Aircraft and missiles capable of rapid global strike and reconnaissance must fly at hypersonic speeds to achieve their performance goals. Future air-breathing hypersonic aircraft and missiles are expected to be powered by supersonic combustion ramjet (scramjet) engines. Unfortunately, scramjet engines only operate well at high speed and must be boosted there by a separate system. In the near term, this capability will probably be realized first in scramjet-powered missiles boosted to high speed with solid rocket motors. Ignition of the scramjet combustor at the end of the boost phase can be difficult to achieve due to the relatively low air pressures, temperatures, and residence times in the combustor as well as cold fuel and engine hardware. In a Phase I project Reaction Systems investigated an innovative new approach utilizing thermally stable catalysts or high temperature catalysts to decompose N2O, resulting in a very hot N2/O2 mixture that can be used to promote fuel ignition. Our approach incorporates the use of wall-mounted catalysts for increased heat flux. The use of a catalyst can significantly decrease ignition time delay and can also be combined with the liquid fuel injection system to achieve good fuel atomization, penetration, and mixing into the engine air flow.
The development of new, robust, lightweight life support systems is currently a crucial need for NASA in order to continue making advances in space exploration, particularly in the development of Lunar outposts and the eventual exploration of Mars. Two functions that are critical to life support systems are the control of carbon dioxide (CO2) and moisture (H2O) during extra vehicular activities (EVA). The current system relies on a sorbent bed to control CO2. Thus in order to increase mission times, the bed must be enlarged or regenerated during the EVA. Both of these choices results in increased size and weight of the portable life support system and also increased chance of failure.
A much simpler approach would be to use a membrane system to separate CO2 from the O2 environment in the space suit. An effective membrane separation process would have several advantages over competing technologies: first it would be a continuous system with no theoretical limit on the quantity of CO2 removed, second it would require no consumables or hardware for switching beds and regeneration, third, it is a simple system with low potential for failure and low energy requirements, and fourth, it will not intentionally vent O2 to space. An even better solution would be the development of a single membrane system that controlled both CO2 and H2O, thereby eliminating the hardware required to condense moisture. Thus, Reaction Systems is developing a liquid membrane that utilizes a low vapor pressure liquid which also contains reagents to facilitate the selectivity separation of CO2 and H2O from O2.
The surfaces of liquid fueled rocket engine thrust chambers, throats, and nozzles are exposed to high pressure combustion products at temperatures up to 6000°F requiring the copper alloy surfaces in these areas to be actively cooled. Regenerative cooling is widely used for liquid fueled rocket engines causing the fuel to reach temperatures where carbon deposits (coke) form on the heat exchanger surfaces. Coke has a much lower thermal conductivity than copper and thicknesses of only several millionths of an inch can cause the wall temperatures to reach levels where they will fail. Moreover, the intention to reuse launch vehicles increases the likelihood that over the course of multiple missions, dangerous levels of coke will be reached. Therefore, there is a need to develop a method to characterize the layer thickness so that engine lifetimes and service intervals can be predicted. Unfortunately, the small and complex channel geometry and the very low levels of coke present make this a difficult and challenging problem. Reaction Systems has identified an approach than can rapidly and accurately map the coke deposited in all flow channels in a single analysis. The method is safe and easy to use and has no potential to cause damage to the engine or leave parts behind in the channels. In addition while carrying out the mapping process our method will remove all of the coke deposits in the heat exchanger, eliminating the need to develop a separate coke mitigation technology.
The development of weapons that can travel at hypersonic speeds is becoming a high priority to the US Air Force. A key technology needed for the continued development of these propulsion systems is the ability to cool the combustor by flowing fuel through channels machined in the walls. Currently, the cooling capacity of kerosene-based fuels is relatively low even with endothermic cracking reactions, and this limits the Mach number that can be achieved. Moreover, increasing the fuel cooling capacity by raising the fuel flow is not practical because the additional fuel would over-fuel the combustor or have to be dumped overboard. Likewise, allowing the fuel to reach higher temperatures is not feasible because coke formation could lead to heat exchanger failure. Therefore, there is a strong need to develop new endothermic fuels and custom heat exchanger/reactors that can deliver substantially higher heat sink capacities. Under a very successful Phase I project with the US Air Force, Reaction Systems has identified a fuel and catalyst combination that can undergo a chemical reaction that produces much higher endotherms than currently available with kerosene-based fuels. In addition, Reaction Systems has just been notified of a Phase II award to continue development of the fuel/catalyst system and design a custom heat exchanger/reactor for use in a hypersonic engine.