Roy Marquardt was an aeronautical engineering graduate from Caltech who had worked at Northrop during World War II on the B-35 flying-wing bomber project. While working on problems cooling the engines, which were buried in the wings, he found that the heat generated by the engines produced useful thrust. This started his interest in the ramjet principle, and in November 1944 he started Marquardt Aircraft in Venice, California in order to develop and sell ramjet engines.
Marquardt's first products were wind tunnels, but by the end of their first year they had delivered an experimental 20 inch (0.51 m) ramjet to the US Navy for testing. The USAAF purchased two of the same design early in 1946, and fitted them to the wingtips of a P-51 Mustang fighter for in-flight testing. By this time the Navy had fitted theirs to a F7F Tigercat and started flight tests in late 1946. Later Navy tests fitted the same engine to a P-83 and F-82 Twin Mustang.
In 1947 Martin built the Gorgon IV missile testbed, powered by the 20" engine. Four Gorgon flights with the new engines were made that year at the subsonic speed of Mach 0.85 at 10,000 feet (3,000 m) altitude, and in 1948 a newer engine pushed the speeds to Mach 0.9. Martin eventually won a contract to convert the Gorgon design into a target drone, becoming the KDM-1 Plover, and delivering Marquardt a contract for 600 more 20" engines.
In 1948 the newly created US Air Force took delivery of several larger 30" (0.76 m) designs and fitted them to the wingtips of a P-80 Shooting Star, which became the first manned aircraft to be powered by ramjets alone. An even larger 48" (1.22 m) design was built as a booster for a new interceptor design, but not put into production.
The same year the company also started conversion of the existing engine designs to operate at supersonic speeds. This requires the airflow to be efficiently slowed to subsonic speeds for combustion, which is accomplished with a series of shock waves created by a carefully designed inlet. Starting with the existing 20" design from 1947, work progressed until the new engine was ready for use in 1949.
By this point the company had outgrown its Venice plant, but had no money to fund a larger factory. Marquardt then sold a controlling interest in the company to General Tire and Rubber Company in 1949, and used the funds to move to a new site in Van Nuys, the former Timm Aircraft factories. However the purchase wasn't a happy one for General Tire due to management differences, after making "only" 25% return in one year, they agreed to sell their share of the company to another investor. Eventually such an investor was found, and General Tire sold their stake to Laurance Rockefeller in 1950 for $250,000.
By this point Marquardt was truly hitting its stride. In the early 1950s supersonic cruise missile and target drone projects for various roles were quite common. Many of them were designs to be shot down as target drones, or simply crash or explode at the end of their mission, so simplicity and low cost was as important as high-speed performance. This made the ramjet ideally suited to these roles. By 1952 Marquardt was involved in a number of projects, including the Navy's Rigel missile, the Air Force's BOMARC anti-aircraft missile. To test the new engine design for the BOMARC, the X-7 high-speed radio control test aircraft was also built.
Over the next few years the X-7 missile would break record after record, and led the Air Force to award Marquardt with the contract for the BOMARC missile engines. Originally they had intended to award the production to a larger company with better manufacturing abilities, as the Van Nuys plant wouldn't be able to build the 1,500 engines quickly enough. Instead, the Air Force and Marquardt collaborated on a new plant on the shores of Great Salt Lake just outside of Ogden, Utah. The plant was officially opened in June 1957, and delivered their first engines a month ahead of schedule. By 1958 the engine was in full production, leading to an additional engine contract from the Air Force for an equally large run of a more advanced version for the IM-99B "Super BOMARC". Meanwhile the X-7 continued to break records, eventually setting the speed record for air-breathing vehicles at Mach 4.31.
By 1959 the company had sales of $70 million, and had purchased several smaller aerospace firms. One of these purchases, Power Systems, led to a number of designs for small rocket motors used as positioning thrusters. This would eventually become one of Marquardt biggest product lines in the 1960s. Meanwhile the main Van Nuys plant was also involved in research into new systems, include a nuclear-powered ramjet for Project Pluto and a liquid air cycle engine (LACE) for the Air Force's Aerospaceplane efforts. Another new product line started with the introduction of their first ram-air turbine, small air-powered generators for providing aircraft with electrical power if the main engine failed. With this diversification came a change in name, to Marquardt Corporation.
By 1970 Marquardt was known primarily as "the" company for small rocket engines and thrusters. Practically all US space vehicles and satellites used their designs, eventually including a major win for the Space Shuttle program.
The market for ramjet engines had largely disappeared by this point due to increased performance from normal jet engines, but Marquardt continued low-level development on advanced designs. One system, developed in partnership with Morton Thiokol, placed a solid fuel booster inside the ramjet core. When the solid fuel burned out the ramjet would ignite as normal. The idea was to combine the booster and ramjet into a single airframe, thereby reducing cost, size, and range safety requirements, as nothing would be "dropped off" in flight.
In 1983 the company was purchased by the ISC Defense and Space Group International Signal and Control. Unknown at the time, ISC was heavily involved in illegal arms dealing, selling advanced US weaponry to anyone with enough money. Through the 1980s ISC sold cluster bombs to Iraq, 1,500 laser guided bombs to Iraq, and electronics for nuclear development to South Africa, all with the full knowledge of the CIA.
In 1987 ISC was purchased by Scotland-based Ferranti, but soon after the merger Ferranti started to realize that ISC had been "cooking the books". Eventually Ferranti was dragged down by the weight of the $700 million they paid for a company that had little real sales, and had existed primarily on illegal arms dealings. Ferranti declared bankruptcy in 1991 and sued ISC's CEO, James Guerin. Guerin claimed he was doing this for the CIA, but the US government disavowed this. He was eventually convicted and sentenced to 15 years for defrauding Ferranti of $1.1 billion, money laundering and illegal arms exports.
As a result of all of this, Marquardt was split in two. The Marquardt Jet Laboratory, building rocket thrusters, was sold to Kaiser Aerospace, while the Marquardt Manufacturing Company disappeared. Kaiser reportedly picked up Marquardt for a mere $1 million, with about $50 million in outstanding Space Shuttle contracts. Kaiser eventually closed the Van Nuys plant in 2001.