Very-High-Altitude Propulsion System (VHAPS)

There is interest in an unmanned aircraft that can be deployed to a target via unconventional means and operate at very high altitudes for very long periods of time. These aircraft are envisioned to be stored in a sealed container for many months at a time, possibly folded up, stowed or deflated in a fashion more similar to a zodiac marine craft than an aircraft. A key technology required for such an aircraft is an engine capable of providing the required thrust at altitude and also meeting stringent weight and volume requirements. Deployment options may mean that traditional multistage-compressor jet or internal combustion engines are not appropriate for the aircraft. Alternative, non-traditional options must be investigated. Aurora Flight Sciences proposes to address the need for compact, highly efficient aircraft propulsion at very high altitudes by analyzing the engineering of the Mini-Sniffer engine and looking for ways to improve upon it. The Mini-Sniffer is an attractive starting point for research into very-high-altitude aircraft propulsion because of its relative simplicity, leading to reduced system mass and volume. In the 35 years since the Mini-Sniffer work was done, there have been technology advances that might increase the engine thermal efficiency without impacting the attractive simplicity of the system, in areas such as propellant, material and mechanical improvements.