Reaction involved in Combustion of Nitrocellulose-Nitroglycerine(NCNG) solid propellant? I'm working on solid propellant based microthrusters and I am using NCNG as the solid propellant. I want to know the reaction taking place and the mass fraction of the products obtained on combustion of NCNG propellant.
Nitrocellulose is complex stuff. It is generally considered to be the fully nitrated version of cellulose, in which every available alcohol functional group is converted to a nitrate:

$$\ce{[C6H10O5]n +3HNO3 -&gt; (C6H7O2(ONO2)3]n +3H2O}$$

In principal it probably contains some small amount of partially and/or non-nitrated units.

If we consider nitrocellulose to be fully nitrated, then the combustion reaction is:

$$\ce{ 2C6H7N3O11 + 9/2O2 -&gt; 12CO2 + 3N2 + 7H2O}$$

For nitroglycerin $(\ce{C3H5N3O9})$:

$$\ce{2C3H5N3O9  -&gt; 6CO2 + 3N2 + 5H2O + 1/2O2}$$

It will depend on the ratio of nitrocellulose to nitroglycerin what the overall $\ce{CO2}:
\ce{N2}:\ce{H2O}$ mole ratio is. I'll leave you to figure out the mass ratios using the molecular masses of the products.