Cryogenic propellant depot and integral sunshield

Abstract

A cryogenic propellant depot and sunshield are provided for operation in earth orbit to fuel or refuel other space vehicles. The sunshield is deployed to effectively mitigate solar radiation emanating from the earth and the sun thereby providing a long term storage solution for cryogenic fluids prone to boil-off. The depot has supporting subsystems to include station keeping equipment and communication equipment so that the depot can be independently controlled. Inflatable booms are used to deploy the sunshield in a desired pattern around the depot.

Description

FIELD OF THE INVENTION[0001]The present invention relates to cryogenic propellant depots used for the fueling of space vehicles in earth orbit, other orbits, deep space or near celestial bodies, and more particularly, to a cryogenic propellant depot placed in space having an integral sunshield to optimize storage of liquid cryogens by shielding the depot from solar radiation.BACKGROUND OF THE INVENTION[0002]Space exploration is limited by a number of factors that prohibit the distance to which space vehicles can travel from the earth to the rest of the solar system. One obvious limitation is the size of a payload that can be placed into earth orbit and beyond. Tremendous power and fuel requirements are required to place larger payloads into earth orbit, and to then project those payloads to other locations in the solar system, such as the moon or Mars. The proposed NASA Ares-5 rocket is capable of delivering approximately 69 tons to earth escape velocity. However, NASA's current arc...

AI Technical Summary

Benefits of technology

[0006]To minimize boil off of the liquid, a low conductivity support truss and thermal isolation gas reservoir is placed between the equipment deck and the tank. To minimize structural mass and maximize the depot propellant capacity within payload fairing envelopes, the thermal isolation gas reservoir and cryogenic tank share a common, insulated bulkhead.

[0007]The sunshield is stored on or adjacent to the equipment deck. Once the depot is in orbit, the sunshield is deployed around the cryogenic tank to thereby minimize heating from the sun and earth. The sunshield deflects radiated heat from these sources to deep space. The sunshield provides a passive, structurally reliable, and affordable solution to minimize boil off of the liquid within the tank.

[0008]Once the sunshield has been deployed, the entire depot slowly spins about its longitudinal axis to provide centrifugal acceleration. The station-keeping propulsion system is used to initiate and control this spin. The centrifugal acceleration provides positive gas / liquid separation by forcing liquid outward toward the tank sidewall, resulting in a gaseous ullage in the center of the tank. Cryogenic fuel management within the tank is greatly improved as the gaseous core may be more effectively vented then a liquid—gas slurry. This venting is similar to the settled ullage venting of existing cryogenic upper stages. Centrifugal settling also simplifies propellant acquisition and transfer, thereby avoiding the need for additional liquid acquisition devices that would otherwise be required to separate gas and liquid prior to liquid transfer. Propellant transfer into and out of the depot is accomplished by differential pressure between the tank and the receiving vehicle / tank; very similar to the manner in which launch vehicle engines are fueled on existing cryogenic stages.

[0009]The well insulated depot, by incorporation of the sunshield, the thermo-isolation gas reservoir, tank geometry and other heat reduction measures enables the depot to stop rotating for docking operations without concerns regarding excessive gas and liquid heating that otherwise might be a concern for a tank that was subject to increased boil-off because of its exposure to solar and earth heating.

[0012]By the robust design of the present cryogenic depot and integral sunshield, inter-planetary space missions are no longer limited by launch vehicle performance. Smaller, less costly launch vehicles can be used, and space explorations can be extended much farther into the solar system. The depot of the present invention enables near term implementation to support the diverse needs in the space industry, thereby reducing costs for all aspects of space utilization. Other features and advantages of the present invention will become more apparent from a review of the following detailed description, taken in conjunction with the drawings.

Problems solved by technology

Space exploration is limited by a number of factors that prohibit the distance to which space vehicles can travel from the earth to the rest of the solar system.

One obvious limitation is the size of a payload that can be placed into earth orbit and beyond.

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