WASHINGTON – NASA must pursue the “aggressive” development of nuclear propulsion technologies in space if the agency wants to use them for human missions to Mars over the next two decades, a report by a committee from the National Academy concluded.
A Feb. 12 study by the National Academies sponsored by NASA said that both nuclear thermal propulsion (NTP) and nuclear electric propulsion (NEP) must overcome significant hurdles for their use in a fictional human mission to Mars in 2039. Such systems could shorten the travel time of expeditions to Mars.
“Nuclear propulsion technology in space shows great potential to facilitate human exploration of Mars,” Bobby Braun, director of planetary science at the Jet Propulsion Laboratory and co-chair of the committee that wrote the report, said in a statement. “However, a significant acceleration in the pace of technology maturation is required if NASA and its partners are to complete this mission within the stated timeline.”
Of the two technologies, the report was more optimistic about NTP, where a nuclear reactor heats a fuel such as liquid hydrogen to generate thrust. “An aggressive program could develop an NTP system capable of carrying out the base mission in 2039,” the report concluded.
However, that technology faces several challenges outside of the nuclear reactor itself. They can, among other things, heat the propellant to the required temperature of 2700 Kelvin and bring the system to operating temperature within a minute. Other challenges include a lack of ground testing facilities for NTP systems and difficulties in storing liquid hydrogen for the duration of a mission.
NEP, where a nuclear reactor generates power for electric thrusters, must scale up its power and thermal management systems to levels well beyond what has been demonstrated to operate with megawatt-class reactors. However, the report notes that little progress has been made in relevant technologies since 2005 and the work done is limited to lower-powered systems.
“As a result of the low and intermittent investment over the decades, it is unclear whether even an aggressive program would be able to develop a NEP system capable of carrying out the base mission in 2039,” concluded the report. Nonetheless, NASA recommended “boosting technology development” for NEP systems.
NASA is struggling to balance conflicting priorities for nuclear and propulsion development. In addition to NTP and NEP, the agency has also worked on surface fission energy systems, such as Kilopower, that would provide energy on the surface of the Moon or Mars. The agency has tried to advance work on Kilopower because that technology has short-term applications for the Artemis lunar exploration program, which does not require nuclear propulsion.
However, proponents of the NTP in Congress have inserted the language of the report into the credit accounts, forcing NASA to spend money on that effort. That also includes the fiscal year 2021 credit bill passed in December that ordered NASA to spend $ 110 million of its $ 1.1 billion on space technology to develop NTP, of which $ 80 million would go toward “designing.” of test items that enable a flight demonstration. ”NASA has not yet announced plans for a flight demonstration of an NTP system.
At a Jan. 27 meeting of the NASA Advisory Board’s Technology Committee, members noted that they had previously advised NASA to prioritize surface fission over NTP because of its uses for Artemis.
We totally agree, “replied Jim Reuter, NASA associate administrator for space technology.” The direction of Congress has been nuclear thermal propulsion. “He said NASA is continuing to request the development of NTP technology because of funding, forcing a surface nuclear power to be delayed until later in the fiscal year.
“Nuclear thermal propulsion is of great interest from a number of viewpoints, both NASA and DOD,” he added. “It’s a very good technology.”
The Trump administration also raised nuclear power above NTP and NEP in its last weeks. Space Policy Guideline 6, released on December 16, established a strategy for the development of nuclear space technologies, including both power and propulsion. It prioritized nuclear power on the surface over nuclear propulsion, as the latter is not needed for the Artemis program.
“Those things are important for getting to Mars,” said a senior government official on nuclear propulsion at the time the strategy was released, “but first we do the moon and use Earth’s capabilities and technologies to get that foothold. to get on the moon. “
It is not clear what relevance this strategy has under the Biden government, which has taken few measures with regard to space policy.