totm nov 2023 SpaceX Discussion Thread

[DAL59]

6 hours ago, Starman4308 said:

"It was NASA's planetary protection officer, in the mission control room, with a baseball bat."

Does that guy really have that any authority over non-NASA missions though?  I mean, he could try to raise a complaint, but Musk would definitely not listen to them, and nobody wants to be the guy who stops a Mars mission.  

[CatastrophicFailure]

32 minutes ago, tater said:

Atlas launches later tonight. Dunno if they leave her horizontal, or take her back to the barn during the Atlas launch.

Despite Atlas’s record, seems the prudent thing would be to put it inside. 

Of course, the Kerbal in me wants to mash the spacebar right like it is. (⊙_◎)

[DAL59]

1 hour ago, tater said:

Life support alone is a daunting issue when it has to work for years without breaking.

They did it on the ISS.  They could also use algea.  You only need 6 liters of algea per person for air.  

[StrandedonEarth]

2 minutes ago, DAL59 said:

They did it on the ISS.  They could also use algea.  You only need 6 liters of algea per person for air.  

The system on the ISS has had many breakdowns and has relied on spare parts delivered from roughly 200 miles and 17,500 mph away. Canned O2 is the backup system. 

[DAL59]

3 hours ago, Nibb31 said:

The point is, there is a moment between the Powerpoint phase (now) and when BFS flies (somewhere in the future), where someone is going to point out to Musk that "it's turning out much harder than he thought it was".

 

It is not the powerpoint phase.  They have already taken many employees and put them into BFR construction.  They already researched SSRP for Dragon.  It is not a distant "2043 to Mars" thing like NASA, BFR tests are only 2 years away.  BFR will have to be delayed by a factor of 4 for NASA to have a chance.      

9 minutes ago, StrandedonEarth said:

The system on the ISS has had many breakdowns and has relied on spare parts delivered from roughly 200 miles and 17,500 mph away. Canned O2 is the backup system. 

Maybe there's a more efficient way to recycle air though.  I wish Musk would talk about that.

Also, the ISS is a modular, international, very finicky station.  On the ISS, 5/6 of astronauts time is spent on repairs.  There are too many sub-sub systems and different modules.  The BFR is an actual spaceship, made entirely by a single company, and should be more robustly designed.  They could have more unitary systems.                                  

[Bill Phil]

18 minutes ago, StrandedonEarth said:

The system on the ISS has had many breakdowns and has relied on spare parts delivered from roughly 200 miles and 17,500 mph away. Canned O2 is the backup system. 

Don't they have oxygen candles as well?

[StrandedonEarth]

2 minutes ago, Bill Phil said:

Don't they have oxygen candles as well?

Actually, I’m not sure, they might, particularly in the Russian segment. I know they were used on MIr, and were the cause of a fire there. 

[tater]

32 minutes ago, DAL59 said:

They did it on the ISS.  They could also use algea.  You only need 6 liters of algea per person for air.  

The LS on ISS is a mess, and is constantly in need of repair. They have not "done it on ISS." Why throw this out there, it's not even controversial that the largest challenge for crew flights BEO is the life support issue.

[tater]

 

[CatastrophicFailure]

1 hour ago, tater said:

The LS on ISS is a mess, and is constantly in need of repair. They have not "done it on ISS." Why throw this out there, it's not even controversial that the largest challenge for crew flights BEO is the life support issue.

On this note, what would be needed to chemically separate CO2 into carbon & oxygen?

[IncongruousGoat]

6 minutes ago, CatastrophicFailure said:

On this note, what would be needed to chemically separate CO2 into carbon & oxygen?

It's not easy. The most direct method is the Bosch process, which works by the following reaction: CO₂ + 2H₂  → C_(s)+2H₂O. The water can then be electrolyzed in order to get the oxygen and retrieve the hydrogen used. The problem with this is that A: it runs really, really hot (400-650 C), which is not good when you're in space, B: the carbon byproduct is solid graphite, which one has to periodically clean out of the reactor... somehow, and C: electrolyzing water is really energy-intensive. Worse still, if one is using a catalyst to speed up the reaction, the graphite byproduct tends to build up on the catalyst bed and render it useless until painstakingly cleaned.

There's also the much-vaunted Sabatier reaction, which works by the following reaction: CO₂ + 4H₂ → CH₄ + 2H₂O. The waste methane can then be decomposed to carbon and hydrogen by pyrolysis in order to close the loop. This, however, has similar problems to the Bosch reaction: it runs hot, and produces solid carbon as a by-product, which needs to be periodically chiseled out of the reaction chamber.

In brief, it's possible but not as simple as one might think, and still requires a lot of R&D before it's ready to fly.

[CatastrophicFailure]

Interesting... what about just going full nuclear submarine? Assuming the BFS could carry a big enough solar array, or small nuclear reactor (a hundred and some tonnes to Mars, after all) how much water would it need to haul as well to electrolyze into O2 for a crew of, Oh, say 10 for easy numbers’ sake? A hundred and some tonnes of payload, after all. That seems to me like a big part of the life support solution. 

[mikegarrison]

6 minutes ago, CatastrophicFailure said:

Interesting... what about just going full nuclear submarine? Assuming the BFS could carry a big enough solar array, or small nuclear reactor (a hundred and some tonnes to Mars, after all) how much water would it need to haul as well to electrolyze into O2 for a crew of, Oh, say 10 for easy numbers’ sake? A hundred and some tonnes of payload, after all. That seems to me like a big part of the life support solution. 

Water is generally useful, because it's a great radiation shield too. But it's extremely expensive to haul a bunch of water up into orbit.

[IncongruousGoat]

22 minutes ago, CatastrophicFailure said:

Interesting... what about just going full nuclear submarine? Assuming the BFS could carry a big enough solar array, or small nuclear reactor (a hundred and some tonnes to Mars, after all) how much water would it need to haul as well to electrolyze into O2 for a crew of, Oh, say 10 for easy numbers’ sake? A hundred and some tonnes of payload, after all. That seems to me like a big part of the life support solution. 

The amount of water necessary aside (I haven't run the numbers), what are you going to do with the CO₂ breathed out by the crew? You could try scrubbers, but that might get difficult for a 6-month flight to Mars. You could separate it out from the air by fractional distillation and then throw it overboard, but that is A: energy-intensive, B: wasteful, and C: would produce a lot of waste heat you now have to deal with when you liquefy the air at the start of the process. Once you're on Mars you can use the planet as a freezer, but in space shunting the kind of heat around you'd need to liquefy a lot of air is not going to be easy.

[CatastrophicFailure]

19 minutes ago, mikegarrison said:

Water is generally useful, because it's a great radiation shield too. But it's extremely expensive to haul a bunch of water up into orbit.

If the BFR operates as economically as is hoped, that changes a lot of things. Like schlepping all that useful water into space... 

@IncongruousGoat Nuclear submarines can easily go six months and more with only lots of water and lots of power as resources, and I think they just use scrubbers. With the kind of lift and loft capacity the BFR promises to bring, maybe the life support solution model is below instead of above. 

Id be very curious how much water a person needs per day to live in a “vacuum,” but math make brain hurt. 

[mikegarrison]

3 minutes ago, CatastrophicFailure said:

If the BFR operates as economically as is hoped, that changes a lot of things. Like schlepping all that useful water into space... 

@IncongruousGoat Nuclear submarines can easily go six months and more with only lots of water and lots of power as resources, and I think they just use scrubbers. With the kind of lift and loft capacity the BFR promises to bring, maybe the life support solution model is below instead of above. 

Id be very curious how much water a person needs per day to live in a “vacuum,” but math make brain hurt. 

I am not an expert on nuclear subs, but I imagine they dump a LOT of heat to the ocean, which is a very convenient heat sink for them.

[tater]

Atlas scrubbed, 24 turn around, so no FH static fire tomorrow.

[Just Jim]

5 minutes ago, tater said:

Atlas scrubbed, 24 turn around, so no FH static fire tomorrow.

I hate to admit this, but I'm almost half-glad... the weather is crystal clear, and we would have seen it from here easily.

But it's really, really cold out there! Brrrr....... 

[tater]

I wanna see them light those candles!

[insert_name]

4 hours ago, DAL59 said:

It is not the powerpoint phase.  They have already taken many employees and put them into BFR construction.  They already researched SSRP for Dragon.  It is not a distant "2043 to Mars" thing like NASA, BFR tests are only 2 years away.  BFR will have to be delayed by a factor of 4 for NASA to have a chance.      

Maybe there's a more efficient way to recycle air though.  I wish Musk would talk about that.

Also, the ISS is a modular, international, very finicky station.  On the ISS, 5/6 of astronauts time is spent on repairs.  There are too many sub-sub systems and different modules.  The BFR is an actual spaceship, made entirely by a single company, and should be more robustly designed.  They could have more unitary systems.                                  

Falcon heavy was announced in 2011, was supposed to be flying in 2013, so a four factor delay is reasonable

[Starman4308]

16 minutes ago, insert_name said:

Falcon heavy was announced in 2011, was supposed to be flying in 2013, so a four factor delay is reasonable

To be fair to Falcon Heavy, there were some pretty legitimate reasons to delay it: the Falcon 9 it's based on had not finished maturing, so it was either freeze the Falcon Heavy to use outdated F9 cores, or just keep on delaying it until the F9 design had reached maturity. Do remember that the Block 5 Falcon 9 is a vastly better launch vehicle than the original design.

What would cause such a delay in BFR is that it requires an absurd number of new technologies and design paradigms to work perfectly. We're talking about reentry of a very large vehicle (the last such was the always-problematic Space Shuttle), precision landing after a hypersonic reentry, fast and cheap turnaround of said very large reentry vehicle, an engine twice as large as anything SpaceX has worked with before (on par with the SSME), and the list just goes on and on. I'm not going to dismiss BFR as impossible quite yet, but at this point, it's barely anything more than a rocket engine and some blueprints.

[CatastrophicFailure]

1 hour ago, mikegarrison said:

I am not an expert on nuclear subs, but I imagine they dump a LOT of heat to the ocean, which is a very convenient heat sink for them.

Fair enough point, but If the rub becomes “what do we do with all this heat?” Instead of “how the heck do we keep these people alive in the first place?” That seems like a much more straightforward engineering challenge. 

Maybe they could have a barbecue. Mmmmm, space barbecue...

4 minutes ago, Starman4308 said:

it's barely anything more than a rocket engine and some blueprints.

That still puts it leaps and bounds ahead of anything NASA has planned for Mars... 

[Starman4308]

4 minutes ago, CatastrophicFailure said:

Fair enough point, but If the rub becomes “what do we do with all this heat?” Instead of “how the heck do we keep these people alive in the first place?” That seems like a much more straightforward engineering challenge. 

Maybe they could have a barbecue. Mmmmm, space barbecue...

That still puts it leaps and bounds ahead of anything NASA has planned for Mars... 

What to do with all that heat is "football fields worth of radiators". Nuclear reactors are no panacea to energy requirements in space.

I'd also point out that NASA had football fields worth of blueprints and even engines for Mars... just no funding or SHLVs to make that a reality. I'm not convinced manned exploration of Mars is economically viable at current levels; while BFR would get us there if it works, there is so much that can go wrong with BFR. Even small additional reflight costs or failure rates would hugely crimp SpaceX's ability to turn BFR into an economic reality, because the hardware is just so expensive and so over-specced for most of what it would do.

[PB666]

13 minutes ago, Starman4308 said:

To be fair to Falcon Heavy, there were some pretty legitimate reasons to delay it: the Falcon 9 it's based on had not finished maturing, so it was either freeze the Falcon Heavy to use outdated F9 cores, or just keep on delaying it until the F9 design had reached maturity. Do remember that the Block 5 Falcon 9 is a vastly better launch vehicle than the original design.

What would cause such a delay in BFR is that it requires an absurd number of new technologies and design paradigms to work perfectly. We're talking about reentry of a very large vehicle (the last such was the always-problematic Space Shuttle), precision landing after a hypersonic reentry, fast and cheap turnaround of said very large reentry vehicle, an engine twice as large as anything SpaceX has worked with before (on par with the SSME), and the list just goes on and on. I'm not going to dismiss BFR as impossible quite yet, but at this point, it's barely anything more than a rocket engine and some blueprints.

There are some pretty legiitimate reasons to delay BFR, namely the Boca-Chica launch facility is at least a year behind schedule.

[tater]

You have to take delays on a case by case basis. SpaceX developered reuse in the same “delay” time period, as well as obviating the need for almost all FH launches anyway, due to F9 improvements.

I will wait and see on BFR and BFS for them to actually start work, then see what shakes out.