аФон+> ...Возникший грохот по уровню шума был сравним с извержением в 1883 г. вулкана Кракатау в Зондском проливе. Вызванная работой двигателей первой ступени воздушная ударная волна была зарегистрирована Геологической обсерваторией Ламон-Доэрти в Палисейдсе, шт. Нью-Йорк, расположенном в 1770 км от места старта."[/QUOTE]
Интересно. А вы не читали о регистрации шумов во время стендовых испытаний ступени S-IC? аФон+> http://www.epizodsspace.narod.ru/bibl/raketostr3/4-1.html аФон+> [QUOTE]Анализ результатов полета показал, что причиной отказов в полете Apollo-6 были продольные колебания ракеты большой амплитуды, вызванные совпадением частоты колебаний топлива в топливных магистралях и собственных колебаний корпуса ступени S-IC.
У Шунейко перевод мягко говоря...
Почему-то изогнутую топливную магистраль перевели как "гибкую"...
И гелий нагнетали не в полости корпуса а в магистрали...
Вот выдержки из доклада НАСА конгрессу США по этому вопросу:
Unlike the near perfect flight of Apollo 4, Apollo 6 experienced problems right from the start. Two minutes into the flight, the rocket experienced severe Pogo oscillations for about 30 seconds. George Mueller explained the cause to a congressional hearing:
Pogo arises fundamentally because you have thrust fluctuations in the engines. Those are normal characteristics of engines. All engines have what you might call noise in their output because the combustion is not quite uniform, so you have this fluctuation in thrust of the first stage as a normal characteristic of all engine burning.
Now, in turn, the engine is fed through a pipe that takes the fuel out of the tanks and feeds it into the engine. That pipe's length is something like an organ pipe so it has a certain resonant frequency of its own and it really turns out that it will oscillate just like an organ pipe does.
The structure of the vehicle is much like a tuning fork, so if you strike it right, it will oscillate up and down longitudinally. In a gross sense it is the interaction between the various frequencies that causes the vehicle to oscillate.
In part due to the pogo, the spacecraft adaptor that attached the CSM and mockup of the Lunar Module to the rocket started to have some structural problems. Air borne cameras recorded several pieces falling off it at T +133.
After the first stage was jettisoned at the end of its task, the S-II second stage began to experience its own problems. Engine Number Two (it had five) had performance problems from 206 to 319 seconds after liftoff and then at 412 seconds shut down all together. Then two seconds later Engine Number Three shut down as well. The onboard computer was able to compensate and the stage burned for 58 more seconds than normal. Even so the S-IVB third stage also had to burn for 29 seconds longer than usual.
S-IC impact location 30°12′ N 74°19′ W; S-II impact location 31°12′ N 32°11′ W
И как они решали эти проблемы...
The cause of the pogo during the first stage of the flight was well known. However, it had been thought that the rocket had been 'detuned'. To further detune the rocket, it was decided to fill the cavities with helium gas.
The failure of the two engines in the second stage was traced to the rupturing of a fuel line that fed the engine igniters. The ignitor was essentially a miniature rocket motor mounted in the wall of the J-2 engine's pressure chamber. It was fed by small-diameter flexible lines carrying liquid hydrogen and liquid oxygen. During the S-II second stage burn, the hydrogen line feeding the engine number three ignitor broke due to vibration. As a result, the igniter fed pure liquid oxygen into the pressure chamber. Normally the J-2 engine burns a hydrogen-rich mixture to keep temperature down. The liquid oxygen flow caused a much higher temperature locally and eventually the pressure chamber failed. The sudden drop in pressure was detected and caused a shutdown command to be issued. Unfortunately, the shutdown command signal for engine three was cross-wired to engine two. Engine two shut down and in turn its pressure sensor sent a shutdown signal back to engine three.
The problem in the ignitor fuel lines was not detected during ground testing because a stainless steel mesh covering the fuel line became saturated with liquid air due to the extreme cold of the liquid hydrogen flowing through it. The liquid air damped a vibration mode that became evident when tests were conducted in a vacuum after the Apollo 6 flight. This was also a simple fix, involving replacing the flexible bellows section where the break occurred with a loop of stainless steel pipe. The S-IVB used the same J-2 engine design as the S-II and so it was decided that an ignitor line problem had also stopped the third stage from reigniting in Earth orbit.