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How early can a scrub be decided ?



 
 
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  #1  
Old July 1st 06, 03:17 AM posted to sci.space.shuttle
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Default How early can a scrub be decided ?

The status report shows a 60% change of weather not permitting a launch
on saturday and similar stats for sunday.

As I recall, the decision is usually made during the t-9 minutes hold.

Are there rules/procedures that cause NASA to decide on a no-go much
earlier ? For instance, if the weather service predicts a 90% chance of
weather prohibiting launch, would NASA still go ahead with the filling
of the ET (a rather expensive endeavour and one which is stressful to
the aluminium and foam) ?

Or is the only time NASA might look at weather is during the T-9 hold
because ot is only then that weather becomes part of a go/no-go to
proceed with resumption of countdown ?

Also, since the shuttle launch procedures were written back in the late
1970s, would it be fair to assume that weather prediction accuracy has
improved significantly ? Does a "60% chance of weather violating rules"
24 hours before launch in 2006 provide significantly more authoritative
data than back in 1982 ?

If, 3 or 4 days before a launch, they predict a hurricane may hit/skirt
the launch site on the launch day, I take it NASA would postpone the
launch and batten down the hatches to prepare the stack to widthstand
the storm ? Is there a defined "line" above which NASA postpones the
flight, and below wich NASA continues with all preparations in the hopes
that 9 minutes before launch, the clouds might hopefully be far enough
away ?
  #2  
Old July 1st 06, 03:39 AM posted to sci.space.shuttle
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Default How early can a scrub be decided ?

John Doe wrote in :

The status report shows a 60% change of weather not permitting a launch
on saturday and similar stats for sunday.

As I recall, the decision is usually made during the t-9 minutes hold.

Are there rules/procedures that cause NASA to decide on a no-go much
earlier ? For instance, if the weather service predicts a 90% chance of
weather prohibiting launch, would NASA still go ahead with the filling
of the ET (a rather expensive endeavour and one which is stressful to
the aluminium and foam) ?


I've seen NASA scrub a launch at the tanking meeting.


--
JRF

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check "Organization" (I am not assimilated) and
think one step ahead of IBM.
  #3  
Old July 1st 06, 03:57 AM posted to sci.space.shuttle
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Default How early can a scrub be decided ?

FYI

As of last night, it was 60%, that has changed as of 10am this morning
and has held all day to 20%.

If anyone is heading down.. Look for me at Indian River!!!! WOHOOO!


Jorge R. Frank wrote:
John Doe wrote in :

The status report shows a 60% change of weather not permitting a launch
on saturday and similar stats for sunday.

As I recall, the decision is usually made during the t-9 minutes hold.

Are there rules/procedures that cause NASA to decide on a no-go much
earlier ? For instance, if the weather service predicts a 90% chance of
weather prohibiting launch, would NASA still go ahead with the filling
of the ET (a rather expensive endeavour and one which is stressful to
the aluminium and foam) ?


I've seen NASA scrub a launch at the tanking meeting.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.


  #4  
Old July 1st 06, 05:12 AM posted to sci.space.shuttle
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Default How early can a scrub be decided ?

On 30 Jun 2006 19:57:17 -0700, "Signalman1968"
wrote:

FYI

As of last night, it was 60%, that has changed as of 10am this morning
and has held all day to 20%.


I'm not sure where you got that. NASA is still saying the weather
forecast is 60% no-go.

http://www.nasa.gov/multimedia/podca...ranscript.html

Of course, I was at the STS-93 launch the night NASA promised "100%
chance of good weather." They scrubbed because of lightning storms
offshore.

You can never tell. Good luck tomorrow!

Brian
  #5  
Old July 1st 06, 02:22 PM posted to sci.space.shuttle
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Default How early can a scrub be decided ?

On Fri, 30 Jun 2006 22:17:12 -0400, John Doe wrote:

Does a "60% chance of weather violating rules"
24 hours before launch in 2006 provide significantly more authoritative
data than back in 1982 ?



Not if the forecasts are anything like the ones for where I live now
(Northern Alabama). Here, a 60% to 80 % chance of rain for several
days in a row usually means it might be overcast and windy, but will
be completely dry. Yesterday, I think we had a zero chance of rain and
had a thunderstorm and heavy downpour in the evening. We definitely
needed the rain.

Sometimes, I think they have gotten over sophisticated in trying to
predict weather with complex computer models and are actually less
accurate in some physical locations. I was raised in Macon Georgia
(near Robins Air Force Base) and have lived in Tallahassee Florida
among other places. Maybe the weather was just easier to predict in
Middle Georgia and in Florida. Usually, if you just reported afternoon
thundershowers during summer, it would be hard to miss. People
(including a friend of mine) were always crashing private planes in
South Georgia because of the sudden thunderstorms.

When I lived in Northern California at around 2000 - 2400 foot
altitude, they could have gotten by with 2 predictions, rain or
snow/ice almost all winter transitioning to hot and completely dry all
the summer. It was strange to be able to go a year without hearing
thunder. The snow predictions were kind of cute. Since the town
climbed a few hundred feet from one end to another and the altitude
above which they expected snow often fell within that range, they'd
just say what major cross street the snow was supposed to start at.

Like you, I'm worried about all that tanking and de-tanking of Cryo
fuels, especially after they were afraid to do a tanking test to check
those fuel level switches in the ET, because they were concerned about
an extra tanking meaning possibly extra foam cracking.

I was a bit surprised they tried to launch this early in the month
since there had been some talk that the lighting conditions to get
good pictures during ET separation wouldn't be all that great until
the 4th or 5th.

-- David
 




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