Corrections on Martian Articles

My latest articles were mostly about establishing a Martian base. I had proposed that the initial mission to Mars (excluding rover-based preliminary surveillance missions) should be to deploy a Martian Shuttle rocket and its base. Given the scarcity of ISRU resources, missions to Mars would be mostly one-way. In such cases, the Martian Shuttle has minimal use. The shuttle becomes important only for two-way missions and provides an emergency escape vehicle for humans to depart from the planet.

During the calculations for the launch pad, I made a calculation error (thanks to Gemini AI) and underestimated the mass of the power plant to be deployed on Mars. Unfortunately, nuclear power—the only option for high-power electrical supply—is a heavy solution for outputs ranging from 100+ kW to 1 MW. Due to the critical mass requirements of a nuclear fission reactor, the power density of a plant improves considerably as power output increases. This mass penalty becomes more pronounced if we want two smaller-capacity reactors instead of one for redundancy; the mass penalty is almost 50%. So, two 300 kW plants are 50% heavier and even bulkier than a single 600 kW plant. However, scaling up the plant hits a wall due to limited cooling abilities on Mars, meaning there is a sweet spot for such reactors.

Another nuclear option is using Strontium-90 as a hot reservoir and the ice of Mars as the cold reservoir, generating electricity using solid-state technologies. Some technologies can even reach 13% efficiency under high temperature-difference modes. The downside is that they are almost twice as heavy as fission reactors of the same electrical output, and this mass gap widens as power output increases. However, their main advantage is they scale very well. Is that doubling the capacity increases their mass and volume twice and sometimes even less than that. For my future idea propositions, I will mostly rely on these technologies.

I do not believe we will have MW-class power plants on Mars anytime soon. Most power sources will be under 100 kW of electricity. If we want to produce ISRU propellant, the power requirement must be at least several hundred kW. Power demand scales directly with the payload capacity of the Martian shuttle. I had initially proposed a 5-ton payload limit, but after evaluating the power generation constraints, I concluded that 1.5 tons is the sweet spot. This reduces power demand, though not below 100 kW.

Another correction I need to make concerns Methalox vs. Hydrolox. Even though I am not a fan of Methalox over Hydrolox, I admit that a Methalox rocket can be considerably easier to refuel on Mars. The high boil-off penalty and larger dry mass of a Hydrolox rocket require double the energy capacity to ISRU-refuel the shuttle. Given the complexity of deploying power plants on Mars, a 2x difference in energy demand is a showstopper in most scenarios.

Finally, the core of my proposal remains: humanity should establish its base on Mars where permanent ice is available, rather than in the equatorial regions.

In my next articles, I will propose a Mars rover and Mars cargo rockets.