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Saturn V

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Template:Dablink Template:Saturn V infobox

The Saturn V (popularly known as the Moon Rocket) was a multistage liquid-fuel expendable rocket used by NASA's Apollo and Skylab programs. It was the largest production model of the Saturn family of rockets, although NASA contemplated larger models. The rocket was designed under the direction of Wernher von Braun and Arthur Rudolph at the Marshall Space Flight Center, with the lead contractors being The Boeing Company, North American Aviation, Douglas Aircraft Company, and IBM.

On all but one of its flights, the Saturn V consisted of three stages — the S-IC first stage, S-II second stage and the S-IVB third stage. All three stages used liquid oxygen (LOX) as an oxidizer. The first stage used RP-1 for fuel, while the second and third stages used liquid hydrogen (LH2). An average mission used the rocket for a total of about 20 minutes.

NASA launched thirteen Saturn V rockets from 1967 to 1973, with no loss of payload. (Although Apollo 6 and Apollo 13 did lose engines, the onboard computers were able to compensate.) The main payloads of the rocket were the Apollo spacecraft which carried the NASA astronauts to the Moon. It also launched the Skylab space station.

Contents

Background

In the early 1960s, the Soviet Union had developed a considerable lead in the Space Race against the United States. In 1957, the Soviets had launched Sputnik 1, the first artificial satellite. In April 1961, Yuri Gagarin had become the first human to travel into space.

On May 25, 1961, President Kennedy announced that America would try to land a man on the Moon by the end of the decade. At that time, the only experience the United States had with manned spaceflight was the 15 minute suborbital Freedom 7 flight of Alan Shepard. No rocket in the world could launch a spacecraft to the Moon in one piece. The Saturn I was in development, but had not yet flown, and due to its small size, it would require several launches to place in orbit all the components of a lunar spacecraft.

Early in the planning process, NASA considered three leading ideas for the moon mission: Earth Orbit Rendezvous, Direct Ascent, and Lunar Orbit Rendezvous (LOR). Although NASA at first dismissed LOR (considering that rendezvous had yet to be performed in Earth orbit, let alone in lunar orbit) in the end NASA decided that this would be the quickest and easiest method for achieving Kennedy's goal. See Choosing a mission mode for more information.

The Marshall Space Flight Center (MSFC) in 1960 through 1962 designed rockets that could be used for various missions, starting with the C-1, which they would later develop into the Saturn I. The C-2 rocket never got very far in the design process before MSFC dropped it in favour of the C-3, using 2 F-1 engines on its first stage, 4 J-2 engines for its second stage, and an S-IV stage, using six RL-10 engines. NASA planned to use this rocket as part of the Earth Orbit Rendezvous concept with at least four or five launches needed for a single mission.

However, MSFC was planning an even bigger rocket, the C-4. This would use the S-IVB, a stage with a single J-2 engine. The first stage of the C-4 would also use four F-1 engines. The second stage would be an enlarged version of the second stage of the C-3. This rocket would need only two launches to carry out an Earth Orbit Rendezvous mission.

On January 10, 1962, NASA announced plans to build the C-5. This would have five F-1 engines on its first stage, five J-2 engines on its second stage and an S-IVB third stage. The first four flights would be tests, successively testing the three stages, with the last test flight an unmanned circumlunar mission. The first manned flight would not be until 1969 (though, in the end, the first manned flight occurred in December 1968).

In the middle of 1962, NASA decided to use an all-up testing scheme, with all three stages tested at once on the very first launch. This would shorten the testing and development timeline, but mean that all the stages would have to work perfectly. It would also reduce the required number of rockets from 25 to 15. In 1963, the C-5 was renamed Saturn V. Also in 1963, Rocketdyne produced the first engines. In 1966, the F-1 passed NASA's first article configuration inspection with complete qualification for manned missions coming on September 6. After intensive design and testing of several years, the rocket was first launched on November 9, 1967 with the Apollo 4 unmanned spacecraft on board.

Technology

The Saturn V is arguably one of the most impressive machines in human history. Over 110 m high and 10 m in diameter, with a total mass of three thousand metric tonnes and a payload capacity of 118,000 kg to LEO, the Saturn V dwarfed and overpowered all other previous rockets which had successfully flown. It gives a good idea of the scale of Saturn V to note that, at 364 feet, it is just one foot shorter than St Paul's Cathedral in London.

Saturn V was designed by the Marshall Space Flight Center in Huntsville, Alabama. It used the new powerful F-1 and J-2 rocket engines for propulsion. Designers decided early on to attempt to use as much technology from the Saturn I program as possible. As such, the S-IVB third stage of the Saturn V was based on the S-IV second stage of the Saturn I. The instrument unit that controlled the Saturn V shared characteristics with that carried by the Saturn I.

Stages

Missing image
Saturn_v_schematic.jpg
Saturn V diagram

Saturn V consisted of three separate stages and the instrument unit, which were developed by various contractors of NASA. Interestingly all three stage contractors are now owned by Boeing through mergers and takeovers.

All three stages also used small solid-fuelled ullage motors that helped to separate the stages during the launch, and to ensure that the liquid propellants were in a proper position to be drawn into the pumps.

In the event of an abort requiring the destruction of the rocket, the range safety officer would send the signal for shaped explosive charges attached to the outer surfaces of the rocket to detonate. These would make cuts in fuel and oxidiser tanks to disperse the fuel quickly and to minimise mixing. After the Launch Escape Tower had been jettisoned the charges were made safe.

S-IC first stage

Missing image
Ap8-68-HC-70.jpg
The first stage of Apollo 8 Saturn V being erected in the VAB on February 1, 1968

The S-IC was built by The Boeing Company at the Michoud Assembly Facility, New Orleans, where the Space Shuttle External Tanks are now constructed. As with almost every rocket stage, most of its mass of over two thousand metric tonnes at launch was fuel, in this case RP-1 rocket fuel and liquid oxygen oxidiser. It was 42 meters tall and 10 meters in diameter, and provided 33.4 MN of thrust to get the rocket through the first 61 kilometers of ascent. The five F-1 engines were arranged in a cross pattern. The center engine was fixed, while the four on the outer ring could be hydraulically turned to control the rocket.

S-II second stage

The S-II was built by North American Aviation at Seal Beach, California. Using liquid hydrogen and liquid oxygen, it had five J-2 engines in a similar arrangement to the S-IC. The second stage accelerated the Saturn V through the upper atmosphere with 5 MN of thrust. When loaded with propellant, 97% of the weight of the stage was propellant. Instead of having an intertank structure to separate the two fuel tanks as was done in the S-IC, the S-II used a common bulkhead that was constructed from both the top of the LOX tank and bottom of the LH2 tank. It consisted of two aluminium sheets separated by a honeycomb structure made of phenol. This had to insulate against the 70 C temperature difference between the two tanks. The use of a common bulkhead saved 3.6 tonnes in weight.

Missing image
Saturn_V_IU.jpg
The Instrument Unit for the Apollo 4 Saturn V

S-IVB third stage

The S-IVB was built by the Douglas Aircraft Company at Huntington Beach, California. It had one J-2 engine and used the same fuel as the S-II. This stage was used twice during the mission: first for the orbit insertion after second stage cutoff, and later for the trans lunar injection (TLI) burn. The S-IVB also used a common bulkhead to insulate the two tanks. The S-IVB was the only rocket stage of the Saturn V small enough to be transported by plane, in this case the Super Guppy. Apart from the interstage adapter, this stage is nearly identical to the second stage of the Saturn IB rocket.

Instrument unit

The Saturn V Instrument Unit was built by IBM and rode atop the third stage. It was constructed at the Space Systems Center in Huntsville. This computer controlled the operations of the rocket from just before liftoff until the S-IVB was discarded. It included guidance and telemetry systems for the rocket. By measuring the acceleration and vehicle attitude, it could calculate the position and velocity of the rocket and correct for any deviations.

Comparisons

The  engines of the S-IC first stage engines dwarf their creator, .
Enlarge
The F-1 engines of the S-IC first stage engines dwarf their creator, Wernher von Braun.

The Soviet counterpart of the Saturn V was the N-1 rocket. It was even bigger than the Saturn V, but never made it even to first stage separation successfully. The decision to use five very powerful engines for the first stage of Saturn V resulted in a much more reliable configuration than the 30 smaller engines of the N-1. During two launches, Apollo 6 and Apollo 13, the Saturn V was even able to recover from the loss of engines.

The three-stage Saturn V had a peak thrust of 33.4 MN and a lift capacity of 118,000 kg to LEO. A few newer rockets have been able to challenge the records set by Saturn V:

  • The Soviet Energia was 46 MN heavy-lift booster to deliver up to 120-150 metric tonnes to LEO in the Vulkan configuration. It never flew at this capacity, and it was only launched twice.
  • The Space Shuttle generates a peak thrust of 34.8 MN, although payload capacity to LEO (excl. Shuttle Orbiter itself) is only 28,800 kg.

Currently the most powerful expendable launch system of the U.S. is the Titan IV with a thrust of approximately 17 MN, and a lift capacity of 21,700 kg to LEO and 5,800 kg to a geostationary transfer orbit (GTO) (thus being much weaker than the Saturn V). The European Ariane 5 performs slightly better with the newest versions Ariane 5 ECA delivering up to 12,000 kg to GTO. The Delta 4 Heavy, which launched a dummy satellite on December 21, 2004, has a capacity of 13,100 kg to geosynchronous transfer orbit. It is the most powerful rocket in operation.

Assembly

Missing image
Ap10-KSC-69PC-110.jpg
The Apollo 10 Saturn V during rollout
After the construction of a stage was completed, it was shipped to the Kennedy Space Center. The first two stages were so large that the only way to transport them was by barge. The S-IC constructed in New Orleans was transported down the Mississippi River to the Gulf of Mexico. After rounding Florida, it was then transported up the Banana River to the Vertical Assembly Building (now called the Vehicle Assembly Building). The S-II was constructed in California and so travelled via the Panama Canal. The third stage and Instrument Unit could be carried by the Aero Spacelines Pregnant Guppy and Super Guppy.

On arrival at Vertical Assembly Building, each stage was checked out in a horizontal position before being moved to a vertical position. NASA also constructed large spool shaped structures that could be used in place of stages if a particular stage was late. These spools had the same height and mass and contained the same electrical connections as the actual stages.

NASA decided to use a mobile launch tower, or "crawler", built by Marion Power Shovel of Ohio. This meant that the rocket was constructed on the launch pad in the VAB and then the whole structure was moved out to the launch site by the crawler, which is still used today by the Space Shuttle program. It runs on four double tracked treads, with each 'shoe' weighing 900 kg. This transporter had to keep the rocket level as it travelled the 3 miles (5 km) to the launch site.

Lunar mission launch sequence

The Saturn V carried the Apollo astronauts to the Moon. All Saturn V missions launched from Launch Complex 39 at the John F. Kennedy Space Center. After the rocket cleared the launch tower, mission control transferred to the Johnson Space Center in Houston, Texas.

S-IC sequence

The first stage burned for 2.5 minutes lifting the rocket to an altitude of 61 kilometers and a speed of 8600 km/h. In the process it used 2,000,000 kg of propellant.

Missing image
Apollo_11_launch.jpg
A visible shock wave formed as the Apollo 11 Saturn V encountered Maximum Dynamic Pressure (Max Q) at about 1 minute 20 seconds into the flight (altitude 12.5 km, 4 km downrange, velocity 1,600 km/h).

At seven seconds before launch the first stage ignition sequence started. The center engine ignited first, followed by opposing outboard pairs at 300-millisecond stagger times, so as to reduce the structural loads on the rocket. The moment that full 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 held back somewhat by tapered metal pins being pulled through holes. The latter lasted for half a second. Once the rocket had lifted off it could not safely settle back down onto the pad if the engines failed.

It took about 6 seconds for the rocket to clear the tower. As it moved past the tower, the rocket could be seen to noticeably yaw away from the tower, to ensure adequate clearance. At an altitude of 130 meters the rocket began to roll and then pitch to the correct flight azimuth. From launch until 38 seconds after second stage ignition, the Saturn V would fly a preprogrammed pitch program biased for the prevailing winds during the launch month. The four outboard engines also tilted away from the center, so that if one engine had shutdown early, the thrust of the remaining engines would have been towards the rocket's center of gravity. The Saturn V quickly accelerated, reaching 500 m/s by 2 km in altitude. However, much of the early portion of the flight was spent gaining altitude, with the required velocity coming later.

At about 80 seconds (depending on the actual atmospheric conditions), the rocket reached the point of the flight with the maximum dynamic pressure ("Max Q"). The dynamic pressure on a rocket is proportional to the air pressure around the rocket and the square of the speed. Although the speed is increasing, the air pressure is decreasing as the rocket gets higher. At Max Q the dynamic pressure is at its greatest, decreasing for the remainder of the flight.

At 135.5 seconds the center engine shut down to reduce the acceleration loads on the rocket, since it became lighter as fuel was used. The F-1 engine was not throttlable so this was the easiest method. The crew also experienced their greatest acceleration during the launch phase just before first stage cut off with 4 g (39 m/s²). The other engines continued to burn until either the oxidiser or fuel was depleted as measured by sensors in the suction assemblies. 600 milliseconds after the engine cutoff the first stage separated with the help of the eight solid-retrorockets. This occurred at an altitude of about 62 km. The first stage continued to an altitude of 110 km, then impacted in the Atlantic Ocean about 560 km from the launch pad.

S-II sequence

Missing image
Ap6-68-HC-191.jpg
Still from film footage of Apollo 6's interstage falling away (NASA)

After the S-IC sequence, the S-II second stage burned for 6 minutes and propelled the craft to 185 km and 24,600 km/h, bringing it close to orbital velocity.

The second stage had a two-part ignition process. In the first part, eight solid-fuel rockets ignited for four seconds to give positive acceleration, followed by the five J-2 engines. In the second part, about 30 seconds after the first stage separated, the aft interstage separated from the second stage. This was a precisely controlled maneuver as the interstage could not be allowed to touch the engines and had a clearance of only one meter. At the same time as the interstage separated, the Launch Escape System was jettisoned. See Apollo abort modes for more information about the various abort modes that could have been used during a launch.

About 38 seconds after the second stage ignition, the control guidance of the Saturn V switched from a preprogrammed pitch routine to Iterative Guidance Mode, controlled by the Instrument Unit, based on accelerometers and altitude sensors. If the Instrument Unit took the rocket outside allowed limits the crew could either abort or take control of the rocket using one of the rotational hand controllers in the capsule.

About 90 seconds before the second stage cutoff, the center engine shut down to reduce longitudinal POGO oscillations. A pogo suppressor, first flown on Apollo 14, stopped this pogo motion but the center engine was still shutdown early. At around this time, the LOX flow rate decreased, 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.

There were five sensors in the bottom of each tank of the S-II. When two of these were uncovered, the Instrument Unit would initiate the staging sequence. One second after the second stage cut off it separated and a tenth of a second later the third stage ignited. The S-II impacted about 4200 km from the launch site.

S-IVB sequence

The third stage burned for a further 2.5 minutes, about 12 minutes after launch. The third stage remained attached while the spacecraft orbited the Earth two and a half times in a 'parking orbit' while astronauts examined the spacecraft and rocket to make sure everything functioned nominally.

Unlike with the previous separation, there was no two-stage separation. The interstage between the second and third stages remained attached to the second stage (although it was constructed as part of the third stage).

By 10 minutes 30 seconds into the launch, the Saturn V was 164 km in altitude and 1700 km downrange from the launch site. After about 5 more minutes of burning, the rocket cut off. The spacecraft was now in an orbit of about 180 km by 165 km. This is quite low by Earth orbit standards and would not have remained stable for very long due to interaction between the spacecraft and the Earth's atmosphere. For the two Earth orbit missions of the Saturn V, Apollo 9 and Skylab, the orbit would have been higher. The next two and a half orbits were spent checking out the systems of the spacecraft and preparing the spacecraft for Trans Lunar Injection (TLI).

Missing image
As7-3-1545.jpg
The S-IVB stage from the Apollo 7 flight in Earth orbit. Although Apollo 7 used a Saturn IB booster, the S-IVB stage was used on both the Saturn IB and Saturn V. On Saturn V flights the four Spacecraft/LM Adapter panels would be jettisoned to allow access to the Lunar Module

TLI came about 2 and a half hours after launch, when the third stage reignited to propel the spacecraft to the Moon. The S-IVB burned for almost 6 minutes so that the total spacecraft velocity at cutoff was over 10 km/s, escape velocity.

A couple of hours after TLI the Apollo Command Service Module (CSM) separated from the third stage, turned 180 degrees, and docked with the Lunar Module (LM) which rode below the CSM during launch. The CSM and LM then separated from the third stage.

If it were to remain on the same trajectory as the spacecraft, the booster could have presented a hazard later in the mission, so the remaining propellant in its tanks was vented out of the engine, changing its trajectory. For third stages from Apollo 13 onwards, controllers directed it to impact the Moon. Seismometers left behind by previous missions detected the impacts, and the information helped map the inside of the Moon. Before that, the stages (except Apollo 9 and 12) were directed towards a flyby of the Moon that sent them into a solar orbit. Apollo 9's S-IVB was put directly into a solar orbit.

Apollo 12's S-IVB stage, on the other hand, had a different fate. On September 3, 2002, Bill Yeung discovered a suspected asteroid which he gave the temporary designation J002E3. It appeared to be in orbit around the Earth, and was soon discovered from spectral analysis to be covered in white titanium dioxide paint, the same paint used for the Saturn V. Although the third stages from Apollo 8, 9, 10, 11 and 12 all went into solar orbits, it was decided that the most plausible explanation was that it was the S-IVB stage from Apollo 12. Mission controllers had planned to send it into orbit around the Sun after a flyby of the Moon but the burn after separating from the Apollo spacecraft lasted too long putting it into a barely-stable orbit around the Earth and Moon. In 1971 through a series of gravitational perturbations it is thought to have entered in a solar orbit and then returned to orbit the Earth 31 years later. It left Earth orbit in June 2003.

Later use of Saturn V systems

Missing image
Skylab_launch_on_Saturn_V.jpg
The last Saturn V launch carried the Skylab space station to low Earth orbit in place of the third stage.

The only launch of the Saturn V not related to the Apollo program was the launch of the Skylab space station. In 1968, the Apollo Applications Program was created to look into science missions that could be performed with the surplus Apollo hardware. Much of the planning centered on the idea of a space station. Originally it was planned to use the 'wet workshop' concept where a rocket stage was launched into orbit and then outfitted in space.

This idea was abandoned for the 'dry workshop' concept where a S-IVB stage was converted into a space station on the ground and launched on a Saturn V. In this case of Skylab itself, this S-IVB came from a Saturn IB, with a backup constructed from a Saturn V third stage. This backup is now on display at the National Air and Space Museum. Three crews lived aboard Skylab from May 25, 1973 to February 8, 1974, with Skylab lasting in orbit until May 1979.

It was hoped that Skylab would stay in orbit long enough to be visited by the Space Shuttle during its first few flights. This could have raised the orbit and been used as a base for future space stations. However the Shuttle didn't fly until 1981 and it is now realised that Skylab would have been of little use as it was not designed to be refurbished and replenished with supplies.

The Space Shuttle was initially conceived of as a cargo transport to be used in concert with the Saturn V. The Shuttle would handle space station logistics, while Saturn V would launch components. Lack of funding for a second Saturn V production run killed this plan and left the United States without a heavy-lift booster for the next 30 years (and counting). Some in the U.S. space community have come to lament this situation, as continued production would have allowed the International Space Station to have been lifted with just a handful of launches.

Wernher von Braun and others also had plans for a rocket that would have featured eight F-1 engines in its first stage allowing it to launch a manned spacecraft on a direct ascent flight to the Moon. Other plans for the Saturn V called for using a Centaur as an upper stage or adding strap-on boosters. These enhancements would have increased its ability to send large unmanned spacecraft to the outer planets or manned spacecraft to Mars. The second production run of Saturn Vs (had it happened) would very likely have used the F-1A engine in its first stage, providing a substantial performance boost over the first run. Other likely changes would have been the removal of the fins, since they turned out to provide little benefit when compared to their weight; a stretched S-IC first stage to support the more powerful F-1As; and uprated J-2s for the upper stages. Saturn V was also to be the launch vehicle for the nuclear rocket stage RIFT test program and the later NERVA. U.S. proposals for a rocket larger than the Saturn V from the late 1950s through the early 1980s were generally called Nova. Over thirty different large rocket proposals carried the Nova name.

Cost

From 1964 until 1973, a total of $US6.5 billion was appropriated for the Saturn V, with the maximum being in 1966 with $US1.2 billion. [1] (http://history.nasa.gov/SP-4029/Apollo_18-16_Apollo_Program_Budget_Appropriations.htm)

One of the main reasons for the cancellation of the Apollo program was the cost. In 1966, NASA received its highest budget of $US4.5 billion, about 0.5% of the GDP of the United States at that time. In the same year, the Department of Defense received $63.5 billion. [2] (http://www.house.gov/hasc/about/DODDbudgetauth.html)

Saturn V vehicles and launches

The Saturn V launched day or night in foul weather or fair at the appropriate time to reach its destination as shown in this montage of all launches
Enlarge
The Saturn V launched day or night in foul weather or fair at the appropriate time to reach its destination as shown in this montage of all launches
Serial Number Mission Launch Date Notes
SA-501
Apollo 4 November 9, 1967 First test flight
SA-502
Apollo 6 April 4, 1968 Second test flight
SA-503
Apollo 8 December 12, 1968 First manned flight of Saturn V and lunar orbit
SA-504
Apollo 9 March 3, 1969 Earth orbit LM test
SA-505
Apollo 10 May 18, 1969 Lunar orbit LM test
SA-506
Apollo 11 July 16, 1969 First manned lunar landing
SA-507
Apollo 12 November 14, 1969 Landed near Surveyor 3
SA-508
Apollo 13 April 11, 1970 Mission aborted, crew saved.
SA-509
Apollo 14 January 31, 1971 Landed near Fra Mauro
SA-510
Apollo 15 July 26, 1971 First Lunar Rover
SA-511
Apollo 16 April 16, 1972 Landed at Descartes
SA-512
Apollo 17 December 6, 1972 First and only night launch; Final Apollo lunar mission
SA-513
Skylab 1 May 14, 1973 Two-stage Skylab version
SA-514
Unused
SA-515
Unused

Currently there are three Saturn Vs on display, all displayed horizontally:

Of these three, only the one at the Johnson Space Center consists only of stages that were meant to be launched. The US Space & Rocket Center also has on display an erect full scale model of the Saturn V. The first stage from SA-515 resides at the Michoud Assembly Facility, New Orleans, Louisiana and the third stage was converted for use as backup Skylab and is now on display at the National Air and Space Museum.

A popular, untrue (http://www.space.com/news/spacehistory/saturn_five_000313.html) urban legend, started in 1996, states that NASA has lost or destroyed the blueprints or other plans for the Saturn V. In fact, the plans still exist on microfilm at the Marshall Space Flight Center, though it seems unlikely that future engineers will find that the plans will come in handy after the subsequent 40-plus years of advances in rocket science.

External links

References

da:Saturn 5-raket de:Saturn (Rakete) fr:Saturn V it:Saturn V nl:Saturnus V fi:Saturn V pl:Saturn V pt:Saturno V ru:Сатурн-5 sv:Saturnus V

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