The ever-intriguing X-37B space plane is slated for its fourth mission in May, this time to experiment with a propulsion system for military satellites, the Air Force announced this week. The target launch date is May 20, according to multiple news sources. The military has revealed little about past missions, prompting broad speculation about what experiments have occurred on the craft. This time, the Air Force says the upcoming flight will be used to test a Hall thruster, an electric device that produces thrust using a gas, such as xenon. While not as powerful as conventional rocket engines, the Hall thruster offers better fuel economy, thus increasing payloads and maneuvering ability. The test device is a new version of the thruster, the Air Force said.
The unmanned X-37B, only 29 feet long, has cargo space about the size of a pickup truck. So far it hasaccumulated 1,367 days in orbit, landing at Vandenberg Air Force Base in California. It last returned in October after 674 days, and the military did not release specifics. It’s unclear how long the next flight will last or if there are other experiments set to take place. For the last mission, the spacecraft launched aboard an Atlas 5 rocket from Cape Canaveral in Florida.
