The REFPROP program developed by the National Institute of Standards and Technology (NIST) is a widely-used database for industrial fluid properties, including propellants used for chemical rocket propulsion. For deep space applications, low-temperature propellants are of particular interest but accurate fluid property data was scarce or unavailable to the industry. Recently, NASA MSFC has funded several research programs (including this proposal's phase I contract) to develop capabilities of handling and measuring the physical, thermodynamic, and system properties of Modified Oxides of Nitrogen (MON), which is Nitrogen Tetraoxide (NTO) blended with various percentages of Nitrous Oxide. High-MON blends (15-30% NO) have a significantly lower freezing point than neat NTO and promise to enable cold-propellant operation in hypergolic rocket engines when paired with Monomethyl Hydrazine (MMH). The fluid property data resulting from these studies would best serve the engineering community if made available in the REFPROP program from the NIST and this proposal seeks to author the collected data into a freely-available library under NIST direction.
Additionally, although the freezing point of MMH approaches -60°C and it should be usable with MON down to -40°C, the viscosity of MMH increase rapidly below 0°C. This may cause flow and mixing problems that can inhibit ignition and steady operation. In a previous Department of Defense program, it was demonstrated that adding a compound to a similar fuel resulted in lower viscosity without negatively impacting combustion efficiency. To characterize the results of blending MMH similarly, this proposal also seeks to investigate key physical properties of MMH-blends at cold temperatures and perform hypergolic ignition and hypergolic performance testing with MON-25. Like the MON data, the results of these studies will be authored into the REFPROP libraries for general distribution.
The information obtained by this proposal will directly benefit the currently active TALOS program managed by the Marshall Space Flight Center as well as a NASA JPL mission to Jupiter's moons currently being planned. Both of those programs are targeting MON-25/MMH operating at low temperatures.
Providing MON-25 and MMH-blend data via REFPROP to the propulsion community will provide benefits to any company or agency interested in developing systems that need low-temperature chemical propulsion.