The US military's secretive X-37B space plane is soon to launch on its next mission. But unlike the spacecraft’s previous missions, which have been shrouded in mystery, the Department of Defense is being slightly more candid about its upcoming flight and even provided a press release about its planned experiments.
The X-37B is scheduled to launch on its sixth mission from Cape Canaveral Air Force Station in Florida on May 16, according to a recent announcement. Although it's still owned by the US Air Force, the US Space Force – yep, that one – will be responsible for the launch, orbit operations, and landing.
The X-37B is an uncrewed orbital vehicle that looks much like a mini version of NASA's iconic Space Shuttle, measuring at just 8.8 meters (29 feet) in length. This will be its first mission to use a compartment to host experiments. One of the experiments will test the reaction of "significant materials" to the conditions in space, and another will study the effect of ambient space radiation on plant seeds, while a third experiment transforms solar power into radiofrequency microwave energy, then studies transmitting that energy to Earth.
The mission will also deploy the FalconSat-8, a small satellite built and designed by cadets at the US Force Academy that holds five separate experiments.
"This sixth mission is a big step for the X-37B program," Randy Walden, Director and Program Executive Officer for the Department of the Air Force Rapid Capabilities Office, said in a statement. "This will be the first X-37B mission to use a service module to host experiments. The incorporation of a service module on this mission enables us to continue to expand the capabilities of the spacecraft and host more experiments than any of the previous missions."
The X-37B program completed its last mission in October 2019, after orbiting Earth for 780 days. As mentioned, there’s been very little official information published about its previous missions. The US Air Force’s website somewhat vaguely states the “primary objectives of the X-37B are twofold: reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth.”
While the US military appears to be more transparent about X-37B missions in recent years, a lack of detail in the past has fueled a fair amount of conjecture about the space plane’s true intentions. One popular theory says it's testing out thrusters in a relatively low orbit with a view to placing reconnaissance satellites here in the near future.
Others have suggested that it's currently being used for some form of military or intelligence application. According to a report in Spaceflight magazine published in 2012, X-37B's orbit closely followed that of China's former space lab, Tiangong-1, leading to speculation that it was being used for space-to-space surveillance against foreign states.
Put together, X-37B missions have racked up a combined 2,865 days in orbit, over 7 years of technology testing. Perhaps, with the Space Force's new candid approach, we can look forward to finding out more about what it's been doing up there all this time.