11:15 〜 11:30
[PPS01-08] Titan Sample Return Using In-Situ Propellants
キーワード：Titan, Mission Concept, Sample Return, Radioisotope Power
Titan is unique in the outer solar system in that it is the only moon with a thick atmosphere, and the only body in the solar system outside the Earth with liquid seas on its surface. A possible next step after Dragonfly's exploration and a possible New Frontiers Titan orbiter is sample return, to bring Titan material to Earth. Such a mission would be essentially impossible with a conventional architecture, but Titan is attractive for in-situ propellant production. With water, liquid methane, and ethane easily available, Titan is a rocket scientist’s dream for propellants, as recognized by Arthur C. Clarke and others.
One important development is the recognition that acquiring liquid methane from the seas is not actually necessary, and is in fact rather geographically restrictive. Instead, simple thermodynamic processing (analogous to running a domestic dehumidifier on Earth) can easily condense methane out of the atmosphere, at any location. The mission would use a radioisotope power system : with 100-200 W of power, it is possible to generate about 1kg/day of liquid methane fuel.
It is assumed that the mission can access water-ice-dominated surface material that can be excavated, melted, and electrolyzed to yield oxygen. Titan temperatures permit this oxygen to be easily stored in liquid form. The electrolysis process is energy-intensive, and becomes the rate-limiting step in the in-situ propellant production. Possible landing sites considered are the Selk impact crater (target of Dragonfly, and known to have some water-bearing material exposed) and the Doom Mons candidate cryovolcano.
LOX/Methane is a high-performance rocket propellant combination, with a specific impulse around 325s. Previous studies suggest ascent and Earth-return delta-Vs required are around 3300 m/s and 4600 m/s respectively. The Titan ascent trajectory is an interesting new problem, in that the gravity and drag losses are quite different from those of terrestrial launch vehicles, and non-rocket means for initial ascent may be attractive.
One important development is the recognition that acquiring liquid methane from the seas is not actually necessary, and is in fact rather geographically restrictive. Instead, simple thermodynamic processing (analogous to running a domestic dehumidifier on Earth) can easily condense methane out of the atmosphere, at any location. The mission would use a radioisotope power system : with 100-200 W of power, it is possible to generate about 1kg/day of liquid methane fuel.
It is assumed that the mission can access water-ice-dominated surface material that can be excavated, melted, and electrolyzed to yield oxygen. Titan temperatures permit this oxygen to be easily stored in liquid form. The electrolysis process is energy-intensive, and becomes the rate-limiting step in the in-situ propellant production. Possible landing sites considered are the Selk impact crater (target of Dragonfly, and known to have some water-bearing material exposed) and the Doom Mons candidate cryovolcano.
LOX/Methane is a high-performance rocket propellant combination, with a specific impulse around 325s. Previous studies suggest ascent and Earth-return delta-Vs required are around 3300 m/s and 4600 m/s respectively. The Titan ascent trajectory is an interesting new problem, in that the gravity and drag losses are quite different from those of terrestrial launch vehicles, and non-rocket means for initial ascent may be attractive.