Supersonic Low Altitude Missile
Encyclopedia
The Supersonic Low Altitude Missile or SLAM (not to be confused with the U.S. Navy's current Standoff Land Attack Missile
) was a canceled U.S. Air Force
project conceived around 1955. Although it never proceeded beyond the initial design and testing phase before being declared obsolete, it represented several radical innovations in tactical aircraft
.
The SLAM was designed to complement the doctrine of mutually assured destruction
, and as a possible replacement for or augment to the Strategic Air Command
system. In the event of nuclear war
it was intended to fly below the cover of enemy radar
at supersonic
speeds, and deliver thermonuclear warhead
s to roughly 16 targets.
The primary innovation was the engine of the aircraft, which was developed under the aegis of a separate project code-named Project Pluto
, after the Roman god of the underworld. It was a ramjet
that used nuclear fission
to superheat incoming air instead of chemical fuel. Project Pluto produced two working prototypes of this engine, the Tory-IIA and the Tory-IIC, which were successfully tested in the Nevada desert. Special ceramic
s had to be developed to meet the stringent weight and tremendous heat tolerances demanded of the SLAM's reactor. These were developed by the Coors Porcelain
Company. The reactor itself was designed at the Lawrence Radiation Laboratory.
The use of a nuclear engine in the airframe
promised to give the missile staggering and unprecedented low-altitude range, estimated to be roughly 113000 miles (181,855.4 km) (over four and a half times the equatorial
circumference of the earth
). The engine also acted as a secondary weapon for the missile: direct neutron radiation from the virtually unshielded reactor would sicken, injure, and/or kill living things beneath the flight path; the stream of fallout
left in its wake would poison enemy territory; and its strategically selected crash site would receive intense radioactive contamination
. In addition, the sonic waves
given off by its passage would damage ground installations.
Another revolutionary aspect of the SLAM was its reliance on automation. It would have the mission of a long-range bomber
, but would be completely unmanned
: accepting radioed commands up to its failsafe point, whereafter it would rely on a Terrain Contour Matching (TERCOM
) radar system to navigate to preprogrammed targets.
Although a prototype of the airframe was never constructed, the SLAM was to be a wingless, fin-guided aircraft. Apart from the ventral ram-air intake
it was very much in keeping with traditional missile
design. Its estimated airspeed
at thirty thousand feet was Mach
4.2.
The SLAM program was scrapped on July 1, 1964. By this time serious questions about its safety had been raised, such as how to test a device that would emit copious amounts of radioactive exhaust from its unshielded reactor core in flight, as well as its efficacy and cost. ICBM
s promised swifter delivery to targets, and because of their speed (the Thor
traveled at roughly Mach 12) and trajectory were considered virtually unstoppable. The SLAM was also being outpaced by advances in defensive ground radar, which threatened to render its stratagem of low-altitude evasion ineffective.
of uranium
was 59.90 kg, and the reactor's power density
averaged at 10 megawatts/cubic foot, with total power of 600 megawatts.
The nuclear fuel
elements were made of refractory ceramic based on beryllium oxide
, with enriched
uranium dioxide
as fuel and small amount of zirconium dioxide
for structural stability. The fuel elements were hollow hexagonal tubes about 4 in long with 0.3 in distance between the outer parallel planes, with inside diameter of 0.227 in. They were manufactured by high-pressure extruding of the green compact, then sintering
almost to its theoretical density
. The core consisted of 465000 individual elements stacked to form 27000 airflow channels; the design with small unattached elements reduced problems related with thermal stresses. The elements were designed for average operation temperature of 2330 °F (1277 °C); the autoignition point of the reactor base plates was only 150 °C higher. The neutron flux
was calculated to be 9×1017 neutrons/cm2.s in the aft and 7×1014 neutrons/cm2.s in the nose. The gamma radiation level was fairly high due to the lack of shielding; radiation hardening
for the guidance electronics had to be designed.
The reactors were successfully tested at Jackass Flats of the Nevada Test Site
. The Tory II-A reactor, the scaled-down variant, was tested in mid-1961 and successfully ran for several seconds on May 14, 1961. A full-scale variant, the Tory II-C, was run for nearly five minutes at full power. The latter test, limited by the air storage facility capacity, ran for 292 seconds. The air fed to the reactor was preheated to 943 °F and compressed to 316 psi, to simulate ramjet flight conditions.
Standoff Land Attack Missile
The Standoff Land Attack Missile or SLAM is a subsonic, over-the-horizon, all-weather standoff cruise missile which grew out of the United States Navy's Harpoon anti-ship missile in the 1970s.-Original SLAM:...
) was a canceled U.S. Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
project conceived around 1955. Although it never proceeded beyond the initial design and testing phase before being declared obsolete, it represented several radical innovations in tactical aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
.
The SLAM was designed to complement the doctrine of mutually assured destruction
Mutual assured destruction
Mutual Assured Destruction, or mutually assured destruction , is a doctrine of military strategy and national security policy in which a full-scale use of high-yield weapons of mass destruction by two opposing sides would effectively result in the complete, utter and irrevocable annihilation of...
, and as a possible replacement for or augment to the Strategic Air Command
Strategic Air Command
The Strategic Air Command was both a Major Command of the United States Air Force and a "specified command" of the United States Department of Defense. SAC was the operational establishment in charge of America's land-based strategic bomber aircraft and land-based intercontinental ballistic...
system. In the event of nuclear war
Nuclear warfare
Nuclear warfare, or atomic warfare, is a military conflict or political strategy in which nuclear weaponry is detonated on an opponent. Compared to conventional warfare, nuclear warfare can be vastly more destructive in range and extent of damage...
it was intended to fly below the cover of enemy radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
at supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
speeds, and deliver thermonuclear warhead
Warhead
The term warhead refers to the explosive material and detonator that is delivered by a missile, rocket, or torpedo.- Etymology :During the early development of naval torpedoes, they could be equipped with an inert payload that was intended for use during training, test firing and exercises. This...
s to roughly 16 targets.
Project Pluto
Project Pluto was a United States government program to develop nuclear powered ramjet engines for use in cruise missiles. Two experimental engines were tested at the United States Department of Energy Nevada Test Site in 1961 and 1964.-History:...
, after the Roman god of the underworld. It was a ramjet
Ramjet
A ramjet, sometimes referred to as a stovepipe jet, or an athodyd, is a form of airbreathing jet engine using the engine's forward motion to compress incoming air, without a rotary compressor. Ramjets cannot produce thrust at zero airspeed and thus cannot move an aircraft from a standstill...
that used nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
to superheat incoming air instead of chemical fuel. Project Pluto produced two working prototypes of this engine, the Tory-IIA and the Tory-IIC, which were successfully tested in the Nevada desert. Special ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
s had to be developed to meet the stringent weight and tremendous heat tolerances demanded of the SLAM's reactor. These were developed by the Coors Porcelain
CoorsTek
CoorsTek, Inc. is a privately owned manufacturer of technical ceramics, semiconductor tooling, plastic tubing, medical devices and other industrial products. CoorsTek’s headquarters and primary factories are located in Golden, Colorado, USA, near the foothills west of Denver. The company is...
Company. The reactor itself was designed at the Lawrence Radiation Laboratory.
The use of a nuclear engine in the airframe
Airframe
The airframe of an aircraft is its mechanical structure. It is typically considered to include fuselage, wings and undercarriage and exclude the propulsion system...
promised to give the missile staggering and unprecedented low-altitude range, estimated to be roughly 113000 miles (181,855.4 km) (over four and a half times the equatorial
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
circumference of the earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
). The engine also acted as a secondary weapon for the missile: direct neutron radiation from the virtually unshielded reactor would sicken, injure, and/or kill living things beneath the flight path; the stream of fallout
Nuclear fallout
Fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and shock wave have passed. It commonly refers to the radioactive dust and ash created when a nuclear weapon explodes...
left in its wake would poison enemy territory; and its strategically selected crash site would receive intense radioactive contamination
Radioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...
. In addition, the sonic waves
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...
given off by its passage would damage ground installations.
Another revolutionary aspect of the SLAM was its reliance on automation. It would have the mission of a long-range bomber
Heavy bomber
A heavy bomber is a bomber aircraft of the largest size and load carrying capacity, and usually the longest range.In New START, the term "heavy bomber" is used for two types of bombers:*one with a range greater than 8,000 kilometers...
, but would be completely unmanned
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...
: accepting radioed commands up to its failsafe point, whereafter it would rely on a Terrain Contour Matching (TERCOM
TERCOM
Terrain Contour Matching, or TERCOM, is a navigation system used primarily by cruise missiles. It uses a pre-recorded contour map of the terrain that is compared to measurements made during flight by an on-board radar altimeter. A TERCOM system considerably increases the accuracy of a missile...
) radar system to navigate to preprogrammed targets.
Although a prototype of the airframe was never constructed, the SLAM was to be a wingless, fin-guided aircraft. Apart from the ventral ram-air intake
Ram-air intake
A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion to increase the static air pressure inside of the intake manifold on an engine, thus allowing a greater massflow through the engine and hence increasing engine power.The ram air intake works by...
it was very much in keeping with traditional missile
Missile
Though a missile may be any thrown or launched object, it colloquially almost always refers to a self-propelled guided weapon system.-Etymology:The word missile comes from the Latin verb mittere, meaning "to send"...
design. Its estimated airspeed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....
at thirty thousand feet was Mach
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
4.2.
The SLAM program was scrapped on July 1, 1964. By this time serious questions about its safety had been raised, such as how to test a device that would emit copious amounts of radioactive exhaust from its unshielded reactor core in flight, as well as its efficacy and cost. ICBM
Intercontinental ballistic missile
An intercontinental ballistic missile is a ballistic missile with a long range typically designed for nuclear weapons delivery...
s promised swifter delivery to targets, and because of their speed (the Thor
PGM-17 Thor
Thor was the first operational ballistic missile of the U.S. Air Force . Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and September 1963 as an intermediate range ballistic missile with thermonuclear warheads. Thor was in height and in diameter. It was...
traveled at roughly Mach 12) and trajectory were considered virtually unstoppable. The SLAM was also being outpaced by advances in defensive ground radar, which threatened to render its stratagem of low-altitude evasion ineffective.
Reactor design
The reactor had outer diameter of 57.25 in and length 64.24 in; the dimension of the reactor core was 47.24 in diameter and 50.70 in length. The critical massCritical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...
of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
was 59.90 kg, and the reactor's power density
Power density
Power density is the amount of power per unit volume....
averaged at 10 megawatts/cubic foot, with total power of 600 megawatts.
The nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
elements were made of refractory ceramic based on beryllium oxide
Beryllium oxide
Beryllium oxide , also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and actually exceeds that of some metals. As an amorphous solid, beryllium...
, with enriched
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...
uranium dioxide
Uranium dioxide
Uranium dioxide or uranium oxide , also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used...
as fuel and small amount of zirconium dioxide
Zirconium dioxide
Zirconium dioxide , sometimes known as zirconia , is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the rare mineral baddeleyite. The high temperature cubic crystalline form is rarely found in nature as mineral tazheranite O2...
for structural stability. The fuel elements were hollow hexagonal tubes about 4 in long with 0.3 in distance between the outer parallel planes, with inside diameter of 0.227 in. They were manufactured by high-pressure extruding of the green compact, then sintering
Sintering
Sintering is a method used to create objects from powders. It is based on atomic diffusion. Diffusion occurs in any material above absolute zero, but it occurs much faster at higher temperatures. In most sintering processes, the powdered material is held in a mold and then heated to a temperature...
almost to its theoretical density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
. The core consisted of 465000 individual elements stacked to form 27000 airflow channels; the design with small unattached elements reduced problems related with thermal stresses. The elements were designed for average operation temperature of 2330 °F (1277 °C); the autoignition point of the reactor base plates was only 150 °C higher. The neutron flux
Neutron flux
The neutron flux is a quantity used in reactor physics corresponding to the total length travelled by all neutrons per unit time and volume . The neutron fluence is defined as the neutron flux integrated over a certain time period....
was calculated to be 9×1017 neutrons/cm2.s in the aft and 7×1014 neutrons/cm2.s in the nose. The gamma radiation level was fairly high due to the lack of shielding; radiation hardening
Radiation hardening
Radiation hardening is a method of designing and testing electronic components and systems to make them resistant to damage or malfunctions caused by ionizing radiation , such as would be encountered in outer space, high-altitude flight, around nuclear reactors, particle accelerators, or during...
for the guidance electronics had to be designed.
The reactors were successfully tested at Jackass Flats of the Nevada Test Site
Nevada Test Site
The Nevada National Security Site , previously the Nevada Test Site , is a United States Department of Energy reservation located in southeastern Nye County, Nevada, about northwest of the city of Las Vegas...
. The Tory II-A reactor, the scaled-down variant, was tested in mid-1961 and successfully ran for several seconds on May 14, 1961. A full-scale variant, the Tory II-C, was run for nearly five minutes at full power. The latter test, limited by the air storage facility capacity, ran for 292 seconds. The air fed to the reactor was preheated to 943 °F and compressed to 316 psi, to simulate ramjet flight conditions.
External links
- The Flying Crowbar from Air And Space Magazine, 1990
- Vought SLAM entry in the Directory of U.S. Military Rockets and Missiles
- SLAM Supersonic Low-Altitude Missile Globalsecurity.org