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Author
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Topic: Launch stresses on Apollo CSM RCS nozzles
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Captain Apollo
Member Posts: 260
From: UK
Registered: Jun 2004
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posted 01-24-2012 02:30 PM
   
Why didn't the Apollo command/service module reaction control system (RCS) nozzles get torn off during liftoff? The quads are exposed on the side of the service module, there is no boost cover and the upper nozzle is even open to the direction of ascent. Why wasn't at least that one torn off? |
moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 01-24-2012 02:35 PM
Simple answer - because they were engineered to withstand the forces applied to them. |
Blackarrow
Member Posts: 3160
From: Belfast, United Kingdom
Registered: Feb 2002
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posted 01-24-2012 05:12 PM
Just about every component on the Saturn-Apollo vehicle was over-engineered to withstand much more than the anticipated stresses of a lunar flight. In close-up pictures of the Apollo capsule I half-expect to see rivets. (I'm joking: no need for an analysis of the relative strengths of welding versus rivetting...) |
moorouge
Member Posts: 2458
From: U.K.
Registered: Jul 2009
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posted 01-25-2012 04:53 AM
Are there any airflow studies of the Saturn stack as it passed through Max-Q? I was wondering if the shape of the CM might have deflected the flow somewhat to reduce the pressure on the quads. |
SpaceAholic
Member Posts: 4494
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 01-25-2012 05:44 AM
Wind tunnel test was performed; in addition during the test flights, sensors were implanted on the nozzles to measure nozzle performance under actual dynamic launch loads. |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
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posted 01-26-2012 10:11 PM
They had plenty of data on it by the time the Saturn Vs flew. The earliest flight testing of dummy RCS quads occurred during the Saturn 1 Block 2 flights in the early 1960s and as I recall, they had one production spec thruster quad on the last Little Joe II LES abort test (done with a Block 1 Apollo spacecraft as opposed to a boilerplate CM) to make sure the flight data matched their test data. It did and it cleared the way for the Saturn 1B and Saturn V flights.A fighter plane can go through mach with big un-aerodynamic looking things strapped to the wings of airplanes (bombs, rockets, other containers). Typically when fully loaded they do not as it wastes fuel. But a launch vehicle is going to keep accelerating as long as it has thrust that exceeds the weight of the rocket. So, if those little protrusions on the outside are designed right, no problem. To me, they provided no more or less air drag than the separation motors on the base of the SRBs of a shuttle stack and those have gone through Max Q just fine without damage. Only thing that ever did rip off on a Saturn V launch to my knowledge was the micrometeoroid shield on Skylab. That broke off primarily because it didn't have a tight seal to the side of the workshop. So an air pocket built up and expanded as the rocket ascended until air drag got under it and tore it off like a roof shingle in a hurricane. That happened mainly because somebody didn't give it the proper testing in the design phase to see if it might be a problem. |
art540
Member Posts: 432
From: Orange, California USA
Registered: Sep 2006
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posted 01-27-2012 12:45 AM
I wonder if the first Atlas-Centaur insulation panel failure could have created some lessons for Skylab 1. Different causes I know... |
Skylon
Member Posts: 277
From:
Registered: Sep 2010
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posted 01-27-2012 05:45 AM
quote:
Originally posted by Jay Chladek:
Only thing that ever did rip off on a Saturn V launch to my knowledge was the micrometeoroid shield on Skylab.
I believe an adapter panel (or part of one) between the SIV-B and Apollo CSM came off on Apollo 6 due to the heavy pogo. |
Jay Chladek
Member Posts: 2272
From: Bellevue, NE, USA
Registered: Aug 2007
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posted 01-28-2012 07:52 PM
quote:
Originally posted by Skylon:
I believe an adapter panel (or part of one) between the SIV-B and Apollo CSM came off on Apollo 6 due to the heavy pogo.
True, but I didn't think of it because Apollo 6 had several anomolies with the pogo being but one of them making it a rather off nominal mission. Skylab's launch was perfectly normal otherwise until the shield came off and even after that happened the rocket continued to work as advertised. But yes, there was at least one SLA panel that came off on Apollo 6. |
moonguyron
Member Posts: 191
From: Trinity, FL USA
Registered: Jan 2011
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posted 01-31-2012 09:05 PM
Only slightly unrelated; Al Worden writes in his book "Falling to Earth" that he had a chance to see the CSM thrusters close up during his EVA on their way home from the moon. He writes: ...the thrusters on the side of the service module had bubbled and burned the module surface when they fired. We'd never been able to see this before, and it wasn't good. It hadn't damaged anything vital that I could see, but I guessed the engineers would want this problem fixed before the next mission. |
SpaceAholic
Member Posts: 4494
From: Sierra Vista, Arizona
Registered: Nov 1999
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posted 01-31-2012 09:53 PM
Think he's citing delamination of the covers vice the nozzles (R-4D nozzles did not have an external coating).  |
rolly
New Member Posts:
From:
Registered:
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posted 02-01-2012 07:28 AM
The document Apollo Experience Report - Command and Service Module Reaction Control Systems (PDF) gives a very good insight into the engineering tests carried out on both the CM and SM RCS systems. It shows the extent of the testing that was done to ensure these systems would operate in both the ascent to orbit and space. |
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