Author Topic: Emergency ejection of CM during the launch phase.  (Read 15422 times)

Offline BILLR

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Emergency ejection of CM during the launch phase.
« on: October 13, 2012, 02:11:17 AM »
How would this process play out?(on Apollo). I know the  commander had physical control in case of this event. How would this work in regards to procedures for the flight crew? Was there any point of flight in which the system was automatic or was it always at the commanders discertion.

Offline raven

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Re: Emergency ejection of CM during the launch phase.
« Reply #1 on: October 13, 2012, 03:21:13 AM »
Unless you have some ulterior motive behind these questions, this would probably do better in the sub forum below this one.
Welcome to the Apollhoax forum, by the way. :)

Offline Glom

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Re: Re: Emergency ejection of CM during the launch phase.
« Reply #2 on: October 13, 2012, 04:27:48 AM »
How would this process play out?(on Apollo). I know the  commander had physical control in case of this event. How would this work in regards to procedures for the flight crew? Was there any point of flight in which the system was automatic or was it always at the commanders discertion.

You refer to the Mode I abort? The launch escape tower would lift the CM away from the space vehicle and it would then parachute into the sea. Not really sure how much flying there was to be done.

Offline Jason Thompson

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Re: Emergency ejection of CM during the launch phase.
« Reply #3 on: October 13, 2012, 07:30:29 AM »
This is probably better off in the 'reality' section.

How would this process play out?(on Apollo).

Once the abort is initiated the escape rocket fires, and small canards emerge from the top of the escape tower to provide some measure of stability and control. The Cm is separated and carried away. once the tower rocket motor burns out the tower and BPC are discarded, the parachutes on the Cm open and the CM drifts slowly back down to land in the sea. Recovery forces then pick up the crew.

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I know the  commander had physical control in case of this event. How would this work in regards to procedures for the flight crew?

They just had to sit tight. There was little to do except pull the abort handle to initiate the abort, then sit back and ride it out.

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Was there any point of flight in which the system was automatic or was it always at the commanders discertion.

The abort system had pressure sensors inside the various stages of the rocket, the idea being that a recorded sudden drop in pressure would indicate that the launch vehicle was breaking up. This would trigger an automatic abort, since the breakup would proceed too rapidly and catastrophically for the crew to react to in time to execute the move. The first test of the abort system was an inadvertent test of the automatic sequencer, as the little Joe II rocket started an uncontrolled roll and broke up. The abort motor triggered successfully. It wasn't what they were trying to test, but it did at least provide usueful data.
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Offline BILLR

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Re: Emergency ejection of CM during the launch phase.
« Reply #4 on: October 13, 2012, 08:30:00 AM »
Thanks guys. I did not notice the reality section. I have alot of questions on mission details. Reading thru flightdeck voice transcripts kind of does that to you.

Offline Kiwi

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Re: Emergency ejection of CM during the launch phase.
« Reply #5 on: October 13, 2012, 10:21:30 AM »
Something I'd like to know about a similar thing that led up to Apollo, is:

Just how amazing (or otherwise) was Wally Schirra's non-pulling of the "chicken ring" during the first attempted launch of Gemini 6?
« Last Edit: October 13, 2012, 10:24:30 AM by Kiwi »
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Offline Echnaton

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Re: Emergency ejection of CM during the launch phase.
« Reply #6 on: October 13, 2012, 05:45:41 PM »
Its hard to say what is going through a guys mind at a time like that.  Don't screw up, has to be one of the top things.  After the loss of Liberty Bell 7 every astronaut must have been especially wary of the consequences of mistakes or even non-mistakes like happened to Grissom.   It is one thing when you are a test pilot in the desert, its another when you are a public figure on live TV.  But those guys had nerves of steel to put all the pressures away and keep a clear head when their missions and lives were on the line.
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Offline Count Zero

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Re: Emergency ejection of CM during the launch phase.
« Reply #7 on: October 14, 2012, 09:04:48 PM »
Something I'd like to know about a similar thing that led up to Apollo, is:

Just how amazing (or otherwise) was Wally Schirra's non-pulling of the "chicken ring" during the first attempted launch of Gemini 6?


See?  Who says you'll never get a medal if you just sit there doing nothing?

I also admire Pete Conrad for "doing nothing" on Apollo 12, when every alarm & light in the cockpit lit-up when they were struck by lightning.
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Offline ka9q

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Re: Emergency ejection of CM during the launch phase.
« Reply #8 on: October 15, 2012, 02:05:43 AM »
During Apollo first stage flight on the Saturn IB and V, emergencies could happen far too quickly for a human to react in time to survive, so an automatic "emergency detection system" (EDS) operated during this time. Its primary sensor was the "Q-ball" at the tip of the launch escape tower; it monitored angle of attack and rotation rates in roll, pitch and yaw, automatically initiating an abort if any exceeded preset limits. The Commander could also initiate an abort manually but it's hard to think of a failure that would require him to do so very rapidly if the EDS were working properly.

The classic example of a failure that woud cause the angle of attack to suddenly increase would be an "engine hardover", a failure of an engine gimbal (or of its hydraulic actuator) that forced it all the way over to one side.

Anything that caused the angle of attack to increase suddenly was especially critical because, near the max-Q (maximum aerodynamic pressure) phase at about T+90 sec an excessive angle of attack could quickly rip the entire stack apart. An uncontrolled angle of attack -- not the disintegration of the external tank -- destroyed Challenger in 1986. I can cite numerous examples of angle-of-attack breakups in unmanned rocket launches, particularly the Delta failure that occurred a few months after Challenger.

Angle of attack has to be kept essentially at zero until the stack is outside the sensible atmosphere. A "gravity turn" maneuver is generally used to allow a gradual pitchover while keeping angle of attack at zero. Only above the atmosphere is "closed loop guidance" usually enabled, allowing the stack to take whatever angle is required to meet its target orbit with the least amount of propellant.

The Apollo Q-ball was jettisoned along with the escape tower shortly after staging. The Commander would inhibit the EDS manually just before staging, as depicted in the movie Apollo 13. Beyond that point the stack was outside the atmosphere so any failure, even one that caused the stack to turn around, would not rip it apart from aerodynamic forces and the automatic EDS abort capability was no longer needed. If a manual abort were needed, the launcher engines would be commanded to shut down and the Service Propulsion System engine would push the CSM away from the failed launcher to a safe distance. Then the CM would separate from the SM and come down as if after a normal entry.

 


Offline Glom

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Re: Emergency ejection of CM during the launch phase.
« Reply #9 on: October 15, 2012, 02:16:08 AM »
"EDS to manual. Inboard! Get ready for a little jolt fellas."

Da da da da da da. Da da da da da da. Da da da da da da. Da daaa!

"That was some little jolt."

Offline smartcooky

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Re: Emergency ejection of CM during the launch phase.
« Reply #10 on: October 15, 2012, 04:06:24 AM »
I have a question.

During an STS launch, the whole vehicle does a "roll" just after liftoff. I think I understand the purpose of that roll; to orient the Orbiter so that it goes into orbit "tail down" and in the required trajectory for whatever orbital inclination is needed for the mission profile.

However, I notice in the transcripts of the Apollo missions, the stack begins a "roll program" about 15 seconds after launch, which becomes a "pitch program" at about 35 seconds; its clearly heard on the audio of the Apollo launches on YT, and faithfully reproduced in the movie Apollo 13 where we hear Tom hanks saying "Roll complete, and we are pitching"

While I understand the need to orient an asymmetrical stack like the STS  (Fuel Tank, SRBs and Orbiter), I don't understand why the Saturn V needs to roll. It is after all a long, round tube with symmetrical main engine placement (one in the centre and four around the outside).

Why does it need to roll? 
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Offline Glom

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Re: Emergency ejection of CM during the launch phase.
« Reply #11 on: October 15, 2012, 04:53:48 AM »
I believe it's so the astronauts are oriented with the right way.

Offline gwiz

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Re: Emergency ejection of CM during the launch phase.
« Reply #12 on: October 15, 2012, 09:44:42 AM »
Once the abort is initiated the escape rocket fires, and small canards emerge from the top of the escape tower to provide some measure of stability and control.
Probably better to say the canards destabilise the stack so that it pitches over to fly heat-shield-first, which is the way you want to be flying when you deploy the parachutes.
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Offline Echnaton

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Re: Emergency ejection of CM during the launch phase.
« Reply #13 on: October 15, 2012, 10:58:34 AM »
Why does it need to roll? 

During launch, the rocket was flown with one axis being referenced to the ground, so, for instance, the pitch maneuver was always performed the same way.    Since each mission could have a different launch direction, each needed to be rolled slightly to get the orientation of the capsule correct to the ground.  One benefit of always having a roll program was that it didn't really matter how much of a roll you made so the orientation on the pad could be in a direction that facilitated access via the white room.
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Offline Peter B

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Re: Emergency ejection of CM during the launch phase.
« Reply #14 on: October 15, 2012, 08:15:14 PM »
During an STS launch, the whole vehicle does a "roll" just after liftoff. I think I understand the purpose of that roll; to orient the Orbiter so that it goes into orbit "tail down" and in the required trajectory for whatever orbital inclination is needed for the mission profile...

While I understand the need to orient an asymmetrical stack like the STS  (Fuel Tank, SRBs and Orbiter), I don't understand why the Saturn V needs to roll. It is after all a long, round tube with symmetrical main engine placement (one in the centre and four around the outside). Why does it need to roll?
My understanding is that the same reasons applied to both spacecraft.

Firstly, it placed the astronauts in a head-down attitude, so that they always had a view of the horizon out the window during launch.

Secondly, it ensured the astronauts' brains weren't starved of blood during acceleration.

However, I'm happy to be corrected by people who actually know this stuff.