This article was initially published in July of 2009.
Early in 1960, the Apollo program was conceived by the Eisenhower administration as a direct sequel to the Mercury program, the United States's first manned space program. Much of the US's backing of the manned space program was rhetoric until Russian Cosmonaut Yuri Gagarin aboard his Vostok 1 spacecraft made history with the world's first orbital crewed flight in April of 1961.
Once the Soviet Union had set the bar, it was seen by the current administration -- John F. Kennedy's -- as a provocation to raise the bar higher in what was clearly an escalating space race. The need to advance our space technology was not only about being superior to the Soviets from a technological perspective, but it was a political motivator to drive American industry to drive technological progress. So on May 25 of 1961, at a special joint session of Congress, President Kennedy delivered his now-famous statement:
First, I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth. No single space project in this period will be more impressive to mankind, or more important in the long-range exploration of space; and none will be so difficult or expensive to accomplish.
Read all parts of the "To the Moon" series by Jason Perlow
Considering that the United States had only just sent its first Mercury astronaut, Alan Shepherd, into a 15-minute sub-orbital flight only two weeks earlier, this was a very tall order.
The technology that would be needed (not to mention the money required to pull this off) would be unprecedented in terms of what had been achieved in the history of humankind.
Getting one man into orbit with Project Mercury was one thing or even two in the case of Gemini, but the rocket propulsion that would be required to get several men to the moon and back safely would need to be many orders of magnitude more powerful than anything that had existed previously.
The company that was on the forefront of American rocket engine design was Rocketdyne (now known as Aerojet Rocketdyne), at the time a subsidiary of North American Aviation. In 1955, Rocketdyne was a company that employed about 2,500 people and was involved in cruise missile research for the United States military, producing a rocket engine for the SM-64 Navaho.
The rocket engine for the Navaho used a liquid kerosene propellant (RP-1) with liquid oxygen (LOX) as the oxidizer. The Navaho was canceled in 1957, after several failed launches.
The canceling of the Navaho contract would have seemed to have spelled the end for kerosene-fueled rockets and Rocketdyne's continued research, if it wasn't for the fact that the Russians launched Sputnik into orbit, which meant that theoretically, the communists could also drop a nuclear warhead anywhere in the United States whenever they wanted to.
This accelerated the development of Intercontinental Ballistic Missiles such as the Atlas (which was also the launch platform for Project Mercury) and Intermediate and Medium Range Ballistic Missiles such as the Thor and Jupiter, all of which Rocketdyne designed the propulsion systems for.
The Mighty F-1
In order to send men to the moon, a much larger rocket engine was going to be needed. In 1960, the Marshall Space Flight Center, led by NASA's chief rocket scientist Wernher Von Braun, determined via early calculations that they would need to design a multi-stage rocket with over 7 million pounds of thrust in its boost stage -- this was many orders of magnitude above what was currently available.
It eventually fell upon Rocketdyne to design an RP-1/LOX engine, eventually designated the F-1, which would have 1.5 million pounds of takeoff thrust apiece. Five F-1s would be used on the S-IC first stage on the Saturn V, which would have a combined thrust of 7.5 million pounds.
NASA had just under ten years in order to satisfy Kennedy's edict to get men on the Moon. Fortunately, Rocketdyne had already done a lot of the groundwork and gained a lot of experience with Atlas, Jupiter, and Thor, and had begun the early development of a prototype high-thrust rocket engine for the Air Force even before NASA asked for engines with the specifications for the Saturn V boost stage.
Rocketdyne was testing early prototypes of the precursor to the F-1 as early as 1959. The problem now was scaling up those engines and designing turbopumpsthat could handle the 40,000+ gallons per minute each giant F-1 engine would consume.
Needless to say, the effort that went into designing and testing the F-1 engines were enormous. The turbomachinery and pressure vessels would frequently explode under the incredible forces and speeds they had to operate under, and many design changes had to occur before the engine could even be flight tested.
From 1957 to 1961, Rocketdyne grew from a company of 2,500 people to well over 20,000 employees and had tremendous resources and many test facilities at their disposal. By 1961 functional F-1 engines were being tested at Edwards Air Force base on huge, oil-derrick sized platforms made to withstand over 2 million pounds of rocket thrust. The first F-1 engines flew on Apollo 4, in November of 1967.
The Versatile J-2
Still, even the F-1 engine alone was not enough to send men to the Moon. While kerosene/LOX rocket engine technology was very powerful, it was also a trade-off. To use the F-1 or other kerosene/LOX engines on the upper stages of the Saturn V would have meant that the rocket would have needed to be much, much heavier and much larger because of the specific impulse characteristics of RP-1 liquid rocket fuel.
Instead, a completely different rocket engine technology would need to be developed that could burn fuel with a much higher specific impulse -- Liquid Hydrogen/LOX engines. Additionally, the upper stage rocket engine on the S-IVB that would send the Apollo spacecraft into Trans Lunar Injection had to be re-startable, which the F-1 was not.
The J-2 project was run in parallel with the F-1 project, and in many respects, the Rocketdyne engineers working on it had much more difficult challenges to overcome than with F-1 because LOX/Hydrogen rockets were utterly new technology and required the development of advanced cryogenic refrigeration and coolant technology for the liquid hydrogen fuel.
Each J-2 was rated at over 200,000 lbs of thrust. Five were used on the S-II stage and a single J-2, which was restartable, was used on the S-IVB that carried the Command Module/Service Module to the Moon. The first J-2 made its first orbital flight on February 26, 1966, aboard a Saturn IB rocket, as part of a full test of the S-IVB stage in space.
Aerojet Rocketdyne continues to be a key player in the rocket propulsion industry. After Apollo, Aerojet Rocketdyne was awarded the contract to build the RS-25 Space Shuttle Main Engine (SSME), which are LOX/Hydrogen rocket engines that are designed to be re-usable and deliver 400,000 lb of thrust each.
In June of 2006, for the Constellation program, Rocketdyne was awarded the rocket engine contract on the Ares I, also known as "The Stick", which combined a Solid Rocket Booster (SRB) from Thiokol as the first stage and a Rocketdyne J-2X on the Earth Departure Stage for the Orion spacecraft -- the modern equivalent of the S-IVB on the Saturn V.
When the Constellation program was canceled, the J-2X eventually ended up being replaced with the RL-10, also produced by Aerojet Rocketdyne and is slated to be used on the ULA Vulcan Centaur and Northop Grumman Omega commercial/military launch vehicles.
But what about the future of Moon rockets? NASA's Space Launch System, which is set to be the spiritual successor to the Saturn V, does not yet have a moon mission configuration. But the future of moon missions may end up relying entirely on private industry, not NASA. SpaceX is developing the BFR or the "Starship" which aspires to be a private industry heavy-lift rocket that would return humankind to the moon and also to Mars.
Were you an employee of Rocketdyne during the Apollo or Shuttle eras? Talk Back and Let Me Know.
Rocketdyne F-1 and J-2 Rocket Engine Development and Testing