Special care is needed in the chemical formulation and engine design to prevent detonating the stored fuel.
Weight, energy density, cost, toxicity, risk of explosions, and other problems make it important for engineers to design rockets with appropriate propellants.
The promise of high performance, greater range and lighter feed systems drove experimentation with blends of nitrous oxide and ammonia, which resulted in numerous explosions and demolished motors.
[2] The complexities involved in building propulsion systems that can safely handle nitrous oxide fuel blend monopropellants have been a deterrent to serious development.
Subsequent development of nitrous oxide fuel blends picked up again in the 2000s, and in 2011 an in-space flight test mission was planned.
The "ISPS NOFBX Green Propellant Demonstration" will utilize a deep-throttling 100 pounds-force (440 N)-thrust-class engine burning NOFBX rocket engine that will be mounted to the outside the European Columbus module on the ISS, and had been expected to remain on-orbit for approximately one year while undergoing a "series of in-space performance tests.
NOFBX had previously been used to fuel a reciprocating engine to power high-altitude, long-endurance drone aircraft under a DARPA contract.