-
#1640
by
ChrisGebhardt
on 25 Feb, 2011 15:26
-
I was going by what it said in "Some Trust in Chariots" book about Challenger which claims there were recycles on both days,
January 6 was T-31 seconds - T-20 minutes - T-9 minutes - SCRUB.
January 7 was T-9 minutes - T-20 minutes - T-9 minutes - SCRUB.
This is according to the book.
One final question also: Was any advantage gained on STS-133 by counting down to T-5 when they did rather than holding at T-9 minutes and picking up the count at the last possible moment and the scrubbing if the issue wasn't resolved when the clock reached T-5 minutes?
I will have to go look at the January 7th launch info.
On the STS-133 question: Yes, gained a tremendous advantage. Not only did we launch (
) but by counting to T-5mins and holding, we gave the Range 4 extra minutes to work the issue.
Think of it this way, if we had held at T-9mins, we would only have been able to hold for 3mins. That means the Range would have had to have cleared their issue by 16:44:27 EST in order for us to pick up the count and launch within the window which closed at 16:53:27 EST. They did not do this. If we had held at T-9mins, we would have scrubbed for the day.
By counting to T-5mins and holding (which began at 16:45:27 EST), the Range had those 4-minutes from T-9mins to T-5mins) plus an additional 3-mins of time once we started holding. Thus, by counting to T-5mins, the Range effectively had until 16:48:27 EST to work and clear the issue. They cleared the issue (manual switch throw from "hold" to "proceed") at 16:48:10 EST and the count resumed at 16:48:24 EST.
-
#1641
by
Zoe
on 25 Feb, 2011 15:30
-
I was resuming the count at T-9 minutes 1 second before the end of the launch window even if the range was still no-go. The clock would then count down to T-5 minutes and if they didn't have a go by that time then the launch would be scrubbed. You wouldn't lose any time if you did it that way.
-
#1642
by
ChrisGebhardt
on 25 Feb, 2011 15:33
-
I was resuming the count at T-9 minutes 1 second before the end of the launch window even if the range was still no-go. The clock would then count down to T-5 minutes and if they didn't have a go by that time then the launch would be scrubbed. You wouldn't lose any time if you did it that way.
Yes, you would. You would lose 4-minutes of troubleshooting time. Re-read my post directly about this one
.
-
#1643
by
Zoe
on 25 Feb, 2011 15:44
-
The launch window clsoed at 16:53:27 EST. T-5 is as low as you would want to go in the count as going beyond there would invovle starting the APUs and if you are not going to launch you don't want to start them. If you resumed at 16:44:27. What I'm saying is that you could have resumed the count at this time regardless of the range. The range would still have had the extra 3 minutes of the T-9 hold plus the time to count down from T-9 to T-5 to troubleshoot the issue before a scrub would have to be decalred. The clock would have reached T-5 minutes at 16:48:27, the same point at which a scrub would have been declared by the way you did it.
-
#1644
by
ChrisGebhardt
on 25 Feb, 2011 15:48
-
The launch window clsoed at 16:53:27 EST. T-5 is as low as you would want to go in the count as going beyond there would invovle starting the APUs and if you are not going to launch you don't want to start them. If you resumed at 16:44:27. What I'm saying is that you could have resumed the count at this time regardless of the range. The range would still have had the extra 3 minutes of the T-9 hold plus the time to count down from T-9 to T-5 to troubleshoot the issue before a scrub would have to be decalred. The clock would have reached T-5 minutes at 16:48:27, the same point at which a scrub would have been declared by the way you did it.
No. If you pick up the count at T-9mins with no option to hold at T-5mins because a department is "no go" then you are in violation of the Launch Commit Criteria. They could no have done this. The only reason we were allowed to proceed past T-9mins, was because we had hold time at T-5mins.
-
#1645
by
Zoe
on 25 Feb, 2011 15:55
-
I wasn't saying not have a hold at T-5. Keep the hold in there to stop the clock at T-5 minutes. The clock would reach T-5 minutes exactly 5 minutes before the end of the window and would then hold so a scrub could be declared. The count would have entered the T-5 hold at the exact same time that STS-133 would have been scrubbed even f you had already counted down to T-5 and waited there.
-
#1646
by
ChrisGebhardt
on 25 Feb, 2011 15:59
-
I wasn't saying not have a hold at T-5. Keep the hold in there to stop the clock at T-5 minutes. The clock would reach T-5 minutes exactly 5 minutes before the end of the window and would then hold so a scrub could be declared. The count would have entered the T-5 hold at the exact same time that STS-133 would have been scrubbed even f you had already counted down to T-5 and waited there.
Again, it doesn't work like that. There would be no option to "hold" at T-5mins if you were targeting the end of the window. Thus, all systems would have had to have been "GO" to resume the count at T-9mins for an exact "end of window" launch. This was not and would not have been the case yesterday.
-
#1647
by
Jim
on 25 Feb, 2011 16:00
-
I wasn't saying not have a hold at T-5. Keep the hold in there to stop the clock at T-5 minutes. The clock would reach T-5 minutes exactly 5 minutes before the end of the window and would then hold so a scrub could be declared. The count would have entered the T-5 hold at the exact same time that STS-133 would have been scrubbed even f you had already counted down to T-5 and waited there.
There is no T-5 hold. T-5 is a hold point. There are other hold points like LO2 hood retract, Auto sequencer start, etc. The point is that there are no holds after T-9 until there is a problem
-
#1648
by
Zoe
on 25 Feb, 2011 16:05
-
So you are not allowed to specify a hold point then if are targetting the end if window. So in the event that you were to target the end of the window and you resumed the count at T-9 minutes and you needed to stop the clock would you call a hold, inform the crew you are going to scrub and then call GLS cutoff or would you just directly call GLS cutoff regardless of how far down the count you were?
Thanks for the replies everyone, I have a better understanding now.
-
#1649
by
ChrisGebhardt
on 25 Feb, 2011 16:09
-
So you are not allowed to specify a hold point then if are targetting the end if window. So in the event that you were to target the end of the window and you resumed the count at T-9 minutes and you needed to stop the clock would you call a hold, inform the crew you are going to scrub and then call GLS cutoff or would you just directly call GLS cutoff regardless of how far down the count you were?
Thanks for the replies everyone, I have a better understanding now.
You would be in an automatic scrub scenario. I believe you would continue to count to the next GLS milestone and then issue a GLS cutoff.
-
#1650
by
Zoe
on 25 Feb, 2011 16:12
-
I've actually never heard a HOLD! HOLD! HOLD! call on a shuttle launch but then manual hold requets after T-9 minutes do seem quite rare.
-
#1651
by
Jim
on 25 Feb, 2011 16:16
-
I've actually never heard a HOLD! HOLD! HOLD! call on a shuttle launch but then manual hold requets after T-9 minutes do seem quite rare.
No, the shuttle syntax is "GLS give cut off"
-
#1652
by
Zoe
on 25 Feb, 2011 16:17
-
I thought that was only after T-31 seconds. If a hold is called before that time it doesn't automatically mean a cutoff.
-
#1653
by
Jim
on 25 Feb, 2011 16:20
-
I thought that was only after T-31 seconds. If a hold is called before that time it doesn't automatically mean a cutoff.
Before that it is "GLS, Hold for XXXX"
Hold, Hold, Hold is only used for ELV's
-
#1654
by
Zoe
on 25 Feb, 2011 16:40
-
Anyone know why the T-20 briefing was done during the T-9 hold for STS-133?
-
#1655
by
The-Hammer
on 25 Feb, 2011 17:29
-
In one of the ascent reports on L2, it mentions a 2-second "RCS window protect firing" occurring about 10 seconds before the OMS assist burn. I haven't seen this term before, and a quick search doesn't show any other mentions of this burn.
Can someone provide some insight into this burn?
-
#1656
by
Jim
on 25 Feb, 2011 17:37
-
In one of the ascent reports on L2, it mentions a 2-second "RCS window protect firing" occurring about 10 seconds before the OMS assist burn. I haven't seen this term before, and a quick search doesn't show any other mentions of this burn.
Can someone provide some insight into this burn?
http://forum.nasaspaceflight.com/index.php?topic=2030.msg33768#msg33768
-
#1657
by
pummuf
on 25 Feb, 2011 18:52
-
What's involved with the SSME servicing between flights?
-
#1658
by
The-Hammer
on 25 Feb, 2011 20:45
-
D'oh.
I searched for both "RCS window protect firing" and then "window protect firing".
I was one dropped word away...
-
#1659
by
sivodave
on 25 Feb, 2011 21:37
-
There a RCS window protecting firing in the moment in which the SRM separate from the ET in order to avoid that the exaust coming off the SRM separation thrusters could damage the forward windows. The forward RCS jets are fired so that they don't allow this exaust to hit the windows. In this way the maintenance of the forward windows is eased.
there is an explanation of this firing in the RCS Workbook on L2.
hope this help
) but by counting to T-5mins and holding, we gave the Range 4 extra minutes to work the issue.