Nitrous oxide fuel blend

Nitrous Oxide Fuel Blend propellants are a class of liquid rocket propellants. The fuel and oxidizer are blended and stored, and are sometimes referred to as 'mixed monopropellants'. Upon use, the propellant is heated or passed over a catalyst bed and the Nitrous oxide decompose into oxygen-rich gasses. Combustion then ensues. Special care is needed in the chemical formulation and engine design to prevent detonating the stored fuel.

NOFBX is a recent example, developed by Firestar Technologies LLC.^[1]

Overview

Nitrous oxide decomposes into hot oxygen-rich air, and requires no separate supply of oxidizer such as the liquid oxygen used in many high performance rocket engines today.^[2] Consequently, it can be used as a monopropellant by itself. For added performance nitrous oxide may also be blended with a range of different fuels and emulsifiers. Such a blend of an oxidizer and a fuel is called a mixed monopropellant.^{[citation needed]} It combines the simplified plumbing of a monopropellant with the performance of a bipropellant.

History

German rocket scientists were experimenting with nitrous oxide fuel blends as early as 1937. Nitrous oxide fuel blends testing continued throughout World War II. 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.^{[3][Full citation needed]} Until recently (~2003), the complexities involved in building propulsion systems that can safely handle nitrous oxide fuel blend monopropellants have been a deterrent to serious development since the end of WWII.^{[citation needed]}

As of August 2011^[update], Innovative Space Propulsion Systems plans to test the NOFBX mono-propellant on the International Space Station in late 2012.^[1] NASA formally approved the mission to the ISS on a 2013 launch slot in May 2012.^[4]

NOFBX

NOFBX is the trademarked name for a proprietary nitrous oxide/fuel/emulsifer blended mono-propellant developed by Firestar Technologies LLC.^[5] NOFBX has a higher ISP and is less toxic than other monopropellants currently used in space applicatons, such as hydrazine. Flight testing of NOFBX engines is planned on the ISS in 2012.^{[6][Full citation needed]}

NOFBX has been used to fuel a reciprocating engine to power high-altitude, long-endurance drone aircraft under a DARPA contract.^[2]

"NOFBX is being promoted as a “game changing” technology with the following characteristics:^[1]

• constituents are widely available from chemical suppliers, inexpensive and safe to handle.
• can be transported and handled without undue precautions or hazards.
• effluents are non-toxic and produces no accumulated deposits or contamination.
• propulsion system has high Isp (320-340 s) – similar to the most common bi-propellant.
• has far better lift capability than the current workhorse monopropellant, hydrazine.
• is tolerant to a wide thermal range; storable at room temperature on the ground and is Space-storable.
• [is projected to] lower cost compared to existing propulsion systems of comparable performance.
• is monopropellant, which significantly reduces the need for auxiliary hardware, saving cost, volume, and mass for launch systems.
• utilizes cool running thrusters that dramatically reduce thermal design challenges.
• burns in liquid, gas, and two-phase flow.
• does not have the materials compatibility constraints of traditional hypergolic systems."

The patent claims a mixture of nitrous oxide (oxidizer) with ethane, ethene or ethyne as the fuel; as an example, the mixed gases are condensed into a liquid at –70 °C.^[7]

Safety Concerns

Recent work on the decomposition of nitrous oxide has raised concerns about the safety risks of mixing hydrocarbons with nitrous oxide. By adding hydrocarbons, the barrier to an explosive decomposition event is lowered significantly.^[8]

References

Sutton, George P.; Oscar Biblarz (2001). Rocket Propulsion Elements, Seventh Edition. John Wiley & Sons. pp. 6. ISBN 0-471-32642-9. 

External links

• NOFBX patent application

Further reading

G.S. Mungas, Regeneratively-Cooled, Vortex-Jacket, Fluids and Heat Transfer Model for Rocket Combustion Chambers, Joint Army, Navy, NASA, Air Force (JANNAF) Interagency Propulsion Conference, LPS-IIP-3, CPIA/JHU, Colombia, MD (May 2010)

G.S. Mungas, D.J. Fisher, J.A. Smith, K.W. Doyle, G.H. Peters, A.P. London, L. Droppers, J. Fryer, S. Coley, T. Delange, NOFBX COLT Engine Development and Testing, Joint Army, Navy, NASA, Air Force (JANNAF) Interagency Propulsion Conference, SPS-IIE-3, CPIA/JHU, Colombia, MD (May 2010)

G.S. Mungas, D.J. Fisher, C.B. Mungas, B. Carryer, NOFB Monopropellants – Background, Characterization, and Testing. Joint Army, Navy, NASA, Air Force Interagency Propulsion Conference (JANNAF), SPS-I-11, CPIA/JHU, Colombia, MD (Dec 2008)