NASA eyes stadium-sized orb launch: Part 3

NASA is hoping to finally get off the ground with the Super Pressure Balloon mission which has been grounded twice by unfavourable winds at altitude since 1 April.

The word from Wanaka Airport, New Zealand, is that there's a launch window between 9 and 11AM local time tomorrow (5 to 7PM EDT or 9 to 11PM GMT tonight).

The mighty helium-filled orb doing the lofting is hewn from "22 acres of polyethylene film – similar to a sandwich bag", and when fully engorged is a breathtaking 516,499 cubic metres. It's tasked with lifting the University of California's Compton Spectrometer and Imager (COSI), intended to "probe the mysterious origins of galactic positrons, study the creation of new elements in the galaxy, and perform pioneering studies of gamma-ray bursts and black holes."

Mighty: An engorged SPB. Pic: NASA / Bill Rodman

A Super Pressure Balloon mission hangs around at roughly 33.5km for up to 100 days – on paper at least – although the record for a flight is 54 days, on a jaunt that began at the previous Antarctica launch site back in 2009.

In case you're wondering why bother, NASA says that the long-duration high-altitude balloon approach is a cheap alternative to sending payloads spacewards atop rockets.

You can follow tonight's launch action live here, and once the gargantuan sandwich bag has actually been waved off, enjoy the live tracking map as NASA menaces the stratosphere. ®