Typical solid rocket motor propellants, like those used in the boosters of the Space Shuttle, are composed of particles of ammonium perchlorate (AP) and aluminum (Al) imbedded in a fuel binder. Typical composition of a propellant is 70% by weight AP, 16% by weight Al, and 14% by weight binder.

The typical size of an Al particle is roughtly 18 microns in diameter.

As the surface regresses, the Al particles become free from the solid propellant and are heated. The small Al particles agglomerate with one another until they form larger particles, usually on the order of 100 microns, then lift of f the surface and are injected into the chamber flow.

As the Al particles leave the combustion region the temperature of the gas is hot enough for ignition to take place, causing the Al particles to burn.

The complexity of including aluminum burning in any numerical simulation can be seen by viewing the two movies below.

The first movie consists of PBAN/AP/AL with 84% by weight total solids loading, with 16% by weight Al particles.

The second movie is that of a Tactical Booster #2, HTPB/AP/Al with 87% by weight total solids loading, with 19% by weight Al particles.

The movies are from United Technologies, Pratt & Whitney, Chemical Systems Division. One aspect of Rocfire will be to simulate numerically this complicated picture of separation, agglomeration, and burning of aluminum particles.

T.L. Jackson (webmaster)
E-mail: tlj@csar.uiuc.edu
URL: www.csar.uiuc.edu/~tlj

Site Last Modified: February 1, 2003