the all-weather interceptor is the coolest type of aircraft. it's only used in emergencies and its only role is to be as fast and as dangerous as possible in a short timespan
the Sprint is the missile version of this. Low altitude terminal defense. An absolutely terrifying concept, when you think about it. It's the thing that's automatically launched when some of them made it through, past the Spartans. Your only hope is to wait until they're close enough that all the decoys and chaff have burned away.
A still image: The reentry vehicle is thirty-seven miles up. Your MSR has radar lock. The warheads are shining brightly, illuminated by millions of watts of microwave power. They are moving at 24 times the speed of sound. You have 7.4 seconds.
The missile is launched automatically. Hinges are too slow; the doors are blasted off the silo with explosives and the missile is driven out with a piston as it ignites. 100 g, 650,000 pounds of boost from the first stage's 1.2 seconds of firing. The second stage provides constant thrust until intercept. It reaches Mach ten in five seconds. "As fast as possible, as fast as possible." It is accelerating faster than anything in the world. It is glowing, not from the heat of reentry, but from the heat of acceleration. Guidance instructions are blasted through the plasma sheath with the most powerful radio transmitters available.
A streak of raw power, itself nuclear-armed. Intercept point. 300 feet from target, two miles up in the worst case. The W66 warhead was one of the first enhanced radiation weapons: a thermonuclear weapon with a radiation case modified to let the fusion neutrons escape, instead of harnessing them to instantly cause fission in a uranium shell, (converting them to explosive power, not required in this application). The blast is small, comparatively. The neutron flux is enormous: the incoming weapon is sabotaged, set off wrong by radiation it could not hope to withstand. A midair fizzle, two kilotons destroying one megaton.
The Sprint would not be enough. A nation can always field more missiles to attack a given target than another can field antiballistic missiles to defend that target. The first intended application was Nike-X. They intended to base Sprints in the suburbs to defend major cities. The Sprint would not be enough. This is nuclear war. There is no defense and it cannot be won. The only hope is prevention.
