Solar Impulse 2

Updated by Bill Lofton 4/29/16


Courtesy of SOLAR IMPULSE on YouTube
 

The Solar Impulse 2 (SB-SIB) is a proof-of-concept series hybrid (solar) motorglider developed from the Solar Impulse 1 (SB-SIA) for improved record-setting flight under solar power.

The easiest way to distinguish the two aircraft is by location of the motor nacelles: on Solar Impulse 1, the two motor nacelles on each side of the fuselage are far apart, whereas on Solar Impulse 2, they’re close together.

Also, the tail booms are distinctive: on Solar Impulse 1, the tail boom height is about 1/2 of the height of the fuselage under the wing, whereas on Solar Impulse 2, the tail boom height is about 3/4 of the height of the fuselage under the wing and the tail boom height is tapered aft.
 

Both Solar Impulse 1 (SB-SIA) and Solar Impulse 2 (SB-SIB) are featured in this video

 

Solar Impulse 2 Background

The Solar Impulse project was created by Bertrand Piccard and André Borschberg with the goal of flying around the world under solar power. The Solar Impulse 1 was intended as a testbed that would enable a second aircraft to achieve the circumnavigation goal.

Project team: (per Wikipedia)

  • 50 engineers and technical specialist from 6 countries
  • 100 outside advisors
  • 80 technological partners

Project partners:

Project timeline: (per Wikipedia)

  • November 2003: Solar Impulse project initiation
  • 2004-2006: Concept development and simulations
  • 2006-2013: Solar Impulse 1 development and flights
  • 2011-2013: Development of the Solar Impulse 2 airplane (registered HB-SIB)
  • June 2, 2014: Maiden flight, in Switzerland
  • March 9, 2015: Initiation of round-the-world (multi-leg) flights starting from Abu Dhabi
  • June 1, 2015: completed flights across Asia
  • July 3, 2015: completed flight from Japan to Hawaii
  • February, 2016: Initiated maintenance test flights in Hawaii
  • April 23, 2016: completed flight from Hawaii to California

The Solar Impulse 2 suffered battery damage from overheating (due to excessive insulation) during the Japan-Hawaii flight in July 2015. Per the Solar Impulse blog, new battery packs were built and installed in Hawaii. Also, the pilot now has direct control to open and close battery cooling vents in event of automated system failure.

Check the Solar Impulse blog for latest status.
 

Where do you store an airplane this big when an airliner hangar isn’t available? In your mobile hangar!

Courtesy of abb-conversations
 


Courtesy of ABB on YouTube
 

Intro to Solar Impulse 2

Solar Impulse 2 features:

  • Carbon fiber/honeycomb composite airframe
  • Single seat in non-pressurized cockpit
  • Solar cells cover wings, fuselage, and horizontal stabilizer
  • 4 motors and battery packs
  • main gear swivels to enable “crabbing” into wind during takeoff run and landing roll (per Wired)

 

“crabbing” to landing with strong crosswind


Courtesy of SOLAR IMPULSE on YouTube
 

Solar Impulse 2 specs:

  • Length: 22.4 m (73.5 ft)
  • Height: 6.4 m (21.0 ft)
  • Wingspan: 72 m (236 ft)
  • Wing area: 271 m2 (2917 ft2)
  • Mean chord: 3.76 m (12.30 ft) (271 m2 wing area / 72 m wingspan)
  • Aspect ratio: 19.1 (72 m wingspan / 3.76 m mean chord)
  • Loaded weight (includes pilot): 2300 kg (5071 lb)

Solar Impulse 2 performance:

  • Max speed: 83.4 km/hr (51.8 MPH, 45 knots)
  • Stall speed: 37 km/hr (23 MPH, 20 knots)
  • Max altitude (in daily flight profile): 8500 m (27888 ft)

 

fuselage structure

Courtesy of SOLAR IMPULSE on YouTube
 

cockpit


Courtesy of SOLAR IMPULSE on YouTube
 

four throttles

Courtesy of SOLAR IMPULSE on YouTube
 

Solar Impulse 2 vs. Solar Impulse 1

Solar Impulse 2 has:

  • More powerful solar system
  • More powerful motors and controllers
  • More powerful and higher energy capacity battery packs
  • Battery cells changed from Li-ion to Li-S (higher specific energy)
  • Larger wing
  • Larger tail boom with triangular cross section (was square)
  • Outer motor nacelles moved closer to fuselage

 

Solar Impulse 2 Solar Power System

Solar Impulse 2 Solar Power System features:

Solar Impulse 2 Solar Power System specs:

  • 17,248 SunPower solar cells with 23% efficiency (before covering with waterproof coating), 135 microns thick

Solar Impulse 2 Solar Power System performance:

  • Solar panels area: 269.5 m2 (2901 ft2)
  • Rated solar power: 66 kW (per Wikipedia)
  • Daily energy generation: up to 340 kWh
  • Rated power hours per day: 5.15 (340 kWh / 66 kW)

 

solar panels everywhere


Courtesy of SOLAR IMPULSE on YouTube
 

building and installing solar panels


Courtesy of SOLAR IMPULSE on YouTube
 

solar panel construction

 

Solar Impulse 2 Electric Propulsion System

Solar Impulse 2 EPS features:

  • Four motors and controllers

Solar Impulse 2 EPS specs:

  • Motor efficiency: 97%

Solar Impulse 2 EPS performance:

  • Motor peak power: 13.0 kW (17.4 HP)
  • Total motors peak power: 52 kW (69.7 HP) (total of 4 motors)
  • Average flight power over 24 hours: 11.2 kW (15 HP) (total of 4 motors)

 

nacelle without fairing and nacelles with fairing


Courtesy of SOLAR IMPULSE on YouTube
 

assembling a nacelle


Courtesy of solarimpulse.com

 

Solar Impulse 2 Propeller

The Solar Impulse 2 has four 2-blades propellers.

Propeller features:

  • Carbon fiber and foam composite construction
  • Teetering mount

Propeller specs:

  • Propeller diameter: 4.0 m (13.1 ft)
  • Propeller normal operating speed: 200-400 RPM
    • Takeoff propeller speed: 420 RPM
    • Climb propeller speed: 340 RPM
  • Propeller max speed: 525 RPM (as limited by max motor speed and reduction gear)
  • Propeller weight: 5.0 kg (11 lb)

 


Courtesy of Milko Vuille on Wikimedia Commons
 


Courtesy of solarimpulse.com
 

teetering mount

Courtesy of SOLAR IMPULSE on YouTube
 


 

Solar Impulse 2 Battery System

Solar Impulse 2 Battery System features:

  • Custom Kokam li-ion battery cells
  • ? Lithium-sulfur (Li-S) battery chemistry?
  • Four battery packs (one per motor, located behind motor in nacelle) built by Air Energy in Germany
  • A balancing controller can transfer power between batteries in event of a motor or controller failure (per Battery Bro)
  • Battery boxes have high density foam insulation
  • Thermal management system heats batteries to 25 degrees C (per Battery Bro)
  • Pilot has direct control to open and close battery cooling vents in event of automated system failure (per the Solar Impulse blog)

Solar Impulse 2 Battery System specs:

  • Battery pack voltage range: 210-304 V (per Battery Bro)
  • Total battery weight: 633 kg (1396 lb) (4 battery packs, 1 battery pack per motor))
  • Battery pack weight: 158 kg (349 lb) (each 1 of 4 battery packs)

Solar Impulse 2 Battery System deduced specs:

  • Battery pack series cell configuration: 72s (304 V pack max voltage / 4.2 V NMC cell max voltage)
  • Battery pack max voltage: 302 V (4.2 V * 72s)
  • Battery pack nominal voltage: 266 V (3.7 V * 72s)
  • Battery pack charge capacity: 154 Ah (41000 Wh / 266 V)

Solar Impulse 2 Battery System performance:

  • Battery pack energy: 41 kWh (1 battery pack per motor)
  • Total battery packs energy: 164 kWh (4 battery packs)
  • Battery pack specific energy: 260 Wh/kg (per Air Energy) also (41000 Wh / 158 kg = 259 Wh/kg)
  • Battery endurance at motor peak power: 3.15 hours (41 kWh / 13.0 kW)
    (motors can’t be run at peak power for hours without overheating)

 

installing a battery pack in nacelle

Courtesy of solarimpulse.com
 

Solar Impulse 2 Press, Other Info, and Videos

Solar Impulse 2 press and other info:

Solar Impulse 2 videos:

 


Courtesy of SOLAR IMPULSE on YouTube