totm nov 2023 SpaceX Discussion Thread

[IncongruousGoat]

2 minutes ago, kerbiloid said:

Er... Not that I propose, I am not the mod maintainer.

But as you have said yourself,

So, if somebody can extract the "oxygen trapped in oxides", this means that he can split the oxides into oxygen and metals.
And as unlikely he had brought cryolite, coke, lime or anything else, probably he does this not chemically, but non-chemically. I.e. by some physical process (you had mentioned the oxygen extraction, btw, not me).

Personally I can imagine (and consider this as a future mainstream) only heating any piece of rock and junk up to ionization temperature and separating ions of different elements by a magnetic trap, getting metal powders of pure Fe, Al, Ti, etc.
But, this is, of course, a more or less far future, not BFR level.

So, I just mean that if somebody can get O, he automatically gets Al as junk.

Ah, fair enough. When I said that, I was trying to make a point about the elements present in the regolith, not about what can feasibly be done with said regolith. I see what you mean now.

[tater]

Yeah, the proposed mechanisms involved lots of heat, basically. Of course the guys I used to hear talks from were also all-in for a "subselene" miner that didn't bore with a bit, but used a nuclear reactor to melt regolith, which would seep into the surrounding area as glass, leaving an air tight tube (these were Los Alamos guys).

 

Edited September 30, 2017 by tater

[TheEpicSquared]

Damn, this thread has exploded. 11.11% (pages 97-108 at the time of writing) has been posted during and after Musk's presentation 

[tater]

Ideally, a tug would have the refilling pipes set up exactly as above. Might be tight in the cargo bay, but this could allow practice refilling (I see why they use "refilling," it makes more sense, since "refueling" explicitly ignore oxidizer). I think the trick on tug size is for it to be minimal to accomplish the goal with some excess capacity, otherwise it's little different than refilling the cargo BFS, and hauling stuff to GEO that way.

Honestly, I suppose if operational experience is the goal anyway, then comanifesting, and refilling to take them with BFS might make more sense, and gain more experience. With ion prop, then it's so much more efficient, then it might make more sense. 

[Rakaydos]

So, a tug using a single raptor vac (possibly even more overexpanded than the normal raptorvac) with the delta V to bring a BFR load (150 tonnes) to gto, and aerobreak back down to LEO, with a reserve. Ideally should be fillable by a single tanker load (150 tonnes of methalox?)

[tater]

No, designed to carry maybe a few GEO stats.

[Rakaydos]

8 minutes ago, tater said:

No, designed to carry maybe a few GEO stats.

If the BFR ever fully booked it's cargo bay, how many tugs would you say would be needed?

[tater]

I have no idea. I was just contemplating if it would make more sense to have a reusable pure orbital asset as part of the system, instead of using the lander vehicle for all roles. A spacefaring society should have some "pure" spacecraft  .

Edited September 30, 2017 by tater

[CatastrophicFailure]

I keep hearing about this "new refueling method" from the presentation. I haven't watched it yet, and probably won't have time to. Where's this in the video?

[Guest]

You don't need anything as big as Fregat but if we use that as an example, it masses a bit more than six tons (base model). Assume you bring up a nine ton sat with it and the Fregat performs circularization and then deorbits itself. Fifteen tons a pop so ten GEO sats.

[Pipcard]

7 minutes ago, CatastrophicFailure said:

I keep hearing about this "new refueling method" from the presentation. I haven't watched it yet, and probably won't have time to. Where's this in the video?

23:30 - BFR spaceships will dock end-to-end and use milli-g thrusts to settle the methalox propellant during transfer.

Edited September 30, 2017 by Pipcard

[tater]

[CatastrophicFailure]

10 minutes ago, Pipcard said:

23:30 - BFR spaceships will dock end-to-end and use milli-g thrusts to settle the methalox propellant during transfer.

Wow, that is brilliantly simple. Don't bother with pumps, just use "gravity." 

 

Edit: Yeah, I couldn't sit thru 45 minutes of that.  The man is brilliant and a visionary, but watching him speak in public reminds me too much of, well, me. 

Edited September 30, 2017 by CatastrophicFailure

[Nibb31]

Not gravity, thrust. You need to be thrusting for the whole duration of the refueling.

[Pipcard]

That's why "gravity" was in quotes.

8 minutes ago, CatastrophicFailure said:

Wow, that is brilliantly simple. Don't bother with pumps, just use "gravity." 

 

Edit: Yeah, I couldn't sit thru 45 minutes of that.  The man is brilliant and a visionary, but watching him speak in public reminds me too much of, well, me. 

Here are some of the slides (no official .pdf yet)

Edited September 30, 2017 by Pipcard

[NSEP]

1 minute ago, Nibb31 said:

Not gravity, thrust. You need to be thrusting for the whole duration of the refueling.

I think he meant G forces. Not really gravity, but sort of simulair to it.

[sevenperforce]

1 hour ago, tater said:

Ideally, a tug would have the refilling pipes set up exactly as above. Might be tight in the cargo bay, but this could allow practice refilling (I see why they use "refilling," it makes more sense, since "refueling" explicitly ignore oxidizer). I think the trick on tug size is for it to be minimal to accomplish the goal with some excess capacity, otherwise it's little different than refilling the cargo BFS, and hauling stuff to GEO that way.

Honestly, I suppose if operational experience is the goal anyway, then comanifesting, and refilling to take them with BFS might make more sense, and gain more experience. With ion prop, then it's so much more efficient, then it might make more sense. 

Presumably there is redundancy on the refilling pipes (four are shown), so it could merely dock to one side or the other. 

56 minutes ago, Rakaydos said:

So, a tug using a single raptor vac (possibly even more overexpanded than the normal raptorvac) with the delta V to bring a BFR load (150 tonnes) to gto, and aerobreak back down to LEO, with a reserve. Ideally should be fillable by a single tanker load (150 tonnes of methalox?)

Definitely not a full BFR load to GTO. More like 40-50 tonnes to GTO or 10-20 tonnes to GEO. It wouldn't need a tanker, either; it could refuel from the same cargo BFR that brought up the comsats.

[mikegarrison]

1 minute ago, sevenperforce said:

Presumably there is redundancy on the refilling pipes (four are shown), so it could merely dock to one side or the other. 

I'm not sure why you would think that. It doesn't really make sense in his vision.

All this talk of "tugs" and such is ignoring that a huge part of what he is relying on is standardization. There is only one booster, and all ships use it. There are only two ships (one passenger, one cargo). There is only one engine, with two kinds of nozzles. They all dock to each other in a standardized way. They all use the same fuel. Etc. Etc.

This standardization is necessary to drive down costs (design and manufacturing as well as inventory, training, flight support hardware, etc. etc.).

[tater]

Any "tug" addition would standardized. You'll note the pipes are male/female, and female/male.

It's entirely a matter of need. You can either put an expendable GTO/GEO stage inside the bay, or you could make that stage reusable. n alternate method would be a stage just big enough to get the customer to GEO/GTO, then the stage comes back to the cargo BFS, and comes home. 100% reuse.

 

[Nibb31]

1 hour ago, sevenperforce said:

Presumably there is redundancy on the refilling pipes (four are shown), so it could merely dock to one side or the other.

4 pipes = 2 LoX for liquid methane, fluid and venting for each. No redundancy.

Edited September 30, 2017 by Nibb31

[kerbiloid]

Both NASA Docking System and International Docking System Standard docking port standards contain pipelines to transfer fuel, oxidizer and water.

Of course these docking nodes are not designed for cryogenic fuels.

But why somebody would split one single node into four separated stumps instead of making one big node ( like in KSP mods   ) ?
Instead of aligning just one, they should align four at once. (Btw, Space-X still has zero docking experience even with lightweight Dragon.)

Even in this case - why have two pipes per every fuel component? Are they going to deliver the fuel or recirculate ?

Another strange presentation from Space-X.

(Just for case. Unlikely they will exchange with pressurizing gas. More probably one ship will would vent it out, while the tanker will would just release fresh portion of the nitrogen from a high-pressure balloon.

Also, why this strange idea with milli-thrust refuelling instead of just press the fuel with nitrogen?)

Edited September 30, 2017 by kerbiloid

[Nibb31]

27 minutes ago, kerbiloid said:

Both NASA Docking System and International Docking System Standard docking port standards contain pipelines to transfer fuel, oxidizer and water.

Of course these docking nodes are not designed for cryogenic fuels.

But why somebody would split one single node into four separated stumps instead of making one big node ( like in KSP mods   ) ?
Instead of aligning just one, they should align four at once. (Btw, Space-X still has zero docking experience even with lightweight Dragon.)

Aligning 4 points or 1 is exactly the same mathematical problem. You need to align X, Y, Z and rotation in exactly the same way.

The CGI renderings are not showing docking radar antennas or sensors for automatic alignment. I would probably add a structural ring around the engine area with a set of latches. You don't want to put the stress of two huge spaceships on those fuel lines.

Quote

Even in this case - why have two pipes per every fuel component? Are they going to deliver the fuel or recirculate ?

Another strange presentation from Space-X.

You need fluid and venting: fluid goes one way, helium or filler gas goes the other.

The CGI models gloss over a lot of details (the landing legs and solar panels are missing in most of the shots, as well as RCS pods, antennas, etc...). They are definitely not accurate renderings of a mature design that is supposed to start construction in 6 months.

Edited September 30, 2017 by Nibb31

[Pipcard]

35 minutes ago, Nibb31 said:

4 pipes = 2 LoX for LH2, fluid and venting for each. No redundancy.

LOX and liquid methane, not LH2. Also, methalox does not need helium for pressurization.

Edited September 30, 2017 by Pipcard

[Nibb31]

Just now, Pipcard said:

LOX and liquid methane, not LH2.

Yes, corrected.

[CatastrophicFailure]

1 hour ago, Pipcard said:

That's why "gravity" was in quotes.

 

1 hour ago, NSEP said:

I think he meant G forces. Not really gravity, but sort of simulair to it.

Gravity is, after all, noted as acceleration.