The team is currently investigating nitrocellulose as an alternative pyrotechnic mechanism to black powder.

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Potential Advantages

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 2C6H7N3O11+92O22C_6H_7N_3O_11 + \frac{9}{2}O_2 \longrightarrow 12CO_2 12CO2+3N2+7H2O 3N_2 + 7H_2O

While some high energy species are also possible, these are in low concentrations and are all gaseous. This contrasts with Black Powder which produces multiple sulfurous compounds. This causes increased maintenance for components which come into contact with the combustion products. These also smell horrible.

Nitrocellulose is a single base propellant, which is a low explosive, and therefore covered under the team's Low Explosives User Permit (LEUP).

Wetted Nitrocellulose is relatively safe to work with, and functions better at low pressures compared to Black Powder. 

Resources:

The Burning Rate Behavior of Pure Nitrocellulose Propellant Samples from the Army Research Laboratory