There are 2 StratRaft versions (V1 & V2), with similar lenticular (L form) based Luffship arrangements, designed in late 2002 for long endurance operation at high altitude. They either may be manned or remotely piloted and autonomously operated. Both versions were arranged to serve as geo-stationary platforms in the stratosphere at say 20 km altitude, be able to orientate or face any direction without translation, carry telecommunications and other equipment, plus have potential capability as aerial carriers for launch and recovery of UAVs (drones) or other small aircraft.
They would be very big aircraft in the stratosphere due to expansion of the displacement gas – not a problem with V1’s lower aerostat variable geometry method or V2’s simple 100% ballonet, enabling almost any height to be accessed and maintained. However, because of V1’s variable geometry method, it can be much smaller at ground level (easier to manage).
They in fact both may be configured to operate at any altitude in the atmosphere. At a small size they therefore could work as manned or unmanned geostationary platforms at a low altitude (say 150 to 300 m – 500 to 1000 ft) remaining on station all day or as long as the crew can manage.
Compared with classic airships designed for such purposes, both StratRaft versions are more simply configured, adopting balloon (instead of airship) technology in a cost effective way. They also remain upright in a natural way throughout flight, as balloons do; difficult for UD types to achieve due to the physics of buoyancy causing the displacement gas to flow to the highest end when pitched. This remains a problem for classic airship types at low altitude until the gas expands to largely fill its aerostat, which it does as atmospheric pressure drops through ascent. Further information from report: StratRaft - a Stratospheric LTA Aircraft, only available from contact.