VOL. 13 September ISSUE YEAR 2012
Off the Beaten Track
in Vol. 13 - September Issue - Year 2012
Around The World In Twenty Days
Over the Swiss Alps
Cutaway view of the balloon
How do you steer a fifty-five meter tall balloon and make it go where you want it to go while attempting to fly it around the world? This was only one of the difficulties, and perhaps not even the biggest difficulty, faced by the team of adventurers who successfully faced what had been described as the last great aviation challenge of the twentieth century: a non-stop, round-the-world flight in a balloon.
The goal had been established in 1980, when British balloon builder Don Cameron announced that a group of balloon enthusiasts planned to circumnavigate the world in a balloon. But it would take many unsuccessful attempts by eighteen teams launching a total of sixteen balloons and almost another twenty years, before the dream would come true.
On the morning of March 1st, 1999, pilots Bertrand Piccard and Brian Jones took off from a grassy field outside a small village in the Swiss Alps. The balloon was named Breitling Orbiter 3 and was the result of many lessons learned from the models used in the two previous failed attempts.
The two main components of the aircraft were the balloon and the gondola. What is commonly referred to as a balloon is actually called the envelope in technical terms. The envelope mounted on the Breitling Orbiter 3 was a Rozière type, a hybrid combining the advantages of helium and hot air which allows the craft to fly very long distances. In this type of envelope, a large cell filled with helium is enclosed within an even larger cell containing hot air. The air is kept hot by propane burners attached to the roof of the gondola. Besides providing lift on its own, the hot air warms the helium, causing it to expand and provide greater lift. This hybrid system ensures maximum temperature stability and a fairly constant altitude, while at the same time conserving helium and propane. The aircraft gains altitude thanks also to the expansion of the helium caused by the heat of the sun and by the lower atmospheric pressure at high altitudes. The design of the Rozière balloon is completed by an insulating tent mounted on top of the main envelope and held up by a smaller helium-filled cell. The purpose of this insulating tent is to protect the main envelope from solar radiation, especially strong in the upper atmosphere. The entire balloon stood fifty-five meters tall when fully inflated.
The gondola on the Breitling Orbiter 3 was a five-and-a-half meter long orange-colored cylinder, barely more than three meters high. In spite of the light but resistant blend of Kevlar and carbon fiber material with which it was made, the gondola weighed in at over two metric tons. Given that the two crew members would work in shifts, there was only one bunk bed in the center, navigational and communications equipment at one end and a small toilet and storage space at the other end. After takeoff, the cabin was sealed at 1800 meters to trap the air inside, after which fresh air and cabin pressure were maintained with a mixture of nitrogen and oxygen. The carbon dioxide was removed by lithium hydroxide filters. At the normal cruising altitude of ten thousand meters, the cabin pressure was kept equal to the atmospheric pressure at three thousand meters. At ten kilometers above the ground, the outside temperature can go as low as – 55°C, but an electrical heating system ensured that the temperature inside the gondola never went below 15°C. Electricity was provided by lead-acid batteries charged by solar panels suspended beneath the gondola. The crew had a supply of fresh food sufficient for the first six days, after which they resorted to dehydrated meals. A two-hundred liter fresh water tank completed their on-board supplies. The propane gas needed for the burners was stored in twenty-eight titanium cylinders attached along the sides of the gondola.
Meticulous planning and correct predictions of the wind currents which pushed the Orbiter eastwards at speeds of up to 161 knots were the key to the mission’s success. After crossing northern Africa, the Arabian Peninsula and India, the sensors reported that the balloon was behaving as predicted and that fuel consumption was actually a bit lower than expected.
When the craft had overflown Burma, the furthest point ever reached by previous failed attempts, it began to seem that the dream would become reality.
On and on it flew, across the Pacific, over Central America and the Atlantic, when, finally, after almost twenty days in the air, the gondola landed safely in the Egyptian desert, having traveled a distance of almost 41,000 kilometers.
By Giovanni Gregorat, Contributing Editor MFN & Sales Manager, Pometon Abrasives
Author: Giovanni Gregorat