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Terminal Defense
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Sprint (Continued)

By operating within the atmosphere, terminal defense using the Sprint was able to target only true threats, since other spurious targets such as ICBM booster fragments, decoys, and chaff would have been destroyed by atmospheric friction during re-entry. The trade off for this advantage was the extremely limited amount of time available for Sprint to do its job.

Its need for ultra fast acceleration made Sprint a remarkable missile. It was launched from its climate controlled silo by being tossed into the air by a gas discharge mechanism at the bottom of the silo after the silo cover had been blown off by an explosive charge. The first stage ignited as it cleared the silo, propelling the missile to hypersonic speed in seconds. Internal components were designed to withstand accelerations of 100g (100 times gravity). The second stage reached velocities that caused atmospheric friction to heat the skin of the missile to the point that it glowed incandescantly; a flame from an acetylene torch would have cooled it.

Terminal defense using the Sprint required "close in" interception. In an attempt to minimize the time between launch and interception, Sprint launchers were dispersed over a wide geographical area. Sprint missile fields were located at the MSR complex as well as at four geographically dispersed remote Sprint launch sites (RSL's) that were arrayed around the MSR complex at 10 to 20 mile distances.

Launch, guidance, and warhead detonation were all controlled by the MSR; its high power beam was capable of penetrating the plasma sheath that surrounded the missile after it reached full velocity. Targets were destroyed by detonation of Sprint's neutron warhead which was specifically designed to minimize collateral damage from its "close in" detonation.

The W66 enhanced radiation warhead aboard Sprint was rated in "the low kiloton range" and would attempt to destroy any re-entry vehicles that had avoided Spartan missiles via neutron flux. The Sprint warhead could ill-afford to be too powerful, as the warhead would detonate reasonably close to the earth in Northeastern North Dakota in a last-ditch effort to intercept enemy warheads.1 <$