An In-Line Reusable Launch Vehicle Concept Using Confined Load-Bearing Frozen Propellants

This paper addresses the problem of the high cost of space vehicles evidenced by actual program lifetime-averaged costs of ~$1.5B per flight (Space Shuttle). Launch vehicles are complex and require high performance engineering design driven significantly by vehicle mass; a large fraction being propellant mass. The work described here investigates a novel concept towards more affordable launch vehicles and is primarily theoretical along with development of computational analyses. The concept involves the storage of propellant as a frozen monolithic mass, phase change to fluid during flight and fluid delivery to a rocket engine; i.e., solid-storage/fluid-delivery (SSFD). The approach is applicable to all propulsion systems (bipropellant, monopropellant, chemical, electric, nuclear, solar, beamed) and a variety of missions. We focus on a launch mission from Earth-surface to Earth-orbit and we focus on chemical bi-propellant propulsion in this paper. A reduction of operational cost is expected for such a vehicle concept from: increased functionality per unit mass, reduced complexity, and engine reusability. Frozen propellants can serve load-bearing/heat-sink roles prior to consumption. Innovative storage and delivery concepts reduce complexity and offer engine reusability. Improvements can be realized with existing rocket engine technology. Further improvements can be realized with development of a novel rocket engine. These will be discussed. We investigate feasibility and show results in terms of design: balance of heat rate necessary for melting with required propellant consumption for thrust and mechanical load-bearing capability with frozen propellant material yield strength and ultimate strength. We also investigate overall vehicle operation and show results in terms of propulsion performance, discuss costs, discuss technical challenges that remain and future research direction.