The solar system is a really big place, and it takes forever to travel from world to world with traditional chemical rockets. But one technique developed back in the 1960s might provide a way to shorten our travel times dramatically: nuclear rockets.
Of course, launching a rocket powered by radioactive material has its own risks, as well. Should we attempt it?
Let’s say that you wanted to visit Mars using a chemical rocket. You would blast off from Earth and go into low Earth orbit. Then, at the right moment, you’d fire your rocket, raising your orbit from the sun. The new elliptical trajectory you’re following intersects with Mars after eight months of flight.
This is known as Hohmann transfer, and it’s the most efficient way we know how to travel in space using the least amount of propellant and the largest amount of payload. The problem of course, is the time it takes. Throughout the journey, astronauts will be consuming food, water, air, and be exposed to the long-term radiation of deep space. Then a return mission doubles the need for resources and doubles the radiation load.
We need to go faster.
It turns out NASA has been thinking about what comes after chemical rockets for almost 50 years: Nuclear thermal rockets. They definitely speed up the journey, but they’re not without their own risks, which is why you haven’t seen them. But maybe their time is here.