SMDC History: Squirt Serves as Sprint test bed

By Sharon Watkins Lang, USASMDC/ARSTRAT Command HistorianNovember 5, 2014

SMDC History: Squirt Serves as Sprint test bed
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SMDC History: Squirt Serves as Sprint test bed
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The first Squirt rocket blasted into history on Nov. 6, 1963, as a component test bed for candidate materials for the short-range, high-speed Sprint interceptor.

Used during the Sprint development phase, the Squirt test vehicle was designed to gather data on aero-thermal effects, or air friction heating, which would be encountered by "super fast missiles."

According to the official Anti-Ballistic Missile Project History "the ablative heat shield had to survive a low-trajectory, high-velocity environment that generated extremely high boundary-layer temperatures without allowing the underlying missile structure to be exposed to destructive temperature. Also, ablative materials had to be free of contaminants which would attenuate radar communications."

To address these issues, the five Squirt launches, challenged with progressively more severe conditions, looked at various construction and insulation materials for use on the Sprint nosecone.

Although Squirt did not replicate Sprint in design or flight characteristics, it was created to operate in a "Sprint environment," flying at three times faster than the speed of a rifle bullet, and thereby supplementing data garnered from wind tunnel testing. Sprint, the highest acceleration-guided missile to date, was designed to intercept ICBMs travelling 17,000 mph and after they have reentered the earth's atmosphere.

Designed by Martin Marietta, Squirt and its launcher were composed of readily available, off-the-shelf, missile parts. Squirt was a two-stage unguided missile, equipped with an X-band beacon and a telemetry system.

The initial launch came from a bundle of seven Recruit rocket motors. Following booster burnout a cluster of seven Cherokee rockets ignited to propel the Squirt down range. The first two tests used a poly sulfide propellant while the rest were to use a polybutadiene acrylic acid to achieve the necessary velocity of 9,000 feet per second.

Following an "uneventful countdown," Squirt number one was launched from Army Launch Area number three at White Sands Missile Range, N.M. Data -- altitude, velocity and acceleration -- showed that the rocket was on track.

At 1.4 seconds, however, all telemetry and tracking beacons were lost. Analysis of the recovered pieces showed that an internal structural failure terminated the flight after the second stage motors collided with the first stage bulkhead. The failure was traced to second stage motor attachment bolts.

With a redesigned attachment section, Squirt number two was launched on March 17, 1964. All test objectives were met as the rocket achieved a maximum velocity of 8,000 feet per second and a maximum dynamic pressure of approximately 53,500 pounds per square foot.

Although the first test experienced structural failure and was terminated soon after launch, the subsequent Squirt launches realized all test objectives. The flights achieved the expected environment -- velocity, dynamic pressures and heating rates expected in a Sprint flight.

In addition, the recovered test vehicles "showed satisfactory response" for several of the test media to include the silica phenolic nose cap, the tape-wrapped silica phenolic heat shield over the body and two molded silica phenolic air vane leading edges.

Ultimately, the Sprint nose cone was formed with a center rod of quartz phenolic wrapped with a phenolic-impregnated silica tape. The ablative heat shield, which covered the rest of the second stage, was composed of a silica cloth impregnated with phenolic resin mixed with rubber for additional elasticity. Thanks to Squirt, Sprint was ready to move forward.