Gelled/Neat Hypergolic Propellant Ignition and Combustion

Impinging jet apparatus featuring electromechanical actuators and 360° optically accessible chamber (Click to enlarge).

This effort, funded by an Army Research Office (ARO) MURI grant, seeks to understand the propellant properties as well as physical and chemical processes that govern hypergolic ignition. Monomethylhydrazine (MMH) and red fuming nitric acid (RFNA) have been the primary focus of this effort but attention is also being given to high performance less toxic hypergolic propellant combinations.

An unlike doublet impinging jet apparatus is used to characterize the ignition and combustion of both neat and gelled hypergols.

Hypergolic combustion chamber interfaced with IJ apparatus to allow combustion studies at elevated pressures (Click for details).

Motor velocity (red) from three identical injection commands with commanded velocity (blue) (Click to enlarge).

• Highly repeatable electromechanically controlled injection events for characterization of hypergolic ignition events.
  • 60° included angle injection system with 160 ft/s (48.8 m/s) maximum injection velocity.
  • Variable O/F, orifice diameter, injection duration, etc.
• Completely optically accessible chamber for imaging ignition events.
• Small scale combustor for evaluation of characteristic velocity and combustion efficiency.
  • Maximum chamber pressure of 200 psi and 3 second firing duration.
  • Windowed combustion chamber for optical accessibility.
  • Array of nozzle throat inserts for variable target pressures and mass flows.
  • Future plans for laser exhaust probing (PIV) to resolve specific impulse.

Ignition delays for neat and gelled MMH/RFNA measured in the impinging jet apparatus (Click to enlarge).

• Identification of a neat MMH/RFNA ignition threshold in the impinging jet apparatus.
• Understanding of key rheological parameters to achieve mixing and combustion of gelled hypergolic propellants.
• Measurement of ignition delays for gelled MMH/RFNA that are very similar to neat MMH/RFNA.
• Evaluation of combustion efficiency loss due to inert gellant in MMH/RFNA.
• Identification of candidate less toxic hypergolic propellants leading to ongoing studies dedicated to improvement of hypergolic propellant toxicity and performance.

Combustion efficiency of an alternative "green" propellant compared to neat MMH/RFNA
(Click for details).