Humans on Mars with Starship
The interview triggered me in thinking about how the logistics would be executed given the upcoming availability of SpaceX's Starship. In the interview, my estimate was that you would at least require 60 Starship launches to get boots on Mars, and return those boots safely to Earth again. I wanted to have a little bit more confidence so I started doing some calculations. Find those calculations in this excel sheet. My final estimate is that we would require 66 Starship (block-3) launches to do the job. This estimate is based on a number of seemingly factual numbers, such as the data on Starship Block-3, that I found on Reddit and that I copied in below.
Some other important numbers are missing, such as the usefull payload mass (including the astronauts) we would want to put on the surface of Mars. But also, the dry mass of Starship block-3. There is a quote that the dry mass of Starship is 100 ton, from a YouTube video hosted by the Everyday Astronaut Tim Dodd. For my calculation, I used a dry mass of 110 ton to account for the longer hull of Starship block-3 compared to its predecessors.
Anyway, I came to the following mission concept and payload mass to drop on the surface of Mars:
First, I thought, before the crewed Starship is landing on the surface of Mars, a test landing needs to take place to learn how to do this and not risk the lives of the Astronauts to this unknown feat. Second purpose to do it like this, would be setting up first base on Mars and have some supplies at hand. So, let's first land a Starship Pathfinder mission that will test out the landing, and if successfull puts some first hardware on the surface of Mars. From fundamental astrodynamics and rocket propulsion, the payload mass that a Starship block-3 could theoretically land on the surface of Mars is 28.100 kg coming from LEO. But to get it from LEO to the Surface of Mars, the Starship needs to be refuelled and this would require 12 Starship launches, that each brings 200 ton of propellant, to fill up the propellant tanks to its maximum capacity of 2300 ton. The payload to land on the surface of Mars should comprise of, for example, an RTG energy reactor, habitat supplies, machines to create methane, water and oxygen from the thin Martian atmosphere, a robotic platform for transportation and a whole bunch of survival supplies for the crew to arrive next. It would also be nice to have an RF beacon deployed, so the crewed Starship knows where to land, say, within a radius of 1 km or so from the Starship pathfinder. When everything works out nicely, it is time to send the 2nd Starship to the surface of Mars.
Now I have assumed that the crewed payload to land with Starship on the surface of Mars will weigh 50 ton, and really, this is a number that needs more research. But yes, the crew will live in this module for 3 years, so it cannot be a small can like Orion or Soyuz. Also, you want to drop this Starship on the surface of Mars including the propellant needed to get back into Low Mars Orbit (LMO) again, because there is no tank farm existing on Mars that will be conditioning and providing the cryogenic propellants. So the mass of this Starship is way too big to launch from LEO to the Mars surface in one go. We will need to refuel it in LMO, and this requires 2 Starship tankers to fly from Earth to Mars, and provide propellant to the crewed Starship. To fuel these 2 Starship tankers, 16 Starship Tanker launches are needed to provide propellant to the 2 LMO bound Starship tankers. So a total of 30 Starship launches are needed to get the 50 ton crewed payload on the Surface of Mars. But then, we want to go back after staying for 2 years on the surface of Mars and I assume we don't want to bring the full 50 ton payload back to LMO, but only use a 10 ton compartment. After launching from the Martian surface with the propellant we still have after 2 years on the surface of Mars (note that I didn't include any leaking or boiling-of of propellants), we will reach LMO with a Starship with empty tanks. Again we need 2 Starship tankers to come over to Mars, to fuel the crewed Starship for its return flight to Earth. These 2 Starship tankers need to be filled-up with 20 Starship tankers that will have to deliver propellants from the Earth surface to the 2 LMO bound Starship tankers. Once the crewed Starship is back in LEO, I assume the crew is back on Earth, and maybe an extra Starship tanker is needed to fuel the crewed Starship for a final descent on Earth's surface
So counting the amount of Starship launches to get humans from the surface of Earth to the surface of Mars, and back is equal to a staggering 66. Of course, Starship is designed to be reusable, so this can really work. What I do conclude though, is that Starship is far from efficient for landing on- and launching from planetary surfaces where it cannot be refuelled. Getting back in a massive rocketship like Starship requires massive propellant transports, and endless in-orbit refuelling. The propellant leaks and boil-offs will happen and even more Starships need to fly to fuel the behemoths.
And the other open question I have is on the 28 ton pathfinder payload and 50 ton crewed payload. Will this be able to keep a crew alive for 2 years, that is required to wait for the return path from Mars to Earth? I am not a Life-support-system-on-Mars specialist so any thought on that is welcome. And if you see any flaws in the calculation, I would be happy to hear about it.
But regardless, I wished the Humans on Mars challenge would become something that could unite planet Earth, and preserve the light of human consciousness, as the now neofascist owner of SpaceX, Elon Musk, once proclaimed in his more liberal years.
