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testing out this technology and
carrying out scientific experiments in a space environment.
Ascent time is usually around
3 hours, initial ascent speed can
be around 3 metres per second
this then reduces as the atmosphere thins and the buoyancy
becomes proportionally less,
for each 5.5 km you ascend, the
atmospheric pressure halves so
when you reach an altitude of
5,500 metres, the air pressure is
only about one half of what it
was at sea level, half of the Earth’s
atmosphere is already below you,
at 11,000 meters air pressure is
only about one quarter of that at
sea level and at an altitude of 30
km you have risen above 99% of
the Earth’s atmosphere.
The speed of most stratospheric balloons will be determined by wind speed which at an
altitude of 30km is approximately
15knots ( 7.5 metres per second)
or 27 kilome tres per hour.
The volume of the Balloon and
pressure and super pressure.
Zero pressure balloons are
the amount of lifting gas in rela- the most common type of large
tion to the weight of the vehicle,
stratospheric balloon, they are
determines the maximum alti- designed to release their lifting
tude you can achieve, i.e a lighter
gas once they have achieved
balloon fabric and science capsule there maximum inflation size and
will mean the Big Space Balloon
the lifting gas begins expanding
could go higher, although as
further in the sunlight, to avoid
stated earlier this isn’t a priority
the balloon envelope bursting or
at the moment.
ripping.
The heating of balloon by
By adjusting the total weight
solar radiation from the Sun and of the balloon and payload in relathe atmospheric temperature and tion to the balloon envelope size
moisture in the air can also effect
and amount of lifting gas, you can
the altitude reached.
determine the approx altitude
The balloon will then contract
in the night-time when the lifting
you wish to achieve.
The balloons payloads of
gas cools, resulting in a loss of alti- Zero pressure types are designed
tude. This loss in Altitude will vary
to release ballast (usually sand)
according to the type of balloon during the night time cycle, this
design we finally use.
allows the balloon to climb again
Main types of large strato- due to having reduced its weight.
spheric balloons
When the balloon gets
There are two main types of
heated by the sun again during
large stratospheric balloons, zero
the daytime cycle, more lifting
ICY SCIENCE | WINTER 2013- 2014