HOUSTON — Step by step, the overarching elements of a human mission to a near-Earth asteroid are coming together at NASA’s Johnson Space Center (JSC), even though the needed hardware is still in development, timelines are hazy and budgets are uncertain.

Scaled Composites completed the glide-flight envelope

HOUSTON — Astronauts Sunita Williams and Akihiko Hoshide will attempt to troubleshoot problems with an electrical unit outside the International Space Station during a Sept. 5 spacewalk organized over the U.S. Labor Day weekend.

MOTOR RUNNING: Alliant Techsystems (ATK) will perform a horizontal test-firing of their GEM-60 solid rocket motor on Sept. 6 at 11:15 a.m. MDT at the company’s facility in Promontory, Utah. The 43-ft.-long, 60-in.-dia. graphite epoxy motor will be cooled to 30F and will produce up to 270,000 lb. of thrust. The GEM-60’s fixed nozzle is needed to accurately test at the colder temperature. The nozzle, previously built by a supplier, is now built by ATK. A public viewing area will be available along route 83 North, approximately 20 mi. west of Corinne, Utah.

NASA prepared a response to a failed attempt on Aug. 30 to replace a degraded Main Bus Switching Unit

HOUSTON — NASA’s twin Radiation Belt Storm Probe mission spacecraft thundered into Earth orbit atop an Atlas 5/Centaur upper stage combination early Aug. 30, initiating a $686 million, two-year mission for studies of high-energy particle fluctuations within the Earth’s Van Allen radiation belts, including their response to solar activity and influences on space weather. The United Launch Alliance rocket carrying the two 1,400-lb. probes lifted off from Space Launch Complex-41 at Cape Canaveral Air Force Station, Fla., at 4:05 a.m. EDT.

SOFIA FLIES: NASA’s Stratospheric Observatory for Infrared Astronomy (Sofia) is to begin its 2012-2013 mission series in November from Dryden Aircraft Operations Facility in Palmdale, Calif. Called Cycle 1, the science series will include 46 flights grouped in four multi-week observing campaigns. Sofia is a 747SP modified to carry a 100-in.-dia. infrared telescope.

U.S. and Japanese astronauts struggled unsuccessfully to replace a failing Main Bus Switching Unit