The concept proposed is that of an innovative turbopump for a staged combustion bi-propellant rocket engine using monopropellant to drive the turbine. The turbopump has a unique feature in that it has an electric generator used to generate electricity and power an external fuel pump.
By using a monopropellant decomposed over a catalyst pack only one fluid can be used to drive one or more turbines. Typically, a turbopump combusts a fuel and an oxidizer in a gas generator to generate the gases to drive the turbine. This requires two sets of feed lines (one for fuel and one for oxidizer) and careful mixture ratio control so that the two combust at a ratio that does not yield such a high temperature that may destroy the turbine. If the mixture ratio is too close to the stoichiometric ratio it will be hot enough to damage the turbine. If it is too far away from the stoichiometric ratio it may not generate enough of the required gases to drive the turbine or even cease combustion (flame out). This problem does not exist with most monopropellants as their maximum decomposition temperature is about half that of modern turbojet engines. Thus, no exotic materials need to be used for the turbine.
The electric generator generates electricity to power an external fuel pump. This allows the pump for one propellant to be placed anywhere on the rocket engine that is desired and does not necessitate mounting it onto the turbopump itself. this greatly simplifies the plumbing of a rocket engine. It also allows the oxidizer and fuel pump to have different speeds so that the engine can change its mixture ratio in flight.
This turbopump is designed to be used with a rocket engine burning propellant combinations where one of the propellants is a monopropellant. This allows for a relatively simple yet fairly high performing rocket engine. In addition, it can easily change its mixture ratio in flight for optimum propellant utilization and little waste.
A rocket engine using a Turbo-Electric Turbopump would be of significant interest to NASA since it is essentially a staged combustion cycle engine with a lot less headache. It uses non-toxic storable propellants and is ideal for small launch vehicle intended to launch on short notice. It can also be used as spacecraft propulsion where higher chamber pressures than typically used with pressure-fed systems are desired, such as on heavy lunar and Mars landers. Such an engine is highly throttleable and very scalable. No ignition system is required.
A rocket engine using a Turbo-Electric Turbopump offers advantages to commercial space companies since it is a high thrust, staged combustion engine that is drastically simpler (and thus less expensive) than a typical staged-combustion engine. It could be used for both vertical and horizontally launched rocket vehicles as well as spacecraft, especially lunar landers for Moon missions.