At 07:12 Abu Dhabi time (03:12 GMT) Andre Borschberg took off on the first leg of a round-the-world flight in a solar powered plane, Solar Impulse 2. First stop Muscat, Oman, 12 hours away. The aircraft is single seat — Borschberg will be alternating pilot duties with fellow Swiss, Bertrand Piccard.
Part of the journey will be at night. Crossing the Pacific, between Nanjing (China) & Hawaii, is projected to take 120 hours (5 days) non-stop. With only one source of energy, the Sun, it is essential to store electricity in the 633 kg of lithium ion battery during the day, to power the plane at night.
Inherent in an aircraft, is another energy storage system: altitude. In addition to charging the battery, the plane will climb during daylight to around 3,000 metres (10,000 feet). At night, energy stored in the battery can be supplemented by allowing the aircraft to glide to a lower altitude. This works well in the Solar Impulse 2: it has been designed on sailplane principles & so has a glide ratio over 40 (how many metres it moves forward for each metre of altitude it loses)¹. At that glide ratio, 3,000 metres of altitude can be turned into 3,000 * 40 = 120,000 metres = 120 km (74.5 miles) of forward progress.
By contrast, a Boeing 747, with a glide ratio around 12 moves forward 3,000 * 12 = 36,000 metres = 36 km for a loss of 3,000 metres².
Update: 06 April, @solarimpulse tweeted: "#Si2's pilot climbs up to the height of Mt. Everest, 8,500 m (28,000 ft), in an unpressurized cabin!" At a glide ratio of 40, 8,500 metres = 8,500 * 40 = 340,000 metres = 340 km = 211 miles.
http://www.theguardian.com/environment/2015/mar/08/swiss-pilots-attempt-worlds-first-around-world-solar-flight
http://www.bbc.com/news/science-environment-31772140
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¹ "Gliding flight" https://en.wikipedia.org/wiki/Gliding_flight#Examples
² "747 Family Technical Characteristics" http://www.boeing.com/boeing/commercial/747family/pf/pf_400_prod.page / Swiss pilot pilots first ever attempt fly around the world propelled the Sun André Borschberg compatriot Bertrand Piccard take turns piloting single seater seat Solar Impulse 2 21,747 miles 35,000 km kilometre 12 legs including gruelling five- to six-day stints across the Atlantic Pacific oceans entire journey will take five months Borschberg took the controls takeoff take off take-off Al-Bateen executive airport Abu Dhabi early on Monday first destination Muscat in Oman pilots roughly 250 hours each inside narrow cockpit no oxygen temperature control temperatures outside range between -40 degrees C to 40°C falling asleep flight need constant attention Piccard Borschberg survive 20-minute naps every two to four hours pilots will practise yoga stave off the physical discomfort remaining confined seat for days at a time Borschberg biggest challenge maintaining concentration Piccard psychiatrist team 1999 first circumnavigated globe non-stop balloon taught techniques of self-hypnosis meditation maintain concentration time duration in the present moment the only way is to be present almost a spiritual experience entire journey circumnavigating Earth in a family car aircraft weighs the same as a Volvo sedan comparable speeds SI2 top speed 87m/h 140km/h pilots conserve battery power limiting plane half cockpit only slightly larger average car contain life support systems food oxygen supplies reclining pilot’s seat triples bed chair toilet fly both day and night no fuel powered by 17,000 solar panels set on its wings wider Boeing 747’s fuselage 633kg bank of lithium batteries quarter weight store energy run motors overnight journey early days intercontinental flight enormous speed range jet engines Qantas fly Kangaroo Route Sydney to London hopping Darwin Singapore Kolkata Karachi Cairo Tripoli en route Borschberg success Solar Impulse project first solar-powered plane fly through the night first to fly between two continents primitive step toward zero-carbon jumbo combustion fossil fuels dominated powered flight 19th century dirigible aviation burns the most carbon per passenger per kilometre of any mode of mass-transport and, despite efforts to limit emissions, remains the fastest growing anthropogenic source of greenhouse gases sector climate change toughest major emissions source to decarbonise solar flight seeks remains decades away Wright Brothers Charles Lindbergh deputy editor Aerospace magazine Bill Read solar flight commercial flights solar cells generate power fly Solar Impulse fly using solar power constructed very light weight light-weight lightweight huge wingspan solar cell technology power source aircraft advances project real-world uses today fly Sun day and night build an aircraft extremely energy efficient technologies energy efficiency used in your home your car appliances four motors power aircraft generate heat energy efficiency single cheapest way reduce carbon emissions across the world technologies challenge energy environment pollution natural resources /
