The Dragon spacecraft is undergoing last minute preparations as it readies for a demonstration flight to the International Space Station (ISS).
Built by SpaceX, the unmanned Dragon will transport 1,200 pounds of cargo, including commemorative patches and pins, 162 meals and a collection of student experiments to the orbiting station.
Most of the cargo's weight, 674 pounds, is in food and crew provisions, including meals, crew clothing and batteries and other pantry items. A laptop and its accompanying accessories will also make the journey.
Tucked inside the Dragon capsule are two NanoRacks dedicated to student experiments that will study a range of microgravity-related areas from microbial growth to water purification. After liftoff, the 18-foot-high Dragon will approach the station only after its sensors and navigation systems are thoroughly checked.
Indeed, the spacecraft will undergo numerous tests during the third day of the flight as it passes within about 1.5 miles of the station. If all checks out, the spacecraft is scheduled to perform a methodical approach to the space station on the fourth day of the mission. The Dragon will first fly around the station at more than 6.2 miles and then fly under it no closer than 1.6 miles. With navigation units on the spacecraft and station relaying information, the Dragon is slated to approach slowly from beneath the station, pausing at several stages as systems are continually monitored.
The crew aboard the space station is set to briefly assume command of the Dragon to test the capsule's ability to retreat from the station. The spacecraft will subsequently move to a position about 700 feet from the station so controllers can determine whether it is safe to allow a closer rendezvous.
Assuming a "go" is given, the Dragon will close to within 98 feet of the station and pause again. The next step should bring Dragon to about 32 feet from the station, within reach of the robotic arm. Expedition 31 crewmember Don Pettit will steer the arm to latch onto the cargo craft and connect it to the Harmony module.
The station crew will unpack the Dragon during the next two weeks, loading the spacecraft with more than 1,400 pounds of used scientific and spacewalking gear. Dragon will then be removed from the station by the arm and released to fly back to Earth.
Unlike the other cargo vehicles that resupply the station, the commercial SpaceX craft is designed to return to Earth safely instead of burning up in the atmosphere. That means experiments and other equipment can be stowed inside the capsule and returned to scientists.