Helium balloons for SFAP

Helium Balloons
for SFAP
ES 555 Small Format
Aerial Photography
James S. Aber

Lighter-than-air gases

Several lighter-than-air gases could be employed for balloons to lift aerial camera equipment--hydrogen (H₂), helium (He), or methane (CH₄). Hydrogen and methane are both explosive and highly flammable; they will not be considered further for obvious safety reasons, which leaves helium as the gas of choice for all modern balloon and blimp applications.

Helium is created as a byproduct of radioactive decay within the solid Earth. Continental crust, which is enriched in uranium and other radioactive elements, is a constant source for helium. Because it is inert, helium does not combine with minerals in the crust, but it does readily dissolve into fluids such as natural gas and ground water. Eventually the helium reaches the surface and is released into the atmosphere. Earth's gravity is too weak to retain the helium molecule (single He atom), so it ultimately escapes into space.

In certain rare geological situations, helium may be trapped in natural-gas reservoirs in the subsurface. Helium extracted from natural gas is the only commercial source. As an industrial commodity, compressed helium is widely available at modest cost in steel cylinders that can be purchased or rented from gas distributors, such as Linweld. Large (K) cylinders hold about 242 cubic feet (6.8 m³) and weigh around 120 pounds (55 kg); smaller (S) cylinders contain 150 cubic feet (4.3 m³) and weigh 65-70 pounds (30 kg). A special balloon-filler valve/nozzle is required for inflating a latex balloon from a compressed helium cylinder.

Helium cylinder mounted on a hand truck for easy transport. This S-sized tank weighs 65-70 pounds when full and contains about 150 cubic feet of helium. It is shown here with the safety cap in place (top of tank). The cap is required whenever the tank is transported or stored. Photo date 3/01 © J.S. Aber.
Closeup view of valve and nozzle for inflating latex balloons. The valve is openned by bending the black rubber nozzle. This valve must be removed for transportation and storage of the tank. Photo date 3/01 © J.S. Aber.

Latex balloons

Many people are familar with weather balloons, used to lift meteorologic instruments into the atmosphere. Such balloons are designed to expand and burst upon reaching a specified altitude (air pressure); the instrument package then parachutes down to the ground. This type of balloon is risky for aerial photography, as premature breaks may occur. In balloon aerial photography, the balloon is normally tethered to the ground, and recovery is a simple matter of pulling the tether line down. Heavy-duty latex balloons are better suited in this application, as they are more durable (reuseable) and less likely to burst.

It is common practice to inflate latex balloons to a size somewhat less than the stated full diameter. While this reduces the balloon's lifting capacity, it also reduces the likelihood of balloon failure. For example, a 4-foot diameter latex balloon filled to 3½ feet diameter can lift one pound (0.45 kg) under nominal conditions--see table below. Rather than using one large balloon to lift a camera rig, several smaller balloons can be utilized to minimize the risk of balloon failure.

Helium requirements for large latex balloons (in English units).
Data obtained from Qualatex Balloons.
Ballon type	Inflated diameter	Lift	Gas volume	No. fillings per tank*	Flying time
3' Giant	2.5'	6.5 oz.	8 cu ft	30	3-5 days
3' Giant	3.0'	12 oz.	15 cu ft	16	3-5 days
4' Jumbo Giant	3.0'	9.5 oz.	15 cu ft	16	5-7 days
4' Jumbo Giant	3.5'	16 oz.	24 cu ft	10	5-7 days
4' Jumbo Giant	4.0'	27 oz.	35 cu ft	7	5-7 days
5' Jumbo Giant	4.0'	24 oz.	35 cu ft	7	7+ days
5' Jumbo Giant	4.5'	34 oz.	50 cu ft	5	7+ days
5' Jumbo Giant	5.0'	51 oz.	66 cu ft	3½	7+ days

* Large (K size) helium tank holds approx. 242 cubic feet.

Left: author demonstrates three latex balloons attached to a tether line. The balloons are inflated to slightly less than their nominal 3-foot diameter. The reel hold 1000 feet (300 m) of braided dacron line. Photo date 4/01 © J.S. Aber.

Right: Three 3-foot helium balloons easily lift a radio-controlled camera rig weighing 570 g (1¼ pounds). This arrangement works well in wind less than 5 km/h (3 mph), but is unsuitable for stronger wind. Photo date 4/01 © J.S. Aber.

As in all forms of aerial photography, clear sunny sky is essential. In addition, a tethered balloon is feasible only in calm or very light wind conditions--less than 3 mph (5 km/h). Any more wind pushes the "captive" balloon to the side and downward, as the wind force acting on the balloon and tether becomes stronger than the helium lift. This means practically that balloon aerial photography must be done under weather conditions of high pressure, when wind is typically light and variable. Large tethered balloons are subject to the same flying restrictions as large kites--500 feet (150 m) maximum height is permitted without filing a flight plan with the nearest airport. This height limit is well within the typical range employed for small-format aerial photography.

Related sites

BurningCam balloon aerial photography (2000).
Balloon aerial photography at Burning Man (1996).
Balloon lift with lighter-than-air gases. From the University of Hawaii at Manoa.
Floatograph balloon aerial photography system.

	Helium cylinder mounted on a hand truck for easy transport. This S-sized tank weighs 65-70 pounds when full and contains about 150 cubic feet of helium. It is shown here with the safety cap in place (top of tank). The cap is required whenever the tank is transported or stored. Photo date 3/01 © J.S. Aber.
	Closeup view of valve and nozzle for inflating latex balloons. The valve is openned by bending the black rubber nozzle. This valve must be removed for transportation and storage of the tank. Photo date 3/01 © J.S. Aber.