William Atkins
Saturday, 14 February 2009 19:56
Science -
Space
Page 1 of 3
NASA officials have delayed the space shuttle Discovery launch from February 22 to 27 because they are still concerned with the shuttle’s fuel tank pressurization values. The mission is important to NASA and the world space community because its astronauts will install the last set of solar panels to complete the power grid for the International Space Station.
NASA spokesperson Allard Beutel, from the Kennedy Space Center in Florida, stated,
"More time was needed to complete analysis and testing.” [Reuters: “
NASA retargets Discovery launch for February 27”]
The actual wording for the launch of the STS-119 mission to the International Space Station is that
Discovery and its crew will not launch any earlier than February 27, 2009.
The three values to the three main engines must work properly while the orbiter lifts up into space. The space shuttle main engines (SSMEs), a part of the
Main Propulsion System of the orbiter, work for about 8.5 to 9.0 minutes during the ascent phase of shuttle missions.
During this time, the GH2 values control (synchronize) the proper flow (even pressure) of gaseous hydrogen (GH2) to a liquid hydrogen reservoir within the external fuel tank (ET) that eventually goes to power each of the three SSMEs.
Too much flow could cause the hydrogen gas to become overly flammable, while too little flow in one value could cause one of the main engines to shut down prematurely.
Either scenario is potentially dangerous to the crew during launch of a shuttle.
Page two describes these two scenarios in more detail.
