NASA Restarts Launch Clock for Space Shuttle Discovery

CAPE CANAVERAL, Fla. - The countdownis on once again for the launch of the space shuttle Discovery, NASA's firstshuttle flight since the Columbia tragedy.

The clock began ticking down towardDiscovery's July 26 launch, currently set for 10:39 a.m. EDT (1439 GMT), exactly at noon Saturday as engineers, astronauts andmission managers prepare for their second launch attempt in almost two weeks.

Discovery's STS-114 flight has beendelayed since July 13, when launch controllers scrubbed the attempted spaceshot after a liquid hydrogen engine cut-off (ECO)sensorin the external tank failed a standard countdown test. A subsequent engineeringinvestigation found that wiring grounding issues that have since been repaired,NASA officials said.

"Discovery is in excellent shape,"said NASA test director Pete Nickolenko during apre-launch status briefing here at Kennedy Space Center (KSC). "We are all very confident that allof the engine cut-off sensors will work as they're designed to in this nextlaunch attempt."

Shuttle weather officer KathyWinters said there is only a 43 percent chance that rain and thunderstormscould prevent Discovery's Tuesday launch attempt. While forecasters continue towatch Tropical Storm Franklin, it should not be an issue for the planned spaceshot, she added.

During Discovery's July 13 launchattempt, the No. 2 liquid hydrogen ECO sensor failed to comply with a standardtest launch controllers run to make sure it and three other sensors are workingproperly. All four sensors are required to function properly under currentshuttle flight rules, and serve as an engine cut-off back up to make sureDiscovery's three main engines shut down before the external tank runs dry.Should the engines continue to fire without fuel, they could rip apart.

Orbiter engineers suspected that thegrounding issue, as well as electromagnetic interference from other hardware onDiscovery's launch stack, could lead to the sensor glitch that scrubbed theJuly 13 launch attempt. Tests to check eight potential sources of thatinterference, which included new heaters and cameras installed as safetymeasures after the Columbia accident, all turned up nominal, Nickolenko said.

Shuttle workers are now buttoning upDiscovery's aft compartment, home to a sensor electronics box that commandedmuch attention during the engineering investigation, and are preparing to loadthe cryogenic reactants that power the orbiter's fuel cells on Sunday.

Other than standard systemconfidence checks, no additional troubleshooting measures are expected, Nickolenko said.

"It makes us feel good that we cango into another launch attempt," he added.

In addition to fine-tuning threesuspect wire grounds, which failed shuttle specifications by just the slightestdegree, pad engineers also switched wiring connections between the No. 2 andNo. 4 liquid hydrogen ECO sensor to better understand the glitch.

"We think they have a great planthat they're going forward with," STS-114 mission commander Eileen Collins saidof the troubleshooting efforts Friday. "We have a lot of confidence in whatthey're doing."

  • Fixing NASA: Complete Coverage of Space Shuttle Return to Flight

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at:

Tariq Malik

Tariq is the Editor-in-Chief of and joined the team in 2001, first as an intern and staff writer, and later as an editor. He covers human spaceflight, exploration and space science, as well as skywatching and entertainment. He became's Managing Editor in 2009 and Editor-in-Chief in 2019. Before joining, Tariq was a staff reporter for The Los Angeles Times covering education and city beats in La Habra, Fullerton and Huntington Beach. In October 2022, Tariq received the Harry Kolcum Award for excellence in space reporting from the National Space Club Florida Committee. He is also an Eagle Scout (yes, he has the Space Exploration merit badge) and went to Space Camp four times as a kid and a fifth time as an adult. He has journalism degrees from the University of Southern California and New York University. You can find Tariq at and as the co-host to the This Week In Space podcast with space historian Rod Pyle on the TWiT network. To see his latest project, you can follow Tariq on Twitter @tariqjmalik.