WASHINGTON — The U.S. Air Force’s secret X-37B spaceplane embarked on its fourth mission May 20 after it launched from Cape Canaveral Air Force Station, Florida, aboard a United Launch Alliance Atlas 5 rocket.

The Air Force does not discuss the X-37B missions, which can last well over a year, beyond acknowledging the program and releasing photographs of the two orbital vehicles, built by Boeing Space and Intelligence Systems of El Segundo, California. Resembling mini space shuttles, the spaceplanes launch vertically atop expendable rockets, are capable of maneuvering on orbit, and then re-enter the atmosphere and glide back to Earth for a runway landing.

The Atlas 5 launched the Air Force Space Command 5 mission at 11:05 a.m. and ULA confirmed a successful launch about 90 minutes later. Around 1:20 p.m., ULA confirmed the cubesats deployed.

The Atlas 5 configuration used in the launch featured a 5-meter payload fairing and a Centaur upper stage featuring one RL-10C-1 engine, the sixth time such a setup has been used.

The rocket also carried a secondary payload consisting of 10 cubesats, one of which is the LightSail solar sail experiment designed by the Planetary Society.

“Today is an extraordinary day for The Planetary Society, our members, and space enthusiasts around the world: LightSail successfully launched into orbit,” Bill Nye, chief executive of the advocacy group, said in a May 20 press release. “While we celebrate this step, LightSail’s biggest tests are still ahead. Over the next days, we will be monitoring our CubeSat as we prepare for the big show: the day LightSail deploys its super shiny Mylar sails for flight on sunlight.”

Below is some additional information about this mission in particular and about the X-37B in general:

• The 10-cubesat package carried aloft by the Atlas 5 is known as the Ultra Lightweight Technology and Research Auxiliary Satellite, or ULTRASat, mission. Nine of those cubesats are sponsored by the U.S. National Reconnaissance Office (NRO), which manages the nation’s spy satellites. NASA sponsored the LightSail mission, which will demonstrate an on-orbit deployment mechanism for a solar sail. Of the NRO-sponsored cubesats, three were built by the U.S. Naval Academy, three by the California Polytechnic State University, two by the Aerospace Corp. and one by the U.S. Air Force Research Laboratory. One of the Aerospace Corp. cubesats will test on-orbit propulsion technology.

The NRO has published additional information on the cubesat missions on its website.

The Air Force's AFSPC-5 payload, encapsulated inside a 5-meter diameter payload fairing, is mated to an Atlas V booster inside the Vertical Integration Facility or VIF at Cape Canaveral Air Force Station's Space Launch Complex-41. Credit: United Launch Alliance.
The Air Force’s AFSPC-5 payload, encapsulated inside a 5-meter diameter payload fairing, is mated to an Atlas 5 booster inside the Vertical Integration Facility at Cape Canaveral Air Force Station’s Space Launch Complex-41. Credit: United Launch Alliance.
The Air Force’s AFSPC-5 payload, encapsulated inside a 5-meter diameter payload fairing, is mated to an Atlas 5 booster inside the Vertical Integration Facility at Cape Canaveral Air Force Station’s Space Launch Complex-41. Credit: United Launch Alliance.

• Although the Air Force isn’t saying anything about the X-37B’s mission, ULA said the vehicle is providing “reusable spacecraft technologies for America’s future in space and operating experiments which can be returned to, and examined, on Earth.” Brian Weeden, a former Air Force officer specializing in space surveillance who now works as a technical adviser at the Secure World Foundation, has said the spaceplane likely is used both for reconnaissance, and for testing guidance and thermal protection systems for reusable spacecraft. Although the X-37B features an on-orbit maneuvering capability and a cargo bay, Weeden said it is unlikely the vehicle is being used for up-close inspection, repair or retrieval of space objects.

• During an interview that recently aired on CBS News’ “60 Minutes,” Gen. John Hyten, commander of Air Force Space Command, said the X-37B is being used “really for cool things” in orbit. “It goes up to space but unlike other satellites, it actually comes back,” he said. “Anything that we put in the payload bay that we take up to space we can now bring back. And we can learn from that.” As for the future of the program, Hyten said, “I’m not going to say what it’s going to become —because we’re experimenting.”

• The Air Force isn’t discussing the duration of the upcoming mission, but the vehicle is carrying a NASA materials exposure experiment in its cargo bay that the civilian space agency says will spend at least 200 days in orbit. The X-37B vehicles have flown a combined three missions to date, each lasting longer than the previous one. On its last mission, the vehicle spent 674 days in space.

• The previous X-37B missions launched from the Cape and landed at Vandenberg Air Force Base, California. Capt Chris Hoyler, an Air Force spokesman, said “work is still ongoing to stand-up Florida as a landing site for the X-37B, and Vandenberg AFB is still being maintained as a landing location.”

• The X-37B program “selects the orbital test vehicle for each activity based upon the experiment objectives,” Hoyler said.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.