Why use such a delicate material? A very large balloon is needed to carry the Red Bull Stratos capsule (which weighs nearly 3,000 lbs / 1.360 kg) to the stratosphere. Very thin material is necessary to save weight. As it is, despite the light weight of the polyethylene, there is so much of it (40 acres) in Felix’s balloon that uninflated it weighs 3,708 lbs / 1.682 kg.
What is the balloon filled with, and why? The balloon is filled with helium. Helium is lighter than air, providing the lift needed to take a heavy payload to the stratosphere.
How is a helium balloon different from hot air balloons used for sightseeing? They’re different in many ways, including size, material and construction methods, but perhaps most significantly, using helium for lift allows a higher altitude. A hot air balloon is limited because the air inside must be heated (usually via propane burners) to provide lift — and with low oxygen in the upper stratosphere such heating wouldn’t be feasible. Helium is lighter than air and provides lift without heating.
How much helium is used? The team will insert about 180,000 cubic feet / 5.097 cubic meters of helium at launch. As the balloon rises and the air pressure decreases, the helium will expand until the entire capacity of nearly 30 million cubic feet /849,505 cubic meters is full.
That’s 10 times larger than Joe Kittinger’s balloon in 1960, and three times bigger than the largest balloon ever launched with humans aboard (project Strato-Lab in 1961).
What are the dimensions of the balloon?
Length of uninflated balloon before launch: 592.41 feet / 180.56 meters
Height of balloon at takeoff: 550 feet / 167 meters
Takeoff height from the top of balloon to bottom of capsule: about 750 feet / 228 meters
Size of balloon at 120,000 feet / 36.576 meters:
- Height 335 feet / Diameter: 424 feet
- Height 102 meters / Diameter 129 meters
What kind of weather conditions are necessary to launch such a large balloon? The factor that concerns the team most is wind. Winds must be no more than about 2 mph / 3 kmh from ground level to about 800 feet / 244 meters.
Read more on the weather for this mission to the edge of space.
What else are these kinds of balloons used for? Helium balloons are used by government and university programs to launch weather equipment and telescopes that look into deep space, and also to provide near-space testing of components in preparation for eventual space missions. They are usually custom-made, so there are very few in existence.
What happens to the balloon after Felix’s jump is complete? When Mission Control determines that the balloon is over an appropriate area, the capsule is remotely triggered to detach from the balloon. The balloon is automatically torn by a cable as it separates from the capsule, so the helium, which is non toxic when vented into the atmosphere, escapes and the empty balloon envelope falls to earth. A field crew retrieves polyethylene material, a process they’ve compared to “wrestling an elephant.” The balloon team also retrieves a digital logger to analyze data from the mission, which can help to inform future flights.
Who launches the balloon? The balloon launch crew is from ATA Aerospace, a company with a half-century of experience, including support of some of Joe Kittinger’s missions. ATA Aerospace is trusted to launch U.S. Air Force high-altitude balloon projects, and collectively the crew members for the Red Bull Stratos balloon have the experience of thousands of balloon launches.
Key among them are crew chief Ed Coca, who directs the team on the runway, and project lead Tracy Gerber, who coordinates balloon launch operations from Mission Control.
How many balloons does the Red Bull Stratos team have? The team had two identical balloons on hand for Felix’s record-breaking attempt. One was used for the aborted launch on October 9 and cannot be re-used. An identical backup balloon will be used for the next attempt, and the team is investigating the possibility of procuring a third balloon should it be needed.
Read here about other high-altitude balloon record attempts.