YAL-1A Airborne Laser Testbed (ALTB)
Throughout the ABL's development the question of the true concept of operations was extremely relevant both in terms of its practical future and to the proposed number of aircraft to be brought into inventory. Questions were raised in a Congressional Research Service report in 2007 about other potential systems to theatre target ballistic missile threats in the boost phase, further highlighting the importance of how the ABL would be integrated into the overall missile defense plan.
The ABL initially had a proposed crew of four, including pilot and copilot, would be required to operate the airborne laser, which will patrol in pairs at high altitude, about 40,000 feet. By March 2003 this number had official been increased to six: pilot, copilot, mission crew commander, airborne surveillance officer, weapon system operator, and special equipment operator. It was also noted that because of the aircraft's inflight refueling capability and therefore its ability to stay on station for extended periods of time, an additional crew member might be added to reduce pilot or operator fatigue. The ABL system has been designed to be a component part of ballistic missile defense plans, complimenting other systems designed to target ballistic missiles in other stages of their flight trajectory. These include ground based interceptors such as the THAAD and PAC-3 variant of the MIM-104 Patriot missile series, RIM-161 Standard SM-3 naval based interceptors, and others. The ABL has also been suggested as a defense mechanism against other types of missiles, including air to air, surface to air, and cruise missiles.
The proposed operational sequence involves the aircraft, operating autonmously, flying in orbits over friendly territory and scanning the horizon for the plumes of rising missiles using a total of six infrared sensors placed around the aircraft. A kilowatt class tracking laser, known as the Track Illuminator would then mark the target and be used to determine a precise aim point. Onboard computers would measure the distance and calculate the missile's course and direction. A second kilowatt-class laser, referred to as the Beacon Illuminator, would then measures disturbances in the atmosphere, which are corrected by the adaptive optics system to accurately point and focus the high energy laser at its intended target. After so acquiring and locking onto the target, a megawatt class laser located in the nose turret and operated via a very large telescope and the beam control/fire control system focuses would be focused onto a pressurized area of the boosting missile, holding it there until the concentrated energy causes the missile to break apart. It was speculated that a a three to five second burst from the laser would be sufficient. The missiles would be destroyed over the launch area. Originally it was planned that only one kilowatt class laser would be required for aiming the primary weapon.
While able to operate autonomously in its mission, the overall characteristics of the ABL aircraft and its weapon system would likely require fighter escort. The nature of the aircraft also raised the possibility that the system could be defeated simply by waiting for an opportunity where the aircraft was refueling or otherwise absent from its post. The ABL was also intended to be an in theatre system with a long on station time. This would require the forward basing of the aircraft. The nature of the fuel required for laser operation raised doubts about whether this could be easily placed at forward operating sites. Developments in the fuel were most likely targeted at this concern, as well as, improving onboard safety.
If the fuel required for aircraft were restricted to bases in the United States, this would mean that the aircraft would have to leave its theatre and return to its home base for recharging. By 2004, the only facility set up to produce and mix the laser's fuel was Edwards Air Force Base in California. A projected ability for three "constrained" fire missions for the ABL without recharging had been cited in a 2004 GAO report. Forward basing required the deployment of specialized maintenance assets as well, because of the highly complex nature of the aircraft's systems. Projected costs for operation were undefined at the time of the GAO report in 2004, but projected to be higher than the per hour operating costs of the Airborne Early Warning System or Joint Surveillance Target Attack System, at $24,000 and $92,000 respectively.
With all of these factors it was posited that the intially planned fleet of seven aircraft might only be able to provide a 24 hour a day defense in a single theatre, requiring multiple fleets at additional cost to extend the coverage to multiple theatres. In the spring of 2006, the Department of Defense decided to suspend purchase of five ABL aircraft because of developmental delays, leaving only the two planned prototype aircraft, of which only one was in inventory as of 2007. By the end of 2007 neither of these aircraft had performed a lethality demonstration, which raised the question in the 2007 CRS report about what use either of these aircraft might have operationally in the event that the deployment might become necessary.
The 2004 GAO report also noted that the ABL's approximate range of 400 km (250 miles) made it impossible to engage ICBM targets, then a potential primary target, from a stand off range against the nations who already possess these systems, Russia and China. This would have meant that the ABL would be required to fly into hostile territory in order to engage the targets, a more active defense than projected in the initial operating concept of defensive ABL orbits. At the time of the CRS report's publishing in 2007 nations like North Korea and Iran did not possess an ICBM capability. The ability of the ABL to engage launches in either of those countries from a stand off range was also debatable. A 2004 study by the American Physical Society of Boost-Phase Interceptors including the ABL, noted that if the system worked as planned it might be able to achieve a range of 600 km (closer to 400 miles). The ability of the ABL to fire on targets at such a range still presented the problem of being able to engage targets in North Korea, but not Iran, unless the ABL units could be stationed over the Caspian or in Turkmenistan. No actual assessment of the military utility of the ABL demonstrator, the only aicraft in inventory, had been scheduled as of 2007.
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