Bring stuff back from Mars, starting with carbon

11/5/24:

Looks like there's at least one error in my spreadsheet. Well, I didn't think it was 100% down the line perfect. It's not my profession after all.

The main idea stands, though. It really would pay to take stuff off Mars since you have to return the Starships anyway. Just ditching them on Mars seems like a big waste, and ultimately you will increase the number of launches needed to get your cargo and crew in place on Mars.

11/4/24:

Some calculations from a spreadsheet. Not very convenient these days on Google platforms because they are so nosy.

The point will become clear from this excerpt ( hopefully if it's readable enough).

Starship/Heavy Version 3 (originally assumed 110 tons, increased here to 200 tons)

Left side-----------------------------------right side

comparsion to LEO and from refilled Starship in space

90 ton payload or 200 ton empty weight Assume dry mass for calculating delta v for right side

wet mass ton______2300__________________wet mass ton_______________2300

dry mass ton______200 __________________dry mass ton_______________800

isp_______________380 __________________isp secs__________________380

grav const m/s^2__9.81__________________grav const m/s^2___________9.81

delta v m/s____9104__________________delta v m/s________________3936

Note that the Starship Version 3 can nearly get to orbit by itself! However, it would be an empty vessel. Not very useful, eh?

However, if you refill it, it can propel itself to another destination. Let's say you are on Mars, and you want to come back to Earth. It takes about 3.8 km/sec to get to Mars orbit from its surface. As is seen above, you can lift 800 tons to Mars orbit from the surface. A lot more than from Earth.

What this shows is that you can put more mass onboard on the surface of Mars, and get it to orbit as compared to doing it on Earth.

Plus you don't need the booster.

It therefore makes sense to send something back from Mars, which means cargo deliveries from Mars is desirable.

What could that cargo be? One thing could be pure carbon for delivery to the Moon. The Moon may not have much carbon, and you can make useful things out of carbon. One useful thing would be methane for rocket propulsion.

If you can make methane on the Moon, you can use the weight savings for more cargo delivered to the Moon. You can also deliver methane to lunar orbit, and beyond.

That's because you can lift even more cargo from the surface of the Moon. Even more still from a LaGrange point. What use would it be at the LaGrange point? You could refill there and store the methane for flights to other destinations.