The record-breaking sixth mission of the X-37B robotic space plane of the US armed forces has finally come to an end, on November 12 it successfully landed at the NASA Kennedy Space Center in Florida. The winged vehicle spent 908 days in orbit — more than four months longer than any previous X-37B flight, writes Space.com.

Boeing’s space plane also delivered a service module into orbit, the first mission for the US Space Force’s X-37B program.

“With the service module added, this was the most we’ve ever carried to orbit on the X-37B, and we’re proud to have been able to prove out this new and flexible capability for the government and its industry partners,” said Jim Chilton, senior vice president of Boeing Space and Launch, in a statement.

The X-37B resembles NASA’s now-retired space shuttle but is much smaller, measuring just 29 feet (8.8 meters) from nose to tail. The space shuttle was 122 feet (37 m) long and was piloted — another key difference, as the X-37B is autonomous.

The US Space Force is believed to have two X-37Bs, both of which were provided by Boeing. To date, the duo has completed six orbital missions, each of which is known as an OTV (Orbital Test Vehicle):

OTV-1: launch on April 22, 2010 and landing on December 3, 2010 (duration 224 days);
OTV-2: March 5, 2011 – June 16, 2012 (468 days);
OTV-3: December 11, 2012 – October 17, 2014 (674 days);
OTV-4: May 20, 2015 – May 7, 2015 (718 days);
OTV-5: from September 7, 2017 to October 27, 2019 (780 days);
OTV-6: from May 17, 2020 to November 12, 2022 (908 days).

The Space Force and Boeing describe the X-37B as a test platform that allows researchers to see how a payload performs in the space environment and then study it on the ground.

“Since the X-37B’s first launch in 2010, it has shattered records and provided our nation with an unrivaled capability to rapidly test and integrate new space technologies,” Chilton said.

Many of these payloads are classified, as are most of the X-37B’s activities. The space force does not release details of the spacecraft’s orbit or say in advance when each OTV mission will end.

But military officials are disclosing information about some of the equipment the X-37B lifts into orbit. For example, it is known that the photoelectric radio frequency antenna module of the US Naval Research Laboratory was tested as part of the OTV-6 mission.

This device, about the size of a pizza box, is designed to convert solar energy into microwaves, which can then be transmitted to Earth. Its work could help bring space solar energy closer to reality, experiment participants say.

OTV-6 also carried FalconSat-8, a satellite designed by cadets at the U.S. Air Force Academy that carries five experimental payloads of its own. The X-37B deployed FalconSat-8 in October 2021, and the satellite remains in orbit today, Boeing representatives said in a statement.

OTV-6 also conducted several famous NASA experiments. One of them tested how cosmic radiation affects plant seeds, and the other measured how different materials react to the space environment.