M.Sc Thesis

M.Sc StudentPeker Avi
SubjectFeasibility Study of a Medium/Long Range Ramjet Cruise
DepartmentDepartment of Aerospace Engineering
Supervisors PROF. Benveniste Natan
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Most cruise missiles operate at cruising altitudes that are two orders of magnitude lower than those of long-range ballistic missiles. This feature is one of the main reasons for the high interest in developing new systems that travel at high speeds and low altitudes, thus increasing detection and interception times for most common interception systems, improving their survivability.

The ramjet engine is an air-breathing engine that operates without any moving parts at high Mach numbers. Furthermore, the ramjet engine is known for its high specific impulse, a performance parameter that represents the capable operational range.

This research conducts a feasibility study of a cruise missile powered by a ramjet engine. The mission profile chosen is a surface-to-surface mission with a 500 kg payload and a 1500 km operation range.

The feasibility question is answered in two parts that are inherently coupled. They combine the external ballistics and flight performance and the internal ballistics (propulsion unit).

The first part involves the missile structure and aerodynamic properties, aerodynamic heating and its effect on the design parameters, and a 3DOF trajectory simulation of the missile. The internal ballistics study includes the solid booster and the ramjet engine performance analysis, where thrust, specific impulse and flow mass rates are derived as a function of altitude, flight velocity and time.

Aerodynamic optimization was conducted to satisfy the design criterion that was developed for maximum range. The aerodynamic coefficients were calculated using a component build-up method, MissileDatcom07. Based on the aerodynamic characteristics, estimations of the flight performance were made, such as required hinge moments and missile maneuver accelerations capability.

The sizing process was based on empirical correlations derived for similar missiles, in addition to the constraints defined by the specific mission, such as total weight and missile length.

An energetic performance analysis was conducted for both the solid rocket booster and the ramjet engine in order to meet the mission requirements. Thermochemical calculations, determined the propellant composition for highest performance. A rod-and-tube propellant grain design was chosen and validated with consideration to erosive burning. The ramjet engine cycle was calculated and a suitable engine configuration was obtained.  

The aerodynamic heating was taken into account by solving the heat transfer equation for areas on the missile far away from stagnation conditions using lumped analysis assumption and Reynolds analogy. The heat flux and wall temperature of the missile were calculated along the trajectory, in order to determine the thermal protection system or other materials selection. Since the wall temperature exceeds 200 0C, the use of traditional aluminum alloys is not feasible for supersonic flight at low altitudes. Different design approaches within the "hot" and "cold" structures were reviewed to address the aerodynamic heating challenge.

Finally, a 3DOF trajectory simulation was carried out and presents the various performance parameters along the missile flight. Moreover, in the trajectory simulation, an applicable "bending" law of the trajectory that utilizes thrust vector control and control surfaces steering was tested and implemented successfully, ensuring that all pre-defined mission requirements were kept.