Ares I-X Positioned For Flight-test
By Frank Morring, Jr. 
KENNEDY SPACE CENTER, Fla. - Most of the pieces of NASA's Ares I-X prototype crew launch vehicle have arrived here, awaiting only the final shuttle mission to service the Hubble Space Telescope before they are stacked for the first flight-test of the post-shuttle era.
Heavy steel cylinders simulating the Ares I crew launch vehicle upper sections are lined up in one of the high bays in the huge Vehicle Assembly Building (VAB) originally erected here for the Saturn V moon rocket. And a special train bearing four standard shuttle redesigned solid rocket motor (RSRM) booster segments reached here March 19.
The booster segments, which have passed the time limits for human-rated flight, will power the Ares I-X vehicle off the pad at Launch Complex 39B in a test of the flight dynamics and controllability of the long, narrow "single-stick" Ares I design.
Once the shuttle Atlantis has safely completed its mission to the Hubble telescope - now scheduled for a May 12 launch - and Endeavour is no longer needed as a potential rescue vehicle, crews will begin setting up the Ares I-X vehicle in High Bay 3 in the VAB. With the traveling crane that lifts shuttle orbiters onto their stacks, workers will begin hauling the cylindrical segments 16 stories up and across the central alcove from High Bay 4 to the port-side solid-rocket booster (SRB) slot on a shuttle mobile launch platform in High Bay 3.
The launch platform will be handed over to the Ares I program after the Hubble mission, which is the pacing event in getting the Ares I-X suborbital test off the ground. Its transfer is but one step in a gradual transition here as the massive infrastructure built to put man on the moon in the 1960s is modified to put him back there again after 2020.
The flight-test itself is intended to gather data on the first two minutes of powered flight for the Ares I. One big question that remains is how stage separation will affect the J-2X upper-stage engine, and the Ares I-X test is designed to help answer it.
The solid-fuel section of the test vehicle will burn for about 126 seconds, pushing the stack to an altitude of about 130,000 feet over the Atlantic east of here. As its fuel burns out, engineers will be particularly interested in the way the stack responds to the thrust oscillation that is common in solid-fuel rockets late in their burns.
Early calculations suggested that the oscillation might set up vibrations in the stack that would endanger the crew in the Orion capsule far above, or at least make it difficult for them to respond to emergencies. The Ares I-X vehicle has been instrumented to collect data on the actual oscillation in a single RSRM flying alone.
The simulated upper stage, Orion and launch abort system will stay together and continue on a ballistic trajectory after first-stage separation to about 150,000 feet, before splashing down in the ocean about 128 nautical miles downrange from the pad.
Ares I-X simulated crew module and launch abort system photo: NASA
