US space agency NASA announced it is partnering with the Pentagon’s DARPA to develop and test a nuclear-powered rocket engine to send astronauts on future missions to Mars. But some experts remain sceptical.

NASA is teaming up with the Pentagon’s research and development arm on a new nuclear thermal rocket (NTR), which it hopes will decrease transit time and reduce risks for astronauts in future missions to Mars.

In a press release on Tuesday, NASA Administrator Bill Nelson announced the break-through news, touting the advanced nuclear thermal propulsion (NTP) technology will be ready for demonstration “as soon as 2027.”

“With the help of this new technology, astronauts could journey to and from deep space faster than ever — a major capability to prepare for crewed missions to Mars,” the former Florida senator said in the statement.

Under the new agreement, NASA will assist the Defense Advanced Research Projects Agency (DARPA) on the development of the engine in a programme known as the Demonstration Rocket for Agile Cislunar Operations (DRACO) that was first launched in 2021.

DRACO Program Manager Dr. Tabitha Dodson tells TRT World that DARPA’s role “is to take the technology question off the table” and is doing so with a phased approach to the engine’s development.

According to Dodson, DARPA is currently working on conducting contract discussions and if terms are agreed upon, they will put a selected performer on contract in the next couple of months.

“There are several regulatory, environmental and safety processes that we are working on in parallel to ensure we will meet our FY27 launch timeline,” said Dodson.

Once all terms are met, the DRACO test flight, which will be an uncrewed demonstration in space, will take place as soon as 2027.

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Chemical vs. nuclear thermal rockets

As compared to a chemical rocket, a NTR uses the exact same propellant (liquid hydrogen) as chemical propulsion but the method to generate thrust is different. 

NTRs work by pumping the hydrogen through a reactor core where Uranium atoms split apart and release heat through fission. The heat converts the hydrogen from a liquid to a gas, which is expanded through a nozzle to produce thrust.

NTP allows a rocket to travel farther on less fuel­ and is twice as efficient as a chemical rocket, according to the US Department of Energy.

The amount of thrust generated by a chemical rocket, that combusts liquid hydrogen and liquid oxygen, is 450 seconds, which is at least half that of nuclear-powered rockets.

This is partly because when chemical rockets are burned, they produce water vapour, which is a much heavier byproduct than the hydrogen used in NTRs.

NTP rockets also reduce travel time to Mars by up to 25 percent, limit a flight crew’s exposure to cosmic radiation and zero gravity (zero-g), enable broader launch windows and allow astronauts to abort missions and return to Earth if necessary.

These benefits will help NASA meet its Moon to Mars Objectives and aid DARPA in its development of an experimental spacecraft (X-NTRV). 

However, Chair of the Department of Physics and Astronomy at Western University, Professor Pauline Barmby tells TRT World there are several concerns about nuclear propulsion.

“One big concern is that such an engine has to be launched from the surface of the Earth, so if a launch fails (e.g. in an explosion) or a vehicle re-enters the atmosphere in an uncontrolled way, there is the potential for contamination over large areas,” Barmby said.

Barmby drew a comparison to an earlier, different design for nuclear propulsion in space known as nuclear pulse propulsion, which essentially “had nuclear bombs as providing the propulsion.”

“Having nuclear weapons in orbit has obvious geopolitical and military implications, which is likely one reason this technology was never further developed,” Barmby said.

Science and technology journalist Brett Tingley told TRT World that another main concern raised by experts is "the possible radiation exposure that crews will experience due to being in close proximity to a working nuclear reactor aboard any future NTR spacecraft."

"However, NASA studies have found that 'exposure estimates are well in excess of baselined permissible exposure limits' and that risk mitigation strategies, such as advanced shielding technologies, countermeasures, and individual-based risk assessments are important to managing these potential risks to the astronauts on these missions," Tingley said.

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‘Power in our partnership’

NTP is not a new concept for the United States and neither is cooperation between NASA and DARPA. 

The country’s last engine tests occurred more than 50 years ago during the Nuclear Engine for Rocket Vehicle Application (NERVA) programme, which was cancelled due to budget cuts and Cold War tensions.

Since then, there have been no new major programs requiring such tests. Now DRACO is harnessing NERVA’s research to improve design, materials and fuels used in NTP systems.

Meanwhile, DARPA and NASA have a long history of collaboration including on the Saturn V rocket that transported the first astronauts to the Moon.

“Both of them are big government agencies with their own strengths and weaknesses, so when they work together, one would hope that they would combine their strengths and not their weaknesses,” Barmby said.

Additionally, the US Space Force has signalled its support for DRACO with the intent to provide the launch for the demonstration mission, according to Dodson.

Two years ago, NASA and the Space Force signed a five-page Memorandum of Understanding to formally team up in a variety of areas from spaceflight to planetary defence.

“NASA and the military share a long history dating back to the late 1950s. There is power in our partnership," Space Force Chief of Space Operations General John Raymond had told the press at the time.

But Barmby says she is “sceptical” about this latest collaboration and that NASA’s timeline for an “in-space demonstration by 2027” seems extremely optimistic.

“There have been many announcements of new space-related programmes that ultimately didn’t accomplish anything,” Barmby said. “However, DARPA has a history of supporting innovative ideas, so I think we can be cautiously excited about this.”

While sending humans to Mars has become one of the main priorities for government space agencies as well as private spaceflight firms, experts warn there is still a lot of work ahead to establish a human presence on the Red Planet. 

“There’s a big difference between having an in-space demonstration and a vehicle that could transport people,” Barmby said, warning that there are many other problems with sending humans to Mars that would still need to be solved.  

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Source: TRTWorld and agencies