NASA's New Rocket Sports a Supersonic Look

NASA?sgleaming new Ares I-X rocket grew an odd-looking hood Wednesday as it launchedskyward on a suborbital test flight ? a telltale sign of a rocket goingsupersonic.

The hood wasactually a vapor cone, sort of like a man-made cloud, created as the long,slender Ares I-X rocket hit Mach 1 and broke the sound barrier. Photographer ScottAndrews caught the moment 39 seconds after the 327-foot (100-meter) rocket blastedoff from NASA?s Kennedy Space Center in Florida. It can also be seen in NASA?s videoof the Ares I-X launch.

The phenomenonis not well studied, but has been seen on jet aircraft and spacecraft,like NASA?s space shuttles and the massive Saturn V rocket, as they surpass thesound barrier. The vapor cone is also referred to as a shock egg or shockcollar.

Scientists thinkthe phenomenon is caused by something called the Prandtl-Glauert singularityand starts when a layer of water droplets is trapped between two high-pressuresurfaces of air. In humid conditions, condensation can gather in the troughbetween the two crests of sound waves produced by a launching rocket or flyingjet. It does not always coincide with breaking the sound barrier.

Photographerscaught a vapor cone on the 363-foot (110-meter) Saturn V rocket that launchedthe Apollo 11, NASA's first manned moon landing mission in 1969. NASAcameras also capture the phenomenon every now and then during spaceshuttle launches, such as the STS-106 flight of Atlantis in 2000.

NASA?s AresI-X rocket is a trial version of the new Ares I booster slated to launch thecrew-carrying Orion capsules that the agency plans to use once the shuttle fleetretires. The prototype consisted of a four-segment solid rocket booster(recycled from the space shuttle fleet?s inventory) capped with a dummy fifthsegment and mock-ups of a second stage, Orion capsule and abort system.

NASA expectedthe rocket to hit a maximum speed of Mach 4.7 before its firststage separated from a dummy upper section two minutes after launch.

The firststage carried parachutes to slow its return and splashed down in the AtlanticOcean to be recovered by a retrieval ship. The dummy second stage, however, wasdiscarded after separation. It crashed in the ocean furtherdownrange as planned.

The launchtest demonstrated the feasibility of the Ares I rocket design, mission managerssaid. NASA?s plan of using Ares I and Orion craft to replace the shuttle fleetand returnastronauts to the moon by 2020 is currently under review by the WhiteHouse.

• Video - Ares I-X Rocket Soars in Test Launch
• The Strangest Moments in Space Launch History
• Image Gallery - Breaking the Sound Barrier

Clickhere for SPACE.com's full Ares I-X mission coverage.