Novel High Nitrogen Propellant Use in Solid Fuel Micropropulsion

TLDR

These high‑nitrogen fuels were chosen for their easy ignition, good safety, long‑term storage, low combustion temperature, non‑corrosive products, and reasonable cost. The study investigates using BTATz and DAATO3.5 as solid propellants in micro‑thrusters. Safety characteristics (impact, friction, DSC, electrostatic sensitivity) and burn‑rate measurements were compared to conventional micro‑propellants, and quartz micro‑thruster tests were performed to assess performance. BTATz and DAATO3.5 exhibit very high burn rates, with DAATO3.5 having the highest known stable organic burn rate and a pressure exponent of 0.28; chamber pressures reached 18 atm, peak thrust ~0.1 N, and specific impulses of 218 s (BTATz) and 228 s (DAATO3.5), a 14 % efficiency relative to theoretical that is acceptable for micro‑propulsion.

Abstract

The use of two novel materials, 3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-s-tetrazine (BTATz) and mixed N-oxides of 3,3'-azo-bis(6-amino-1,2,4,5-tetrazine) (DAATO3.5, where the 3.5 indicates the average oxide content), as solid fuels in micropropulsion systems is investigated. These materials were selected due to their ease of ignition, relatively good safety characteristics, long-term storage capability, low combustion temperature, noncorrosive combustion products, and reasonable projected material cost. Material safety data including impact, friction, differential scanning calorimetry, and electrostatic sensitivity are reported and compared to the previously implemented micropropulsion fuels, lead styphnate, glycidyl azide polymer (GAP) and 3,6-diamino-1,2,4,5-tetrazine-1,4-dioxide. Burn rate data are also reported for both materials. Whereas BTATz and DAATO3.5 have very high burn rates, DAATO3.5 is believed to have the highest burn rate of any known stable organic solid. Additionally, DAATO3.5 has a very desirable pressure exponent of 0.28. Test stand results using a quartz microthruster are reported for these materials. Estimated chamber pressures reached 18 atm with peak thrust levels around 0.1 N. Measured specific impulses of approximately 14% of the theoretical specific impulse (218 s for BTATz and 228 s for DAATO3.5) were obtained. This level of inefficiency is believed to be acceptable for micropropulsion systems and is comparable to other, independent work.