The US military has lost contact with an experimental hypersonic glider after it was launched by a rocket on a test flight over the Pacific Ocean.
The Falcon Hypersonic Technology Vehicle-2 was launched last Thursday from Vandenberg Air Force Base, California, and was supposed to separate from the booster at an altitude of several hundred thousand feet and then autonomously glide at 13,000mph to a splashdown in a sea range near Kwajalein Atoll, 2,500 miles south west of Hawaii.
The separation did occur, according to a Defence Advanced Research Projects Agency statement.
A preliminary review indicates the vehicle achieved controlled flight in the atmosphere before telemetry was lost, DARPA spokeswoman Johanna Spangenberg Jones said.
The loss of signal came nine minutes after lift-off.
Flight telemetry from the air force, navy, army and US Missile Defence Agency was being analysed to determine details of what happened, including where it came down.
The flight was intended to test technologies for flight at extremely high speeds.
The Lockheed Martin-designed HTV-2 was not intended to be recovered. The test would have ended with it reaching its target in 30 minutes, crashing into the sea and sinking.
Last week's mission was the first of two planned in the HTV-2 programme, which uses Minotaur 4 boosters developed by Orbital Sciences from decommissioned Peacekeeper intercontinental ballistic missiles.
The US military is trying to develop technology to respond to threats around the globe at speeds of Mach 20 or greater, according to DARPA.