they could also damage United States reconnaissance satellites. As a result, the United States anti-satellite weapons development efforts were re-directed to develop systems that did not require the use of nuclear weapons.
In 1978, the USAF started a new program initially designated the Prototype Miniature Air-Launched Segment (PMALS) and Air Force Systems Command's Space Division established a system program office. The USAF issued a Request for Proposal for the Air-Launched Miniature Vehicle (ALMV). The requirement was for an air-launched missile that could be used against satellites in low Earth orbit.
Design[edit | edit source]
The LTV Aerospace Altair 3 was used as the second stage of the ASM-135. The Altair 3 used the Thiokol FW-4S solid propellant rocket engine. The Altair 3 stage was also used as the fourth stage for the Scout rocket  and had been previously used in both the Bold Orion and HiHo anti-satellite weapons efforts. The Altair was equipped with hydrazine fueled thrusters that could be used to point the missile towards the target satellite.
LTV Aerospace also provided the third stage for the ASM-135 ASAT. This stage was called Miniature Homing Vehicle (MHV) interceptor. Prior to being deployed the second stage was used to spin the MHV up to approximately 30 revolutions per second and point the MHV towards the target.
A Honeywell ring laser gyroscope was used for spin rate determination and to obtain an inertial timing reference before the MHV separated from the second stage. The infrared sensor was developed by Hughes Research Laboratories. The sensor used a strip detector where four strips of Indium Bismuth were arranged in a cross and four strips were arranged as logarithmic spirals. As the detector was spun, the infrared target's position could be measured as it crossed the strips in the sensor's field of view. The MHV infrared detector was cooled by liquid helium from a dewar installed in place of the F-15's gun ammunition drum and from a smaller dewar located in the second stage of the ASM-135. Cryogenic lines from the second stage were retracted prior to the spin up of the MHV.
The MHV guidance system solely tracked targets in the field of view of the infrared sensor, but did not determine altitude, attitude, or range to the target. Direct Proportional Line of Sight guidance used information from the detector to maneuver and null out any line-of-sight change. A Bang-bang control system was used to fire 56 full charge "divert" and lower thrust 8 half charge "end-game" solid rocket motors arranged around the circumference of the MHV. The half charge 8 "end-game" motors were used to perform finer trajectory adjustments just prior to intercepting the target satellite. Four pods at the rear of the MHV contained small attitude control rocket motors. These motors were used to damp off center rotation by the MHV.
Test launches[edit | edit source]
On 20 August 1985 President Reagan authorized a test against a satellite. The test was delayed to provide notice to the United States Congress. The target was the Solwind P78-1, an orbiting solar observatory that was launched on 24 February 1979.
On 13 September 1985, Maj. Wilbert D. "Doug" Pearson, flying the "Celestial Eagle" F-15A 76-0084 launched an ASM-135 ASAT about 322 km (200 miles) west of Vandenberg Air Force Base and destroyed the Solwind P78-1 satellite flying at an altitude of 555 km (345 miles). Prior to the launch, the F-15 - flying at Mach 1.22 - executed a 3.8g zoom climb at an angle of 65 degrees. The ASM-135 ASAT was automatically launched at 11.6 km while the F-15 was flying at Mach .934. The 13.6 kg (30 lb) MHV collided with the 907 kg (2,000 lb) Solwind P78-1 satellite at closing velocity of 24,140 km/h (15,000 mph).
NASA learned of U.S. Air Force plans for the Solwind ASAT test in July 1985. NASA modeled the effects of the test. This model determined that debris produced would still be in orbit in the 1990s. It would force NASA to enhance debris shielding for its planned space station.
Earlier the U.S. Air Force and NASA had worked together 