The
Texas Instruments
Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globall ...
BOLT-117 (BOmb, Laser Terminal-117), retrospectively redesignated as the GBU-1/B (Guided Bomb Unit)
was the world's first
laser-guided bomb
A laser-guided bomb (LGB) is a guided bomb that uses semi-active laser guidance to strike a designated target with greater accuracy than an unguided bomb. First developed by the United States during the Vietnam War, laser-guided bombs quickly p ...
(LGB). It consisted of a standard
M117 bomb case with a KMU-342
laser guidance
Laser guidance directs a robotics system to a target position by means of a laser beam. The laser guidance of a robot is accomplished by projecting a laser light, image processing and communication to improve the accuracy of guidance. The key ide ...
and control kit. This consisted of a
gimbal
A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of ...
led laser seeker on the front of the bomb and tail and control fins to guide the bomb to the target. The latter used the
bang-bang method of control where each control surface was either straight or fully deflected. This was inefficient
aerodynamically
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
, but reduced costs and minimized demands on the primitive onboard
electronics
The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...
.
![F-4D 497th TFS with BOLT-117s 1971](https://upload.wikimedia.org/wikipedia/commons/9/91/F-4D_497th_TFS_with_BOLT-117s_1971.jpg)
Originally the project began as a surface-to-air missile seeker developed by Texas Instruments (TI). When TI executive Glenn E. Penisten attempted to sell the new technology to the
United States Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
(USAF),
Colonel
Colonel (abbreviated as Col., Col or COL) is a senior military officer rank used in many countries. It is also used in some police forces and paramilitary organizations.
In the 17th, 18th and 19th centuries, a colonel was typically in charge of ...
Joe Davis Jr. inquired if it could instead be used as a ground attack system to overcome problems US aircraft were having with the poor accuracy of bombing in Vietnam. Davis had already witnessed a test of the
United States Army
The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
's new laser target designator made by
Martin Marietta
The Martin Marietta Corporation was an American company founded in 1961 through the merger of Glenn L. Martin Company and American-Marietta Corporation. In 1995, it merged with Lockheed Corporation to form Lockheed Martin.
History
Martin Mari ...
, but no seeker existed to make use of the system. Davis had already performed tests from the back seat of an
F-4 Phantom II
The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber originally developed by McDonnell Aircraft for the United States Navy.Swanborough and Bow ...
fighter bomber
A fighter-bomber is a fighter aircraft that has been modified, or used primarily, as a light bomber or attack aircraft. It differs from bomber and attack aircraft primarily in its origins, as a fighter that has been adapted into other roles, wh ...
and proved that it was possible to accurately target objects from a moving aircraft. His mock testing proved correct, and during further testing with live seekers, it took just six attempts to improves the seeker accuracy from to within of the target. This greatly exceeded the design requirements. It was commissioned by the USAF in 1967.
The BOLT-117 and
Paveway I
Paveway is a series of laser-guided bombs (LGBs).
''Pave'' or PAVE is sometimes used as an acronym for ''precision avionics vectoring equipment''; literally, electronics for controlling the speed and direction of aircraft. Laser guidance is a ...
(based on the more streamlined
Mk 84 2,000-pound bomb) underwent combat evaluation with the
8th Tactical Fighter Wing
The United States Air Force 8th Fighter Wing is the host unit at Kunsan Air Base, Republic of Korea and is assigned to Seventh Air Force. Seventh Air Force falls under Pacific Air Forces (PACAF). The Wing's 8th Operations Group is the success ...
in Southeast Asia from May to August 1968. The first combat drop of a laser guided bomb was made using BOLT-117s on 23 May 1968. Without the existence of tracking pods, the Weapon Systems Officer (WSO) in the back seat of an F-4 Phantom II used a hand-held ''Airborne
Laser Designator
A laser designator is a laser light source which is used to designate a target. Laser designators provide targeting for laser-guided bombs, missiles, or precision artillery munitions, such as the Paveway series of bombs, AGM-114 Hellfire, or ...
'' to guide the bombs, but half of the LGBs still hit their targets despite the difficulties inherent in keeping the laser on the target.
Placement of the
control surfaces on the rear of the bomb proved to be less than ideal as it limited the ability of the fins to control the bomb's
trajectory
A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete traj ...
. In the combat evaluations the BOLT-117 achieved a
circular error probability
In the military science of ballistics, circular error probable (CEP) (also circular error probability or circle of equal probability) is a measure of a weapon system's precision. It is defined as the radius of a circle, centered on the mean, w ...
(CEP) of while the Paveway I achieved a CEP of with one in every four bombs scoring a direct hit.
Only a limited number of BOLT-117 bombs were produced before it was discontinued in favor of the more accurate Paveway I family of guidance kits that moved the control fins to the front of the bomb. The Paveway variant was very successful and over 28,000 Paveway weapons were dropped during the war in Vietnam.
The impact of the BOLT-117 on
aerial warfare
Aerial warfare is the use of military aircraft and other flying machines in warfare. Aerial warfare includes bombers attacking enemy installations or a concentration of enemy troops or strategic targets; fighter aircraft battling for control o ...
was revolutionary, allowing the destruction of targets even other existing precision weapons had difficulty destroying due to having small warheads and difficulty tracking certain types of objects. Earlier electro-optical weapons such as the
AGM-62 Walleye
The AGM-62 Walleye is a television-guided glide bomb which was produced by Martin Marietta and used by the United States Armed Forces from the 1960s-1990s. Most had a 250 lb (113 kg) high-explosive warhead; some had a nuclear warhea ...
could accurately strike targets with small outlines and good contrast on camera but had difficulty hitting large oddly shaped structures like bridges. Laser-guided weapons allowed far greater precision against these types of targets, and with much larger warheads.
John Darrell Sherwood
John Darrell Sherwood (born 1966) is an American author who has published five books and numerous articles. He specializes in military history, but has also published articles on travel and skiing. He has been with the Naval History and Heritag ...
, ''Nixon's Trident: Naval Power in Southeast Asia, 1968–1972,'' (Washington: DC: Naval Historical Center
The Naval History and Heritage Command, formerly the Naval Historical Center, is an Echelon II command responsible for the preservation, analysis, and dissemination of U.S. naval history and heritage located at the historic Washington Navy Yard. ...
, forthcoming).
Another equally important improvement was the ability to use add-on guidance kits to turn standard "dumb" ordnance into
precision-guided munition
A precision-guided munition (PGM, smart weapon, smart munition, smart bomb) is a guided munition intended to precisely hit a specific target, to minimize collateral damage and increase lethality against intended targets. During the First Gul ...
yielding a considerable increase in effectiveness compared with free-falling,
unguided bomb
An unguided bomb, also known as a free-fall bomb, gravity bomb, dumb bomb, or iron bomb, is a conventional or nuclear aircraft-delivered bomb that does not contain a guidance system and hence simply follows a ballistic trajectory. This described ...
s, and doing so at a fraction of the cost of other guided weapons. The cost of the add-on kits was only a few percent of the original $100,000 price goal.
References
External links
{{commons category, BOLT-117
BOLT-117 (BOmb, Laser Terminal-117) - Global Security*
ttp://www.vectorsite.net/twbomb_05.html#m2 Modern glide bombs on VectorsiteBOLT-117 at nd.edu
Cold War aerial bombs of the United States
Weapon guidance
Guided bombs of the United States
Texas Instruments