posted 02-06-2011 07:08 PM            

My first question is when a shuttle launches, I'm assuming that the engine firing is handled by computers and not someone "pressing a button" in the firing room. If this is so, when did this begin? On a recent viewing of "The Right Stuff" a technician is seen pressing a button in the firing room (hence its name) for Alan Shepard's Mercury launch.

Also while watching a Soyuz launch, a launch key was mentioned. So how exactly do they launch (a bit off topic)?

My next question regards the external tank piping connections to the orbiter. After the external tank is jettisoned, what happens to the exposed intake areas on the bottom of the shuttle? I have never seen open doors on the bottom of the orbiter which would close. Sliding doors don't make sense to me as I would think the tiles could be damaged, and the "seal" between the "door" and bottom wouldn't be proper atmospheric reentry.

posted 02-06-2011 08:20 PM               

As such, there is no launch button in the LCC.*

From T-8 seconds, the final ignition sequence and liftoff of the Saturn V was computer controlled (T-3 seconds for the Saturn IB).

Gemini-Titan's first stage engine ignition signal was given from the blockhouse.

The Soyuz countdown includes a key being inserted in the launch bunker after the T-5 minute mark, a carryover from the Vostok launch countdown. Control is turned over to an automatic sequencer at one minute to launch.

As for the external tank umbilicals to the orbiter, doors close to cover the attach points after ET jettison.

An electromechanical actuation system on each umbilical door closes the left and right umbilical cavities after the external tank is jettisoned and the umbilical plates retracted inside the orbiter's aft fuselage. Each umbilical door is approximately 50 inches square.