NASA plan to alter STS-120 launch countdown

[Chris Bergin]

http://www.nasaspaceflight.com/content/?cid=5224

[TJL]

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

[Chandonn]

Another good article!

Actually, I think shaving the hold time reduces the tendency to begin tanking early.  I believe there have sometimes been issues with ground equipment at the start of tanking so they tend to go for an early start.

[ChrisGebhardt]

Isn't ET-120 flying with STS-120?

[psloss]

Trekkie07 - 9/9/2007  7:14 PM

Isn't ET-120 flying with STS-120?

Yes.

[nathan.moeller]

TJL - 9/9/2007  5:53 PM

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

I could be wrong, but I believe the tanking process takes place in the T-3 hour hold.  Someone correct me if that's incorrect.

[psloss]

nathan.moeller - 9/9/2007  7:50 PM

I could be wrong, but I believe the tanking process takes place in the T-3 hour hold.  Someone correct me if that's incorrect.

It roughly starts when the clock resumes at T-6 hours, or at least that's the plan.  The hold at T-3 hours allows for some catch up (like STS-97 or the second STS-116 tanking, although those are extreme cases), but usually the tank is full around the time the count gets there.

Is the launch time still going to be the same or is it going to be moved forward if this plan is taken into effect?

[Jim]

TJL - 9/9/2007  6:53 PM

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

Changing holds is easier wrt to documents. The countdown procedure is written per T minus time

[mkirk]

Jim - 9/9/2007  7:29 PM

TJL - 9/9/2007  6:53 PM

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

Changing holds is easier wrt to documents. The countdown procedure is written per T minus time

This also preserves trouble shooting time for anomalies that arise during the loading process and Final Inspection Team activities.

Mark Kirkman

[mkirk]

Justin Wheat - 9/9/2007  7:23 PM

Is the launch time still going to be the same or is it going to be moved forward if this plan is taken into effect?

No this will not effect (affect ?) the T-0 time.

Mark Kirkman

[mkirk]

nathan.moeller - 9/9/2007  6:50 PM

TJL - 9/9/2007  5:53 PM

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

I could be wrong, but I believe the tanking process takes place in the T-3 hour hold.  Someone correct me if that's incorrect.

Under normal circumstances the Tank should be in stable replenish by the T-3 hour hold.  As you may or may not know "stable replenish" is the continuos topping off of the LO2 and LH2 as they boil off.

Mark Kirkman

[ChrisGebhardt]

Justin Wheat - 9/9/2007  8:23 PM

Is the launch time still going to be the same or is it going to be moved forward if this plan is taken into effect?

The launch time will still be the same. It's only a 10minute launch window because of rendezvous capabilities with the ISS so the launch time can't change.

EDIT: Sorry.... missed the previous post answering this question.

[nathan.moeller]

mkirk - 9/9/2007  7:36 PM

nathan.moeller - 9/9/2007  6:50 PM

TJL - 9/9/2007  5:53 PM

This may be a silly question but, what is the difference between reducing the 3 hour hold to 2 hours and 30 minutes or just begin the tanking process 1/2 hour later in the count?

I could be wrong, but I believe the tanking process takes place in the T-3 hour hold.  Someone correct me if that's incorrect.

Under normal circumstances the Tank should be in stable replenish by the T-3 hour hold.  As you may or may not know "stable replenish" is the continuos topping off of the LO2 and LH2 as they boil off.

Mark Kirkman

Thanks Mark.  I know what stable replenish is but I didn't know the timelines.

[nathan.moeller]

Justin Wheat - 9/9/2007  7:23 PM

Is the launch time still going to be the same or is it going to be moved forward if this plan is taken into effect?

No change to T-0.  They'll start the count a half-hour later than they have for past launches.

[Seattle Dave]

That's a very good article, especially on explaining the tank, ice and foam relation.

[George CA]

Can more ice form at more humid times of year?

[STS Tony]

Good move by Mike!

[mkirk]

George CA - 10/9/2007  5:25 PM

Can more ice form at more humid times of year?

Yes.

There are other factor that influence the ice/frost build up as well such as winds (direction & magnitude).

Mark Kirkman

[DaveS]

mkirk - 10/9/2007  2:33 AM

Justin Wheat - 9/9/2007  7:23 PM

Is the launch time still going to be the same or is it going to be moved forward if this plan is taken into effect?

No this will not effect (affect ?) the T-0 time.

Mark Kirkman

It's affect.