Here's everything we know for sure about the United State' X-37B experimental spaceplane

• The X-37B is the United States first spaceplane since the Space Shuttle.
• It has been in development since the late 1990s,
• But, what exactly is its purpose?

The X-37B is the latest variant of a program of spaceplanes allegedly intended to perform similar functions to the venerable and now cancelled Space Shuttle program that preceded it. Autonomous, small, and very fast, what exactly is this new spaceplane's purpose?

Let's see what we know about this mysterious craft.

What is the X-37B spaceplane?

The Orbital Test Vehicle (OTV), also known as the Boeing X-37, is a reusable autonomous spaceplane. A launch vehicle launches it into space, then after returning to Earth's atmosphere, it lands in a similar fashion to a conventional aircraft.

The X-37 is currently run by the US Space Force, but up until 2019, it was run by the Air Force Space Command and used for covert missions and orbital spaceflight missions meant to showcase reusable space capabilities. It is a variant of the previous Boeing X-40 that had been scaled down by 120%.

Before being turned over to the Pentagon's Defense Advanced Research Projects Agency (DARPA) in 2004, the X-37 was a NASA project. Development began in 1999 when NASA chose Boeing Integrated Defense Systems to create and construct an orbital vehicle. This was then made by Boeing's Phantom Works in California.

The project cost US$192 million over a four-year period, with NASA spending US$109 million, the US Air Force spending US$16 million, and Boeing spending US$67 million.

At the end of 2002, Boeing received a brand-new US$301 million contract as a component of NASA's Space Launch Initiative framework. 

In comparison to DARPA's Hypersonic Technology Vehicle, the X-37 has a reduced cross range and Mach numbers at higher altitudes, due to its aerodynamic design, which was adapted from the bigger Space Shuttle orbiter.

An early specification for the spacecraft was to provide a total mission delta-v (a measure of a spacecraft's change in velocity) of 7,000 miles per hour (3.1 km/s).

The X-37 was initially intended to be taken into orbit in the cargo bay of the Space Shuttle. On September 13, 2004, the Defense Advanced Research Projects Agency (DARPA) received the X-37 from NASA.

The X-37's ability to rendezvous with satellites and carry out maintenance was an early program objective. The X-37 underwent re-designing for launch on a Delta IV or equivalent rocket after it was discovered that a shuttle trip would not be financially viable. Today, the X-37B rides the United Launch Alliance’s Atlas V booster into space, although it is also capable of being launched by different rockets. During its fifth mission in 2017, a SpaceX Falcon 9 rocket was used.

The project was later labeled as classified. The X-37 was promoted by DARPA as a component of the independent space policy that the US Department of Defense has been pursuing since the Challenger catastrophe in 1986.

X-37B's vital statistics

These statistics are taken from official figures, and other figures quoted, that are readily available to the public.

• Crew: None/Autonomous
• Payload capacity: 500 lbs (227 kg)
• Length: 29 feet 3 inches (8.9 meters)
• Wingspan: 14 feet 11 inches (4.5 meters)
• Height: 9 ft 6 inches (2.9 meters)
• Max launch weight: 11,000 lb (4,990 kg)
• Electrical power: Gallium arsenide solar cells with lithium-ion batteries
• Launch vehicles: United Launch Alliance Atlas V (501) and SpaceX Falcon 9
• Payload bay: 7 feet (2.1 meters) × 4 feet (1.2 meters)
• Orbital speed: 17,426 mph (28,044 kph)
• Orbit: Low Earth orbit

Is the X-37B a weapon?

Despite flying six missions to date, the X-37B's true purpose remains a mystery. Understandably, The Space Force's latest Orbital Test Vehicle drone has drawn some suspicion from home and abroad with regard to its actual purpose. Is it a space-based anti-satellite strike aircraft? Is it used for high-altitude surveillance and the deployment of spy satellites?

Can it track enemy weapons or launch missile attacks? These and other inquiries abound as the Boeing-built space drone advances in technological development.

According to the Pentagon, the X-37B was recently fitted with a new service module that allowed for large numbers of experiments to be carried to orbit. During a 2020 mission, the X-37B deployed a small satellite called FalconSat-8, which contained five experimental payloads designed by NASA and the U.S. Air Force. This was the first time the military had disclosed any specifics about such cargo.

According to an Air Force report, the program is testing advanced guidance, navigation, and control, avionics, thermal protection systems, conformal reusable insulation, lightweight electromechanical flight systems, advanced propulsion systems, advanced materials, and autonomous orbital flight, reentry, and landing technologies.

“Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends, and lands horizontally on a runway,” an Air Force Statement says. 

The Air Force's stated technologies raise numerous intriguing and important issues, many of which have to do with the capability of carrying out activities at extremely high speeds and, therefore, high temperatures. In 2019, former Air Force Secretary Heather Wilson told a panel at the Aspen Security Forum that the X-37B may be able to fly low enough to use Earth's atmosphere to alter its orbit, maneuvers which may be designed to prevent enemies from predicting exactly how the craft will move.

The ability to maintain a steady flight trajectory for space-traveling weapons like intercontinental ballistic missiles or hypersonic missiles also makes "thermal protection" crucial for space flight in several fundamental ways.

Furthermore, in order for humans to travel into space, some form of insulating or thermal protection technology is required. Because of this, it is possible that at some unspecified time in the future, human, armed, high-speed spacecraft could launch strikes from beyond the Earth's atmosphere.

These materials are already developing rapidly since they are essential for the operational deployment of hypersonic weapons. They are required to assure the structural configurations required to produce the right air flow boundary layer surrounding missiles, interceptors, or spacecraft, in addition to maintaining flight stability at hypersonic speeds.

Spacecraft autonomy is also very important because, as autonomous space flight algorithms advance quickly, uncrewed systems may be able to carry out surveillance missions, strengthen or expand satellite communications networks, or even fire weapons on their own or under the control of ground-based operators acting in a command and control capacity.

So, for now, the jury is somewhat out. However, The Space Force's stated goal is to "enhance the way U.S. forces fight and to provide decision-makers with additional military options. This means organizing, training, and equipping service members to successfully conduct global space operations." So, it is quite likely that later production models of the spaceplane could have both benign and aggressive applications.

What does X-37B do?

Officially, the X-37B is an experimental reusable autonomous spaceplane. But, as we have seen above, it could, in the future, play a variety of roles for the United States Space Force. This has, understandably, resulted in various outsiders of the program speculating widely as to the craft's capabilities and ultimate purpose.

For example, Tom Burghardt predicted on Space Daily in May 2010 that the X-37B may be utilized as a spy satellite or a weapon delivery vehicle. Subsequently, the Pentagon refuted reports that the test flights of the X-37B aided in the creation of space-based weaponry. 

Allegations that the X-37B was being used to spy on China's Tiangong-1 space station module also surfaced in January 2012.

Later, former U.S. Air Force orbital analyst Brian Weeden disputed this assertion, pointing out that the spacecraft's orbits prevented any useful surveillance flybys. Security specialists reportedly claimed that the X-37B was being used "to test surveillance and spy instruments, notably how they hold up against radiation and other perils of orbit," according to an article in The Guardian from October 2014.

2009 saw the implementation of an EmDrive technology transfer agreement with Boeing through the use of a State Department TAA and a UK export license that had been authorized by the UK Ministry of Defence. However, since then, Boeing has declared that it is no longer researching this field of study.

Other reports speculate that the X-37B is being used by the U.S. Air Force to test a Hall-effect propulsion system for Aerojet Rocketdyne. 

When an X-37B is in an elliptic orbit, it could, at perigee, use the thin atmosphere to make an orbit change, preventing some observers from discovering the new orbit for a while, and in theory allowing secret activities, according to former US Secretary of the Air Force Heather Wilson, who spoke about this in July 2019.

Notification of satellites launched from the X-37B was not given to the United Nations Office for Outer Space Affairs, as required by the Registration Convention, according to astronomer Jonathan McDowell, editor of Jonathan's Space Report, therefore other parties to the convention would not be aware of them.

Interestingly, it has also been speculated that the Chinese may have recently constructed spacecraft which emulates the design and capabilities of the U.S.' X-37B. 

And that, spaceplane lovers, is your lot for today.

The X-37B program is as tantalizing in its nature as it is frustrating to not know its exact purpose. However, it can be argued that it is a positive step in the direction of returning to experimentation with methods of getting humans, satellites, and research into space using reusable spacecraft. Whether or not the spacecraft will be further militarized or not is yet to be seen, but any spin-off technologies used to better human existence on Earth will be a nice bonus.