The need for sustainable energy is something the world cannot ignore. As our demands for power increase, the problems with fossil fuel use become more apparent; not least of which are climatic effect and a finite supply...

Despite a significant state actor pulling out of the Paris Accord it is an undeniable fact that carbon emissions need to be drastically reduced. We have now been promised a carbon neutral UK by 2050 and if this commitment is to stand any chance of being fulfilled, we need to act now. Renewable energy, such as solar, is one of the few viable solutions.

An example of Solar Power panels

By coincidence the watch world has been well ahead in the energy game for years with the pioneering use of solar power. Two watches in my collection have never needed a new battery and have never stopped, one in over 15 years of ownership. They are a Citizen Pro-Master Tough Ray Mears and a Casio AQ. Both are very clever machines aimed at different markets, but the Casio’s newer technology takes the concept to a higher level. It reaches maximum power storage in a matter of hours and retains a charge that will last 10 months if left in darkness.

The dual digital/analogue system has a smart sequential shutdown mechanism, initially blanking out the digital screen overnight. After two days of no exposure to light the hands lock at the 00:00hr mark but crucially a chip retains the time. When exposed to light the watch immediately resets itself. It is impressive tech but these are small machines and the transfer to technology to large platforms, such as solar powered family cars, is a distant dream.

The Citizen Pro-Master Tough fitted to the Canvas NATO - Image Credit: WatchGecko Online Magazine

Aircraft are a substantial contributor to CO2 pollution depositing about 12% of our carbon trail in the skies above. This is a relatively low number when compared to land vehicles which make up 74% of CO2 but in 2009, we saw a machine which was so radical, so revolutionary, that it could one day change the way we fly forever. It was called SOLAR IMPULSE.


Solar Impulse is a Swiss based experimental solar-powered aircraft project. Between 2009 and today they have developed and flown two incredible machines, Solar Impulse 1 and 2, or HB-SIA and HB-SIB to give them their formal titles. Spearheaded by the Swiss engineer André Borschberg and flown by the famous balloonist Bertrand Piccard, who was famous for piloting the Breitling Orbiter 3 balloon in a non-stop circumnavigation. Solar Impulse’s primary objective was to circumnavigate of the Earth in a fixed wing aircraft using only solar power and to use this achievement as a platform to highlight what is possible.

Solar Impulse 1 and 2 were single-seated monoplanes with a forward cockpit and a tiny cabin in the back for the alternate pilot to rest in. Both aircraft were powered by photovoltaic cells. The aircraft is fully independent with regards to power and can take off, fly and land under its own self-generated solar electricity. Solar Impulse 1 was effectively a test bed for the technology, similar to the early Apollos which were never built to fly to the Moon. Solar Impulse 1 was designed to remain airborne for up to 36 hours and it had its maiden flight in December 2009.

Critical technology and performance had to be thoroughly tested before the planned Solar Impulse 2 mission could even be considered, such as flying at night when the aircraft could not recharge. No one knew if it could retain enough power to remain airborne. In July 2010 HB-SIA flew for a full 26 hours non-stop. In what is known as a full diurnal cycle, this flight included almost nine hours of flying in darkness. The flight was a success and lead to further test flights for Piccard and Borschberg in different environmental locations to test for compatibility and potential problems with the aircraft in heat and cold – these experiments being held in Switzerland and Morocco respectively in 2012.

Flea Hop HB-SIA Solar Impulse - Image Credit: Matth1 / CC BY-SA

2013 saw a year of analysing the myriad of data collected from HB-SIA and construction began on the aircraft which would attempt the circumnavigation.

In 2014 Solar Impulse 2 (HB-SIB) was unveiled weighing in at only 2.3 tons and having a huge wingspan of 72m, the same as a 747. With total wing solar panel coverage, the 17000 advanced power panels could only be 135 microns in thickness to maximize the power to weight ratio of the aircraft.

HB-SIB had four propellers which each generated 17.4 hp. These were fitted under the giant wings in a traditional position and pioneered a revolution reduction gear limiting the rotation of speed of the 4m propeller to 525 rpm. The aircraft could fly at 36 km/h at sea level and 140 km/h at a maximum service ceiling of 8500m.

Solar Impulse - Image Credit: Anthony Quintano / CC BY

The Journey

In January 2015 the aircraft was delivered to Masdar City in Abu Dhabi for the World Future Energy Summit. Masdar City is a “future” city in the UAE which is wholly powered by renewable energy and wind. It was constructed to show what was possible and is a big tourist attraction in the Emirate. Major tech companies such as Siemens now have their Middle East HQs in Masdar. No cars are allowed in Masdar, instead electric pods transport the public on pre-laid electric paths to various locations from programmable touch pads in the cars. It was a fitting location to launch the aircraft.

HB-SIB finally took off on the 9th March 2015 from the Al Bateen Executive Airport which is in the heart of the city. Although the airport was closed to the public there were many areas to watch the runway and it was an unforgettable moment to see this huge machine silently take off powered only by the sun.

Solar Impulse 2 was scheduled to return to the same runway in August 2015 after circumnavigating the world in 17 hops. A NASA style Mission Control for the flight was established in Monaco, utilising satellite up links to show real-time flight data and remain in constant contact with the aircraft crew and the support team.

Solar Impule - Image Credit: Dominique Mollicone / CC BY-SA

The journey took Piccard and Borschberg from the UAE to Oman, India, China, Japan, USA, Spain, Egypt and back to UAE. The longest flight was 117 hours which covered the leg from Nagoya in Japan to Hawaii. To date the world’s longest solar powered single flight. The shortest segment of 4 hours was internally in the USA from Philadelphia to New York.

By May 2015, HB-SIB was over Japan and made an unscheduled stop as bad weather over the Pacific made flying unsafe. During the 117-hour leg the plane's batteries overheated because they had been packed in too much insulation allowing excessive heat accumulation. The plane was then grounded in Hawaii awaiting spares.

New batteries were made and installed in the plane. These had to be fully tested in flight which lead to a frustrating delay in the early months of 2016, but the journey resumed in April with the plane finally landing in mainland USA in California. During that flight, Piccard spoke from the cockpit via satcom with the UN Secretary General Ban Ki-Moon before the General Assembly of the United Nations, commenting on that day's historic signing of the Paris Agreement. Such irony that in 2019 the US would pull out of the same agreement. Solar Impulse 2 finally touched down in Abu Dhabi on 26 July, to international acclaim, completing the trip in 16 months.


The impact of the HB aircraft cannot be underestimated but none of it would have been possible without the significant contribution from Omega Watches. Not only were unique Speedmaster's designed for the crew but Omega funded, developed and made many of then highly sophisticated components in both aircraft.

OMEGA’s contributions to Solar Impulse included:

The landing light system, which weighed one kilogram, with an advanced “watt to weight” ratio which illuminated the landing area.

On the aircraft flight panel, the “OMEGA Instrument”, designed by ESA astronaut Claude Nicollier, indicated flight path and alerts the pilot if the wing angle exceeded the normal limit.

HB-SIB was equipped with Omega energy dispatchers on each wing which deployed bi-directional functionality to ensure that either gondola battery could support the other in the event of an engine failure.

Solar energy is used to power the instruments in the cockpit through high-voltage batteries in the plane’s cockpit. An Omega DC-DC Converter converted the energy from the batteries to a low voltage (28V) so that the plane’s cockpit electronics can also function with solar energy.

The “Omega Instrument” would initiate a vibration panel in the sleeve of flight crew suit in the presentation of important information and the OMEGA “Buzz” was a timer which could be set by the pilots to emit a loud noise every 20 minutes so they would not fall asleep at critical times.

Solar Impulse - Image Credit: Milko Vuille / CC BY-SA


It goes without saying that the pilots of these aircraft had to wear Omega watches given the company’s significant involvement in the project. Acknowledging the parallels to pioneering space flight the Speedmaster was the obvious choice.

The Omega Speedmaster fitted to the Kington Short Dress leather strap - Image Credit: WatchGecko Online Magazine

For HB-SIA, possibly the most stunning Speedy of all time was developed - Omega reference 321. It was, and still is, the only classic dial Speedmaster to be made of titanium. These specially numbered series watches had a fourth GMT hand and paid tribute to the Solar Impulse project. The watch featured a brushed titanium case with polished finished bevel edges. The case sat on a similarly brushed titanium bracelet with polished centre links. The dial was a unique black carbon fibre design.

The hands and indices were white and bolder than the standard watch and the GMT/24 hour function used a distinctive white aircraft tipped black & orange hand with the following orange text "NORTH GMT". Unlike the Professional Moonwatch there was a date window located between the 4 & 5 o'clock position.

The Omega HB-SIA Co-Axial GMT Chronograph (ref. 321. - Image Credit: Omega Japan

The deeply coloured and beautifully embellished case back featured the first Solar Impulse mission patch and was inscribed "OMEGA SOLAR IMPULSE HB-SIA - 100m/330FT - CO-AXIAL - CHRONOMETER - TEST - FLIGHT - No. 1234".

An Omega automatic calibre 3603 was fitted with a friction-reducing Co-Axial escapement for greater precision & durability. Beating at 28,800 vph the movement had an approximate 55-hour power reserve. There does not appear to any definitive information on how many of these watches have been or will be produced. It is still “live” on the Omega website but trying to find one is very hard and for collection purposes this gem is normally referred to in the past tense.

For the flight of HB-SIB Omega went in a totally different direction and produced a special edition of the X-33 Skywalker for the crew.

The watch is made of grade 2 titanium and weighs less than 60 grams. With a blue ceramic bezel circumnavigating the digital dial and Super Luminova coated indexes it offered supreme legibility for the pilots. The watch came with a unique Omega blue and green NATO strap which had Solar Impulse engraved on the retention bars. The set was limited to 1924 pieces in commemoration of the year the first aircraft flew round the world piloted by a crew from the American Army Air Service.

Like the standard European Space Agency X-33 the HB-SIB watch was powered by Omega’s quartz calibre 5619. It offered all the same highly advanced features such as a program to allow the crew to measure Mission Elapsed Time (MET). MET is, as the name implies, the time since commencement of a mission; in this case the entire circumnavigation of the globe. The watch had a sub-program to measure the time of each leg (which was developed for recording EVA times on space stations). The MET stopwatch on the X33 is unique as it can run into days, therefore is suitable for prolonged flight measurement.

The case back still carried the ESA selection certification but was less striking than the MB-SIA watch with a simple, uncoloured, engraving of the aircraft and the words “SOLAR IMPULSE – AROUND THE WORLD”. The watch is no longer advertised on Omega’s website, but pre-owned models can be found sub £3000.

Both the Solar Impulse Speedmasters are in their own way stunning watches. They seem perfectly suited for the incredible achievement of MB-SIA & B aircraft and their crews. Like the Apollo missions before them the Omega Speedmaster has become an integral part of yet another of mankind’s greatest technical feats. Whether an Omega will walk on the Moon again is certainly up for conjecture. Anyone who has followed my Geckota blogs will know I am a huge Apollo enthusiast but even I must admit that the Moon missions in the 60s and 70s perhaps seem a little archaic now and were most certainly a product of the Cold War.

Solar Impulse - Image Credit: Energy Gov

However, on a planet desperate for renewable and clean energy, the Solar Impulse flights are more relevant than ever and highlighted to the world not only the technical wonder of the project and what could be possible but the fact that real prolonged flight was possible without using so much as a drop of fuel. For sure the HB-SIA/B machines are years away from any form of commercial viability such as passenger or freight carry but they must surely pave the way for the continued study of this key technology which could one day make air travel something we can use forever.