Note that balloon envelope thickness is generally expressed in units of 1 millionth
of a meter, or micron, using the ‘μ’ symbol of the Greek alphabet. Sometimes the
American standard is used; mil, which is one thousandth of an inch.
2.2.1 Ultra High Altitude Balloon (UHAB)
Since the start of scientific ballooning, researchers have sought to lift increasingly
heavier, more sophisticated, payloads to higher altitudes. In the 1960’s and 1970’s
advances in film extrusion and balloon fabrication techniques enabled the creation
of increasingly larger balloons, culminating with a 1.5 million m
3
(53 million ft
3
)
behemoth successfully launched in 1975. The ability to create significantly larger
balloons was constrained primarily by limitations in materials, including films.
BU60-1
The Japanese Institute of Space and Astronautical Science (ISAS) launched a balloon in 2002 designated BU60-1 to test the flight performance of an envelope
manufactured with a newly developed ultra-thin film only 3.4 μm thick made of
polyethylene. It had a volume of 30,000 m
3
(1.06 million ft
3
). The empty weight
of this balloon was only 60% of conventional high altitude balloons of the same
volume. It reached an altitude of 53 km (173,900 ft) which broke the previous
record set in 1972. As 1 μm equals roughly 0.00004 in, the film was 3.4 times that,
or 0.000133858 in thick. See Section 3.1.5 for a discussion on Ultra-Thin Films.
Big 60
The UHAB development started in March 2002, when NASA requested Raven
Industries to undertake a study on a series of ultra-high altitude zero-pressure balloon platforms. After analyzing several load-altitude targets, NASA chose a 1.7
million m
3
(60 million ft
3
) design with an ultimate payload capacity of 750 kg
(1,653 lb). The balloon was designed using traditional zero-pressure techniques,
but the shell and cap material was chosen to be Stratofilm-430, which was based
upon the Stratofilm-420 developed for the ULDB program. It comprised a threelayer co-extruded film using the same resins as Stratofilm-420. The overall film
thickness was 10.2 μm (0.40157 mil) for the shell and 13.2 μm (0.51965 mil) for
each of the two cap layers. Relative to traditional zero-pressure balloon film, the
Stratofilm-430 had higher strength and ductility at normal surface temperatures,
enabling the shell to better withstand dynamic launch loads.
Production of the balloon, unofficially christened the “Big 60”, required some
minor rearrangement of production space at the Raven factory to accommodate
the almost 230 m (756 ft) gore length. That’s twice the length of a football field
including the end zones. They did it using two tables half the length. Due to its
similarity to standard zero-pressure designs, the fabrication of the balloon was
2.2 Zero-Pressure Balloons (ZPB) 13
of a meter, or micron, using the ‘μ’ symbol of the Greek alphabet. Sometimes the
American standard is used; mil, which is one thousandth of an inch.
2.2.1 Ultra High Altitude Balloon (UHAB)
Since the start of scientific ballooning, researchers have sought to lift increasingly
heavier, more sophisticated, payloads to higher altitudes. In the 1960’s and 1970’s
advances in film extrusion and balloon fabrication techniques enabled the creation
of increasingly larger balloons, culminating with a 1.5 million m
3
(53 million ft
3
)
behemoth successfully launched in 1975. The ability to create significantly larger
balloons was constrained primarily by limitations in materials, including films.
BU60-1
The Japanese Institute of Space and Astronautical Science (ISAS) launched a balloon in 2002 designated BU60-1 to test the flight performance of an envelope
manufactured with a newly developed ultra-thin film only 3.4 μm thick made of
polyethylene. It had a volume of 30,000 m
3
(1.06 million ft
3
). The empty weight
of this balloon was only 60% of conventional high altitude balloons of the same
volume. It reached an altitude of 53 km (173,900 ft) which broke the previous
record set in 1972. As 1 μm equals roughly 0.00004 in, the film was 3.4 times that,
or 0.000133858 in thick. See Section 3.1.5 for a discussion on Ultra-Thin Films.
Big 60
The UHAB development started in March 2002, when NASA requested Raven
Industries to undertake a study on a series of ultra-high altitude zero-pressure balloon platforms. After analyzing several load-altitude targets, NASA chose a 1.7
million m
3
(60 million ft
3
) design with an ultimate payload capacity of 750 kg
(1,653 lb). The balloon was designed using traditional zero-pressure techniques,
but the shell and cap material was chosen to be Stratofilm-430, which was based
upon the Stratofilm-420 developed for the ULDB program. It comprised a threelayer co-extruded film using the same resins as Stratofilm-420. The overall film
thickness was 10.2 μm (0.40157 mil) for the shell and 13.2 μm (0.51965 mil) for
each of the two cap layers. Relative to traditional zero-pressure balloon film, the
Stratofilm-430 had higher strength and ductility at normal surface temperatures,
enabling the shell to better withstand dynamic launch loads.
Production of the balloon, unofficially christened the “Big 60”, required some
minor rearrangement of production space at the Raven factory to accommodate
the almost 230 m (756 ft) gore length. That’s twice the length of a football field
including the end zones. They did it using two tables half the length. Due to its
similarity to standard zero-pressure designs, the fabrication of the balloon was
2.2 Zero-Pressure Balloons (ZPB) 13