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High altitude balloon

High altitude balloon

At launch the balloon and capsule together stand taller than Seattle's Space Needle

A 40 acre dry cleaner bag carries nearly 3,000 pounds. That's the Red Bull Stratos Balloon.

Type: The balloon is filled with helium to create lift. Helium is non-flammable, non-toxic if vented to the atmosphere and a safe, predictable method of ascent.

Material: It is constructed of strips of high-performance polyethylene (plastic) film that is only 0.0008 inches thick. In total, these strips would cover 40 acres if they were laid flat. Polyester-fibre reinforced load tapes are incorporated to do the weight bearing.

Size, volume and shape: The balloon for Felix's mission from the edge of space will be nearly 30 million cubic feet in capacity - 10 times larger than Joe Kittinger's balloon in 1960.

At launch, it will be tall and thin, stretching 55 stories high. As the balloon ascends, the helium will expand and the balloon will slowly fill out to an almost completely round shape:

Length of uninflated balloon before launch: 592.41 feet. Height of balloon at take-off: 550 feet. The height from the top of the balloon to bottom of the capsule will be: 695 feet. Size of balloon at 120,000 feet: Height 334.82 feet / Diameter: 424.37 feet

Weight: The uninflated balloon weighs 3,708 pounds


Helium is delivered on two large trucks. Another truck with a "launch arm" restraint holds down a portion of the balloon during inflation. At launch, the arm moves out of the way to allow the balloon to ascend. Simultaneously, a large crane drives in to position the capsule under the balloon. The crane releases the capsule, the balloon lifts it off the crane, and the ascent begins.


Was the balloon specially developed for the Red Bull Stratos mission?

The balloon is a standard design utilizing principles and materials that have been refined over 60 years of high-altitude scientific balloon flights.

Are there hazards associated with helium balloon flight?
Balloons are susceptible to wind, which can literally tear them - particularly at critical times.

Take-off, when difficulties due to weather or other factors could drag the capsule across the ground or cause a sudden dangerous drop in height. If a problem occurred below 1,000 feet, there would not be enough time to deploy a personal or capsule parachute.
Ascent through the troposphere (30,000 to 60,000 feet), where turbulence is common.
Float altitude(top altitude), where low air pressure will cause the helium to expand so much that if the excess cannot escape through the balloon's vent tubes, it will burst. Helium inflation quantities are carefully calculated to avoid this.

How long does it take to inflate the balloon?

The overall launch process for this kind of balloon requires approximately 8 hours of preparation immediately before launch, including about 45 to 60 minutes for insertion of the helium.

How big is the launch crew?
The balloon launch crew itself is about 12 to 15 people, all of whom must wear clothing that won't snag the balloon. A number of individuals will clear the runway of fine debris before laying out the balloon. Fewer than 10 people actually handle the balloon, and those who do wear cotton gloves.

Why does a helium balloon rise?

Helium is lighter than air. If the balloon is large enough in relation to the weight of its payload, the helium will ascend and bring the payload with it.

How fast will the balloon ascend?

The balloon will ascend at about 1,000 feet per minute. At some points, its ascent could be as fast as 1,400 feet per minute. Upon reaching about 100,000 feet, however, it will likely slow to roughly 750 feet per minute until it levels off at approximately 120,000 feet above sea level.

How is the balloon steered?
Wind is used to direct a balloon's trajectory. Wind speed and direction vary at different altitudes so balloons are steered by changing altitude to reach the desired wind conditions. Releasing helium causes a decrease in altitude, while dropping ballast allows a balloon to rise.

How does the balloon avoid other aircraft in the sky?

The balloon will be tracked by the mission team while in the air. The mission team coordinates closely with the U.S. Federal Aviation Administration to obtain clearance for flight and special reflective tape is incorporated into the seams so that it can be seen on radar.

Felix's target altitude is described as "float altitude." What is that?

Float altitude is the point at which the balloon levels off and stops ascending. Although helium is lighter than air, at higher altitudes air density is reduced. Float altitude is reached when the average density of the balloon is the same as the density of the surrounding atmosphere.

What happens to the balloon after Felix jumps?

After Felix has landed, Mission Control will trigger the separation of the capsule and balloon, so that the capsule can descend under its parachute. A nylon "destruct line" will release the helium so that the balloon returns to Earth. Then, the team will gather the envelope into a large truck, a process that can take several hours.

Is the same balloon being used repeatedly for tests, as well as the final mission?

No. The test balloons are smaller than the almost 30 million cubic foot balloon used for the ascent to 120,000 feet. None of these delicate balloons can be re-used. In fact, once Felix's balloon is even taken out of its box it must be launched promptly or discarded.

Who is responsible for launching the balloon?

ATA Aerospace provides the balloon launch services, personnel and equipment for Red Bull Stratos. Key personnel on the ATA team include crew chief Ed Coca, meteorologist Don Day and project lead Tracy Gerber. A joint venture of Albuquerque-based Applied Technology Associates and ASRC Aerospace, ATA Aerospace offers the expertise of an extensive history in large-scale balloon launches, including serving as the prime contractor on the AFRL Space Technology Research, Analysis, Integration and Test (STRAIT) contract. On this contract, ATA Aerospace provides the program management; engineering services; integration, test, and launch support; on-orbit support; and test facility operations and management for satellite and high-altitude systems and subsystems including buses and payloads. For more information:


The best weather conditions for balloon launch usually occur at dawn. Here is an approximate timeline.

Launch minus 8 hours

After a weather and safety briefing, the team inspects the equipment and communications systems, then pulls the boxed balloon and equipment out of the hangar while a separate crew works to clear the runway of dirt, debris and other objects. The capsule and balloon are delivered to the launch area on a cleared runway. More checks and re-verifications are conducted.

Launch minus 4:30 hours
Crew Chief contacts Mission Control for permission to lay out the flight train components. Balloon is laid out on a layer of Herculite. Then balloon, parachute and capsule are connected.

Launch minus 2:45 hours
Layout of flight train is complete.

Launch minus 2:15 hours

Balloon's helium valves are rechecked and verified.

Launch minus 1:15 hours
All capsule checks are complete.

Launch minus 1:00 hours
Crew chief contacts meteorologist and requests permission to begin inflation.

Launch minus 0:55 hours
Inflation begins.

Launch minus 0:30 hours
Felix is sealed in capsule which is cradled on a crane and pressurization begins.

Launch minus 0:10 hours
Inflation is complete.

Launch minus 0:05 hours
Crew chief inspects the entire flight train and removes all safety restraints

Launch minus 0:01 hours

Balloon bubble is released from launch arm.

As the balloon rises, the crane bearing the capsule drives rapidly down the runway to meet it. The crane releases the capsule when it's vertical with the balloon. The balloon lifts the capsule off the crane and the ascent begins.