Without fuel, no return. And for the missions inhabited towards Mars, this risk is very real. Fortunately, NASA may have just resolved one of the greatest technical obstacles to the interplanetary trip: the conservation of cryogenic fuel over long durations. A revolutionary cooling system could allow astronauts to leave … and return safely.
The invisible but fatal problem: evaporation of ergols
For over 70 years, sending humans to Mars has been a dream brought by scientists and engineers. Today, this ambition is part of a more concrete phase. Spatial agencies and private companies redouble their efforts to make this scenario credible. But if progress is notable in navigation, survival in hostile or propulsion, a persistent technical problem could compromise everything: how to keep, for months, the fuels necessary for the return trip?
To propel a spacecraft towards Mars then bring it back, it takes a massive amount of fuel. This fuel, often composed of substances such as hydrogen, oxygen or liquid methane, is stored in cryogenic form, at extreme temperatures up to -253 ° C. But even in space, these liquids bubble slowly in their tanks, generating a pressure which must be released to avoid the explosion. Result: a slow but continuous evaporation.
This phenomenon is acceptable for short orbital or robotic missions, but becomes a logistics nightmare for a round trip to Mars. The figures speak for themselves: with a tank of 38 tonnes of liquid hydrogen, a typical mission would lose up to 16 tonnes per year by passive evaporation. What completely compromise the return trip, and put the crew in danger.
Active cooling to stop the energy hemorrhage
Faced with this dead end, engineers from the NASA Marshall space center in Huntsville (Alabama) have developed an experimental cryogenic fluid management technology. Their solution? A spatial super-spatial repair called “two-story cooling”, capable of maintaining cryogenic fuels at stable temperature for months, or even years.
The system is based on two cooling loops integrated into thick insulation and a thermal shield. The first loop, at the heart of the device, directly surrounds the tank with tubes filled with liquid helium at -253 ° C, which ensure the immediate cooling of fuel and its wall. The second loop, at a slightly higher temperature (-183 ° C), acts as a thermal barrier, intercepting any residual heat before it reaches the interior.
Three months of promising tests
This technology was tested for three months under simulated ground conditions. The results are very encouraging: the system has been able to maintain stable cryogenic conditions without any measurable loss of fuel. The device therefore opens the way to longer missions, without the need to overload the excess fuel vessels intended to compensate for the losses. Better yet, it offers a solution for long-term storage of ergols on the Martian surface itself.
Cryogenic tank installed in an empty room. Credits: NASA/Kathy Henkel
A decisive advance for spatial autonomy
This innovation is much more than just technical progress. It changes the situation for future trips in deep space. By removing losses related to evaporation, it drastically reduces logistical, costs and risks. The vessels can be designed more effectively, the missions planned with more flexibility, and the crews focus on their mission, without fear of lacking fuel at the decisive moment.
According to Kathy Henkel, head of the Cryogenic project at NASA, ” Two-storey cooling technology is essential to the success of missions to the Moon, Mars, and beyond ». She recalls that ”
These systems are not only used for transport, but also for storage, in transit as on the surface of planets. »
One more step towards Mars… without going back
If Martian rockets and habitats capture the collective imagination, it is often the less spectacular systems, like this super-refrigerator, which make spatial exploration really possible. It is thanks to this type of discreet but fundamental innovation that humanity can one day set foot on Mars … and return to earth.