The Hempsell Docking Ring (HDR) will be utilized to accommodate the most important task in all spaceflight operations: orbital cryogenic propellant transfer.
There will be two versions of the propellant transfer HDR, with both versions starting with the unpressurized HDR. The first version will be able to receive propellant and the other version will provide the propellant itself.
Reaction Engines, Ltd. (REL) has an excellent idea of how to transfer propellant using their Skylon spaceliner. It looks to be a variant of the old Apollo–style Probe and Drogue style of connectivity, where one probe loads the Liquid Hydrogen (LH2) fuel, whilst the other probe loads the Liquid Oxygen (LO2) oxidizer (see Video Clip 1).
We hope to adopt the same idea in space. The scenario envisioned is to dock a propellant refill module to an empty vehicle using the HDRs. Probes will then extend from the refill module into receptacles in the receiving vehicle. Once a solid connection has been established, three cryogenic fluids will be pumped aboard: LH2, LO2, and Liquid Nitrogen (LN2).
There will be two versions of the propellant transfer HDR, with both versions starting with the unpressurized HDR. The first version will be able to receive propellant and the other version will provide the propellant itself.
Reaction Engines, Ltd. (REL) has an excellent idea of how to transfer propellant using their Skylon spaceliner. It looks to be a variant of the old Apollo–style Probe and Drogue style of connectivity, where one probe loads the Liquid Hydrogen (LH2) fuel, whilst the other probe loads the Liquid Oxygen (LO2) oxidizer (see Video Clip 1).
We hope to adopt the same idea in space. The scenario envisioned is to dock a propellant refill module to an empty vehicle using the HDRs. Probes will then extend from the refill module into receptacles in the receiving vehicle. Once a solid connection has been established, three cryogenic fluids will be pumped aboard: LH2, LO2, and Liquid Nitrogen (LN2).
The Input Variant of the HDR includes all of the infrastructure needed to handle the cryogenics, and adds 32 kg to the overall mass, for a total of 73 kg.
The Output variant includes the infrastructure needed to deliver the cryogenics, and adds 43 kg to the overall mass, for a total of 91 kg.
Table 1 summarizes the masses.
Table 1: Propellant variant masses
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