Mary Reveley is an Aerospace engineer at NASA Glenn research Center where she predicts the costs and benefits of implementing new propulsion and aviation technologies. The results of which are used to influence the NASA technology investment and decision making processes. An active area of hypersonic propulsion research at Glenn is the application of air-breathing propulsion to launch vehicles in order to reduce the cost of space access. . In contrast, the rocket engine carries both its fuel and oxidizer and is completely independent of the atmosphere for its combustion. Thus, the rocket can operate in the vacuum of space, where obviously the air-breathing engines cannot.
Space access is costly for a number of economic and technical reasons.
A rocket is an expendable launch vehicle used for only one flight. The Space Shuttle has a number of expendable components such as the external tank. Others, such as the main engines must be refurbished after every flight. The various components must then be reassembled prior to the next flight. This makes the shuttle one of the most expensive means of putting payload into orbit.