The U.S. Department of Defense’s reusable X-37B Orbital Test Vehicle (OTV) is about to make its eighth overall flight into orbit. Vehicle 1, the first X-37B to fly, is scheduled to launch atop a SpaceX Falcon 9 from the Kennedy Space Center’s Launch Complex 39A on Thursday, Aug. 21, at 11:50 PM EDT (03:50 UTC on Friday, Aug. 22).
The launch window is just under four hours long and lasts until 3:40 AM EDT (07:40 UTC) on Friday morning. After liftoff, Falcon 9 will follow a northeast trajectory to loft the X-37B into a low-Earth orbit, possibly a circular orbit at 500 km altitude inclined 49.5 degrees to the equator. The Orbital Test Vehicle 8 (OTV-8) mission will spend an unspecified amount of time in orbit, with missions lasting hundreds of days in orbit before landing on a runway.
The booster supporting this mission, B1092-6, will perform a return-to-launch-site (RTLS) landing and touchdown on the concrete pad at Landing Zone 2 (LZ-2). LZ-2 will be used for all future RTLS missions until landing pads are constructed at Launch Complex 39A (LC-39A) and Space Launch Complex-40 (SLC-40) at the Cape Canaveral Space Force Station (CCSFS). Landing Zone 1 (LZ-1) saw its final landing during the Crew-11 mission.
Landing pad construction at LC-39A and SLC-40 is awaiting environmental reviews to be complete, and the long-term plan is for every launch provider with a reusable vehicle and RTLS capability to use landing pads at the launch complex from which the rocket flies.
Falcon 9 B1092 launching the GPS III SV08 mission from SLC-40. (Credit: Sawyer Rosenstein for NSF/L2)
This flight will not serve as B1092’s first national security mission. The booster also launched the NROL-69 mission on March 24; NROL-69 is thought to have launched a Naval Ocean Surveillance System satellite. The booster also flew the GPS III SV08 payload, the CRS-32 cargo mission to the International Space Station, and two Starlink missions.
OTV-8, as a military mission, likely has many classified objectives. However, some mission experiments have been publicized. One of these is a demonstration of high-bandwidth inter-satellite laser communications, and another is enhanced non-GPS navigation utilizing the highest performing quantum inertial sensor in space.
Laser communications can carry higher data bandwidth due to the shorter wavelength of infrared light versus radio waves. Lasers are also more resistant to jamming due to their targeted nature. OTV-8 will demonstrate laser communications using proliferated low-Earth orbit (LEO) communications satellite networks, and if successful, could allow for more resilient space-based military communications.
The quantum inertial sensor experiment is also an effort to increase resiliency in military space systems. GPS jamming is already known to occur in war-torn areas and could become a serious issue during future conflicts. The inertial sensor detects the rotation and acceleration of atoms, eliminating the need for GPS for navigational information. This technology could also be useful in cislunar space.
Prior to OTV-8, the X-37B fleet of two spacecraft has collectively accrued 4,208 days in space across seven flights. This averages to just over 601 days per mission, which allows for long-term testing in the space environment of technologies earmarked for use in future classified national security satellites or for other national security purposes.
X-37B Vehicle 1 after landing on Runway 33 at the Shuttle Landing Facility on Nov. 12, 2022. (Credit: USAF/SSgt. Adam Shanks)
Some examples of technologies known to have been tested on OTV missions include space domain awareness capabilities, solar power beaming from space, and electric Hall-effect thrusters for the Advanced Extremely High Frequency (AEHF) military communications satellite.
At least one small satellite, FalconSat-8, was launched by the spacecraft on a prior mission. FalconSat-8 was developed by the Air Force Research Laboratory and cadets at the Air Force Academy and contains several experimental technologies. A NASA experiment to study the effects of the space environment on seeds was also flown aboard the X-37B.
The X-37B has launched atop multiple rockets from different providers. The spaceplane’s first four flights, starting in 2010, were launched atop an Atlas V 501, configured with a five-meter fairing and no solid rocket boosters. The spaceplane is enclosed in a payload fairing during ascent.
OTV-5 flew aboard a Falcon 9 Block 4 in 2017, and OTV-6 reverted to the Atlas V 501. OTV-7 launched to space aboard a Falcon Heavy on Dec. 28, 2023, into a highly elliptical orbit.
Earth seen from the X-37B Vehicle 2 during the OTV-7 mission. (Credit: U.S. Space Force)
The spacecraft has also flown in a variety of orbits, including orbits that took the vehicle to very high altitudes far beyond any Space Shuttle flight. In one of these orbits, on the OTV-7 mission, the X-37B successfully demonstrated a new aerobraking method. Though the X-37B and the Shuttle share some similarities, they are very different spacecraft.
The X-37B’s origins date back to the middle of the 1990s, when NASA looked at cheaper alternatives to the Space Shuttle. The U.S. Air Force also looked into a more responsive spaceflight solution, and Boeing built the X-40A prototype as part of the Space Maneuver Vehicle program. The X-40A was a subscale prototype of the X-37 design and flown underneath — and also released from — a CH-47 Chinook helicopter.
The Air Force transferred the X-40A prototype to NASA, and the space agency flew the prototype seven times on free flights before it discontinued its effort in 2004. The uncrewed reusable spacecraft the agency was working on did not contribute directly to its new exploration goals, so the effort was taken over by the Defense Advanced Research Projects Agency (DARPA).
The X-37B spaceplane landing at Vandenberg Space Force Base. (Credit: Boeing)
DARPA built an X-37 prototype and flew it eight times underneath the White Knight aircraft, with three of these being free flights ending in a runway landing. The Air Force’s Rapid Capabilities Office gave Boeing the contract to develop the spaceflight-capable X-37B OTV.
The X-37B, massing around 4,990 kg, is nearly nine meters long and features a 4.5 m wingspan. The spacecraft is also approximately three meters high at its tallest point, and features a payload bay around the size of a pickup truck bed. Two payload bay doors open to expose the spacecraft’s solar panels and payloads to space.
The X-37B uses a hypergolic-fueled engine for deorbit and in-space maneuvering and thrusters to control its orientation. After the spacecraft lands, workers are required to use protective suits to offload the propellant due to its highly toxic nature.
The X-37B Vehicle 1 being prepared for the OTV-8 flight. (Credit: U.S. Space Force)
The spaceplane’s capacity to fly experiments was increased when a non-reusable service module for use in space was added to the design beginning with the 908-day OTV-6 mission in May 2020. OTV-7 also flew with a service module; it is not currently known if OTV-8 is using a service module.
The X-37B became the first U.S. spaceplane to demonstrate an autonomous capability to land on a runway with OTV-1’s landing at what was then Vandenberg Air Force Base on Dec. 3, 2010. Three other OTV flights also used Vandenberg’s Runway 12, while three flights used Runway 33 at the Shuttle Landing Facility in Florida.
OTV-8 is the latest flight of a spacecraft that has proven itself to be a valuable test bed for future space technologies. The X-37B is one of the latest examples of a long-held practice to use experimental testbeds to prove out new technologies.
(Lead image: Falcon 9 atop LC-39A ahead of the USSF-36 mission. Credit: SpaceX)
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