Technology

I wondered what the actual power difference or advantage is, and found answers in the second link:

Even in favorable scenarios where Earth and Mars line up every 26 months, a humans-to-Mars mission still requires 1,000 to 4,000 metric tons of propellant.

If that’s difficult to visualize, consider this. When upgraded to its Block 1B configuration, NASA’s Space Launch System rocket will have a carrying capacity of 105 tons to low-Earth orbit. NASA expects to launch this rocket once a year, and its cost will likely be around $2 billion for flight. So to get enough fuel into orbit for a Mars mission would require at least 10 launches of the SLS rocket, or about a decade and $20 billion. Just for the fuel.

The bottom line: if we’re going to Mars, we probably need to think about other ways of doing it.

Nuclear propulsion requires significantly less fuel than chemical propulsion, often less than 500 metric tons. That would be helpful for a Mars mission that would include several advance missions to pre-stage cargo on the red planet. Nuclear propulsion's fuel consumption is also more consistent with the launch opportunities afforded by the orbits of Earth and Mars. During some conjunctions, which occur about every 26 months, the propellant required to complete a Mars mission with chemical propellants is so high that it simply is not feasible.

And what of the Starship concept that SpaceX is building to send humans to Mars? The project seeks to address the problem of needing a lot of chemical propellant by developing a low-cost, reusable launch system. SpaceX engineers know it will take a lot of fuel to reach Mars, but they believe the problem is solvable if Starship can be built to fly often and for relatively little money. The basic concept is to launch a Starship to orbit with empty tanks and transfer fuel launched by other Starships in low-Earth orbit before a single vehicle flies to Mars.

Braun said SpaceX is developing a plan to send humans to Mars with different assumptions than NASA. "I think there's a fundamental difference in the assumptions that NASA tends to make for what kind of infrastructure is needed at Mars," he said.

That's not to say Starship cannot work. However, it does illustrate the challenge of mounting a mission to Mars with chemical-only propulsion. To use traditional propulsion, one needs to push the boundaries of reuse and heavy lift rockets to extreme limits—which is precisely what SpaceX is trying to do with its fully reusable launch system.