ASM-135 ASAT - Design

Design

The ASM-135 was designed to be launched from an F-15A in a supersonic zoom climb. The F-15's mission computer and heads-up display were modified to provide steering directions for the pilot. The actual intercept was done subsonically.

A modified Boeing AGM-69 SRAM missile with a Lockheed Propulsion Company LPC-415 solid propellant two pulse rocket engine was used as the first stage of the ASM-135 ASAT.

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) intercepter. 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 utilized 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 and as it crossed the strips in the sensors 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.