Why Mars and why now?
Mars has long been a goal for space agencies around the world. NASA notably plans to send manned missions to the planet over the next decade.
There are several reasons for the interest in Mars. On the one hand, it is one of the closest planets to Earth. But above all, it could potentially harbor life or have conditions conducive to colonization.
Naturally, a manned trip to Mars involves many challenges. One of the main ones is travel time. With current propulsion technologies, reaching the Red Planet takes several months, which poses problems for astronauts, particularly in terms of health (exposure to cosmic radiation, muscle and bone loss, etc.) and logistics (food , water, oxygen).
It is therefore essential to find faster and more efficient ways to get to Mars. That’s where nuclear thermal propulsion comes in, a developing technology that could reduce these travel times and open up new opportunities for deep space exploration.
Understanding Today’s Rockets: Chemical Propulsion
Traditional rockets, the ones we currently use to send satellites and space missions, operate using chemical propulsion. This system relies on the combustion of a fuel, usually a mixture of propellant (such as hydrogen) and oxygen. These two elements, when mixed and ignited, then generate thrust allowing the rocket to escape Earth’s gravity and then move through space.
One of the main strengths of this system is its simplicity: the chemical reaction is reliable and efficient. However, it also has its limits. For combustion to take place, large quantities of oxygen and fuel must be carried, which makes the rocket heavier and limits its payload capabilities.
Furthermore, although these engines are capable of taking us into space, they cannot achieve very high speeds over long distances. This means that trips like the one to Mars take a long time (around 9 months).
nuclear propulsion rocket
” width=”1203″ height=”871″/>
The nuclear revolution
This is where nuclear thermal propulsion comes in. Unlike chemical propulsion systems, this technology uses nuclear fission to generate energy.
As a reminder, nuclear fission is the process that occurs when an atom (usually uranium 235) is divided into two smaller fragments after absorbing a neutron. This reaction releases a huge amount of energy in the form of heat. In a nuclear thermal propulsion engine, this heat is then used to heat a propellant, such as hydrogen, which is then expelled through a nozzle, creating thrust.
On paper, this process is much more efficient than chemical propulsion. One of the major advantages is that it generates very high thrust, which allows it to accelerate more quickly in space. This means that travel time for long-duration missions, such as those to Mars, could be cut in half, making missions safer and more viable.
Scientists also report a significantly higher “specific impulse” with this technology. Specific impulse is a measure of how efficiently an engine uses fuel to generate thrust. In the case of nuclear thermal propulsion, this impulse would be approximately twice that of chemically propelled rockets. This means that nuclear thermal propulsion would allow fuel to be used much more efficiently, resulting in more rational fuel consumption.
An idea brought up to date
Of course, the idea of nuclear propulsion is not new. As early as the 1950s, the United States began investing in research to develop this technology. Between 1955 and 1973, programs such as those of NASA and General Electric produced and tested around twenty ground-based nuclear thermal propulsion engines. These engines were promising, but they used highly enriched uranium fuel, which posed security and nuclear proliferation concerns.
Today, research into nuclear thermal propulsion has resumed with a vengeance. The DRACO program of NASA and DARPA plans in particular to use a new type of fuel based on low-enriched uranium, safer and more suitable for space use. The program aims to test this technology in space from 2027.
Also note that exploring Mars is only the first step. Nuclear propulsion could make it possible to explore even more distant areas of our solar system, such as the moons of Jupiter or Saturn. It could also be used to build mobile space stations capable of moving in space and carrying out maintenance missions on satellites, or even defending them in the event of a threat.
Nuclear rockets could one day enable faster space travel. Credit: NASA
The challenges to be met
Although this approach promises to revolutionize space travel, it is not without obstacles. Several major challenges must still be overcome before this technology can be used for manned missions to Mars or beyond.
The main technical challenge lies in designing the nuclear reactor capable of operating safely in space. The nuclear thermal propulsion engine will have to operate at extremely high temperatures, much higher than those of traditional terrestrial nuclear reactors, while remaining reliable for long periods in hostile conditions. It will therefore be necessary to ensure that the reactor can maintain constant heat production without overheating, and to effectively manage the engine start and stop cycles.
The materials used to build these engines must also be strong enough to withstand high temperatures without degrading, while remaining light enough not to weigh down the rocket.
Another major issue will be security. Working with nuclear materials indeed presents radiation risks, especially in the event of an accident during launch or in orbit. Strict precautions will therefore have to be taken to avoid radiation leaks into the space environment or on Earth. Furthermore, the use of even slightly enriched uranium raises questions of nuclear proliferation and international regulation. Approval from national and international regulatory bodies will be required to launch these missions.
Finally, the development of this technology will also be expensive. Nuclear reactors and propulsion systems are complex and require massive investments in research and development. The flight tests planned as part of the DRACO program by 2027 are a first step, but many other steps will have to be taken before a manned mission to Mars can be considered.
Source : The Conversation
