totm nov 2023 SpaceX Discussion Thread

[darthgently]

3 hours ago, Terwin said:

Unfortunately, boiloff is not a solved problem.

Though earthshine would still be a problem, getting the team that did the shield for JWST could be a win

[RCgothic]

Double layer tanks with vacuum between them and a solar powered cryo-cooler. Maybe a sunshade too. Refine as necessary.

It's not as if zero-boil-off tanks are a theoretical impossibility.

Edited December 9, 2023 by RCgothic

[tater]

17 minutes ago, RCgothic said:

Double layer tanks with vacuum between them and a solar powered cryo-cooler. Maybe a sunshade too. Refine as necessary.

It's not as if zero-boil-off tanks are a theoretical impossibility.

Yeah, there has been a bunch of work. ULA did a lot of footwork for ACES, for example. It's just actually building it to see how it works in the real world.

[Jacke]

1 hour ago, RCgothic said:

Double layer tanks with vacuum between them and a solar powered cryo-cooler. Maybe a sunshade too. Refine as necessary.

It's not as if zero-boil-off tanks are a theoretical impossibility.

1 hour ago, tater said:

Yeah, there has been a bunch of work. ULA did a lot of footwork for ACES, for example. It's just actually building it to see how it works in the real world.

What I think limits what has been done so far is that the lifetime needed for cryogenic propellants (beyond lower amounts for fuel cells that have primarily used boil-off cooling) has just been at most a couple of days to allow for an extended parking LEO prior to the final burn.  Beyond that for mission propellants it's almost completely storable hypergols or liquid noble gases for ion drives.

Which means it's whole new experience for long term cryo propellant storage.  At least it's not LH2.  But I expect this will take a fair amount of testing to find what measures will be worth their expense in payload mass.  Adding mass on the final stage of a rocket (for cooling gear or lost propellants) is near 1-to-1 in cost of payload mass.

[tater]

32 minutes ago, Jacke said:

Which means it's whole new experience for long term cryo propellant storage.  At least it's not LH2.  But I expect this will take a fair amount of testing to find what measures will be worth their expense in payload mass.  Adding mass on the final stage of a rocket (for cooling gear or lost propellants) is near 1-to-1 in cost of payload mass.

Yeah, the ACeS work was explicily for cislunar at least, so whatever they worked on was assuming a few days at least. ~3 days for transit, then lunar orbital insertion.

[tater]

Up next:

 

[RCgothic]

16 hours ago, Jacke said:

What I think limits what has been done so far is that the lifetime needed for cryogenic propellants (beyond lower amounts for fuel cells that have primarily used boil-off cooling) has just been at most a couple of days to allow for an extended parking LEO prior to the final burn.  Beyond that for mission propellants it's almost completely storable hypergols or liquid noble gases for ion drives.

Which means it's whole new experience for long term cryo propellant storage.  At least it's not LH2.  But I expect this will take a fair amount of testing to find what measures will be worth their expense in payload mass.  Adding mass on the final stage of a rocket (for cooling gear or lost propellants) is near 1-to-1 in cost of payload mass.

In this instance they could launch a 300t depot with over 200t of zero boil off gubbins and *zero* residual propellants and all it would cost is an additional refuelling mission.

Obviously there's room to refine, but as a first effort they've got a lot of mass budget to play with.

[darthgently]

Upon reading this, you have 30 seconds to gin up a use-case for the fictional Falcon 18

 

[SunlitZelkova]

6 minutes ago, darthgently said:

Upon reading this, you have 30 seconds to gin up a use-case for the fictional Falcon 18

 

Bruh, this is a real concept.

https://dongfanghour.com/ispace-asymetrical-hyperbola-3a/

China’s i-Space wants to do this.

It is useful because it creates an intermediate capability between the “light” rocket (F9 or its Chinese clone) and the “heavy” rocket (FH or its Chinese clone)- in other words, a “medium rocket”.

[tater]

 

[darthgently]

3 hours ago, SunlitZelkova said:

Bruh, this is a real concept.

https://dongfanghour.com/ispace-asymetrical-hyperbola-3a/

China’s i-Space wants to do this.

It is useful because it creates an intermediate capability between the “light” rocket (F9 or its Chinese clone) and the “heavy” rocket (FH or its Chinese clone)- in other words, a “medium rocket”.

Looks can be extremely deceiving 

[SunlitZelkova]

15 minutes ago, darthgently said:

Looks can be extremely deceiving 

Eh, this is what was said about the R-56, a rocket developed by Mikhail Yangel, the lesser known of the space industry but a huge name in ballistic missiles. One blog called it “too big for LEO missions, too small for lunar missions” and attributed that to why it was never built. But Falcon Heavy, which has a roughly similar payload to the R-56, has proven to be useful.

I think it would be useful to have in the same way Atlas occasionally flew with only one SRB. But the question is whether that capability is worth the development cost. If Musk died in a car crash in 2015 and Starship never existed, I think it would be worth it. But now it would just make sense to use whatever funding can be found for SS/SH.

[tater]

Properly done, a 2 core F9 only saves the cost of props and refurb for 1 booster in a use case where 3 cores (all reused) is overkill. We'd have to look at the payload numbers for F9 with booster reuse (RTLS, then ASDS), compare it to FH with 3 cores recovered, vs 1 expended—and the difference between whichever cores are ASDS vs RTLS). That number is not $0, but it's not a huge amount, either, and will be for some narrow payload mass regime I bet.

[darthgently]

1 hour ago, SunlitZelkova said:

Eh, this is what was said about the R-56, a rocket developed by Mikhail Yangel, the lesser known of the space industry but a huge name in ballistic missiles. One blog called it “too big for LEO missions, too small for lunar missions” and attributed that to why it was never built. But Falcon Heavy, which has a roughly similar payload to the R-56, has proven to be useful.

I think it would be useful to have in the same way Atlas occasionally flew with only one SRB. But the question is whether that capability is worth the development cost. If Musk died in a car crash in 2015 and Starship never existed, I think it would be worth it. But now it would just make sense to use whatever funding can be found for SS/SH.

I agree.  What I meant was is that just because those rockets look like SpaceX rockets doesn't mean they would perform the same

[darthgently]

Someone asked Jared Isaacman what was taking Polaris Dawn so long...

 

 

Edited December 10, 2023 by darthgently

[tater]

 

[tater]

Testing new, smaller tiles.

 

[Cuky]

A bit under 3h ago was the first time that I have seen Starlink satellites passing above my island and those weren't as bright as I actually expected. If they didn't move in a perfect line one after the other one could easily mistake them for a star or a plane. But it was nice finally experiencing seeing something man made with my naked eyes in the night sky

[JoeSchmuckatelli]

17 minutes ago, Cuky said:

A bit under 3h ago was the first time that I have seen Starlink satellites passing above my island and those weren't as bright as I actually expected. If they didn't move in a perfect line one after the other one could easily mistake them for a star or a plane. But it was nice finally experiencing seeing something man made with my naked eyes in the night sky

Spotting satellites is fun.  I remember getting up before dawn in West Texas and watching them in the 70s.  The most impressive I ever saw was Shuttle docked with ISS in the 90s; the brightest man-made structure in the sky.  Nowadays, its fairly easy to spot some from a city (presumes you're looking just after sunset / before sunrise).

But it is super cool to know what you're looking at!  Most of the time I just see a fast moving red dot and think... yup, that's a satellite.

[CatastrophicFailure]

18 hours ago, SunlitZelkova said:

One blog called it “too big for LEO missions, too small for lunar missions”

So, basically, SLS? 

Spoiler

 

1 hour ago, Cuky said:

A bit under 3h ago was the first time that I have seen Starlink satellites passing above my island and those weren't as bright as I actually expected. If they didn't move in a perfect line one after the other one could easily mistake them for a star or a plane. But it was nice finally experiencing seeing something man made with my naked eyes in the night sky

Have you never seen the ISS? 

22 hours ago, SunlitZelkova said:

Bruh, this is a real concept.

I wonder if we might see more "goofy" stuff like this as boosters start reaching a hard wall EOL? Like, they need to dispose of it anyway, might as well give it a Viking funeral vs scrapping it. Probably cheaper, too.

[Cuky]

1 hour ago, CatastrophicFailure said:

Have you never seen the ISS?

Sadly no. Even starlink today I just happened to be outside at the time they were passing above.  The problem I have is that it mostly passes far out of sight and is only visible for few seconds so I don't even try. But now that you asked me I went to check and on December 20th it should pass above just 100-150km north from where I am located and should be visible for around 5 minutes so I might go looking for it if I don't forget

Edited December 10, 2023 by Cuky

[SunlitZelkova]

3 hours ago, JoeSchmuckatelli said:

Nowadays, its fairly easy to spot some from a city (presumes you're looking just after sunset / before sunrise).

I’m very lucky to live right on the edge of suburbia. If I drive 5 minutes one way I’m in ranch country and 5 minutes the other way there is a supermarket.

So I get good internet to enjoy discussing with everyone on the KSP forum while also having decent enough darkness to see satellites frequently. Like, I’ll often see 5-6 in one night if it’s clear enough.

Notably, I tend to find them easier to spot in the middle of the night/early morning hours, rather than just after sunrise or sunset.

3 hours ago, JoeSchmuckatelli said:

The most impressive I ever saw was Shuttle docked with ISS in the 90s; the brightest man-made structure in the sky.

I came to stargazing too late to see Shuttle with ISS, but the one time I did see ISS, there was a Cargo Dragon trailing behind it. The difference between the station and that ship is just incredible.

Also interestingly, the Cargo Dragon was dimmer than most satellites I see. I don’t know if that we because it was near ISS or if the solar panel side was facing me and absorbing light? If anyone knows please share your thoughts 

[tater]

 

[darthgently]

19 hours ago, tater said:

Testing new, smaller tiles.

 

I suppose the idea is that if a tile comes loose, a smaller area will be exposed.  Am I missing other possible advantages?

[sevenperforce]

18 hours ago, CatastrophicFailure said:

On 12/9/2023 at 9:25 PM, SunlitZelkova said:

One blog called it “too big for LEO missions, too small for lunar missions”

So, basically, SLS? 

OOOOOOH that burns like an pad without a deluge.

19 hours ago, tater said:

Testing new, smaller tiles.

 

I dunno why but that gives me the ick.

On 12/9/2023 at 11:32 PM, darthgently said:

Someone asked Jared Isaacman what was taking Polaris Dawn so long...

 

 

Kind of figured something along these lines. A real solid workable EVA suit -- one they actually want to build on rather than use as a tethered one-off -- is tough. But doable.

On 12/9/2023 at 10:36 PM, tater said:

Properly done, a 2 core F9 only saves the cost of props and refurb for 1 booster in a use case where 3 cores (all reused) is overkill. We'd have to look at the payload numbers for F9 with booster reuse (RTLS, then ASDS), compare it to FH with 3 cores recovered, vs 1 expended—and the difference between whichever cores are ASDS vs RTLS). That number is not $0, but it's not a huge amount, either, and will be for some narrow payload mass regime I bet.

There are a lot of unknowns about internal operational cost of ASDS vs RTLS and so forth.

In theory, there are a total of 17 different flight options for the Falcon family:

1. One core
   1. RTLS
   2. ASDS
   3. Expended
2. Two core
   1. Both RTLS
   2. Booster RTLS and center ASDS
   3. Both ASDS
   4. Booster RTLS and center expended
   5. Booster ASDS and center expended
   6. Both expended
3. Three core
   1. All RTLS
   2. Boosters RTLS, center ASDS
   3. Boosters RTLS, center expended
   4. One booster RTLS, one booster ASDS, center ASDS
   5. One booster RTLS, one booster ASDS, center expended
   6. Both boosters ASDS, center ASDS
   7.  Both boosters ASDS, center expended
   8. All expended

I really have no idea what the correct ordering is in terms of payload capability.

1 minute ago, darthgently said:

19 hours ago, tater said:

Testing new, smaller tiles.

 

Expand  

I suppose the idea is that if a tile comes loose, a smaller area will be exposed.  Am I missing other possible advantages?

That's one advantage, but another one probably comes before that: smaller tiles have a lower torque arm moment and thus are less sensitive to flexion of the underlying substrate surface. This would make sense if this is a problem area where they keep losing tiles no matter what.