Mars Sample Retrieval

The distance between Mars and Earth varies between 55 to 401 million km. Mars is closest to Earth every 780 days. If we want to explore Mars further, planning missions every 2 years is not an option. We should be able to launch missions more frequently. In the worst case 400 million km is not that much if we want to explore the solar system further. Saturn's moon Titan is more than a billion km away from Earth.

I propose a four stage rocket for Mars missions. The first two stages would be classical rockets that launch geostationary satellites. The third and the fourth stages will have Nuclear-Thermal-Propulsion (NTP). Unlike the NTP's developed earlier (see image below), I propose a much simpler and reliable design.

NTP I propose uses tiny gun-type fission bombs that are activated by explosives. These bombs are simple in design and do not require complex timing circuitry of plutonium implosion type. The idea is to heat liquid carbon dioxide to generate high pressure gas using nuclear fission. The Nukes are more efficient, reliable, simpler, smaller and lighter in generating heat from fission compared to much complex nuclear reactors.

The mono propellent, solid carbon dioxide (dry ice) will be partially liquified and poured inside the pressure chamber. Then from a magazine, a pill sized Nuke will be dropped inside. After a chemically delayed explosion, the fission reaction will pressurize the carbon dioxide gas. Which will then be exhausted from the aerospike engines to generate thrust. In order to generate continuous thrust, two pressure chambers will be used in succession. Interplanetary missions require engines that can be fired multiple times. My design allows that.

The third stage of the rocket will put the rocket into Earth to Mars trajectory. The fourth stage will slow down the rocket for landing on Mars. After the landing, a robot will gather the samples. In the meanwhile, the rocket's dry ice maker (powered by nuclear batteries) will refuel the dry ice tank from the Martian atmosphere which is mostly carbon dioxide. Partially filled tank can lift the rocket from ground and let it fly over distant terrain to collect more samples before returning to Earth. Once the sample collection ends, the dry ice tank can be fully loaded. Then the rocket can lift off and start it's return journey.