Demonstration of Optimal Chilldown Methods for Cryogenic Propellant Tanks in Reduced Gravity

The PIs group has previously performed many terrestrial chilldown and microgravity parabolic flight chilldown experiments for pipes. More difficult to model and in most cases more important for the propellant thermal management is the chilldown of the receiver tank. The receiver tank is the most massive component of the system to be chilled down and, therefore, takes much more time to chill down and thus more cryogen consumption. As a result, the time and propellant spent during chilldown will mostly be dictated by how fast the tank can be chilled down. But at this time there have been no studies on tank chilldown in zero gravity. Previous tank chilldown studies have been limited to just 1g conditions and were very scarce with only two data sets available and the experiments were poorly executed. The proposed project seeks to fill this void and close this gap by conducting reduced gravity experiment for cryogenic chilldown of a receiver tank in reduced gravity, analyzing data, developing models, and then suggest optimal tank chilldown methods.
This work builds on prior work under T0172. Problem Statement In-Space Tank-to-Tank Transfer is composed of three operational elements 1) high efficiency line chilldown, 2) high efficiency tank chilldown, and 3) no-vent fill of the receiver tank. When transferring cryogen from a supply tank to a receiver tank, the transfer line (i.e. pipe and valves) and receiver tank are at high temperatures compared to that of the liquid propellant. Chilldown is the process of introducing the cryogen into the system to cool the hardware down to the liquid temperature. The flowing propellant boils off as it cools the line and tank. Since the propellant is only storable and useful to the engine in pure liquid form, this vaporized propellant is vented overboard and considered lost. Since each of the three elements is a two-phase flow process,

This methodology to be demonstrated in flight provides a safe and efficient way of performing cryogenic tank chill-down in reduced gravity, which is an essential step prior to tank-to-tank propellant transfer needed for Human Mars Missions. It will benefits future NASA missions.

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