Space News
space history and artifacts articles

Messages
space history discussion forums

Sightings
worldwide astronaut appearances

Resources
selected space history documents

Websites
related space history websites

  collectSPACE: Messages
  Free Space
  What does the "T" in T-minus mean?

Post New Topic  Post A Reply
profile | register | preferences | faq | search

next newest topic | next oldest topic
Author Topic:   What does the "T" in T-minus mean?
flight_plan
New Member

Posts:
From:
Registered:

posted 07-31-2009 01:44 PM     Click Here to See the Profile for flight_plan   Click Here to Email flight_plan     Edit/Delete Message   Reply w/Quote
Have just been out for a sit in the park and a read of Buzz Aldrin's latest book. Trouble is I was suprised when the wife took it first. She is not normally interested in space stuff but suprised 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: 348
From: Chattanooga, TN
Registered: Dec 2007

posted 07-31-2009 01:54 PM     Click Here to See the Profile for Mr Meek     Edit/Delete Message   Reply w/Quote
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: 1567
From: Sydney, Australia
Registered: Sep 2003

posted 07-31-2009 04:51 PM     Click Here to See the Profile for ColinBurgess   Click Here to Email ColinBurgess     Edit/Delete Message   Reply w/Quote
I always thought it was short for Takeoff, but I'm happy to be proven wrong.

David Stephenson
Member

Posts: 290
From: England
Registered: Mar 2003

posted 07-31-2009 05:26 PM     Click Here to See the Profile for David Stephenson   Click Here to Email David Stephenson     Edit/Delete Message   Reply w/Quote
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: 374
From: Germantown, WI USA
Registered: Jan 2004

posted 07-31-2009 06:26 PM     Click Here to See the Profile for mikej   Click Here to Email mikej     Edit/Delete Message   Reply w/Quote
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

posted 07-31-2009 11:18 PM     Click Here to See the Profile for Rizz     Edit/Delete Message   Reply w/Quote
And TALO stands for Time After Lift Off.

Sy Liebergot
Member

Posts: 458
From: Pearland, Texas USA
Registered: May 2003

posted 08-01-2009 12:32 PM     Click Here to See the Profile for Sy Liebergot   Click Here to Email Sy Liebergot     Edit/Delete Message   Reply w/Quote
Time.

AstroAutos
Member

Posts: 724
From: Monaghan Town, Co. Monaghan, Ireland
Registered: Mar 2009

posted 08-01-2009 12:48 PM     Click Here to See the Profile for AstroAutos   Click Here to Email AstroAutos     Edit/Delete Message   Reply w/Quote
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
New Member

Posts:
From:
Registered:

posted 08-01-2009 04:19 PM     Click Here to See the Profile for flight_plan   Click Here to Email flight_plan     Edit/Delete Message   Reply w/Quote
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: 903
From: Norfolk UK
Registered: Feb 2005

posted 08-02-2009 12:53 AM     Click Here to See the Profile for David Bryant   Click Here to Email David Bryant     Edit/Delete Message   Reply w/Quote
In the blue corner: EECOM Sy Liebergot

In the red corner: Flight Director Mike Leinbach

They can't both be right!

Rizz
Member

Posts: 1208
From: Upcountry, Maui, Hawaii
Registered: Mar 2002

posted 08-02-2009 01:39 AM     Click Here to See the Profile for Rizz     Edit/Delete Message   Reply w/Quote
They're not, Sy wins.

T-X minutes and 'counting' certainly does relate to 'time'.

Most launches are not tests.

flight_plan
New Member

Posts:
From:
Registered:

posted 08-02-2009 01:45 AM     Click Here to See the Profile for flight_plan   Click Here to Email flight_plan     Edit/Delete Message   Reply w/Quote
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 "John" Jack King. Is he a member on here?

Robert Pearlman
Editor

Posts: 27327
From: Houston, TX
Registered: Nov 1999

posted 08-02-2009 09:21 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
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: 391
From:
Registered: Jul 2007

posted 08-02-2009 10:18 AM     Click Here to See the Profile for lm5eagle   Click Here to Email lm5eagle     Edit/Delete Message   Reply w/Quote
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: 458
From: Pearland, Texas USA
Registered: May 2003

posted 08-02-2009 10:41 AM     Click Here to See the Profile for Sy Liebergot   Click Here to Email Sy Liebergot     Edit/Delete Message   Reply w/Quote
Again, it's Time (to go).

Sy

Lunar_module_5
unregistered
posted 08-02-2009 11:09 AM           Edit/Delete Message   Reply w/Quote
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: 828
From: Celina,Ohio U.S.A.
Registered: Feb 2000

posted 08-02-2009 07:31 PM     Click Here to See the Profile for Rick Boos   Click Here to Email Rick Boos     Edit/Delete Message   Reply w/Quote
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

posted 08-02-2009 10:40 PM     Click Here to See the Profile for Rizz     Edit/Delete Message   Reply w/Quote
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'.

Just my opinion.

quote:
Originally posted by Sy Liebergot:
Again, it's Time (to go).
LOL

mdmyer
Member

Posts: 899
From: Humboldt KS USA
Registered: Dec 2003

posted 08-03-2009 08:01 AM     Click Here to See the Profile for mdmyer   Click Here to Email mdmyer     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Sy Liebergot:
Again, it's Time (to go).
How about It's Time (to go) to the Moon (again).

blue_eyes
Member

Posts: 161
From: North Carolina, USA
Registered: Jul 2005

posted 08-03-2009 11:46 AM     Click Here to See the Profile for blue_eyes   Click Here to Email blue_eyes     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Rizz:
When you start up your car in the morning, is that considered a test also.
With my car, definitely yes.

robsouth
Member

Posts: 607
From: West Midlands, UK
Registered: Jun 2005

posted 08-03-2009 03:57 PM     Click Here to See the Profile for robsouth     Edit/Delete Message   Reply w/Quote
I had always assumed it meant takeoff. Takeoff minus 10 seconds and counting... minus 8 seconds... we have a go for main engine start... 3... 2... 1... liftoff, maybe it should have been L-10... 9... 8!!!!!

All times are CT (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | The Source for Space History & Artifacts

Copyright 1999-2012 collectSPACE.com All rights reserved.


Ultimate Bulletin Board 5.47a





advertisement