Suppose you were to take on the challenge of defending against ballistic missiles. The big ones, mind–intercontinental ones with thermonuclear warheads. You might conclude that you’d need a layered defense, with different missiles to attack the ICBM in flight. Of course, the trickiest interception problem is the goaltender’s, i.e. the last line of defense. How to intercept a missile when your shot is the last one is a really tricky problem, and one such solution is the topic of today’s resurrected weapon post.
Behold, the Sprint antiballistic missile system!
It was a relatively short ranged system, with a claimed operational radius of 40 km, and a flight ceiling of 30 km. But that’s to be expected. It’s supposed to be the last attempt to stop an incoming warhead. Of course, since other missiles were to have had the first go, the incoming warhead was beginning its decent. In order to stop it, Sprint had to be mind-bogglingly fast.
The Sprint missile was a two-stage affair, which accelerated at 100 Gs. This sustained acceleration would turn any human passengers into paste. Good thing it doesn’t have any. Sprint would go from zero to Mach 10, or 3.4 kilometers per second, in under five seconds. Given this tremendous velocity, it would intercept a target it’s maximum interception altitude of 30 kilometers in less than fifteen seconds.
In order to make this speed work, Sprint had a number of interesting features for the time. It was cone shaped, and was sheathed in an ablative coating to withstand the extreme1 temperatures generated by the missile. The silo doors were blown off by explosive charges, and the missile was kicked from its silo by a second set of explosive charges, pushing a large piston. Once clear of the silo, the first stage burned for only 1.2 seconds before dropping away.
Sprint had a novel and rather dirty way of defeating incoming warheads. Sprint’s payload was a W66 enhanced-neutron warhead. This low-yield warhead was designed to spray high-energy neutrons, to disable the electronic systems of the incoming warhead, or to cause the warhead to fizzle2 prematurely. Of course, this neutron blast, and the resulting possible fizzle, is not exactly clean, so Sprint was intended for use as a terminal defense system for ICBM silos.
Guidance of Sprint was also a difficult challenge. To keep fragile electronics out of the missile, a large and powerful radar set was emplaced on the ground, and a radio command guidance system was used. At the speeds Sprint traveled, it would be enveloped in a plasma sheath, which would make radio communication difficult. To get around this, the radio beam was made very narrow and very powerful.
So what do we think? As is, it’s kind of specialized. But there’s a market for ABM systems these days, and it bears some further testing with a more conventional fragmentation warhead, and possibly more capacity for maneuvering at speed.
Verdict: Project approved for further research funding by Borgundy Air Force Procurement Board
1.) About 3,400 degrees Celsius or so. Very hot. That speed comes at a price.
2.) A technical term in this case for a subcritical nuclear reaction.