Image: X-37B space plane
NASA/MSFC
NASA's Marshall Space Flight Center image shows on-orbit functions for the reusable X-37 space plane, now under the wing of the U.S. Air Force.
By
updated 3/6/2012 4:54:48 PM ET 2012-03-06T21:54:48

The U.S. Air Force's robotic X-37B space plane has celebrated a silent anniversary, surpassing an entire year in Earth orbit on a mystery mission for American military. Meanwhile, a third X-37B space plane mission is being readied, and could even launch later this year, Space.com has learned.

The X-37B space plane currently orbiting Earth is the second spacecraft of its kind built for the Air Force by Boeing’s Phantom Works. Known as the Orbital Test Vehicle 2, or OTV-2, its classified mission is under the wing of the Air Force Rapid Capabilities Office.

The robotic X-37B space plane is a reusable spacecraft that resembles a miniature space shuttle. The Air Force launched the OTV-2 mission on March 5, 2011, with an unmanned Atlas 5 rocket lofting the space plane into orbit from the Cape Canaveral Air Force Station in Florida.

"We are very pleased with the results of ongoing X-37B experiments," Air Force Lt. Col. Tom McIntyre of the Air Force Rapid Capabilities Office told SPACE.com. "The X-37B program is setting the standard for a reusable space plane and, on this one-year orbital milestone, has returned great value on the experimental investment," he told SPACE.com. [ Photos: Inside the X-37B Mission ]

What the robotic space plane has been doing in orbit for so long remains a mystery, since Air Force officials have not commented on the flight's details due to its classified nature. Outside experts, however, have suggested that the flight is testing the limits of the X-37B space plane, or possibly serving as an orbital spy platform.

McIntyre dropped no hints, except to suggest that the next X-37B flight could launch later this year.

"Upon completion of all objectives, we look forward to bringing the mission to a safe, successful conclusion. The next program phase, the third X-37B mission, has been tentatively planned for the fall of 2012," McIntyre said.

Each X-37B space plane is about 29 feet (8.8 meters) long and 15 feet (4.5 meters) wide. It has a payload bay about the size of a pickup truck bed. It is outfitted with a deployable solar array power system. What’s inside that payload bay, and what functions they serve, are classified.

Like NASA's now-retired space shuttle, the X-37B space planes are capable of returning experiments to Earth for inspection and analysis, as well as re-flight of equipment.

One year in space
The maiden voyage of an X-37B space plane, the OTV-1 mission, launched in 2010 on a flight that lasted 225 days. That initial mission spacecraft lifted off on April 22 and landed on Dec. 3, gliding onto a specially prepared runway at Vandenberg Air Force Base in California.

So far, the OTV-2 mission has set an endurance record for the X-37B space plane — one that gets longer with each passing day — and the spacecraft is in good health, Air Force officials said.

According to Air Force Maj. Tracy Bunko, a Pentagon spokesperson for the X-37B program, "the mission is still on track and the vehicle is performing well."

Bunko said the flight of the vehicle is being extending as circumstances allow, in order to obtain maximum value out of the mission. "We don’t know when we'll land, but we regularly evaluate that based on test objectives."

The X-37B space plane originated as a NASA spacecraft research project, but lack of funding led the agency to transfer the program to the Defense Advanced Research Agency in 2004. The Air Force took control of the project in 2006, and has launched two apparently successful missions so far.

Skywatchers track space plane
Ted Molczan, a Toronto, Canada-based satellite watcher and spacecraft analyst, offered his view of what the X-37B space plane might be up to.

  1. Space news from NBCNews.com
    1. KARE
      Teen's space mission fueled by social media

      Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

    2. Buzz Aldrin's vision for journey to Mars
    3. Giant black hole may be cooking up meals
    4. Watch a 'ring of fire' solar eclipse online

"I do not know OTV-2's mission, but its frequently repeating ground track may be a clue that it is gathering imagery intelligence. Ground tracks that repeat at intervals of two, three or four days have long been favored for U.S. imagery intelligence satellites, because they enable frequent monitoring of targets of interest," Molczan told Space.com.

In an Internet posting to his fellow amateur skywatchers, Molczan said the X-37B's altitude has changed little since launch, and it has been at about 331 kilometers by 342 kilometers.

The OTV-2 spacecraft's ground track repeats after every 31 revolutions, in just under two days, Molczan added. The mission of the first X-37B vehicle operated in several different orbits, most of which repeated every two to four days, he said.

Molczan and other skywatchers have also managed to catch video of the X-37B space plane in orbit as it sailed across the night sky.

Whenever this second X-37B mission concludes, the craft is designed to make a "do-it-itself" guided entry and wheels-down runway landing at Vandenberg Air Force Base in California. An alternate desert landing site is neighboring Edwards Air Force Base, Calif., mission officials have said.

Leonard David has been reporting on the space industry for more than five decades. He is a winner of last year's National Space Club Press Award and a past editor-in-chief of the National Space Society's Ad Astra and Space World magazines. He has written for Space.com since 1999.

© 2013 Space.com. All rights reserved. More from Space.com.

Photos: Month in Space: January 2014

loading photos...
  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
  1. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  2. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  3. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

  4. Editor's note:
    This image contains graphic content that some viewers may find disturbing.

    Click to view the image, or use the buttons above to navigate away.

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments