From a draft NASA requirements document:
22.214.171.124 Both the crew and the CVCC [Commercial Vehicle Control Center] shall be capable of initiating the pad and the ascent abort sequence.
From NASA Generic Flight Rules Volume A, Space Shuttle:
A2-58 ABORT LIGHT
B. ABORT REQUEST CUES – TWO CUES ARE REQUIRED FOR THE CREW TO TAKE THE NECESSARY ACTION TO ABORT THE FLIGHT (E.G., PHYSIOLOGICAL CUES, ILLUMINATED ABORT LIGHT, VOICE REPORT OVER A/G, COCKPIT INDICATIONS).
I need to do some homework on Mercury, Gemini, and Apollo abort initiation. Gemini crew members could actuate their ejection seats on their own, but whether both the crew and the ground could initiate an abort is something I don’t really know. Famously, the Soyuz crew members cannot initiate an abort. Both the “April Anomaly” of 1975 and Soyuz T-10-1 pad abort of 1983 (http://www.youtube.com/watch?v=UyFF4cpMVag) crews were unable to initiate abort action and had to rely on the ground control, as is still the case today even with the newest model Soyuz.
The Shuttle on the other hand . . . well, here is a mostly true Flight Director story.
In the “old” mission control center at JSC the Flight Director console is preserved much as it was during Apollo and also as it was when I was first training to be a Shuttle Ascent Flight Director in the late 1980’s. Among the old fashioned push buttons and lights (and a rotary phone!) is a formidable piece of hardware always referred to in capital letters: the Abort Switch. The face of the Flight Director console has the (black&white) computer monitor screens, the comm panels with all the flashing lights, and the DDD (dedicated display driver) lights which illuminated for various events to keep the Flight Director situationally aware. The surface of the console is a flat desk covered with Plexiglas (all the better to keep coffee spills off the reference papers below. Between these two surfaces, one horizontal, one vertical, is a short, inclined surface with various controls. One of these controls is the Abort Switch. A large handle, maybe 3 inches long, fits into its base snugly by virtue of triangular metal fittings and strong springs. The Abort Switch is a “lever locking” switch, which means it cannot be accidentally bumped. The protocol, after loudly announcing on the Flight Director comm loop to the CAPCOM: “Abort RTLS (or TAL or ATO)” which the CAPCOM would immediately repeat to the crew over all three air to ground circuits, was for the Flight Director to pull the Abort Switch Handle out from the console, moving it up (to send the “A” command), then releasing the handle to let the switch pop back to center neutral (locked position), pull the Abort Switch handle out a second time from the console and move it down (to send the “B” command), and finally let the switch freely pop back to the center neutral/locked position.
Why all the rigmarole?
The hardware Abort Switch had a nasty habit of sticking on and flooding the command buffer with “Abort A” or “Abort B” commands unless the switch was allowed to pop freely back to the neutral position. If the Abort Switch got stuck in this continuous command mode, no other commands could be sent to the shuttle and the Ground Control officer’s back room had to do computer terminal magic work to make it go away – remember, those were the days of main frame computers and ordinary mortals – or even the Flight Director – were not allowed to touch a computer terminal.
Funny thing, all this effort was merely to illuminate a light on the Shuttle Commander’s dashboard. The entire sequence sent a series of “Abort Request Commands” which really did very little. But we paid a lot of attention to the sequence. When properly initiated the Abort Switch first sent three times the single stage “Abort Request A Command” which, once received onboard, was routed from the radio equipment to the General Purpose Computers to a Multiplexer/Demultiplexer to one of the Annunciator Control Assembly electronics to light one bulb of the Commander’s abort light. The second actuation sent the “B” command out three times through the same radio equipment to the GPCs then to a redundant MDM and ACA to light the redundant bulb in the Commander’s abort light. The Shuttle Commander, after having the confirming cue as described in the flight rule above, then moves the rotary abort switch from its “off” position to the desired abort mode (RTLS, TAL, ATO, or AOA) and punches the Abort push button indicator (which the abort commands have illuminated), and then the computer software modes to the desired abort mode and away you go. Whew. Go back and read that slowly. All of that, just to avoid making a mistake. Does it sound overly complex to you?
When we moved to the “new” control center in the mid 90’s, the builders wanted to eliminate the abort switch and just have the Flight Director send the abort commands by mouse click on the computer screen in front of him. The Flight Director office rebelled against this affront to tradition and demanded a dedicated PBI on the console to send the abort command. Probably the only PBI in the “new” control center is the Flight Director’s Abort button. Which doesn’t do anything but light a light in front of the spacecraft commander. But don’t worry; it has complex and convoluted software to control it!
During multitudinous simulations in both the old and new control centers, I have had the opportunity to send the abort command to the crew in the shuttle mission simulator probably a thousand times. The only Flight Director to have a reason to send the abort request command in real flight was Orion Flight, Flight Director #21, Cleon Lacefield, on STS-51-F in 1985. The Center SSME was erroneously shut down early by bad instrumentation resulting in an Abort To Orbit (which is principally a dump of fuel from the Orbital Maneuvering System). STS-51-F made it to orbit, and the mission was accomplished completely successfully albeit at a lower than planned orbital altitude. There is an apocryphal story that Cleon was so busy with the ascent that he neglected to send the Abort Request Command. I don’t know if that is true, I need to ask Cleon. In any event, Orion Flight is the only American Flight Director to declare an ascent abort in history of American manned spaceflight.
All of that is background to my real story for the day.
Every countdown, the Abort Command System is checked about 10 hours pre-launch. One of the non-ascent Flight Directors is on console in Houston with a team to babysit the vehicle (really under the control of the Launch Director), the network, and the Mission Control Center until the Ascent team shows up about four hours prior to launch. Now, the orbit certified Flight Directors do not have the training that the Ascent Flight Directors have, and there is considerable uncertainty about this test. The FD is directed to actually send the Abort Request commands (both A and B) to the vehicle and one of the Caped Crusaders sitting in the Commander’s seat verifies the light comes on.
So when Alpha Flight (FD #23, you have to look it up) was doing prelaunch for the very first time, the NTD called from KSC and said: “Houston Flight, step 16-xxx, send Abort Command” he wouldn’t do it! As he later said, “I thought it might blow up the vehicle, and I didn’t want to be responsible for that!”
I remember this incident well, because as the rookie trainee Flight Director I got the assignment to write up the Handbook procedure on the pre-launch abort light test.
But if you hadn’t read this, wouldn’t you agree with Alpha Flight? Who would believe that the Shuttle Flight Director sending the abort command merely lights a light in the cockpit for the Commander to see?!
Oh, next you will want to know how to turn the light off . . . .