CAPE
CANAVERAL, Fla. - NASA engineers are meeting today determine whether to go
forward with the planned Sunday launch of the space shuttle Atlantis despite a
suspect fuel tank sensor system.
Top mission
managers are meeting to decide whether to proceed with a Sunday afternoon
launch for Atlantis with some stricter
flight rules in place, or take more time to study an intermittent glitch
with fuel
gauge sensors at the bottom of the orbiter's 15-story external tank.
"The
proposal's on the table," NASA shuttle program manager Wayne Hale said late
Friday. "We're very cognizant of the fact that you don't like to accept risk at
the launch site."
Commanded
by veteran shuttle flyer Stephen Frick, Atlantis' STS-122
crew is charged with delivering the European Space Agency's Columbus laboratory to the International Space Station (ISS). A Sunday launch attempt, if
approved, would lift off at about 3:21 p.m. EST (2021 GMT), with current
forecasts predicting an 80 percent chance of good weather.
Mission managers called off a Thursday
launch attempt after two of four engine cut-off sensors in the liquid
hydrogen portion of the shuttle's fuel tank failed a standard check. A third
sensor also acted later as the fuel tank was drained. NASA flight rules call
for three of the four sensors to be working properly in order to launch.
"We pretty
much came to the conclusion that we are in an area that we have got a suspect
system," said Hale, adding that the sensors are based on 1960s, Apollo-era
technology.
The sensors
serve as a backup system to shut down Atlantis' three main engines before its propellant
supply runs dry. Space shuttles consume more than 500,000 gallons (1.9 million
liters) super-chilled liquid hydrogen and liquid oxygen propellant during
launch.
NASA has wrangled
with the fuel sensor glitches since the agency resumed shuttle flight in 2005
following the Columbia tragedy. After modifying the sensors and adding extra
monitoring devices to ensure they work properly, NASA is still at a loss to
explain their intermittent behavior.
"We'd like to
have certainty," Hale said. "We would like to know root cause."
For Sunday's
launch attempt, NASA is looking at tightening the sensor rule to require all
four units to be working properly before attempting a liftoff. As an extra
measure, they may also shorten the daily five-minute launch window to one
single minute to conserve fuel in case the suspect sensors fail during flight.
"We don't
want to get launch fever," Hale said. "Even though the Columbus is out there
loaded in the payload bay and everybody is anxious for us to launch that guy,
we want to make sure that when we go launch, it is safe or as safe as it ever
is in this normally risky business."
NASA
will broadcast Atlantis' STS-122 mission live on NASA TV. Click here for SPACE.com's shuttle mission coverage and NASA
TV feed.
advertisement
