Simulation Is Critical for Solar Impulse, Sustainable Flight

Simulation plays a huge role in Solar Impulse’s world-crossing, sustainable plane.

Late last year, Solar Impulse shocked the world by circumnavigating the globe in a solar-powered airplane. The craft, called Solar Impulse HB-SIA, achieved a number of feats during its ’round the world journey, but its most impressive accomplishment may have been flying for 26 hours nonstop only using energy it generated from the sun.

Today, the Solar Impulse team is still hard at work pushing the envelope of sustainably powered flight by developing its next-generation craft, the HB-SIB.

Throughout the process of developing the SIA and now, in its development of the SIB, Solar Impulse’s engineers have relied on simulation software to direct their design. In fact, throughout every stage of the SIA design process, Solar Impulse engineers relied on MATLAB and Simulink software to provide critical insight into the aerodynamics, handling and mission development of their project. 

“Simulations with MATLAB and Simulink were essential to assessing feasibility and evaluating broad design tradeoffs as well as making detailed design decisions—such as the size of control surfaces and the vertical tail—that directly affect aircraft dynamics and handling qualities,” said Ralph Paul, Solar Impulse’s head of flight dynamics.

To begin with, the Solar Impulse team used Simulink to build a system model of their aircraft, including its structural properties and subsystems such as the craft’s lithium batteries. Leveraging this system model, Solar Impulse’s designers found that their flying machine would require massive 80-meter wings, a nonstarter for the Solar Impulse team. After engineers reconfigured their model and reran simulations, the craft’s wings were reduced to 64 meters, a length that better suited manufacturing parameters.

Moving forward, the team also turned to Simulink to better understand how the flyer’s dynamics would affect its aerodynamics and control. With these elements coded into Simulink, the fuselage, gearboxes and other critical systems of the SIA’s design were fine-tuned to create the most efficient craft possible.

Finally, Solar Impulse used MATLAB to develop algorithms that could analyze flight data. With MATLAB results in hand, engineers were able to refine the SIA’s dynamics models, estimate sensor errors and improve air data computer algorithms. With these data refinements in place, Paul and his team could turn back to Simulink to develop a realistic flight simulator that instructed pilots on how to react to the SIA’s idiosyncrasies. 

“When the pilot turns the yoke to execute a turn, the aircraft’s nose initially moves up to 10 degrees in the opposite direction,” said Paul. “Our simulations predicted this, but more importantly, the flight simulator that we built with Simulink enabled our pilots to learn how to manage this counter-intuitive behavior, especially for the final phase of the landing.”

Today, Solar Impulse’s team continues to use MATLAB and Simulink technology to further their designs.

Could Solar Impulse’s pioneering ideas lead to breakthroughs in sustainable flight and impact the millions of passengers crisscrossing the globe each day? Tell us what you think in the comments section below.