Ammonium perchlorate composite propellant
In addition, the high-power rocketry community regularly uses APCP in the form of commercially available propellant "reloads", as well as single-use motors.
The resulting cured propellant is fairly elastic (rubbery), which also helps limit fracturing during accumulated damage (such as shipping, installing, cutting) and high acceleration applications such as rocketry.
The composition of APCP can vary significantly depending on the application, intended burn characteristics, and constraints such as nozzle thermal limitations or specific impulse (Isp).
In addition, the chemical composition of the gases changes, varying the effective heat capacity of the gas.
The propellant particle size distribution has a profound impact on APCP rocket motor performance.
However, the surface area increases as the square of the radius, which is roughly proportional to the heat flux into the particle.
The mass flux (kg/s) [and therefore pressure] of combustion gases generated is a function of the instantaneous surface area
(m/s): Several geometric configurations are often used depending on the application and desired thrust curve: While the surface area can be easily tailored by careful geometric design of the propellant, the burn rate is dependent on several subtle factors: In summary, however, most formulations have a burn rate between 1–3 mm/s at STP and 6–12 mm/s at 68 atm.
That is, if surface area were maintained constant during a burn the combustion reaction would not run away to (theoretically) infinite as the pressure would reach an internal equilibrium.
For RMS, the APCP "grains" (cylinders of propellant) are loaded into the reusable motor casing along with a sequence of insulator disks and o-rings and a (graphite or glass-filled phenolic resin) nozzle.
Compacted black powder slugs become prone to fracture in larger applications, which can result in catastrophic failure in rocket vehicles.
APCP's elastic material properties make it less vulnerable to fracture from accidental shock or high-acceleration flights.
Due to these attributes, widespread adoption of APCP and related propellant types in the hobby has significantly enhanced the safety of rocketry.
The hydrochloric acid component of APCP exhaust leads to the condensation of atmospheric moisture in the plume and this enhances the visible signature of the contrail.
The vendor is charged with the responsibility (by the NAR and TRA) to check hobbyists for high-power rocket certification before a sale can be made.
