The Air Force's latest attempt to field a hypersonic weapon that can hit any target around the world in an hour ended in failure when Air Force engineers lost contact with the weapon during a test flight on Tuesday.
The prototype weapon, dubbed the X-51 Waverider, was designed to travel at Mach 6 speeds, or six times the speed of sound.
Without the fin, the weapon was unable to activate its so-called "scramjet," which would have propelled it into subsonic speeds. The weapon eventually crash-landed into the Pacific Ocean, off the coast of California.
This was the second failure for the Waverider program in as many years, and the third failed attempt by Air Force engineers to successfully test a hypersonic weapon.
In 2011, an engine failure caused a previous Waverider prototype to also crash into the ocean after program officials were unable to remotely restart the weapon's engine during the flight.
Last August, a similar weapon developed by the Defense Advanced Research Projects Agency (DARPA), known as the Falcon Hypersonic Test Vehicle 2, lost contact with DOD handlers during its test flight.
The weapon was mounted on top of an Air Force Minotaur IV rocket and launched from Vandenberg Air Force Base, Calif.
The rocket and its payload traveled successfully into the earth's upper atmosphere, where the Falcon separated from the Minotaur, DARPA said at the time.
Once separated, the Falcon should have glided through the atmosphere at nearly 13,000 miles per hour, while separate air, land and sea-based assets collected flight and performance data from the vehicle's on-board systems.
But shortly after the Falcon began the glide phase of the test flight, DARPA officials say they lost contact with the vehicle.
The Pentagon has long sought a conventional missile, known as a prompt global-strike weapon, that can move at the same speeds as a nuclear missile.
Former Vice Chief of the Joint Chiefs of Staff Gen. James Cartwright, among others inside DOD, have championed the technology.
Advocates argue it would provide the United States more flexibility in responding to global crises, allowing the United States to rely on weapons that could be delivered to a remote area quickly without relying on nuclear weapons.
Some prompt global-strike proponents claim such a weapon could have been used against high-value targets such as the late Osama bin Laden.
However, that argument appears to fallen out of favor within DOD, largely because of the difficulties of getting excellent actionable intelligence with such a short time frame.