When winds meet mountain ranges they are diverted upwards to follow the slopes. But before descending again winds can continue on an upward path, shooting towards space.
Under the right conditions, the winds can bounce along in an undulating up-and-down pattern for hundreds of miles, a pattern known as lee or mountain waves.
These mountain waves sometimes become visible when they give rise to clouds, known as altocumulus standing lenticular clouds, which appear to remain stationary over mountain peaks.
Little is known about what happens at high altitudes where such winds may interact with the polar vortex. However, in a research project, a new type of manned glider is to surf mountain waves and explore their greatest altitudes as well as collect data about the Earth’s atmosphere and its ozone layer.
The glider, known as Perlan II, developed in the US by aviators and scientists with the Airbus Group, goes to Patagonia this May to start flight testing over the Andes.
A tow plane will release the aircraft at 5,000ft, where it should catch a mountain wave. The aim is to reach 90,000ft (27,430 metres), which would be a record for a glider.
At this stratospheric altitude, where the air is just 3% as dense as at ground level, the glider will surf at 400 miles an hour with no external power. The aircraft, which has a crew of two, has no engine, partly to save weight, partly so that atmospheric samples can be collected without a contamination risk.
Perlan’s special safety equipment includes a recovery parachute for the entire sailplane to descend to the ground in the event of a wipeout.
- This article was amended on 24 May 2017. The Perlan project will explore the southern polar vortex, not the northern as stated in the caption.