Helium Blimp

The small helium blimp used by one of us is 4 m long and has a gas capacity of ~7m (Aber, 2004). The blimp has a classic aerodynamic shape with four rigid fins for stability in flight. It has a payload lift of ~ 3 kg, which is 2-3 times the weight of camera rigs and has proven to be an adequate margin of safety for blimp operation. The camera rig, which is the same system utilized for kite aerial photography (KAP) (see Chapter 7), is attached to a keel along the bottom of the

Helium Filter
FIGURE 8-10 Small gas filter used for preventing dirt and rust particles from entering the special hot-air blimp gas bottle during filling from commercial gas tanks. Photo by IM.

FIGURE 8-11 Blimp ready for flight with radio-controlled camera rig and Picavet suspension attached to keel. Blimp is 4 m (13 feet) long and contains ~ 7 m3 of helium; tether line extends to lower right. Photograph courtesy of N. Hubbard.

blimp (Fig. 8-11). The blimp is secured and maneuvered using a single tether line of braided dacron with a breaking strength of 90 kg (for knots and bends, see Section 8.4.2).

All equipment can be transported in the back of a small truck or trailer including one large helium tank that holds ~ 7 m , which is just enough to inflate the blimp one time. Field operation is relatively simple; first, a large ground tarp is laid out, and the blimp is inflated on this tarp (Fig. 8-12). Once inflated, a camera rig is attached and tested. The whole preparation and inflation procedure takes about half an hour and requires only two people. As with other tethered platforms, the blimp may be flown up to 500 feet (150 m) above the ground in the United States without filing a flight plan with the nearest airport (see Chapter 9.8.2). The tether line is marked at 500 feet, and a laser altimeter is used to confirm blimp height.

The blimp may be sent aloft and brought down repeatedly to change camera rigs or to move to new locations around the study site. In principle, the blimp could remain aloft until the helium gradually leaks out, a period of several days. In practice, blimp aerial photography is conducted normally at a single study site in one day, from mid-morning until mid-afternoon, when the sun is high in the sky. At the end of each session, the helium is released, as there is no practical means to recover it in the field.

The blimp has been utilized under conditions ranging from completely calm to moderate wind speeds in rural and urban settings (Figs. 8-13 and 8-14). The blimp has proven quite stable in calm to light wind and remains relatively stable in wind up to 10-15 km/h. Under light wind, the blimp can be maneuvered quite precisely relative to ground targets. Stronger wind, however, tends to push the tethered blimp both downwind and down in height, so that surrounding obstacles may become troublesome.

This particular blimp is relatively small and easy to handle, which results in excellent portability for reaching any site accessible to a four-wheel-drive vehicle. Furthermore, small blimps of this type are widely available for advertising purposes and are low in cost. Many larger helium blimps have been employed by other people for SFAP. In some cases, a permanently inflated blimp is stored and transported in a big trailer, for example a horse trailer. In this case, none or

FIGURE 8-12 Inflating the blimp on a canvas trap. The helium tank, deflated blimp, camera rigs, and all other equipment are transported in the back of the small four-wheel-drive truck, which can reach remote locations. Photo of SWA by JSA, April 2007.

FIGURE 8-13 Overview of Shoal Creek with agricultural fields in valley bottom to right and forested uplands to left. Launching and operating the helium blimp under near-calm conditions was feasible from the narrow opening between the stream and forest in lower right corner of view. Schermerhorn Park, Cherokee County, Kansas, United States. Taken from Aber and Aber (2009, fig. 74).

FIGURE 8-13 Overview of Shoal Creek with agricultural fields in valley bottom to right and forested uplands to left. Launching and operating the helium blimp under near-calm conditions was feasible from the narrow opening between the stream and forest in lower right corner of view. Schermerhorn Park, Cherokee County, Kansas, United States. Taken from Aber and Aber (2009, fig. 74).

only some of the helium has to be released. This reduces the costs significantly and enables several ascents on successive days. In other cases, a blimp may remain in the air over a study site for long periods of time—days or weeks. Special fabrics and wind-resistant designs are necessary for success with such extended usage. Larger and more robust blimps mean higher costs for equipment and operation and are generally less portable in the field.

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