How does Solar Impulse 2 use inflight connectivity?

Solar Impulse 2
Solar Impulse 2

“Get Connected’s” Steve Nichols was recently invited to visit the Monaco-based Mission Control Centre (MCC) for “Solar Impulse 2” – the solar-powered aircraft attempting to be the first to fly 35,000km right around the world.

The trip was to see how Inmarsat’s SwiftBroadband (SBB) satellite-based inflight connectivity, coupled with SITAONAIR’s expertise, is helping the flight’s organisers keep in touch with the lightweight craft that is powered only by the sun.

Solar Impulse 2, tail number HB-SIB, started its round-the-world-flight from Abu Dhabi in March 2015.

HB-SIB uses SITAONAIR satellite connectivity for pilot voice and data communications, as well as operational applications such as live weather updates and real-time aircraft monitoring.

A thousand or so sensors on the aircraft send a constant stream of data back to the MCC during the flight, including power, temperature information, and performance data covering every piece of equipment.

The system also allows the public to experience the flights real-time via a video stream (visit the Solar Impulse YouTube channel) and messaging on social networks.

Inmarsat SBB

SITAONAIR provides Solar Impulse HB-SIB with Inmarsat SBB-based satellite services. The airborne and ground infrastructure was designed specifically for the aircraft by Solar Impulse’s Official National Partner, Swisscom.

The aircraft has generated gigabytes of background IP data and hours of streaming IP data since its initial departure from Abu Dhabi. This data comprises messages from the 1,000 plus sensors covering the aircraft from cockpit data, from voice communications over IP and also from live streaming video when the pilot, either Bertrand Piccard or Andre Borschberg, talks to the media via the onboard GoPro camera.

The sensors cover everything from the temperature of each of the battery cells and the electric motors, strain gauges, accelerometers and oxygen sensors in the cockpit.

Mission engineer Michael Anger said: “We can get sensor updates via the Inmarsat satellites up to 10-50 times a second. To save bandwidth some sensors only transmit data if their values change. The data link has proved to be very reliable and we have only had the odd data dropout lasting just a second or so. It has been very impressive.”

Biometric monitoring is also important. The team in Monaco can measure the pilot’s vital functions, including pulse rate and blood/oxygen saturation. A medical expert is on hand during every flight.

SITAONAIR estimates that the entire mission will generate about 18,000 minutes of mobile telephony, around 400 mins of live video streaming and 400Mb of live video calls.

It also estimates 4Gb of photographic data from the aircraft and up to 140 minutes of weather data to the aircraft will have been transferred by the time Solar Impulse 2 gets back to Abu Dhabi.

The telemetry is sent back to the MCC where it is displayed on multiple consoles so that the team can monitor, not only the aircraft’s attitude and position, but also the all-important energy parameters including battery voltages, temperatures and charging status.

The inflight connectivity system has also made it possible to organise landing permissions at unplanned airfields and enabled constant contact between the Solar Impulse 2 base team, the aircraft’s pilot and air traffic control.

Swisscom

Swisscom engineers spent a year devising the communications solution. The airborne element is very light and is designed to use as little power as possible, while providing uninterrupted connectivity.

Its airborne SwiftBroadband satcom terminal was prepared for Swisscom by Cobham in South Africa who stripped it down to its bare essentials.

The big issue was equipment weight. Swisscom/Cobham made an SBB mid-gain special by stripping off all casings and connectors, and making an antenna out of foil and without a radome (the aircraft itself is the radome).

The lightweight system was based on a Cobham SATCOM SB300 class 7 SwiftBroadband system, offering both voice and data.

The total weight came in at about 5kg and it uses about 50W of energy. There is also an Iridium satellite back-up system.

Telemetry screens at the Solar Impulse control centre in Monaco.Solar Impulse 2’s route has so far taken it from Abu Dhabi to Oman, India and China. It then crossed the Pacific via Hawaii, and has flown across the US. It is currently at JFK airport, New York City after flying there from Pennsylvania last week.

After crossing the Atlantic, it will then either stop-over in southern Europe or North Africa, depending on conditions, before returning to Abu Dhabi.

Michael Anger said: “The Atlantic crossing will be more challenging than the Pacific leg. The weather and turbulence will be more demanding.

“The aircraft is more efficient when flying at lower altitudes due to the air density, but obviously it is better to fly above the clouds in terms of the solar power.

“A typical night-time minimum flight height might be 3,000ft, but during the day it would be more like 28,000 ft,” said Anger.

Solar Impulse 2

Julie Conti, of the Solar Impulse 2 PR team, said: “The actual route will depend upon the weather, but it has to be back to Abu Dhabi by October before the winter. The team is aiming for the end of July.”

Solar Impulse 2 is a single-seater aircraft made of carbon fibre that has a 72m / 236ft wingspan (larger than a Boeing 747) for a weight of 2,300kg / 5,100lb (the equivalent of an empty family car). The 17,248 solar cells built into the wing power the four batteries (38.5kWh per battery) that in turn power the four electric engines (13.5kW / 17.5hp each).

The solar cells are about 23-24% efficient in terms of converting the sun’s 240W per square metre light energy that falls upon them. And they are old technology.

Engineer Yves Heller (right) said the cell and lithium polymer battery technology was actually chosen four years ago – and the world has moved on since then.

“If we were to build Solar Impulse 2 today it would be even more efficient,” he said.

The aircraft has already broken eight world records, has flown for nearly 400 hours and 30,000 km in 14 legs.

With no true auto pilot, Andre or Bertrand can only power nap for 15 minutes before the ground team needs to wake them up. But that didn’t stop the aircraft flying non-stop for five days and nights for the Pacific crossing.

The Solar Impulse 2 story is not science fiction, but really more about “science future”. The project aims to educate the world as to the possibilities offered by carbon composites and solar technology. As its web site says, it is “inventing the future”.

Keep on eye on the team’s website for the next instalment.

  • Get Connected’s Steve Nichols presented a video for “Arabian Aerospace” on how Solar Impulse is using Inmarsat SwiftBroadband, SITAONAIR and Swisscom technology to keep in touch with its Monaco-based HQ. 

Solar Impulse website: www.solarimpulse.com

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