Author Topic: Apollo forward heat shield  (Read 3121 times)

Offline bknight

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Apollo forward heat shield
« on: October 30, 2017, 02:18:08 PM »
A question was asked in CosmoQuest yesterday
https://forum.cosmoquest.org/showthread.php?166983-Apollo-disaster-procedures&highlight=apollo

That asked basically what procedures were in place for certain disasters.

slang linked to a NASA Technical site.

https://ntrs.nasa.gov/

 I was browsing yesterday and ran across A15's parachute failure.  In the paper, the forward heat shield might have caused the failure, but that was disproved by TV imagery of the heat shield below the CM when viewed by ship/helicopters.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010152.pdf

That got me to thinking, and failing to resolve my search I'll ask here.

1. It seems like the ejection event of the heat shield was  caused by explosives, but could have been caused by springs.  Which was it?

2.  As he heat shield was propelled upward how did it get out of the way of the drogue chute deployment?  Was it decided by the engineers that it would travel upward and then drift laterally out of the way.  From the description the shield must have fell faster than the capsule.  No problem here if it was out of the way during the drogue deployment.
So what mechanism was used to plan for the shield to be out of the way of the drogue and the mains?
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline Allan F

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Re: Apollo forward heat shield
« Reply #1 on: October 31, 2017, 10:54:37 AM »
Drogue chutes were deployed by pyrotechnics. Small solid rocket engines pulled the drogues out into the airstream.
Well, it is like this: The truth doesn't need insults. Insults are the refuge of a darkened mind, a mind that refuses to open and see. Foul language can't outcompete knowledge. And knowledge is the result of education. Education is the result of the wish to know more, not less.

Offline bknight

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Re: Apollo forward heat shield
« Reply #2 on: November 01, 2017, 08:07:07 AM »
Drogue chutes were deployed by pyrotechnics. Small solid rocket engines pulled the drogues out into the airstream.

Yes the drogue chutes were deployed by mortars, but how was the shield itself accomplished
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline Jason Thompson

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Re: Apollo forward heat shield
« Reply #3 on: November 01, 2017, 08:26:25 AM »
I believe the book excerpt here has the information you seek:

"There's this idea that everyone's opinion is equally valid. My arse! Bloke who was a professor of dentistry for forty years does NOT have a debate with some eejit who removes his teeth with string and a door!"  - Dara O'Briain

Offline Obviousman

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Re: Apollo forward heat shield
« Reply #4 on: November 01, 2017, 04:38:17 PM »
This YouTube video shows the sequence at about 7 mins. Not a lot but it might help a little.



Also, some detail in here:

https://www.ibiblio.org/apollo/ApolloProjectOnline/Documents/SMA2A-03-BLOCK%20II%20Volume%201%2019691015/aoh-v1-2-09-seqsys.pdf

« Last Edit: November 01, 2017, 04:50:50 PM by Obviousman »

Offline Obviousman

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Re: Apollo forward heat shield
« Reply #5 on: November 01, 2017, 04:56:43 PM »
Drogue chutes were deployed by pyrotechnics. Small solid rocket engines pulled the drogues out into the airstream.

Yes the drogue chutes were deployed by mortars, but how was the shield itself accomplished

Piston rods.

"When gas pressure is generated by the pressure cartridges, two pistons will be forced apart and a tension line will be broken. The lower piston will be forced against a stop and the upper piston will be forced out of its cylinder. The piston rod ends are attached to forward heat shield fittings and the apex cover is forced away from the CM"

Also:

"The mortar deployed drag parachute, as the name implies, is used to drag the apex cover out of an area of negative air pressure following the CM and will prevent recontact of the apex cover with the CM"

(From the PDF link above)
« Last Edit: November 01, 2017, 05:05:40 PM by Obviousman »

Offline bknight

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Re: Apollo forward heat shield
« Reply #6 on: November 02, 2017, 08:06:29 AM »
I believe the book excerpt here has the information you seek:

Yes that was the information.  Thanks Jason.
Quote
At 24000 feet (7300 meters), barometric switches close and mortar charges fire to separate the forward heat shield or apex cover, from the rest of the spacecraft.  A small parachute built into the apex cover assists in separating the two and ensures that they will not recontact.
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan

Offline bknight

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Re: Apollo forward heat shield
« Reply #7 on: November 02, 2017, 08:09:33 AM »
This YouTube video shows the sequence at about 7 mins. Not a lot but it might help a little.



Also, some detail in here:

https://www.ibiblio.org/apollo/ApolloProjectOnline/Documents/SMA2A-03-BLOCK%20II%20Volume%201%2019691015/aoh-v1-2-09-seqsys.pdf

My lap won't open the document, but it probably indicates the same information as Jason linked.  Thanks
Truth needs no defense.  Nobody can take those footsteps I made on the surface of the moon away from me.
Eugene Cernan