whether running all six Raptors at full throttle at MaxQ would produce a thrust be greater than the magnitude of aerodynamic drag.

TWR looks to be >1, but pretty low.

 

[YNM]

17 minutes ago, tater said:

TWR looks to be >1, but pretty low.

Would you need TWR larger than 1 or is it larger than the TWR of the booster at the time of MaxQ (or anytime an abort have to be executed) ?

Will say that if the failure results merely in the shutdown of the engine then that's potentially still better than the non-killable SRBs of the Shuttle. Not sure in what scenario would one see the booster engines continue to be on honestly, except for aero/structural failure (which would've stemmed from control failure, as aero fails are most likely due to unusual attitude/situation).

Edited May 20, 2021 by YNM

[RealKerbal3x]

An important point here is that if we can't shift the paradigm from 'rockets fly infrequently and are dangerous and expensive' (as they have been for much of their existence) to 'rockets fly often and are safe and cheap', we're not really going anywhere in space as a species.

[YNM]

5 minutes ago, RealKerbal3x said:

'rockets fly often and are safe and cheap', we're not really going anywhere in space as a species.

erm... we actually stockpiled them around during the cold war, and that was the way they intended to end the world as we knew it XD

[RealKerbal3x]

2 minutes ago, YNM said:

erm... we actually stockpiled them around during the cold war, and that was the way they intended to end the world as we knew it XD

Well that sounds like just about the least safe way you could use a rocket

[StrandedonEarth]

2 hours ago, YNM said:

erm... we actually stockpiled them around during the cold war, and that was the way they intended to end the world as we knew it XD

[magnemoe]

1 hour ago, RealKerbal3x said:

Well that sounds like just about the least safe way you could use a rocket

ICBM are also not known for being super reliable, its an weapon system after all, the launch platform could be destroyed before launch, it could be shot down or miss or system might be outdated so it was no need to gold plate them they you could instead build more. 
They was also not tested in huge number compared to popular orbital rockets. 

Most of the early orbital rockets had an ICBM origin, for stuff like Titan and Soyuz improved on the orbital part while ICBM moved on to hypergolic or solid fuel as they need to be stored for decades. 
 

1 hour ago, RealKerbal3x said:

An important point here is that if we can't shift the paradigm from 'rockets fly infrequently and are dangerous and expensive' (as they have been for much of their existence) to 'rockets fly often and are safe and cheap', we're not really going anywhere in space as a species.

Agree, however the power levels involved in orbital rockets makes it dangerous, seems hard to get it safer than an reliable fighter jet who is a lot safer than 1:270 LOC or combat operations and dangerous ones not routine ones. 
And you have the starship landing or the dangerous part. Honestly I say they should work on an abort system, primary for the landing and for faster human rating of starship. 

On the other hand starship has the option to abort an cargo flight, yes its a bit risky but assume superheavy fails in an way who does not damage starship. you then seperate, do an boostback do an powered decent to burn off fuel before landing.
Spaceship also has an abort to orbit option, if it uses up its landing fuel it can get more fuel from another starship for reaching higher orbit, deploy payload and land. 
This is also an way to increase the cargo to orbit limit. 
 

[magnemoe]

11 minutes ago, StrandedonEarth said:

And all KSP players know the issues with this plan , they was ballistic missiles with an limited range of less than half the diameter of earth, they could not reach orbit and hitting the sun is hard, moon is much easier but also harder than orbit. Yes ICBM has been used for orbital missions but with smaller payloads. 

[cubinator]

10 minutes ago, magnemoe said:

And all KSP players know the issues with this plan , they was ballistic missiles with an limited range of less than half the diameter of earth, they could not reach orbit and hitting the sun is hard, moon is much easier but also harder than orbit. Yes ICBM has been used for orbital missions but with smaller payloads. 

I interpret it as them deciding that it is worth the additional effort to build bigger rocket boosters capable of reaching the Sun, because that is the only appropriate place to dispose of the bombs.

[Deddly]

Is this thread about SpaceX or what? 

[tater]

18 minutes ago, Deddly said:

Is this thread about SpaceX or what? 

Most days we see actual news, it's been slow after SN15. Sorta.

Supposedly a road closure tomorrow...

Could be SN15 related, or maybe they will move the new integration tower segments to the pad to install them?

 

[Beccab]

Just now, tater said:

Most days we see actual news, it's been slow after SN15. Sorta.

Supposedly a road closure tomorrow...

Could be SN15 related, or maybe they will move the new integration tower segments to the pad to install them?

 

Doubt we will see anything with SN15 until they move the new crane, the massive one

[YNM]

1 hour ago, magnemoe said:

ICBM are also not known for being super reliable, its an weapon system after all, the launch platform could be destroyed before launch, it could be shot down or miss or system might be outdated so it was no need to gold plate them they you could instead build more. 
They was also not tested in huge number compared to popular orbital rockets. 

I think it's kind of a dilemma. At one point we clearly had like hundreds of them lying around, and hypergolic and solid fuel was the 'stupid cheap' way to get reliability.

That's why even if it was an off comment (sorry moderators !) I think it's interesting to see that the 'cheap' stuff we do now (assuming Starship is cheap, so LCH4/LOX) is actually a lot more 'safe' per se than what it used to be (you can't store cryogenic forever w/o pressure rise or cooling... yet...)

Edited May 20, 2021 by YNM

[tater]

 

[JoeSchmuckatelli]

1 hour ago, magnemoe said:

hitting the sun is hard

Biggest thing in the solar system, and one of the hardest to hit.

So - is it easier to use Jupiter or Venus to get your garbage tug to hit the sun ?

[CatastrophicFailure]

1 hour ago, cubinator said:

boosters capable of reaching the Sun, because that is the only appropriate place to dispose of the bombs.

If the computer had any sense, it would send them to go nuke Mars (easier to reach anyway), also more likely since any such computer would clearly be the result of AI merging with Elon’s Neuralinked consciousness. 
there, I made it on topic, happy?

[StrandedonEarth]

8 hours ago, Deddly said:

Is this thread about SpaceX or what? 

Yeah, sorry...

Spoiler