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T-43 Hours and Counting

Posted by timothy on from the prepare-the-tax-dollar-machine dept.

An anonymous reader submits "As seen on NASA TV, for the first time in over two years, the countdown clock has started at 6:00 PM EDT for the Wednesday 3:51 PM EDT launch of Space Shuttle Discovery on the first of the return to flight test flights. The launch is not for certain due to weather issues associated with hurricane Dennis. Currently it is estimated for a 70% chance of launch on Wednesday, with the chances lowering later in the week. If you are confused on how T-43 hours equals almost 3 days, perhaps you should read Countdown 101."

6 of 192 comments (clear)

  1. Re:Can someone please explain by battamer · · Score: 5, Informative

    Time. As in liftoff time. Before the liftoff, the clock regesters as "T minus ..." after liftoff it regesters as "T plus..."

  2. Link to the actual TV Schedule by OverlordQ · · Score: 3, Informative

    Linkeh.

    Information about tuning in to NASA TV can be found here as well.

    --
    Your hair look like poop, Bob! - Wanker.
  3. Re:Can someone please explain by iamlucky13 · · Score: 3, Informative

    It makes more sense if you say the whole phrase:

    T minus 43 hours = launch time minus 43 hours

  4. Re:T-19 Hours... by richdun · · Score: 3, Informative

    lol...

    Umbilicals provide power and such to the shuttle while it is on the pad. The shuttle's batteries/fuel cells provide enough power for the mission, but they like to run it on Earth-based power for as long as possible before setting it on its own power.

    Just think of "Demate the orbiter's midbody umbilical unit" as "Unplug laptop" before taking it off your desk. I know, not so sexy, but just imagine the laptop is a Powerbook G5 or an Alienware Media Center laptop that is liquid cooled, overclocked, and only 1" thin/5 lbs., whichever daydream is your preference.

  5. Still confused ... by dougmc · · Score: 3, Informative
    If you are confused on how T-43 hours equals almost 3 days, perhaps you should read Countdown 101."
    I had to read Countdown 101 a few times before I realized what I was missing. It's the ... and holding periods that make up the difference. I guess when they start working on those things, the clock stops. Which seems very odd, but I guess they're just not sure how long they'll take.
  6. Re:So.. What does.. by lommer · · Score: 4, Informative

    T- stands for "Time minus". "Time" is when the main event occurs (the shuttle liftoff). All other times are specified as relative to this event. Thus, T minus 3 minutes is (theoretically) three minutes before the shuttle lifts off, and T plus 6 hours is 6 hours after the shuttle lifts off. The military uses this convention for operations too (e.g. D-Day plus 6 is 6 days after D-Day). This system is good because it allows things to be scheduled without knowing exactly when the main event is going to occur (the launch could be delayed by weather, etc).

    The system isn't perfect though, which is why you have "holds" for some things. These "holds" allow time for activities whose duration is really difficult to predict.