Rocket boost

OK, here's an interesting one for all the airfile/config experts out there! I'm working on a number of projects that are jets, with an additional rocket booster. From a dynamics point of view, can anybody think how I might go about simulating an additional engine with a limited fuel capacity?
For example, I want to add a RATO effect to the B-47, which would have an additional 18000 lb of thrust, but only for a short duration.
All help GREATLY appreciated ???
For example, I want to add a RATO effect to the B-47, which would have an additional 18000 lb of thrust, but only for a short duration.
All help GREATLY appreciated ???