Author Topic: On-Pad Explosions  (Read 23315 times)

Offline edkyle99

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On-Pad Explosions
« on: 09/02/2016 07:34 PM »
In light of recent events, here are some previous relatively big on-pad explosions in the U.S. to compare.  Keep in mind that Falcon 9-29/AMOS-6 dwarfs them all.

The first was Atlas 9C with an Able upper stage, which caught fire, collapsed, and exploded during an attempted flight readiness firing at Launch Complex 12 on September 25, 1959.  The pad was out of service for eight months.

 - Ed Kyle
« Last Edit: 09/03/2016 04:19 PM by edkyle99 »

Offline Jim

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Re: On-Pad Explosions
« Reply #1 on: 09/02/2016 07:38 PM »
The Titan I were the FTS went off?

Offline edkyle99

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Re: On-Pad Explosions
« Reply #2 on: 09/02/2016 07:41 PM »
Next was Atlas 51D at LC 13 on March 11, 1960.  It only went seven feet, after the B2 engine suffered combustion instability, before falling back on its pad.  LC 13 would be out of action for seven months.

 - Ed Kyle

Offline edkyle99

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Re: On-Pad Explosions
« Reply #3 on: 09/02/2016 07:46 PM »
The Titan I were the FTS went off?
First came Titan 1 Missile No. B-5, which was released prematurely from LC 19 on August 14, 1959, causing an unplanned umbilical release that killed the engines after 2.87 seconds.  B-5 fell back onto the launch stand and disappeared in a fireball.  The pad was offline for 6 months.       

 - Ed Kyle
« Last Edit: 09/02/2016 07:55 PM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #4 on: 09/02/2016 07:52 PM »
The next on-pad explosion was the destruct system issue.  Titan 1 C-3 exploded at LC 16 on December 12, 1959 during a launch attempt.  4.2 seconds after the engines ignited, a launch destruct system relay "chattered" due to vibration, setting off the destruct charges.  Somehow the pad escaped substantial damage so that it hosted a launch only two months later.  Perhaps the destruct system saved the pad from the worst of it.

 - Ed Kyle
« Last Edit: 09/03/2016 01:35 AM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #5 on: 09/02/2016 08:06 PM »
Atlas 48D suffered a failure very similar to Atlas 51D.  It flew just a few feet from LC 11 on April 8, 1960 before falling back on its pad after a booster engine suffered combustion instability.  This failure did less damage to the launch pad this time.  LC 11 hosted its next launch only three months later.

Art LeBrun supplied a post-fire photo.

More to come ...

 - Ed Kyle 

« Last Edit: 09/02/2016 09:53 PM by edkyle99 »

Offline IRobot

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Re: On-Pad Explosions
« Reply #6 on: 09/02/2016 08:57 PM »
Atlas Agena D, May 1963.
No bang, but collapse on pad, due to structural failure, as the 2nd stage tanks were emptied.


Offline edkyle99

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Re: On-Pad Explosions
« Reply #7 on: 09/02/2016 09:52 PM »
Combustion instability struck again when Atlas 27E failed at liftoff from Vandenberg AFB 576-F on June 7, 1961.  This was the first Atlas E operational type launch attempt from a coffin launcher.  The result was a nasty failure.  The launch attempt failed immediately when the B-1 chamber lost thrust.  The site suffered heavy damage and was out of service for nine months.

 - Ed Kyle
« Last Edit: 09/02/2016 09:54 PM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #8 on: 09/02/2016 10:01 PM »
Atlas 11F blew up upon launched from Cape Canaveral LC 11 on April 9, 1962.  Atlas ignited its engines and began to rise, but suddenly, only a few feet above the launch stand, its sustainer engine turbopump exploded.  11F disappeared in a giant fireball, leaving only scattered remains around a smoking launch pad.  LC 11 would be out of action for four months.  I don't have any photos, but a video of the dramatic failure can be found at Critical Past.
http://www.criticalpast.com/video/65675023307_Atlas-missile11F_Atlantic-Missile-Range_large-explosion_fire-and-smoke

 - Ed Kyle
« Last Edit: 09/02/2016 10:03 PM by edkyle99 »

Offline Graham

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Re: On-Pad Explosions
« Reply #9 on: 09/02/2016 10:07 PM »
I was planning on creating a thread asking about this very thing. Thanks Ed, and of course the late Mr. LeBrun for the pictures and info.
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Offline edkyle99

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Re: On-Pad Explosions
« Reply #10 on: 09/02/2016 10:13 PM »
The Titan Operational Suitability Test Facility at Vandenberg AFB, was built as a prototype for future operational Strategic Air Command Titan ICBM launch complexes.  It consisted of a 160 foot deep silo complex equipped with a hydraulically driven elevator designed to lift a fully fueled Titan, its launch stand, and its launch umbilical mast to the surface for launch.  Titan 1 missile V-2 was installed in the silo to test the design.  On December 3, 1960, a full wet dress rehearsal was performed using Titan V-2.  The missile was in its silo for the 15 minute LOX loading, then was raised to the surface for final countdown.  After the countdown test was completed the missile tanks were vented and the missile began to be lowered back into the silo where propellant offloading would be performed.  During the lowering process, the elevator failed.  The missile plummeted to the bottom of the silo causing a series of explosions that ejected the 160 ton, multi-story elevator "crib" structure straight up out of the silo.  The two massive silo caps were also tossed aside.  One five-ton piece of the site landed 1,200 feet away.

This launch site damage was permanent.  OSTF was never rebuilt.  It remains to this day a giant hole in the ground.

 - Ed Kyle
« Last Edit: 09/02/2016 10:14 PM by edkyle99 »

Offline Blackstar

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Re: On-Pad Explosions
« Reply #11 on: 09/03/2016 12:24 AM »

This launch site damage was permanent.  OSTF was never rebuilt.  It remains to this day a giant hole in the ground.



I took these a couple of years ago at the site.

Offline edkyle99

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Re: On-Pad Explosions
« Reply #12 on: 09/03/2016 01:33 AM »
Atlas 45F faltered when its B-1 main fuel valve failed to open at liftoff from VAFB 576G on October 4, 1963.  With only one of the two boosters firing, the missile toppled right over on its side and exploded.  The elevator silo pad was damaged, but not as severely as it would have been in the case of a direct fall back.  Another launch took place about 10 weeks later from this site.

SDASM images.

 - Ed Kyle
« Last Edit: 09/03/2016 01:44 AM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #13 on: 09/03/2016 01:42 AM »
Atlas 3F repeated the 45F failure, from the very same launch pad, on April 3, 1964.  Again the B-1 main fuel valve failed to open.  Again the rocket toppled and exploded.  This time six months would pass before another launch from 576G.

 - Ed Kyle
« Last Edit: 09/03/2016 01:42 AM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #14 on: 09/03/2016 01:57 AM »
Atlas Centaur 5 suffered a sudden main fuel valve closure at T+0.88 seconds during its launch from Cape Canaveral LC 36A on March 2, 1965.  The rocket fell straight back down into the launcher and exploded, creating a mushroom cloud.  It was the largest on-pad explosion at the Cape for more than five decades, until Falcon 9-29/AMOS-6 on September 1, 2016.  LC 36A didn't host another launch for 16 months.

 - Ed Kyle
« Last Edit: 09/03/2016 01:57 AM by edkyle99 »

Offline rayleighscatter

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Re: On-Pad Explosions
« Reply #15 on: 09/03/2016 03:36 AM »
In 1980 a Titan II ICBM in Arkansas was struck by a dropped socket wrench socket. The rocket started leaking fuel and several hours later the hypergolic fuel exploded killing an airman as well as destroying the rocket and silo.

Offline russianhalo117

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Re: On-Pad Explosions
« Reply #16 on: 09/03/2016 04:07 AM »
In 1980 a Titan II ICBM in Arkansas was struck by a dropped socket wrench socket. The rocket started leaking fuel and several hours later the hypergolic fuel exploded killing an airman as well as destroying the rocket and silo.
Actually the Silo (LC374-7) survived with some damage on the order of $225,322,670 in 1980 Dollars. The silo was stripped and sealed during decommissioning after USAF decided that the cost to restore to Titan II Service was to great and the scheduled  conversion of all 373 and 374 silos in Arkansas to the Minuteman series was a short time later cancelled by the Regan Administration.
Quote
The Titan II Missile Launch Complex 374-7 Site was listed in the National Register of Historic Places on February 18, 2000.
Titan II Missile Launch Complex 374-7 Background info: http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2543
Titan II pads (373 and 373 SMS units) In Arkansas: http://www.encyclopediaofarkansas.net/encyclopedia/entry-detail.aspx?entryID=2266
https://www.facebook.com/forbidden.hillcrest/posts/720157944707720
http://themilitarystandard.com/missile/titan2/silo/index.php
https://en.wikipedia.org/wiki/LGM-25C_Titan_II
« Last Edit: 09/03/2016 04:08 AM by russianhalo117 »

Offline Chrup4

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Re: On-Pad Explosions
« Reply #17 on: 09/03/2016 07:07 AM »
Samos 3 exploded on LC 1-1 at PALC on September 9, 1961. A pad umbilical did not detach at liftoff, which caused the Atlas-Agena B to switch from internal to external power. The engines shut down and the Atlas dropped back onto the pad and exploded in a huge fireball, resulting in the total loss of the photoreconnaissance satellite.

Pad damage was evidently not that bad as Samos 4 flew from LC 1-1 only nine weeks later.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #18 on: 09/03/2016 07:16 AM »
The first Thor IRBM lifted from LC-17B at Cape Canaveral on January 26, 1957. Almost immediately at liftoff, the engine shut down and the missile fell back through the launch stand and exploded. It was unclear what caused the failure until a film review of prelaunch preparations showed pad crews dragging a LOX filler hose through a sandy area, thus it was concluded that the LOX became contaminated with foreign debris, resulting in valve failure.

Pad damage was repaired quickly and LC-17B hosted the second Thor test flight in April 1957.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #19 on: 09/03/2016 07:24 AM »
The third Thor IRBM test, Missile 103, never made it off the pad. During prelaunch preparations on May 22, 1957, the LOX tank exploded and for the second time in 5 months, LC-17B had to be repaired and was out of use until the following September.

This incident was traced to a stuck LOX vent valve which allowed tank pressure to build up to the point where it suffered a structural failure, combined with a careless technician who failed to pay attention to a LOX pressure gauge reporting dangerous pressure levels.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #20 on: 09/03/2016 07:31 AM »
The fifth Thor test on October 3, 1957, was launched from LC-17A. In a near repeat of Thor 101, the missile lost thrust almost immediately at liftoff, fell back through the launch stand, and exploded. This incident was traced to a failure of the gas generator valve to open.

Pad damage was evidently quite minor, as LC-17A hosted the launch of Thor 108 on October 24, only 21 days later.
« Last Edit: 09/03/2016 07:36 AM by Chrup4 »

Offline Chrup4

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Re: On-Pad Explosions
« Reply #21 on: 09/03/2016 07:40 AM »
(no picture)

Thor 121 launched from LC-17B on April 19, 1958 and resulted in yet another loss of thrust at liftoff followed by an explosion. This time, the culprit was apparently a collapsed fuel duct.

LC-17B was out of service for two months and hosted its next launch in June.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #22 on: 09/03/2016 08:04 AM »
A couple of points about the Atlas/Titan failures mentioned earlier.

It is probably correct that the explosion of Titan C-3 was less damaging than B-5 due to the nature of the failure. Since the RSO charges went off, they would have split the first stage tanks open and largely prevented propellant mixing from occurring (which is exactly what they're designed to do), resulting in a much less energetic blast. I would imagine that Titan B-5's RP-1 tank probably rammed into the LOX tank when the vehicle broke apart (somewhat like what happened with Challenger's external fuel tank), causing a lot of propellant mixing and thus a rather violent explosion.

Atlas 51D was intentionally destroyed by the Range Safety Officer once it became apparent that there was a malfunction in one engine. There is a closeup shot showing the tanks splitting open and an explosion in the area of the common bulkhead where the RSO charges were located.

Atlas 48D did not get off the pad to my knowledge. I've never seen film of this launch, but as I understood it, the sustainer engine exploded prior to liftoff which would explain why the thrust section is resting inside the launcher mechanism in the aftermath photo.

Also I can't account for the quick damage recovery from Samos 3 given the similarity of the failure to Titan B-5 and Atlas AC-5, except maybe the Agena's hypergolic propellant did not explode with as much force as the cryo propellants in the other vehicles and thus less pad damage.

Offline Hobbes-22

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Re: On-Pad Explosions
« Reply #23 on: 09/03/2016 11:21 AM »
N-1 5L: The LOX turbopump for engine no. 8 exploded just before liftoff. The rocket managed to clear the tower, at 10 seconds into the flight the KORD system started shutting down 29 of the 30 engines. The rocket crashed on the pad, wiping it out and damaging the second N-1 pad nearby.

The photo shows the escape system firing to yank the capsule away from the N-1 as it begins to fall back down onto the pad.


Offline kevin-rf

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Re: On-Pad Explosions
« Reply #24 on: 09/03/2016 12:24 PM »
So how is the Sea Launch NSS-8 launch failure in jan. 30, 2007 counted. Would this be considered an American launch failure due to partial Boeing ownership? Also wouldn't, okay just checked F9 contains ~20% more propellants than the Zenit. So would it be the second largest US pad explosion? Third going to AC-5?
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Offline edkyle99

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Re: On-Pad Explosions
« Reply #25 on: 09/03/2016 03:23 PM »
Samos 3 exploded on LC 1-1 at PALC on September 9, 1961. A pad umbilical did not detach at liftoff, which caused the Atlas-Agena B to switch from internal to external power. The engines shut down and the Atlas dropped back onto the pad and exploded in a huge fireball, resulting in the total loss of the photoreconnaissance satellite.

Pad damage was evidently not that bad as Samos 4 flew from LC 1-1 only nine weeks later.
Thanks for adding this one!   This was Atlas 106 D and Agena B A2201.  I have to date found no photos of the failure or its aftermath.  This could have been a more powerful explosion than Atlas-Able, the previous U.S. largest.  At the time, Atlas Agena B was the largest, most-powerful U.S. launch vehicle.  The next launch from Point Arguello LC 1-1 (later renamed VAFB SLC 3 West) took place on November 22, 1961.  It also failed, but not on the pad.

 - Ed Kyle
« Last Edit: 09/03/2016 03:31 PM by edkyle99 »

Offline edkyle99

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Re: On-Pad Explosions
« Reply #26 on: 09/03/2016 03:37 PM »
So how is the Sea Launch NSS-8 launch failure in jan. 30, 2007 counted. Would this be considered an American launch failure due to partial Boeing ownership? Also wouldn't, okay just checked F9 contains ~20% more propellants than the Zenit. So would it be the second largest US pad explosion? Third going to AC-5?
To me, Zenit 3SL was a Ukrainio-Russian rocket with a U.S. payload fairing.  It definitely was not an "American launch vehicle".  It might fall into an "International" category.  (Atlas 5 has a European payload fairing, but I've never heard anyone suggest that it is a European launch vehicle.)

In terms of U.S. pad (or near-pad) explosions, Falcon 9 is likely most powerful, followed by Antares and Atlas Centaur 5.  The three had GLOWs of about 587 tonnes, 286 tonnes, and 138 tonnes, respectively.  (We can debate whether Antares fits the "on-pad" category.  I think it fits due to the severe pad damage.  We can also debate whether Antares is a "U.S. launch vehicle", but maybe not here!) 

Amazing that we've seen the two worst such U.S. failures during just the past two years.

 - Ed Kyle
« Last Edit: 09/03/2016 03:45 PM by edkyle99 »

Offline HMXHMX

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Re: On-Pad Explosions
« Reply #27 on: 09/03/2016 04:11 PM »
The fifth Thor test on October 3, 1957, was launched from LC-17A. In a near repeat of Thor 101, the missile lost thrust almost immediately at liftoff, fell back through the launch stand, and exploded. This incident was traced to a failure of the gas generator valve to open.

Pad damage was evidently quite minor, as LC-17A hosted the launch of Thor 108 on October 24, only 21 days later.

A second-hand personal note about Thor failures...

My good friend and mentor the late Max Hunter (Thrust into Space, 1966, and the fictional movie character "Dr. Hunter" in "2001: A Space Odyssey" hibernaculum, as a homage from his friend Arthur C. Clarke), once told me why Thor pads could be brought back on line so quickly.  Max was Chief Engineer on Thor (and also the S-IV and S-IVB stages).

The Thor was built with separate propellant tanks.  If it fell back onto the pad in a more or less vertical orientation, the vehicle descended below the pad deck through the center hole, hit the flame deflector and skidded along it, breaking neatly into two parts, one fuel and one oxidizer. One tank would break open below the deck, the other above. The propellants didn't inertially mix as thoroughly as was the case on other pads, such as Atlas.  While there was a still large conflagration, the blast effects were less than were seen on other stands.

Offline Archibald

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Re: On-Pad Explosions
« Reply #28 on: 09/03/2016 06:26 PM »
Ah. So SpaceX explosion was bigger than Atlas Centaur AC-5 ? That record stood for 51 years.
(my favorite rocket explosion of all times)
 Didn't realised it, but of course Falcon 9 is a lot bigger than the old Atlas.
« Last Edit: 09/03/2016 06:34 PM by Archibald »

Offline Nomic

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Re: On-Pad Explosions
« Reply #29 on: 09/03/2016 07:04 PM »
Stretching to test stand explosions, what about the Titan IV booster (after a redesgin became the srmu)  explosion at Edwards AFB? Only 280 tonnes of prop though...

Offline HMXHMX

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Re: On-Pad Explosions
« Reply #30 on: 09/03/2016 11:40 PM »
Stretching to test stand explosions, what about the Titan IV booster (after a redesgin became the srmu)  explosion at Edwards AFB? Only 280 tonnes of prop though...

OK, another anecdote...I was on that stand with my business partner something like a month before the firing (and kaboom). Being a liquid guy, and not liking solids at all, I remember being very nervous walking under the plugged nozzle, and he said something soothing like "if it blows up you'll never even feel it."  Neither of us had any idea that it was going to do that, of course. 

If you can visit the Evergreen Air Museum in Oregon, you can see an unloaded version of the composite case they used.

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Re: On-Pad Explosions
« Reply #31 on: 09/03/2016 11:59 PM »
If the Titan II ICBM silo explosion of 1980 counts, and we're including other nationalities:

Nedelin Disaster: On the 24th of October, 1960 at Baikonur the second stage engines of an R-16 ICBM prototype activated on the pad. The missile was instantly destroyed and over 90 people were incinerated, including Nedelin himself. The pad was closed until 1961, and serves as a memorial to the disaster today.





Offline Chrup4

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Re: On-Pad Explosions
« Reply #32 on: 09/04/2016 01:17 PM »
Thanks for adding this one!   This was Atlas 106 D and Agena B A2201.  I have to date found no photos of the failure or its aftermath.  This could have been a more powerful explosion than Atlas-Able, the previous U.S. largest.  At the time, Atlas Agena B was the largest, most-powerful U.S. launch vehicle.  The next launch from Point Arguello LC 1-1 (later renamed VAFB SLC 3 West) took place on November 22, 1961.  It also failed, but not on the pad.

The video of the launch is on CriticalPast, but I've also never found any still photos of Samos 3 other than the prelaunch one I posted earlier. One of the more peculiar things I noted in the video is that the Agena appears to break apart before the fireball reaches it. The best I figure out is that the RSO charges on the Agena went off from vibration as the Atlas started to break up. This was not the first time the umbilicals on LC 1-1 caused trouble since they were also responsible for the loss of Samos 1 eleven months earlier.

For the record, Atlas 9C was a larger blast than Samos 3 because the common bulkhead between the propellant tanks collapsed, which caused the entire load of LOX to fall into the RP-1 tank and turn into explosive gel. The explosive force was tremendous, enough to completely level the pad umbilicals and hurl a one-ton piece of the service tower about 50 feet. As noted earlier, LC-12 took seven months to restore while the damage from Samos 3 was completely repaired in a month and a half.

I'm also fairly certain that Vanguard TV-3, Samos 3, and Cygnus CRS-3 were the only pad explosions of a US launch vehicle during an actual orbital launch attempt (assuming you discount Atlas-Centaur AC-5 because it had only a dummy Surveyor probe for a payload). Every other pad explosion I can think of was suborbital or occurred during a PFRT.
« Last Edit: 09/04/2016 06:12 PM by Chrup4 »

Offline Chrup4

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Re: On-Pad Explosions
« Reply #33 on: 09/04/2016 01:37 PM »
The Thor was built with separate propellant tanks.  If it fell back onto the pad in a more or less vertical orientation, the vehicle descended below the pad deck through the center hole, hit the flame deflector and skidded along it, breaking neatly into two parts, one fuel and one oxidizer. One tank would break open below the deck, the other above. The propellants didn't inertially mix as thoroughly as was the case on other pads, such as Atlas.  While there was a still large conflagration, the blast effects were less than were seen on other stands.

It could be a combination of the pad design and the nature of the failure. Like noted earlier, Titan I B-5 caused enough damage to put LC-19 out of service for six months while C-3 only put LC-16 out for two months. As I understand, most of the damage to LC-19 was the umbilical tower, which suffered extensive fire damage.

B-5 also got further off the pad than C-3, a couple feet before the engines cut off. Most likely, the engines struck the flame deflector pit and got rammed upward into the RP-1 tank, which then rammed up into the LOX tank. Since it fell down from a couple of feet up, there must have been considerable force being imparted into the missile as it hit the flame deflector. The propellants thus mixed, blew, and caused extensive damage.

C-3 really didn't even lift, maybe an inch or so when the RSO charges activated and split the first stage tanks open, which would have mostly just spilled out the propellants and caused a low intensity deflagration.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #34 on: 09/04/2016 01:49 PM »
The third Redstone missile test, RS-3, took place from LC-4 at CCAS on May 3, 1954 and ended ignominiously when the engine cut off one second after liftoff, causing the missile to fall back onto the launch stand in a ball of white flame.

Afterwards, Major General Holger Toftoy asked Werner Von Braun "Werner, why did the rocket explode?" Von Braun replied that he had no idea, but they would review telemetry data to find out. When Toftoy continued to press Von Braun for the cause of the failure, he replied "It exploded because the damn sonofabitch blew up!"

Von Braun subsequently pushed for better quality workmanship on the Redstones, noting acidly "Maximum reliability will be achieved when the target area of the missile becomes more dangerous than the launching area."

Offline Chrup4

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Re: On-Pad Explosions
« Reply #35 on: 09/04/2016 02:05 PM »
N-1 5L: The LOX turbopump for engine no. 8 exploded just before liftoff. The rocket managed to clear the tower, at 10 seconds into the flight the KORD system started shutting down 29 of the 30 engines. The rocket crashed on the pad, wiping it out and damaging the second N-1 pad nearby.

The photo shows the escape system firing to yank the capsule away from the N-1 as it begins to fall back down onto the pad.

There were many Soviet pad explosions that were spectacular beyond belief, but the last one to date was the 1990 Zenit disaster. I'm not aware of any happening in the post-Soviet era unless there was a missile test or two at some point.

Aside from the Nedelin Catastrophe and N-1 5L, there were numerous R-7s that blew on or near the pad over the years. The very first R-36 launch in 1963 lost thrust at liftoff and fell back onto the pad. Two Kosmos (R-14) boosters blew on the pad in the early 70s, one lost thrust at liftoff, the other caught fire during servicing and killed 9 people.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #36 on: 09/04/2016 04:13 PM »
The final Titan I R&D launch was that of Missile V-4 from VABF's 395-A1 on the evening of May 1, 1963. In an ominous prediction of Atlas 45F five months later, the missile experienced a stuck engine valve that prevented the LR-87 engines from achieving sufficient thrust to lift the 110 ton missile, which then tipped over and exploded on impact with the ground.

395-A1 was repaired in two months and hosted Titan SM-7 on August 15.

Online Phillip Clark

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Re: On-Pad Explosions
« Reply #37 on: 09/05/2016 03:04 AM »
I am surprised that no-one has mentioned the on-the-pad explosion of the Brazil's third VLS.

The launch was scheduled for August 25, 2003 and it was planned to orbit the SATEC and UNOSAT 1 payloads.   On August 22 one of the four strap-on boosters exploded, with the launch pad being destroyed and 21 people being killed.

Work on the VLS continued until earlier this year, when it was decided to develop the VLM-1 instead.

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Re: On-Pad Explosions
« Reply #38 on: 09/05/2016 06:13 AM »
A factor in the rapid repair of the old IRBM and ICBM pads in the 60s was that these were top-priority national programs with unlimited funding, so spare pad hardware was stockpiled. Pad explosions were expected and planned for. Note how launch support equipment was well separated from the pads and protected by concrete blast walls (or the long-vanished 'Blockhouses"). Also, the RP-1 usually burned off quickly, so there usually was not thermal damage to the underlying concrete structure.

SpaceX clearly thought pad explosions were a thing of the past, since the fueling and other support equipment was located close to the pad and was completely fried by the prolonged RP-1 fire. Also, witnesses report spalling and cracking of the concrete pad and exhaust duct. It will take a long time to get LC-40 operational again.

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Re: On-Pad Explosions
« Reply #39 on: 09/05/2016 06:50 AM »
Will Space X have to pay the bill for the repairs or is that the responsibility of the CCAFB?

Offline Chrup4

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Re: On-Pad Explosions
« Reply #40 on: 09/05/2016 10:54 AM »
A factor in the rapid repair of the old IRBM and ICBM pads in the 60s was that these were top-priority national programs with unlimited funding, so spare pad hardware was stockpiled. Pad explosions were expected and planned for. Note how launch support equipment was well separated from the pads and protected by concrete blast walls (or the long-vanished 'Blockhouses"). Also, the RP-1 usually burned off quickly, so there usually was not thermal damage to the underlying concrete structure.

I had heard that the damage from Atlas AC-5 was mostly repaired in three months even though the next launch from LC-36A was not for over a year (probably more fire than structural damage). The Atlas-Centaur launch rate was small (only two during the time LC-36A was offline) and probably 36B alone was enough to handle it. Also while LC-13 was offline six months following Atlas 51D, some of that delay could have been due to converting the pad for Atlas E launches.

As for the RP-1 burning off quickly, you have to remember also that most of it doesn't actually go off in an explosion. Even on N1-5L, about 80% of the propellant load in the booster did not ignite and what did was mostly in the first stage. After the blockhouse crew were allowed outside, there were unburned droplets of RP-1 raining down from the sky. Despite the blast being intense enough to level the service towers and cave in the concrete launch stand, they still recovered most of the vital telemetry tapes intact from the rubble.

Offline kevin-rf

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Re: On-Pad Explosions
« Reply #41 on: 09/05/2016 11:00 AM »
Will Space X have to pay the bill for the repairs or is that the responsibility of the CCAFB?

Considering they are the ones who built and operate it, I would assume they (or insurance) has to not only pay for any pad repairs, but also any damage they inflicted on other people's equipment.
« Last Edit: 09/05/2016 11:02 AM by kevin-rf »
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Offline Chrup4

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Re: On-Pad Explosions
« Reply #42 on: 09/05/2016 02:25 PM »
Operation Fishbowl in 1962 involved a series of high altitude nuclear tests launched from Johnson Island in the Pacific on Thor IRBMs. After the "Bluegill" launch failed on June 2, the next attempt, code named Bluegill Prime, was made on July 25 but ended disastrously when the Thor caught fire on the pad. A stuck engine value cut the flow of LOX to the combustion chamber and RP-1 ignited on contact with the hot engine. The Range Safety Officer sent the destruct command and blew up the Thor on the pad, also destroying the nuclear warhead.

The pad area was extensively contaminated with plutonium and had to be cleaned up before the destroyed launch stand could be rebuilt.

Offline Jim

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Re: On-Pad Explosions
« Reply #43 on: 09/05/2016 03:25 PM »

SpaceX clearly thought pad explosions were a thing of the past, since the fueling and other support equipment was located close to the pad

Not really, they were protected by berms just like days of old.  They reused the existing Titan berms

You can see here

http://forum.nasaspaceflight.com/index.php?topic=40868.msg1578330#msg1578330
« Last Edit: 09/05/2016 03:32 PM by Jim »

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Re: On-Pad Explosions
« Reply #44 on: 09/05/2016 10:22 PM »
video of pad explosion of Atlas-Centuar AC-5 (video of explosion starts at 2:13)

Largest Explosion

https://www.youtube.com/watch?v=NgqnlUifggw?t=000

« Last Edit: 09/05/2016 10:24 PM by catdlr »
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Re: On-Pad Explosions
« Reply #45 on: 09/06/2016 04:02 AM »
Very fascinating series, Ed.

But what I'm taking away from this is why there were over 43 separate launch pads in the old days.

Blow one up? Go fly on another while you examine the charred, painted rocket pieces and rebuild the pad.

Took a while to rebuild pads, and it is only slightly faster today with light-gantry launches using strongbacks.
"Why is the logo on the side of a rocket so important?"
"So you can find the pieces." -Jim, the Steely Eyed

Offline Chrup4

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Re: On-Pad Explosions
« Reply #46 on: 09/06/2016 10:36 AM »
video of pad explosion of Atlas-Centuar AC-5 (video of explosion starts at 2:13)

Oddly enough, in all this time nobody's turned up the postflight launch reports for AC-1 or AC-5 although the reports for several early Centaur launches are online.

Offline Chrup4

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Re: On-Pad Explosions
« Reply #47 on: 09/06/2016 11:17 PM »
The final Titan I R&D launch was that of Missile V-4 from VABF's 395-A1 on the evening of May 1, 1963. In an ominous prediction of Atlas 45F five months later, the missile experienced a stuck engine valve that prevented the LR-87 engines from achieving sufficient thrust to lift the 110 ton missile, which then tipped over and exploded on impact with the ground. 395-A1 was repaired in two months and hosted Titan SM-7 on August 15.

I should add, I saw a video of Titan I V-4 on the net a long time ago. It was just like Atlas 45F--nighttime launch where the thing tipped over as soon as it was released. There's a closeup shot on the engines which are essentially not firing at all. I also once saw a brief clip of Redstone RS-3 on a Youtube rocket failure compilation. Otherwise most of those videos just have failures everyone's already seen hundreds of times like Juno AM-16, Atlas 27E, and Delta II 241.

Offline koroljow

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Re: On-Pad Explosions
« Reply #48 on: 03/12/2017 06:02 PM »
Samos 3 exploded on LC 1-1 at PALC on September 9, 1961. A pad umbilical did not detach at liftoff, which caused the Atlas-Agena B to switch from internal to external power. The engines shut down and the Atlas dropped back onto the pad and exploded in a huge fireball, resulting in the total loss of the photoreconnaissance satellite.

Pad damage was evidently not that bad as Samos 4 flew from LC 1-1 only nine weeks later.
Thanks for adding this one!   This was Atlas 106 D and Agena B A2201.  I have to date found no photos of the failure or its aftermath.  This could have been a more powerful explosion than Atlas-Able, the previous U.S. largest.  At the time, Atlas Agena B was the largest, most-powerful U.S. launch vehicle.  The next launch from Point Arguello LC 1-1 (later renamed VAFB SLC 3 West) took place on November 22, 1961.  It also failed, but not on the pad.

 - Ed Kyle

Sorry (again) for digging up an old thread.  But if someone (Ed?) ist still interested: this is the link to a video showing Atlas 106D's fate:


-Olaf-
Geschichte und Geschichten aus mehr als 5 Jahrzehnten Raumfahrt:
http://www.raumfahrtkalender.de

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Re: On-Pad Explosions
« Reply #49 on: 04/05/2017 05:49 PM »
To answer one of the earlier queries, the reason the Agena appears to break up before the fireball reaches it is because of the Inadvertent Separation Destruct System. This system was present on most Atlas-Agena vehicles, and it was designed to destroy the Agena if it would prematurely separate from the stack. So essentially what happened on Samos 3 is that the Atlas started to break up and this tripped the ISDS charges.

An ISDS malfunction caused the loss of the very first Atlas-Agena flown, and you may recall that they had to destroy Mariner 1's booster just before staging occurred since the Range Safety charges on the Agena would then be disabled.


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Re: On-Pad Explosions
« Reply #50 on: 04/05/2017 08:26 PM »
Note the thrust ring and forward portion/adapter section of the Atlas LOX tank survived more-or-less intact. The second photo shows what I believe are the remains of the Agena.

There were a high number of VAFB failures caused by problems with the launcher/pad equipment for some reason. Samos 1, Samos 3, Discoverer 9, Midas 6, Atlas 71F, Atlas 64E (sort of), a couple of Atlas D failures off 576-B, Titan II N-7. The only Cape failures caused by the pad equipment (that I know of) were Titan I B-5 and Atlas 7D, neither of which were orbital launches.

Edit: I just remembered another Cape failure--Titan I AJ-10, again though not an orbital launch.
« Last Edit: 04/08/2017 12:46 AM by WallE »

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Re: On-Pad Explosions
« Reply #51 on: 04/06/2017 07:17 PM »
Atlas 48D suffered a failure very similar to Atlas 51D.  It flew just a few feet from LC 11 on April 8, 1960 before falling back on its pad after a booster engine suffered combustion instability.  This failure did less damage to the launch pad this time.  LC 11 hosted its next launch only three months later.

I read the postflight report for 48D. The B-2 engine malfunctioned, causing a thrust section explosion, and an automatic shutoff command was sent to the entire propulsion system. This happened before it developed sufficient thrust, so the missile never lifted from the pad. It sat there and burned for 60 seconds until the propellant tanks exploded.

As for 51D, the failure occurred in the B-1 engine and it did lift from the pad. There was a post in here claiming it was an RSO destruct, but while I don't have a postflight report for 51D, the 48D report and several other Convair docs have no allusions in them to it being destroyed intentionally. In the photo here, you can see the engines are still running which would not happen in an RSO destruct (propulsion system shutoff followed by detonation of the destruct charges). It seems that what actually happened is that an explosion in the thrust section damaged the pneumatic system and caused structural failure of the missile. I could still be wrong but unless the postflight report for 51D turns up, sketchy details are all I have.

They had also taken the turbine exhaust duct off LC-11 and LC-13 in early 1960 and after the back-to-back pad explosions, it was decided to put it back on just as a precaution although there wasn't any evidence that the absence of the duct had caused the failures.

Edit: LC-12 and LC-14 still had their ducts because they were used for space launches which did still have PFRFs. My mistake
« Last Edit: 04/07/2017 12:49 AM by WallE »

Offline Proponent

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Re: On-Pad Explosions
« Reply #52 on: 04/06/2017 10:50 PM »
Thanks much, WallE -- that's a very interesting account.  Was there any particular reason for removing the turbine duct in the first place?
« Last Edit: 04/06/2017 11:00 PM by Proponent »

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Re: On-Pad Explosions
« Reply #53 on: 04/07/2017 12:45 AM »
Thanks much, WallE -- that's a very interesting account.  Was there any particular reason for removing the turbine duct in the first place?

They took the duct off because it impeded the removal of covers installed on the turbine exhaust during pressure testing and since they had stopped doing Pre Flight Readiness Firing tests (aside from space launcher Atlases) by early 1960, there was no concern about the Atlas's thrust section being exposed to the turbine exhaust for long periods of time.  After the 51D and 48D failures, in addition to reinstalling the duct, camera coverage of the flame deflector pit was increased. Also they wanted the pads to comply with the configuration of Atlas D missile silos.

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Re: On-Pad Explosions
« Reply #54 on: 04/08/2017 01:03 AM »
As one more pad explosion not yet mentioned, Atlas 19D exploded on 576-A1 at VAFB March 5, 1960 when a fire started during a fuel loading exercise. This brings the Atlas pad explosion tally to five for both the East Coast (9C, 51D, 48D, 11F, and AC-5) and West Coast (19D, 27E, 106D, 45F, and 3F).

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Re: On-Pad Explosions
« Reply #55 on: 04/08/2017 02:06 AM »
I think that a few years ago Joel Powell did an article on Atlas pad crumples. Not all of them went boom. In fact, I think he was more interested in the ones that crumpled but did not explode, because they were not recorded regularly.

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Re: On-Pad Explosions
« Reply #56 on: 04/08/2017 02:48 AM »
I think that a few years ago Joel Powell did an article on Atlas pad crumples. Not all of them went boom. In fact, I think he was more interested in the ones that crumpled but did not explode, because they were not recorded regularly.

Atlas 190D famously crumpled on SLC-4W May 11, 1963 and was recorded on camera, we've all seen than one. The booster intended to launch Mariner 6 also crumpled, but its collapse was averted by two quick-thinking technicians. Atlas collapses also happened a couple of times at operational silo facilities.

The Mercury astronauts were in a high risk profession; John Glenn flew when the Atlas was batting .500. Atlas 52D blew up during an operational test from the West Coast only about 24 hours after Glenn's launch. When Gordon Cooper flew at the end of the Mercury program, things didn't get much better; there were four Atlas failures in the first three months of 1963, three of which were D-series (ie. a potential direct problem for Mercury).

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Re: On-Pad Explosions
« Reply #57 on: 04/10/2017 01:49 PM »

An ISDS malfunction caused the loss of the very first Atlas-Agena flown, and you may recall that they had to destroy Mariner 1's booster just before staging occurred since the Range Safety charges on the Agena would then be disabled.

Staging does not disable the upper stage FTS

Offline WallE

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Re: On-Pad Explosions
« Reply #58 on: 04/10/2017 03:17 PM »
Staging does not disable the upper stage FTS

https://archive.org/stream/nasa_techdoc_19750065548/19750065548_djvu.txt

"5. 3 AGENA B FLIGHT TERMINATION SYSTEM

This system consists of two independent circuits which utilize the dual command destruct signal inputs from the Atlas first booster. These circuits and destruct charge are located in the adapter section between the Agena B and the Atlas. This provision will permit the destruct system to remain with the Atlas on separation which will eliminate weight and destruct capability during the Agena boost phase. Dual independent premature separation destruct circuits are also provided. Each circuit consists of independent battery, wiring, and squibs for the initiation primer. These circuits are actuated when a lanyard releases either of the two (2) separation switches mounted on the adapter at the base of the vehicle. Some components of each circuit are shared with the command destruct circuits. These circuits are disarmed and "safed" before programmed separation of the Agena B. Detailed information on this system is provided in LMSD-447590-A, Ranger Flight Termination System, 28 February 1961, Confidential. "

"2. 3 WAIVER REQUIREMENTS

The Flight Range Safety Waiver requested in accordance with AFMTC instructions* is required because:

a. The instantaneous impact point will have to cross South Africa.

b. Due to weight considerations which would compromise the mission, a separate and independent destruct system with R-F receivers and attendant electronic equipment is not desired."

To make a long story short, the Agena didn't have its own FTS due to weight restrictions, only the ISDS which was disabled at staging. The details on Centaur are less clear. The mission reports for AC-6 indicate that it had an ISDS, but it doesn't seem that it was carried on all launches (certainly not on AC-43 anyway). All Centaurs did have a separate FTS, which was used several times over the years. So it's technically correct that staging didn't disable the FTS since the Agena lacked its own FTS and was left without any Range Safety destruct capability post-staging.

The Mod 3 GE guidance system on the Atlas was a reliability disaster and it malfunctioned numerous times (Samos 1, Samos 4, Mariner 1, a couple of Ranger launches, several missile tests, etc) before the Lewis Spaceflight Center stepped in and initiated a quality improvement program on Atlas.
« Last Edit: 04/10/2017 05:14 PM by WallE »

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Re: On-Pad Explosions
« Reply #59 on: 04/10/2017 05:04 PM »

1.  The details on Centaur are less clear. The mission reports for AC-6 indicate that it had an ISDS, but it doesn't seem that it was carried on all launches (certainly not on AC-43 anyway). All Centaurs did have a separate FTS, which was used several times over the years.

2.  I probably should have phrased that earlier post better since it makes it sound as if the Agena had a separate FTS, which it didn't.

1.  ISDS is not really a "system".  It is just a series of lanyards or break wires across stage planes or SRM attach points that are enabled and then disable at appropriate times.  The basic stage/SRM FTS charges are used and there are no additional charges. 

2.  That was important for GATV. 

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Re: On-Pad Explosions
« Reply #60 on: 04/10/2017 05:28 PM »
2.  That was important for GATV.

GATV was modified from the standard Agena in several ways, and apparently the Range Safety system was also set up so that it fired a slug through the propellant tanks rather than the usual system of splitting the tanks open. This was so that if the FTS charges accidentally went off in orbit, it wouldn't create a cloud of debris that would endanger the Gemini.

Some would argue that GATV wasn't a "real" Agena, but a customized Agena variant just as the GLV wasn't a "real" Titan II.
« Last Edit: 04/10/2017 05:38 PM by WallE »

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Re: On-Pad Explosions
« Reply #61 on: 04/10/2017 05:39 PM »
Some would argue that GATV wasn't a "real" Agena, but a customized Agena variant

That would apply to all Agenas.  They were all produced in the open on a white contract to a generic/standardized configuration and then each program modified them for their particular application.  A GAMBIT Agena was just as customized as a GATV.

Offline WallE

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Re: On-Pad Explosions
« Reply #62 on: 04/10/2017 06:06 PM »
That would apply to all Agenas.  They were all produced in the open on a white contract to a generic/standardized configuration and then each program modified them for their particular application.  A GAMBIT Agena was just as customized as a GATV.

The Atlas SLV-3 and Agena D had emerged out of Lewis's proposal for a standardized Atlas-Agena. While the Atlas was more-or-less the same on every launch (barring adapter section widths for different upper stages and the long tank Atlas SLV-3A), the Agenas did indeed still vary a lot depending on the mission, especially for DoD missions where they often remained attached to the payload and carried special hardware or were used for in-orbit maneuvers.

Some of the changes to Agena D over Agena B also involved improved hardware, checkout, and assembly practices, per the Lewis suggestions. This went a long way to improving the Agena's reliability, and although failures still happened, the success rate of them dramatically improved over 1959-62 when it was at about 50%.

What Jim says about the Agena being produced to a generic configuration and custom-modified also applied to Atlas pre SLV-3 (that is to say purchasing an Atlas D core and modifying it for the particular mission), and this was one reason for the endless reliability issues with them. While Atlas could be reduced to one configuration, this wasn't as doable on Agena due to mission requirements. Still, the improvements to hardware and testing helped a great deal.

The NASA planetary probes I would guess had the most "vanilla" Agena configuration since they wouldn't have to do anything other than put the payload into a parking orbit and restart once for IPT injection. NASA apparently also had enough stockpiled Agena Bs that they kept flying them into 1966 (OGO 3 was the last one), but Agena was the Air Force's bird and they likely got priority on orders for the newer Agena D.
« Last Edit: 04/10/2017 07:06 PM by WallE »

Offline Archibald

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Re: On-Pad Explosions
« Reply #63 on: 04/10/2017 06:15 PM »
I think that a few years ago Joel Powell did an article on Atlas pad crumples. Not all of them went boom. In fact, I think he was more interested in the ones that crumpled but did not explode, because they were not recorded regularly.

Atlas 190D famously crumpled on SLC-4W May 11, 1963 and was recorded on camera, we've all seen than one. The booster intended to launch Mariner 6 also crumpled, but its collapse was averted by two quick-thinking technicians. Atlas collapses also happened a couple of times at operational silo facilities.

The Mercury astronauts were in a high risk profession; John Glenn flew when the Atlas was batting .500. Atlas 52D blew up during an operational test from the West Coast only about 24 hours after Glenn's launch. When Gordon Cooper flew at the end of the Mercury program, things didn't get much better; there were four Atlas failures in the first three months of 1963, three of which were D-series (ie. a potential direct problem for Mercury).



The red-button launch man face at 1:29 speaks volume :)
« Last Edit: 04/10/2017 06:16 PM by Archibald »

Offline WallE

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Re: On-Pad Explosions
« Reply #64 on: 04/10/2017 07:28 PM »
They also had different paint jobs on the Agena A/B which seem to indicate the launch location (applying of course to Atlas-Agena since Thor and Titan Agenas were never flown from CC). West Coast Agenas had two dots inside a rectangle while East Coast Agenas had roll bars. Samos 1's Agena was all-white, but they probably hadn't come up with a paint scheme yet. The Agena D did away with this, all of them had a checkerboard pattern.

Offline Jim

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Re: On-Pad Explosions
« Reply #65 on: 04/10/2017 07:31 PM »

The Atlas SLV-3 and Agena D had emerged out of Lewis's proposal for a standardized Atlas-Agena.

That had nothing to do with Lewis, NASA did not have any contracts for Atlas or Agena.  It got them through the USAF.  They were separate projects.    Agena-D was a Lockheed internal initiative. Standardized launch vehicles was an Air Force initiative and covered Titan, Thor and Atlas projects.
« Last Edit: 04/10/2017 07:49 PM by Jim »

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Re: On-Pad Explosions
« Reply #66 on: 04/10/2017 07:37 PM »
They also had different paint jobs on the Agena A/B which seem to indicate the launch location

It was driven by mission thermal requirements, which is a function of orbital requirements which drove launch location. 
Hence a bus mission like GAMBIT is going to have a different thermal environment (long term and day/night cycle) vs an ascent mission like Ranger (short duration, sun vs shadow different for each mission)

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Re: On-Pad Explosions
« Reply #67 on: 04/10/2017 07:58 PM »
That had nothing to do with Lewis, it was an Air Force initiative.  NASA did not have any contracts for Atlas or Agena.  It got them through the USAF.

First they had a board of inquiry (the Kelley Board) after the failure of Ranger 5 which declared that neither the LVs or the probes had good enough reliability or quality for the needs of the program, then later on Lewis got the job of fixing it (actually a side assignment along with their main task of getting Atlas-Centaur up and running) and they were the guys who recommended standardizing the hardware and implementing better quality control.

One of the Kelley Board's proposals involved removing the Air Force from an active role in NASA missions, so the latter would be completely in charge of purchasing launch vehicles and writing mission reports. This meant that by 1963, NASA could purchase Atlas-Agena vehicles without Air Force interference. The fact that NASA failures happened in the public eye unlike the numerous secretive Air Force failures probably helped motivate improvements since it didn't look too good to have $14 million of taxpayer money go into the Atlantic Ocean.

And no, it wasn't an Air Force initiative. The Kelley Board was a NASA initiative although they did have to get the Air Force's cooperation as they were the official "owner" of Atlas-Agena. Details are all in "A History of Project Ranger" for anyone who wants to read them.

Standardizing the LVs was probably inevitable anyway once the Atlas ICBM program came to an end. In fact the Soviets did same with the R-7 family; once they retired it from missile service, they came up with one standard configuration instead of the numerous variants flying prior to 1966.
« Last Edit: 04/10/2017 08:19 PM by WallE »

Offline WallE

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Re: On-Pad Explosions
« Reply #68 on: 04/10/2017 08:06 PM »
Hence a bus mission like GAMBIT is going to have a different thermal environment (long term and day/night cycle) vs an ascent mission like Ranger (short duration, sun vs shadow different for each mission)

But at the same time, not all Agenas were bus missions. For example, some Samos satellites separated from the Agena and only used it for the boost phase, while others used it as a bus, yet they seem to have all had the same paint pattern. Also all Agena Ds had the same checkerboard-over-black paint pattern regardless of the mission and the launch site. However, they might have standardized on this scheme because most Agena Ds were used for Corona/Gambit and there was no reason to alter it for the small number of times NASA flew them (just a hunch of mine).

Edit: I just checked and Midas 2's booster did have a paint pattern closer to that of VAFB Agenas, but also sporting the Thor-Agena checkerboard on white. (Midas 1 had the roll bars). All Air Force Atlas-Agena A/Bs from Samos 2 onward seem to have had the two black dots on white inside a black rectangle.
« Last Edit: 04/10/2017 09:11 PM by WallE »

Offline Jim

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Re: On-Pad Explosions
« Reply #69 on: 04/11/2017 12:18 AM »

And no, it wasn't an Air Force initiative. The Kelley Board was a NASA initiative although they did have to get the Air Force's cooperation as they were the official "owner" of Atlas-Agena. Details are all in "A History of Project Ranger" for anyone who wants to read them.

Wrong.  It was an Air Force initiative
a.  A NASA book is not an authoritative source for Air Force run programs Atlas and Agena
b.  Ranger had little impact to the larger user of Atlas and Agena.
c.  The standard Atlas (SLV-3) was not used for Ranger and flew before the last Ranger.
d.  What was "standardized" was the specific launch vehicle configuration assigned for Ranger and not a fleet wide " standardized Atlas-Agena".
« Last Edit: 04/11/2017 12:24 AM by Jim »

Offline Jim

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Re: On-Pad Explosions
« Reply #70 on: 04/11/2017 12:22 AM »

1.  But at the same time, not all Agenas were bus missions. For example, some Samos satellites separated from the Agena and only used it for the boost phase, while others used it as a bus, yet they seem to have all had the same paint pattern.

2. Edit: I just checked and Midas 2's booster did have a paint pattern closer to that of VAFB Agenas, but also sporting the Thor-Agena checkerboard on white. (Midas 1 had the roll bars). All Air Force Atlas-Agena A/Bs from Samos 2 onward seem to have had the two black dots on white inside a black rectangle.

1.  No, SAMOS were all bus missions. 

2.  the black dots were likely antennas, unique to the west coast.
Despite the standardization of the SLV-3, there were still launch site specific differences
« Last Edit: 04/11/2017 12:27 AM by Jim »

Offline WallE

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Re: On-Pad Explosions
« Reply #71 on: 04/11/2017 01:51 AM »

1.  No, SAMOS were all bus missions.

Ok fair enough. Some of the sources I was using seem to be outdated and predate declassifications. The artist's rendering here does show a Samos still attached to the Agena.


2.  the black dots were likely antennas, unique to the west coast. Despite the standardization of the SLV-3, there were still launch site specific differences.

Guidance systems would definitely be different for CCAS and VAFB. There could also have been differences to accommodate the launcher/ground support equipment at both sites.

As for the other point about Ranger not using the Atlas SLV-3/Agena D, the Air Force got priority which resulted in NASA flying Agena Bs for a good two years after DoD launches stopped using them (although Mariner 3/4 used the Agena D). NASA wouldn't have even used Agena at all if they'd had the choice, but Centaur took almost half a decade to become operational.

Offline Jim

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Re: On-Pad Explosions
« Reply #72 on: 04/11/2017 02:02 AM »

Standardizing the LVs was probably inevitable anyway once the Atlas ICBM program came to an end.

It was in work before the end of the program

Offline Jim

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Re: On-Pad Explosions
« Reply #73 on: 04/11/2017 02:05 AM »

As for the other point about Ranger not using the Atlas SLV-3/Agena D, the Air Force got priority which resulted in NASA flying Agena Bs for a good two years after DoD launches stopped using them (although Mariner 3/4 used the Agena D). NASA wouldn't have even used Agena at all if they'd had the choice, but Centaur took almost half a decade to become operational.

Wrong.  You can't have it both ways.  You can't say NASA was for standardizing on the Ranger missions and then say the reason for Agena B was AF priority.  The use of Agena D for Mariner 3/4 is just one of many points against your case. 
« Last Edit: 04/11/2017 02:14 AM by Jim »

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Re: On-Pad Explosions
« Reply #74 on: 04/11/2017 02:16 AM »

Ok fair enough. Some of the sources I was using seem to be outdated and predate declassifications. The artist's rendering here does show a Samos still attached to the Agena.


None of the early sources had it separate from the Agena.  Both SAMOS and Discoverer were bus missions from day 1.

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Re: On-Pad Explosions
« Reply #75 on: 04/11/2017 02:29 AM »
Wrong.  You can't have it both ways.  You can't say NASA was for standardizing on the Ranger missions and then say the reason for Agena B was AF priority.  The use of Agena D for Mariner 3/4 is just one of many points against your case.

What I meant was the Air Force got priority which prevented switching Ranger to them so NASA had to continue using the older Agena Bs that they'd already accumulated. NASA also had budget constraints which did not affect the practically limitless funds available for high priority DoD missions. Now, it's possible that Lockheed were able to fill two orders for Agena Ds to launch Mariner, but all other ones they had were earmarked for Air Force use.

I doesn't seem logical that they'd continue flying Ranger on the older and less reliable booster models if they'd had the choice. The Air Force didn't use Agena B one second longer than they had to, because they could get the latest and best hardware ahead of NASA. As proof of this, NASA originally intended to use leftover Atlases from cancelled Mercury missions to launch GATVs, but the Gemini program ended up getting enough funds that they scrapped that idea and just bought all-new SLV-3s.

Offline Jim

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Re: On-Pad Explosions
« Reply #76 on: 04/11/2017 02:51 AM »

1.  What I meant was the Air Force got priority which prevented switching Ranger to them so NASA had to continue using the older Agena Bs that they'd already accumulated. NASA also had budget constraints which did not affect the practically limitless funds available for high priority DoD missions. Now, it's possible that Lockheed were able to fill two orders for Agena Ds to launch Mariner, but all other ones they had were earmarked for Air Force use.

2.  I doesn't seem logical that they'd continue flying Ranger on the older and less reliable booster models if they'd had the choice.

3.  The Air Force didn't use Agena B one second longer than they had to, because they could get the latest and best hardware ahead of NASA. As proof of this, NASA originally intended to use leftover Atlases from cancelled Mercury missions to launch GATVs, but the Gemini program ended up getting enough funds that they scrapped that idea and just bought all-new SLV-3s.

1.  Wrong.  The only NASA users of Agena B after the introduction of the D model was Ranger and OGO.  Mariner, GATV, OAO-1 used the D.  The AF still used B for MIDAD

2.  Yes it does. 
a.  If they already bought them
b.  The standardization thing

3.   Midas used B after the introduction of the D.  The D introduction coincided with GAMBIT.  Your claim is not proof.  And there were no real "leftover" Atlas D's from Mercury.  They were quickly reassigned


Offline WallE

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Re: On-Pad Explosions
« Reply #77 on: 04/11/2017 03:17 AM »
1.  Wrong.  The only NASA users of Agena B after the introduction of the D model was Ranger and OGO.  Mariner, GATV, OAO-1 used the D.  The AF still used B for MIDAS

Yes as I said, they probably had leftover Agena Bs and possibly lacked the money/scheduling to buy Ds. The statement about MIDAS definitely isn't correct because the last of the original MIDAS series flew in July 1963 one week after GAMBIT made its maiden launch, so MIDAS was ending just as GAMBIT was beginning. There was a second group of MIDASes flown in 1966, but of course those used the SLV-3/Agena D.

And apparently, Agena Ds were a necessity for Mariner 3/4 due to their larger mass, the Bs weren't enough.

a.  If they already bought them

I had addressed that. NASA had limited funds therefore this is an entirely plausible reason. In fact they were getting their budget clipped by Congress because Ranger wasn't producing any successful missions.

And there were no real "leftover" Atlas D's from Mercury.  They were quickly reassigned

The leftover Mercury-Atlases at program cancellation in June 1963 were 144D, 152D, and 167D, and these don't seem to have been reassigned to anything. I believe 144D was completed by that time (it would have launched Alan Shepard on an orbital flight later in the year) but the other two were probably still under construction. Most likely they were just scrapped  Way earlier in the program, they were going to use Atlas 77D for MA-3, which was completed and even received a factory rollout, but the postflight findings from MA-1 led to it being recalled and replaced by 100D. No idea what became of 77D either, probably scrapped.
« Last Edit: 04/11/2017 03:29 AM by WallE »

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Re: On-Pad Explosions
« Reply #78 on: 04/11/2017 02:54 PM »
Yes as I said, they probably had leftover Agena Bs and possibly lacked the money/scheduling to buy Ds. The statement about MIDAS definitely isn't correct because the last of the original MIDAS series flew in July 1963 one week after GAMBIT made its maiden launch, so MIDAS was ending just as GAMBIT was beginning. There was a second group of MIDASes flown in 1966, but of course those used the SLV-3/Agena D.


Again, no such thing as "leftover" Agenas, they were built for specific spacecraft.   The statement about MIDAS is 100% correct.  Production of B & D were concurrent. 

Offline edkyle99

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Re: On-Pad Explosions
« Reply #79 on: 04/11/2017 03:46 PM »
They also had different paint jobs on the Agena A/B which seem to indicate the launch location (applying of course to Atlas-Agena since Thor and Titan Agenas were never flown from CC). West Coast Agenas had two dots inside a rectangle while East Coast Agenas had roll bars. Samos 1's Agena was all-white, but they probably hadn't come up with a paint scheme yet. The Agena D did away with this, all of them had a checkerboard pattern.
Note that the roll bars, checkerboards, and such that you are mentioning were on the adapter (interstage) rather than on Agena itself, at least for the B and D variants.

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Re: On-Pad Explosions
« Reply #80 on: 04/11/2017 08:46 PM »
Returning this thread to the original topic, here's an obscure one--Scout X-3A launched from Wallops Island's LA-3 on July 20, 1963 for a test of ablative heat shield material. The first stage nozzle burned through 2.5 seconds after liftoff and the Scout got to a height of about 300 feet before it spun out of control and disintegrated. The first and second stages flew off in random directions while the third and fourth stages fell back on the pad and burned. LA-3 was badly damaged by the incident, which was traced to deficient manufacturing practices on the first stage. Scout launches were suspended for two months until the existing stockpile of them could be checked for defects. The next launch on September 27 also failed, but not on or around the pad.
« Last Edit: 04/11/2017 09:26 PM by WallE »

Offline ZachS09

Re: On-Pad Explosions
« Reply #81 on: 04/11/2017 11:02 PM »
Although most of the on-pad explosions previously covered in this thread were solely American rocket failures, I have a different example you might recognize:

On October 15, 2002 at 18:20 UTC (9:20 PM local), a Soyuz-U rocket took off from Site 43/3 at Plesetsk Cosmodrome, carrying the Foton M-1 spacecraft. This mission's payload involved the European Space Agency, so some ESA officials were watching the night launch from a close viewing point. 8 seconds after launch, foreign debris was accidentally ingested into one of the boosters' turbopumps. That booster stripped off the core stage at T+20 seconds and impacted the pad area. When the stricken booster separated, an automatic shutdown command was given to the remaining engines. The highest the Soyuz reached was 200 meters, or 656 feet. The launch pad itself was not totally destroyed by the explosion; it was a partial destruction since the rest of the launch vehicle impacted an area not too far from the pad. Only one person was killed in the explosion: a 20-year-old Russian soldier who was observing the launch from, in my humble opinion, a closer viewing point than ESA was given.



Sources:

https://www.newscientist.com/article/dn2931-soyuz-rocket-explodes-killing-one/
https://web.archive.org/web/20021226120038/http://www.spaceandtech.com/digest/flash2002/flash2002-082.shtml
« Last Edit: 04/11/2017 11:13 PM by ZachS09 »
"Falcon 9 has landed. Landing operators, move into Procedure 11.100 on Recovery Net."

Offline WallE

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Re: On-Pad Explosions
« Reply #82 on: 04/12/2017 01:35 AM »
On October 15, 2002 at 18:20 UTC (9:20 PM local), a Soyuz-U rocket took off from Site 43/3 at Plesetsk Cosmodrome, carrying the Foton M-1 spacecraft. This mission's payload involved the European Space Agency, so some ESA officials were watching the night launch from a close viewing point. 8 seconds after launch, foreign debris was accidentally ingested into one of the boosters' turbopumps. That booster stripped off the core stage at T+20 seconds and impacted the pad area. When the stricken booster separated, an automatic shutdown command was given to the remaining engines. The highest the Soyuz reached was 200 meters, or 656 feet. The launch pad itself was not totally destroyed by the explosion; it was a partial destruction since the rest of the launch vehicle impacted an area not too far from the pad. Only one person was killed in the explosion: a 20-year-old Russian soldier who was observing the launch from, in my humble opinion, a closer viewing point than ESA was given.

To date, this is the only R-7 failure in the first two minutes of launch in the post-Soviet era (the Yantar failures in '96 don't count because they were malfunctions of the payload shroud, not the LV).

Three Plesetsk R-7 launches during the '80s failed in very similar fashion to Foton. The first of these was a Zenit satellite launch in 1982 where a defective PCB shut down the core stage shortly after liftoff, resulting in impact near LC-41. No significant damage seems to have resulted since an Oko early warning satellite was launched from the same pad only five days later. The second was a Resurs launch in 1987 when one strap-on suffered a turbopump failure seconds after liftoff. LC-43/3 was not used again for 18 months. In 1988, another Resurs from the adjacent LC-43/4 suffered a core stage failure. The pad was not used again for 11 months.
« Last Edit: 04/12/2017 04:21 AM by WallE »

Offline ZachS09

Re: On-Pad Explosions
« Reply #83 on: 04/12/2017 03:34 AM »
I actually did not know about this extra R-7 info until now. Thanks, WallE.
"Falcon 9 has landed. Landing operators, move into Procedure 11.100 on Recovery Net."

Offline JAFO

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Re: On-Pad Explosions
« Reply #84 on: 04/12/2017 03:51 AM »
There's a B&W video of an old Soviet rocket launching, suffering a total engine failure, then falling back into the pad area. Seems every time I find it, it gets removed a short time later. Always wondered about that launch.
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Offline ZachS09

Re: On-Pad Explosions
« Reply #85 on: 04/12/2017 03:59 AM »
There's a B&W video of an old Soviet rocket launching, suffering a total engine failure, then falling back into the pad area. Seems every time I find it, it gets removed a short time later. Always wondered about that launch.

When you saw this one video, did you see the strap-on boosters stripping off moments before impact?
"Falcon 9 has landed. Landing operators, move into Procedure 11.100 on Recovery Net."

Offline WallE

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Re: On-Pad Explosions
« Reply #86 on: 04/12/2017 04:14 AM »
When you saw this one video, did you see the strap-on boosters stripping off moments before impact?

If so, that would be the 1982 Zenit accident. An old thread here from a couple years ago had identified that video clip as the '82 failure. Otherwise the April 2, 1969 Proton accident is a possibility.

In the case of the '88 accident, the core stage engines malfunctioned almost immediately at liftoff, but the booster computer system was blocked from sending a shutoff command until T+20 seconds so as to prevent a pad fallback. When the 20 second mark was reached, the command was unblocked and the core and strap-ons shut down. This turned out to not be enough time to get the booster away from the pad, which was severely damaged. According to a translated document I read, it seems like the core stage suffered a control rather than a propulsion system failure.

The same document also noted that the '87 accident would not have been survivable on a manned launch, and apparently necessitated improvements to the Soyuz SAS abort system (at least that's what I could discern from the translated text).
« Last Edit: 04/12/2017 04:19 AM by WallE »

Offline ZachS09

Re: On-Pad Explosions
« Reply #87 on: 04/12/2017 04:56 AM »
Because the Foton M-1 failure was technically not an on-pad explosion since it was hit by only one booster, here's a simulation of what it would look like if all went wrong at engine ignition. Orbiter 2010 is used.

"Falcon 9 has landed. Landing operators, move into Procedure 11.100 on Recovery Net."

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #88 on: 04/12/2017 06:12 AM »
When you saw this one video, did you see the strap-on boosters stripping off moments before impact?

If so, that would be the 1982 Zenit accident. An old thread here from a couple years ago had identified that video clip as the '82 failure. Otherwise the April 2, 1969 Proton accident is a possibility.

In the case of the '88 accident, the core stage engines malfunctioned almost immediately at liftoff, but the booster computer system was blocked from sending a shutoff command until T+20 seconds so as to prevent a pad fallback. When the 20 second mark was reached, the command was unblocked and the core and strap-ons shut down. This turned out to not be enough time to get the booster away from the pad, which was severely damaged. According to a translated document I read, it seems like the core stage suffered a control rather than a propulsion system failure.

The same document also noted that the '87 accident would not have been survivable on a manned launch, and apparently necessitated improvements to the Soyuz SAS abort system (at least that's what I could discern from the translated text).
Video clip from the launch failure on 15.05.1982
http://www.kosmonavtika.com/lancements/1982/15051982/15051982photos.html

Online The_Ronin

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Re: On-Pad Explosions
« Reply #89 on: 04/12/2017 03:24 PM »
Wow.  I'm surprised how it remained mostly intact all the way down.  That was surreal.

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #90 on: 04/12/2017 05:38 PM »
Wow.  I'm surprised how it remained mostly intact all the way down.  That was surreal.
Emergency shutdown T+28,26 (sec)

Offline WallE

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Re: On-Pad Explosions
« Reply #91 on: 04/13/2017 04:56 AM »
Emergency shutdown T+28,26 (sec)

Not quite. According to a translated Russian site I'd check out, the core stage shut down at T+28 seconds due to "the formation of false commands due to the ingress of extraneous metal particles in the cam mechanism of the program time device of the control system". Meaning the shutoff was unintentional and not deliberately commanded.

I believe the video clip linked here is in fact the 1988 failure, not the '82 one because the entire propulsion system shuts down, not just the core stage. We also don't have a list of Baikonur R-7 failures, so some of them remain a mystery and there could have been more crashes in the pad area for all anyone knows.
« Last Edit: 04/13/2017 05:05 AM by WallE »

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #92 on: 04/13/2017 06:20 AM »
A real on-pad explosion (Nicolas' website)
http://www.kosmonavtika.com/lancements/1990/04101990/04101990photos.html
4.10.1990 pad 45/2 destroyed and never rebuilt

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #93 on: 04/13/2017 01:26 PM »
Emergency shutdown T+28,26 (sec)

I believe the video clip linked here is in fact the 1988 failure, not the '82 one because the entire propulsion system shuts down, not just the core stage.
27.07.1988 launch took place 09:05:00 (12:05:00 Moscow time)
the video clip shows darkness (?)

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #94 on: 04/13/2017 02:10 PM »
launch failures (on-pad or near the pad)
possibly not completely
16.04.1960 (Luna)     exploded near the pad
01.06.1962 Zenit 2    emergency shutdown T+1,8 sec /fell down 300m next to pad
10.07.1963 Zenit 2    emergency shutdown T-1,5 sec /exploded / pad damaged - next launch 10/63
18.03.1980 Tselina    exploding when refueling / next launch April 1983 ! (43/4)
15.05.1982 Zenit 6U  failed T+28.26 crashed in the forest                       (41/1)
26.09.1983 Sojus (T10) fire/exploded / next launch 11.06.1984               (1/5)
18.06.1987 Resurs    ex/pad damaged/next launch 12/88                      (43/3)
27.07.1988 Resurs    fell down 50 m near the pad/pad damaged/ next launch 6/89 (43/4)
04.10.1990 Tselina 2  ex T+2,44 sec                                                     (45/2)

30.01.2007 NSS 8     ex shortly after liftoff                                            (Odyssey)
« Last Edit: 04/13/2017 03:23 PM by Alter Sachse »

Offline kevin-rf

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Re: On-Pad Explosions
« Reply #95 on: 04/13/2017 04:09 PM »
Was Intelsat 27 to far from the pad to count?
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Offline B. Hendrickx

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Re: On-Pad Explosions
« Reply #96 on: 04/13/2017 04:12 PM »
At least one other I can add is the explosion of a Soyuz rocket carrying the second unmanned Soyuz vehicle on 14 December 1966 (Baikonur - Site 31).

Anatoly Zak recently summarized what is known about this accident :

http://www.russianspaceweb.com/soyuz-7k-ok-no1-explosion.html

Offline WallE

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Re: On-Pad Explosions
« Reply #97 on: 04/13/2017 04:16 PM »
launch failures (on-pad or near the pad)
possibly not completely
16.04.1960 (Luna)     exploded near the pad
01.06.1962 Zenit 2    emergency shutdown T+1,8 sec /fell down 300m next to pad
10.07.1963 Zenit 2    emergency shutdown T-1,5 sec /exploded / pad damaged - next launch 10/63
18.03.1980 Tselina    exploding when refueling / next launch April 1983 ! (43/4)
15.05.1982 Zenit 6U  failed T+28.26 crashed in the forest                       (41/1)
26.09.1983 Sojus (T10) fire/exploded / next launch 11.06.1984               (1/5)
18.06.1987 Resurs    ex/pad damaged/next launch 12/88                      (43/3)
27.07.1988 Resurs    fell down 50 m near the pad/pad damaged/ next launch 6/89 (43/4)
04.10.1990 Tselina 2  ex T+2,44 sec                                                     (45/2)

30.01.2007 NSS 8     ex shortly after liftoff                                            (Odyssey)

An R-7 ICBM test on July 10, 1958 failed when one strap-on shut down at liftoff and broke away from the stack. The strap-on fell onto the pad while the rest of the vehicle crashed nearby. According to some sources, it carried some of the avionics intended for the Luna 8K72 booster, and the failure was caused by high frequency combustion chamber vibration which would end up being a nagging problem over the next two years.

The two Zenit failures in 1962-63 were caused by the strap-ons shutting down at liftoff, and the first one delayed Vostok 3's launch by a month. They were eventually found to be liftoff-induced vibration accidentally flipping a power switch designed to cut electrical power to the strap-ons at staging.

Two Kosmos 11K65Ms blew on the pad. The first happened on December 22, 1970 when the first stage engine cut off a few seconds after liftoff. The other was on June 26, 1973 during an aborted launch attempt. A fire started while attempting to drain the propellant from the booster, which exploded and killed nine people. The culprit turned out to be high frequency combustion instability in the RD-216 engine, but it took an entire decade and two more first stage failures before the engine was redesigned.

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #98 on: 04/13/2017 04:17 PM »
Was Intelsat 27 to far from the pad to count?
I have a note: 3 km south of the launch pad

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #99 on: 04/13/2017 04:51 PM »
To the last posts
Some forgotten:
14.12 1966 yes!
10.07.1958 I did not know any details
22.12.1970 yes!
26.06.1973 yes!

Offline WallE

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Re: On-Pad Explosions
« Reply #100 on: 04/13/2017 05:28 PM »
A launch of a Zenit satellite from Plesetsk's LC-43/4 on December 3, 1971 failed when the core stage ingested loose debris and shut down almost immediately at liftoff. The booster continued to climb for about 20-30 seconds before breaking up, and according to a translated account of the launch, the weather that day was overcast with thick clouds, so it was soon out of visibility. One strap-on fell out of the clouds (literally) and impacted near the pad. The rest of the booster crashed a few miles away. The next launch from LC-43/4 took place three weeks later, so no serious damage occurred.

Offline Jim

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Re: On-Pad Explosions
« Reply #101 on: 04/13/2017 07:29 PM »

An R-7 ICBM test on July 10, 1958 failed when one strap-on shut down at liftoff and broke away from the stack. The strap-on fell onto the pad while the rest of the vehicle crashed nearby. According to some sources, it carried some of the avionics intended for the Luna 8K72 booster, and the failure was caused by high frequency combustion chamber vibration which would end up being a nagging problem over the next two years.


Are you going to cite your sources or just blatantly cut and paste from wikipedia and bypassing its sources?

Offline WallE

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Re: On-Pad Explosions
« Reply #102 on: 04/13/2017 08:42 PM »
Are you going to cite your sources or just blatantly cut and paste from wikipedia and bypassing its sources?

If you wanted that list of Plesetsk R-7 failures, it's right here.

http://forum.nasaspaceflight.com/index.php?topic=17286.235

Offline JAFO

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Re: On-Pad Explosions
« Reply #103 on: 04/13/2017 09:54 PM »
When you saw this one video, did you see the strap-on boosters stripping off moments before impact?

If so, that would be the 1982 Zenit accident. An old thread here from a couple years ago had identified that video clip as the '82 failure. Otherwise the April 2, 1969 Proton accident is a possibility.

In the case of the '88 accident, the core stage engines malfunctioned almost immediately at liftoff, but the booster computer system was blocked from sending a shutoff command until T+20 seconds so as to prevent a pad fallback. When the 20 second mark was reached, the command was unblocked and the core and strap-ons shut down. This turned out to not be enough time to get the booster away from the pad, which was severely damaged. According to a translated document I read, it seems like the core stage suffered a control rather than a propulsion system failure.

The same document also noted that the '87 accident would not have been survivable on a manned launch, and apparently necessitated improvements to the Soyuz SAS abort system (at least that's what I could discern from the translated text).
Video clip from the launch failure on 15.05.1982
http://www.kosmonavtika.com/lancements/1982/15051982/15051982photos.html

That's the one.

-Wonder what the uphill velocity was when the engines cut out was vs the downhill velocity at impact?

-Must of been scary as heck to be near the pad and see the rocket suspended in mid-air, juuuuuust before it started down.
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Offline WallE

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Re: On-Pad Explosions
« Reply #104 on: 04/14/2017 12:14 AM »
http://kik-sssr.ru/IP_4_Turatam_old_Razdel_1.htm

This site (use Google Translate) also has some nice bits of info about various R-7 failures. I had intended to post the link earlier but forgot.

http://cosmopark.ru/r7/prig8.htm

This one describes the 1962-63 Zenit accidents and the cause of them.
« Last Edit: 04/14/2017 12:21 AM by WallE »

Offline WallE

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Re: On-Pad Explosions
« Reply #105 on: 04/14/2017 03:54 AM »
A real on-pad explosion (Nicolas' website) http://www.kosmonavtika.com/lancements/1990/04101990/04101990photos.html
4.10.1990 pad 45/2 destroyed and never rebuilt

The Zenit booster got off to a bit of a rough start since the RD-171 engine was new technology and understandably had teething problems, however, it was the only survivor out of an ambitious series of next-generation Soviet LVs and manned spacecraft planned for the 1980s and beyond. Under original plans, it would have launched Zarya, the intended successor to Soyuz.

That 1990 disaster is easily one of the top ten rocket crashes of all time and the total devastation of the pad was largely due to a poor design that resulted in the blast wave having nowhere to disperse. If I remember correctly (and I could be wrong about this), there was only a small flame trench under the launch stand as opposed to the giant flame pit on R-7 pads.

Offline Alter Sachse

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Re: On-Pad Explosions
« Reply #106 on: 04/14/2017 04:09 PM »
http://kik-sssr.ru/IP_4_Turatam_old_Razdel_1.htm

3.12.1971:Block A failed T+0.5
rocket continued the flight and crashed at the village Karasye (7...8 km north of launch complex 43)

Offline WallE

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Re: On-Pad Explosions
« Reply #107 on: 04/24/2017 01:42 AM »
I think that a few years ago Joel Powell did an article on Atlas pad crumples. Not all of them went boom. In fact, I think he was more interested in the ones that crumpled but did not explode, because they were not recorded regularly.

Another such failure mode was Atlas bulkhead reversals. If the pressure levels in the propellant tanks got too high or too low, the bulkhead separating the propellant tanks would reverse/rupture/collapse, causing all of the LOX and RP-1 to mix, turn to gel, and explode instantaneously like a giant stick of dynamite.

This happened on Atlas 5C, 7D, 5D, and 81D. The first three resulted from loss of RP-1 tank pressure, the second two from overpressurization of the LOX tank. If you'd seen the video of 7D, the explosion happens really fast, almost instantaneously while on, say, Atlas Centaur AC-1, there's a much slower moving fireball with very little propellant mixing.

Kerolox has this unfortunate property not experienced with other propellant combinations. Hypergols burn on contact, reducing their explosive potential, while hydrolox, in the absence of an ignition source, will merely turn into water vapor if it mixes.
« Last Edit: 06/21/2017 12:11 PM by WallE »

Offline Jim

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Re: On-Pad Explosions
« Reply #108 on: 04/24/2017 02:50 PM »
Kerolox has this unfortunate property not experienced with other propellant combinations. Hypergols burn on contact, reducing their explosive potential, while hydrolox, in the absence of an ignition source, will merely turn into water vapor if it mixes.

Wrong, Kerolox and hydrolox have the same issue. 

if there is no ignition, then hydrolox remain H2 and O2.  Kerolox also requires an ignition source  and would remain O2 and RP-1 without one.  hydrolox has more flammability and lower ignition energy.

Offline WallE

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Re: On-Pad Explosions
« Reply #109 on: 04/25/2017 02:23 AM »
Kerolox also requires an ignition source  and would remain O2 and RP-1

Alright, that part is correct. LOX and LH2 should turn into gel when mixed because LOX will do that when it's mixed with any flammable liquid. Most importantly, it turns into a shock-sensitive gel. An ignition source isn't required to set it off, you just have to bump/strike/hit it.

In the absence of an ignition source, then no, the propellants shouldn't go off if they're not mixed. The Atlas 190D/GAMBIT pad crumple didn't result in a fire or explosion because they'd removed the LOX when the mishap occurred, so the RP-1 just spilled onto the launch stand. If the LOX had still been present... kaboom. It was mentioned earlier in this thread that Thor on-pad explosions were less destructive on average than Atlas ones because of the separate tanks that reduced the chance for the propellants to inertially mix.

Hypergols aren't as explosive simply because they burn on contact and can't mix first. This was a factor in the decision to not use an escape tower on Gemini--they reasoned that a Titan II couldn't explode with as much force as an Atlas or a Saturn.
« Last Edit: 04/25/2017 08:53 AM by WallE »

Offline Jim

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Re: On-Pad Explosions
« Reply #110 on: 04/25/2017 04:15 PM »

Alright, that part is correct. LOX and LH2 should turn into gel when mixed because LOX will do that when it's mixed with any flammable liquid. Most importantly, it turns into a shock-sensitive gel. An ignition source isn't required to set it off, you just have to bump/strike/hit it.


Wrong again.  The warmer LOX would make the LH2 turn into a gas.  There would be no gel.

Offline Jim

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Re: On-Pad Explosions
« Reply #111 on: 04/25/2017 04:16 PM »
If the LOX had still been present... kaboom.

Not true either.

Offline WallE

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Re: On-Pad Explosions
« Reply #112 on: 04/26/2017 03:27 AM »
Not true either.

It doesn't take much imagination to assume that an Atlas splitting open on the launch stand and releasing thousands of gallons of RP-1 and LOX won't result in at least some mixing of the propellants.

Take Atlas 71F. A little kerolox glob in the flame pit exploded and damaged the booster, resulting in eventual engine shutdown and loss of the mission. Now take a guess what an entire load of propellant can do.

Offline Stan-1967

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Re: On-Pad Explosions
« Reply #113 on: 04/26/2017 04:07 AM »
Kerolox has this unfortunate property not experienced with other propellant combinations. Hypergols burn on contact, reducing their explosive potential, while hydrolox, in the absence of an ignition source, will merely turn into water vapor if it mixes.

Wrong, Kerolox and hydrolox have the same issue. 

if there is no ignition, then hydrolox remain H2 and O2.  Kerolox also requires an ignition source  and would remain O2 and RP-1 without one.  hydrolox has more flammability and lower ignition energy.

Are there any examples of pad failures where hydrolox or LOX + any hydrocarbon mixed together on the pad environment and failed to explode?   I'm recalling from some thread here on NSF the rocket scientist maxim that "ignition is free" when it comes to investigating explosion failures.

I can't think of any off the top of my head.  I recall various leaks of monoprops & hypergols making a mess on the pad, but not exploding.  I'm also not counting the buildup of gaseous hydrogen on the STS pad that was handled with the burnoff system prior to main engine ignition.

Offline WallE

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Re: On-Pad Explosions
« Reply #114 on: 04/26/2017 04:51 AM »
Are there any examples of pad failures where hydrolox or LOX + any hydrocarbon mixed together on the pad environment and failed to explode?   I'm recalling from some thread here on NSF the rocket scientist maxim that "ignition is free" when it comes to investigating explosion failures.

http://www.healthsafety.com/articles/man-lox-warning-video-contains-graphic-content

"LOX or liquid oxygen is not flammable on its own; however once you combine it with a flammable item, it can have explosive results. The boil off, or fog of oxygen that is produced can create oxygen enriched environments increasing the danger of fires and explosions. LOX has an expansion ratio of 1:861, meaning that one liter of liquid oxygen will expand to 861 liters of gaseous oxygen. LOX is considered a cryogenic compound, meaning that it instantly freezes biological material, like your skin, on contact. When LOX encounters petroleum based products, it can react violently causing explosions and fires. There have been reports of alcohol based hand sanitizers catching fire in oxygen-enriched environments at hospitals."

Jim is correct in his statement that LOX mixing with LH2 doesn't gel (still highly explosive). RP-1 sure is petroleum-based though, which is why it seems silly to think that an Atlas rupturing and dumping all of its propellants on the pad would not result in some very bad things happening.

Aside from Atlas 71F, the first Atlas D launch (Missile 3D) had a failure of the propellant fill and drain valves, causing the propellants to spill out and explode on the pad. It flew for 27 seconds until the booster section exploded and Range Safety blew it up, but as I understand, this was caused by unstable B-2 engine combustion due to the loss of LOX rather than the incident at liftoff.

I can't think of any off the top of my head.  I recall various leaks of monoprops & hypergols making a mess on the pad, but not exploding.  I'm also not counting the buildup of gaseous hydrogen on the STS pad that was handled with the burnoff system prior to main engine ignition.

When they were preparing Challenger for its first launch in early 1983, several leaks of liquid hydrogen ducting were discovered, which resulted in the SSMEs being removed and replaced. However, no fire or explosion resulted.

The attempted launch of Discovery in June 1984 failed because of a stuck SSME main fuel valve preventing the flow of LOX to the #3 engine. Liquid hydrogen pooled around the base of the thrust section and started a fire, but the water deluge system put it out. If the astronauts had tried to evacuate using the slidewire escape system, they would have plunged right into the invisible LH2 fire.
« Last Edit: 04/26/2017 08:06 AM by WallE »

Offline WallE

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Re: On-Pad Explosions
« Reply #115 on: 04/28/2017 04:51 PM »
Since we were on the topic of propellant mixing, Atlas 9C was particularly nasty because the propellant tanks lost pressure and the intermediate bulkhead collapsed, allowing all of the LOX and RP-1 to mix, gel, and explode with an estimated force of 60,000 pounds of TNT. Atlas AC-5, while it produced a huge blast, was actually much less destructive because the explosion started at the bottom of the booster. The RP-1 tank went off first and most of the propellant had ignited before the LOX tank blew, minimizing mixing. This would also apply to Samos 3 and several other pad fallbacks discussed in here.

Atlas 9C has to be one for the record books since there has never (to my knowledge) been another failure of a US launch vehicle that did this much damage to the pad. There have been Soviet failures that did more damage, but not American ones. The umbilical towers and the large service tower were completely flattened. The top portion of the service tower shown here weighed about a ton, and it was thrown a few hundred feet by the blast. As you can see, the concrete launch stand was also caved in. They didn't rebuild the service tower on LC-12; after restoration, the pad hosted the second and third Atlas-Able launches and ICBM tests before being converted for Atlas-Agena.

All because of one incorrectly installed piece of plumbing in the Atlas.
« Last Edit: 04/29/2017 11:01 AM by WallE »

Offline kevin-rf

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Re: On-Pad Explosions
« Reply #116 on: 04/28/2017 06:03 PM »
Atlas 9C has to be one for the record books since there has never (to my knowledge) been another failure of a US launch vehicle that did this much damage to the pad. .... The umbilical towers and the large service tower were completely flattened. The top portion of the service tower shown here weight about a ton, and it was thrown a few hundred feet by the blast. The concrete launch stand was also caved in.
I wonder how the SpaceX Amos 6 and Antares CRS-3 failures stack up. Both did significant damage.
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Offline WallE

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Re: On-Pad Explosions
« Reply #117 on: 04/28/2017 06:38 PM »
I wonder how the SpaceX Amos 6 and Antares CRS-3 failures stack up. Both did significant damage.

They didn't knock the umbilical tower over, and on CRS-3, the Range Safety Officer sent the destruct command about two seconds before pad impact.

The damage caused by AMOS 6 has been discussed at length in other threads, and earlier in this thread, it was pointed out that pad explosions in the 50s-60s were expected and planned for. It was pretty obvious that SpaceX didn't worry about such an event in this day and age, as exhibited by the fact that they had the satellite and upper stages on the booster, all of which were fully fueled, as a PFRF was being conducted. They didn't do this in the 50s-60s. Atlas 9C had an unfueled second stage, dummy third stage, and the probe was not on top of it.

Shown here is the PFRF for Wally Schirra's Atlas. No Mercury capsule on top. They didn't take any chances back then, especially since this firing had the added objective of making sure there wasn't a recurrence of a turbopump problem that had destroyed two Atlas Fs earlier in the year.

Offline WallE

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Re: On-Pad Explosions
« Reply #118 on: 05/29/2017 05:13 PM »
The Thor was built with separate propellant tanks.  If it fell back onto the pad in a more or less vertical orientation, the vehicle descended below the pad deck through the center hole, hit the flame deflector and skidded along it, breaking neatly into two parts, one fuel and one oxidizer. One tank would break open below the deck, the other above. The propellants didn't inertially mix as thoroughly as was the case on other pads, such as Atlas.  While there was a still large conflagration, the blast effects were less than were seen on other stands.



Here's some high speed film of Atlas Centaur AC-5 from a couple different angles. The loss of booster engine thrust is clearly visible here and there's a LOX-rich explosion in the Quad III section at pad impact (probably ruptured low-pressure ducting) followed by a spreading thrust section fire and some LOX leakage out of the Quad I section. Also note how the vernier engine becomes intermittent post-impact. The final explosion begins just at the bottom of the RP-1 tank.

Also check out the photo here. The sustainer engine is badly burned, but the booster engines seem to have only impact damage, likely because they had shut off prior to impact/vehicle breakup.

Contrary to popular belief, damage to LC-36A was not that extensive, it was mostly fixed by June 1965.
« Last Edit: 05/29/2017 05:18 PM by WallE »

Offline rsnellenberger

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Re: On-Pad Explosions
« Reply #119 on: 05/29/2017 05:29 PM »
Watching these early attempts to land an Atlas booster helps me appreciate the progress we've made...

Offline WallE

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Re: On-Pad Explosions
« Reply #120 on: 06/07/2017 09:25 PM »
After watching that video of AC-5 more closely, I can see it now. Go to 9:35. The LOX fill/drain line strikes part of the launcher mechanism and rips open, LOX spills out, and gets ignited by the vernier exhaust. The verniers also have a momentary drop in thrust just before the explosion, possibly due to the LOX leak affecting the booster propellant feed system (cf. Atlas 3D).

Offline Jim

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Re: On-Pad Explosions
« Reply #121 on: 06/07/2017 09:29 PM »
LOX spills out, and gets ignited by the vernier exhaust.

LOX does not burn

Offline WallE

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Re: On-Pad Explosions
« Reply #122 on: 06/07/2017 09:49 PM »
LOX does not burn

Not the most precise language, but you get what I'm trying to say. Of course the LOX doesn't burn in the sense of catching fire, although anything that pure oxygen comes into contact with becomes incredibly flammable as Apollo 1 unfortunately demonstrated.

Offline Jim

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Re: On-Pad Explosions
« Reply #123 on: 06/07/2017 10:10 PM »
RP-1 within the booster section was the source of the explosion.  The LOX on the outside was just after math

Offline WallE

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Re: On-Pad Explosions
« Reply #124 on: 06/07/2017 11:17 PM »
RP-1 within the booster section was the source of the explosion.  The LOX on the outside was just after math

I noticed that the RP-1 fill/drain line also gets ruptured (go to 15:26 in the video). That aside, the rise-off connectors on the pad also hit the base of the booster skirt and get shoved up underneath it (12:25). The initial explosion happens on the side with the turbine exhaust, so there was probably plumbing in that area. I would have assumed the booster fuel feed system was empty after the prevalve closure cut off the RP-1 flow, but I may be wrong.

The explosion of the Centaur of course was what caused the real fireworks here. Normally hydrogen burns invisibly, but when mixed with oxygen it explodes with a brilliant yellow-white color, which of course can clearly be seen in the videos of the launch. The temperature at the center of the blast reached about 3000F and NASA used data from AC-5 to estimate the blast effects of a Saturn pad explosion, although the propellant load on the Saturn vehicles was significantly greater. A Saturn V pad explosion would have been a disaster beyond all proportions, N-1 5L isn't even a good comparison because the N-1 didn't use LH2.

This was the first Atlas to carry the full-up MA-5 propulsion system (the first couple of Atlas-Centaurs had uprated MA-2 engines), so it might not be completely surprising that new, unproven hardware like this would fail on its first launch.
« Last Edit: 06/11/2017 10:20 AM by WallE »

Offline WallE

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Re: On-Pad Explosions
« Reply #125 on: 06/10/2017 11:58 PM »
Two interesting photos. The first one shows the launcher from 576-A2 being "borrowed" to replace PALC 1-1's launcher after Samos 3. When you need a launcher mechanism in a hurry, best way to get one is to steal it, preferably from an inactive pad. The second photo shows the old, burned-out launcher being hauled away. I wonder if they scrapped it, or if it was refurbed. Who knows?

For comparison, the launcher on LC-36A was replaced with an emergency spare that they had in storage at the Cape. CCAS only had three other active Atlas pads in 1965 all of which were extremely busy, so there was no chance of stealing their launcher mechanisms.

Offline Jim

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Re: On-Pad Explosions
« Reply #126 on: 06/11/2017 04:17 PM »
Five pads were in use in 1965.  LC- 12,13, 14 and 36 A&B

Offline WallE

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Re: On-Pad Explosions
« Reply #127 on: 06/12/2017 12:33 AM »
Five pads were in use in 1965.  LC- 12,13, 14 and 36 A&B

There's the catch--36B wasn't in use in early 1965 (I should have clarified that I meant early '65), it was mothballed until AC-5 forced them to get it running. Since the pad was 90% finished anyway, they just decided to use it for the next Atlas-Centaur launch rather than wait for the repair work on 36A to be done.

VAFB in 1961 had two Atlas-Agena pads in operation, the second of which was the designated Midas launch facility, so PALC 1-1 had to be repaired as fast as possible and there were several inactive Atlas missile test pads that had a launcher readily available.
« Last Edit: 06/12/2017 12:51 AM by WallE »

Offline Blackstar

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Re: On-Pad Explosions
« Reply #128 on: 06/12/2017 02:42 AM »
Two interesting photos. The first one shows the launcher from 576-A2 being "borrowed" to replace PALC 1-1's launcher after Samos 3. When you need a launcher mechanism in a hurry, best way to get one is to steal it, preferably from an inactive pad. The second photo shows the old, burned-out launcher being hauled away. I wonder if they scrapped it, or if it was refurbed. Who knows?


Where did these images come from?

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Re: On-Pad Explosions
« Reply #129 on: 06/12/2017 03:16 AM »
Where did these images come from?

On Flickr. There's a lot of Atlas stuff there. SiloWorld used to be the go-to site for Atlas pics, but it hasn't been updated in years.

Offline Blackstar

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Re: On-Pad Explosions
« Reply #130 on: 06/12/2017 11:45 AM »
Where did these images come from?

On Flickr. There's a lot of Atlas stuff there. SiloWorld used to be the go-to site for Atlas pics, but it hasn't been updated in years.

Can you be a bit more specific?

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Re: On-Pad Explosions
« Reply #131 on: 06/13/2017 01:08 AM »
Can you be a bit more specific?

SDASM Archives is what you want to look for, you can also search for the Atlas serial number to find a specific vehicle.

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Re: On-Pad Explosions
« Reply #132 on: 06/13/2017 06:06 PM »
I'm surprised no one has posted Soyuz T-10-1 (unless I missed it scanning through the thread), a remarkable argument for a robust launch escape system for crewed missions:




Offline WallE

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Re: On-Pad Explosions
« Reply #133 on: 06/21/2017 12:58 PM »
I did a little research in regard to some of the launches mentioned in here. As I suspected, Atlas 51D was not a Range Safety destruct. The thrust section exploded at T+3 seconds followed by failure of the propellant tanks at T+5 seconds.

Atlas 45F/3F failed because of dried-up hypergol residue causing the booster engine main fuel valve to stick. This was due to repeated test firings of the engines prior to launch. On 45F, the main fuel valve never opened. On 3F, it did open but too late for B-2 engine start to be possible. After these incidents, checks/modifications were made to Atlas missiles in the field.

Atlas 106D/Samos 3, as already noted, experienced an improper umbilical disconnect that caused the booster to switch to external power, but because the power umbilicals had already ejected, the effect was to cause complete loss of power to all booster systems. Corrective action involved modifying the launcher system logic to not release the booster until all umbilicals were ejected first. In addition, modifications were made to umbilical installation procedures since a similar problem had caused the loss of Samos 1 eleven months earlier.

Accidental closure of the fuel staging disconnect valve was considered as a possibility on AC-5 before the culprit turned out to be the prevalves. A few small modifications were made to the staging disconnect valve just to be safe. The exact reason for the prevalve closure was not determined, however changes included replacing the hydraulic prevalves with manually activated ones, installing a lock that would be activated during the prelaunch countdown, and not draining propellant from the engines unless the main fuel tank was empty.
« Last Edit: 06/25/2017 08:28 PM by WallE »

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