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Solar Impulse gathers
support around Europe
Solar Impulse’s first prototype solar-powered aircraft completed a European promotional tour this year, in the run-up
to a planned non-stop, round-the-world flight in 2014, writes Andrzej Jeziorski.
n Sunday, 3 July, Solar
back at Payerne
bringing to a close
the revolutionary solar-powered aircraft’s
European tour as the team gears up
attempt a non-stop circumnavigation of
the globe in 2014.
The prototype, piloted by Solar Impulse
co-founder and Chief Executive Officer
Andre Borschberg , touched down in the
evening in Payerne after a 12-and-a-half
hour flight, p owered by solar energ y alone.
Solar Impulse says its European promotional
flight campaign was “highly successful”, with
Borschberg and Solar Impulse founder and
President Bertrand Piccard meeting – among many
others – several high-le vel political and financial figures.
“The feedback from our European flight campaign is
encouraging ,” says Piccard. “ The welcome we received
from political and industrial circles in Brussels and Paris
shows that Solar Impulse is pioneering a new way of
thinking in terms of renewable energ y and energ y saving.”
In Brussels – as g uests of the President of the European
Parliament, the President of the European Council and
of the European Commission – the Solar Impulse team
actively promoted new technologies and renewable
energies with the aim of reducing dependency on fossil
fuel. From there, the team travelled to Paris as sp ecial
guests of the International Air and Space Show at Le
The aircraft, with Borschberg at the controls
co mpleted three international flights during the
European campaign: a 630 km leg from Payerne to
Brussels on 13 May ; 395km from Brussels to Paris-Le
Bourget on 14; and 426km from Paris-Le Bourget to
Payerne on 3 July.
The flights were part of a long run-up to the team’s
ultimate goal : a round-the-world flight scheduled
for 2014. “These flights have provided good learning
opportunities in terms of slotting the solar aircraft into
international air spac e and landing at international
a irports,” Solar Impulse says.
“This solar plane is an extraordinary example of what
we can do with stored energ y,” Borschberg says. “ The
welcome we received in Brussels and Paris was highly
motivating for the team as we enter phase two of the
project which is building a second plane to fly around
The ultimate goal of the programme is ambitious:
to circumnavigate the Earth, non-stop, carrying two
pilots and no fuel whatsoever. Instead , solar energ y
will power the aircraft’s ele ctric motors and charge
batteries that will keep it flying at night.
HB-SIA is a single-seat prototype – a precursor to
the t wo -seat aircraft that will attempt the round-the-
world mission. The aircraft took to the air for its first
time on 7 April 2010, completing an 87-minute flight
up to an altitude of 1,200m (3,937ft). Since then, the
aircraft has been constantly pushing back boundaries
and breaking records.
The first prototype is designed to stay aloft
continuously for up to 36 hours and will be followed by a
larger single-seater, HB-SIB, which will be limited in its
flight duration only by the pilot’s endurance. Eventually,
improved battery efficiency will yield further weight
reductions that will permit the construction of a two -
seat aircraft. This last is the one that will be used for the
non-stop round-the-world flight.
HB-SIA has a wingspan of 63.4m
– about the same as an Airbus A340 –
while being just 21.85m in length. Hug e
efforts have been put into keeping the
loaded weight down to 1,600kg – about
the same as an average family car.
The aircraft is built around a carbon-
fibre composite honeycomb sandwich
structure. The upper wing surface is
covered with a skin of encapsulated solar
cells and the underside comprises a high-
resistance, flexible film. Inside the wing ,
120 carbon-fibre ribs, placed 50cm apart,
maintain the aerodynamic cross-section .
The Solar Impulse energ y-
capture system comprises 11,628
monocrystalline silicone solar cells,
each just 150 microns thick and sele cted for their
lightness and flexibility. Their energ y efficiency could
be higher – it is now 22 percent – but they remain the
optimum solution for now.
The project’s biggest weight challenge is carrying the
batteries needed to keep the aircraft flying at night. In
HB-SIA, the solution is the carriag e of about 400kg
of lithium polymer batteries – accounting for about a
quarter of the aircraft’s total weight.
Beneath the aircraft’s slender wing are four
gondolas, each containing a 10hp electric motor,
a lithium polymer battery set and a management
system controlling electrical charge/discharge and
temperature. Thermal insulation protects the systems
from temperatures of -40 degrees Celsius encountered
at 8,500m altitude. Each engine also has a reducer that
limits the rotation of the aircraft’s 3.5m, twin-bladed
propellers to 200-4,000rpm.
“Our future depends on our ability to convert
rapidly to the use of renewable energies,” Piccard
said on the occasion of the first aircraft’s maiden
flight. “Solar Impulse is intended to demonstrate
what can be done already today by using these
energies and applying new technologies that can
save natural resources.”
AsianAviation | JULY-AUGUST 2011 37
Solar Impulse’s European flight campaign was part of
a run-up to a round-the-world flight planned for 2014.
2/09/11 5:57 PM
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