Air Force's Mysterious X-37B is The ongoing mission of the U. S. Air Force's robotic X-37B space plane is now the longest in the clandestine program's history.
As of today (March 25), the X-37B has spent 675 days on its latest Earth-circling mission, which is known as Orbital Test Vehicle-4 (OTV-4). The previous record was 674 days, set during OTV-3, which lasted from December 2012 to October 2014.
It's unclear what the new duration record will end up being; most X-37B activities and payloads are classified, and the Air Force has historically been tight-lipped about landing plans. [The X-37B's Fourth Mystery Mission in Photos]
"The landing date will be determined based on the completion of the program's on-orbit demonstrations and objectives for this mission, " Capt. AnnMarie Annicelli, an Air Force spokeswoman, told Space. com via email.
OTV-4 is still nowhere near the overall record for longest space mission, however. Some Earth-observation satellites have operated for decades; for example, Landsat-5 studied the planet from 1984 to 2013. And NASA's far-flung Voyager 1 and Voyager 2 probes are still sending data home, nearly 40 years after their 1977 launches.
Mini-shuttle mystery missions
The Air Force is known to have two X-37B vehicles, both of which were built by aerospace giant Boeing. The X-37B launches vertically and lands horizontally on a runway, just like NASA's now-retired space shuttle orbiters did.
The Air Force vehicle also looks like a miniature version of the space shuttle. Each solar-powered X-37B is just 29 feet (8. 8 meters) long and 9. 6 feet (2. 9 m) tall, with a wingspan of about 15 feet (4. 6 m). For comparison, the space shuttle was about 122 feet (37 m) long, with a wingspan of 78 feet (24 m).
Together, these two X-37Bs have flown four space missions to date, each of which has set a new duration record. OTV-1 launched on April 22, 2010, and landed on Dec. 3 of that year, spending a total of 224 days in orbit; OTV-2 lifted off on March 5, 2011, and wrapped up on June 16, 2012 (468 days); OTV-3 launched on Dec. 11, 2012, and landed on Oct. 17, 2014 (674 days); and OTV-4 lifted off on May 20, 2015. (The mission lengths of OTV-3 and OTV-4 may seem equivalent as of today, but the former landed about 2 hours shy of the full 675-day mark. )
The latest three missions have therefore blown past the space plane's designed orbital lifetime, which is just 270 days, according to the Air Force's X-37B fact sheet.
The secrecy surrounding the X-37B program has led to some speculation that the vehicle may be a space weapon. But this is unlikely to be true, experts say; for example, the space plane does not seem big enough or maneuverable enough to be used to manipulate other satellites.
Indeed, the Air Force has always stressed that the X-37B has two primary objectives: testing reusable spacecraft technologies, and helping to conduct experiments that can be returned to Earth for examination.
"Technologies being tested in the program include advanced guidance, navigation and control; thermal
protection systems; avionics; high-temperature structures and seals; conformal reusable insulation, lightweight electromechanical flight systems; and autonomous orbital flight, re-entry and landing, " Annicelli told Space. com, declining to offer details about OTV-4 in particular.
"Also, the Air Force Research Laboratory (AFRL), Space and Missile Systems Center (SMC) and the Air Force Rapid Capabilities Office (AFRCO) are investigating an experimental propulsion system, " she added. [The X-37B Space Plane: 6 Surprising Facts].
As of today (March 25), the X-37B has spent 675 days on its latest Earth-circling mission, which is known as Orbital Test Vehicle-4 (OTV-4). The previous record was 674 days, set during OTV-3, which lasted from December 2012 to October 2014.
It's unclear what the new duration record will end up being; most X-37B activities and payloads are classified, and the Air Force has historically been tight-lipped about landing plans. [The X-37B's Fourth Mystery Mission in Photos]
"The landing date will be determined based on the completion of the program's on-orbit demonstrations and objectives for this mission, " Capt. AnnMarie Annicelli, an Air Force spokeswoman, told Space. com via email.
OTV-4 is still nowhere near the overall record for longest space mission, however. Some Earth-observation satellites have operated for decades; for example, Landsat-5 studied the planet from 1984 to 2013. And NASA's far-flung Voyager 1 and Voyager 2 probes are still sending data home, nearly 40 years after their 1977 launches.
Mini-shuttle mystery missions
The Air Force is known to have two X-37B vehicles, both of which were built by aerospace giant Boeing. The X-37B launches vertically and lands horizontally on a runway, just like NASA's now-retired space shuttle orbiters did.
The Air Force vehicle also looks like a miniature version of the space shuttle. Each solar-powered X-37B is just 29 feet (8. 8 meters) long and 9. 6 feet (2. 9 m) tall, with a wingspan of about 15 feet (4. 6 m). For comparison, the space shuttle was about 122 feet (37 m) long, with a wingspan of 78 feet (24 m).
Together, these two X-37Bs have flown four space missions to date, each of which has set a new duration record. OTV-1 launched on April 22, 2010, and landed on Dec. 3 of that year, spending a total of 224 days in orbit; OTV-2 lifted off on March 5, 2011, and wrapped up on June 16, 2012 (468 days); OTV-3 launched on Dec. 11, 2012, and landed on Oct. 17, 2014 (674 days); and OTV-4 lifted off on May 20, 2015. (The mission lengths of OTV-3 and OTV-4 may seem equivalent as of today, but the former landed about 2 hours shy of the full 675-day mark. )
The latest three missions have therefore blown past the space plane's designed orbital lifetime, which is just 270 days, according to the Air Force's X-37B fact sheet.
The secrecy surrounding the X-37B program has led to some speculation that the vehicle may be a space weapon. But this is unlikely to be true, experts say; for example, the space plane does not seem big enough or maneuverable enough to be used to manipulate other satellites.
Indeed, the Air Force has always stressed that the X-37B has two primary objectives: testing reusable spacecraft technologies, and helping to conduct experiments that can be returned to Earth for examination.
"Technologies being tested in the program include advanced guidance, navigation and control; thermal
protection systems; avionics; high-temperature structures and seals; conformal reusable insulation, lightweight electromechanical flight systems; and autonomous orbital flight, re-entry and landing, " Annicelli told Space. com, declining to offer details about OTV-4 in particular.
"Also, the Air Force Research Laboratory (AFRL), Space and Missile Systems Center (SMC) and the Air Force Rapid Capabilities Office (AFRCO) are investigating an experimental propulsion system, " she added. [The X-37B Space Plane: 6 Surprising Facts].
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