totm nov 2023 SpaceX Discussion Thread

[tater]

4 minutes ago, Nightside said:

It was already named that when they bought it.

They actually didn't buy it at all, I think. They are hiring it, and it's named for the owner's father, Steven Miguez.

Edited May 22, 2019 by tater

[Ultimate Steve]

26 minutes ago, Nightside said:

It was already named that when they bought it.

They named it after me.

[ThatGuyWithALongUsername]

46 minutes ago, Nightside said:

It was already named that when they bought it.

"Just Read The Instructions," "Of Course I still Love You," and, eventually, "A Shortfall of Gravitas" were not, though. And those names, even though they come from a sci-fi novel series, definitely have, well, a shortfall of gravitas.

[Ricktoberfest]

6 minutes ago, ThatGuyWithALongUsername said:

"Just Read The Instructions," "Of Course I still Love You," and, eventually, "A Shortfall of Gravitas" were not, though. And those names, even though they come from a sci-fi novel series, definitely have, well, a shortfall of gravitas.

As opposed to "Boaty McBoatface" or whatever that ship was. I think some people take themselves way too seriously. Its that kind of institutionalized/traditional thinking that has kept the space race at a walk for the last several decades

[tater]

56 minutes ago, ThatGuyWithALongUsername said:

"Just Read The Instructions," "Of Course I still Love You," and, eventually, "A Shortfall of Gravitas" were not, though. And those names, even though they come from a sci-fi novel series, definitely have, well, a shortfall of gravitas.

I love the Culture naming scheme, and much prefer "BFR" to Starship or Super Heavy.

[CatastrophicFailure]

Yay! 

 

Eek. 

 

 

[sh1pman]

Quote

Absent any court actions to reverse the LSA decision, says the complaint, “SpaceX will suffer the irreparable harm of being deprived of the opportunity to compete fairly.” Because of the flawed and biased treatment of SpaceX, the company will suffer “substantial competitive harm” in the final phase of this procurement, the Phase 2 competition.

 

[CatastrophicFailure]

3 hours ago, Meecrob said:

Edit: its 2019...Look at your username...and mine...and everyone elses...its all stupid silly names.

Yeah but I can pretty much guarantee no one will ever use mine. 

Also:

 

For comparison, the largest Diesel engine in the world, powering a container ship, is about 109,000hp...

[tater]

 

[tater]

Back to vacuum Raptor!

 

[tater]

Vacuum Raptor makes a huge difference. It means that LEO--->Lunar Surface and back to Earth is possible with 85 tonnes of Starship, plus ~35t of cargo (some of which might really be landing propellants). If 85t dry includes a crew component, that's impressive.

Looks like Vacuum Raptor must have turned out easier than expected. I bet the June 20 info is pretty interesting, and we might well see some hardware flying (hopper) in the next several days.

 

[Val]

Moved an interesting, but off-topic discussion to it's own thread.

 

[sh1pman]

4 hours ago, tater said:

Vacuum Raptor makes a huge difference. It means that LEO--->Lunar Surface and back to Earth is possible with 85 tonnes of Starship, plus ~35t of cargo (some of which might really be landing propellants). If 85t dry includes a crew component, that's impressive.

Looks like Vacuum Raptor must have turned out easier than expected. I bet the June 20 info is pretty interesting, and we might well see some hardware flying (hopper) in the next several days.

It should also bring LEO payload back to 150t.

[magnemoe]

Ok 6 engines I assume this will be three engines in the center and the vacuum ones out towards the sides like on the first version but now down to 3 vacuum over 4 and three sea level in middle. 

 

[sh1pman]

18 minutes ago, magnemoe said:

Ok 6 engines I assume this will be three engines in the center and the vacuum ones out towards the sides like on the first version but now down to 3 vacuum over 4 and three sea level in middle. 

3 vacuum Raptors generate thrust of about 5.7 MN. Fully fueled Starship is about 1100t.That gives a TWR of about 0.5 after booster separation. Isn’t that too low for manned flights? F9 S2 TWR is close to 1 at stage sep.

[tater]

 

Edited May 23, 2019 by tater

[AVaughan]

29 minutes ago, sh1pman said:

3 vacuum Raptors generate thrust of about 5.7 MN. Fully fueled Starship is about 1100t.That gives a TWR of about 0.5 after booster separation. Isn’t that too low for manned flights? F9 S2 TWR is close to 1 at stage sep.

I think they will use all 6 engines after stage separation, then shutdown the sea level Raptors once they are no longer needed.  (I believe that was the plan back when they had a 4/2 split).

[tater]

3 minutes ago, AVaughan said:

I think they will use all 6 engines after stage separation, then shutdown the sea level Raptors once they are no longer needed.  (I believe that was the plan back when they had a 4/2 split).

Yeah, there is no reason why they have to run just the vac engines, they can run whatever they need. They could also just run the SL engines for a short burn, then switch to vac.

[sh1pman]

13 minutes ago, tater said:

Yeah, there is no reason why they have to run just the vac engines, they can run whatever they need. They could also just run the SL engines for a short burn, then switch to vac.

At the altitude where stage sep happens, SL engines are hugely underexpanded, it’s a waste of efficiency. Payload mass will drop. I think 7 engine config (4 Vac + 3 SL) is the way to go.

[tater]

2 minutes ago, sh1pman said:

At the altitude where stage sep happens, SL engines are hugely underexpanded, it’s a waste of efficiency. Payload mass will drop. I think 7 engine config (4 Vac + 3 SL) is the way to go.

Using all SL Raptors was a waste of efficiency as well (which was the plan as we knew it until yesterday). With spark ignition (infinite relights), I see no reason not to do what they need to to make the launch profile they want (with crew), then add the vac engines at some point in the burn, burn both types at once, whatever. Say they light all 6, then after a few seconds shutdown the SL engines when the trajectory is shaped correctly for crew.

Yeah, they lose some margin, but for tanker flights, they might use the vac engines alone. We'll see.

[sh1pman]

3 minutes ago, tater said:

Yeah, they lose some margin, but for tanker flights, they might use the vac engines alone. We'll see.

Yes, tanker flights are most strongly affected by this. 150t vs 100t to LEO means that 33% fewer tanker launches are needed to refuel a Starship.

[tater]

2 minutes ago, sh1pman said:

Yes, tanker flights are most strongly affected by this. 150t vs 100t to LEO means that 33% fewer tanker launches are needed to refuel a Starship.

Yeah, I'm dubious about crew launches for quite a while (ie: uncrewed first many times). So they can use 0.5 TWR for cargo (many upper stages do this or lower).

It;s also important to realize that crew trajectories are shaped with abort constraints in mind.

They don't want the trajectory such that after LES is used the g-load on the capsule is too high. With Starship the abort profile is different (or non-existent depending on how you look at it). Not sure that it's a factor.

 

[Elthy]

Dont forget that Starliner has a very low TWR with its Centaur upper stage, too. 2. Stage+Starliner are about 38t while two RL10 engines deliver about 200kN of thrust, so the TWR ist also close to 0.5...

[Spaceception]

I feel this is a pretty big thing to miss

Made ~1 day ago 

And this 

I don't think I agree with this, but I can see why you wouldn't do it now. On Mars, you can branch out smaller habitats, and have direct access to resources. For this, you would have to build either smaller rotating habitats, and/or wait to build 1 really big habitat later. But you would need to carry everything up first, rather than just building on the surface. But this is most likely the long term goal for BO, and for now, their focus is likely on the Moon. So by the time they start, this should make a lot more sense.

Edited May 23, 2019 by Spaceception

[tater]

15 minutes ago, Spaceception said:

I feel this is a pretty big thing to miss

Made ~1 day ago 

Well, the road closures May 28/29 at Boca Chica were posted up the thread, so we knew that hopper was supposed to fly on those dates.

 

15 minutes ago, Spaceception said:

 

And this 

I don't think I agree with this, but I can see why you wouldn't do it now. On Mars, you can branch out smaller habitats, and have direct access to resources. For this, you would have to build either smaller rotating habitats, and/or wait to build 1 really big habitat later. But you would need to carry everything up first, rather than just building on the surface. But this is most likely the long term goal for BO, and for now, their focus is likely on the Moon. So by the time they start, this should make a lot more sense.

I think Bezos is right here. Both concepts are predicated on far cheaper access to space, and for large payloads. So for the colony idea, treat that as a given (Starship like, or greater payloads to LEO at prices that rival the cost to FedEx something overnight per kg). Also, human spaceflight down to airline level costs (maybe 1st class RT level, but that order of magnitude).

With those given, moving asteroids is a thing. That solves the materials issue for orbital habitats. Either way, each requires that humans live in 100% built environments. Equatorial LEO beats the Mars surface for radiation protection because Earth has a magnetic field (though the GCR threat is fundamentally the same). The solution at Mars is obviously straightforward (bury habs), whereas orbital colonies have to drag that regolith to the station.

I don't see a colonization path that makes economic sense for either, however.