USRA provides expertise in space physical sciences to NASA by conducting and managing research in fluid physics, combustion, colloids/condensed matter, and modeling of biological systems.
Electricity and Heat for Planetary Exploration
USRA teams worked on a Radioisotope Thermoelectric Generator, an enabling technology for many planetary missions, that keeps electronic circuits and mechanical joints functional.
A Radioisotope Thermoelectric Generator (RTG) uses the heat of long-lived isotopes to produce 100 to 300 W of electricity and heat to keep electronic circuits and mechanical joints functional.
RTGs are an enabling technology for many planetary missions, including the New Horizons mission to Pluto, the Curiosity Rover on Mars and to the Cassini Mission to Saturn, which completed its 20- year mission in 2017. Earlier RTGs continue to power the Voyager 1 and 2 more than 40 years after launch.
USRA hosted three teams of students from ten U.S. universities, led by USRA’s Steve Herring and mentored by Jorge Navarro, Brian Gross, Eric Clarke and Ken Wahlquist (from Idaho National Laboratory-INL) who worked on three projects during the 2017 USRA/CSNR Summer Program in Idaho.
The first team explored the irradiation of Np-237 in the Advanced Test Reactor at the INL since older reactors that produced Pu-238 for earlier missions are no longer operating. Using neutron transport codes, the team found that the use of twenty seldom-used “I-Positions” around the periphery produced high-purity Pu-238 because of the low-energy neutron flux in those locations. Because of the number and size of the I-Positions, the ATR could be a significant source of future Pu-238.
The second team developed software to model the fueling and testing of the General Purpose Heat Source (GPHS) module at the Idaho National Lab to account for combinations of events such as simultaneous work on two or three units, for late deliveries of components and for breakdowns in test facilities.
The third team explored substitutes for the currently used Fine Weave Pierced Fabric (FWPF), which is a critical material used by NASA in their MMRTGs. FWPF is a carbon-carbon composite, which is very labor- intensive and expensive. The team presented a table of 10 currently available substitutes for FWPF.
Cryogenic Fluid Management in Space
USRA and its collaborators supported the development of reliable cryogenic fluid storage for use in propellant or life support systems necessary in space and planetary expeditions.
Integral to all phases of NASA’s projected space and planetary expeditions is affordable and reliable cryogenic fluid storage for use in propellant or life support systems. Cryogen vaporization due to heat leaks into the tank from its surroundings and support structure can cause self-pressurization that can be relieved through venting.
During long-duration on-orbit or on-surface storage, however, repeated venting of the vapor will result in significant propellant loss rendering the cost of long distance human space expeditions prohibitive. This has led to a significant impetus for developing innovative pressure control designs based on mixing of the bulk tank fluid together with some form of active or passive cooling to allow storage of the cryogenic fluid with zero or reduced boil-off.
The Zero-Boil-Off Tank (ZBOT) Experiments being performed and led by PI Dr. Mohammed Kassemi of CWRU, on the ARTS contract at NASA GRC are a series of small scale tank pressurization and pressure control experiments aboard the ISS.
Located in the Microgravity Science Glovebox, ZBOT uses a transparent volatile simulant fluid in a transparent sealed tank to delineate various fluid ow, heat and mass transport, and phase change phenomena that control storage tank pressurization and pressure control in microgravity. The hardware for ZBOT-1, the first of three hierarchical flight experiments, ew to the ISS in April 2017.
Experiments began in September 2017. The ZBOT-1 experiment consists of approximately 90 tests, which are being conducted over a 3- to 6-month period. These investigations are quantifying fluid ow and thermal strati cation during self-pressurization and mixing, thermal destratification, depressurization, and jet ullage penetration during the pressure control intervals. The digital imaging and machine readable textual/numerical data from the experiments are being continuously downloaded. The raw experimental data and a set of reduced data analyzed and processed by the ZBOT science team together, with the CFD simulations results, are being stored on the ISS Physical Sciences Open System Repository Server operated and maintained by NASA. Approximately one year after the end of ZBOT’s on-orbit operations, this data will be released for use to the scientific and engineering communities at large.
Dr. Mohammad Al-Hamdan
Center For Space Nuclear Research (CSNR)
The Center for Space Nuclear Research (CSNR), a USRA Institute at the Idaho National Laboratory, investigates transformative applications for the use of nuclear energy in space.
On Earth most flames are driven by gravity-dependent convection while in microgravity diffusion is the controlling mechanism. Microgravity combustion research provides safer materials for use in spacecraft, improved fire detection and suppression equipment for spacecraft, and improved combustion models that are being used for a variety of Earth-based applications, including transportation and energy conversion.
Cryogenic Fluid Management in Space
Integral to all phases of NASA's projected space and planetary expeditions is affordable and reliable cryogenic fluid storage for use in propellant or life support systems. During long duration on-orbit or on-surface storage, repeated venting of the vapor results in sinificant propellant loss rendering the cost of long distance human space expeditions prohibitive. This has led to the impetus to develop innovative pressure control designs to allow storage of cryogenic fluid with zero or reduced boil-off.
The Zero-BoilOff Tank (ZBOT) Experiments are being performed by members of Case Western Reserve University on the ARTS contract at NASA Glenn Research Center. These investigations are quantifying fluid flow and thermal stratification during self pressurization and mixing, thermal destratification, depressurization and jet ullage penetration during pressure control intervals. The raw experimental data and a set of reduced data analyzed and processed by the ZBOT science team together with the CFD simulations are being stored and maintained by NASA.
Plutonium -238 Production For Space Nuclear Power
The Multi-Mission Radioscope Thermoelectric Generator (MMRTG) is an enabling technology for current and future deep space missions. These power sources are particularly well suited to long-duration missions to the outer solar system, where alternative technologies, such as solar panels or fuel cells, are impractical. Given the interest in Mars and other destinations in the solar system, it is expected that the demand for radioisotope power for spacecraft will rise.
USRA researchers at the Center for Space Nuclear Research (CSNR) in Idaho Falls performed detailed research and analysis to understand and model the neutronic characteristics of the ATR. This important research is contributing to understanding how to optimize Pu-238 in the ATR will enable future demand for MMRTG fuel to be met, while also streamlining the production and assembly of MMRTGs for deep space missions.
Radio Frequency Mass Gauge Technology
USRA is actively involved supporting NASA GRC in the development of a Radio Frequency Mass Gauge (RFMG) for future space missions. The RFMG is a technology advancement for gauging cryogenic propellant mass in the reduced gravity environment that requires minimal modifications to the propellant storage tanks. Using the finite element modeling package COMSOL, Marius Asipauskas of USRA modelled the RF response of cryogenic propellant at various fill levels and reduced gravity values. This modelling is critical to the development of an accurate RFMG.