Editing Boeing YAL-1 (section)

== Design ==
[[File:USAF Airborne laser.jpg|thumb|Artist impression of two YAL-1As shooting down ballistic missiles. The laser beams are highlighted red for visibility. (In reality, they would be invisible to the naked eye.)]]

=== COIL ===
The heart of the system was the COIL, comprising six interconnected modules, each as large as an [[SUV]].  Each module weighed about 6,500 pounds (3,000&nbsp;kg).  When fired, the laser used enough energy in a five-second burst to power a typical American household for more than an hour.<ref name="atn1">{{cite web|author=Grill, Tech. Sgt. Eric M. |url=https://www.af.mil/News/story/id/123045745/ |title=Airborne Laser fires tracking laser, hits target |publisher=Air Force |date=March 21, 2007 |url-status=live |archive-url=https://web.archive.org/web/20081211212241/http://www.af.mil/news/story.asp?id=123045745 |archive-date=December 11, 2008 |df=mdy }}</ref>

=== Use against ICBMs vs TBMs ===
[[File:Airbornelaserturret.jpg|thumb|upright|Laser Turret, said by the US Air Force to be the world's largest.]]

The ABL was designed for use against [[tactical ballistic missile]]s (TBMs). These have a shorter range and fly more slowly than [[ICBM]]s.  The MDA had suggested the ABL might be used against ICBMs during their boost phase. This could require much longer flights to get in position, and might not be possible without flying over hostile territory.  Liquid-fueled ICBMs, which have thinner skins, and remain in boost phase longer than TBMs, might be easier to destroy.{{Citation needed|date=August 2011}}

If the ABL had achieved its design goals, it could have destroyed liquid-fueled ICBMs up to 600&nbsp;km away.  Tougher solid-fueled ICBM destruction range would likely have been limited to 300&nbsp;km, too short to be useful in many scenarios, according to a 2003 report by the [[American Physical Society]] on [[National Missile Defense]].<ref>{{cite web |url=http://www.aps.org/about/pressreleases/boosts2.cfm |title=APS Study |publisher=aps.org |url-status=dead |archiveurl=https://web.archive.org/web/20070213231108/http://www.aps.org/about/pressreleases/boosts2.cfm |archive-date=February 13, 2007 |df=mdy }}</ref>

=== Intercept sequence ===
The ABL system used infrared sensors for initial missile detection.  After initial detection, three low-power tracking lasers calculated missile course, speed, aimpoint, and air turbulence.  Air turbulence deflects and distorts lasers.  The ABL [[adaptive optics]] use the turbulence measurement to compensate for atmospheric errors.  The main [[laser]], located in a turret on the aircraft nose, could be fired for 3 to 5 seconds, causing the missile to break up in flight near the launch area.  The ABL was not designed to intercept TBMs in the terminal or descending flight phase.  Thus, the ABL would have had to be within a few hundred kilometers of the missile launch point.  All of this would have occurred in approximately 8 to 12 seconds.<ref>{{cite web|url=http://www.airborne-laser.com/how_does_it_work.php|title=How Does it work - Airborne Laser|website=www.airborne-laser.com|access-date=March 18, 2018|archive-date=March 23, 2016|archive-url=https://web.archive.org/web/20160323025610/http://www.airborne-laser.com/how_does_it_work.php|url-status=usurped}}</ref>

=== Operational considerations ===
[[File:Lasertests.jpg|thumb|upright|A technician evaluates the interaction of multiple lasers for use aboard the Airborne Laser.]]

The ABL did not burn through or disintegrate its target. It heated the missile skin, weakening it, causing failure from high-speed flight stress. The laser used chemical fuel similar to rocket propellant to generate the high laser power. Plans called for each 747 to carry enough laser fuel for about 20 shots, or perhaps as many as 40 low-power shots against fragile TBMs. To refuel the laser, YAL-1 would have to land. The aircraft itself could have been refueled in flight, which would have enabled it to stay aloft for long periods. Preliminary operational plans called for the ABL to be escorted by fighters and possibly [[electronic warfare]] aircraft. The ABL aircraft would likely have had to orbit near potential launch sites (located in hostile countries) for long periods, flying a figure-eight pattern that allows the aircraft to keep the laser aimed toward the missiles.<ref>{{cite book| author = Congress| title = Congressional Record| url = https://books.google.com/books?id=oj5jAMspUfAC&pg=PA11290| year = 2011| publisher = Government Printing Office | isbn = 9780160924286}}</ref>

=== Use against other targets ===
In theory, an airborne laser could be used against hostile fighter aircraft, cruise missiles, or even low-Earth-orbit satellites (see [[anti-satellite weapon]]). However, the YAL-1 infrared target acquisition system was designed to detect the hot exhaust of TBMs in boost phase. Satellites and other aircraft have a much lower heat signature, making them more difficult to detect. Aside from the difficulty of acquiring and tracking a different kind of target, ground targets such as armored vehicles and possibly even aircraft are not fragile enough to be damaged by a megawatt-class laser.

An analysis by the [[Union of Concerned Scientists]] discusses potential airborne laser use against low Earth orbit satellites.<ref>{{cite web 
 | url = http://www.ucsusa.org/global_security/space_weapons/asat-capabilities-of-us-missile-defense-systems.html | title = Anti-Satellite Capabilities of Planned US Missile Defense Systems | work = ucsusa.org | publisher = [[Union of Concerned Scientists]] | date = December 9, 2002 | first1 = David | last1 = Wright | first2 = Laura | last2 = Grego | author2-link = Laura Grego | url-status = dead | archive-url = https://web.archive.org/web/20051211090828/http://www.ucsusa.org/global_security/space_weapons/asat-capabilities-of-us-missile-defense-systems.html | archive-date = December 11, 2005 |df=mdy }}</ref> Another program, the [[Advanced Tactical Laser]], envisions air-to-ground use of a megawatt-class laser mounted on an aircraft better suited for low altitude flight.<ref>http://goliath.ecnext.com/coms2/product-compint-0000806204-page.html {{Dead link|date=September 2022}}</ref>