Metal-organic frameworks as hypergolic additives for hybrid rockets

Area of Science:

• Aerospace Engineering
• Materials Science
• Combustion Science

Background:

• Hybrid rocket propulsion offers cost reduction through simplified engine design.
• Hypergolic propellants ignite on contact, eliminating ignition systems and simplifying integration.
• Current hypergolic fuels often rely on toxic hydrazines, necessitating safer alternatives.

Purpose of the Study:

• To demonstrate the use of hypergolic metal-organic frameworks (HMOFs) as additives for hypergolic ignition in paraffin-based hybrid rocket fuels.
• To investigate the ignition delay (ID) of HMOF-paraffin blends with White Fuming Nitric Acid (WFNA).
• To theoretically analyze the performance impact of HMOFs on specific impulse (Isp) and density impulse (ρIsp) in hybrid launcher engines.

Main Methods:

• Experimental measurement of ignition delay for paraffin blends containing varying mass fractions of HMOFs.
• Use of White Fuming Nitric Acid (WFNA) as the oxidizer.
• Theoretical performance analysis of HMOF-containing fuels in a hybrid rocket engine scenario.

Main Results:

• The majority of tested HMOF-paraffin blends exhibited ignition delays under 10 ms, qualifying them as ultrafast hypergolic propellants.
• Theoretical analysis indicated a slight decrease in specific impulse (Isp) and density impulse (ρIsp) with HMOF addition, comparable to Ammonia Borane (AB).
• HMOFs demonstrated significantly higher thermal stability than AB, facilitating safer and simpler manufacturing processes.

Conclusions:

• HMOFs are effective additives for achieving hypergolic ignition in paraffin-based hybrid rocket fuels.
• HMOFs offer a safer, more stable alternative to traditional hypergolic additives, with tunable combustion properties.
• The use of HMOFs presents a promising pathway for developing cost-effective and environmentally friendlier hybrid rocket propulsion systems.