Balloon-lifted capsule offers passengers a 'balcony' at the edge of space

It is an experience that only a tiny handful of people have ever had – stepping out of the safety and comfort of a spacecraft into the great unknown. Whether walking on the Moon or floating outside the International Space Station, such missions are a remarkable triumph of engineering.

More people could soon share a similar experience if French start-up Stratoflight and global engineering firm Expleo succeed in a new venture. Aiming to deliver a “new sustainable mode of transport,” the partners will offer customers balloon flights up to 35,000m. Once they reach maximum altitude, the passengers will be able to leave the cockpit and walk out on to the craft’s ‘balcony’, looking down to see the curvature of the Earth and a view that stretches for more than 1,200km – allowing them to see Amsterdam and Barcelona simultaneously, for example. 

Zero-pressure balloon

Designed to ensure a safe and immersive experience, the 8m-long craft will carry up to six people, including two pilots. Remarkably, Expleo engineers aim to use bio-sourced, recycled or recyclable material where possible. 

The capsule will be carried by a ‘zero-pressure’ balloon, open at the bottom and with ducts on the sides to allow the gas – green hydrogen – to escape when needed. The hydrogen will be produced at the launch site using renewable energy, including solar and wind, said the partners. 

Everyone onboard will wear pressure suits during the entire flight. Similar to those used by astronauts, the suits will provide oxygen, recycle carbon dioxide, maintain pressure in the very low-pressure environment of the stratosphere, and protect the wearers from harmful radiation. 

After the passengers have enjoyed the view from the balcony, the pilots will initiate the descent, first by a controlled release of the balloon gas, then by deploying a parafoil at around 8,000m. Controlled by fly-by-wire commands, the parafoil and the capsule’s aerodynamic shape will enable speeds of up to 140km/h as the craft descends. 

‘Making space accessible’

The use of hydrogen might make some potential customers think twice, but the gas is often safely used in weather balloons. The capsule will also have four separate parachutes fitted, said the partners, to provide high levels of redundancy.

“Stratoflight provides passengers with multiple exceptional experiences – the ascent to space that feels like a hot-air balloon flight, stepping out on to the viewing balcony, moving into space like an astronaut, and the landing, similar to free flight in a paraglider – all this in a capsule similar to a spacecraft,” said Arnaud Longobardi, airline pilot and co-founder of Stratoflight. 

“For me, this mission is not only the realisation of my dreams as a pilot, but also a technological innovation respectful of the planet.” 

Reservations for passengers will reportedly open in early 2023, with the first flight scheduled for 2025. Stratoflight also aims to offer several flights each year to scientists and educators. The price of a ticket has not been disclosed, but Expleo head of space Frédérique Rebout claimed that “making space accessible to all” was central to the firm’s beliefs, along with respecting the environment.

“Our teams of space engineers have designed this capsule with this dual objectives in mind, and we intend to go further. We are investigating the possibility of making the capsule out of new green composite materials based on bamboo, which would further reduce its carbon footprint.”

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.