A Method for Reducing Jet Engine Thermal Signature

The protection of aircraft against shoulder fired heat seeking missiles is of growing concern in the aviation community. This paper presents a simple method for shielding the infrared signature of a jet engine from heat seeking missiles, by using water injection. The experimental results presented herein were obtained using a small (1 kN thrust) turbojet. Water was first injected at a mass flow rate of 13% of the mass flow rate of exhaust gases, reducing the temperature and producing some shielding. Water was then injected through a manifold at a mass flow rate of 118% of the mass flow rate of exhaust gases, producing a substantial reduction in temperature and complete shielding of the infrared signature. Results are presented in the form of thermocouple data and thermal images from the experiments. Graduate Research Assistant, currently Aerospace Engineer, Air Force Research Laboratory, Kirtland AFB, NM 87117-5776 Associate Professor