Quote from: Greg Hullender on 01/20/2025 01:01 amQuote from: ChrML on 01/19/2025 10:10 pmPossibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?Not dumb, but there are a lot of challenges to overcome to make this work. Since SpaceX already announced they aren't planning to do this, it hasn't attracted a lot of interest. Has SpaceX said Starship will never have actively cooled depots? Or have they only said they intend to first try passive cooling and/or frequent replenishment of boil-off? I imagine replenishment gets more costly when the depot is located beyond LEO. Also any BLEO depot likely needs to hold propellant longer. So that's where it seems like active cooling will eventually be implemented.
Quote from: ChrML on 01/19/2025 10:10 pmPossibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?Not dumb, but there are a lot of challenges to overcome to make this work. Since SpaceX already announced they aren't planning to do this, it hasn't attracted a lot of interest.
Possibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?
Quote from: sdsds on 01/20/2025 03:19 amQuote from: Greg Hullender on 01/20/2025 01:01 amQuote from: ChrML on 01/19/2025 10:10 pmPossibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?Not dumb, but there are a lot of challenges to overcome to make this work. Since SpaceX already announced they aren't planning to do this, it hasn't attracted a lot of interest. Has SpaceX said Starship will never have actively cooled depots? Or have they only said they intend to first try passive cooling and/or frequent replenishment of boil-off? I imagine replenishment gets more costly when the depot is located beyond LEO. Also any BLEO depot likely needs to hold propellant longer. So that's where it seems like active cooling will eventually be implemented.Has a SOFI-MLI combo ever flown?
Doesn't MLI depend on she open space between layers?
Unless this is a real thing maybe active cooling and radiators are the best trade for extended ops in the warm clime of VLEO.
I'm tying to picture a shield big enough to block ~40% of the sky (Earth), mobile enough to keep the ship shielded as the nose targets the sun and the sun-earth angle changes, not get in the way of a mating ship, do it all repeatedly, and still be reasonably light. Almost forgot. It has to withstand cold thruster blasts. I'm coming up blank but hope it's a lack of imagination.
Quote from: OTV Booster on 01/21/2025 03:23 amI'm tying to picture a shield big enough to block ~40% of the sky (Earth), mobile enough to keep the ship shielded as the nose targets the sun and the sun-earth angle changes, not get in the way of a mating ship, do it all repeatedly, and still be reasonably light. Almost forgot. It has to withstand cold thruster blasts. I'm coming up blank but hope it's a lack of imagination.The complication that troubles me the most is the interaction between the Earth-blocking shield and the sun. When the sun is behind it, it seems there's no way to avoid it reflecting at least some of the sun's back onto the depot. Unless you put the active cooling on the shield, not the depot!
Quote from: OTV Booster on 01/21/2025 04:07 amQuote from: sdsds on 01/20/2025 03:19 amQuote from: Greg Hullender on 01/20/2025 01:01 amQuote from: ChrML on 01/19/2025 10:10 pmPossibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?Not dumb, but there are a lot of challenges to overcome to make this work. Since SpaceX already announced they aren't planning to do this, it hasn't attracted a lot of interest. Has SpaceX said Starship will never have actively cooled depots? Or have they only said they intend to first try passive cooling and/or frequent replenishment of boil-off? I imagine replenishment gets more costly when the depot is located beyond LEO. Also any BLEO depot likely needs to hold propellant longer. So that's where it seems like active cooling will eventually be implemented.Has a SOFI-MLI combo ever flown?Not AFAIK, but of course neither have the (re)deployable "cone" shields.Quote from: OTV Booster on 01/21/2025 04:07 amDoesn't MLI depend on she open space between layers?The MLI "quilt" (including an overlayer of protective aerocover fabric) gets glued (RTV) on top of the foam. You don't put foam between the layers. Quote from: OTV Booster on 01/21/2025 04:07 amUnless this is a real thing maybe active cooling and radiators are the best trade for extended ops in the warm clime of VLEO.You still want to minimize heat ingress to minimize the mass of any active system.
Quote from: Twark_Main on 01/21/2025 05:13 amQuote from: OTV Booster on 01/21/2025 04:07 amQuote from: sdsds on 01/20/2025 03:19 amQuote from: Greg Hullender on 01/20/2025 01:01 amQuote from: ChrML on 01/19/2025 10:10 pmPossibly a dumb question, but can't there be some kind of solar powered active cooling system? That radiates the excess heat on the side not pointing towards the sun, to reliquidify the boil-off?Not dumb, but there are a lot of challenges to overcome to make this work. Since SpaceX already announced they aren't planning to do this, it hasn't attracted a lot of interest. Has SpaceX said Starship will never have actively cooled depots? Or have they only said they intend to first try passive cooling and/or frequent replenishment of boil-off? I imagine replenishment gets more costly when the depot is located beyond LEO. Also any BLEO depot likely needs to hold propellant longer. So that's where it seems like active cooling will eventually be implemented.Has a SOFI-MLI combo ever flown?Not AFAIK, but of course neither have the (re)deployable "cone" shields.Quote from: OTV Booster on 01/21/2025 04:07 amDoesn't MLI depend on she open space between layers?The MLI "quilt" (including an overlayer of protective aerocover fabric) gets glued (RTV) on top of the foam. You don't put foam between the layers. Quote from: OTV Booster on 01/21/2025 04:07 amUnless this is a real thing maybe active cooling and radiators are the best trade for extended ops in the warm clime of VLEO.You still want to minimize heat ingress to minimize the mass of any active system.There seems to be a misunderstanding. Everybody knows the MLI cells are pumped full of vacuum before use.
How would the MLI handle MaxQ? I've never seen it directly exposed to aero forces, and if I understand the principals by which it operates, the flimsier it is, the better it does its job.
MLI "quilt" (including an overlayer of protective aerocover fabric)
True that: a shade even during active cooling. But, a simpler and less perfect (and hopefully more robust) shade becomes a more viable option. Shading requirements go from 'stop as much heat as we can' to 'what are the trades between cooler size and shade complexity".
Speaking at the Smallsat Symposium here Feb. 6, Gary Henry, a senior adviser at the Defense Innovation Unit (DIU) and a former SpaceX executive, said the agency was working with SpaceX to examine how Starship’s in-space refueling capabilities could support a broader range of users.[...]Another Starship application that DIU is exploring is what he called “novel responsive space delivery,” which he defined as delivering unique payloads using rockets. The Air Force Research Lab is already studying “rocket cargo” concepts, like Starship, through a Vanguard program for point-to-point transportationThe DIU approach involves using Starship for delivering cargo from orbit to the ground. “You’ve got payloads on orbit and you want to do something useful with them, and then you want to reenter them and bring them back and exploit them in some way,” he said.