Author Topic: Mercury, Gemini, and Apollo Range Safety  (Read 2557 times)

Offline Danny Dot

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Mercury, Gemini, and Apollo Range Safety
« on: 06/07/2009 03:34 PM »
Does anyone know how the "old" manned systems handed range safety termination of the flight?  In other words how did the crew get away if the Range Safety Officer decided to end the flight?

Danny Deger
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Offline Jim

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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #1 on: 06/07/2009 03:46 PM »
Does anyone know how the "old" manned systems handed range safety termination of the flight?  In other words how did the crew get away if the Range Safety Officer decided to end the flight?

Danny Deger

The range safety "Arm" command would initiate the escape system.

Offline Danny Dot

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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #2 on: 06/07/2009 04:00 PM »
Does anyone know how the "old" manned systems handed range safety termination of the flight?  In other words how did the crew get away if the Range Safety Officer decided to end the flight?

Danny Deger

The range safety "Arm" command would initiate the escape system.

That's what I thought.  I assumed they were trained to wait a couple of seconds before sending the Execute command.  In Gemini, it must have turned on a light in the cockpit.  I don't think there was an automatic abort.

Danny Deger
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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #3 on: 06/09/2009 03:30 PM »
Does anyone know how the "old" manned systems handed range safety termination of the flight?  In other words how did the crew get away if the Range Safety Officer decided to end the flight?

Danny Deger

The range safety "Arm" command would initiate the escape system.
Is there a picture of this?

Offline Jim

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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #4 on: 06/09/2009 04:09 PM »

Is there a picture of this?

It is just a switch on a console
« Last Edit: 06/09/2009 04:12 PM by Jim »

Offline Art LeBrun

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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #5 on: 06/09/2009 04:24 PM »

Is there a picture of this?

It is just a switch on a console

Does the switch have a "protective/flip up" cover to prevent inadvertent triggering prior to launch?
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Offline WallE

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Re: Mercury, Gemini, and Apollo Range Safety
« Reply #6 on: 05/13/2018 08:50 AM »
Gemini didn't have any means of automatic abort. If a launch vehicle malfunction occurred in flight, two abort lights would be illuminated on the control panel via ground command (either direct command to the spacecraft or if a shutdown signal was sent to the LV), after which the astronauts would then pull the D-rings to activate the ejector seats and bail out.

Mercury and Apollo had flight termination that could be activated either through a manual ground command, the ASIS/EDS system, or via manual activation from a lever in the capsule. Alan Shepard during his Mercury flight found himself unable to use the periscope in the capsule without a pressure gauge on his wrist bumping the abort lever. Although the escape tower was gone and bumping the lever probably wouldn't do anything, he didn't want to do it just in case something unexpected happened, so he decided to not use the periscope.

The Range Safety system also had a three second delay between engine shutdown and activation of the destruct charges (as opposed to the normal one second delay) to give the LES enough time to pull the capsule away. This was routed through the ASIS/EDS system--if the Range Safety destruct command were sent, the ASIS/EDS would allow the engine cutoff command to go through while blocking the destruct signal for three seconds. The resultant decrease in propulsion system performance would be sensed by the ASIS/EDS, which then activated the LES. Once the three second delay was done, the destruct command would be unblocked.

In addition, the ASIS/EDS was blocked from sending a cutoff command for the first 30 seconds of launch so that the vehicle would not come down on or around the pad, during this time, only the Range Safety Officer could send a cutoff command.

On Redstone, the decision was made to operate the abort system open loop on manned flights, meaning that the ASIS did not automatically terminate the flight, but instead merely sent an abort signal that the astronaut or ground controllers could act upon. This was because the Redstone had a rigid body structure with high aerodynamic stability and was less likely to break up or tumble suddenly in the event of a flight malfunction, so the astronaut would have enough time to pull the abort lever in the capsule.

On Atlas, they preferred the closed loop abort for manned flights with flight termination being an automated process because it was more likely to fail in such a way that the astronaut would not have time to react.

The EDS system on Saturn was similar to ASIS but had the additional job of checking for premature stage separation.
« Last Edit: 06/02/2018 08:31 AM by WallE »

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