totm nov 2023 SpaceX Discussion Thread

[tater]

Ithacus had this 4 man escape pod. I'd think that the very top of a crew BFS could be a capsule. Ideally it would have a heatshield pass-through hatch, so that there could be a crew compartment below that was more extensive. Crew would ride in the escape cockpit during liftoff and reentry.

[magnemoe]

2 minutes ago, tater said:

Ithacus had this 4 man escape pod. I'd think that the very top of a crew BFS could be a capsule. Ideally it would have a heatshield pass-through hatch, so that there could be a crew compartment below that was more extensive. Crew would ride in the escape cockpit during liftoff and reentry.

I agree, the lack of the LES is an issue, second stage problems and landings will be an total loss. 
I would use an pretty simple LES, not much of an heat shield, not able to deorbit, chance of fail in the late stage is pretty low,  if you reach orbit you send an rescue mission.
During reentry I don't think LES is very useful i think, trying to separate during deorbit will be very hard in any case. Now landing is dangerous and here an LES would be very useful. 
 

[DAL59]

4 hours ago, tater said:

 

Wait... if they can fish them out of the water, do they really need the net?  I know there's corrosion, but the fairings would be in the water for only a few minutes, right?

[IncongruousGoat]

1 minute ago, DAL59 said:

Wait... if they can fish them out of the water, do they really need the net?  I know there's corrosion, but the fairings would be in the water for only a few minutes, right?

Only a few minutes is still enough to cause damage. Remember, this is space hardware. Even a small amount of saltwater corrosion could easily be enough to ruin a fairing. Plus, the ocean isn't always going to be calm enough for the fairings to be able to float without being sunken by rough seas.

[sevenperforce]

6 minutes ago, DAL59 said:

Wait... if they can fish them out of the water, do they really need the net?  I know there's corrosion, but the fairings would be in the water for only a few minutes, right?

My guess is that splashdown is splashy enough to spray water all over the sensitive insides.

[sh1pman]

Will SpaceX try to save the fairing after Hispasat launch?

[sevenperforce]

28 minutes ago, magnemoe said:

55 minutes ago, tater said:

Ithacus had this 4 man escape pod. I'd think that the very top of a crew BFS could be a capsule. Ideally it would have a heatshield pass-through hatch, so that there could be a crew compartment below that was more extensive. Crew would ride in the escape cockpit during liftoff and reentry.

I agree, the lack of the LES is an issue, second stage problems and landings will be an total loss. 
I would use an pretty simple LES, not much of an heat shield, not able to deorbit, chance of fail in the late stage is pretty low,  if you reach orbit you send an rescue mission.
During reentry I don't think LES is very useful i think, trying to separate during deorbit will be very hard in any case. Now landing is dangerous and here an LES would be very useful. 

I definitely agree with having an ascent/landing capsule separate from the larger crew compartment, for the same reason that you wear an IVA suit during ascent and entry. I don't ever see orbital launches being a shirtsleeve environment.

The trouble with a rescue mission is that if you're going to do a rescue, then your escape pod needs to have its own robust onboard RCS system for docking, and that's tricky. Might be cheaper, mass-wise, to just go with a heat shield. 

I'm having trouble coming up with a good placement that integrates with the rest of the craft but can still leave the rest of the craft in a hurry if need be.

6 minutes ago, sh1pman said:

Will SpaceX try to save the fairing after Hispasat launch?

Mr Steven is the only netted recovery ship so far, but I'm sure they'll still chute it down to the water and recover it.

They are, however, trying to save the booster.

[tater]

10 minutes ago, sh1pman said:

Will SpaceX try to save the fairing after Hispasat launch?

Next attempt is next month. Mr. Steven is in LA, so any attempts will be at VAFB. I think they want a proof of concept before they rig up more than one ship.

[Spaceception]

12 minutes ago, tater said:

Next attempt is next month. Mr. Steven is in LA, so any attempts will be at VAFB. I think they want a proof of concept before they rig up more than one ship.

That makes sense... But if that's the case, why not do it at the cape? There's a lot more launches. Or am I missing something?

Edited February 23, 2018 by Spaceception

[StrandedonEarth]

I would have thought it had steerable chutes, and then it can flare above the net and drop right in. Apparently they need a faster boat along with the bigger chutes they have planned

[tater]

1 minute ago, Spaceception said:

That makes sense... But if that's the case, why not do it at the cape? There's a lot more launches. Or am I missing something?

Maybe they want to be able to quickly change stuff, or easily bring it to the shop in LA. Dunno.

[Rakaydos]

23 minutes ago, StrandedonEarth said:

I would have thought it had steerable chutes, and then it can flare above the net and drop right in. Apparently they need a faster boat along with the bigger chutes they have planned

As I understand it, there was some trouble with the fairing displacing so much air that the chute collapsed in the middle.

[StrandedonEarth]

1 minute ago, Rakaydos said:

As I understand it, there was some trouble with the fairing displacing so much air that the chute collapsed in the middle.

I thought fairing 2.0 was supposed to resolve that with different attach points, or did they see that it’s still a problem?

[Rakaydos]

Just now, StrandedonEarth said:

I thought fairing 2.0 was supposed to resolve that with different attach points, or did they see that it’s still a problem?

I dont know. it's still a big air displacement, however you rig it.

[tater]

Musk said they need a bigger chute. Decreasing the sink rate gives them more lateral range to steer into.

[Starman4308]

For a BFR LES, I'd think about just using a Crew Dragon. Put it at the top of the stack. If there's a problem, separate from the rest of the vehicle much like you would for an F9 upper stage failure. If there's not a problem, the astronauts can just egress from the Dragon's hatch into the rest of the pressurized section of the BFR vehicle.

It's not like the BFR doesn't have the payload capacity for a Crew Dragon.

[PB666]

7 hours ago, sevenperforce said:

Oh, I was just being overly enthusiastic, since to date we only heard of one entering successfully on each mission.

They are just fairings.

[sevenperforce]

1 hour ago, Starman4308 said:

For a BFR LES, I'd think about just using a Crew Dragon. Put it at the top of the stack. If there's a problem, separate from the rest of the vehicle much like you would for an F9 upper stage failure. If there's not a problem, the astronauts can just egress from the Dragon's hatch into the rest of the pressurized section of the BFR vehicle.

It's not like the BFR doesn't have the payload capacity for a Crew Dragon.

That was my thought. Trouble is that BFS's re-entry profile is highly dependent on its OML. How do you integrate a Dragon 2 + trunk with the BFS OML, still allowing it to enter normally, while ensuring it can do a successful abort, while also allowing crew to move freely out of the capsule and into the rest of the ship?

[tater]

1 hour ago, Starman4308 said:

For a BFR LES, I'd think about just using a Crew Dragon. Put it at the top of the stack. If there's a problem, separate from the rest of the vehicle much like you would for an F9 upper stage failure. If there's not a problem, the astronauts can just egress from the Dragon's hatch into the rest of the pressurized section of the BFR vehicle.

It's not like the BFR doesn't have the payload capacity for a Crew Dragon.

The nose has to fit with a nominal reentry profile, I'd think a purpose-built nose module would be better. With the exception of sending it someplace like the Moon, I don't see a lot of point in a crew version, however, as you mix crew and cargo.

Anyone complaining about the lack of crew safety on BFS of course needs to remember that Shuttle flew, and never had real abort modes. I know they practiced them, but they were all pretty dubious.

[sevenperforce]

4 minutes ago, tater said:

The nose has to fit with a nominal reentry profile, I'd think a purpose-built nose module would be better. With the exception of sending it someplace like the Moon, I don't see a lot of point in a crew version, however, as you mix crew and cargo.

Anyone complaining about the lack of crew safety on BFS of course needs to remember that Shuttle flew, and never had real abort modes. I know they practiced them, but they were all pretty dubious.

Well, if it is REALLY as cheap as Musk thinks it will be, then they'll surely want to use it for crew launches instead of Falcon 9.

A lunar version would need abort for Earth EDL from cislunar space.

The dubiousness of the Shuttle abort modes (and the two Shuttle LOCVs) are why I raised the question of abort on BFS.

[tater]

Yeah, I mean as far as mass numbers of crew. I'd think for LEO/cislunar, you could have as large a crew as you'd ever want, and still be able to have a capsule at the nose.

Shuttle SRB chutes had a design load of 88 tons, and massed a little under a ton. Drogues massed about half that. For a crew version, the whole thing could have backup parachutes at a small loss of cargo, assuming any engine failure that would result in a LOM was detected in time.

[sevenperforce]

4 minutes ago, tater said:

Yeah, I mean as far as mass numbers of crew. I'd think for LEO/cislunar, you could have as large a crew as you'd ever want, and still be able to have a capsule at the nose.

Shuttle SRB chutes had a design load of 88 tons, and massed a little under a ton. Drogues massed about half that. For a crew version, the whole thing could have backup parachutes at a small loss of cargo, assuming any engine failure that would result in a LOM was detected in time.

What about something like a Mk2 cockpit, with egress in the rear, between escape engines, and a heat shield underneath? Not right on top, but along the dorsal side just aft of the nose. 

[cubinator]

1 hour ago, sevenperforce said:

What about something like a Mk2 cockpit, with egress in the rear, between escape engines, and a heat shield underneath? Not right on top, but along the dorsal side just aft of the nose. 

I believe NASA considered a detachable Shuttle cockpit, but found that it was too hard. I think that SpaceX is really going for a super-duper reliable BFR, that only will ever need two parts. BFS also wouldn't have stuff coming at it from the side if the booster was destroyed, not as badly as Shuttle did. 

If there was a need to abort during a BFR launch, could the booster engines most likely be shut off so that the spaceship can get away faster?

[Starman4308]

8 minutes ago, cubinator said:

I believe NASA considered a detachable Shuttle cockpit, but found that it was too hard. I think that SpaceX is really going for a super-duper reliable BFR, that only will ever need two parts. BFS also wouldn't have stuff coming at it from the side if the booster was destroyed, not as badly as Shuttle did. 

If there was a need to abort during a BFR launch, could the booster engines most likely be shut off so that the spaceship can get away faster?

Unless the control mechanisms are utterly shot, I don't see why the engines can't be shut off, though it may take a few seconds to go from 100% thrust down to zero.

I believe one of the early Falcon 1 launches failed because of that: they'd moved to regenerative cooling on the Merlin engine (meaning there's some residual fuel in the engine between the turbopump and the combustion chamber), and they didn't wait for the thrust to die down before separating stage 2.

Regardless of what SpaceX wants, I suspect NASA will insist on a LAS. I personally wouldn't trust a no-LAS BFR for crew transport unless they'd demonstrated a couple hundred trouble-free flights in a row, bare minimum.

[cubinator]

9 minutes ago, Starman4308 said:

Regardless of what SpaceX wants, I suspect NASA will insist on a LAS. I personally wouldn't trust a no-LAS BFR for crew transport unless they'd demonstrated a couple hundred trouble-free flights in a row, bare minimum.

That's quite likely. For a cargo or demo run to Mars, though, they'll probably have to launch the same rocket up to ten times in a row to top off the spaceship anyways, and that'd be pretty reassuring to see the rocket pull that off. And if they do that with several spaceships, that's already a lot of flights. They might be able to get that many flights in in just a few years.