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On the 12th of September 1962, President John F. Kennedy made his famous speech about landing
a man on the Moon by the end of the decade.
At this point in time, NASA had just several hours worth of human spaceflight experience.
Many Americans had accepted that the space race would be won by the Soviet Union,
who had already claimed the records for launching the first satellite and the first human into orbit.
So in order to achieve their goal of reaching the Moon, NASA would need to develop much
larger rockets with engines more powerful than anything they had made before.
But scaling up to a much larger rocket design sent NASA engineers into a new world of complex problems.
In this video we’re going to look at the issues that NASA had with their F1 engine.
We’re also going to look at how they fixed these issues and the unusual method they used
to test it.
In order to lift the enormous Saturn 5 rocket off the launch pad, it required five F1 engines
on the first stage, each capable of producing 1.5 million pounds of thrust.
In order to achieve this amount of thrust, massive amounts of RP1 fuel and liquid oxygen
had to be pumped into the thrust chamber.
Here, the two propellants would combust and lift the Saturn 5 away from the launch pad.
The first stage alone would burn through an entire Olympic swimming pool’s worth of
fuel in just over 2 minutes.
The company tasked with making such a powerful engine was Rocketdyne.
They had designed the F1 engine several years before for the US Air Force - but after the
Air Force couldn’t find a use for such a powerful engine, development was stopped.
Until NASA came along.
In June 1962 rocketdyne were ready to perform a long duration test of the F1 engine.
But as the engine ignited and the turbopumps spooled up, the test came to a catastrophic end
when the engine exploded.
It took several more explosive tests before the engineers finally found what was going wrong -
combustion instability.
This is where the propellants in the thrust chamber burn unevenly and cause enormous pressure
swings inside the chamber.
As one area of the chamber fills with more oxygen, it produces more heat which pushes
the flame around in the thrust chamber.
The reason this was so catastrophic in the F1 engine - is because these pressure swings
were happening 2000 times a second, enough to completely rip apart the engine.
At this point, the Apollo program was well underway and NASA needed a fully capable engine
for the first crewed flights which were just a few years away.
But since an engine of this scale had never been made before, the solution to this problem
wasn’t going to be obvious.
Engineers started to focus on the injector plate, which feeds the fuel and oxidizer into
the thrust chamber.
The original design was a single large plate with multiple injection holes.
Although this was a common design, previous engines never suffered from instability since
their thrust chambers were much smaller and the propellants were more contained.
In order to solve this critical issue, Rocketdyne engineers looked back to one of the very first
rocket designs, the V2 rocket.
This rocket was developed by the Germans during the second world war - but it contained the
perfect solution to fix the F1 engine.
Instead of a single flat injector plate, the V2 featured several different nozzles which
separated the combustion into different streams.
The engineers believed that the more controlled sections in the V2 engine eliminated the possibility
of combustion instability.
In order to translate this theory onto the enormous F1 engine without a complete redesign,
engineers added a series of baffles to the injector plate to split the combustion up
into different zones.
After experimenting with many variations of baffle designs, the engineers came across
a layout which seemed to stabilize the combustion.
This new design was put to the test and sure enough, the engine executed a flawless burn.
But the engineers weren’t convinced that the problem was fully fixed.
Many worried that once the engine was in-flight, the extra forces and vibrations could reintroduce
instability back into the engine.
So in order to fully test the new design, NASA placed a small bomb in the center of
the injector plate and set it off as soon as the engine fired up.
The idea was that a small explosion within the engine would create an enormous amount
of instability - far greater than the engine would naturally receive.
When the bomb went off, the flame inside the engine became completely unstable.
But almost instantly, the baffles on the injector plate started to dampen the pressure swings
and the combustion became stable again.
NASA performed multiple explosive tests in order to make sure that the combustion instability had gone.
From the first Saturn 5 launch to the last, 65 F1-engines propelled multiple astronauts
into space without any instability problems.
Looking back to a time when rocket engines were designed using slide rules, the ingenuity
that was required to overcome these monumental challenges is spectacular.
And although we have yet to return to the Moon, we can appreciate the incredible genius
and dedication that went into achieving Kennedy’s goal.
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Thank you very much for watching and I’ll see you in the next video.