Unmanned radio-controlled hot-air balloons may, at first sight, seem to be an unlikely form of transport for aerial photography work. However there are quite a few people using them around the world, and a number of companies, particularly in the USA and Germany, now manufacture the necessary equipment. The picture on the right, by kind permission of Bernard Smatana of Aerial Images, shows a typical balloon and aluminium gondola available in ready-to-fly form.

The balloons offer a remarkably stable platform for photography although, as with full-sized manned balloons, flight control is limited to up or down. The direction of flight is determined by local winds, which are a key limitation on flying conditions. A wind speed of about 5mph is regarded as the maximum for successful and safe operation.

A typical R/C hot-air balloon has a capacity of about 1,500 - 3,500 cubic feet and might lift a payload of 10 - 25 lbs. The inflated canopy is about 18 - 22 feet high. Average flight times, determined largely by the volume/weight of propane gas carried for the burners, is about 20 - 30 minutes. The cost of each flight in terms of propane gas is likely to be about £5.

A typical R/C hot-air balloon setup consists of the following equipment:

• A 2,500 cubic foot canopy, with scoop and Velcro rip-out panel for deflation, manufactured from 12 or 24 vertical gores of various weights (0.75 - 2.2oz) of ripstop nylon or Nomex fabric;
• A whicker or aluminium basket/gondola;
• Battery pack and charger;
• Suitable propane tanks (usually a total of about 5kg) available at any good hardware store;
• A propane cylinder refill adaptor;
• About 1,000 feet of heavy duty tether on a spool;
• A 12v inflation fan (powered from a car battery);
• 2 or 4 channel model radio-control.transmitter and receiver and other associated equipment
• Suitable camera mounting and control equipment.

The total cost of this equipment may exceed £2,500.