Live: No shuttle launch Feb. 27; no new date

Marathon meetings at the Kennedy Space Center have broken up and NASA managers could not reach a decision that would have allowed them to launch the space shuttle Discovery on Feb. 27 as planned. They have not decided on an official new launch date, so the mission's liftoff is in limbo.

NASA has a news conference set for 10:30 p.m., where managers will explain what happened and what comes next. They have decided however they will not launch next Friday. You can click the image above or the NASA TV player to the right of this post to watch the broadcast of that news conference live.

NASA's Kyle Hering says the agency is still evaluating whether the shuttle could liftoff by March 13, the beginning of a "cutout" period during which an orbiter could not visit the space station because of a planned Russian Soyuz mission. The cutout extends to April 6.

Editor's Note: At 10:37 p.m., NASA space operations chief said NASA needed to better understand the consquences of a failure of the questioned valves. He said there is a lot of "open" work before NASA could consider. "I am not even going to pick a target launch date at this time." He wanted to give the team "quality time" to go study the issues. Indeed, they called off work at the pad this weekend.

The mission was set to launch more than one week ago, and was most recently rescheduled for a Feb. 27 liftoff, but concerns about flaws in a fuel-pressurization system prompted a series of delays and extensive safety reviews involving engineers across the country.

Once launched, Discovery and her crew are bound for the International Space Station, where they would install the last piece of the outpost's central truss and a giant set of power-generating solar arrays.

Discovery is waiting at the pad for liftoff and the crew is trained and ready to go. They are simply awaiting the completion of the safety analyses and any possible redesign of the system ordered by NASA management.

At issue is the safety of three flow control valves which pop up like lawn sprinklers to help route hydrogen gas from the shuttle main engines through a pipe in the external tank. The gas helps maintain pressure inside the giant orange fuel tank as the rocket propellant is used up.

A tiny piece of one valve snapped off during Endeavour's launch in November. That concerned engineers and safety officials. Because even the smallest of debris inside shuttle fuel lines could rupture other delicate parts of the shuttle propulsion system. Other forms of failure could result in the tank over-pressurizing.

Either way, the worst-case outcomes could include explosion in flight or the premature shutdown of the engines. Any such circumstance could prove disastrous.

Read more about the flow control valves and see pictures in this fact sheet prepared by the space agency.