The Saturn rocket series’ biggest brother, the culmination of America’s efforts during the Cold War Space Race against the Russians, and the paragon of human spaceflight achievement, The Apollo program’s primary tool was the mighty Saturn V, the pride of American space exploration, and NASA’s poster child. Designed by Wehrner von Braun, the massive rocket took 24 astronauts beyond Earth’s orbit, 12 of which walked on the Moon.
The Saturn V dwarfed every previous rocket fielded by America in the Space Race, remaining to this day the tallest, heaviest, and most powerful rocket ever brought to operational status and still holds records for the heaviest payload launched and largest payload capacity. On the pad, she stood 363 feet (111m) tall, taller than the Statue of Liberty by 58 feet, with a diameter of 33 feet (10m), and weighed 6.5 million pounds fully fueled. Her designed payload capacity was rated at 261,000 pounds (118,000 kg) to Low Earth Orbit and 90,000 pounds (41,000 kg) to the Moon, but in later missions was able to carry about 310,000 pounds (140,000 kg) to LEO and sent up to 107,100 lb (48,600 kg) worth of spacecraft to the Moon.
The total launch vehicle was a 3 stage vehicle: the S-IC first stage, S-II second stage and the S-IVB third stage. The first stage used RP-1 for fuel, while the second and third stages used liquid hydrogen (LH2), with all three using liquid oxygen (LOX) for oxidizer.
The first stage of the Saturn V is the lower section of the rocket, producing the most thrust in order to get the vehicle off the pad and up to altitude for the second stage.
The Rocketdyne F-1 engine used to propel the rocket was designed for the U.S. Air Force by Rocketdyne for use on ICBM’s, but was dropped and picked up by NASA for use on their rockets. This engine still is the most powerful single combustion chamber engine ever produced, producing 1,522,000 lbf (6,770 kN) at sea level and 1,746,000 lbf (7,770 kN) in a vacuum. The S-IC has five F-1 engines. Total thrust on the pad, once fully throttled, was well over 7,600,000 lbf, consuming the RP-1 fuel and LOX oxidizer at a jaw-dropping 13 metric tonnes per second.
The launch sequence for the first stage begins at approx. T-minus 8.9 seconds, when the five F-1 engines are ignited to achieve full throttle on t-minus 0. The center engine ignited first, followed by opposing outboard pairs at 300-millisecond intervals to reduce the structural loads on the rocket. When thrust had been confirmed by the onboard computers, the rocket was “soft-released” in two stages: first, the hold-down arms released the rocket, and second, as the rocket began to accelerate upwards, it was slowed by tapered metal pins pulled through dies for half a second.
It took about 12 seconds for the rocket to clear the tower. During this time, it yawed 1.25 degrees away from the tower to ensure adequate clearance despite adverse winds. (This yaw, although small, can be seen in launch photos taken from the east or west.) At an altitude of 430 feet (130 m) the rocket rolled to the correct flight azimuth and then gradually pitched down until 38 seconds after second stage ignition. This pitch program was set according to the prevailing winds during the launch month. The four outboard engines also tilted toward the outside so that in the event of a premature outboard engine shutdown the remaining engines would thrust through the rocket’s center of gravity. At this point in the launch, forces exerted on the astronauts is about 1.25 g.
At about T+ 1 minute, the rocket has gone supersonic, at which point, shock collars form around the rocket’s second stage separator. At this point, the vehicle is between 3 and 4 nautical miles in altitude.
As the rocket ascends into thinner atmosphere and continues to burn fuel, the rocket becomes lighter, and the engine efficiency increases, accelerating the rocket at a tremendous rate.
At about 80 seconds, the rocket experienced maximum dynamic pressure. Once maximum efficiency of the F-1 engines is achieved, the total thrust peaks at around 9,000,000 lbf. At T+ 135 seconds, astronaut strain has increased to a constant 4 g’s.
At around T+ 168 seconds, the engines cut off as all fuel in the first stage is expended. At this point in flight, the rocket is at an altitude of about 36 nautical miles (67 km), was downrange about 50 nautical miles (93 km), and was moving about 6,164 miles per hour (2,756 m/s). The first stage separates at a little less than 1 second following engine cutoff to allow for engine trail-off.
Eight small solid fuel separation motors backs the S-IC from the rest of the vehicle, and the first stage continues ballistically to an altitude of about 59 nautical miles (109 km) and then falls in the Atlantic Ocean about 300 nautical miles (560 km) downrange. Contrary to the common misconception, the S-IC stage never leaves Earth’s atmosphere, making it, technically, an aircraft.
The second stage is responsible with propelling the vehicle to orbital altitude and velocity. Already up to speed and altitude, the second stage doesn’t require as much Delta-V to achieve it’s operation.
For the first two unmanned launches, eight solid-fuel ullage motors ignited for four seconds to give positive acceleration to the S-II stage, followed by start of the five Rocketdyne J-2 engines. For the first seven manned Apollo missions only four ullage motors were used on the S-II, and they were eliminated completely for the final four launches.
About 30 seconds after first stage separation, the interstage ring dropped from the second stage. This was done with an inertially fixed attitude so that the interstage, only 1 meter from the outboard J-2 engines, would fall cleanly without contacting them. Shortly after interstage separation the Launch Escape System was also jettisoned.
About 38 seconds after the second stage ignition the Saturn V switched from a preprogrammed trajectory to a “closed loop” or Iterative Guidance Mode. The Instrument Unit now computed in real time the most fuel-efficient trajectory toward its target orbit. If the Instrument Unit failed, the crew could switch control of the Saturn to the Command Module’s computer, take manual control, or abort the flight.
About 90 seconds before the second stage cutoff, the center engine shut down to reduce longitudinal pogo oscillations (a forward/backward oscillation caused by the unstable combustion of propellant). At around this time, the LOX flow rate decreases, changing the mix ratio of the two propellants, ensuring that there would be as little propellant as possible left in the tanks at the end of second stage flight. This was done at a predetermined Delta-V.
Five level sensors in the bottom of each S-II propellant tank are armed during S-II flight, allowing any two to trigger S-II cutoff and staging when they were uncovered. One second after the second stage cut off it separates and several seconds later the third stage ignited. Solid fuel retro-rockets mounted on the interstage at the top of the S-II fires to back it away from the S-IVB. The S-II impacts about 2,300 nautical miles (4,200 km) from the launch site.
The S-II would burn for 6 minutes to propel the vehicle to 109 miles (175km) and 15,647 mph, close to orbital velocity.
Now in space, the third stage, the S-IVB’s sole purpose is to prepare and push the Command, Service, and Lunar Modules to the Moon via TLI.
Unlike the two-plane separation of the S-IC and S-II, the S-II and S-IVB stages separated with a single step. Although it was constructed as part of the third stage, the interstage remained attached to the second stage.
During Apollo 11, a typical lunar mission, the third stage burned for about 2.5 minutes until first cutoff at 11 minutes 40 seconds. At this point it was 1,430 nautical miles (2,650 km) downrange and in a parking orbit at an altitude of 103.2 nautical miles (191.1 km) and velocity of 17,432 mph (7,793 m/s). The third stage remained attached to the spacecraft while it orbited the Earth one and a half times while astronauts and mission controllers prepared for translunar injection.
This parking orbit is quite low, and would eventually succumb to aerodynamic drag if maintained, but on lunar missions, this can be gotten away with because the vehicle is not intended to stay in said orbit for long. The S-IVB also continued to thrust at a low level by venting gaseous hydrogen, to keep propellants settled in their tanks and prevent gaseous cavities from forming in propellant feed lines. This venting also maintained safe pressures as liquid hydrogen boiled off in the fuel tank. This venting thrust easily exceeded aerodynamic drag.
On Apollo 11, TLI came at 2 hours and 44 minutes after launch. The S-IVB burned for almost six minutes giving the spacecraft a velocity close to the Earth’s escape velocity of 25,053 mph (11,200 m/s). This gave an energy-efficient transfer to lunar orbit, with the Moon helping to capture the spacecraft with a minimum of CSM fuel consumption.
After the TLI, the Saturn V has fullfilled its purpose of getting the Apollo crew and modules on their way to the Moon. At around 40 minutes after TLI, the Command Service module (the conjoined Command module and Service Module) separate from the LM adapter, turns 180 degrees, and docks with the exposed Lunar Module. After 50 minutes, the 3 modules separate from the spent S-IVC, in a process known as Transposition, docking and extraction.
Of course, if the S-IVC were to remain on the same course (in other words, if they leave it right there unattended), due to the physics of zero gravity environments, the third stage would present a collision hazard for the Apollo modules. To prevent this, its remaining propellants were vented and the auxiliary propulsion system fired to move it away. Before Apollo 13, the S-IVB was directed to slingshot around the Moon into a solar orbit, but from 13 onward, the S-IVB was directed to actually impact the Moon. The reason for this was for existing probes to register the impacts on their seismic sensors, giving valuable data on the internals and structure of the Moon.
Launch Escape System
The Saturn V carries a frightening amount of potential energy (the Saturn V on the pad, if launch failed and the rocket ruptured and exploded, would have released an energy equivalent to 2 kilotons of TNT, a force shy of the smallest atomic weapons), which luckily was unleashed as planned without incident. However, this being NASA, precautions were made to save the crew in event of a catastrophic failure.
The LES (Launch Escape System) has been around since the Mercury Program as a way to get the crew capsule away from a potential explosion on the pad or in early launch. The idea is that a small rocket would take the capsule far enough away from the rocket that parachutes could be deployed.
The LES included three wires that ran down the exterior of the launch vehicle. If the signals from any two of the wires were lost, the LES would activate automatically. Alternatively, the Commander could activate the system manually using one of two translation controller handles, which were switched to a special abort mode for launch. When activated, the LES would fire a solid fuel escape rocket, and open a canard system to direct the Command Module away from, and off the path of, a launch vehicle in trouble. The LES would then jettison and the Command Module would land with its parachute recovery system.
If the emergency happened on the launch pad, the LES would lift the Command Module to a sufficient height to allow the recovery parachutes to deploy safely before coming in contact with the ground.
An interesting factoid is how much power the LES possesses; in fact, the LES rocket produces more thrust (147,000 pounds-force (650 kN) sea level thrust) than the Mercury-Redstone rocket (78,000 pounds-force (350 kN)) used to launch Freedom-7 during the Mercury program.
After budget cuts necessitated mission cancellations and the end of the Apollo program, NASA still had at least one Saturn V rocket intended for Apollo 18/19. Luckily, in 1965, the Apollo Applications Program was established to find a use for the Saturn V rocket following the Apollo program. Much of the research conducted in this program revolved around sending up a space station. This station (now known as Skylab) would be built on the ground from a surplus Saturn IB second stage and launched on the first two live stages of a Saturn V.
The only significant changes to the Saturn V from the Apollo configurations involved some modification to the S-II to act as the terminal stage for inserting the Skylab payload into Earth orbit, and to vent excess propellant after engine cutoff so the spent stage would not rupture in orbit. The S-II remained in orbit for almost two years, and made an uncontrolled re-entry on January 11, 1975.
This would be NASA’s only Saturn V launch not associated with the Apollo program, and unfortunately, would prove to be the Saturn V’s last one. There were other concepts for Saturn V’s as launch vehicles, including a space shuttle design, but none of these ever came to fruition.
From 1964 until 1973, a total of $6.417 billion ($41.4 billion in 2016) was appropriated for the Saturn V, with the maximum being in 1966 with $1.2 billion ($8.75 billion in 2016).
Displays and Survivors
There are several displays of Saturn V rockets around the United States, including a few test rockets and unused ones intended for flight. The list below details what and where they are.
Two at the U.S. Space & Rocket Center in Huntsville:
SA-500D is on horizontal display made up of S-IC-D, S-II-F/D and S-IVB-D. These were all test stages not meant for flight. This vehicle was displayed outdoors from 1969 to 2007, was restored, and is now displayed in the Davidson Center for Space Exploration. The second display here is a vertical display (replica) built in 1999 located in an adjacent area.
One at the Johnson Space Center made up of first stage from SA-514, the second stage from SA-515 and the third stage from SA-513 (replaced for flight by the Skylab workshop). With stages arriving between 1977 and 1979, this was displayed in the open until its 2005 restoration when a structure was built around it for protection. This is the only display Saturn consisting entirely of stages intended to be launched.
One at the Kennedy Space Center Visitor Complex, made up of S-IC-T (test stage) and the second and third stages from SA-514. It was displayed outdoors for decades, then in 1996 was enclosed for protection from the elements in the Apollo/Saturn V Center.
The S-IC stage from SA-515 is on display at the Michoud Assembly Facility in New Orleans, Louisiana.
The S-IVB stage from SA-515 was converted for use as a backup for Skylab, and is on display at the National Air and Space Museum in Washington, D.C.
Here, we have the Saturn V rocket, housed inside the Apollo/Saturn V Center at Kennedy Space Center near Titusville, Florida, just a few miles from Launch complex 39, where these beasts once roared into the sky.
When we look at the enormous first stage of the Saturn V rocket, called an S-IC, we think “spaceship”. Truthfully, the Saturn V first stage never actually made it into space. The stage only burned for the first 150 seconds of flight, then dropped away from the rest of the rocket, all while remaining totally inside Earth’s atmosphere. The S-IC stage is merely an aircraft.
Even more truthfully, the S-IC stage displayed here at the Apollo/Saturn V Center at the Kennedy Space Center in Florida, never flew at all. It is a static test article, fired while firmly attached to the ground, to make sure the rocket would actually hold together in flight. Obviously, these tests were successful, (e.g. she didn’t blow up), and she sits on our Apollo museum today. I wrote more about this particular stage in a previous post, (click here to view.)
The rest of the rocket, the second and third stages, called the S-II and S-IVB stages, did fly into space. The S-II put the manned payload into orbit, and the S-IVB was responsible for initially propelling that payload from earth orbit to the moon, an act called “trans-lunar injection” (TLI).
The particular rocket in this display, except for the first stage, is called SA-514. 514 was going to launch the cancelled Apollo 18 and 19 moon missions.
The command/service module (CSM) in the photos is called CSM-119. This particular capsule is unique to the Apollo program, because it has five seats. All the others had three. 119 could launch with a crew of three, and land with five, because it was designed it for a possible Skylab rescue mission. It was later used it as a backup capsule for the Apollo-Soyuz Test Project.
Apollo 7 Completes Transposition & Docking Procedures (11 Oct. 1968) — The expended Saturn S-IVB stage as photographed from the Apollo 7 spacecraft during transposition and docking maneuvers at an approximate altitude of 125 nautical miles, at ground elapsed time of three hours and 16 minutes (beginning of third revolution). This view is over the Atlantic Ocean off the coast of Cape Kennedy, Florida. The Florida coastline from Flagler Beach southward to Vero Beach is clearly visible in picture. Much of the Florida peninsula can be seen. Behind the open panels is the Gulf of Mexico. Distance between the Apollo 7 spacecraft and the S-IVB is approximately 100 feet. The round, white disc inside the open panels of the S-IVB is a simulated docking target similar to that used on the Lunar Module (LM) for docking during lunar missions.
Every rocket has a payload; even the small, solid fuel rocket that I built and fired while attending Space Camp as a child. My rocket launched an earthworm as its payload, carrying it about 1,000 feet above the ground. A parachute opened and brought my payload it back to the ground, alive and unscathed. Obviously, larger rockets tend to carry larger payloads. The Saturn V Moon rocket was the largest launch vehicle ever successfully flown. The whole point of the Saturn V was to lift this, the Lunar Stack, off of Earth, insert it into a brief period of Earth orbit, then push it toward the Moon.
The Lunar Stack consisted of several systems. The very tip of the rocket is a component called the Launch Escape System. This was a tower fixed to the nose of the manned capsule during launch, which contained a solid rocket motor that would be fired if the rocket started to break up, pulling the crew to safety. Luckily, this never had to happen in the Apollo program. If everything was performing nominally, the Launch Escape System would be jettisoned away from the capsule after ignition of the S-II second stage.
The next major system down the line is the Command-Service Module (CSM). This two-part component consists of the Command Module (CM) and the Service Module (SM). The CM carried all three astronauts during the whole flight, from launch, all the way to splash-down, excluding the time when two of the three astronauts would transfer to the Lunar Module (LM) for their excursion to the moon. The particular Command-Service Module pictured here is called CSM-115, which was manufactured for the cancelled Apollo 19 mission. It is only partially completed. Normally, the unflown Command Modules are a shiny silver color, but this module sat outside for decades, and has taken the appearance of one that has suffered an entry into the atmosphere.
The conical structure aft of the CSM is the Spacecraft-Lunar Adapter, which housed and protected the Lunar Module (LM), and the CSM engine during launch. Once the Lunar Stack was on a path to the moon, the CSM would detach from the SLA cone, which would open up like flower petals, exposing the LM. The CSM would turn 180°, dock with the LM, and pull it away from the S-IVB third stage. Then, the CSM and LM would continue their path to the Moon, separate from the S-IVB third stage.
Each small component of the Apollo System, from the launch, to the Escape Tower, and everything in between, is incredible to me. I could go into endless detail about each small component within these systems, but that will have to wait for future articles.
The Apollo 7 spacecraft and Spacecraft launch adapter are seen being lowered on to the S-IVB stage of their Saturn IB rocket. This unique photo shows the forward bulkhead of the liquid Hydrogen tank and the attach points on the forward skirt.
Assembly of the Saturn IB vehicle - including that of Apollo 7 - occurred on the launch pad itself. Cranes and service platforms were located in a massive, inverted U-shaped structure known as the Mobile Service Structure.
Once assembly was complete, the MSS would roll back from the launch mount, exposing the fixed service structure and the vehicle ready for launch.
Apollo-Saturn 201 (AS-201), the first Saturn IB launch vehicle developed by NASA’s Marshall Space Flight Center (MSFC), lifts off from Cape
Canaveral, Florida, at 11:12 a.m. on Feb. 26, 1966. The AS-201 mission
was an unmanned suborbital flight to test the Saturn 1B launch vehicle
and the Apollo Command and Service Modules. This was the first flight of
the S-IB and S-IVB stages, including the first flight test of the
liquid-hydrogen/liquid oxygen-propelled J-2 engine in the S-IVB stage.
During the thirty-seven minute flight, the vehicle reached an altitude
of 303 miles and traveled 5,264 miles downrange.
Apollo 9 Completes First Docking of a Lunar Module (3 March 1969) — The Lunar Module (LM) “Spider”, still attached to the Saturn V third (S-IVB) stage, is photographed from the Command and Service Modules (CSM) “Gumdrop” on the first day of the Apollo 9 Earth-orbital mission. This picture was taken following CSM/LM-S-IVB separation and prior to LM extraction from the S-IVB. The Spacecraft Lunar Module Adapter (SLA) panels have already been jettisoned. Inside the Command Module were astronauts James A. McDivitt, commander; David R. Scott, command module pilot; and Russell L. Schweickart, lunar module pilot.
Johnson Space Center has one of three remaining flight-worthy Saturn V rockets in the world. Of those three, Johnson’s display is the only one that consists of flight-worthy stages. Displays at Kennedy and Marshall consist of a mix between flight-worthy and test stages.
Its first stage is S-IC-14, second is S-II-15, and third S-IVB-13. The first and second stage of Saturn V-13, S-IC-13 and S-II-13 lofted the Skylab space station to orbit. Since the orbiting workshop took place of the vehicle’s third stage, S-IVB-13 remained on the ground.
Boilerplate 115A represents the Apollo spacecraft, and was an unused test vehicle.
is a photograph taken from the Apollo 8 spacecraft looking back at the
Saturn V third (S-IVB) stage from which the spacecraft had just
separated following trans-lunar injection. Attached to the S-IVB is the
Lunar Module Test Article (LTA) which simulated the mass of a Lunar
Module (LM) on the Apollo 8 lunar orbit mission. The 29-feet panels of
the Spacecraft LM Adapter which enclosed the LTA during launch have
already been jettisoned and are out of view. Sunlight reflected from
small particles shows the “firefly” phenomenon which was reported by
astronaut John H. Glenn Jr. during the first Earth-orbital flight,
Mercury-Atlas 6 (MA-6) of the Mercury Program.
The AS-204 spacecraft and its Spacecraft Launch Adapter is mated to the S-IVB stage of its Saturn 1B booster. AS-204 was the official designation of the Apollo 1 mission.
The Saturn 1B rocket was, like all rockets from Cape Canaveral at the time, assembled on the launch pad itself. A Mobile Service Structure would roll to the launch mount, where cranes would then hoist the vehicle to a vertical position. The process would be repeated until the vehicle was assembled. This process is still undertaken by the Delta IV vehicles today.
Saturn V rockets (and Skylab Saturn 1B’s) were assembled vertically in the Vehicle Assembly Building and then rolled out to LC-39 on the crawler transporter. AS-204 would be the second to last assembly of a planned crewed launch vehicle from Cape Canaveral, followed only by AS-205, Apollo 7.