USA-261, also referred to as Orbital Test Vehicle 4 (OTV-4) or AFSPC-5, is the second flight of the second

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and product ...

X-37B The Boeing X-37, also known as the Orbital Test Vehicle (OTV), is a reusable robotic spacecraft. It is boosted into space by a launch vehicle, then re-enters Earth's atmosphere and lands as a spaceplane. The X-37 is operated by the United State ...

, an American unmanned vertical-takeoff, horizontal-landing

spaceplane A spaceplane is a vehicle that can fly and glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Orbital spaceplanes ten ...

. It was launched to

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

aboard an

Atlas V Atlas V is an expendable launch system and the fifth major version in the Atlas (rocket family), Atlas launch vehicle family. It was originally designed by Lockheed Martin, now being operated by United Launch Alliance (ULA), a joint venture be ...

rocket from

Cape Canaveral , image = cape canaveral.jpg , image_size = 300 , caption = View of Cape Canaveral from space in 1991 , map = Florida#USA , map_width = 300 , type =Cape , map_caption = Location in Florida , location ...

on May 20, 2015. Its mission designation is part of the USA series. The spaceplane was operated by the

Air Force Space Command The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

, which considers the mission classified and as such has not revealed the objectives. However, the Air Force did reveal that the X-37 would be carrying an experimental

hall-effect thruster In spacecraft propulsion, a Hall-effect thruster (HET) is a type of ion thruster in which the propellant is accelerated by an electric field. Hall-effect thrusters (based on the discovery by Edwin Hall) are sometimes referred to as Hall thruster ...

for testing ahead of potential use in future

AEHF Advanced Extremely High Frequency (AEHF) is a constellation of communications satellites operated by the United States Space Force. They are used to relay secure communications for the United States Armed Forces, the British Armed Forces, the C ...

satellites. Additionally,

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

announced it was flying a materials science payload similar to

MISSE The Materials International Space Station Experiment (MISSE) is a series of experiments mounted externally on the International Space Station (ISS) that investigates the effects of long-term exposure of materials to the harsh space environment. T ...

called METIS.

Mission

OTV-4 is the second mission for the second X-37B, and the fourth X-37B mission overall. It flew on an

rocket, with a 5-meter payload fairing and no

solid rocket boosters A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to give ...

. Originally scheduled to launch on May 6, OTV-4 was delayed until May 20 for undisclosed reasons. OTV-4 launched successfully at 11:05 Eastern Time on May 20, 2015. OTV-4 stayed in orbit for a record-setting 718 days, beating OTV-3's record of 674 days. OTV-4 landed on May 7, 2017 at the

Shuttle Landing Facility The Shuttle Landing Facility (SLF) also known as Launch and Landing Facility (LLF) is an airport located on Merritt Island in Brevard County, Florida, United States. It is a part of the Kennedy Space Center and was used by Space Shuttle for lan ...

ELaNa XI

utilized the launch of OTV-4 to fly the eleventh ELaNa

CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...

rideshare mission. Ten cubesats were deployed from a P-POD deployment system affixed to the

Centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...

upper stage. ELaNa XI included

LightSail-1 LightSail is a project to demonstrate controlled solar sailing within low Earth orbit using a CubeSat. The project was developed by The Planetary Society, a global non-profit organization devoted to space exploration. It consists of two spacecr ...

, an experimental

solar sail Solar sails (also known as light sails and photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large mirrors. A number of spaceflight missions to test solar propulsion and navigation have been p ...

References

{{Orbital launches in 2015 Spacecraft launched in 2015 Satellites of the United States Air Force Spacecraft which reentered in 2017 USA satellites Boeing X-37

Mission

ELaNa XI

See also

References