An unpiloted military space plane, launched by an Atlas 5 rocket in May 2015, glided to an unannounced landing on the long shuttle runway at the Kennedy Space Center on Sunday, closing out a 718-day mission. It was the first Florida landing of a returning spacecraft since Atlantis flew home in the program's final mission in 2011.

Sonic booms rumbled across central Florida around 8 a.m. and a few minutes later, the Air Force tweeted that the Boeing-built X-37B space plane -- a compact, delta-wing craft equipped with a payload bay, a solar power boom and a sophisticated computer control systems -- had returned from orbit and landed safely.

The #AirForce #X37B #OTV4 has returned from orbit and has landed safely @NASAKennedy. Stay tuned for more info. — U.S. Air Force (@usairforce) May 7, 2017

"Today marks an incredibly exciting day for the 45th Space Wing as we continue to break barriers," Brig. Gen. Wayne Monteith, 45th Space Wing commander, said in a statement. "Our team has been preparing for this event for several years, and I am extremely proud to see our hard work and dedication culminate in today's safe and successful landing."

It was the fourth clandestine flight of the X-37B, the longest in the program and the first to end in Florida, where Boeing has taken over two former shuttle processing hangars that have been modified to handle the secret spycraft. The first three missions ended with landings at Vandenberg Air Force Base northwest of Los Angeles.

Total time in space by both vehicles across four flights now stands at 2,085 days.

"This mission once again set an on-orbit endurance record and marks the vehicle's first landing in the state of Florida," Lt. Col. Ron Fehlen, X-37B program manager, said in the Air Force statement. "We are incredibly pleased with the performance of the space vehicle and are excited about the data gathered to support the scientific and space communities."

The program's fifth launch is expected later this year.

Two X-37Bs, also known as OTVs, or orbital test vehicles, are known to exist. OTV-1 flew the program's first and third missions while OTV-2, flew the second and fourth, which began with launch atop an Atlas 5 rocket at the Cape Canaveral Air Force Station on May 20, 2015.

A nose-on view of the X-37B, one of two autonomous military spaceplanes used for classified missions in low-Earth orbit. U.S. Air Force

The spacecraft are believed to fly as orbital test beds for advanced technology sensors and other systems but the program is classified, and the Air Force provides almost no details on the nature of the space plane's missions, what might have been accomplished or when the reusable craft might fly again.

But before OTV-2 took off on its just-ended flight, the Air Force acknowledged two experiments: a NASA materials science project and one to test an Aerojet Rocketdyne Hall-effect thruster, which generates low but steady thrust by accelerating electrically charged xenon ions. The thrusters are used aboard Advanced Extremely-High Frequency military communications satellites.

But in general, the X-37 program is conducted in near total secrecy.

Joan Johnson-Freese, a space policy analyst at the Naval War College, said before the most recent launching that the X-37B appears to be what the Air Force claims, a technology demonstrator and testbed. But she said the secrecy surrounding the program likely will continue fueling interest among potential adversaries.

"What's interesting to me is it's being done in such an opaque manner," she said. "If the Chinese were doing this, oh my God, there would be congressional hearings on a daily basis and programs being ginned up to respond to it. It has capabilities that other countries aren't sure about, and so they're going to be very nervous about them. If it's a highly maneuverable space vehicle, that has some pretty significant implications."

SpaceX launch a major test for its re-usable technology

The original idea for a small unmanned orbiter was developed by NASA and built by Boeing's Phantom Works division. But the program was turned over to the Pentagon's Defense Advanced Research Projects Agency, or DARPA, in 2004.

Two years later, the Air Force took over. The first X-37B took off on the program's initial orbital test flight April 22, 2010. The spacecraft spent nearly 225 days in orbit before gliding to a computer-controlled touchdown at Vandenberg Air Force Base, Calif.

A second X-37B, the same one that landed Sunday, was launched on March 5, 2011. It spent 469 days in space, landing June 16, 2012, at Vandenberg. The third flight, the second for the original OTV-1, took off on Dec. 11, 2012 and landed in California on Oct. 17, 2014, after logging nearly 675 days aloft.

The unmanned orbiters are based on the same lifting body design used for the space shuttle and they fly a similar re-entry trajectory.

But the X-37B features more lightweight composite materials, improved wing insulation and tougher heat-shield tiles that "are significantly more durable than the first generation tiles used by the space shuttle," according to a Boeing website description. "All avionics on the X-37B are designed to automate all de-orbit and landing functions."

The X-37B is equipped with a scaled-down 4-foot-by-7-foot payload bay. But unlike the space shuttle, which relied on fuel cells for electrical power, the Air Force spaceplane is equipped with a deployable solar array that permits it to remain in orbit for long-duration missions.

But exactly what the X-37B does in orbit remains a mystery.</s>A sonic boom that rattled Central Florida early Sunday morning was no secret. What caused it was a secret military mission ending at Kennedy Space Center.

The U.S. Air Force tweeted Sunday morning that “The Air Force #X37B #OTV4 has returned from orbit and landed safely at @NASAKennedy.”

The X37B is a secret military unmanned mini-space shuttle, which as been orbiting the Earth for nearly two years on its fourth flight.

There were rumors back in February that the X37B might be returning to Florida. Now, after 719 days flying around our planet, the mini shuttle landed at Kennedy Space Center at its Shuttle Landing Facility.

According to NASASpaceFlight.com, which reported back in February, “Depending on the specific path the X-37B follows in its entry sequence – currently understood to be a descending node entry over portions of the United States and Florida – large swathes of Central Florida could be graced with twin sonic booms during the morning commute as the X-37B rather insistently heralds its arrival back home.”

The site also noted that this would be the first time since the mini shuttle landed at Kennedy Space Center, where America’s space shuttle program used to call its home for decades during their program.

“The ability for this fourth mission to attempt a return to the runway at Kennedy follows three highly successful, completely autonomous deorbit, entry, and landing sequences of the first three X-37B flights, which all ended with precise touchdowns at the runway at Vandenberg Air Force Base, CA,” the site said.

The unannounced return of the shuttle — it was on a secret mission, after all — had many Central Floridians wondering what they just heard or what woke them up.</s>CAPE CANAVERAL, Fla. -- An unmanned military space plane landed at Kennedy Space Center on Sunday morning sending a sonic boom across Central Florida and concluding an almost two-year mission in orbit, according to the Air Force.

The Air Force tweeted shortly after 8 a.m. that the reusable X-37B Orbital Test Vehicle had landed safely, completing its fourth classified mission. OTV-4 launched from Cape Canaveral on a United Launch Alliance Atlas V rocket on May 20, 2015.

Air Force officials have called the X-37B program, which is managed by the Air Force Rapid Capabilities Office, "the newest and most advanced re-entry spacecraft."

The sonic boom could be heard throughout Central Florida. Some Brevard County residents might have heard the booms before the space plane landed at the Shuttle Landing Facility.

Officials said several technologies are being tested in the program.

"The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth," officials said.

Air Force officials said the X-37B is the first vehicle able to return experiments to Earth for further inspection and analysis since NASA's Shuttle Orbiter. The X-37B is able to stay in space longer because if its on-orbit time of 270 days or more, according to officials.</s>Workers in protective suits check out the Air Force’s X-37B Orbital Test Vehcile after its touchdown at NASA’s Kennedy Space Center Shuttle Landing Facility. (U.S. Air Force Photo)

After nearly two years in orbit, the U.S. Air Force’s X-37B robotic space plane landed at NASA’s Kennedy Space Center in Florida today with a loud sonic boom, but nary a word about what exactly it was doing up there all this time.

This was the fourth and longest classified mission for the Boeing-built craft, which was launched from Florida 718 days earlier in 2015 atop a United Launch Alliance Atlas 5 rocket. The three earlier missions were flown in 2010, 2011 and 2012, and landed at Vandenberg Air Force Base in California.

The Air Force’s fleet of X-37B Orbital Test Vehicles has now spent a total of 2,085 days to gauge the reusable winged plane’s ability to conduct on-orbit operations and return for airplane-style horizontal landings.

“The landing of OTV-4 marks another success for the X-37B program and the nation,” Lt. Col. Ron Fehlen, X-37B program manager, said in an Air Force news release. “This mission once again set an on-orbit endurance record and marks the vehicle’s first landing in the state of Florida. We are incredibly pleased with the performance of the space vehicle and are excited about the data gathered to support the scientific and space communities.”

The purpose of the X-37B program has been a mystery for well more than a decade. Precursor prototypes were rumored to be designed as “space bombers,” but more recent speculation has downplayed the plane’s potential use against terrestrial targets.

Instead, the plane is seen as an experimental test bed for military space technologies.

“The primary objectives of the X-37B are twofold: reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth,” the Air Force says in its X-37B fact sheet.

Such experiments are thought to include a new type of rocket thruster built by Aerojet Rocketdyne, new sensors for intelligence gathering, and new tools for deploying and retrieving payloads in space.

Randy Walden, director of the Air Force Rapid Capabilities Office, took special note of the first-ever Florida landing. “The ability to land, refurbish and launch from the same location further enhances the OTV’s ability to rapidly integrate and qualify new space technologies,” he said.

The Air Force says it’s preparing to launch its fifth top-secret X-37B mission from Cape Canaveral Air Force Station in Florida later this year.
• In video call to space station, President Donald Trump calls for speeding up trips to Mars
• Cygnus cargo craft heads for space station with 3-D printer and more cool gizmos</s>Secret U.S. Space Plane Lands With A Boom In Florida

The Air Force's experimental X-37B space plane announced the end of its nearly two-year mission by creating a sonic boom on Sunday that surprised residents along Florida's Space Coast. Officials have provided only vague details about the unmanned craft's more than 700-day mission.

"Not much is known about the 30-foot-long robotic spacecraft or what it took to space," as member station WMFE reports.

The X-37B is an "orbital test vehicle" that looks like a miniature space shuttle — it even used the old shuttle runway at NASA's Kennedy Space Center when it landed Sunday. To reach orbit, it rides on an Atlas V rocket.

This was the fourth mission for the reusable vehicle, and the first time it has landed in Florida. Earlier trips have ended at the Vandenberg Air Force Base in California.

Sunday's landing sparked a flurry of tweets and questions about the sonic boom, with The Orlando Sentinel reporting that before the landing, officials had refused to confirm rumors of a pending return to Florida. The Air Force announced the landing in a tweet — after it had occurred. By then, windows had been rattled and residents had been startled.

"But it wasn't just Central Floridians who heard the spacecraft," the paper says. "Reports came from as far away as Tampa and Fort Myers."

Confirmation of the landing was met with relief in at least one household, as a resident tweeted, "CENTRAL FLORIDA HAD A SONIC BOOM IM NOT CRAZY."

The space plane has been the object of frequent speculation about its potential military uses, particularly in either surveillance or some type of combat application, as NPR's Scott Neuman reported in a roundup of theories about the craft in 2014.

The Air Force says that the program includes the testing of many technologies, from guidance and control (Sunday's landing was autonomous) to thermal protection and advanced propulsion systems. The craft is powered by gallium arsenide solar cells with lithium-ion batteries.

The craft is managed by the Air Force Rapid Capabilities Office, which describes its mission as developing "combat support and weapon systems by leveraging defense-wide technology development efforts and existing operational capabilities."

The Air Force's public information about the craft focuses on its role in researching reusable space vehicles and establishing a "space test platform for the United States Air Force."

Military space programs "are as big as NASA," astrophysicist and astronomer Jonathan McDowell told NPR's Here and Now in 2015, when the X-37B left for its most recent mission.

At the time, McDowell said there are around 20 to 25 "full-fledged spy satellites or other really secret vehicles" that orbit Earth.

The concept of militarizing space is one that's still developing, McDowell said, noting the distinction between the use of satellites solely to support on-ground operations and their use to snoop on, and even interfere with, other satellites.

Civilian satellite spotters are able to track the more than 5-ton X-37B as it orbits Earth. Fueling theories that it aids surveillance programs, trackers found that at least one earlier mission followed an orbit that took it over countries that included Iran, Afghanistan and Pakistan.</s>(CAPE CANAVERAL, Fla.) — U.S. military officials say an unmanned aircraft orbiting Earth since May 2015 has landed in Florida.

The Air Force posted tweets that the X37B shuttle landed Sunday morning at the Kennedy Space Center in Cape Canaveral after 718 days in orbit.

Multiple media outlets reported that the 29-foot-long aircraft's return caused a sonic boom that rattled central Florida and could be heard as far away as Tampa and Fort Myers.

It's the shuttle's first landing in Florida. Previous X37B missions have landed at Vandenberg Air Force Base in California.

In a statement , officials said the X37B shuttle is "an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force." Another mission is scheduled to launch from Cape Canaveral later this year.</s>A X-37B orbital test vehicle, a U.S. Air Force-owned unmanned, reusable spacecraft, like the one seen in this 2011 photos, landed in Florida at the Kennedy Space Center in Cape Canaveral after 718 days in orbit.

CAPE CANAVERAL, Fla. — U.S. military officials say an unmanned spacecraft orbiting Earth since May 2015 has landed in Florida.

The Air Force posted tweets that the X37B spacecraft landed Sunday morning at the Kennedy Space Center in Cape Canaveral after 718 days in orbit.

Multiple media outlets reported that the 29-foot-long spacecraft's return caused a sonic boom that rattled central Florida and could be heard as far away as Tampa and Fort Myers.

It's the spacecraft's first landing in Florida. Previous X37B missions have landed at Vandenberg Air Force Base in California.

In a statement , officials said the X37B spacecraft is "an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force." Another mission is scheduled to launch from Cape Canaveral later this year.</s>A sonic boom in Central Florida was caused by the return of a military space shuttle. Here's video of the mini unmanned shuttle, known as X37B, being launched from Cape Canaveral on an Atlas V rocket on May 20, 2015.

Start the conversation, or Read more at South Florida Sun-Sentinel.</s>The Air Force posted tweets that the X-37B shuttle landed Sunday morning at the Kennedy Space Center in Cape Canaveral after 718 days in orbit.

Multiple media outlets reported that the 29-foot-long aircraft's return caused a sonic boom that rattled central Florida and could be heard as far away as Tampa and Fort Myers.

It's the shuttle's first landing in Florida. Previous X-37B missions have landed at Vandenberg Air Force Base in California.

In a statement , officials said the X-37B shuttle is "an experimental test program to demonstrate technologies for a reliable, reusable, unmanned space test platform for the U.S. Air Force." Another mission is scheduled to launch from Cape Canaveral later this year.

Explore further: US military spacecraft back on ground after 7 months</s>An unmanned military space plane landed at Kennedy Space Center Sunday with a sonic boom.

The reusable X-37B Orbital Test Vehicle's (OTV-4) return concluded an almost two-year mission in orbit, according to the US Air Force.

The Air Force tweeted shortly after 8am that the vehicle had landed safely, marking the conclusion of its fourth classified mission, which lasted more than 700 days.

OTV-4 launched from Cape Canaveral on a United Launch Alliance Atlas V rocket on May 20, 2015, reported Click Orlando.

Air Force officials have called the X-37B program 'the newest and most advanced re-entry spacecraft.' The program is managed by the Air Force Rapid Capabilities Office.

The two mini-shuttles have each completed two missions since their first launch from the Cape in 2010. Three of the prior X-37B landings occurred at the Vandenberg Air Force Base in California.

When the plane landed Sunday morning the sonic boom could be heard throughout Central Florida, and some Brevard County residents likely heard them before it even touched down at the Shuttle Landing Facility.

Air Force officials said that several technologies are being tested in the program.

'The primary objectives of the X-37B are twofold; reusable spacecraft technologies for America's future in space and operating experiments which can be returned to, and examined, on Earth,' an official said, according to Click Orlando.

Officials also explained that the X-37B is the first vehicle of its kind able to return experiments to Earth for further inspection and analysis. It is the first with this capability since NASA's Shuttle Orbiter.

The X-37B is able to stay in space longer because of its minimum on-orbit time of 270 days, officials said.
The United States Air Force's unmanned spacecraft X-37B successfully lands at Kennedy Space Center's Shuttle Landing Facility in Merritt Island, Florida, after spending a record-breaking 718 days in orbit. The landing was responsible for reports of sonic booms across central Florida.