Boeing X-37
The Boeing X-37 is a reusable robotic spaceplane developed for various orbital missions, operated by the US Air Force. Initially conceived as part of a NASA program in the late 1990s, the project transitioned to the Department of Defense in 2004. The X-37, also known as the Orbital Test Vehicle (OTV), is designed to demonstrate reusable spacecraft technologies and conduct experiments in low-Earth orbit. Since its first mission in 2010, the X-37 has completed multiple classified missions, carrying secret payloads and remaining in orbit for extended periods, often exceeding 700 days.
Each mission is launched using rockets from providers like United Launch Alliance and SpaceX. The vehicles have landed at various locations, including Vandenberg Air Force Base and the Kennedy Space Center. Due to the classified nature of many of its activities, there is speculation about its potential military applications, although these claims are largely dismissed by experts. The X-37 program represents a significant step in advancing unmanned space technology and its implications for future space operations.
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Boeing X-37
The Boeing X-37 is a reusable robotic spacecraft that is transported to space via a launch vehicle and subsequently re-enters the atmosphere and lands as a spaceplane. Also known as the Orbital Test Vehicle (OTV), the X-37 is operated by the US Air Force and used for various orbital spaceflight missions meant to demonstrate the capabilities of reusable space technologies. Beginning as a National Aeronautics and Space Administration (NASA) program in 1999 and constructed in the early 2000s, the X-37 was transferred to the US Department of Defense in 2004 and underwent its first test flight two years later. Since completing its first formal mission in 2010, the X-37 has completed a number of additional classified missions in service of the military space program. On each of these missions, the X-37 carried top-secret payloads on long-duration flights in Earth's orbit, typically remaining in orbit for hundreds of days at a time.
Background
The idea for the X-37 first arose when NASA began looking into less-costly alternatives to the Space Shuttle in the 1990s. Since it was equipped with reusable booster engines and could be flown on multiple missions, the Space Shuttle was expected to dramatically lower the costs involved in transporting astronauts and equipment to low-Earth orbit when it was first developed. Over time, however, the Space Shuttle ended up requiring far more maintenance than imagined and ultimately failed to lower costs. NASA was left with little choice but to explore other means of reaching low-Earth orbit.
One potential solution to NASA’s problem was to move away from using human crews and instead focus on unmanned vehicles that did not require habitable living spaces or life-support systems. Since unmanned spaceplanes can be much smaller than manned spaceplanes, they typically require less thrust and a smaller rocket to reach their destination. Unmanned spaceplanes also have the advantage of being able to remain in low-Earth orbit for much longer periods than would be possible with human crewmembers aboard. With this in mind, NASA began work on developing an unmanned spaceplane in the mid-1990s. Around the same time, the U.S. Air Force was working on a similar craft known as the Space Maneuver Vehicle that was eventually built by Boeing. That craft, the X-40A test aircraft, was an 85-percent-scale version of NASA’s proposed spaceplane that flew one mission for the Air Force before being loaned to the space agency. After conducting a series of additional test flights with the X-40A, NASA moved forward with its plan for a full-scale spaceplane.
Officials at NASA originally intended to build two separate vehicles, including the Approach and Landing Test Vehicles (ALTV) and an Orbital Vehicle. Before that could happen, however, these officials decided that an unmanned spaceplane would not support the agency’s goals for space exploration and therefore handed the project off to the Pentagon’s Defense Advanced Research Projects Agency (DARPA). With the help of Boeing’s Phantom Works division, DARPA built the ALTV, which was the original test version of the X-37. Boeing also later constructed the final full-scale version of the X-37, often referred to as the X-37B.
Overview
The X-37 is an experimental spaceplane that is primarily designed to demonstrate reusable spacecraft technologies that could prove pivotal to the United States’ future in space. It is also used to carry out various experiments in low-Earth orbit that can later be examined by scientists on the ground. The X-37 program is operated by the Air Force’s Rapid Capabilities Office, and mission control for X-37 flights is based out of the 3rd Space Experimentation Squadron at Schriever Air Force Base in Colorado. Because much of the X-37’s onboard gear and many of the details relating to its orbital activities are classified, little is publicly known about the specifics of its missions. While this had led to some speculation that the X-37 is actually an experimental space weapon that might be used to damage or capture other countries’ satellites, the Air Force denies these allegations and most experts agree that such claims are unlikely to be true, especially considering that the craft is too small and probably not maneuverable enough to pull off such actions.
Two separate X-37 vehicles flew a total of six missions by the end of 2023. These missions were officially referred to as OTV-1, OTV-2, OTV-3, OTV-4, OTV-5, OTV-6, and OTV-7. Each of the first four flights and the sixth flight were launched with the aid of an Atlas V rocket manufactured by United Launch Alliance. The fifth was lifted into low-Earth orbit by a SpaceX Falcon 9 rocket, and the seventh launched aboard a Falcon Heavy rocket.
OTV-1 launched in April 2010 and remained in orbit for a total of 224 days. OTV-2, which utilized the second X-37 spaceplane, subsequently launched in March 2011, remained in orbit for 224 days, and returned in June 2012. The first X-37 vehicle was again used for OTV-3, which launched in December 2012. It stayed in orbit for 647 days until returning to Earth in October 2014. At the conclusion of each of the first three OTV missions, the X-37 landed at Vandenberg Air Force Base in California. The second X-37 was used again for OTV-4. After launching in May 2015, OTV-4 remained in orbit for a record-breaking 718 days before returning in May 2017. At the end of the OTV-4, the X-37 landed at NASA’s Shuttle Landing Facility at the Kennedy Space Center (KSC) in Cape Canaveral, Florida, for the first time.
The fifth OTV mission (OTV-5) launched from KSC in September 2017 and remained in orbit for 780 days. Notably, OTV-5 carried the Air Force Research Laboratory Advanced Structurally Embedded Thermal Spreader, which was an experiment designed to test experimental electronics and oscillating heat-pipe technologies in a long-duration space environment. OTV-5 also carried a number of other experiments and small satellites. Upon completing its mission, OTV-5 returned to Earth and touched down at the NASA Shuttle Landing Facility on October 27, 2019. The sixth OTV mission (OTV-6) launched from KSC in May 2020 and broke its predecessor's duration record by remaining in orbit for 908 days. It was the first mission to introduce a service module-a ring attached to the rear of the vehicle. This increased the number of experiments that could be performed during the mission. It returned to Earth on November 12, 2022. The seventh OTV mission launched from KSC in December 2023. OTV-7 changed its orbit around Earth in 2024 to dispose of its service vehicle. OTV-7's return to Earth was scheduled for 2027.
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