Aggressive Nuclear Propulsion R&D Effort Needed To Send Humans to Mars in 2039 – SpacePolicyOnline.com
A new report from the National Academies of Science, Engineering, and Medicine concludes that if the goal is to send humans to Mars in 2039, an aggressive nuclear propulsion research and development program will be needed and no time to lose.
NASA gave the committee a base mission to assess the maturity of the Nuclear Thermal Propulsion (NTP) and Nuclear Electric Propulsion (NEP) technologies to get a crew of four to and from Mars.
The basic parameters were introduced in 2039 with a total travel duration of no more than 750 days. Residence time on the surface of Mars of 30 days; crew of four, two of whom would land on Mars; separate cargo and crew vehicles with the same propulsion system, with cargo vehicles arriving on Mars prior to the crew’s first departure from Earth; and vehicle systems, cargo, and propellants delivered by multiple launch vehicles to a collection point in orbit or in cislunar space.
Co-chaired by Robert (Bobby) Braun of the Jet Propulsion Laboratory and Roger Myers of R. Myers Consulting, who retired from Aerojet Rocketdyne after leading his Advanced In-Space programs, the committee concluded there was still much left Doing research and development is done before decisions are made.
The study did not look at the organization, funding, or other factors required for a human mission to Mars, only an assessment of the nuclear propulsion technologies that could make it possible.
Spaceships can only be launched to Mars if the planets are correctly aligned. The conjunctive opportunities are 26 months apart and require the lowest power (“Delta V”) of the drive system. All robotic Mars missions launched so far have been carried out during conjunctions. However, spaceships can be fired to Mars when the planets are in opposition when a flyby of Venus is added. Opposition missions require more power from the propulsion system, but reduce total travel time, an important consideration for the health and safety of the crew.
According to the report, a conjuncture class mission launched in 2039 would take 916 days, round-trip: 210 days, 496 days on the surface for the planets to realign, and 210 days at home. A comparison mission of the opposition class would start in 2037 and last 650 days: 217 days on the way, 30 days on the surface and 403 days home via a Venus swingby.
To achieve these trigger times, an NEP system would have to be supplemented by a chemical propulsion system in space (liquid methane and liquid oxygen), while an NTP system on its own would be sufficient.
Extensive research into NTP was carried out under the Rover / NERVA program in the 1960s, but much of this expertise has been lost and design problems remain unsolved.
“NTP development faces four major challenges that can be met with adequate resources to carry out the base mission in 2039. As mentioned above, this challenge is to (1) heat the propellant at the reactor outlet to approximately 2700 K for the duration of each combustion, (2) long-term storage of liquid hydrogen in space with minimal loss, (3) the lack of adequate ground-based testing facilities and (4) the ability to quickly bring an NTP system to full operating temperature (preferably in 1 minute or less). “
Concerns about the possibility of increased nuclear proliferation here on earth in the processing of high-enriched uranium (HEU) have led to calls for high-enriched low-enriched uranium (HALEU) to be used instead. HEU is fortified with 20 percent or more U-235, versus 1 percent in naturally occurring uranium. HALEU is enriched to 5-20 percent. The Space Policy Guideline 6 (SPD-6) of the Trump administration of December 2020 on nuclear power and propulsion in space (SNPP) had a strong effect in favor of HALEU. The HEU should only be used if a mission would otherwise not be feasible.
However, the ASEB committee concluded that there is not enough information available to make an informed decision about HEU versus HALEU and urged NASA and the Department of Energy to “conduct a comprehensive and expeditious assessment” by the end of this year, when the goal is achieved, a system will be ready for launch in 2039.
The committee was not optimistic that even an aggressive R&D program could prepare NEP for 2039.
Much remains to be done in both approaches and there is no time to be lost.
NEP and NTP systems have great potential to facilitate human exploration of Mars. However, using either system to complete the base mission by 2039 will require an aggressive research and development program. Such a program would have to begin with NASA making key architecture and investment decisions in the coming year. In particular, NASA should develop consistent performance metrics and technical expertise to enable an objective comparison of the ability of NEP and NTP systems to meet the requirements for a base mission launch in 2039.
In a statement, Braun said, “A significant acceleration in technology maturation is required if NASA and its partners are to complete this mission within the specified timeframe.”
Congress has allocated considerable sums of money to the development of NTP in recent years. For example, the fiscal year 2011 budget has allocated US $ 110 million to NTP, of which no less than US $ 80 million will be used to design test items to enable a flight demonstration. This is actually a step backwards from fiscal 2020, which also saw $ 110 million provisioning. However, $ 80 million was earmarked for designing a flight demonstration through 2024, not just designing test items to enable a demonstration.