NASA delayed the launch of space shuttle Discovery for a fourth time on Friday amid valve concerns, and managers are uncertain when the flight will take place. Following a 13-hour meeting at Kennedy Space Center, shuttle managers decided against launching next week. The launch had been targeted for no sooner than Feb. 27; no new date was set. Officials said they believe they have a realistic shot at launching Discovery to the international space station before mid-March. After that, the shuttle would have to get in line behind a Russian Soyuz launch with a new space station crew, and the next opportunity for Discovery would be after April 6, Associated Press reported. NASA originally hoped to send Discovery to the space station, with one final set of solar wings, on Feb. 12. But extra tests were ordered for the valves that control the flow of hydrogen gas into the external fuel tank during liftoff. One of those valves broke during the last shuttle launch in November.
