Yesterday, NASA Administrator Bill Nelson announced a collaboration between the Defence Advanced Research Projects Agency (DARPA) and NASA to re-develop nuclear propulsion capabilities. The proposed project would enable fast, efficient travel to Mars and beyond.

What is Nuclear Propulsion

NASA’s NERVA Engine on Test Stand

Nuclear Propulsion has been one of the most highly anticipated forms of space travel since we first walked among the stars.

Simply, Nuclear Thermal Propulsion uses a miniaturised nuclear reactor as the main element in the rocket engine. By passing liquid hydrogen through the reactor core, the propellant rapidly expands as it quickly evaporates from its cryogenic to gaseous forms. The high pressure of the expanding hydrogen gas is then directed and amplified by the rocket engine’s bell, providing high efficiency, low thrust propulsion. 

First theorised in 1947, a NTP rocket engine has been an elusive and complex goal for rocket scientists. The first tests of a NTP rocket engine was the NERVA-NRX engine, developed by NASA in 1960. Tested in the Nevada desert, the engine performed numerous tests despite its complexity and danger. The NERVA engine continued to be refined and improved until 1973, when the program was canceled.

In Depth: NERVA vs DRACO

DRACO engine on X-NTRV Demonstrator

NASA and DARPA’s Collaborative NTP engine is being developed under DARPAs Demonstration Rocket for Agile Cislunar Operations (DRACO) NTP development program. This program has had major contributors working on an NTP engine since April of 2021, with organisations such as Blue Origin, General Dynamics, and Lockheed Martin all participating in early design phases. NASA has also had independent analysis of a NTP engine, working closely with the Department of Energy. While little is known about the DRACO engine, it will likely share a stark resemblance to the 1960s NERVA engine. 

One major difference between the two engines will be the test campaign that each engine is demonstrated under. The NERVA engine was tested in the Nevada desert, and subjected the area to high levels of radiation during its tests. DRACO will avoid this constraint by being tested fully in orbit, with demonstrators being flown up to a high orbit, between 700 and 2,000km in altitude. For reference, the international space station orbits at only 410km over the surface of the earth. This precaution ensures that in case of a critical failure, all radioactive elements will pose no threat to earth or other astronauts.

The DRACO engine will be tested on the X-NTRV demonstrator vehicle, which will provide all necessary avionics and secondary control systems to enable a full and rigorous test of the DRACO engine.

The X-NTRV demonstrator vehicle will be launched aboard a commercial rocket, however which rocket is currently unknown.

“NASA will work with our long-term partner, DARPA, to develop and demonstrate advanced nuclear thermal propulsion technology 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,” said NASA Administrator Bill Nelson. “Congratulations to both NASA and DARPA on this exciting investment, as we ignite the future, together.”

What This Means

Proposed Mars Crew Vehicle using NTP engines

NASA Administrator Bill Nelson announced that the current date for the test flight for the X-NTRV demonstrator would take place in 2027, and would be ready to pursue flying a crewed mission to Mars by 2030. Despite the ambitious timeline, the DRACO engine and X-NTRV vehicle will need to be tested extensively to ensure the engine is able to operate nominally. The engine would need to undergo many ignitions and hours of testing to ensure the safety of all crew onboard future missions.

However, the possible future with an operational NTP engine would allow an unprecedented access to interplanetary space for robotic and crewed missions. Access to our neighboring and outlying planets could be accessed at an incredible pace and could begin the process of a human landing on Mars. 

“Expanding our partnership to nuclear propulsion will help drive forward NASA's goal to send humans to Mars.” said NASA Deputy Administrator Pam Melroy in a statement to media.