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Boeing X-37B OTV

Boeing · Reusable Spaceplane · USA · Digital Age (2010–present)

The Boeing X-37 (designated X-37B Orbital Test Vehicle for the flying examples) is an American reusable robotic spaceplane built by Boeing Phantom Works as a classified US Space Force orbital test bed. After the Space Shuttle, it is the most-flown reusable orbiter in service. Boeing developed the airframe between 1999 and 2010 under a programme that began at NASA, passed to DARPA, then to the USAF, and finally to Space Force. The first orbital flight, OTV-1, launched on 22 April 2010. Two X-37B vehicles are in service; together they have flown 7 missions through 2026, accumulating more than 4,000 days in orbit.

The X-37B is a small unmanned lifting body 8.9 m long with a 4.5 m wingspan, weighing 4,990 kg with around 270 kg of payload. Launch is on an Atlas V 501 or Falcon 9 expendable booster; reentry ends with an autonomous runway landing at Vandenberg Space Force Base or the Kennedy Space Center Shuttle Landing Facility. The vehicle is essentially a scaled-down Shuttle orbiter, with a payload bay of roughly 2.1 × 1.2 m, GH₂ and LOX propellant, a single AR-2/3 hypergolic main engine, RCS thrusters, and autonomous flight-control software. Solar arrays deployed from the payload bay provide about 3 kW of electrical power. On-orbit propellant supports altitude changes from roughly 200 km to 800 km and orbital-plane manoeuvres.

Payloads and objectives remain almost entirely undisclosed. Open-source analysis of flight tracks points to four likely mission lines: experimental sensor testing in orbit (electro-optical, infrared, and SIGINT payloads exercised in space conditions before being committed to fielded satellites); anti-satellite and counter-space technology evaluation, given a manoeuvring envelope and observed track changes consistent with ASAT-related work; novel materials and propulsion experiments; and possible nuclear-thermal-propulsion validation. Mission durations have stretched from 224 days on OTV-1 to 908 days on OTV-6 in 2020-2022. The X-37B is the most heavily classified US spacecraft programme flying today, and Space Force has signalled further vehicles and missions through around 2035.

For Kids — a shorter, friendlier version

The Boeing X-37 is a small robot spaceplane that looks like a tiny Space Shuttle. It has no pilot inside. The plane is launched on a big rocket, spends a long time in space, and then glides back down to a runway by itself.

The X-37 first flew into space in 2010. Two X-37 spaceplanes are still in service today. Together they have flown seven missions and spent more than 4,000 days in orbit. That is over 11 years of total spaceflight.

The X-37 is about as long as a small school bus. It is only about one quarter the size of the Space Shuttle. The plane has a small payload bay in the middle for carrying secret science experiments. Solar panels open up in space to give it power.

The X-37 belongs to the US Space Force. It lands all by itself at Kennedy Space Center or Vandenberg Space Force Base in California. The Space Force does not tell people what the X-37 does on its long missions, so much of its work is kept secret.

Fun Facts

The X-37 is a robot spaceplane that lands by itself on a runway.
Two X-37 spaceplanes have flown more than 4,000 days in orbit together.
It is only about one quarter the size of the Space Shuttle.
The X-37 belongs to the US Space Force.
The plane launches on top of a big Atlas V or Falcon 9 rocket.
Most of what the X-37 does in orbit is kept secret.

Kids’ Questions

How does the X-37 stay in space for so long?

The X-37 has solar panels that fold out from its payload bay once it reaches orbit. The panels make electricity from sunlight. The plane can store this power and use it for years before coming home.

What does the X-37 do in space?

Most of the X-37 missions are kept secret by the US Space Force. People know the plane carries science experiments and tests new technology. Some scientists think it also tests sensors that watch other satellites.

Variants

X-37A ALTV (cancelled): NASA atmospheric drop-test prototype. Few flights.
X-37B OTV (2010-present): Orbital Test Vehicle. 2 vehicles built.

Notable Operators

US Space Force (2019-present): Current operator. Transferred from USAF in 2019.
US Air Force (2010-2019): Original operator. Six missions before transfer.

Frequently Asked Questions

What is the X-37B for?

The US government has never officially explained X-37B objectives. Outside analysts — including the Secure World Foundation, the Center for Strategic and International Studies, and commercial satellite-tracking firms — infer the mission from observed flight tracks and commercial-imagery shots of the vehicle in orbit. The leading hypotheses are three. First, experimental sensor and electronics testing in space before committing the technology to large reconnaissance satellites: flying a sensor on a returnable X-37B is far cheaper than building it into a $500 million spacecraft. Second, co-orbital and counter-space experimentation, including close approaches to other satellites — the X-37B is reported to have made close-approach manoeuvres to a Chinese satellite in 2020 and a Russian satellite in 2022. Third, classified payload deployment and retrieval. The X-37B is widely treated as an experimental and intelligence-related platform rather than a deployed weapon.

Sources

Wikipedia — Boeing X-37