does anyone know what is used to insulate the super-chilled fuel storage tanks? I’m from the area near Boca Chica beach and I can tell you it is way hotter than Florida or McGregor. as of this McGregor TX is 82F/28C wile Brownsville TX is 91F/32C. the thing i was interested in is would it be a cheaper long-term for SpaceX to use the same insulation that parkers solar probe used to keep temps low and thereby reduce the cooling power/equipment upkeep costs. the tanks i saw on site don’t look like there insulated at all, or even putting them 60 feet underground where the average temp stays at 62f-72F ish in that area of Texas.
The best physical insulation is Aerogel. It’s like $5 per ft^2 for a pad 2-3 cm thick. So if you wanted to insulate your home using the stuff to the same depth as the standard fiberglass batting, it would probably cost more than your home. Thus, unless your ROI timescales are on the order of decades it’s not worth it (or unless you’re a crazy expensive space ship with special insulation needs, then it’s relatively cheap).
The Parker probe didn’t use aerogel because it would have melted. The carbon foam Parker used wasn’t a better insulator, just the only one that could stand that much heat.
Most likely the storage tanks at Boca Chica are double walled with a vacuum acting as insulation. That set up is actually pretty unbeatable for insulation. So, I doubt they’ll need more.
When thinking about temperature difference for cryogenically stored fuels, you have to look at the difference relative to the storage temperature. These will be stored as liquids.
methane is liquid from -182°C to -161.5°C
oxygen is a liquid from -218.8°C to -183°C
Thus the difference between Brownsville 32 - (-218.8) = 250.8°C vs McGregor 28 - (-218.8) = 246.8°C at worst is really only (246.8 - 250.8) / 250.8 = 1.6%
Here’s a picture of aerogel I found on the internet. I once saw a picture with an ice cube on top and the bunsen burner under the aerogel. Unfortunately, I can no longer find it, but you get the picture.
Some Silica Aerogels will only transmit 0.01 W/mK, which means that for two mediums of 100 degrees Kelvin in temperature difference, a layer of aerogel of 1 metre thickness (~1 foot) will only transmit 1 Joule a second per square metre (~3 x 3 feet).
Aerogel is also the lightest manmade material with Graphene Aerogel weighing 0.16 Kilogramms per cubic metre. For reference: That’s about 3 x 3 x 3 feet and if you fill that with water it weighs one metric tons (1’000 kilogramms).