Winston
Lorenzo von Matterhorn
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I found a recently posted video of this, investigated, and found it interesting:
Atlas Centaur AC-5 Launch Failure 3/2/1965
https://en.wikipedia.org/wiki/Atlas-Centaur#R&D_flights
The fifth flight on March 2, 1965 was only intended to carry out a single burn of the Centaur, and program officials felt confident that this simple mission could be performed with no difficulties. This was also the first Atlas-Centaur equipped with the uprated 165,000 pound MA-5 booster engines (they had been tested previously on two Atlas-Agena flights). Instead, AC-5 proved a complete disaster when the booster engines shut down 1.5 seconds after liftoff. The sustainer engine by itself could not lift the 150 ton rocket and it fell back onto LC-36A in the biggest pad explosion yet seen at Cape Canaveral. As a result, NASA was forced to finish work on LC-36B, constructed as a backup pad, but abandoned when it was 90% completed; the damage to LC-36A was not as severe as it looked and repairs were largely completed in three months. Most damage was thermal rather than structural and the upper portion of the umbilical tower, which was in the center of the LH2 blast, had been subjected to temperatures of 6000°F (3315°C). The accident marked the first failure of an Atlas in a space launch since Midas 8 in June 1963, a new record at the time of 26 consecutive flights with only malfunctions of the upper stages or payload. This would be the last on-pad explosion at Cape Canaveral until 2016. [referring to SpaceX's Falcon explosion - W]
Postflight investigation examined several possible reasons for the booster engine shutdown; these included closure of the booster fuel prevalves, rupture of propellant ducting, an open fuel fill/drain valve, an inadvertent BECO signal, or accidental closure of the fuel staging disconnect valve. Most of them were quickly ruled out and attention centered around the prevalves. The low pressure booster fuel ducting was found to have collapsed from the sudden loss of fuel flow, but had not ruptured. Impact on the pad occurred at T+2.7 seconds and all telemetry was lost at T+3 seconds. All other launch vehicle systems functioned normally until that point. The hydraulic clamps that held the booster section to the missile structure were examined as well, but had no sign of failure.
Investigation found that the fuel prevalves had only opened partially and the propellant flow force was enough to push them shut, starving the booster engines of RP-1 and causing a LOX-rich shutdown. Engine start had proceeded normally and all booster systems functioned properly until the prevalves closed. Bench testing confirmed that there were several possible ways that the prevalves would only open partially, although the exact reason was not determined. This failure mode had never occurred in the 240 Atlas launches prior to AC-5 although it had always been possible. Although the sustainer prevalve had not been at fault, it was also replaced with an Atlas E-type prevalve, which used manual control. Until a more permanent solution could be found, a temporary fix was made for Atlas-Agena vehicles by equipping the prevalves with a manual lock that would be enabled during the prelaunch countdown.
In addition, an unrelated system malfunction in AC-5 was discovered when examination of telemetry data found that a power failure had occurred in the guidance computer, which could have had an adverse effect on the flight had it continued normally. As a temporary fix for Atlas-Centaur AC-6, 7, and 8, several unused components were removed from the computer in order to reduce system complexity and failure points.
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Film from the Atlas Centaur Heritage Film Collection which was donated to the San Diego Air and Space Museum by Lockheed Martin and United Launch Alliance. The Collection contains 3,000 reels of 16-millimeter film.
Ultra slow motion, start at 1:04.
Side view. Not an identified launch according to the title, but certainly looks like it's AC-5:
Start at 0:20:
The familiar green tint seen at vernier rocket ignition, especially in the first video, led me to investigate. Sure enough:
"The LR-101 was a single-start, fixed-thrust engine with an expansion ration of 6:1. In its Block 2 version, ignition occurred by means of pyrophoric (hypergolic) fluid (a mixture of tri-ethyl aluminum and tri-ethyl boron) which ignites spontaneously in the presence of oxygen."
Atlas Centaur AC-5 Launch Failure 3/2/1965
https://en.wikipedia.org/wiki/Atlas-Centaur#R&D_flights
The fifth flight on March 2, 1965 was only intended to carry out a single burn of the Centaur, and program officials felt confident that this simple mission could be performed with no difficulties. This was also the first Atlas-Centaur equipped with the uprated 165,000 pound MA-5 booster engines (they had been tested previously on two Atlas-Agena flights). Instead, AC-5 proved a complete disaster when the booster engines shut down 1.5 seconds after liftoff. The sustainer engine by itself could not lift the 150 ton rocket and it fell back onto LC-36A in the biggest pad explosion yet seen at Cape Canaveral. As a result, NASA was forced to finish work on LC-36B, constructed as a backup pad, but abandoned when it was 90% completed; the damage to LC-36A was not as severe as it looked and repairs were largely completed in three months. Most damage was thermal rather than structural and the upper portion of the umbilical tower, which was in the center of the LH2 blast, had been subjected to temperatures of 6000°F (3315°C). The accident marked the first failure of an Atlas in a space launch since Midas 8 in June 1963, a new record at the time of 26 consecutive flights with only malfunctions of the upper stages or payload. This would be the last on-pad explosion at Cape Canaveral until 2016. [referring to SpaceX's Falcon explosion - W]
Postflight investigation examined several possible reasons for the booster engine shutdown; these included closure of the booster fuel prevalves, rupture of propellant ducting, an open fuel fill/drain valve, an inadvertent BECO signal, or accidental closure of the fuel staging disconnect valve. Most of them were quickly ruled out and attention centered around the prevalves. The low pressure booster fuel ducting was found to have collapsed from the sudden loss of fuel flow, but had not ruptured. Impact on the pad occurred at T+2.7 seconds and all telemetry was lost at T+3 seconds. All other launch vehicle systems functioned normally until that point. The hydraulic clamps that held the booster section to the missile structure were examined as well, but had no sign of failure.
Investigation found that the fuel prevalves had only opened partially and the propellant flow force was enough to push them shut, starving the booster engines of RP-1 and causing a LOX-rich shutdown. Engine start had proceeded normally and all booster systems functioned properly until the prevalves closed. Bench testing confirmed that there were several possible ways that the prevalves would only open partially, although the exact reason was not determined. This failure mode had never occurred in the 240 Atlas launches prior to AC-5 although it had always been possible. Although the sustainer prevalve had not been at fault, it was also replaced with an Atlas E-type prevalve, which used manual control. Until a more permanent solution could be found, a temporary fix was made for Atlas-Agena vehicles by equipping the prevalves with a manual lock that would be enabled during the prelaunch countdown.
In addition, an unrelated system malfunction in AC-5 was discovered when examination of telemetry data found that a power failure had occurred in the guidance computer, which could have had an adverse effect on the flight had it continued normally. As a temporary fix for Atlas-Centaur AC-6, 7, and 8, several unused components were removed from the computer in order to reduce system complexity and failure points.
---------
Film from the Atlas Centaur Heritage Film Collection which was donated to the San Diego Air and Space Museum by Lockheed Martin and United Launch Alliance. The Collection contains 3,000 reels of 16-millimeter film.
Ultra slow motion, start at 1:04.
Side view. Not an identified launch according to the title, but certainly looks like it's AC-5:
Start at 0:20:
The familiar green tint seen at vernier rocket ignition, especially in the first video, led me to investigate. Sure enough:
"The LR-101 was a single-start, fixed-thrust engine with an expansion ration of 6:1. In its Block 2 version, ignition occurred by means of pyrophoric (hypergolic) fluid (a mixture of tri-ethyl aluminum and tri-ethyl boron) which ignites spontaneously in the presence of oxygen."
