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Author
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Topic: What does the "T" in T-minus mean?
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flight_plan
Member Posts: 58
From: Lincs
Registered: Apr 2009
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posted 07-31-2009 01:44 PM
  
Have just been out for a sit in the park and a read of Buzz Aldrin's latest book. Trouble is I was surprised when the wife took it first. She is not normally interested in space stuff but surprised me even more when she asked:"When doing the countdown and they say T minus 10 minutes, what does the T mean?" I had no answer but am sure I know deep inside my head but need refreshing. Any takers? |
Mr Meek
Member Posts: 353
From: Chattanooga, TN
Registered: Dec 2007
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posted 07-31-2009 01:54 PM
I've always understood it as "Time." However, that's my armchair understanding. It's possible that it could stand for something much more esoteric. |
ColinBurgess
Member Posts: 2094
From: Sydney, Australia
Registered: Sep 2003
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posted 07-31-2009 04:51 PM
I always thought it was short for Takeoff, but I'm happy to be proven wrong. |
David Stephenson
Member Posts: 294
From: England
Registered: Mar 2003
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posted 07-31-2009 05:26 PM
I would be happy to know also, that's the sort of question I dread been asked by a group of school children. |
mikej
Member Posts: 483
From: Germantown, WI USA
Registered: Jan 2004
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posted 07-31-2009 06:26 PM
I have always assumed that it means "takeoff," but according to Shuttle Launch Director Mike Leinbach, it stands for "test": Abigail from Pembroke Pines: I've heard that during a launch countdown the "T" in T minus does not stand for "Time." If so, what does the "T" really mean?You hear us talk in the Launch Control Center about T-9 minutes, T-20 minutes, etcetera. And so the assumption is that T stands for time. I joined the space program about 20 years ago and I asked this question of my elders in the program when I did join, and it turns out that T stands for test. Because it's not always related to time. And so, in the early days of the space program, back in the Mercury and Gemini days and, indeed, Apollo, T stood for test. Because again, not all tests are based on time. It could be the start of a particular test in our Orbiter Processing Facility that is independent of the time of day. And so, the T actually stands for test. Good question. It took me awhile to figure that out myself, but it's a good question. |
Rizz
Member Posts: 1208
From: Upcountry, Maui, Hawaii
Registered: Mar 2002
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posted 07-31-2009 11:18 PM
And TALO stands for Time After Lift Off. |
Sy Liebergot
Member Posts: 502
From: Pearland, Texas USA
Registered: May 2003
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posted 08-01-2009 12:32 PM
Time. |
AstroAutos
Member Posts: 803
From: Co. Monaghan, Republic of Ireland
Registered: Mar 2009
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posted 08-01-2009 12:48 PM
We can't argue with Sy — if he says it's time, then it's time because he's been there...Case closed! |
flight_plan
Member Posts: 58
From: Lincs
Registered: Apr 2009
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posted 08-01-2009 04:19 PM
Well my flabber is ghasted. I am so glad it was not an easy one to answer. As the wifey is sitting nearby I have just read all these replies to her and she is a tad smug at finding a question that stumped some of us.As she is now converted to Space history, I have just explained who Sy is as well! Thank you all. |
David Bryant
Member Posts: 986
From: Norfolk UK
Registered: Feb 2005
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posted 08-02-2009 12:53 AM
In the blue corner: EECOM Sy LiebergotIn the red corner: Flight Director Mike Leinbach They can't both be right! |
Rizz
Member Posts: 1208
From: Upcountry, Maui, Hawaii
Registered: Mar 2002
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posted 08-02-2009 01:39 AM
They're not, Sy wins.T-X minutes and 'counting' certainly does relate to 'time'. Most launches are not tests. |
flight_plan
Member Posts: 58
From: Lincs
Registered: Apr 2009
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posted 08-02-2009 01:45 AM
Do we have a problem Houston?As Sy was a member of the pioneers, using the "T" word long before the shuttle guys, I will go with him. We could always ask Jack King. Is he a member on here? |
Robert Pearlman
Editor Posts: 46239
From: Houston, TX
Registered: Nov 1999
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posted 08-02-2009 09:21 AM
The person that manages the countdown (among other preparations) for any launch is called the "Test Director." S/he in turn, then reports to the Launch Director. All launches are tests, but not all tests are launches. Colloquially, I think "T" became known as time, even amongst the mission control ranks, but if you think about it, it really is not a measure of time. During a shuttle countdown, the clock begins at T-43 hours (and counting). If 'T' was strictly "Time" then one should expect the shuttle to launch 43 hours later, but it does not. The actual length of the countdown is longer than 43 hours as a result of seven built-in holds. |
lm5eagle
Member Posts: 429
From:
Registered: Jul 2007
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posted 08-02-2009 10:18 AM
Time to edit Wikipedia. wherein the question is posed: Was T definitely Time or might it have been Takeoff, Terminus, Termination, Triumph, Teatime, or some foreign word or esoteric term? |
Sy Liebergot
Member Posts: 502
From: Pearland, Texas USA
Registered: May 2003
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posted 08-02-2009 10:41 AM
Again, it's Time (to go). |
Lunar Module 5
Member Posts: 370
From: Wales, UK
Registered: Dec 2004
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posted 08-02-2009 11:09 AM
I remember hearing Hugh Harris on the PAO for one of the early shuttle flights. He said "...we will pick up the count at the Time minus, T minus 9 minute point...."So for me "T" is time.... always will be! |
Rick Boos
Member Posts: 851
From: Celina, Ohio
Registered: Feb 2000
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posted 08-02-2009 07:31 PM
I agree "T" is for time, but does anyone recall X-minus? I've read books and saw movies where they say X minus, but what I thought was interesting, I once owned Guenter Wendt's MR-4 whiteroom notebook (black in color) and on the cover he wrote "X-4 days" in yellow crayon. Just a side note. |
Rizz
Member Posts: 1208
From: Upcountry, Maui, Hawaii
Registered: Mar 2002
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posted 08-02-2009 10:40 PM
quote:
Originally posted by Robert Pearlman:
All launches are tests.
Really? I don't think so. They've worked the bugs out for the most part.When astronauts and payloads are being prepared for launch, they are not being "tested," are they? Granted, accidents do occur, but I'd have to respectfully disagree with your statement above. When you start up your car in the morning, is that considered a test also. Its sort of a given that it will "go." |
Jim Behling
Member Posts: 1637
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 05-09-2021 06:06 AM
quote:
Originally posted by Rizz:
When astronauts and payloads are being prepared for launch, they are not being "tested," are they?
Yes, they are. |
SkyMan1958
Member Posts: 1043
From: CA.
Registered: Jan 2011
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posted 05-09-2021 12:30 PM
I'd go with T - Time. Time is after all variable, it does not mean a specific hour of launch. T -30:00 is still 30 minutes from launch with the scheduled holds in it.Let's not forget, to a lot of these people WW II was not ancient history, to many it was a conflict they had fought/participated in. When an Allied invasion was scheduled in WW II it was on D - Day at H - Hour. It was only because June 6, 1944 became so synonymous with D- Day that in some of, but not all, of the later Allied invasions they used another letter besides D to represent the day of invasion. |
Buel
Member Posts: 764
From: UK
Registered: Mar 2012
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posted 05-10-2021 05:11 PM
Dutch von Ehrenfried has been on; Yes, it is Time.In the early days, I would have to call (radio) the tracking stations and give them a "Time Hack" in order to synch their clocks to the control center clocks which were synced to WWV (google that). |
Robert Pearlman
Editor Posts: 46239
From: Houston, TX
Registered: Nov 1999
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posted 05-10-2021 05:33 PM
Given that we have former flight controllers and launch directors giving different definitions (either Time or Test) and given that NASA's website defines it as either "Test" or "Time" depending on where you look, I would suggest that both "Time" and "Test" are correct.I believe the initial use was "Test," given that it was the test conductor (or director) who oversaw the countdown, but it was later interpreted as "Time" as mission control evolved. That said, "test" has not been retired. NASA websites describing the countdowns for Space Launch System hot fires define "T" as "Test." |
GACspaceguy
Member Posts: 2705
From: Guyton, GA
Registered: Jan 2006
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posted 05-10-2021 07:19 PM
This reminds me of the VAB. Originally the Vertical Assembly Building for the Saturn V being stacked vertically. Then Vehicle Assembly Building once the Shuttle was assembled in there. I remember being on a tour with Fred Gregory as the guest astronaut. You would think he would call it a Vehicle Assembly Building as a shuttle astronaut but he called it Vertical Assembly Building during the tour (I believe as he grew up in that era as well). |
Jim Behling
Member Posts: 1637
From: Cape Canaveral, FL
Registered: Mar 2010
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posted 05-10-2021 09:03 PM
It had nothing to do with the shuttle. The name was changed from Vertical to Vehicle in February 1965. Long before Gregory dealt with NASA. |
GACspaceguy
Member Posts: 2705
From: Guyton, GA
Registered: Jan 2006
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posted 05-11-2021 04:54 AM
Thanks for the info. I appear to have posted a VAB legend rather than fact.  |
cspg
Member Posts: 6253
From: Geneva, Switzerland
Registered: May 2006
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posted 05-11-2021 09:55 AM
T for Too-late (to get out)  |
Buel
Member Posts: 764
From: UK
Registered: Mar 2012
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posted 05-12-2021 04:31 PM
Apollo Simsup Dick Koos says: Don't think it's time. But maybe time to launch or time to ignition most likely. I'll go with time to ignition. Trying to think what we used for countdown to inflight burns. I think ignition. |
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