Orbital Sciences Corp., one of two private companies that currently hold a contract with U.S. space agency NASA to fly unmanned cargo missions to the International Space Station, completed a successful test launch of its new Antares rocket on Sunday.

　　The newest medium-class space launch vehicle in the U.S. lift off at 5 p.m. EDT (2100 GMT) from NASA's Wallops Flight Facility on Wallops Island, Virginia, followed by payload separation approximately 10 minutes later and mission completion at about 18 minutes after launch.

　　"The test flight demonstrated all operational aspects of the new Antares launcher, including the ascent to space and accurate delivery of a simulated payload to a target orbit of approximately 150 miles (about 250 kilometers)," said Virginia-based Orbital in a statement.

　　John Holdren, assistant to the president for science and technology, said that the flight "demonstrates an additional private space-launch capability for the United States and lays the groundwork for the first Antares cargo mission to the International Space Station later this year."

　　"With NASA focusing on the challenging and exciting task of sending humans deeper into space than ever before, private companies will be crucial in taking the baton for American cargo and crew launches into low-Earth orbit," said Holdren in a statement.

　　Orbital said it will now move forward toward completing a full flight demonstration mission of its new Antares system and Cygnus cargo delivery system to resupply the Space Station around mid- year.

　　Orbital signed a 1.9-billion-U.S.-dollar deal with NASA to fly eight unmanned supply missions using the Antares and Cygnus cargo delivery system.

　　Another U.S. company, California-based SpaceX, made history when its Dragon spacecraft became the first commercial vehicle in history to successfully attach to the space station in a May 2012 test flight.

　　Dragon has already made three trips to the space station and it still needs to complete another ten to fulfill its 1.6-billion- dollar contract with NASA. The next SpaceX cargo run is scheduled for September.

　　相关新闻：美国私营企业轨道科学公司21日成功将一枚“安塔瑞斯”号运载火箭发射升空。美国白宫发表声明表示祝贺。美国航天局局长查尔斯?博尔登说，这是美国商业航天发射的“又一个重要里程碑”。

　　当地时间17时许(北京时间22日5时许)，“安塔瑞斯”号从美国东海岸外的瓦勒普斯岛美国航天局基地点火发射。美国航天局电视直播画面显示，“安塔瑞斯”号从一片浓烟之中冲天而起，越飞越高，穿过淡淡的云雾，带着火光刺入蓝天。

　　大约10分钟后，“安塔瑞斯”号进入预定轨道，其搭载的“天鹅座”飞船模型与火箭成功分离。

　　美国总统科技顾问约翰?霍尔德伦在白宫祝贺声明中说，“安塔瑞斯”号的成功发射证明了美国又一家私营企业具有航天发射能力，这为轨道科学公司今年晚些时候将 “天鹅座”飞船送上国际空间站奠定基础。随着美国航天局将重心转移到更具挑战性的将人送入深空的任务上，私营企业将接过把宇航员和相关货物送入地球低轨道的接力棒。

　　美国航天局局长博尔登说，美国航天局希望倚仗美国本土企业运送给养和宇航员去国际空间站，因此今天的成功是“又一个重要里程碑”。

　　轨道科学公司原计划17日发射“安塔瑞斯”号，但发射前12分钟连接管线出现故障，发射被迫推迟到20日。而20日由于风力过大，因此改于21日发射。

　　轨道科学公司今年为“安塔瑞斯”号安排了两次试射，第二次试射计划于今年年中实施，届时“安塔瑞斯”号将尝试把该公司研制的“天鹅座”飞船送往国际空间站。

　　轨道科学公司已与美国航天局签署了19亿美元的合同，将向空间站发射8次货运飞船。若一切顺利，货运计划将于今年年底前开始实施。

　　美国政府还与另一家私营企业太空探索技术公司签署了16亿美元的合同，利用该公司的“龙”飞船向空间站运送货物。“龙”飞船至今已完成两次送货任务。

　　美国航天飞机2011年退役后，美国向空间站运送人员和货物需要依靠俄罗斯。为改变这种状况，美国航天局积极支持私营企业投身航天发射行业，鼓励它们建造能够向国际空间站运送人员和物资的航天器。“龙”飞船、“安塔瑞斯”号火箭和“天鹅座”飞船应运而生。此间舆论认为，美国的“商业航天”之路正逐渐形成。