When NASA first began launching rockets into space – barely half a century after the first airplane take flight of stairs – it encountered what it calls the " pogo problem " .
During the launch of Saturn V rocket ’s first stage burn , part of the uncrewed Apollo 6 mission , the rocket engine go through cycle along its duration , like springs going up and down on a pogo marijuana cigarette .
" Pogo come about when a partial vacuum in the fuel and oxidizer provender lines reached the railway locomotive provoke chamber causing the locomotive engine to skip over , " John Uri of NASA ’s Johnson Space Centerexplains . " These oscillations then travel up the bloc of the launch vehicle ensue in vivid quiver in the Command Module and make some trivial structural impairment to the Spacecraft Lunar Module Adaptor ( SLA ) . Had a crew been onboard , they would have experience severe vibrations and even potential injury . "
The problem had occurred in previous rocket launches , including Titan II used for the Gemini program . Though it might not fathom like a immense deal , and crews carried in the Command Module could have been perfectly safe , it lead Marshall Space Flight Center Director Wernher von Braun to conclude that unless it was lick " we just can not go to the Moon . ”
NASA make a Pogo Working Group to analyze the trouble and come up with solutions , conclude that they should " detune " the engine and change the frequency of the vibration by filling prevalve cavities on the liquid oxygen feed lines with helium .
" inject helium into those line of reasoning prior to lighting would effectively work as a shock absorber to forbid the cycle from traveling up and down fuel and oxidant provender lines , " Uri explain .
This worked well enough , and shortly NASA was able to send astronauts to the Moon . However , the pogo impression continue to pose problem for the space agency , notably during the approximate - ruinous Apollo 13 mission .
" During the second stage burn , two episodes of pogo take place on the center J-2 engine as expected from previous mission , but the third occurrence diverged severely and speedup at the engine attachment reach an forecast 34 thou ’s ( the accelerometer conk out of kitchen stove ) before the engine ’s burning chamber low - storey press sensor commanded a shut down,“NASA explainsin a report on pogo in spaceflight . " It was estimated in the post - flight investigation that only one more cycle of bounty growth could have been sustained without catastrophic morphological failure . "
