by Mary Reveley
Journal entry for June 2, 1999
Money always gets people's attention. My job is to determine how much money is needed for new and unconventional aeropropulsion technology concepts on engine/aircraft systems. The results of which are used to influence the NASA technology investment and decision making processes.
Today I was given a new assignment: determine/find/development a new cost estimating method for estimating the costs associated with a reusable rocket based combined cycle launch vehicle.
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. . Air-breathing propulsion: the piston engine, turbojet, ramjet- all depend on the combustion of fuel with air, where the air is obtained directly from the atmosphere. 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. From a qualitative technical standpoint, a case can be made for launch vehicles that would be reused many time's without refurbishment or re-assembly. This implies a highly reusable, single-stage-to-orbit launch vehicle.
It currently costs on the order of ten to twenty thousand dollars per pound to launch payload into orbit. The future of the space program is hindered by this high cost and associated low reliability.
The rocket-based combined cycle engine combines the high thrust of a rocket, which is needed for lift-off, with the ram jet engine, which can be exploited after an initial acceleration to sufficient velocity. Upon reaching an appropriate maximum ramjet Mach number, the rocket is re-ignited for the final acceleration to orbit.
Getting back to my problem for the day (and the rest of the month!) is how do I estimate the costs of developing, manufacturing and using this rocket-based combined cycle engine? Welcome to NASA where the unusual is usual! I will spend time researching any work already done by fellow workers, search for information at our library, and contact the Air Force since they have done cost estimating work on advanced concepts. I will also have to learn a cost estimating program used widely by government and industry called Price-H which is a hardware cost estimating computer model.
Today I have been reviewing how the following engines work: the rocket-based combined cycle, the scram jet and the ram jet.