The design of the RS-84 engine includes a creative arrangement of a small part of the manifold - the flow of fuel in the pipe funnel - placed along the combustion chamber and the engine nozzle. The manifold weaves kerosene fuel to flow to the coolant pipe and collects the heat pipe wall after the fuel is cooled. There are gaps between manifolds, so kerosene will not be heated to exceed the coking limit. Some RS-84 flow pipes will also inject a small amount of kerosene directly into the thrust chamber, forming a layer of fuel film along the thrust chamber wall, which helps to reduce the temperature of the thrust chamber wall. This arrangement reduces the temperature of the combustion chamber wall and shortens the time of fuel exposure to high temperature.

Danny Davis, assistant manager of Marshall RS-84, said: "Developing a safe, reliable and reusable kerosene engine has become the primary task of the Space Launch Initiative Propulsion Office." "The space launch plan has determined that kerosene has a significant advantage in the concept of reusable launch vehicles. Our RS-84 design team is answering questions about reusability and manifold arrangement to make the concept of kerosene possible. In addition, our oxygen-enriched staged combustion concept uses cleaner and heated oxygen to drive the turbine to avoid the problem of kerosene rich gas in the past."

Another method adopted by the TR107 engine team is to cool the main combustion chamber in pipes and use materials that do not catalyze or interact with kerosene to form coking. Add pipes or gaskets in the combustion chamber to separate the fuel from the combustion chamber wall, so as to cool the combustion chamber in a controlled way, while keeping the temperature of kerosene low.

"The potential benefits of duct cooling can certainly solve the coking problem," said Rick Ryan, assistant manager of Marshall TR107. "In addition, duct cooling has the potential to greatly simplify rocket engines. By eliminating the regenerative cooling circuit, you have eliminated many large manifolds and related pipes. This in turn has eliminated several potential failure modes that affect engine reliability."

Although the concept of pipe cooling is very different from the concept of large rocket engine nozzle in the past, early analysis shows great potential. Like RS-84 engine, TR107 engine uses cleaner and cooler oxygen-enriched propellant to help reduce soot accumulation on turbine blades.

Kerosene is a fuel with relatively low maintenance costs, which is convenient for ground operation and reduces operating costs. In addition, because it is not a cryogenic or extremely cold fuel like hydrogen, the propulsion system does not need to insulate the propulsion-related pipes, valves, pipelines and actuators, thus saving weight and cost.

A comparison between the new kerosene engine and the F-1 engine has not changed: just as in the early days of Apollo, NASA engineers and industry partners are writing a new chapter in space propulsion.

"This is an exciting moment for NASA," Lairs said

The space launch plan continues to promote the development of technologies needed for the next generation of space launch. The Marshall Center manages the space launch program for NASA's Aerospace Technology Office.