As NASA pursues innovative, cost-effective alternatives to conventional propulsion technologies to forge new paths into the solar system, researchers at NASA’s Marshall Space Flight Center in Huntsville, Alabama, say nuclear thermal propulsion technologies are more promising than ever, and have contracted with BWXT Nuclear Energy, Inc. of Lynchburg, Virginia, to further advance and refine those concepts.
Part of NASA’s Game Changing Development Program, the Nuclear Thermal Propulsion (NTP) project could indeed significantly change space travel, largely due to its ability to accelerate a large amount of propellant out of the back of a rocket at very high speeds, resulting in a highly efficient, high-thrust engine. In comparison, a nuclear thermal rocket has double the propulsion efficiency of the Space Shuttle main engine, one of the hardest-working standard chemical engines of the past 40 years. That capability makes nuclear thermal propulsion ideal for delivering large, automated payloads to distant worlds.
“As we push out into the solar system, nuclear propulsion may offer the only truly viable technology option to extend human reach to the surface of Mars and to worlds beyond,” said Sonny Mitchell, Nuclear Thermal Propulsion project manager at Marshall. “We’re excited to be working on technologies that could open up deep space for human exploration.”
An NTP system can cut the voyage time to Mars from six months to four and safely deliver human explorers by reducing their exposure to radiation. That also could reduce the vehicle mass, enabling deep space missions to haul more payload.
Given its experience in developing and delivering nuclear fuels for the U.S. Navy, BWXT will aid in the design and testing of a promising, low-enriched uranium-based nuclear thermal engine concept and “Cermet” — ceramic metallic — fuel element technology. During this three-year, $18.8-million contract, the company will manufacture and test prototype fuel elements and also help NASA properly address and resolve nuclear licensing and regulatory requirements. BWXT will aid NASA in refining the feasibility and affordability of developing a nuclear thermal propulsion engine, delivering the technical and programmatic data needed to determine how to implement this promising technology in years to come.
The company’s new contract is expected to run through Sept. 30, 2019.
Nuclear-powered rocket concepts are not new. The United States conducted studies and significant ground tests from 1955 to 1972 to determine the viability of such systems, but ceased testing when plans for a crewed Mars mission were deferred. Since then, nuclear thermal propulsion has been revisited several times in conceptual mission studies and technology feasibility projects. Thanks to renewed interest in exploring the Red Planet in recent decades, NASA has begun new studies of nuclear thermal propulsion, recognizing its potential value for exploration of Mars and beyond.
In late September, the Nuclear Thermal Propulsion project will determine the feasibility of using low-enriched uranium fuel. The project then will spend a year testing and refining its ability to manufacture the necessary Cermet fuel elements. Testing of full-length fuel rods will be conducted using a unique Marshall test facility.
To date, all nuclear propulsion system designs have been derived from reactors fueled by highly enriched uranium. Recent advances in materials technology may provide a more affordable pathway to development of a nuclear rocket engine. A shift to low enriched uranium (LEU)—defined as a concentration of lower than 20 percent uranium-235—offers several potential advantages for a nuclear propulsion development program. Security regulations for an LEU system could be less burdensome on the project budget and schedule. Handling regulations for an LEU source are similar to those for a university research reactor, opening up the development effort to partnerships with industry and academia. The ability to affordably produce isotopically pure tungsten would be required for the development of a ceramic-metallic (cermet) fueled NTP system using LEU. This potentially “game changing” technology is key to the development of a cermet-based LEU NTP engine that could have extensibility beyond the current Mars campaign, and may provide the ability to develop these systems at an affordable level of budgetary commitment.
The overall goal of this game changing technology project is to determine the feasibility and affordability of an LEU based NTP engine with solid cost and schedule confidence. Initial project goals are to demonstrate the ability to purify tungsten to a minimum of 90 percent purity and determine the production costs at that purity level; to determine the technical and programmatic feasibility (pre-phase A level) of an NTP engine in the thrust range of interest for a human Mars mission; and to determine the program cost of an LEU NTP system and the confidence level of each major cost element.
BWXT has refocused its extensive nuclear reactor design, component manufacturing and fuel manufacturing development experience to assist other small modular reactor (SMR) and advanced reactor vendors in the development and deployment of their designs. This transition away from a strategy of developing its own proprietary SMR technology (BWXT mPower ®) gives BWXT the opportunity to share its extensive experience and to have the flexibility to pursue new market opportunities.