This engineer's concept drawing of the A-3 Test Stand shows the 300-foot-tall structure's open steel frame and large exhaust diffuser.

Stennis Space Center firefighter Rodney Boone rappels a tower structure during an onsite training exercise May 11, 2012. The training focused on high-angle rope rescues, which could be needed on the new 300-foot-tall A-3 Test Stand at Stennis.

Stennis Space Center firefighter Rodney Boone rappels a tower structure during an onsite training exercise May 11, 2012. The training focused on high-angle rope rescues, which could be needed on the new 300-foot-tall A-3 Test Stand at Stennis.

Stennis Space Center employees marked another construction milestone July 25 with installation of the 85,000-gallon liquid hydrogen tank atop the A-3 Test Stand. The 300-foot-tall stand is being built to test next-generation rocket engines that could carry humans into deep space once more. The liquid hydrogen tank and a 35,000-gallon liquid oxygen tank installed atop the steel structure earlier in June will provide fuel propellants for testing the engines.

Instructor Rob Mortin watches as Stennis Space Center firefighters Lt. Greg Lampley, Rodney Boone, Vance Forrest and Billy Scarborough practice high-angle rope rescue techniques during a May 11, 2012, training exercise. The exercise specifically focused on scenarios applicable to the 300-foot-tall, open-steel-structure A-3 Test Stand under construction at the rocket engine test facility.

Instructor Rob Mortin watches as Stennis Space Center firefighters Lt. Greg Lampley, Rodney Boone, Vance Forrest and Billy Scarborough practice high-angle rope rescue techniques during a May 11, 2012, training exercise. The exercise specifically focused on scenarios applicable to the 300-foot-tall, open-steel-structure A-3 Test Stand under construction at the rocket engine test facility.

Tree clearing for the site of the new A-3 Test Stand at Stennis Space center began June 13. NASA's first new large rocket engine test stand to be built since the site's inception, A-3 construction begins a historic era for America's largest rocket engine test complex. The 300-foot-tall structure is scheduled for completion in August 2010. A-3 will perform altitude tests on the Constellation's J-2X engine that will power the upper stage of the Ares I crew launch vehicle and earth departure stage of the Ares V cargo launch vehicle. The Constellation Program, NASA's plan for carrying out the nation's Vision for Space Exploration, will return humans to the moon and eventually carry them to Mars and beyond.

KENNEDY SPACE CENTER, FLA. -- On the morning of the second launch attempt, Space Shuttle Discovery is revealed after rollback of the rotating service structure. Seen above the golden external tank is the vent hood (known as the "beanie cap") at the end of the gaseous oxygen vent arm, extending from the fixed service structure. Vapors are created as the liquid oxygen in the external tank boil off. The hood vents the gaseous oxygen vapors away from the space shuttle vehicle. Below it, also extending toward Discovery from the FSS, is the orbiter access arm with the White Room at the end. The crew gains access into the orbiter through the White Room. Atop the FSS is the 80-foot-tall lightning mast. To the right of the shuttle is the water tower, containing 300 gallons of water used for sound suppression at liftoff. The first launch attempt of STS-116 Dec. 7 was postponed due a low cloud ceiling over Kennedy Space Center. The next launch attempt was scheduled for Saturday, Dec. 9, at 8:47 p.m. This will be Discovery's 33rd mission and the first night launch since 2002. The 20th shuttle mission to the International Space Station, STS-116 carries another truss segment, P5. It will serve as a spacer, mated to the P4 truss that was attached in September. After installing the P5, the crew will reconfigure and redistribute the power generated by two pairs of U.S. solar arrays. Landing is expected Dec. 19 at KSC. Photo credit: NASA/Ken Thornsley