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  Apollo 13 pad fire: Security cars vs LOX vapor

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Author Topic:   Apollo 13 pad fire: Security cars vs LOX vapor
Robert Pearlman

Posts: 43576
From: Houston, TX
Registered: Nov 1999

posted 09-19-2015 02:53 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
JL Pickering unearthed these NASA photos showing a March 25, 1970 fire at Pad 39A that engulfed three security cars prior to the launch of Apollo 13.
Three security vehicles, severely damaged by fire, are removed from the perimeter gate at Pad A Launch Complex 39. The three vehicles caught fire when they drove through a liquid oxygen vapor concentration on the pad perimeter while clearing the pad area of personnel during the Apollo 13 Countdown Demonstration Test that morning.

The drivers of the three vehicles abandoned their cars when the incidents occurred near a pad perimeter gate about 1000 feet from the Saturn V space vehicle. There were no injuries. Damage was confined to the three vehicles.

(Color photographs from the same incident appear in JL's and John Bisney's book, Moonshots and Snapshots of Project Apollo.)


Posts: 2458
From: U.K.
Registered: Jul 2009

posted 09-20-2015 02:17 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
The LOX used to fuel the Saturn V was stored in a 800,000 gallon insulated tank and transferred to the umbilical tower across a gap by an uninsulated pipe. Before the LOX actually used to fill the tanks of the rocket could be loaded, a long chill down process of this pipe, lines and launch vehicle had to be done using about 25,000 gallons of LOX. This, once it had done its job was allowed to drain into a ditch in a nearby swamp. Usually, it was not a problem as the LOX vapourised, mixed with the air and was blown away in the wind.

However, on the day in question a dead calm, an overcast sky and the prevailing temperature and humidity combined to prevent the LOX dispersing. Instead it just sat in the ditch creating a localised fog of pure oxygen vapour.

The police cars, having completed their sweep of the launch complex usually made their exit through a gate close by the LOX facility. On this day, as they drove to the gate and through the fog, the hot engines and grease in the pure oxygen caught fire.

Nobody knew at the time what was happening, but once the excitement had died down the CDDT continued without further incident.

The police never used that particular exit gate again.

On edit: Just to clarify the chill-down process. The oxygen involved was that used to chill down the LOX transfer pump. This was fed by gravity from the storage tank and allowed to escape through a 3 to 4 inch pipe that ran under the pad perimeter road and into the swamp. It was this oxygen that failed to disperse and which the cars ran into.

After the pump was chilled down they started the pump at low rpm and flowed LOX up the uninsulated transfer line into the S-1C first stage where it was vented off through the S-1C vent valve until the transfer line was chilled down and carrying good quality LOX to the Saturn V stages. They then started to fill the vehicle.

Jim Behling

Posts: 1488
From: Cape Canaveral, FL
Registered: Mar 2010

posted 09-20-2015 07:48 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
Here is the area in question.


Posts: 191
From: Trinity, FL USA
Registered: Jan 2011

posted 09-20-2015 10:59 AM     Click Here to See the Profile for moonguyron   Click Here to Email moonguyron     Edit/Delete Message   Reply w/Quote
This incident and many others are described in a book I recently stumbled upon titled "Countdown to a Moon Launch: Preparing Apollo for It's Historic Journey." As a guy that has read on the subject for years it is rare to run onto something I have not read or heard of before. This book has on almost every page reference to details I was not aware of and is therefore both enjoyable and enlightening.

Andy Anderson

Posts: 87
From: Perth, Australia
Registered: Dec 2009

posted 09-21-2015 12:20 AM     Click Here to See the Profile for Andy Anderson   Click Here to Email Andy Anderson     Edit/Delete Message   Reply w/Quote
Also this and some other NASA O2 incidents up to 1971 dealt with here: Mishaps With Oxygen In NASA Operations (NASA TM X-67953).

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