The US space agency (Nasa) has launched a prototype rocket designed to replace the ageing space shuttle.

美国航空航天局新型试验火箭成功发射，该火箭旨在取代老化的航天飞机。

The Ares I-X blasted off（点火起飞） from Florida on a flight that will test technology for the development of a future manned launch vehicle.

The 100m-tall, syringe（注射器）-like rocket roared into the sky at 1530 GMT from Nasa's Kennedy Space Center.

The stick-thin launcher is the first Nasa has built in more than three decades, but its future is uncertain.

The $450m (300m euros; £275m) Ares I-X is what Nasa describes as a "Pathfinder" vehicle.

It was designed to climb about 40km (25 miles) into the sky during the powered phase（主动段） of its two-minute flight.

The I-X carried more than 700 sensors¹ to measure vehicle aerodynamics（空气动力学）, controls and performance of the rocket's first stage.

"This is a huge step forward for Nasa's exploration goals," said Doug Cooke, an associate administrator² at the space agency's headquarters in Washington DC.

"Ares I-X provides Nasa with an enormous amount of data that will be used to improve the design and safety of the next generation of American spaceflight vehicles - vehicles that could again take humans beyond low Earth orbit."

The top half of the rocket is a dummy³. What would be an upper stage, with a crew capsule and its emergency escape mechanism⁴, is actually a simulator made to the correct shape and weight.

After the two portions separated, parachutes（降落伞） were expected to open up, dropping the booster into the Atlantic, where recovery ships（宇航器回收舰） were waiting to retrieve⁵（恢复，补偿） it.

The upper, dummy portion of the rocket fell uncontrolled into the ocean and was destroyed on impact. These parts were not intended to be recovered.

Lightning strikes

The rocket was scheduled to launch on Tuesday, but the attempt had to be scrubbed（用力擦洗） due in part to bad weather.

Forecasters gave only a 40% chance of acceptable weather for Wednesday's launch attempt. Controllers had to wait for interfering⁶ clouds to clear, finally launching the I-X three-and-a-half hours into its lift-off window.

The rocket systems had to be re-tested after more than 150 lightning strikes were reported around the launch pad overnight.

A recent report has cast doubt on the future of the Ares programme.

The Augustine panel, which had been asked to review the US human spaceflight programme, published its report on 22 October.

Although the panel supported the Ares I-X test flight, it questioned the need to develop the launch vehicle.

In particular, the panel queried⁷ the cost and design of the craft as well as its development time.

The decision on the future of the Ares I and the rest of the Constellation⁸ programme now rests with President Barack Obama who is expected to give a response in coming weeks.