Mars Rocket Lower Stages

Designing a warm gas propulsion rocket engine simplifies the engine and the propellant tank design. Carbon dioxide liquifies above 5.2 bar at −56.6 °C. Increasing the pressure would decrease the temperature. A propellant tank made of HDPE would easily satisfy these needs. HDPE is very cheap compared to traditional metals used on space rockets. It is also much lighter. It can easily be manufactured in large dimensions and welded continuously compared to the metal counterparts. More importantly the discarded rocket stages would completely decompose into carbon dioxide and water vapor during reentry. Low temperature nature of the design allows unibody plastic pressure chamber and nozzle. They can easily be molded and mass produced. I proposed a common nuclear waste, Strontium-90, to be used as the radioactive heater for the rocket engine. It would be used to heat the carbon dioxide to its critical point, 31 °C, for maximum pressure generation.

Traditional rockets have a very high aspect ratio due to their flight trajectory. I propose a direct ascent trajectory, which takes the rocket out of the atmosphere at relatively low speeds. This allows low aspect ratio designs with much larger base. This design reduces the thrust requirement for the first stage recovery. Much lower center of gravity also helps the stability of the rocket. An interesting bonus for the design is that, during reentry, air entering the combustion chamber of the unused engines would be heated by the radioactive heater and pushed back which would contribute to slowing of the rocket without any propellant consumption.

The solid boosters strapped to the first stage of the rocket would burn out very fast and drop back to the launch site from a relatively low altitude which can be slowed down by parachutes. Therefore, some of these boosters may be refurbished together with the first stage of the rocket. Unfortunately, upper stages of the rocket would not be recoverable. That’s the reason they would be made of plastic.

This rocket architecture allows highly scalable rocket designs with much lower build cost. It can be easily tested in smaller sizes and gradually expanded.

Liquid carbon dioxide for the rocket would be supplied from the thermal power stations which is a waste of those plants. The radioactive Strontium would be supplied from the nuclear power plants which is a waste of those plants. Strontium has a half-life of 29 years and emits beta particles. Therefore, some of it being dispersed to the atmosphere from the upper stages wouldn’t exhibit a major environmental hazard. As a result, this rocket would be one of the greenest of the rockets in operation.