**2.8 Concluding remarks for monopropellant**

An initial risk reduction program has been performed for the concept of dualcapability propulsion systems. This was done by analysis of data as well as by dedicated tests. The program included proof of concept of dual use of all propulsion system parts and components, such as thrusters, valves, diaphragm tanks, pressure transducers, and pipework. The dual use of the propulsion systems' key components, the thrusters, is beyond any previous work. Both material compatibility and actual operation have been justified for both hydrazine and RHP, in view of an eventual system end-to-end proof by firing testing in space simulation environment.

The concept of dual-capability systems may serve as a vehicle toward gradual migration from monopropellant hydrazine propulsion systems to equivalent RHP systems. Hydrazine systems are prevalent in several applications and are still often the systems of choice in space propulsion as well as in other applications. The slow introduction rate of RHP or "green propellants," into space systems due to the conservatism of the space propulsion industry may be expedited thanks to the possibility for gradual conversion by dual capability of conventional hydrazine systems and ADN-based RHP. The presented propulsion system concept may accept last moment decisions on fueling with either hydrazine or with an RHP. This flexibility enables project progress until a very late stage without necessary commitment to either of the propellants, thus allowing a smoother transfer from hydrazine to RHP.
