The Saturn II was a series of American

expendable launch vehicle An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are either destroyed during reentry or discarded in space. ELVs typically consist of several rocket s ...

s, studied by

North American Aviation North American Aviation (NAA) was a major American aerospace manufacturer that designed and built several notable aircraft and spacecraft. Its products included: the T-6 Texan trainer, the P-51 Mustang fighter, the B-25 Mitchell bomber, the ...

under a

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedi ...

contract in 1966, derived from the

Saturn V Saturn V is a retired American super heavy-lift launch vehicle developed by NASA under the Apollo program for human exploration of the Moon. The rocket was human-rated, with three stages, and powered with liquid fuel. It was flown from 1 ...

rocket used for the Apollo lunar program. The intent of the study was to eliminate production of the

Saturn IB The Saturn IB (also known as the uprated Saturn I) was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It uprated the Saturn I by replacing the S-IV second stage (, 43, ...

, and create a lower-cost heavy launch vehicle based on Saturn V hardware. North American studied three versions with the

S-IC The S-IC (pronounced S-one-C) was the first stage of the American Saturn V rocket. The S-IC stage was manufactured by the Boeing Company. Like the first stages of most rockets, most of its mass of more than at launch was propellant, in this cas ...

first stage removed: the INT-17, a two-stage vehicle with a

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never m ...

payload capability of ; the INT-18, which added

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fiction ...

UA1204 or UA1207 strap-on

solid rocket booster A solid rocket booster (SRB) is a large solid propellant motor used to provide thrust in spacecraft launches from initial launch through the first ascent. Many launch vehicles, including the Atlas V, SLS and space shuttle, have used SRBs to giv ...

s, with payloads ranging from to ; and the INT-19, using solid boosters derived from the

Minuteman Minutemen were members of the organized New England colonial militia companies trained in weaponry, tactics, and military strategies during the American Revolutionary War. They were known for being ready at a minute's notice, hence the name. Mi ...

missile first stage. For this study, the

Boeing The Boeing Company () is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, telecommunications equipment, and missiles worldwide. The company also provides leasing and ...

company also investigated configurations designated INT-20 and INT-21 which employed its S-IC first stage, and eliminated either North American's

S-II The S-II (pronounced "S-two") was the second stage of the Saturn V rocket. It was built by North American Aviation. Using liquid hydrogen (LH2) and liquid oxygen (LOX) it had five J-2 engines in a quincunx pattern. The second stage accelerated ...

second stage, or the

Douglas Douglas may refer to: People * Douglas (given name) * Douglas (surname) Animals * Douglas (parrot), macaw that starred as the parrot ''Rosalinda'' in Pippi Longstocking * Douglas the camel, a camel in the Confederate Army in the American Civi ...

S-IVB The S-IVB (pronounced "S-four-B") was the third stage on the Saturn V and second stage on the Saturn IB launch vehicles. Built by the Douglas Aircraft Company, it had one J-2 rocket engine. For lunar missions it was fired twice: first for Earth ...

third stage. Budget constraints led to cancellation of the study and exclusive use of the

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...

for orbital payloads.

Concept

There was a large payload gap between the

capacity and the

's capability. In the mid-1960s NASA's

Marshall Space Flight Center The George C. Marshall Space Flight Center (MSFC), located in Redstone Arsenal, Alabama ( Huntsville postal address), is the U.S. government's civilian rocketry and spacecraft propulsion research center. As the largest NASA center, MSFC's first ...

(MSFC) initiated several studies to extend the capabilities of the Saturn family. NASA specified a LEO of , 28° inclination for payload calculations, and the studies examined a number of Modified Launch Vehicle (MLV) configurations based on the Saturn IB and Saturn V launch vehicles as well as Intermediate Payload (INT) launch vehicles based on modified Saturn V stages (MS-IC, MS-II, and MS-IVB).

Martin Marietta The Martin Marietta Corporation was an American company founded in 1961 through the merger of Glenn L. Martin Company and American-Marietta Corporation. In 1995, it merged with Lockheed Corporation to form Lockheed Martin. History Martin Ma ...

(builder of

Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...

and

rockets), Boeing (builder of

first stages), and North American Aviation (builder of the S-II second stage) were three of the companies that provided responses. North American believed the best way to fill the gap was to use the Saturn V's second stage, the S-II, as the first stage of an intermediate launch vehicle. The basic concept of the Saturn II was to save money by ceasing production of the

rocket, and replacing it with launch vehicles built entirely with current Saturn V components. This would allow closing down

Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automot ...

Space Division production lines for the

S-IB The S-IB stage was the first stage of the Saturn IB launch vehicle, which was used for Earth orbital missions. It was composed of nine propellant containers, eight fins, a thrust structure assembly, eight H-1 rocket engines, and many other compo ...

first stage, and would allow for more efficient integration of rocket systems.

Design

The baseline for the Saturn II was a Saturn V, without the Boeing-built

first stage. The Saturn V's second stage

became the first stage, and the non-restartable S-IVB-200 used on the Saturn IB became the second stage. Such a vehicle could not fly without modification, because the S-II was designed to operate in the near-vacuum of high altitude space. Atmospheric thrust suppression reduced the five

Rocketdyne J-2 The J-2 is a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch vehicles. Built in the U.S. by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, with each engine produci ...

engines' of vacuum thrust to at sea level, insufficient to lift the weight of the two stages, even without a payload, off of the ground. This required that the S-II be either refit with higher thrust engines, augmented with

s, or both. Another design variable was the amount of the full propellant load carried in the S-II, and in the S-IVB stage. Before any version could be put into production, work on all Saturn variants was stopped in favor of launching all future payloads from the

Saturn INT-17

The Saturn INT-17 was the first version of the Saturn II to be considered. It replaced the first stage's five J-2 engines with seven higher thrust HG-3-SL engines, giving of sea level thrust. It would burn a reduced S-II propellant load of in 200 seconds. The vehicle had a LEO payload capability of with a gross weight of . The reduced payload permitted a savings of in structural weight, and omitting the S-IVB restart capability saved ."Saturn INT-17",Encyclopedia Astronautica
/ref> This configuration was dropped when it was determined that the HG-3-SL could not compete with the J-2 in terms of overall performance, reliability, and cost-effectiveness. This required the addition of booster stages in order to provide more takeoff thrust.

Saturn INT-18

The Saturn INT-18 would have used the standard S-II with J-2 engines, augmented by two or four

SRBs. The UA1204 and

UA1207 UA120 was a family of American solid rocket boosters, manufactured by the Chemical Systems Division of United Aircraft (later United Technologies Corporation). Several variants existed, with a varying number of segments. Design All versions of ...

boosters were considered, with the highest total impulse configuration using four UA1207 boosters, capable of placing of payload into low Earth orbit. Designers considered changing the amount of fuel loaded into the rocket, and whether to ignite the S-II stage on the ground, or whether to launch using the solids, and start the main stage in flight. Two versions omitted the S-IVB stage. The following configurations were studied:

Saturn INT-19

The Saturn INT-19 would have used smaller solid boosters, derived from the first stage of the

missile, to supplement the thrust of the S-II. Eleven configurations were studied, using between four and twelve solids, with some being started at lift-off, and some being started in flight, and varying propellant loads in the Saturn stages. The S-II stage would have been modified by refitting the J-2–SL engines with reduced

expansion ratio The expansion ratio of a liquefied and cryogenic substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at room temperature and normal atmospheric pressure ...

nozzles, to increase sea level thrust to per engine. The highest total impulse configuration would have used twelve boosters, with eight started at launch and four started after the first group had been jettisoned. It would have been capable of lofting a payload of . The following configurations were studied:"Saturn INT-19", Astronautix
/ref>

Notes

References

Encyclopaedia Astronautica Saturn II stageFinal Report - Studies of Improved Saturn V Vehicles and Intermediate Payload Vehicles (PDF format)
October 7, 1966. {{Saturns II