On August 25, an explosion tore through the southern Alaskan sky. The blast shook the remote island that houses the Kodiak Launch Complex, where the U.S. Department of Defense was testing an unmanned hypersonic glide vehicle (HGV). The flight of the highly secretive craft lasted a mere four seconds before an "anomaly" in the launch rocket forced controllers to deploy the emergency self-destruct mechanism.

The launch, the latest in a series that began in 2011, was saddled with added pressure: China has reportedly carried out at least two hypersonic tests this year (though both also ended in flames). The two nations are racing to engineer a vehicle capable of traveling faster than 10 times the speed of sound, which presents major obstacles. Such a craft requires materials that can withstand temperatures over 3,500°F and a steering system sensitive enough to maneuver through the thin air of the upper atmosphere.

The details behind the U.S. and China's HGV programs remain confidential, but that real-world tests—however spectacular the crashes—are taking place indicates that the vehicles have crossed into the realm of the possible. Experts anticipate that HGVs could be fully operational as soon as 2019 and reach speeds up to Mach 25, or about 16,000 miles per hour.