Solar Turbines
| Company type | Subsidiary |
|---|---|
| Industry | Industrial gas turbines |
| Predecessor | Prudden-San Diego Airplane Company, Solar Aircraft Company, Solar Division of International Harvester |
| Founded | 1927 |
| Founder | George Prudden and seven San Diego entrepreneurs |
| Fate | Acquired by Caterpillar Inc. (1981) |
| Headquarters | San Diego , United States |
Area served | Worldwide |
Key people | Edmund Price (former president) |
| Products | Industrial gas turbines (Saturn, Centaur, Mercury, Taurus, Mars, Titan series), accessories |
| Owner | Caterpillar Inc. |
| Parent | Caterpillar Inc. |
| Website | www |
Solar Turbines Incorporated, a fully owned subsidiary of Caterpillar Inc., specializes in the design and production of industrial gas turbines used in onshore and offshore power generation, marine propulsion, as well as natural gas and oil extraction and transportation.
The company's roots trace back to 1927 when it was established as the Prudden-San Diego Airplane Company, later renamed Solar Aircraft Company in 1929. During the Great Depression, the firm shifted to manufacturing components for other producers, expanded operations throughout World War II, and diversified its product line after the war by entering non-aviation markets, including contracts for jet engine parts. Identifying the promise of gas turbines, Solar invested substantially in developing small turbine technology.
Although gas turbines never became the dominant prime mover, Solar's proficiency allowed it to capture specialized market segments. In 1960, International Harvester Company acquired Solar, which was rebranded as the Solar Division of International Harvester by 1963. By 1973, Solar had withdrawn from aerospace activities to concentrate solely on industrial turbine production. In 1975, production of radial engines was transferred to a newly formed Radial Engines Group, which was renamed the Turbomach Division in 1980.
Following Caterpillar's acquisition of Solar Division and Turbomach assets from International Harvester on May 31, 1981, Solar Turbines Incorporated became a Caterpillar subsidiary. The Turbomach Division was later sold to Sundstrand Corporation in 1985.
Prudden-San Diego Airplane Company
Solar Turbines traces its beginnings to the Prudden–San Diego Airplane Company, founded in 1927 by George Prudden along with seven San Diego entrepreneurs. Due to internal management disputes, Prudden departed the company in November 1928.
First product—a trimotor aircraft
In March 1929, reflecting San Diego’s sunny environment, the company was renamed Solar Aircraft Company. Its main offering was an all-metal passenger trimotor aircraft equipped with Siemens & Halske radial engines. However, sales were severely impacted by the Great Depression, resulting in only three units produced.
Transition to aircraft component manufacturing
After the commercial failure of the trimotor airplane, Solar Aircraft shifted focus to producing specialized components for other manufacturers, notably stainless steel exhaust manifolds capable of withstanding high temperatures. The company was reincorporated as Solar Aircraft Company in 1937 and expanded its workforce to 229 employees by 1939. Military contracts during World War II accelerated growth dramatically; staff numbers soared to 5,000 while manufacturing more than 300,000 exhaust manifolds for U.S. military aircraft.
Following the war, demand declined, prompting diversification into stainless steel consumer goods such as caskets, frying pans, bulk milk containers, and redwood furniture. Capitalizing on its expertise in durable high-temperature materials, Solar secured contracts for jet engine parts and developed turbine engines for U.S. military applications including auxiliary power units, aircraft fuselages, and rocket engine components for guided missiles. The company continued expanding until its acquisition by International Harvester in early 1960, becoming the Solar Division of International Harvester in 1963.
Advancing proficiency in gas turbine technology
Solar Aircraft Company's specialization in high-temperature metallurgy facilitated the manufacture of parts for early American jet engines, such as the General Electric I-40, along with fulfilling a US Navy contract to produce an afterburner for the Westinghouse J34. Additional contracts included components for the Allison J33, Allison J35, Avro Canada Orenda, and Bristol Olympus engines. Engineer Wendell Reed invented the pneumatic microjet controller for engines, which earned him the Wright Brothers Medal in 1955; this device became a standard feature in gas turbines, afterburners, and ramjets.
Identifying turbines as key future power sources, company president Edmund Price led a team under Paul Pitt in 1946 to create an axial-flow turbine intended as an auxiliary power unit (APU) for the US Army Air Force's Convair B-36 bomber. Although the Army canceled this project, Solar secured a 1947 contract from the US Navy to develop a 250 kW emergency power system for naval vessels. The T-400, which first operated in 1949, was deployed on minesweepers and landing craft. Solar also provided APUs for the initial 632 KC-135A tankers operated by the Strategic Air Command.
In 1947, Leon Wosika and Eric Balje engineered a compact centrifugal-flow turbine system initially named MPM-45 and later marketed as "Mars." The Navy designated this unit as T41 and utilized it to drive portable firefighting pumps aboard ships. By 1956, Solar introduced a larger model called "Titan" (T62) designed to power the Gyrodyne XRON-1 helicopter; following cancellation of that helicopter program, Solar repurposed it as an auxiliary power unit with production beginning in 1962. The Navy also requested a free-turbine variant (T66), which ultimately was never fielded. Additional Mars derivatives included models named Spartan and Gemini.
During the late 1950s, Solar developed the axial-flow "Saturn," an engine designed for a high-speed Navy vessel that entered production in 1960. Targeted at industrial customers requiring approximately , the Saturn became the most widely adopted industrial gas turbine worldwide, with roughly 4,800 units installed across 80 countries. It continues to be produced today with upgraded versions available. To improve market competitiveness, Solar offered complete systems integrating the Saturn with gas compressors, pump drives, and generator sets—particularly favored by natural gas pipeline operators.
Solar Division under International Harvester
International Harvester acquired Solar Aircraft Company in early 1960 and reorganized it as the Solar Division in 1963. Over the following decade, this division broadened its engine portfolio with products such as the Centaur, first launched in 1968 with an output of 2,700 hp; modern iterations now deliver up to 4,700 hp. By 1973, Solar had shifted its primary focus away from aviation toward industrial gas turbines.
Reorganization of product lines
In 1975, International Harvester separated Solar's radial engine production into a newly formed Radial Engine Group, which was renamed Turbomach Division in 1980. The Solar Division introduced a larger Centaur derivative—the Mars engine—in 1977, initially rated at 10,600 hp and currently offered as the Mars 90 (13,220 hp) and Mars 100 (16,000 hp) models.
Subsidiary Fully Owned by Caterpillar Inc.
On May 31, 1981, Caterpillar Tractor Co. acquired the Solar and Turbomach Divisions from International Harvester, establishing Solar Turbines Incorporated as a wholly owned subsidiary. Caterpillar tasked Solar Turbines with the development and production of the Model 5600 gas turbine, initially derived from Boeing’s 551/553 series before Boeing withdrew from the gas turbine sector in 1966.
Sale of Turbomach Division
In 1985, Caterpillar divested its Turbomach Division, selling it to Sundstrand Corporation (currently Collins Aerospace), thereby withdrawing from the centrifugal gas turbine market.
Advances in Product Development During the 1980s and 1990s
Throughout the 1980s and 1990s, Solar Turbines consistently enhanced its axial-flow industrial gas engines. A major milestone occurred in 1997 with the launch of the Titan 130, delivering 19,500 horsepower—representing a substantial improvement over previous models; today’s Titan 250 reaches up to 30,000 horsepower. The company also focused on increasing fuel efficiency and lowering emissions. In 1992, it introduced the SoLoNOx lean-burn technology aimed at reducing nitrogen oxide emissions; this system has been retrofitted to more than 2,000 turbines and is now standard on newer models. Partnerships with the U.S. Department of Energy fostered further innovation, such as ceramic hot-section components for the Centaur 50 and recuperator technology for Mercury 50 turbines.
Acquisition of Turbomach S.A.
In 2004, Caterpillar broadened its international footprint by acquiring Turbomach S.A., a Swiss firm specializing in packaging industrial turbines from manufacturers including Solar, Rolls-Royce, and Trent.
Present-Day Product Range
Solar Turbines Incorporated offers an extensive lineup of turbines, including the Saturn, Centaur, Mercury, Taurus, Mars, and Titan series along with a variety of accessories. The company has sold over 15,000 gas turbine units worldwide, accumulating more than two billion operational hours—highlighting its strong market presence and sustained growth.
Product Specifications
Titan 350 38 8,495 1800 -- 1 (annular) 237.5 910| Electrical Generation Specifications | ||||||||
|---|---|---|---|---|---|---|---|---|
| Model | POWER RATING ISO Base Load (MW) | HEAT RATE Lower Heating Value (Btu/kWhe) | POWER SHAFT SPEED (RPM) | PRESSURE RATIO | NUMBER OF COMBUSTORS | Exhaust Flow (lb/sec) | Exhaust Temp (°F) | Year Entered Production |
| Saturn 20 | 1.2 | 14,810 | 1800 | 6.7 | 1 (annular) | 14.3 | 945 | 1960 |
| Centaur 40 | 3.5 | 12,910 | 1800 | 10.1 | 1 (annular) | 41.6 | 830 | 1968 |
| Centaur 50 | 4.6 | 11,630 | 1800 | 10.6 | 1 (annular) | 41.8 | 950 | |
| Mercury 50 | 4.6 | 8,865 | 1800 | 9.9 | 1 (annular) | 39 | 690 | 1998 |
| Taurus 60/MPU* | 5.7 | 10,830 | 1800 | 9.9 | 1 (annular) | 48 | 950 | |
| Taurus 65 | 6.5 | 10,295 | 1800 | 15 | 1 (annular) | 47.1 | 1000 | |
| Taurus 70 | 8.2 | 9,920 | 1800 | 17.6 | 1 (annular) | 59.2 | 970 | 1995 |
| Mars 100 | 11.4 | 10,365 | 1800 | 17.7 | 1 (annular) | 93.1 | 905 | |
| Titan 130/MPU* | 16.5 | 9,605 | 1800 | 17.1 | 1 (annular) | 124 | 915 | |
| Titan 250 | 23.1 | 8,775 | 1800 | 24.4 | 1 (annular) | 153.9 | 865
2008 | |
- MPU: Mobile Power Unit (trailer-mounted). SMT denotes Solar Mobile Turbomachinery engineered for rapid deployment without crane assistance.
| Mechanical Drive Specifications | |||||||
|---|---|---|---|---|---|---|---|
| Model | POWER RATING ISO Base Load (hp) | HEAT RATE Lower Heating Value (Btu/hp-hr) | POWER SHAFT SPEED (RPM) | PRESSURE RATIO | NUMBER OF COMBUSTORS | Exhaust Flow (kg/sec) | Exhaust Temp (°C) |
The specifications are based on natural gas fuel with no installation-related losses; these offerings highlight Solar Turbines’ strengths in delivering efficient and versatile solutions for both power generation and mechanical drive applications.
Bibliography
- 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
- Companies of the United States by year of establishment