The Aerojet 530NS-35 solid motor was designed to propel the Radioplane
RP-76 target drone. It produced 36-lbf (160N) for about nine minutes,
empowering the target to fly at Mach 0.95 and up to 60,000-ft.
Twin exhaust nozzles extended from the wastebasket-size cylindrical
motor. I have seen the motors at Aerojet in 1959, but wasn't then
curious about the propellant or grain. Now I realize that "NS"
referred to a "nitrate-type" oxidized system, and suspect that
guanidine nitrate was the key ingredient. But how, pray tell, design a
solid grain with nine-minutes burn time?
Perhaps an end-burner encased in a spiral tube, with a burn rate of
millimeters per second?
At 0.1"/sec burn rate, that's a fifty-three inch long end-burning grain. No?
I cannot image an end-burn grain of any geometry that gives a
long-term even thrust, no matter the concept. My experience with
end-burn solid grains is they tend to "cone" into concave burn
surfaces that become progressively larger, in brief periods of time.
What's your notion how they made a 530-sec burn in a wastebasket size motor?
Exhaust nozzles, white, can be seen in the photos here:
https://www.ewarbirds.org/aircraft/aqm38target.shtml
Edward