Agreed. It was an amazing success story. It worked far better than the Rats could allow to be heard. They had a DOD renegade leftist schill "strategic analyst" (who in fact contributed nothing himself to the development of the system) pose as an expert to smear the system's performance and justification back in '69, and the Senate kept calling him back to further defame the Safeguard System. The Sprint had gotten so accurate that it was colliding with incoming RVs. So they detuned the MSR radar a bit so that it wouldn't be as likely to collide. Kind of silly when you think about. Even if its own W-66 1.kt warhead didn't go off because of evisceration in an impact event, ...it would similarly have killed the incoming RV...and gotten the job done.
Kind of a precursor to our modern approach of hit-to-kill.
The cone-shaped Sprint missile was powered by a two-stage solid-propellant rocket motor. The motor ignited after the missile had been ejected from its silo by gas pressure, and accelerated the Sprint with more than 100 g. Within seconds, the missile reached a speed of Mach 10+, and the extreme thermodynamic heating demanded sophisticated ablative shielding (the nose was already glowing red-hot less than a second after launch). The Sprint was guided to the target by radio-commands from the ground control system, which used high-speed phased-array MSRs to track the incoming ICBM reentry vehicles. The command uplink had to be powerful enough to work through the exhaust plume and the plasma sheathe around the missile body. Sprint's first stage used fluid-injection jet vanes for control, and the second stage had four small moving fins. The missile was armed with a 1 kT W-66 enhanced radiation thermonuclear warhead, which was detonated by ground command. It destroyed the target's warhead not only with the nuclear blast, but mainly with the very high neutron flux. The whole flight time for an intercept was expected to be not more than 15 seconds.
.
The Soviets clearly admired Sprint, as I believe there are just too many close similarities in the design of their SH-08 Gazelle system, which they keep on station and active:
