Measurement of Spray Heat Transfer for In-Space Cryogenic Transfer Systems

The Parabolic Flight Experiments for Measurement of Spray Heat Transfer During Cryogen Chilldown of Receiver Tank aim to support refueling of spacecraft. Through parabolic flight tests, researchers will evaluate cryogenic tank chilldown via spray injection and fill methods that avoid venting precious liquid directly into space. Researchers will use data collected during flight testing for development of experimentally validated universal direct-cryogenic spray correlations. These correlations will potentially be integrated into the design and analysis of future in-space cryogenic transfer systems for use in microgravity and missions to the Moon and Mars. 

Problem Statement 
Accurate design of cryogenic propellant transfer systems where two-phase cryogenic flow occurs (including transfer lines and propellant tanks) requires reliable correlations at the fundamental level. However, the thermal/fluid design codes currently used to design cryogenic propellant transfer systems do not address all phenomena, such as spray trajectory, droplet heat and mass transfer, and spray boiling at the wall. 

Additionally, all available spray boiling correlations are based on room temperature fluids, not cryogens. Therefore, there is a need for direct cryogenic correlations that accurately captures the fundamental heat and mass transfer rates associated with tank chilldown and fill. 

Technology Maturation 
Parabolic flight experiments with Zero Gravity Corporation will gather lunar, Martian, and microgravity steady-state cryogenic spray heat transfer data over two flight campaigns. By measuring the relationship between spray heat transfer and wall temperature as a function of gravity, mass flow rate, pressure, inlet temperature, and spray droplet parameters, the data are expected to enable the development of experimentally validated reduced gravity cryogenic spray heat transfer correlations. The correlations will be made available for integration into NASA’s lumped node fluid/thermal codes that are used for design and analysis of cryogenic tank chill and fill. These flight test aim to advance the innovation from technology readiness level (TRL) 4 to TRL 5. 

This work is a continuation of previous flight testing under T0291-P and T0041-P.

- Reduced waste: Improves chilldown and fill methods to avoid venting cryogenic fluid into space 
- Efficient refueling: Provides basis for more accurate universal cryogenic spray heat transfer correlations to improve design and analysis of cryogenic tank chill and fill 

Future Customers
- Cryogenic propellant management for NASA and commercial space missions, including: 
- Nuclear thermal propulsion systems 
- Chemical propulsion stages 
- Ascent stages 
Descent stages 
In-space fuel depots

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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