use with Chapter 13
States of Matter
New Technology Is Full of Hot Air
Posted December 1, 1999
In recent years, NASA has faced major budget cuts. This has
caused NASA researchers to develop more efficient projects
and technology. One famous example of such efficiency is the
Mars Pathfinder, a mission to the Red Planet launched several
years ago, that cost only a fraction of what originally was
NASA is now working on perfecting a new spacecraft. It's not
a state-of-the-art rocket ship, nor is it a top-secret satellite.
In fact, the technology for this new type of spacecraft is
based on the oldest type of flying craft-the balloon. Balloons
are relatively inexpensive to launch into our atmosphere,
and they can stay aloft for up to 100 days. In addition, their
parts can be recycled for further missions.
Balloons are more efficient than other inner-atmosphere probes,
such as a robotic plane, because they use buoyant forces to
lift them into the air. Inner-atmosphere probes use massive
amounts of fuel to move about, as well as maintain a certain
altitude. Balloons do not have this difficulty. They stay
aloft because the weight of the gases and equipment is lighter
than the weight of the gas they displace. Balloons can move
about and maintain altitude by just adjusting the heat of
the gas inside the balloon, much like a hot-air balloon, or
by adjusting the amount of gas inside the balloon. Hence,
the only fuel needed is what is required to heat the gas.
Balloons have already been placed into atmospheres of other
planets. In 1985, the former Soviet Union, in cooperation
with France and the United States, sent two balloons into
the atmosphere of Venus. Rockets launched from Earth carried
capsules to Venus, which then inflated the balloons in the
planet's atmosphere. The sensors carried by the balloon made
detailed measurements of the winds on Venus.
Scientists are faced with the challenge of keeping a balloon
in flight for an extended period of time. In December 2001,
NASA Goddard Space Flight Center will launch the Ultra-Long
Duration Balloon (ULDB) into Earth's atmosphere, where it
will glide for several months at an altitude four times higher
than that of passenger jets. In order to meet this altitude
and duration of flight, NASA has had to redesign the shape
and the material of a traditional balloon.
Traditional balloons had a spherical shape and were made of
light, yet strong, material. But when a balloon flies at high
altitudes, the balloon will expand as it rises, which places
stress on the circumference of the balloon. The instruments
hanging below the balloon add additional stress. NASA has
been able to circumvent this problem by switching to a pumpkin-shaped
balloon. The stress in a pumpkin-shaped balloon occurs more
along the seams of the segments, which can be reinforced.
This then reduces the strength requirement of the balloon
material. Despite this reduction, to meet the strength requirement
in this high-altitude project, the material must be stronger
than a traditional balloon and must not allow as much gas
to diffuse out, since the loss of gas prevents a longer flight.
To meet these requirements, NASA has chosen to use a composite
material, with three different layers—a polyester fabric,
a polyester film, and a polyethylene film.
In the future, NASA hopes to use the advances in current balloon
projects, such as the ULDB, to send balloons into the atmospheres
of other planets, including Venus, Mars, Jupiter, Saturn,
Uranus, Neptune, and Titan, a moon of Saturn.
Use the Internet to learn more about the ULDB projects and
other balloons. Write an entry in your Science Journal explaining
how different types of balloons function and use buoyant forces.