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  Mercury - Gemini - Apollo
  Apollo 13: LC-39 Pad A CDT Fire 25 Mar 1970

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Author Topic:   Apollo 13: LC-39 Pad A CDT Fire 25 Mar 1970
YankeeClipper
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Posts: 285
From: Dublin, Ireland
Registered: Mar 2011

posted 04-19-2014 10:31 AM     Click Here to See the Profile for YankeeClipper   Click Here to Email YankeeClipper     Edit/Delete Message   Reply w/Quote
It is said that many aerospace accidents begin on the ground. Even Apollo 13 LMP Fred Haise wasn't aware of this Countdown Demonstration Test fire on 25 March 1970, when I showed him a photo of the aftermath last year.
Apollo 13 Launch Operations

After four days of hypergolic load tests in mid-March, the launch team began the countdown demonstration test on the 18th.

A strange accident punctuated the last day of the test. Early on 25 March, Graydon Corn's propellants crew started the chill-down of the LOX pumping system. The operation required a 760-liter-per-minute flow to the replenishing pumps (which could handle five times that rate) and a lesser amount through a bleed line that had been added to the LOX system after the 500-F spill in August 1966.

During the 40 minutes of precooling, the launch team emptied 39,000 liters of LOX into a drainage ditch outside the perimeter fence. Normally ocean breezes dissipated the oxygen fog. On the morning of the 25th, however, there was no wind and a pronounced temperature inversion. A dense fog built up in the drainage ditch; at a culvert where the road to the slide wire bunker crossed the ditch, the invisible oxygen overflowed onto the bank.

At 6:00 a.m. the closeout crew and safety personnel left the LOX storage area. First-stage loading could begin after a three-minute chill-down of the 38,000-liter-per-minute main pumps. A security team completed its job of clearing the pad area and proceeded in three cars to the perimeter gate southwest of the LOX sphere.

The driver of the first car, Patrolman Nolan Watson, drove through the gate and parked. As he walked back to Earl Paige's car, an order over the radio directed the team to clear the slide wire bunker area. Paige turned his ignition on and heard a loud pop. Soon flames sprang up from beneath the hood. Watson ran back to his car, only to find it also on fire. About the same time, the third car burst into flames. The three guards quickly ran for cover.

A fire and rescue crew arrived in five minutes but took no action until the oxygen cloud dissipated. It was nearly 7:00 a.m. before the fire was under control, leaving three burnt hulks and a shaken crew.

Debus called for an immediate investigation. The preliminary report, rendered a week later, blamed the accident on the enriched oxygen atmosphere. Spontaneous ignition resulting from the engine heat, combustibles (oil and grease on the engine covers and gas around the carburetors) and the oxygen vapor cloud caused two of the fires, the third apparently starting when the driver turned the ignition switch.

The report criticized the practice of dumping large quantities of cryogenics and termed the resulting vapor a hazard. Recommendations included immediate studies of the drainage system leading from the LOX storage area and its dump reservoir, of entry and exit routes at pad 39 A, and of KSC's safety training course.

The major change brought about by the accident was to extend the LOX drainage pipes beyond the perimeter ditch to a marshy area farther from the pad.

moorouge
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Posts: 1746
From: U.K.
Registered: Jul 2009

posted 04-19-2014 11:59 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
I alluded to this in another '13' thread. Ken Mattingly didn't know about this either when I spoke to him during his visit to Pontefract. This is what the LOX engineer involved had to say about it.
The car fire occurred during LOX transfer pump chilldown. They gravity fed a bunch of LOX from the storage tank through the pump and then out some fairly small (3 or 4 inch) pipes under the pad perimeter road and into the swamp. No special pond or tank. It was this flow that occurred as part of the “Start Chilldown” command that created the cloud that caused the fire. Normally 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 LO2 to the Saturn V stages. Then the fill of the vehicle started.
He also mentioned another earlier incident involving LOX.
Another LOX story occurred during testing of the Saturn 500 F facility checkout vehicle (non flight). They had chilled down the transfer pump and started it up. The large flex hose (12” or so) between the tank and the transfer line took the first big slug of liquid and split with personnel standing right next to it. They shut down the pump and fled the area. There was no valve between the storage tank and the broken flex hose so all anyone could do was watch 800 thousand gallons of LOX drain onto the pad surface and across the asphalt perimeter road. It was quite a scene of a large vapor cloud for a long time. As I remember the perimeter road was frozen for weeks. Amazing nothing caught on fire from that episode. Immediately thereafter a valve was put upstream of the flex hose or the flex hose was removed.

moorouge
Member

Posts: 1746
From: U.K.
Registered: Jul 2009

posted 04-20-2014 02:55 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Here is an eyewitness account to the CDDT incident -
We were doing a CDDT, Countdown Demonstration Test, a simulated countdown including fueling the rocket to show we could do it right on the Apollo 13 launch day. The day was overcast, not a breath of wind and the humidity and temperature were just right. On that day the pure oxygen draining into the ditch next to the road did not dissipate. It just sat in the ditch. You have all heard the stories of what happens in a hospital oxygen tent if you light a cigarette. In a 100% oxygen atmosphere it almost explodes it burns so fast.

The Security Police manned the guardhouse at the entrance to the launch pad. Just before we started loading the launch vehicle with fuel and oxidizer the pad was officially cleared, except for the police who did a final sweep of the Pad. They would get in their patrol cars and drive around the pad perimeter road with red lights flashing and loud speakers blaring, "Clear the Pad." They would then report to the test conductor that the pad was officially clear for propellant loading and launch and exit the Pad through a gate near the LO2 facility. That day as we followed the patrol cars around the pad and out the gate on our console television monitors, they entered a fog bank where the dirt road was near the ditch. Normally this would have been condensed moisture from the humid air caused by the cold oxygen gas, but for Apollo 13 it evidently was pure oxygen. As the patrol cars drove though the cloud the hot grease on the engines caught fire. We saw the Security Police jump out and run to safety. A second car and then third followed and exploded in flame. No one knew what the heck was happening. We watched as the patrol cars burned with the oil, grease and gasoline acting as the fuel and the pure oxygen. The vehicles melted down to the engine blocks. Fortunately all of the patrolmen escaped. Once the excitement died down we resumed the simulated countdown. Never again did the police use that Pad exit!

All times are CT (US)

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