The U.S. Air Force X-37B UOV (unmanned orbital vehicle) is scheduled to go into space for the sixth time in mid-May, seven months after the other X-37B returned from its last, and longest (25.5 months) mission. The X-37B has been doing this for a decade now, going into orbit for the first time in April 2010, for over seven months. Each subsequent launch (March 2011, December 2012, May 2016 and September 2017) kept the X-37B in orbit longer (225 days then 469, 675, 718 and 780). There are actually two X-37B “space planes” so they are not putting the same one back into orbit soon after it returns.
One unanswered question is; what does X-37B do up there? The X-37B operations are classified secret and little information about what happens in orbit is released. The most recent X-37B mission caused a problem when the air force mentioned that the X-37B had carried and released three cubesats (very small satellites) that were not registered with the UN. That X-37B was known to be carrying ten cubesats to be released into orbit to perform various experiments. Cubesats are technically U Class spacecraft that can be no larger than 10 cm (about four inches) square and weigh no more than 1.33 kg (2.9 pounds). Cubesats are increasingly popular for science experiments by smaller organizations, or even individuals, that cannot afford a multi-million dollar satellite that is ten or more times larger and heavier than a cubesat. So far over 1,200 cubesats have been launched since 1998, with about 93 percent reaching orbit. That number is expected to double in the next few years because more and more commercial satellite launchers are providing unused space and weight on their launcher rockets for carrying and launching some cubesats. In some cases the cubesat owners pay for this service while in other cases some cubesats are taken up for free, as a public service. The U.S. is accused of using the unregistered cubesats launched from the X-37B as a test of a new anti-satellite weapon. A cubesat placed in the proper orbit could intercept and destroy or disable a much larger satellite. Or so the theory goes. The U.S. Air Force has no comment although two senior air force officials did mention, in 2019, that there were some secret anti-satellite projects under way. An anti-satellite weapon that is kept secret is more effective when used because the enemy doesn’t know what to prepare for.
America, Russia and China are the major players in orbital space and ASAT (anti-satellite weapons) development. This is mainly because these three countries own or operate most of the commercial and military satellites up there. Some other countries are active with ASAT as well. In March 2020 India tested an ASAT weapon when they launched one of their anti-missile missiles with the third stage “interceptor” reconfigured to hit an object in orbit rather than an ICBM warhead plunging towards earth. The target was a small Indian satellite launched in 2019 into a low (280 kilometers) orbit. This meant that when the ASAT warhead hit the satellite the resulting debris (hundreds of fragments) would soon fall to earth and burn up in the atmosphere. The target satellite was apparently launched just to be an ASAT target.
China conducted a similar test in 2007, but destroyed one of their own satellites that was no longer functional and in a higher orbit. The Chinese ASAT test debris are still in orbit and China is still criticized for this test. Other nations, including the big three, are working on ground bases electronic weapons for disabling satellite. Russia has some ambitious ASAT plans but no money to build their airborne ASAT laser (to blind or destroy low orbit spy or communications satellites), or the orbital satellite jammer powered by a nuclear reactor. Russia can afford more ground based jammers and such and they putting as much money as they can into that. So is China, which has a lot more cash. But so are nations like Japan and even less affluent states like North Korea and Iran.
And then there’s the mysterious X-37B. It is unmanned and operated by earth-based controllers. It does have automatic landing software that has been used several times without any problems. While the air force reports few details about the X-37B it was difficult to hide the fact that mission 5 used a different launch vehicle; the SpaceX booster. This was important because the SpaceX rocket itself is reusable and the first stage returns to earth and lands upright for refurbishing and reuse. Air force officials noted that the SpaceX design is a fitting match for X-37B which was designed for multiple reuse and autonomous operation. Mission 5 was apparently similar to Mission 4 in that new technologies were tested and more micro-satellites were placed in orbit, including the unregistered cubesats, which are the smallest class of satellites.
Mission 6 was originally scheduled for late 2019, using the disposable Atlas 5 launch vehicle normally employed but probably on its way out. SpaceX is cheaper and has a growing list of successful landings including twelve successes in a row, including all ten in 2017. The SpaceX landing tests began in 2010.
It was eventually revealed that mission 4 tested a new thruster system for mobile satellites that needed to be tried out while in orbit. Also carried were dozens of different materials, possibly including some new spy satellite components to see what the harsh environment in orbit, especially the radiation can do. Such exposure can have unpredictable effects on materials and microelectronics after prolonged time in space.
Earlier missions were also successful. The third X-37B mission ended in October 2014 after nearly two years in orbit. The second mission landed on June 16th 2012 after 15 months in orbit. The first mission ended on December 3rd 2010 after seven months in orbit. The official endurance of the X-37B was originally about nine months (280 days). The real endurance appears to be 3-4 times that, at least. The long endurance is largely because the X-37B carries a sizable solar panel, which is deployed from the cargo bay, unfolded and produces enough power to keep the X-37B up there for a long time. The air force has not made public much about what the X-37B has been doing up there for nearly 2,000 days so far.
In effect the X-37B is a remotely controlled mini-Space Shuttle. The space vehicle, according to amateur astronomers (who like to watch spy satellites as well), appears to be going through some tests much of the time. The X-37B is believed to have a payload of about 227-300 kg (500-660 pounds). The payload bay is 2.1x1.4 meters (7x4 feet). As it returned to earth, it is designed to land by itself after being ordered to use a specific landing area. The X-37B weighs five tons, is nine meters (29 feet) long and has a wingspan of 4 meters (14 feet). In contrast the Space Shuttle was 56 meters long, weighed 2,000 tons and had a payload of 24 tons.
The X-37B is a classified project, so not many additional details were expected to be made available. It's been in development since 2000 but work was slowed down for a while because of lack of money. Whatever the X-37B is now doing up there has been convincing enough to get Congress to spend over a billion dollars on it. What makes the X-37B so useful is that it is very maneuverable, contains some internal sensors (as well as communications gear), and can carry mini-satellites, or additional sensors, in the payload bay. The X-37B is believed capable of serving as a platform for attacks on enemy satellites in wartime. Using a remotely controlled arm, the X-37B could refuel or repair other satellites. All this is estimates because, as a classified project, there is little confirmed information about its payload or mission, other than testing the system on its first mission. It is likely that future missions will involve intelligence work, and perhaps servicing existing spy satellites, which use up their fuel to change their orbits. For regular satellite refueling missions a larger “X-37C” would probably be used. This is a scaled up X-37B that would have a much larger (probably over a ton) of payload. The X-37C could be quickly switched between cargo and passenger configurations. The X-37C would still be robotic and not require anyone onboard to control it. Work on the X-37C has apparently been halted because there are similar alternative designs that are closer to service.
The X-37B also demonstrated that it could not be easily tracked while in orbit although at times the X-37B could be elusive for amateur astronomers. The international collection of amateur sky watchers have proved remarkably adept at spotting orbital objects in the past, including classified ones like the X-37B. The amateur orbital observer community has concluded that one thing the X-37B tested was how well it could constantly switch positions, and stay hidden. In that respect, the X-37B was a resounding success. That's because these amateur observers are generally very good at tracking what's up there.
One notable incident occurred in 2008 when a U.S. spy satellite fell out of orbit, apparently because of a failure in its maneuvering system. The amateur astronomers were able to track it. If this had not been an American reconnaissance satellite, there would have been no media attention to this, because 4-5 satellites a month fall back to earth. Since most of the planet is ocean, or otherwise uninhabited (humans like to cluster together), the satellites tend to come down as a few fragments, and rarely is anyone, or anything manmade, hit.
Before the Internet became widely used after 2000 you heard very little about all these injured or worn out space satellites raining down on the planet. But with the Internet, the many thousands of amateur astronomers could connect and compare notes. It was like assembling a huge jigsaw puzzle. Many sightings now formed a pattern, and a worldwide network of observers made visible the movements of hundreds of space satellites. These objects were always visible at night, sometimes to the naked eye, but unless you knew something about orbits and such, they could be difficult to keep track of. These days, a lot of the activity is posted and discussed at http://www.satobs.org/. But the X-37B has proved elusive, and sometimes became a frustrating challenge to the amateur sky watchers. This is pleasing to American air force officials, who designed the X-37B to be elusive to terrestrial observation and the dedicated (and quite effective) amateur satellite watchers gave the X-37B quite a workout.