Solar Turbines Incorporated, a wholly owned subsidiary of

Caterpillar Inc. Caterpillar Inc. (stock symbol CAT) is an American ''Fortune'' 500 corporation and the world's largest construction-equipment manufacturer. In 2018, Caterpillar was ranked number 65 on the ''Fortune'' 500 list and number 238 on the Global ''Fo ...

, designs and manufactures industrial

gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...

s for onshore and offshore electrical power generation, for marine propulsion and for producing, processing and transporting natural gas and oil. The company traces its history to the 1927 founding of the Prudden-San Diego Airplane Company, which became the Solar Aircraft Company in 1929. Through the

Great Depression The Great Depression (19291939) was an economic shock that impacted most countries across the world. It was a period of economic depression that became evident after a major fall in stock prices in the United States. The economic contagio ...

, they mainly produced components for other manufacturers, growing during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

and diversifying into non-aircraft products after the war. During this period, they won a number of contracts to produce jet engine components. Convinced that the

was the prime mover of the future, the company invested heavily in the development of small

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating e ...

s. The turbine never came to be the main prime mover, but Solar's expertise in small turbines found a number of niche roles. The company was purchased by

International Harvester Company The International Harvester Company (often abbreviated by IHC, IH, or simply International ( colloq.)) was an American manufacturer of agricultural and construction equipment, automobiles, commercial trucks, lawn and garden products, household e ...

in early 1960, becoming the Solar Division of International Harvester in 1963. In 1973, the Solar Division exited the aerospace industry to focus solely on industrial turbines. In 1975, the development and manufacture of the Solar Division's radial engines was moved into a newly formed Radial Engines Group, renamed the Turbomach Division in 1980. Solar Turbines Incorporated became a wholly owned subsidiary of Caterpillar Tractor Co. after Caterpillar purchased the assets of the Solar Division and the Turbomach division from International Harvester on 31 May 1981. In 1985, Caterpillar sold the Turbomach Division to

Sundstrand Corporation Sundstrand Corporation was founded in 1926 as a merger of the Rockford Tool Company and Rockford Milling Machine Company in Rockford, Illinois. It was known as Sundstrand Machine Tool Company until 1959 when shareholders voted to change the name ...

Prudden-San Diego Airplane Company

Solar Turbines traces its roots to the Prudden-San Diego Airplane Company, a partnership founded in 1927 between George Prudden and seven

San Diego San Diego ( , ; ) is a city on the Pacific Ocean coast of Southern California located immediately adjacent to the Mexico–United States border. With a 2020 population of 1,386,932, it is the List of United States cities by population, eigh ...

area businessmen. Due to differences in management philosophy between Prudden and his investors, Prudden left the company in November 1928.

Solar Aircraft Company

First product - a trimotor airplane

In March 1929, Prudden-San Diego Airplane Company changed its name to Solar Aircraft Company, a reference to San Diego's sunny climate. Solar Aircraft Company's main product was an all-metal passenger aircraft powered by three

Siemens & Halske Siemens & Halske AG (or Siemens-Halske) was a German electrical engineering company that later became part of Siemens. It was founded on 12 October 1847 as ''Telegraphen-Bauanstalt von Siemens & Halske'' by Werner von Siemens and Johann Geo ...

radial engines The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is cal ...

. Due to the

in 1929, the company was unable to market the aircraft and made only three airplanes.

From airplanes to airplane components

The sales failure of the tri-motor airplane due to the Great Depression led Solar Aircraft Company into making parts for other manufacturers, especially hard-to-manufacture parts able to withstand high-temperatures, such as

stainless steel Stainless steel is an alloy of iron that is resistant to rusting and corrosion. It contains at least 11% chromium and may contain elements such as carbon, other nonmetals and metals to obtain other desired properties. Stainless steel's corros ...

exhaust manifolds. The company was reincorporated in 1937 as the Solar Aircraft Company, dropping the "Ltd" from its name. By 1939, Solar Aircraft Company had a work force of 229. Military orders during

led to rapid expansion and by the end of the war the company had a workforce of 5,000, largely part of a massive effort to build more than 300,000 exhaust manifolds for U.S. airplanes. Business dropped considerably after World War II and the management developed a plan to diversify into producing other stainless steel products including caskets, frying pans, bulk milk containers and even redwood furniture; immediately after World War II, the company also produced the

Solar Midget The Solar midget car was a type of midget car racing vehicle produced by the Solar Aircraft Company immediately following the end of World War II. The first midget car to be mass-produced, the vehicle was designed by Elmer Ross using a car body desi ...

race car. Solar's expertise in hard-to-manufacture parts able to withstand high-temperatures led to contracts to produce jet engine components. Solar Aircraft began to design and manufacture completed turbine engines for the United States military for applications such as

auxiliary power unit An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion. They are commonly found on large aircraft and naval ships as well as some large land vehicles. Aircraft APUs generally produce 115&n ...

fuselage The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft t ...

s, and

rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...

components of

guided missiles In military terminology, a missile is a guided airborne ranged weapon capable of self-propelled flight usually by a jet engine or rocket motor. Missiles are thus also called guided missiles or guided rockets (when a previously unguided rocket i ...

. Solar Aircraft continued to expand its product line and grow its business until it was purchased by

in early 1960, becoming the Solar Division of International Harvester in 1963.

Developing expertise in gas turbines

Solar Aircraft Company's expertise in high-temperature metallurgy led to work producing components for some of the first US

jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...

s, including the General Electric I-40 and a contract from the

US Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage of ...

to build an

afterburner An afterburner (or reheat in British English) is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and comba ...

for the

Westinghouse J34 The Westinghouse J34, company designation Westinghouse 24C, was a turbojet engine developed by Westinghouse Aviation Gas Turbine Division in the late 1940s. Essentially an enlarged version of the earlier Westinghouse J30, the J34 produced 3,000 p ...

. Solar Aircraft Company also won contracts for the

Allison J33 The General Electric/Allison J33 is a development of the General Electric J31, enlarged to produce significantly greater thrust, starting at and ending at with an additional low-altitude boost to with water-alcohol injection. Development Th ...

Allison J35 The General Electric/Allison J35 was the United States Air Force's first axial-flow (straight-through airflow) compressor jet engine. Originally developed by General Electric (GE company designation TG-180) in parallel with the Whittle-based c ...

Avro Canada Orenda The Avro Canada TR5 Orenda was the first production jet engine from Avro Canada's Gas Turbine Division. Similar to other early jet engines in design, like the Rolls-Royce Avon or General Electric J47, the Orenda nevertheless outperformed its ...

, and

Bristol Olympus The Rolls-Royce Olympus (originally the Bristol B.E.10 Olympus) was the world's second two- spool axial-flow turbojet aircraft engine design, first run in May 1950 and preceded only by the Pratt & Whitney J57, first-run in January 1950. It is ...

. It was during this time that one of its engineers, Wendell Reed, developed the pneumatic engine microjet controller, for which he won the

Wright Brothers Medal The Wright Brothers Medal was conceived of in 1924 by the Dayton Section of the Society of Automotive Engineers, and the SAE established it in 1927 to recognize individuals who have made notable contributions in the engineering, design, developmen ...

in 1955 and which became widely used for gas turbines, afterburners, and ramjets. This controller is described in "Flight" magazine, 2 December 1955. Solar Aircraft Company's work in the jet engine field convinced the company's president, Edmund Price, that the turbine would be the main prime mover in the future. Solar Aircraft Company assembled a team under the direction of Paul Pitt in 1946 and started developing a small

axial-flow An axial compressor is a gas compressor that can continuously pressurize gases. It is a rotating, airfoil-based compressor in which the gas or working fluid principally flows parallel to the axis of rotation, or axially. This differs from othe ...

turbine as an

for the

US Army Air Force The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

Convair B-36 The Convair B-36 "Peacemaker" is a strategic bomber that was built by Convair and operated by the United States Air Force (USAF) from 1949 to 1959. The B-36 is the largest mass-produced piston-engined aircraft ever built. It had the longest win ...

strategic bomber A strategic bomber is a medium- to long-range penetration bomber aircraft designed to drop large amounts of air-to-ground weaponry onto a distant target for the purposes of debilitating the enemy's capacity to wage war. Unlike tactical bombers, ...

. The Army eventually canceled this contract, but Solar Aircraft Company soon won a contract from the

in 1947 for a 250 kW system to provide emergency power on ships. First running in 1949, the T-400 would go on to provide power on

minesweeper A minesweeper is a small warship designed to remove or detonate naval mines. Using various mechanisms intended to counter the threat posed by naval mines, minesweepers keep waterways clear for safe shipping. History The earliest known usage of ...

s and

landing craft Landing craft are small and medium seagoing watercraft, such as boats and barges, used to convey a landing force (infantry and vehicles) from the sea to the shore during an amphibious assault. The term excludes landing ships, which are larger. Pr ...

Solar did win the contract to provide the APU for the first 632

KC-135A The Boeing KC-135 Stratotanker is an American military aerial refueling aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It is the predominant variant of the C-135 Stratolifter family of transpo ...

tankers for the

Strategic Air Command Strategic Air Command (SAC) was both a United States Department of Defense Specified Command and a United States Air Force (USAF) Major Command responsible for command and control of the strategic bomber and intercontinental ballistic missile ...

. In 1947, Leon Wosika and Eric Balje set up a second design line and developed a centrifugal-flow system that was much more compact than Solar's previous designs. Originally known as the MPM-45, the unit was delivered as the "Mars". The Navy purchased the Mars to power portable fire fighting pumps on ships and gave it the designation T41. In 1956, the Navy turned to Solar to provide a slightly larger design to power a small helicopter, the Gyrodyne XRON-1. Solar Aircraft Company responded by developing a slightly larger version of the Mars, the "Titan", which the Navy designated the T62. When the Navy abandoned development of Gyrodyne's XRON helicopter, Solar Aircraft Company adapted the Titan for service as an

. Deliveries of this auxiliary power unit started in 1962. The Navy also had Solar adapt the Titan into a free-turbine version designated by the Navy as the T66, but this unit was never put into use. Solar Aircraft Company designed other versions of the basic Mars design, including the Spartan, and the Gemini. sdw In the late 1950s, the Navy once again turned to Solar, this time for a larger unit that would be used as an engine in a high-speed boat. The result was the axial-flow "Saturn" engine, which entered production in 1960. Solar started marketing the Saturn to industrial users needing a unit for any role, and it went on to become the world's most widely used industrial gas turbine with some 4800 units in 80 countries. It remains in production today in two uprated and enhanced configurations. In order to make the system more attractive, Solar also started the design of various "front ends" that could be purchased as a complete unit with the Saturn. These included gas compressor sets, pump-drive packages and generator sets. These units, especially the gas compressors, are widely used in the

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

industry as pumping units on pipelines.

Solar Division of International Harvester

Just prior to the release of the Saturn, International Harvester purchased Solar Aircraft Company in early 1960. In 1963, Solar Aircraft Company was re-organized as the Solar Division of International Harvester. During the next decade, the Solar Division introduced a number of new designs, both larger and smaller than the Saturn. The Centaur, which first entered service in 1968, supplied , while the modern versions supply . In 1973, Solar exited the aviation industry to concentrate its resources on industrial gas turbines.

Products separated into two divisions

In the spring of 1975, International Harvester placed Solar Division's radial engine designs into the newly formed Radial Engine Group. In 1980, the Radial Engine Group was renamed, becoming the Turbomach Division. In 1977, the Solar Division introduced a larger version of the Centaur, the Mars, re-using the name from the earlier smaller engine. The Mars is currently sold as the Mars 90 and Mars 100.

Wholly owned subsidiary of Caterpillar Inc.

Caterpillar Tractor Co. purchased the assets of the Solar Division and the Turbomach Division from International Harvester on May 31, 1981. The newly acquired assets were organized as a wholly owned subsidiary of Caterpillar Tractor Co. named Solar Turbines Incorporated. After the purchase, Caterpillar assigned development and manufacturing of the Caterpillar Model 5600 to Solar Turbines. The 5600 was originally developed by

The Boeing Company The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

as the Boeing 551/553 series, which Caterpillar had purchased when Boeing decided to exit the gas turbine business in 1966.

Sale of Turbomach Division to Sundstrand

In 1985, Caterpillar sold the Turbomach Division to

(now

Collins Aerospace Collins Aerospace is an American technology corporation that is one of the world's largest suppliers of aerospace and defense products. Headquartered in Charlotte, North Carolina, it is a subsidiary of Raytheon Technologies. History On No ...

), exiting the Centrifugal gas turbine engine business.

New products in the 80s and 90s

Solar Turbines Incorporated continued to introduce new versions of their axial-flow industrial engines throughout the 1980s and 90s, often re-using older names instead of introducing new names. In 1997, Solar Turbines Incorporated announced the Titan 130, a design much larger than the original Titan. The latest model, the Titan 250, delivers . Solar Turbines Incorporated has also been involved in a number of projects to improve the fuel economy of industrial turbines of all sorts. In 1992, Solar Turbines introduced the SoLoNOx system. The SoLoNOx system uses lean-burn technologies to reduce

NOx In atmospheric chemistry, is shorthand for nitric oxide () and nitrogen dioxide (), the nitrogen oxides that are most relevant for air pollution. These gases contribute to the formation of smog and acid rain, as well as affecting tropos ...

emissions. The SoLoNOx system has been retrofitted to over 2,000 turbines and all of Solar Turbine's more recent designs can be equipped with SoLoNOx as a feature. In 1997, Solar Turbines introduced a ceramic hot-section design for the Centaur 50 and introduced a

recuperator A recuperator is a special purpose counter-flow energy recovery heat exchanger positioned within the supply and exhaust air streams of an air handling system, or in the exhaust gases of an industrial process, in order to recover the waste heat. ...

for the Mercury 50, in experiments conducted with the

US Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United State ...

Purchase of Turbomach S.A.

In 2004 Caterpillar acquired Swiss company Turbomach S.A. which had long been a packager of industrial turbines from Solar, Rolls-Royce, and Trent.

Current product line

Solar Turbine Incorporated's product line currently consists of the Saturn, Centaur, Mercury, Taurus, Mars and Titan turbines, and a variety of attachments that are sold with them. To date, Solar has sold more than 15,000 gas turbine systems, with a combined operating history of over 2 billion hours of use, equivalent to over 100,000 years.

Products

Note: Specifications are for natural gas fuel. MPU stands for Mobile Power Unit (trailer mounted). SMT stands fo
Solar Mobile Turbomachinery
which is specifically designed to not need a crane to setup.

References

Notes

Bibliography

* * * * * * {{Caterpillar 1927 establishments in California Aircraft component manufacturers of the United States Aircraft engine manufacturers of the United States American brands American companies established in 1927 Caterpillar Inc. subsidiaries Engine manufacturers of the United States Gas turbine manufacturers Manufacturing companies based in San Diego Manufacturing companies established in 1927 Renewable resource companies established in 1927 Solar energy in California