Improving solar sail controllability: Alesia Herasimenka wins the L'Oréal-UNESCO 2023 Prize

Alesia Herasimenka's work is at the heart of the current search for new types of propulsion to enable more space missions to be carried out at lower cost. Large, expensive satellites powered by chemical engines are increasingly being replaced by smaller, less expensive satellites (CubeSats), affordable by universities, laboratories or even private companies. If sailboats use the wind to propel them across the water, solar sails use sunlight to propel spacecraft into space, at speeds that would be virtually impossible for chemical rockets to reach.

This is the theme of his thesis work: sails propelled by sunlight, giving them an infinite source of energy. Nevertheless, these satellites pose many difficulties in terms of control, as they can only go in the opposite direction to the Sun.  First, Alesia Herasimenka analyzed the controllability of a solar sail around a planet or an asteroid, formulating a minimum optical requirement for controllability. This requirement does not depend on the gravitational attraction of the body around which the sail is orbiting, so it can be used when designing future missions. She was able to demonstrate that fairly reflective solar sails, relying on the gravitation of the planets or the Sun, are capable of performing any desired maneuver.

The second part of her research focused on the optimal control of solar sails. She has also developed advanced, robust control algorithms to optimize the trajectories of the sails, thereby considerably improving performance by exploring the achievable limits of the system's performance.

While space missions have almost always been limited by the amount of fuel that can be carried on board, the practical applications of Alesia Herasimenka's work open up a whole new range of possibilities for exploring the farthest reaches of the Universe. Indeed, as the principle of solar sails is based on the pressure of light, they open up a whole range of new space missions to study our solar system.

What's more, the continuous acceleration due to light would enable the sails to reach very high speeds, up to 7 astronomical units (an astronomical unit is the distance between Earth and Sun, i.e. 149.6 million kilometers) per year, which could enable us to send satellites to very distant regions or even beyond our solar system.

Her role model? Ever since she was a child in Minsk, Belarus, she's dreamed of following in Marie Curie's footsteps. She was delighted to have been able to follow in Marie Curie's footsteps in her university career, studying at the Sorbonne in Paris.

Alesia Herasimenka believes in teamwork. "The more different people are in a team, the more ideas are born and realized". She is convinced that women possess qualities that are indispensable to science, and must hang in there all the more as the competition is tougher for women than for men, but "the role of women in science is extremely important".

The L'Oréal Foundation's "Women in Science" program encourages women to pursue a career in science, and to feel they have a right to do so. She makes hers this quote from Marie Curie: "we never pay attention to what has been done, we only see what remains to be done". And she recognizes the importance of being encouraged throughout her career, and of receiving positive feedback.

While she takes her scientific vocation for granted, she calls herself lucky. "I haven't had any particular difficulties because I'm a woman. On the other hand, I often get noticed, especially at conferences where sometimes I'm the only woman in a room full of scientists. But I take it more as a challenge and it motivates me even more to show that a woman can be very strong or even the strongest in her field, while staying loyal to herself. And I'm very happy at every opportunity to be able to prove it."