Two NASA astronauts and an Italian flight engineer are sheltering in the space station’s Russian segment as mission control analyzes a possible leak of toxic ammonia coolant aboard the complex.

Managers have pushed back the next flight of United Launch Alliance’s Delta 4-Heavy rocket from a launch pad in California until no sooner than early December, and the first launch of SpaceX’s Falcon Heavy for the U.S. Air Force has likely been delayed to some time early next year, officials said this week.

A Russian Proton rocket lifted off Thursday from the Baikonur Cosmodrome in Kazakhstan with the AsiaSat 9 satellite destined to provide television broadcast, video networking and data delivery services over the Asia-Pacific region. Launch occurred at 1852:16 GMT (2:52:16 p.m. EDT), beginning a series of maneuvers expected to last nine hours before AsiaSat 9 is deployed from the rocket.