Solar Impulse
HB-SIA

With its huge wingspan equal to that of an Airbus A340, and its proportionally tiny weight – that of an average car - the HB-SIA prototype presents physical and aerodynamic features never seen before. These place it in a yet unexplored flight envelope.

 

Carbon fiber structure, propulsion chain, flight instrumentation, everything has been designed to save energy, to resist the hostile conditions facing airplane and pilot at high altitudes and to marry weight restraints with the required strength.

 

It was not built to fly round the world. Its purpose was rather to demonstrate the feasibility of the program by making the first ever whole day-and-night flight without fuel, a task that it accomplished brilliantly in July 2010. The lessons learned by the team are now being applied to the construction of Solar Impulse HB-SIB, which is due to circumnavigate the Earth in 2015.

The question of energy defines the entire project.

At midday, each square meter of land surface receives, in the form of light energy, the equivalent of 1000 watts, or 1.3 horsepower of light power. Over 24 hours, this sun energy averages out at just 250W/m². With 200m² of photovoltaic cells and a 12 % total efficiency of the propulsion chain, the plane’s motors achieve an average power of 8 HP or 6kW.

That’s roughly the amount of power the Wright brothers had available to them in 1903 when they made their first powered flight. And it is with that energy, optimized from the solar panel to the propeller, that Solar Impulse managed to fly day and night without fuel!

FIVE world records:

  • Absolute height: 9235 m (30300 ft)
  • Height gain: 8744 m (28690 ft)
  • Duration: 26 hours, 10 minutes, 19 seconds
  • Free Distance along a course: 1116 km (693.5 miles)
  • Straight distance, pre-declared waypoints: 1099.3 km (683 miles)
Légende photo

HUMAN RESOURCES

The construction of the prototype would have been impossible without the intense collaboration between the Solar Impulse team, charged with the plane’s design, and the materials suppliers, the components producers and other partners. It was only by wrestling with the specifications and fully exploring everyone’s potential that totally new aeronautic solutions were found.

ENERGY RESOURCES

Multiple forms of energy have had to be managed and their conversion phenomena understood and optimized:

  • photic – the mechanics of solar radiation
  • electrical – in the photovoltaic cells, the batteries and the motors
  • chemical - inside the batteries
  • potential - when the plane gains altitude
  • mechanical - through the propulsion system
  • kinetic - when the plane gains speed
  • thermal – the various losses (friction, heating…) to be minimized at all costs

EFFICIENCY AND STORAGE CAPACITY

The 12 000 or so photovoltaic cells of 145 micron monocrystalline silicon combine lightness and efficiency. Their efficiency could have been even higher, like the panels used in space, but their weight would then have been much too high, penalizing the plane during night flight. This phase being the most critical, the main constraint is the one imposed by the batteries. Still heavy, they require a drastic reduction of the weight of the rest of the plane, so as to optimize the whole energy chain and to maximize the aerodynamic performance provided by using a high aspect ratio wing with a low-speed profile. With an energy density of 240Wh/kg, the lithium polymer accumulators weigh 400kg, or more than ¼ of the total mass of the plane.

STRUCTURE AND MATERIALS

Reconciling rigidity with lightness and controllability in flight, Solar Impulse is constructed around a skeleton of carbon fibre-honeycomb composites in a sandwich assembly. The upper wing surface is covered with a skin of embedded solar cells and the lower surface with lightweight flexible film. Between these two surfaces, one hundred and twenty carbon fiber ribs at 50cm intervals give the wing its aerodynamic profile.

PROPULSION SYSTEM

Four pods are fixed under the wings. Each contains a brushless, sensorless electric motor, a polymer lithium battery consisting of 70 accumulators, and a management system controlling the charge and temperature thresholds. The thermal insulation has been designed to conserve the heat radiated by the batteries and keep them functioning despite the -40 °C encountered at 8,500 meters. Each motor has a maximum power output of 10 HP. A gear box limits the rotation of each 3.5 meter diameter, twin-bladed propeller to 400 revolutions per minute. Over a 24-hour period the average power used is 8 hp, or 6 kW.

CENTRAL INTELLIGENCE

The on-board computing system gathers and analyses hundreds of flight management parameters, giving the pilot information to interpret for making decisions, transmitting key data via telemetry to the ground team and, above all, providing the motors with optimal power for the particular flight configuration and battery charge/discharge status.

Timeline

ACROSS AMERICA 2013: IN FLIGHT TO DALLAS

How does one prepare for a 20-hour flight in a solar airplane?

Flying a solar airplane is no easy task especially when one considers the size of the cockpit, which amounts to a meager 46 ft³ (1,3 m³)! Today’s Phoenix to Dallas flight, which will last approximately 18 hours, will also allow André to beat his previously established absolute distance world record in the solar ...

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Flying a solar airplane is no easy task especially when one considers the size of the cockpit, which amounts to a meager 46 ft³ (1,3 m³)! Today’s Phoenix to Dallas flight, which will last approximately 18 hours, will also allow André to beat his previously established absolute distance world record in the solar airplane category, achieved in 2012 during the flight from Payerne (Switzerland) to Madrid (Spain). The current flight will total 868 miles (1396.8 km).

But how does André stay focused and awake now that he’s only half way? Apart from being in great physical condition, the pilots also have to prove an extraordinary level of concentration and mental strength necessary to maneuver the unique and extremely lightweight solar aircraft during such long legs. In a cockpit devoid of an autopilot and dependent on the Mission Control Center (MCC) for flight route updates, André and Bertrand have to maintain a heightened level of focus throughout each flight.

The only way André could feel anxious before a flight is if he considered himself insufficiently prepared. Aware of this, every aspect of the flight is analyzed to the smallest detail. For example, the day before getting in the cockpit he closes his eyes and visualizes the first hours of the flight from take-off onward. He imagines all possible developments with different “what if” scenarios, even emergency ones, until he feels comfortable with the indications the Flight Director and his team have briefed him on that day. A final, shorter briefing is always given early in the morning the day of the flight to update the pilot on any potential changes.

André actively engages in Yoga, respiratory exercises and meditation. Yoga keeps his muscles flexible and comes in handy in the cockpit to maintain blood circulation. He regularly controls his breathing for many different reasons. For example, when he’s feeling a little tired he will start breathing faster to increase his energy level – an exercise he likes to do the day before a flight. But he will also control his breathing to relax. He does this by inhaling seven times and exhaling seven times bringing his heartbeat to a regular rhythm and allowing him to relax during calmer moments in the air. Finally, meditation is particularly handy the day before a flight, just before going to bed, to clear his mind from unnecessary thoughts ensuring a deep and restful sleep.

The Borschberg family is known to be fond of good food which explains why André doesn’t particularly like the few days preceding a flight. Don’t get me wrong, he’s ecstatic to know he’ll be soon in the cockpit again! The only downside is that he’s required to pay attention to his diet by completely cutting out aliments rich in fiber, like fruits and vegetables (see Brian’s funny video here to understand why). Even during the flight, André only brings snacks like cereal bars, nuts, dried fruits and maybe a sandwich, accompanied by water or a sports beverage.

With a growling stomach at the time of landing, transforming more into a lion’s roar during the ensuing press conference, it’s not surprising that André likes to indulge in a hearty meal – don’t forget to bring out those veggies!

ACROSS AMERICA 2013: PHOENIX TAKE OFF

A blessed take off

Solar Impulse has gracefully lifted off of Arizona’s soil at 04:47AM MST (UTC-7) on its way to Dallas Fort Worth International Airport. Landing is expected to occur tomorrow, Thursday May 23nd around 01:00 AM CDT (UTC-5).

Piloted by André, the solar airplane will be attempting to break the world distance ...

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Solar Impulse has gracefully lifted off of Arizona’s soil at 04:47AM MST (UTC-7) on its way to Dallas Fort Worth International Airport. Landing is expected to occur tomorrow, Thursday May 23nd around 01:00 AM CDT (UTC-5).

Piloted by André, the solar airplane will be attempting to break the world distance record in the solar airplane category, a record previously achieved by the same couple – Solar Impulse and André – when connecting Payerne (Switzerland) to Madrid (Spain) in 2012. The total estimated distance is 868 miles (1396.8 km). The third leg of the Across America mission, Dallas (TX) to St. Louis (MI), will be piloted by Bertrand.

What made today’s departure so unique was the presence of a Native American Medicine Man, Delmar Boni, of the San Carlos Apache Tribe. Dressed in traditional clothing with a beautiful crown of feathers partially covering his face, Delmar circled around the pilots, thumb painted yellow, while chanting a pleasant tune.  

He blessed today’s pilot, André, and the wings that will carry him on his journey to Texas. He also blessed his partner and project co-founder, Bertrand. There was something very soothing and mystical about this ritual. The tone of Delmar’s voice and the comforting flow of words he murmured, although incomprehensible to our ears, couldn’t be mistaken for anything other than a powerful blessing.

Today’s flight will be challenging because of the length - the longest distance ever flown by this aircraft - but it’s off to a good start: accompanied by America’s history and Native traditions, Solar Impulse is on its way to explore the future.  

ACROSS AMERICA 2013

Dallas, we’re ready!

Solar Impulse, piloted by André, will take off for Dallas (TX) tomorrow, Wednesday May 22nd at 4:3045AM MST (UTC-7) from Phoenix Sky Harbor International Airport. Landing is scheduled at 01:00AM CDT (UTC-5) at Dallas Fort Worth International Airport. Should ...

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Solar Impulse, piloted by André, will take off for Dallas (TX) tomorrow, Wednesday May 22nd at 4:3045AM MST (UTC-7) from Phoenix Sky Harbor International Airport. Landing is scheduled at 01:00AM CDT (UTC-5) at Dallas Fort Worth International Airport. Should there be any last minute changes, please consult our Dallas page on the Solar Impulse website.

The solar airplane and the team accompanying it were truly moved by the warm welcome they received in Phoenix – by the airport authorities, the public and political officials alike. But it’s time to move on and proceed with the next leg as people in other cities are waiting to welcome the solar airplane as well.

It is now André’s turn to take the commands of the solar airplane for this second leg, Phoenix to Dallas where he will attempt to break the world distance record in the solar aviation category, a record he previously set during the flight Payerne (Switzerland) to Madrid (Spain) in 2012. The total distance is estimated at 868 miles (1396.8 km). The flight from Arizona to Texas via New Mexico will provide André with some spectacular desert landscapes as he flies over Roswell (NM), where Felix Baumgartner completed the famous Red Bull Stratos jump from the stratosphere, towards Hobbs (NM) and then, on his approach to Dallas, above Abilene (TX). The third leg of the Across America mission, connecting Dallas to St. Louis, will be flown by Bertrand.

There are spaces available to come and see the airplane take off from Phoenix Sky Harbor tomorrow. Sign up here today if you want to see the solar airplane lift itself off the ground. Spaces are limited to a first comes first serves basis, so hurry up! If you would prefer to see the plane in flight, go to the butte on Arizona State University’s campus (in front of the Packard Drive bus stop at 6th street and Rio Salado Pkwy) – the plane will be visible with the naked eye.

As part of Solar Impulse’s Clean Generation initiative, meant to inspire and incite politicians, businessman and ordinary people to invest in clean technologies, the first flag displaying the initiative’s slogan and the destination city’s name, in the case Phoenix, was handed to the Governor of Arizona, Jan Brewer as a token of appreciation for her State’s hospitality. A new custom-designed flag will be brought in the cockpit from Phoenix to Dallas together with a USB key. The key virtually carries the names of Solar Impulse supporters across the United States. If you would like to be part of this pioneering adventure and cross the country with thousands of others, sign up today to become a friend of the project.

Don’t forget that Solar Impulse always films the entire mission flights live. Just go directly to Solar Impulse TV and see the pilots, one from the cockpit and the other from the ground, follow interviews with the people that make it happen and watch footage from past events and flights. Also on the live page, and during all flights, there’s a moving map and virtual cockpit allowing viewers like you to feel as if they too were in the cockpit

During the stopover in Dallas, the Solar Impulse team will organize an Open House on Friday, May 24th from 2PM to 7PM. Sign up here if you want to see the plane with you own eyes! Changes might occur so if you live in the Dallas area, stay tuned via our homepage or sign up to become a Supporter and get priority information about flights, events and more! 

2013 ACROSS AMERICA

Farewell and Au Revoir !

Fighting the glacial wind, known as the bise in this part of Switzerland, Solar Impulse’s team, Swissport and Cargolux employees together were able to load HB-SIA’s disassembled parts into Cargolux’s mastodon Boeing-747. The aircraft is already on its way for the United States and is expected to land ...

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Fighting the glacial wind, known as the bise in this part of Switzerland, Solar Impulse’s team, Swissport and Cargolux employees together were able to load HB-SIA’s disassembled parts into Cargolux’s mastodon Boeing-747. The aircraft is already on its way for the United States and is expected to land sometime around 12:30PM local San Francisco time on Thursday 21 February.

Never have I seen a cargo aircraft up close and the relatively small size of the Payerne runway made the Jumbo Jet look even more disproportionate. Several curious onlookers were present last night to watch the beast gently touch the tarmac and maneuver into its loading position.

We had a chance to visit the 747’s insides, including the top deck with the cockpit and passenger seating. I was reassured, our engineers and technicians are in good hands: the seats looked comfortable and passengers even have access to a miniscule room with a bed. I couldn’t stop thinking about how pleasant it must be to do a transatlantic flight devoid of crying babies, irritatingly narrow seating areas (making you feel more like a sardine when the person in front of you gets too comfortable), and annoying lines to use the restroom after lunch. One small detail that might be missing is a smiley young flight attendant to serve them a hot meal. But then again, we don’t want our trio getting too distracted now, do we?

Farewell, Au Revoir and best of luck on your new adventure HB-SIA!

2013 ACROSS AMERICA

The Giant’s coming

Tomorrow, 20 February 2013, Cargolux's impressive Boeing 747 (a.k.a. Jumbo Jet) will be landing at Payerne’s small military airfield. Scheduled to land between 4:45PM and 5PM, the loading will take place immediately thereafter with a departure the following day ...

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Tomorrow, 20 February 2013, Cargolux's impressive Boeing 747 (a.k.a. Jumbo Jet) will be landing at Payerne’s small military airfield. Scheduled to land between 4:45PM and 5PM, the loading will take place immediately thereafter with a departure the following day for Moffett Airfield at the Ames Research Center of NASA in San Francisco. Located at the heart of Silicon Valley, it’s the perfect place to start this year’s Across America mission.

Imagine, with the same wingspan as HB-SIA (64m) this aeronautical beast is 257 times the weight of Solar Impulse’s solar-powered airplane (1’600 kg vs. 412’770 kg)! The internal main deck will be stuffed with the dismantled HB-SIA and all the material needed to complete this spring/summer’s Across America mission, including the tools necessary for reassembly. This will leave enough room to squeeze in a few of our engineers and technicians somewhere between the fuselage and the tail boom for one, between the gondola crates and wing parts for the second and in front of the cockpit for the third…

Jokes aside; as much as we care about HB-SIA’s wellbeing, the three Solar Impulse team members have skillfully negotiated some fine business-style seating in the anterior part of the aircraft, avoiding an uncomfortable and frigid transatlantic flight to the faraway coast of California. They will be our watchdogs, ensuring the safety and handling requirements are followed during the unloading of this unique aircraft. 

2013 ACROSS AMERICA

Playing with Cranes

That’s it; there’s no turning back now – HB-SIA is slowly but surely looking less like an airplane and more like a scattered set of parts of an adult version toy mechanic.  The solar aircraft is getting ready for its USA adventure this spring!

This ...

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That’s it; there’s no turning back now – HB-SIA is slowly but surely looking less like an airplane and more like a scattered set of parts of an adult version toy mechanic.  The solar aircraft is getting ready for its USA adventure this spring!

This week the gondolas, vertical and horizontal stabilizers and the wings were entirely dismantled leaving a skimpy skeletal version of a solar airplane alone inside the vast hangar. The greatest challenge the team faced was when they detached the impressive 64m by 710kg wings from the aircraft’s body - the fuselage.

The wings are secured to the fuselage by five metallic rods. The rods are sleek and are meant to pop out when there is no load or pressure on them; but to achieve this, two cranes had to gently and simultaneously lift the wings until the rods were released. There is really no way of knowing exactly when the rods will let go of their solid grip and the process has to be done slowly and with no time constraints. Silence reigned in the Payerne hanger while two engineers had all their attention dedicated to the rods, patiently awaiting the moment of their disengagement.

The same process is required to undo the wings into three separate parts, but this exercise didn’t require the cranes, making it somewhat more manageable.


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