SBIR-STTR Award

Rocket propulsion for deep space applications typically use liquid propellants for axial stage and attitude control systems. The most common propellants are hydrazine (N2H4) and monomethylhydrazine (MMH) (CH3N2H3) for the fuels, and nitrogen tetroxide (NTO) (N2O4) for the oxidizer. The freezing points of both hydrazine and NTO approach room temperature and require on-board electrical heaters for the propellant tanks. MMH has a much lower freezing point but is used with NTO as an oxidizer so propulsion systems still require significant heater power. MON-25, an oxidizer composed of NTO mixed with 25% nitric oxide (NO), has a freezing point comparable to MMH. MMH and MON-25 propellants can allow a thruster to operate at -40°C. However, the properties of MON-25 have not been fully defined, specifically at temperatures below 5°C . This project will further characterize the properties of MON-25 and MON-30 oxidizers so they can be used with confidence at cold temperatures in space flight systems. These propellants will save considerable power required for propellant heaters, which will permit larger science payload and enhance the mission capability of deep space probes. The low-temperature oxidizers may also find use in lunar landing and ascent systems where sunlight is intermittent or absent.

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.nbsp; For deep space applications, low-temperature propellants are of particular interest but accurate fluid property data was scarce or unavailable to the industry.nbsp; Recently, NASA MSFC has funded several research programs (including this proposal#39;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.nbsp; 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-availablenbsp;library under NIST direction.nbsp;Additionally, although the freezing point of MMH approaches -60deg;C and it should be usable with MON down to -40deg;C, the viscosity of MMH increase rapidly below 0deg;C.nbsp;This may causenbsp;flow and mixing problems that can inhibit ignition and steady operation.nbsp; In a previous Department of Defense program, it was demonstrated that adding a compound to a similar fuel resulted innbsp;lower viscosity without negatively impacting combustion efficiency.nbsp; To characterize the results of blending MMH similarly, this proposal also seeks to investigatenbsp;key physical properties of MMH-blends at cold temperatures andnbsp;perform hypergolic ignition and hypergolic performance testing with MON-25.nbsp; Like the MON data, the results of these studies will be authored into the REFPROP libraries for general distribution.