speculated it became the first manmade object to enter Earth's orbit. The cap was never found.

In a conversation with Bill Ogle, Brownlee estimated its velocity as "six times the escape velocity from the Earth"--approximately 67.2 km/s (150,000 mph). Scientists believe compression heating caused the cap to vaporize as it sped through the atmosphere. A high-speed camera, which took one frame per millisecond,