Exploration of the rain forest canopy using airships and similar aerial platforms
The key technological challenges involved in the development of lighter-than-air platforms to explore tropical rain forest canopy include:
1) A proper understanding of the aerodynamic forces (steady and non-steady) acting in the atmospheric boundary layer immediately above the canopy is required to assist the design process.
2) The development of lighweight power systems. Rechargeable lithium batteries appears to be the best primary power source at present, but fuel cell generators may become competitive for long endurance missions. The White Diamond airship used a state-of-the-art 200Ah lithium-ion battery, but improvements are possible and new batteries are rapidly emerging.
3) Development of quiet thrusters and propulsion systems is needed. The White Diamond used electric motors to drive (ducted) propellers. Wind tunnel tests are being carried-out to reduce noise levels and improve efficiency.
4) Station-keeping close to the canopy: holding station within one or two metres is difficult when there are large sporadic gusts of wind, hence tree clamping systems need to be developed.
5) Vertical height control in supra-canopy atmospheric conditions that may include temperature inversions and micro-thermals. Auto-height holding systems would be beneficial.
6) The development of lightweight helium retaining envelopes that are resistant to high UV levels as well as fungal deterioration. Helium leakage rates have to kept low to reduce operating costs. A programme of work is currently underway with Cameron Balloons UK, http://www.cameronballoons.co.uk/
7) Design of lightweight structures to reduce gondola mass, etc.
8) Development of miscellaneous systems such as helium valves, that cannot be easily acquired.
9) Development of direct and remote-control systems.
10) Development of in-situ scientific packages, e.g., "sniffers" to detect pheromones, floral scents and other airborne volatile chemicals in canopy clouds. See, e.g., http://www.aaai.org/AITopics/html/nose.html
Some sample pictures below show some recent technical activities:
Wind tunnel test in the Whitehead Laboratory
Testing of new design of helium valve