First Stage of a Highly Reliable Reusable Launch System

Abstract

Electromagnetic launch assist has the potential to provide a highly reliable reusable first stage to a space access system infrastructure at a lower overall cost. This paper explores the benefits of a smaller system that adds the advantages of a high specific impulse air-breathing stage and supersonic launch speeds. The method of virtual specific impulse is introduced as a tool to emphasize the gains afforded by launch assist. Analysis shows launch assist can provide a 278-s virtual specific impulse for a first-stage solid rocket. Additional trajectory analysis demonstrates that a system composed of a launch-assisted first-stage ramjet plus a bipropellant second stage can provide a 48-percent gross lift-off weight reduction versus an all-rocket system. The combination of high-speed linear induction motors and ramjets is identified, as the enabling technologies and benchtop prototypes are investigated. The high-speed response of a standard 60 Hz linear induction motor was tested with a pulse width modulated variable frequency drive to 150 Hz using a 10-lb load, achieving 150 mph. A 300-Hz stator-compensated linear induction motor was constructed and static-tested to 1900 lbf average. A matching ramjet design was developed for use on the 300-Hz linear induction motor.

A Lunar Electromagnetic Launch System for In Situ Resource Utilization

“…Another system, 5.5 m (18 ft) long utilizing 300-Hz DSLIM's, was built to test speeds of approximately 322 km/hr (200 mph) (Fig. 1); static load-cell testing was performed, with peak thrust measured at 15.57 N (3,500 lb-t) [11]. With these demonstrations, a Technology Readiness Level (TRL) [12] of5 has been achieved.…”