NASA will decide Wednesday afternoon whether to try to launch shuttle Discovery the following day or perhaps delay its mission until early December so repairs can be made to one of its three liquid-fueled main engines.
Discovery and six astronauts now are tentatively slated for a 3:29 p.m. Thursday blast-off, but engineers still have to explain trouble with a circuit breaker that plays a key role in routing commands from the shuttle's primary flight computers to a computer that controls Discovery's Engine No. 3.
The engine controller failed to immediately power up during prelaunch checkouts Tuesday, an indication that the circuit breaker was not operating properly. The controller subsequently powered itself on and was in the midst of a self-test when engineers detected an small-but-unusual drop in voltage -- another sign the breaker might be faulty.
Mike Moses, chairman of NASA's prelaunch Mission Management Team, said dust or some type of contaminant might be keeping the circuit breaker from fully connecting with metal contacts. Similar problems have been resolved in the past by repeatedly turning power on and off, clearing any transient contaminant.
NASA engineers still are trying to pinpoint the exact cause of the two glitches, and they must develop a full understanding of the problem before the agency commits to proceeding with a countdown. The countdown will remain in the T-Minus 11-hour hold for the time being.
The Mission Management Team will meet at 2 p.m. Thursday. Engineers will brief them and then managers will decide whether to press ahead with external tank propellant-loading operations Thursday morning.
The weather forecast for launch on Thursday is not good. Air Force meteorologists say there is a 70 percent chance n approaching cold front will bring low-level clouds and rain into the Kennedy Space Center area at launch time -- conditions that would force NASA to scrub a launch attempt.
NASA must launch Discovery by Sunday or delay its International Space Station outfitting mission to early December. The sun angle on the station between Monday and Nov. 23 will be such that the outpost could not generate enough power and the shuttle could not dispel enough heat to complete the 11-day mission.
Then a three-person crew is departing the station Nov. 29, and a shuttle mission in that timeframe would interrupt that operation.
9 comments:
Don't think for a minute that the flight crew isn't slightly concerned about all the delays & what could happen if their systems fail. NASA really needs to work harder on finding a better system to generate enough power than setting launch dates relying on sun angles.
To 12:42 Its what they call ancient engineering.
To 12:42 - You must be the new guy? Been like this for 25 years.
Have a problem? Stop, fix it, launch.
They aren't making widgets out here ! If they aren't extremely cautious, they catch hell...if they're too cautious, they catch hell. Thank God they don't run the Space Program like Disney and play to the crowds.
Before the shuttle launches, mission planners calculate the angle defined by its orbital plane around Earth and a line drawn from the center of Earth to the center of the sun. This “solar beta angle” changes constantly as Earth moves around the sun and the shuttle’s orbital plane precesses, or slowly shifts, due to the gravitational tug from Earth’s equatorial bulge.
When the beta angle is less than 60 degrees, the shuttle spends a tolerable amount of time in sunlight; the vehicle heats up, but not too much, on the day side of its orbit, then cools off on the night side. When the beta angle is greater than 60 degrees, however, the shuttle must do slow barrel rolls to keep the sun from overheating one side. This “barbeque” mode also was used on the Apollo missions to the moon. Without it, propellant tanks on the sun side of the lunar spacecraft might have exploded.
When the shuttle is docked to the space station, it obviously can’t turn barrel rolls. So for the duration of these two-week visits, the station itself has to have a solar beta angle of less than 60 degrees.
On-orbit, the ISS uses the most abundant, reliable, and safe power source known to science - Solar Power. Unfortunately, solar power usage does requiring you to develop a power plan based on solar angles, and it adds the complication of a heating factor. All of those elements must be factored into flight plans.
Nothing about flying missions to LEO is routine or commonplace. Every mission takes thousands of dedicated professionals across the USA, Russia, Europe, and Japan to coordiante, communicate, and execute all phases of a mission.
Is it complex? Yes. Is it difficult? Yes. Is is rocket science? Yes. But, it is facing that level of challenge every day that forces us to push ourselves - test human resolve - and redefine the boundary of normal.
Anyone who thinks its ancient engineering or believes they know better ways to get the job done - join NASA and help them instead of sitting on the sideline criticizing. No one has ever erected a statue in honor of a critic.
Anonymous @ 9:27AM Join NASA now? You must be joking! Didn't you read the Headlines - NASA is laying off their so called dedicated professionals they pay so well. Commercialized space industry is highly motivated in challenging the complexities of rocket science. A little motivation goes a long way. Someone has to improve the redundancy NASA has fallen to in the last decade which finally ended our space program. Better to join a team that works towards progress than living on the fumes of past glory. No one has ever erected a statue to honor idleness either.
I would wait a couple of years before joining NASA.
Not a single NASA worker is getting laid off, or will be laid off. It's only contractors that are being let go.
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