Electromagnetic launch assistance for space vehicles

by reducing the cost of launching space vehicles, the US National Aeronautics and Space Administration sponsored an industry/university research project to explore the application of electromagnetic forces. Here, the technical issues involved are examined, the initial achievements reported and further improvements suggested. If the initial launch phase of a space vehicle is horizontal instead of vertical, it is possible to use electromagnetic forces to supplement the rocket thrust, with consequent saving of rocket fuel. The short time of the horizontal launch phase (10-20 s) enables induction levitation to be used in combination with a compact form of a linear induction motor. The performance, dynamic characteristics and scaling laws of this system are examined. Induction levitation is simple and effective, but it has an oscillatory response to force or torque disturbances, and it is unsuitable for very large space vehicles. These problems can be overcome with magnetic suspension using controlled DC electromagnets. Although the energy required for electromagnetic launch assistance is small, the electrical power demand is very high, necessitating some form of local energy storage.