Teledyne CAE J402 The Teledyne CAE J402 is a small turbojet engine designed to power unmanned air vehicles such as missiles and target drones . Developed in the 1970s for the Harpoon anti - ship missile , the J402 was the first jet engine to be designed as a " wooden round " , meaning that the engine had to be able to sit for long periods without maintenance or inspection and work right away . Several variants of the engine have been developed , some of which power unmanned aerial target drones . Development and design . The J402 engine was designed for the Harpoon missile from the beginning . Its size and weight were dictated by the already - planned missile ( just over 12 inches ( 30 cm ) in diameter , about 100 lb ( 45 kg ) in weight ) . The engine also had to be designed to be inexpensive ; the military wanted to produce and store large quantities of the missile . To meet these requirements , Teledyne aerodynamically scaled their J69 - T - 406 turbojet to just 32 % air capacity . This brought thrust and size down to the desired levels . The J402 - CA - 400 , the original Harpoon variant , was qualified in 1974 and proved to be extremely reliable , failing only twice in 131 flights through mid 1980 . The J402 - powered Harpoon had an excellent service record , including sinking two Libyan warships during the 1986 Gulf of Sidra Incident . Through 1988 , the oldest J402 engine fired in a Harpoon was over eleven years old , exceeding the original five year " wooden round " requirement . The J402 - CA - 400 was a single shaft engine , with one axial compressor stage and one centrifugal compressor stage . The compressed air was combusted in an annular combustor , and then passed through a single high pressure turbine stage before being exhausted . Because the engine was designed for a one - time use missile , its service life was only one hour . The primary challenge of the " wooden round " requirement was to design the engine to be as reliable as possible . To that end , significant efforts were made to reduce the number of individual parts throughout the engine . For example , the rotor system of the J402 had 16 parts , while the J69 ( the parent engine ) had 149 parts for the same system . Another simplifying measure was to eliminate the standard gearbox . All the engine accessories , like the fuel pump and electrical alternator , ran directly off the rotor shaft . Engine starting was another reliability - critical function of the engine , and to accomplish that requirement , the J402 utilizes pyrotechnic cartridges to start the engine . Finally , the engine was among the first to feature a fully electronic analog fuel controller . Soon after development of the - 400 variant for the Harpoon began , Teledyne began work on a new variant , the J402 - CA - 700 for the new MQM - 107 Streaker aerial target drone . These target drones were not " one - time - use " vehicles like the Harpoon missiles were , so the lifetime of the engine had to be extended from one hour to 15 hours . To accomplish this , the turbine temperature was reduced , as well as the rotational speeds . A new starter system was included to give the engine the ability to restart . The result was an engine that was slightly less powerful , at 640 lbf ( 2 . 8 kN ) versus the - 400 ' s 660 lbf ( 2 . 9 kN ) , but had the required service life . An additional variant , the J402 - CA - 702 , was developed internally by the company . This variant added an additional axial compressor stage ( bringing the total to two axial stages ) , which increased the engine length by only 4 in ( 10 cm ) , yet increased the thrust to 970 lbf ( 4 . 3 kN ) . The engine was later selected to power the MQM - 107D , an improved version of the target drone . The addition of additional compressor stage increased the pressure ratio and overall airflow through the engine , and necessitated the development of a new turbine section . Teledyne designed and tested the new two stage axial compressor early in the J402 ' s life ( mid 1970s ) , but did not work on the new turbine ( and subsequently the - 702 variant of the engine ) until nearly a decade later in the mid - 1980s . The resulting engine was 45 % more power than the - 400 / - 700 variants , yet also had a 24 % lower thrust specific fuel consumption ( SFC ) . The most recent variant of the J402 is the J402 - CA - 100 , developed for the AGM - 158 JASSM cruise missile . This derivative , like the - 700 , is based on the original - 400 variant . The primary changes are an aerodynamically refined axial compressor and turbine section , resulting in a more fuel efficient engine at the same thrust levels as the - 400 .