The X-37B looks like a beaten-up version of the old Space Shuttle. However, with no crew nor the need for the necessities that sustain them, it can weigh almost 100 times less and stay in space far longer.
"Since the X-37B's first launch in 2010, it has shattered records and provided our nation with an unrivaled capability to rapidly test and integrate new space technologies," Boeing’s Jim Chilton said in a statement.
During the mission the Naval Research Laboratory’s Photovoltaic Radiofrequency Antenna Module turned sunlight into electricity for microwave transmission to the ground. This idea, widely discussed in the 1980s, is experiencing a renaissance as the falling cost of solar power and space launches bring it closer to cost competitiveness.
To increase its usefulness on this, the sixth mission, the X-37B carried a service module attached to its rear for the first time. The module needed to separate to allow for safe atmospheric re-entry, but in a likely dig at China’s out-of-control Long March boosters, Air Force Secretary Frank Kendall said; “The deliberate manner in which we conduct on-orbit operations – to include the service module disposal – speaks to the United States' commitment to safe and responsible space practices, particularly as the issue of growing orbital debris threatens to impact global space operations.”
Many of the experiments the X-37B carries have military involvement, such as the FalconSat-8 built in collaboration with the Air Force Research Laboratory, leading to speculation it is actually a spy plane or weapon. If so, it’s deep undercover, with analysts arguing it is too easy to track and too ungainly on re-entry for either purpose.
Public parts of the mission included a long-term study on how time exposed to space radiation affects the viability of seeds, and testing of radiation shielding thermal coating materials for NASA.
After this mission, the X-37B has now spent a total of 3,774 days in space, during which time it has flown more than 2.1 billion kilometers (1.3 billion miles).
“The X-37B continues to push the boundaries of experimentation, enabled by an elite government and industry team behind the scenes,” said the Air Force’s Lt. Col. Joseph Fritschen in a statement. “The ability to conduct on-orbit experiments and bring them home safely for in-depth analysis on the ground has proven valuable for the Department of the Air Force and scientific community. The addition of the service module on OTV-6 allowed us to host more experiments than ever before.”
The plane’s operators may not have made too many friends in central Florida, however. Neighbors of the Kennedy Space Center probably get used to loud noises, but a sonic boom immediately prior to its 5:22 am touchdown isn’t the way most people like to wake up on a Saturday. The Tampa Bay Times reports residents about 50 kilometers (30 miles) west of Kennedy saying their “whole house shook”, and there was a “sulfur-smelling fog” after the plane passed. In keeping with the partial secrecy about the project, residents had no warning.