Saturn IB - WikiHQ

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 (, 43,380,000 lb-sec total impulse), with the S-IVB (, 96,000,000 lb-sec total impulse). The S-IB first stage also increased the S-I baseline's thrust from and propellant load by 3.1%. This increased the Saturn I's low Earth orbit payload capability from , enough for early flight tests of a half-fueled Apollo command and service module (CSM) or a fully fueled Apollo Lunar Module (LM), before the larger Saturn V needed for lunar flight was ready.

By sharing the S-IVB upper stage, the Saturn IB and Saturn V provided a common interface to the Apollo spacecraft. The only major difference was that the S-IVB on the Saturn V burned only part of its propellant to achieve Earth orbit, so it could be restarted for trans-lunar injection. The S-IVB on the Saturn IB needed all of its propellant to achieve Earth orbit.

The Saturn IB launched two uncrewed CSM suborbital flights to a height of 162 km, one uncrewed LM orbital flight, and the first crewed CSM orbital mission (first planned as Apollo 1, later flown as Apollo 7). It also launched one orbital mission, AS-203, without a payload so the S-IVB would have residual liquid hydrogen fuel. This mission supported the design of the restartable version of the S-IVB used in the Saturn V, by observing the behavior of the liquid hydrogen in weightlessness.

In 1973, the year after the Apollo lunar program ended, three Apollo CSM/Saturn IBs ferried crews to the Skylab space station. In 1975, one last Apollo/Saturn IB launched the Apollo portion of the joint US-USSR Apollo–Soyuz Test Project (ASTP). A backup Apollo CSM/Saturn IB was assembled and readied for a Skylab rescue mission, but never flown.

The remaining Saturn IBs in NASA's inventory were scrapped after the ASTP mission, as no use could be found for them and all heavy lift needs of the US space program could be serviced by the cheaper and more versatile Titan III family and the Space Shuttle.

History

thumb|"The Saturn IB Story 1966" - Official [[NASA promotional information film reel.]]

In 1959, NASA's Silverstein Committee issued recommendations to develop the Saturn class launch vehicles, growing from the C-1. When the Apollo program was started in 1961 with the goal of landing men on the Moon, NASA chose the Saturn I for Earth orbital test missions. However, the Saturn I's payload limit of to 162 km would allow testing of only the command module with a smaller propulsion module attached, as the command and service module would have a dry weight of at least , in addition to service propulsion and reaction control fuel. In July 1962, NASA announced selection of the C-5 for the lunar landing mission, and decided to develop another launch vehicle by upgrading the Saturn I, replacing its S-IV second stage with the S-IVB, which would also be modified for use as the Saturn V third stage. The S-I first stage would also be upgraded to the S-IB by improving the thrust of its engines and removing some weight. The new Saturn IB, with a payload capability of at least , would replace the Saturn I for Earth orbit testing, allowing the command and service module to be flown with a partial fuel load. It would also allow launching the lunar excursion module separately for uncrewed and crewed Earth orbital testing, before the Saturn V was ready to be flown. It would also give early development to the third stage.

! S-IB (1st stage)

! S-IVB (2nd stage)

! Instrument unit

! Height

! Diameter

! Structural mass

! Propellant

| LOX / RP-1

| LOX / LH<sub>2</sub>

! Propellant mass

! Engines

| 8 × H-1

| 1 × J-2

! Thrust

| sea level

| vacuum

! Burn duration

| 150 seconds

| 480 seconds

! Specific impulse

| sea level

| vacuum

! Contractor

| Chrysler

| Douglas

| IBM

Payload configurations

{| class="wikitable"

! Parameter

! Command and service module

! Apollo 5

! AS-203

! Launch Escape System mass

! Apollo command and service module mass

! Apollo Lunar Module mass

! Spacecraft–LM adapter mass

! Nose cone height

! Payload height

! Total space vehicle height

S-IB first stage

right|thumb|300px|Diagram of the S-IB first stage of the Saturn IB rocket

The S-IB stage was built by the Chrysler corporation at the Michoud Assembly Facility, New Orleans. The four outboard engines were mounted on gimbals, allowing them to be steered to control the rocket. Eight fins surrounding the base thrust structure provided aerodynamic stability and control.

Data from:

S-IVB second stage

right|thumb|300px|Diagram of the S-IVB second stage of the Saturn IB

The S-IVB was built by the Douglas Aircraft Company at Huntington Beach, California. The S-IVB-200 model was similar to the S-IVB-500 third stage used on the Saturn V, with the exception of the interstage adapter, smaller auxiliary propulsion control modules, and lack of on-orbit engine restart capability. It was powered by a single Rocketdyne J-2 engine. The fuel and oxidizer tanks shared a common bulkhead, which saved about ten tons of weight and reduced vehicle length over ten feet.

Instrument unit

right|thumb|The instrument unit, which controlled the Saturn IB and Saturn V

IBM built the instrument unit at the Space Systems Center in Huntsville, Alabama. Located at the top of the S-IVB stage, it consisted of a Launch Vehicle Digital Computer (LVDC), an inertial platform, accelerometers, a tracking, telemetry and command system and associated environmental controls. It controlled the entire rocket from just before liftoff until battery depletion. Like other rocket guidance systems, it maintained its state vector (position and velocity estimates) by integrating accelerometer measurements, sent firing and steering commands to the main engines and auxiliary thrusters, and fired the appropriate ordnance and solid rocket motors during staging and payload separation events.

As with other rockets, a completely independent and redundant range safety system could be invoked by ground radio command to terminate thrust and to destroy the vehicle should it malfunction and threaten people or property on the ground. In the Saturn IB and V, the range safety system was permanently disabled by ground command after safely reaching orbit. This was done to ensure that the S-IVB stage would not inadvertently rupture and create a cloud of debris in orbit that could endanger the crew of the Apollo CSM.

Launch sequence events

{| class="wikitable defaultright col1left"

! Launch event

! scope=col | Time (s)

! scope=col | Altitude (km)

! scope=col | Speed (m/s)

| Guidance reference release

| −5.0

| 0.09

| 0

| First motion

| 0.0

| 0.09

| 0

| Mach 1

| 58.9

| 7.4

| 183

| Maximum dynamic pressure

| 73.6

| 12.4

| 328

| Freeze tilt

| 130.5

| 48.2

| 1587

| Inboard engine cutoff

| 137.6

| 54.8

| 1845

| Outboard engine cutoff

| 140.6

| 57.6

| 1903

| S-IB / S-IVB separation

| 142.0

| 59.0

| 1905

| S-IVB ignition

| 143.4

| 59.9

| 1900

| Ullage case jettison

| 154.0

| 69.7

| 1914

| Launch escape tower jettison

| 165.6

| 79.5

| 1960

| Iterative guidance mode initiation

| 171.0

| 83.7

| 1984

| Engine mixture ratio shift

| 469.5

| 164.8

| 5064

| Guidance cutoff signal

| 581.9

| 158.4

| 7419

| Orbit insertion

| 591.9

| 158.5

| 7426

Acceleration of the Saturn IB increased from 1.24 G at liftoff to a maximum of 4.35 G at the end of the S-IB stage burn, and increased again from 0 G to 2.85 G from stage separation to the end of the S-IVB burn. Mobile Launcher Platform No. 1 was modified, adding an elevated platform known as the "milkstool" to accommodate the height differential between the Saturn IB and the much larger Saturn V. <br />S-IVB stage rests with Skylab underwater training simulator hardware and is on display outdoors at the U.S. Space and Rocket Center in Huntsville, Alabama.

| align=center| SA-212

| colspan="2" |

| Unused. First stage scrapped.<br />S-IVB stage converted to Skylab space station.

| align=center| SA-213

| colspan="2" |

| Only first stage built. Unused and scrapped. The structural integrity of the display, after four decades of weathering, could not be repaired. Dismantling of the vehicle for disposal began by September 14, 2023.

Notes

References

External links

http://www.apollosaturn.com/
http://www.spaceline.org/rocketsum/saturn-Ib.html
NASA Marshall Spaceflight Center,  , 30 September 1972