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Winter mornings in Reno, Nevada, are often amazingly clear and calm.
This is weather that balloonists dream of, which is why, from 1 November,
the three-man crew of the balloon Earthwinds Hilton will be waiting there,
ready to jump into their lightweight capsule and circle the globe nonstop
– a trip that is expected to take less than three weeks.

The Earthwinds Hilton’s flight crew comprises Larry Newman, a pilot
for America West Airlines, balloonist Richard Abruzzo, and former cosmonaut
Vladimir Dzhanibekov. They will take with them two packages of scientific
instruments, one from Russia and the other from the US, to lend an international
scientific flavour to what is largely an engineering challenge and, most
of all, an adventure. Around 1500 instrument-carrying balloons have circled
the globe this century, but Earthwinds Hilton aims to be the first to include
people.

‘Successfully circling the Earth in a balloon is one of the last great
aviation plums,’ says Barron Hilton, the project’s sponsor. He is the chair
and chief executive of the famous chain of Hilton Hotels, and a fan of flying
– in hot-air balloons, jets, helicopters and gliders. This project gives
him the first opportunity to indulge his enthusiasm on a grand scale. It
was originally sponsored by Richard Branson, who in January 1991 plucked
the previous aviation plum, a balloon crossing of the Pacific.

Third time lucky?

Since Hilton took over in July 1992, his team has made one unsuccessful
attempt at the trip in January. This followed Branson’s previous attempt
in February 1992. Now the Earthwinds crew and hundreds of volunteers are
ready for the third try.

As well as being a daredevil stunt, global circumnavigation is a test
of high-technology materials and engineering. Earthwinds Hilton’s capsule
will be suspended between two balloons which, when fully deployed, will
resemble an enormous figure eight standing over 110 metres tall. The upper
lift balloon, 43 metres in diameter and made of clear polythene film, will
be filled with 31 150 cubic metres of helium – enough to fill five Goodyear
blimps. As in conventional designs, the balloon vents helium if its pressure
gets too high for safety.

But unique to Earthwinds is the use of air for ballast instead of sand
or water. The ballast air is contained in an anchor balloon 33 metres in
diameter, that hangs below the capsule. This is made from a fabric that
does not expand as the balloon ascends into the thin upper atmosphere. Thus,
the air in the anchor remains at the density of ground-level air and will
exert a downward pull against the upper balloon’s lift. By releasing air
from the anchor, or pumping it in, the balloonists should be able to control
their altitude precisely.

The concept of an anchor balloon has been kicked around since the 1790s,
according to Tim Lachenmeier, the aerospace engineer with Raven Industries
of Sioux Falls, South Dakota, who designed the Earthwinds system. But for
most of the intervening two centuries, balloonists could not test the idea
because they lacked materials that were light and strong enough. It was
only in 1985, when Spectra – the synthetic fibre with the highest known
strength-to-weight value – was developed by AlliedSignal of New Jersey in
the US, that the anchor balloon became practical, he says.

Spectra fibres are made from polythene – a polymer more familiar from
drinks bottles and washing-up bowls – yet they are ten times as strong as
steel cable when compared by weight. The difference is that the polymer
molecules used to make Spectra are up to a hundred times as long as those
of conventional polythene. Already intrinsically strong, the molecules receive
special treatment as they are formed into fibres, to enhance the strength
of the finished product. In most synthetic fibres, the molecules tend to
bunch up and fold over each other as they are being spun, causing weak spots
to form. To prevent this from happening with Spectra fibres, the molecules
are suspended in hot mineral oil as the fibre is spun. When the oil is extracted,
the result is a fibre made up of thousands of molecules packed tightly together.

Nevertheless, the finished fabric has had to be carefully inspected
and handled to guarantee that it is free of flaws. A broken or missing thread
in the fabric of the anchor balloon could develop into a disastrous tear
at high altitudes. For instance, a thumb-sized hole, probably made by a
soldering iron, was discovered in the anchor balloon during January’s attempted
launch and had to be sewn up on the spot.

Lightweight materials are also used for the capsule, which is shaped
like a rugby ball dangling between the two balloons. The capsule’s shell
is built from a composite of fibreglass and carbon fibres bonded together
with epoxy resin. Inside, two 12-horsepower (9-kilowatt) engines will supply
power for compressing air for the anchor balloon and the capsule, and for
generating electricity. To keep weight down, there will be just one bed,
and the three passengers will have to take turns to sleep. They will dine
on food from sealed pouches, much as astronauts do. The three will be in
constant touch via a satellite telephone link with ‘mission control’ back
in the Reno Hilton hotel. A chase plane will follow the balloon around the
world.

Bad weather and lack of familiarity with the dynamics of the experimental
craft have been blamed for the previous failures. For the first attempt,
out of a Goodyear balloon hangar in Akron, Ohio, the upper balloon was inflated
inside the hangar. When it emerged, turbulent winds caused it to twist uncontrollably
and the flight was abandoned. Reno was chosen as the new launch site as
it was thought that the temperature inversions that are common there in
winter would keep winds at bay, making for a smooth launch. For the second
attempt, earlier this year, the weather was calm, but the launch was defeated
by ground-level temperatures as low as -28 °C. It was so cold that the
gas in the upper balloon became too dense to lift the craft through the
warmer layer of air above. The result was that it drifted horizontally and
hit a craggy ridge nearby.

Even with the knowledge gained from previous launch attempts, the project
still has plenty of unknowns, says John Ackroyd, the missions engineer.
After all, the system has never been in the air, apart from its short flight
straight into the mountain. Moreover, the expensive specialised balloon
is not reusable, and the budget is limited. ‘The first flight is the maiden
flight, the test flight and the final flight all wrapped in one,’ says Ackroyd.

‘Funders will never put up money for an adequate test programme,’ comments
Vincent Lally, who has launched hundreds of balloon projects, including
many uncrewed round-the-world flights for NASA. And Earthwinds seems to
be under some pressure, as other circumnavigations are being planned.

Good atmosphere

The Earthwinds Hilton balloon therefore needs to succeed during this
winter’s launch window, which ends in February. This time the team will
be able to call on scientists from the Desert Research Institute (DRI) in
Reno for meteorological data. Atmospheric physicist Melanie Wetzel says
she will be deploying her tethered balloon system to take accurate temperature
and wind measurements from as high as 500 metres above the launch site,
providing real-time weather forecasting of the layer of air through which
Earthwinds Hilton will ascend to reach its cruising altitude of about 10
000 metres.

Returning the compliment, the balloon will be carrying instruments
for an experiment devised by DRI scientists Randolph Borys and Douglas Lowenthal,
which will measure ozone and sulphate particles at the boundary of the stratosphere
and troposphere, which is where Earthwinds will travel. And Russia is lending
not only its prized former cosmonaut but also a separate package of ozone
and aerosol particle detectors.

Lally describes the science as little more than window dressing. ‘This
project exists for itself. It’s just a fun project.’ But will Earthwinds
Hilton make it round the world? Despite his criticism, Lally thinks it just
might – that is, if the enormous two-balloon system can get off the ground
and up to altitude. This, he believes, is the big ‘if’. And if, by the end
of this winter, the Earthwinds team has still not made it, will Hilton pull
out of the project, leaving the way clear for his competitors? Says project
spokeswoman Erin Porter, ‘We’ll cross that bridge when we come to it.’

Scott Veggeberg is a freelance writer based in Philadelphia, US.