Airbag technology, originally developed in the automotive safety program, is adapted to submunition dispensing system. For the mathematical modeling of the gas generator, a lumped parameter approach is adapted, treating heat transfer and pressure drop in the filter section explicitly. Inflation of airbag is simulated by assuming that it keeps cylindrical shape during inflation. Some experiments on the filter layer are carried out to obtain the Ergun constants and heat tranfer coefficient. To verify the validity of the model, comparison is made with real tank test data. Result of numerical simulation under the specified design parameters is given.