By signing with Darpa for the development of a nuclear-powered rocket, NASA is looking for a way to facilitate travel to Mars… And the rest of the galaxy? Response of the viability of the project during the first test launch within (at least!) four years.
Nuclear is not only in favor in the production of energy: while the energy tensions of the invasion of Ukraine have revived many civilian programs, now the power of the atom could finally go into the ‘space. The American space agency NASA has indeed announced that it is collaborating with the American military technology agency (Darpa) for the development of a space nuclear rocket via the DRACO project (Demonstration Rocket for Agile Cislunar Operations, or “demonstration rocket for agile operations within the earth-moon zone” in French). A propulsion whose theoretical power has a first goal displayed in NASA’s tweet: to send the first manned mission to the planet Mars.
We’re partnering with @DARPA to demonstrate a nuclear thermal rocket engine in space. This new engine would allow us to do more science and reach destinations faster—key steps for sending the first crewed mission to Mars. https://t.co/xhWJYNbRz2 pic.twitter.com/JUDN6nUGbj
—NASA (@NASA) January 24, 2023
Because if the moon has occupied many minds with the recent success of the Artemis mission – which should lead to a return of man to the moon – the red planet remains at the heart of fantasies. Those of Elon Musk on the one hand, but also those of NASA, which has been working for decades to conquer the red planet. A planet that raises many challenges that the thermal nuclear engine could help to meet.
Time, the enemy of trips to Mars
Before talking about the engine, let’s consider the reason for the development of this engine: time. While the moon is located at a fixed distance of 384,400 km, Mars is on average 225 million km from us – 56 million at perigee, 405 million at apogee (and space launches don’t happen in a straight line! ). Already that the lunar voyages are technical challenges, those towards Mars are another pair of handle. And become even more difficult when one aims to put men on board.
In addition to the landing, which many unmanned missions have paid the price, the difficulty of traveling with men to Mars is linked to the travel time. A time that oscillates around 180-200 days at best. Combined with the time of exploration and return (a journey of about three years!), this duration poses two fundamental problems: the protection of physical health linked to space radiation and the protection of the mental health of humans cut off from their world for such extended periods. Reducing this duration is therefore essential for risk reduction. And this is where the atom comes in.
A more efficient engine than chemical engines
Atomic energy is envisaged by NASA in two forms: an electric nuclear engine and a thermal nuclear engine. It is on this second type of engine that the space agency is collaborating with Darpa. Such an engine works by transferring heat from the nuclear reactor to a liquid propellant. The heat transforms the liquid into gas, which will thus expand to be expelled through a nozzle. Producing thrust. A thrust that turns out, in the case of the nuclear reactor, to be both greater and more efficient (at least three times!) than that of chemical engines.
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A double blow since it makes it possible to lighten the mass of the fuel of the mission, which NASA estimates between 850 and 1250 tons. And it could also (and importantly) reduce the travel time for humans to Mars to just 100 days. Even 45-50 days in the case of a bimodal engine which would combine the thermal nuclear engine and the electric nuclear engine – less powerful, but capable of providing constant long-term thrust.
Propulsion rising from the ashes
Whether the chosen solution is mono or bimodal, the nuclear engine has on paper very significant advantages over chemical propulsion. But it also presents risks that humanity has so far never managed to overcome. Whether for technical or political reasons. On the technical side, it is obviously the fissionable material which poses the first problems. No “nice” civilian concentrations: space requires, the weight is essential in the design of the machines. It is therefore highly enriched military grade materials that are selected. This is also the reason that prompted NASA to join the Darpa project. Who remains the prime contractor and the only one able to provide radioactive material of this quality.
In the past, Americans and Soviets have all worked on nuclear propulsion. The American project Orion (not the capsule that should allow future lunar travel) of the 50s and 60s sought to use the power of explosions (!) to propel a ship into space. A project that ended up being buried following the first partial nuclear test ban treaties in the early 1960s. The engine closest to the one in development is also American. Called Nerva (Nuclear Engine for Rocket Vehicle Applications), this project took over from Orion between 1960 and 1972. This nuclear thermal engine was already expected to provide propulsion to Mars, but the end of the Appolo program marked its death… and we had to wait until early 2023 to see the effective resurrection of this technology.
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If this nuclear propulsion engine becomes a reality, this nuclear “first” in space will only be for high-power propulsion. Because it’s been a while since we send radioisotope thermoelectric generators (RTG) in space. It is these devices – operating on the basis of plutonium (USA, Russia) or americium (Europe) – which have equipped probes such as Cassini or rovers such as Perseverance for decades. And make it possible to provide low intensity propulsion and/or electrical power (which can, through the battery supply, also indirectly provide propulsion).
It only remains to wait four years for the first test flight of DRACO, scheduled for 2027. Hopefully!
Nasa
