HIGH TEMPERATURE REUSABLE VACUUM-JACKETED INSULATION FOR ROCKET MISSIONS
A number of techniques, structures, and materials for thermally insulating a cryogenic propellant tank barrel section are presented. Thermal insulation for a tank, such as tanks for use in space flight missions, may be a dual wall vacuum jacket system where one wall is the propellant tank wall and the other wall is a metallic foil that is welded to portions of the propellant tank wall. The metallic foil may act as a vapor barrier and a vacuum seal. A structural and breathable insulation that is durable and functional in a range from cold to relatively high temperatures may be used to maintain a standoff distance between the two walls. The volume between the propellant tank wall and the metallic foil may be purged with a gas that has a liquefaction temperature greater than that of the cryogenic propellant that will be in the propellant tank during operations.
1 . A reusable, high-temperature cryogenic insulation system for a cryogenic tank, the system comprising:
a tank shell having an interior surface and an exterior surface, wherein the interior surface is configured to contain a cryogenic fluid;
a metallic foil covering at least a portion of the exterior surface of the tank shell;
a gas-permeable thermal insulation occupying a cavity between the exterior surface of the tank shell and the metallic foil;
a gas in the cavity that condenses, via thermal conduction, when the cryogenic fluid is in the cryogenic tank and resultantly creates a vacuum or a reduced pressure in the cavity, wherein the metallic foil has a resilience that allows for a distance between the exterior surface of the tank shell and the metallic foil to change based on the reduced pressure of the gas in the cavity.
2 . The system of claim 1 , further comprising a valve configured to control flow of the gas in and out of the cavity.
3 . The system of claim 2 , wherein the reduced pressure of the gas is based, at least in part, on the flow of the gas and a temperature of the gas.
4 . The system of claim 2 , further comprising a control system configured to operate the valve to maintain a pressure of the gas to be at substantially a vacuum for i) a launch pad hold and launch stage, ii) an orbital coast stage, and iii) a reentry stage.
5 . The system of claim 2 , further comprising a control system configured to operate the valve to purge the cavity between the exterior surface of the tank shell and the metallic foil with a cooling fluid.
6 . The system of claim 1 , wherein the distance between the exterior surface of the tank shell and the metallic foil is further based on a pressure of the gas relative to pressure exerted on the metallic foil from outside the system.
7 . The system of claim 1 , wherein the distance between the exterior surface of the tank shell and the metallic foil is further based, at least in part, on a presence of the cryogenic fluid within the interior surface of the tank shell.
8 . The system of claim 1 , wherein the tank shell is a portion of a fuel system for a secondary stage of a rocket.
9 . The system of claim 1 , wherein the gas-permeable thermal insulation comprises a fiberglass mat embedded with a silica aerogel.
10 . The system of claim 1 , wherein the metallic foil has a thickness of less than about 0.05 inches to provide for the resilience.
11 . The system of claim 1 , further comprising a thermal protection system (TPS) at least partially covering the metallic foil.
12 . The system of claim 1 , wherein the tank shell is configured, via thermal conductivity of the gas-permeable thermal insulation when the cavity is in the vacuum or the reduced pressure, to be a heat sink for heat generated during a reentry stage of space flight.
13 . A method of operating a reusable, high-temperature cryogenic insulation system for a cryogenic tank of a rocket, the method comprising:
providing a gas to a gas-permeable thermal insulation that occupies a cavity between an exterior surface of the cryogenic tank and a metallic foil that overlays the cryogenic tank;
at least partially filling the cryogenic tank with a cryogenic fluid;
allowing the cold temperature of the cryogenic fluid in the cryogenic tank to condense the gas into a liquid so as to create a vacuum or a reduced pressure in the cavity;
launching the rocket while the cryogenic fluid in the cavity remains condensed in the liquid;
allowing the vacuum or the reduced pressure in the cavity to equalize with the pressure of the vacuum of space during an orbital coast phase for the rocket, wherein the equalization leads to an increase in a distance between the exterior surface of the cryogenic tank and the metallic foil; and
maintaining the vacuum or the reduced pressure in the cavity during a reentry phase for the rocket so as to decrease the distance between the exterior surface of the cryogenic tank and the metallic foil.
14 . The method of claim 13 , further comprising operating a valve that controls a flow in and out of the cavity to i) allow the cold temperature of the cryogenic fluid in the cryogenic tank to condense the gas into the liquid, ii) allow the vacuum or the reduced pressure in the cavity to equalize with the pressure of the vacuum of space during the orbital coast phase for the rocket, and iii) maintain the vacuum or the reduced pressure in the cavity during the reentry phase for the rocket.
15 . The method of claim 14 , further comprising operating the valve to purge the cavity between the exterior surface of the cryogenic tank and the metallic foil with a cooling fluid.
16 . The method of claim 13 , further comprising operating the cryogenic tank as a heat sink for heat generated during the reentry phase.
17 . The method of claim 13 , wherein the cryogenic tank is a portion of a fuel system for a secondary stage of the rocket.
18 . The method of claim 13 , wherein the gas-permeable thermal insulation comprises a fiberglass mat embedded with silica aerogel.
19 . The method of claim 13 , wherein the metallic foil has a thickness of less than about 0.05 inches to provide the metallic foil with resilience that allows the metallic foil to billow out and increase the distance between the exterior surface of the cryogenic tank and the metallic foil.
20 . The method of claim 13 , wherein the gas has a condensation temperature that is greater than the condensation temperature of the cryogenic fluid.