Established Member
On launching an Apollo, who exactly pressed the launch button?
Where was he located? Were there any physical safeguards?
What exactly happened when the button was pressed?
Have there been any changes in pressing the launch button for the Shuttle and todays' Atlas launches?
Are computerised launches necessarily any safer than the pre-computer era launches of Mercury and Gemini?
Order of Kilopi
If I am not mistaken, the engine start was done by an automatic sequencer. The mission control people up close to the launch site were in a reinforced blockhouse that could take the inferno in case of a disaster on the pad.Originally Posted by wd40
I don't know when this technique originated, as opposed to manually pushing buttons or closing switches to start the engines.
Order of Kilopi
I suspected that myself, but there's one piece that I'm missing myself.
Once the launch controller got the go/nogo confirmations, how was the sequencer started?
Established Member
Good question. I had always envisioned the computers in the firing room deciding they were satified that all the switches were in the right positions inside the spacecraft, that everything that needed to be "turned on" for the rocket to work correctly, and that all of the ground equipment (Fuel and oxidizer supplies, pneumatic lines, etc) was equally configured. When it decided all those conditions were properly met, the computers would ask if the controllers were prepared to proceed at T minus 3 minutes 7 seconds. A simple command may have been punched on a small keypad or keyboard, to answer yes. From that point the ground computers set a timer inside the computers of the launch vehicle, and the vehicle itself was pretty much calling the shots. I don't imagine a single button being pressed. As far as who entered this commit code, I would guess the test conductor. I'm looking to see if I can find a more definative answer, but thats as much as I know.
Established Member
Maybe this will help. It's from the NASA Public Affairs office and is a detailed narrative of the Apollo 12 launch. (My bold for emphasis.)
Excerpted from: http://history.nasa.gov/ap12fj/01lau...arth_orbit.htm
Public Affairs Office - "This is Apollo Saturn Launch Control, T minus 5 minutes and counting. At T minus 5 that swing arm number 9 will now be coming back to its fully retracted position at the pad. Mark the swing arm now moving back from the spacecraft as planned at the 5-minute mark in the count. Just before coming up on the swing arm removal, we went through our final status checks and received a loud and strong go from the Mission Director, Chet Lee, Launch Operations Manager, Paul Donnelly, and Launch Director Walt Kapryan responding to the request from the test supervisor.
The lights now will be coming on the abort panels of Astronaut Pete Conrad. These are his cue lights for the five engines in the first stage. These five lights remain on. When we get proper thrust for lift-off the lights go out informing the spacecraft commander that he has good thrust beneath him. We're coming up now on the 4-minute mark. Pete Conrad reports his lights are on.
Spacecraft Test Conductor Skip Chauvin has said, 'Have a good trip, Pete.' Pete reported back, 'We appreciate everything everyone has done.' Four minutes and counting. Still proceeding at this time.
We'll be coming up on our automatic sequence at 3 minutes and 10 seconds in the countdown. We're going through our final astronauts checks at this time as the countdown continues. During these checks just now the Launch Operations Manager Paul Donnelly said to Pete Conrad, 'The launch team wishes you good luck. May the wind be always behind you.' Pete Conrad said, 'Thank you very much.' Count still continuing.
Final checks of the guidance and navigation system going on now. Pete Conrad reporting back on their status.
We'll be coming up on the automatic sequence in about 10 seconds. From that time on down we are completely automatic leading up to 8.9 - the 8.9 second mark in the count when we get the ignition sequence.
Mark firing command, launch sequence start. We have the firing command. We're on automatic sequence. T minus 3 minutes and counting, T minus 3.
Once the automatic sequence began we've begun pressurizing those big fuel and oxidizer tanks, the overall propellant tanks in the 3 stages of the Saturn V launch vehicle. This will lead us up to 8.9 seconds when the engine ignition sequence begins. The five engines in the first stage will ignite building up 7.6 million pounds thrust total. This should occur at the zero mark in the count. We will get verification through the computer that we have proper start thrust, the hold down arms will release, and we'll be off with Apollo 12."
Established Member
http://quest.arc.nasa.gov/space/chat...vis_chat3.html
"The firing room", says the technician. But no clue to the original who dunnit?
edit: The above post.
From the context of the text, I think the 'person' would be the Launch Operations Manager as he appears to be the person most likely to abort the mission should there be a hitch. Since there is apparently no 'button' to push, the person who can stop the launch qualifies?
Order of Kilopi
They actually have three buttons, and there are three people who press them all simultaneously, just so none is really sure that he/she is the one who actually launched the rocket. They can all go to bed reassured that it was probably one of the other two.
Oops, sorry, wrong context.
As above, so below
Established Member
http://www.space.com/12186-space-shu...s-liftoff.html
It works the other way around: once the Ground Launch Sequencer starts, the vehicle will take off, unless someone (or something) issues a hold or abort command.
Order of Kilopi
I don't know who you are responding to, so I don't know who has it the wrong way around.
If it's Jens, then it was a joke.
If it was the OP, then I think we narrowed it down to "no button".
Where it left off was how and when the automated sequencer starts, and that article doesn't make it clear.
It says "The GLS is typically started at about the T-minus 45 minute mark." and "will assume automatic control of the countdown at the T-minus 9 minute mark."
When I hear T-minus, I think of the countdown clock which does not include the hold time.
So; I can only infer that the GLS starts 54 minutes before launch but doesn't take control until the end of the hold.
I would imagine the entire launch countdown is under some kind of computer control and keeps track of things that are checked off as "ok".
Somewhere, somehow, the GLS has to be triggered. Somewhere down the line, someone starts something. I would imagine it would be when someone says "start the clock".
Established Member
http://en.wikipedia.org/wiki/Space_s....A0minute_hold
This wiki article says that the sequencer is started when the countdown resumes (i.e. end of hold = sequencer start).
My guess is that the software is written so that when the clock counts down to T-9min, the system automatically enters hold state until someone presses the button. Once that happens, it will count down and launch the vehicle at T=0, unless there is an abort condition.
Established Member
One doesn't get a more direct linkage between a firing finger and a rocket than at 20:18 in this clip!
http://www.youtube.com/watch?v=VDmaF...eature=related
Order of Kilopi
WD40 - this, as with so many of your threads I feel this need to say..
Why do you ask?
If nothing else, knowing where you're coming from may help us get to whatever specifics of the answer you're looking for.
Order of Kilopi
These are missles, they have nothing to do with NASA launches.
You could have been clear about the video's subject matter in your post, and how it's related. At least I didn't have to wait for over 20 minutes of a video to load before I figured that out for myself.
Also; There's been a lot of information about the workings of a NASA launch. Don't you have any kind of questions, insights or acknowledgements from that?
Vulcan Administrator
If you click on the timeline at the bottom, it will load from the point where you click, so you don't have to wait for the whole thing to load.
Everything I need to know I learned through Googling.
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