US commercial cargo capsule arrives at space station

WASHINGTON - A privately owned Dragon capsule arrived at the International Space Station on Sunday morning after a technical hiccup, US space agency NASA announced.

According to NASA, astronauts aboard the outpost used the station's robotic arm to pluck the capsule from orbit at 5:31 a.m. EST as the ships sailed 250 miles over northern Ukraine. The capsule, built by the private spaceflight company SpaceX, was berthed to the Harmony module of the station at 8:56 a.m. EST. The hatch between the newly arrived spacecraft and the Harmony module of the space station is scheduled to be opened on Monday.

Dragon was scheduled to dock with the station on Saturday but a problem with its thruster rocket pods developed soon after reaching orbit. Shortly after the capsule separated from its rocket, SpaceX determined three of the capsule's four thruster pods -- which it would use to reach the station -- weren't operating. The problem appeared to be fixed by Friday afternoon.

The capsule is packed with tons of supplies for the International Space Station's six-man crew, including frozen mouse stem cells, 640 seeds of mouse-ear cress, a small flowering weed used in research, and tasty treats for the station crew picked from the orchard of a SpaceX employee's father.

Dragon is the only space station cargo craft designed to safely return to Earth, a critical capability that was lost when NASA's space shuttle fleet was retired in 2011. The Russian Soyuz spacecraft that ferry crews to and from the space station can only carry a few hundred pounds of small items back to Earth. All other station vehicles -- unmanned Russian Progress supply ships and European and Japanese cargo craft -- burn up during re-entry.

Before Dragon's liftoff, flights to the space station have always been a government-only affair. Until their retirement, US space shuttles carried most of the gear and many of the astronauts to the orbiting outpost. Since then, American astronauts have had to rely on Russian capsules for rides. European, Japanese and Russian supply ships have been delivering cargo.

NASA is looking to the private sector, in this post-shuttle era, to get American astronauts launching again from US soil. It will be at least four to five years before SpaceX or any other private operator is capable of flying astronauts.