Title: Strat-X
text: Experiments in space can be expensive and infrequent, but Earth’s upper atmosphere is accessible via large scientific balloons, and can be used to address many of the same fundamental questions. Scientific balloons are made of a thin polyethylene film inflated with helium, and can carry atmospheric sampling instruments on a gondola suspended underneath the balloon that eventually is returned to the surface on a parachute. For stratospheric flights between 30 and 40 km above sea level, balloons typically reach the float altitude 2-3 hours after launch, and travel in the direction of the prevailing winds.