Jet aircraft on Mars
Jet using magnesium powder
There is a report of a jet engine being developed for use on Mars which would burn magnesium powder. The Wickman Spacecraft & Propulsion Co. tried different ways of fluidizing the magnesium powder. Using nitrogen gas to blow the magnesium powder seemed best but their turbine clogged up with carbon stripped from the carbon dioxide atmosphere by the burning magnesium. It seems likely that hydrogen gas would work better to fluidize the magnesium. Equations of the chemical reactions that might occur in such a jet engine are:
2Mg + 2H2 + CO2 ==> 2MgO + CH4
2Mg + 2H2 + 2CO2 ==> 2MgO + 2CH2O
The products of formaldehyde and methane would not cause carbon build-up, but putting magnesium oxide powder through a turbine seems incompatible with long engine life. The whole problem of turbine wear and fouling could be obviated by using a ramjet engine such as was used on the CIM-10 Bomarc Surface-to-air missile which flew at Mach 2.6 at 60,000 feet (18 km). A ramjet would need a rocket stage to get it to the speed at which the ramjet can start. Then the aircraft would need to switch to rocket power again to land or land unpowered. Another problem would be the thinness of the Martian atmosphere. The highest altitude air-breathing jet engine on Earth was the SR-71 reconnaissance aircraft which flew at up to 26 kilometers altitude. The pressure of the Martian atmosphere at the surface is about equal to the pressure at 40 kilometers altitude on Earth, six times lower pressure than at the service ceiling of the SR-71.
So there is a possibility of an atmosphere-breathing ramjet-powered aircraft on Mars, but there are problems that might prevent it.
As the propellant must be refined using energy taken from solar energy of nuclear reactors, it can be said that all propulsion systems on Mars are basically nuclear or solar.
The propellant producing reactions used on Mars, probably electrolysis of water, possibly the Sabatier reaction, produce large amounts of oxygen. It seems more practical to simply recombine the oxygen and hydrogen, or oxygen and methane, bach into their source material of water and CO2 than to use the Martian atmosphere as a less than perfectly efficient reaction mass. Carrying the oxygen is a mass penalty, but hardly worse than carrying large amounts of magnesium. Nitrogen would probably be in demand on Mars as a necessary element for food production and atmospheric composition.