Nasa's super pressure balloon will not be launched from Wanaka after a sixth attempt has been unsuccessful.

At 11.45am, an airport spokesperson said: 'Devastating news. Due to a technical problem with the balloon winch - the launch attempt is over."

The balloon had been taken out of its box - a sign it would finally be launched after a series of delays.

The weather was still and crisp, with some lingering river fog surrounding the airport this morning.

Roadblocks had been put in place, restricting access along the Luggate highway (State Highway 6), State Highway 8A, and Mt Barker Rd.

A fifth launch attempt scheduled yesterday was canceled because of unacceptable wind conditions.

Nasa's balloon programme office chief Debbie Fairbrother said the reason behind the cancellation was that both surface and upper-level winds were above 10 knots.

"A high-pressure system that would have brought the exact wind conditions we needed did not arrive in time for Thursday's launch attempt," she said.

Upcoming campaigns in Sweden and the United States have meant today's scheduled launch is the sixth and final attempt in Wanaka.

Nasa first began launching super pressure balloons from Wanaka in 2015. Today would be the fourth launch.

The programme was temporarily halted due to funding and Covid-19 issues.

The primary goal of the flight was to validate and certify the balloon technology and, in particular, the balloon's capability to pressurise at high altitudes and cope with heating and cooling during the day-night cycle, Fairbrother said.