ShareChanges in the use of cryogenic propellants in space
Near-term exploration beyond low Earth orbit will require the use of cryogenic propellants and in-space cryogenic propellant storage durations will exceed our current capabilities by at least two orders of magnitude. This will require the development of a whole range of technologies.
According to W. Notardonato from Kennedy Space Centre , a new phase in US human space exploration is dawning with the retirement of the space shuttle fleet. Near-term exploration beyond low Earth orbit will require the use of cryogenic propellants and in-space cryogenic propellant storage durations will exceed our current capabilities by at least two orders of magnitude. This will require the development of a whole range of technologies, including large-scale insulation systems, microgravity fluid control and active thermal control of cryogens for extended duration zero boil-off.
One of the challenges is to use common fluids in several operations in order to reduce space use and mass. Liquid hydrogen and oxygen are already used in primary in-space propulsion applications and exhibit the highest performance of any chemical propellant. They are ideal candidates for secondary propulsion, but require long-duration cryogenic storage. Currently, hypergols, another type of propellant, usually play that role due to their storability, reliability and a successful history of use. However, advances in active and passive thermal control in the near future should enable long-duration cryogenic storage and make liquid hydrogen and oxygen as storable as their competitor.
Active control means control of both the state of the cryogen and that of the position of the fluid in the tank. This implies being able to regulate or govern the state of the propellant, including increasing the bulk fluid temperature or the system pressure when desired.
In his article, Notardonato even proposes the concept of a propellant-production and liquefaction spacecraft (PPLS) that could electrolyse water and liquefy hydrogen and oxygen for storage in spacecraft propellants. Many refrigeration cycles could be used for the liquefaction process, but the model he proposes considers two of them: a closed cycle multiple-stage Brayton system or a more conventional open-cycle liquefier. In all cases, very large solar arrays would be necessary to power the cooling process, until space-based nuclear power is developed.
*Notardonato W. Active control of cryogenic propellants in space, Cryogenics, April-June 2012
doi:10.1016/j.cryogenics.2012.01.003
One of the challenges is to use common fluids in several operations in order to reduce space use and mass. Liquid hydrogen and oxygen are already used in primary in-space propulsion applications and exhibit the highest performance of any chemical propellant. They are ideal candidates for secondary propulsion, but require long-duration cryogenic storage. Currently, hypergols, another type of propellant, usually play that role due to their storability, reliability and a successful history of use. However, advances in active and passive thermal control in the near future should enable long-duration cryogenic storage and make liquid hydrogen and oxygen as storable as their competitor.
Active control means control of both the state of the cryogen and that of the position of the fluid in the tank. This implies being able to regulate or govern the state of the propellant, including increasing the bulk fluid temperature or the system pressure when desired.
In his article, Notardonato even proposes the concept of a propellant-production and liquefaction spacecraft (PPLS) that could electrolyse water and liquefy hydrogen and oxygen for storage in spacecraft propellants. Many refrigeration cycles could be used for the liquefaction process, but the model he proposes considers two of them: a closed cycle multiple-stage Brayton system or a more conventional open-cycle liquefier. In all cases, very large solar arrays would be necessary to power the cooling process, until space-based nuclear power is developed.
*Notardonato W. Active control of cryogenic propellants in space, Cryogenics, April-June 2012
doi:10.1016/j.cryogenics.2012.01.003