Deriving the Generalized Rocket Kinetic Power Equations and Associated Propulsion Indexes

• Published in: JSME International Journal Series B Fluids and Thermal Engineering Vol. 42; no. 1; pp. 127 - 136
• Main Authors: LEE, Hsing-Juin, LEE, Hsing-Wei
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Society of Mechanical Engineers 1999; Japan Society of Mechanical Engineers; Japan Science and Technology Agency
• Subjects: Applied sciences; Efficiency Equations; Energy efficiency; Exact sciences and technology; Generalized Power; Kinetic energy; Mathematical models; Other techniques and industries; Overall Efficiencies; Propulsive; Rocket Kinetic Powers; Space application; Fuse; Theoretical study; Propulsion; Kinetic energy; Performance
• ISSN: 1340-8054; 1347-5371
• DOI: 10.1299/jsmeb.42.127

In this study, firstly we endeavor to prescribe logic definitions and reasoning process for obtaining correct rocket power and relevant efficiency equations. With the Lagrangian Reynolds transport approach, we also rigorously derive these highly generalized equations for rocket total kinetic power, thrust power and related propulsive, thermal, and overall efficiencies. They involve a few more physical effects including rocket acceleration, relative flow velocity / steadiness, outlet pressure, and gravity, thus open an original route for improving rocket propulsion analysis / design. Incidentally, it is interesting to note that under some conditions, a rocket in flight may retain less kinetic energy due to ejecting more kinetic energy of burning propellant per second than the thrust power acquired. Also, the derived correct rocket total kinetic power equations are quite reasonable in that all the velocities involved are of relative nature, thus invariant with respect to different observers and shielding the possibility of violating energy conservation law.