Search Exo Cruiser

Oct 25, 2015

SM Service Module (Part 10, Apollo Control Systems)

Apollo Service Module (SM) was an important part of the Apollo Command/Service Module (CSM). Nowadays also the new SM which is connected to the Orion capsule is called a service module. Actually Europeans are just now building one (2015).


North American Aviation logo

Apollo Command / Service Module was built by North American Aviation.

James Howard "Dutch" Kindelberger

James Howard "Dutch" Kindelberger was an American aviation pioneer, a leader of North American Aviation in 1934-60.

Kindelberger became the president and general manager of North American Aviation in 1934. He was promoted to chairman and chief executive officer in 1948, with Lee Atwood replacing him as president.

John Leland Atwood

In 1960, Atwood took over as chief executive when Kindelberger retired. Kindelberger remained chairman of the board until his death in 1962. "Under Kindelberger's guidance, North American Aviation broke technological barriers; produced propeller- and jet-powered fighters and bombers, military trainers, rocket engines, and rocket-powered aircraft; and began its role as the prime contractor for the country's space program". Between the years 1935 and 1967, North American Aviation (under Kindelberger's direction) built more military aircraft than any other airplane maker in U.S. history.

Douglas logo

Kindelberger and Atwood were young engineers when they met at Douglas Aircraft Company in 1930, working on the DC-1 and DC-2 transports. They left together in 1934 to join the manufacturing division of North American Aviation, where they became a unique American industrial team. An extroverted "pile-driver" of a man, Kindelberger rose to be president of the company, while Atwood, who was the quiet type became chief engineer.

Curtiss P-40 Warhawks

When the two arrived at North American in 1934, the company had one passenger aircraft on order. Kindelberger managed to get a $1 million order for BT-9 aircraft. Then Britain asked North American to build P-40 fighters. Kindelberger told them he could make a better design, and completed the prototype of the legendary P-51 Mustang in four months; 42,000 aircraft were built by the company by the end of the war.

North American's Inglewood plant with P-51s lined up in final assembly.

After World War II Atwood expected there would be a need for improved rocket engines based on those developed by the Germans for the V-2. The two decided in 1946 to invest $1 million in a rocket engine test facility in Santa Susana, California, and a supersonic wind tunnel at Los Angeles International Airport. This paid off when North American landed the contract to develop the Navaho, a rocket-boosted intercontinental cruise missile.

[During its years of operation at Santa Susana Field Laboratory widespread use occurred of highly toxic chemical additives to power over 30,000 rocket engine tests and to clean the rocket test-stands afterwards, as well as considerable nuclear research and at least four nuclear accidents, which has resulted in the SSFL becoming a seriously contaminated site and offsite pollution source requiring a sophisticated multi-agency and corporate Cleanup Project. A long process has been and is still ongoing (2007) to determine the site contamination levels and locations, cleanup standards to meet, methods to use, timelines and costs, and completion requirements - all still being defined, debated, and litigated.

Santa Susana Field Laboratory

The Santa Susana Field Lab Cleanup Project is a very complex challenge: technically, logistically, politically, legally, and emotionally. Regarding cleanup, the site's current owner is Boeing, with NASA and DOE liable for several parcels within that. On August 2, 2005, Pratt & Whitney purchased Boeing's Rocketdyne division, but declined to acquire SSFL as part of the sale.] /1/

North American SM-64 Navaho was a supersonic intercontinental cruise missile

Navaho allowed North American to develop expertise in rocket engines, inertial navigation systems, and supersonic aerodynamics. This in turn led to securing contracts for many advanced aerospace vehicles in the late 1950s – the X-15 manned hypersonic spaceplane, the Hound Dog missile, and the XB-70 Valkyrie triple-sonic bomber. The XB-70 required the company to develop new materials, welding, and manufacturing processes.

Operating a hand drill at North American Aviation, 1942

Kindelberger died in 1962, and Atwood became chairman of the board. Kindelberger was recently honored in a documentary by filmmaker William Winship. "Pioneers in Aviation: The Race to the Moon", which profiles four of America's legendary aerospace pioneers
whose achievements led the U.S. and the world from the era of open-cockpit biplanes to the very threshold of Space. American Public Television aired this film starting in Spring 2006. The film has previously unreleased interviews, photos, and film footage of "Dutch" (Deutsch) Kindelberger.

YouTube video about Kindelberger: "Boeing History"

Little Joe rocket

In 1959, North American built the first of several Little Joe boosters used to test the launch escape system for the Project Mercury spacecraft.

Apollo launch. using Saturn V launch vehicle

In 1960 the new North American CEO, Lee Atwood, decided to focus on the space program and the company became the prime contractor for the Apollo Command/Service Module. A larger Little Joe II rocket was built to test the Apollo's launch escape system, and the second stage of the Saturn V.

North American F-100 Super Sabre

John Leland Atwood (October 26, 1904 - March 5, 1999) was a prominent engineer and executive in the aerospace industry. He worked as Chief Engineer and Executive at North American Aviation for over 35 years, succeeding Dutch Kindelberger as President and CEO. He developed the P-51 Mustang during World War II, the F-100 jet fighter, the X-15 rocket plane, and oversaw the Apollo program

The North American Aviation plant at Downey, California, developed and produced the Apollo command module.

North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA.

Apollo 1 Block I Command Module disassembled after the fire.

However, the Apollo 1 fire in January 1967 was partly blamed on the North American company. In March, it merged with Rockwell-Standard, and the merged company became known as North American Rockwell.

Chris Kraft (seated) confers with Walt Williams and others during Mercury-Atlas 9.

In an interview August 25, 1989 Lee Atwood said: "In retrospect. I had no idea that the Apollo was going to be inflated with high-pressure oxygen. I've got some letters from various people, Walt Williams and Chris Kraft and others who pretty much acknowledge this."

Space shuttle Atlantis‍‍ '​‍s landing gear are deployed following STS-122

Within two years the new company was studying concepts for the Space Shuttle, and won the orbiter contract in 1972. The company changed its name again to Rockwell International and named its aircraft division North American Aircraft Operations in 1973.

View of a group of North American Aviation (following a 1967 merger, known as North American Rockwell) employees as they assemble components on a portion of a space module from NASA's Apollo program at the company's plant in Downey, California, 1966.


A cylindrical Service Module (SM) supported the Command Module, with a service propulsion engine and an RCS with propellants, and a fuel cell power generation system with liquid hydrogen and liquid oxygen reactants. A high-gain S-band antenna was used for long-distance communications on the lunar flights.

View of the ill-fated Apollo 13 Service Module after separation. 17 April 1970.

On the extended lunar missions, an orbital scientific instrument package was carried. The Service Module was discarded just before re-entry. The initial lunar flight version weighed approximately 51,300 pounds fully fueled, while a later version designed to carry a lunar orbit scientific instrument package weighed just over 54,000 pounds.

Labor activists picket the North American Aviation plant in a photo published June 6, 1941. The workers wanted a rise.

North American Aviation won the contract to build the CSM, and also the second stage of the Saturn V launch vehicle for NASA. Because the CSM design was started early before the selection of lunar orbit rendezvous, the service propulsion engine was sized to lift the CSM off of the Moon, and thus was oversized to about twice the thrust required for translunar flight.

Apollo Block I Command Module with missing docking port

Also, there was no provision for docking with the Lunar Module. A 1964 program definition study concluded that the initial design should be continued as Block I which would be used for early testing, while Block II, the actual lunar spacecraft, would incorporate the docking equipment and take advantage of the lessons learned in Block I development

Apollo Service Module propellant tank locations

The Service Module was an unpressurized cylindrical structure, measuring 24 feet 7 inches (7.5 m) long and 12 feet 10 inches (3.9 m) in diameter. The interior was a simple structure consisting of a central tunnel section 44 inches (1.1 m) in diameter, surrounded by six pie-shaped sectors.

The sectors were topped by a forward bulkhead and fairing, separated by six radial beams, covered on the outside by four honeycomb panels, and supported by an aft bulkhead and engine heat shield. The sectors were not all equal 60° angles, but varied according to required size.


S1. (50°) was originally unused, so it was filled with ballast to maintain the SM's center-of gravity. On the last three lunar landing (I-J class) missions, it carried the Scientific Instrument Module (SIM) which contained a package of lunar orbital sensors and a subsatellite.

Apollo 17 SM Scientific Instrument Module (SIM) bay

S2. (70°) contained the Service Propulsion System (SPS) (see below) oxidizer sump tank, so called because it directly fed the engine and was kept continuously filled by a separate storage tank, until the latter was empty. The sump tank was a cylinder with hemispherical ends, 153.8 inches (3.91 m) high, 51 inches (1.3 m) in diameter, and contained 13,923 pounds (6,315 kg) of oxidizer.

S3. (60°) contained the SPS oxidizer storage tank, which was the same shape as the sump tank but slightly smaller at 154.47 inches (3.924 m) high and 44 inches (1.1 m) in diameter, and held 11,284 pounds (5,118 kg) of oxidizer.

S4. (50°) contained the Electrical Power System (EPS) fuel cells with their hydrogen and oxygen reactants.

Close up of fuel cell bay showing fuel cells located immediately above the H2 and O2 cryogenic tanks (Image Source: NASA)

S5. (70°) contained the SPS fuel sump tank. This was the same size as the oxidizer sump tank and held 8,708 pounds (3,950 kg) of fuel.

S6. (60°) contained the SPS fuel storage tank, also the same size as the oxidizer storage tank. It held 7,058 pounds (3,201 kg) of fuel.

The SM top part or forward fairing contents

The forward fairing (SM top part) measured 2 feet 10 inches (864 mm) long and included the
  • Reaction Control System (RCS) computer,
  • umbilical connection,
  • power distribution block,
  • ECS (Environmental Control System) controller,
  • separation controllers,
  • components for the high-gain antenna, and
  • eight EPS (Electrical Power System) radiators.
The umbilical housing contained the main electrical and plumbing connections to the CM. The fairing externally contained
  • a retractable forward-facing spotlight;
  • an EVA (Extra Vehicular Activity) floodlight to aid the Command Module pilot in SIM film retrieval; and
  • a flashing rendezvous beacon visible from 54 nautical miles (100 km) away as a navigation aid for rendezvous with the Lunar Module (LM).

This SM picture shows the compression pads and cradle for the CM:

The SM was connected to the CM using three tension ties and six compression pads. The tension ties were stainless steel straps bolted to the CM's aft heat shield.

This picture shows the bare CM prior to being attached to the SM that shows the three tension ties coming through the heatshield.

The SM remained attached to the Command Module throughout most of the mission, until being jettisoned just prior to re-entry into the Earth's atmosphere.

The umbilical that connects on the SM side wall vs the CM heat shield.

At jettison, the CM umbillical connections were cut using a pyrotechnic-activated guillotine assembly. Following jettison, the SM aft translation thrusters automatically fired continuously to distance it from the CM, until either the RCS fuel or the fuel cell power was depleted. The roll thrusters were also fired for five seconds to make sure it followed a different trajectory from the CM and faster break-up on re-entry.

Apollo Service Module major parts

  • Length: 24.8 ft (7.6 m)
  • Diameter: 12.8 ft (3.9 m)
  • Mass: 54,060 lb (24,520 kg)
  • Structure mass: 4,200 lb (1,900 kg)
  • Electrical System: three 1.4 kW 30 V DC fuel cells
  • Electrical equipment mass: 2,600 lb (1,200 kg)
  • Spacecraft delta v: 9,200 ft/s (2,800 m/s)

SPS (Service Propulsion System [engine])

An Aerojet employee stands next to a 20,500-pound-force AJ10-137 Service Propulsion System (SPS) engine. The Apollo SPS engine served successfully on all Apollo missions and was used to place the Apollo spacecraft into and out of lunar orbit, and for mid-course corrections between the Earth and moon. Aerojet’s contributions included the SPS, 16 bipropellant reaction control system thrusters on the Lunar Module (LM) and 16 on the Service Module, as well as the propellant tanks for the LM ascent stage.

The engine selected was the AJ10-137, which used Aerozine 50 as fuel and nitrogen tetroxide (N2O4) as oxidizer to produce 20,500 lbf (91 kN) of thrust.
  • Service Propulsion (SPS) engine mass: 6,600 lb (3,000 kg)
  • propellants: 40,590 lb (18,410 kg)
  • thrust: 20,500 lbf (91,000 N)
  • propellants: (UDMH / N2H4) / N2O4
  • ISP: 314 s (3,100 N·s/kg)
The propellants were pressure-fed to the engine by 39.2 cubic feet (1.11 m3) of gaseous helium at 3,600 pounds per square inch (25 MPa), carried in two 40-inch (1.0 m) diameter spherical tanks.

The exhaust nozzle engine bell measured 152.82 inches (3.88 m) long and 98.48 inches (2.5 m) wide at the base. It was mounted on two gimbals to keep the thrust vector aligned with the spacecraft's center of mass during SPS firings. The combustion chamber and pressurant tanks were housed in the central tunnel.

RCS (Reaction Control System [jets])

Four clusters of four reaction control system (RCS) thrusters were installed around the upper section of the SM every 90°.

GSM and LM axes systems.

The sixteen-thruster arrangement provided rotation and translation control in all three spacecraft axes.

R-4D thruster (RCS jet)

Each R-4D thruster generated 100 pounds-force (440 N) of thrust, and used mono-methyl hydrazine (MMH) as fuel and nitrogen tetroxide (NTO) as oxidizer.

RCS Quad

Each quad assembly measured 8 feet (2.4 m) by 3 feet (0.91 m) and had its own fuel tank, oxidizer tank, helium pressurant tank, and associated valves and regulators.

The Lunar Module used a similar four-quad arrangement of the identical thruster engines for its RCS.
  • thrust: two or four x 100 lbf (440 N)
  • Propellants: MMH / N2O4


In 1960, Clay Boyce was assigned to the Aerojet Win Apollo team and, then, became engineering manager of the Apollo Service Propulsion System (SPS) engine development. Here is his story about the AJ10-137 reliability.

Clay Boyce, AJ10-137 engineering manager

// Just before the launch of the Apollo 8 mission, which took the first men out around the moon, Tom Paine was the acting administrator of NASA. He called George Mueller, who was the associate administrator for manned space flight. Paine said,

 “George, are you sure that engine is going to start? Find out.”

Wernher von Braun, Aerospace engineer and space architect, talking to US Vice President Spiro Agnew (left) and George E. Mueller (right), the Associate Administrator of the NASA Office of Manned Space Flight, in the Kennedy Space Center in Cape Canaveral during launch preparations of Apollo 9, (back) Thomas O. Paine, 3rd Administrator of NASA

Mueller sent a team off to study the engine. The results of his study were the reason I knew the engine would start. Mueller said,

 “There have been over 3,200 starts of that engine in development and qualification. There were only four times it didn’t start, and those were all due to test stand stuff.”

The engine had started every time all through the development and qualification program. When I used to go to my little hometown in north Idaho, which was a long way from the space program, some of guys back there would ask me what I was working on. I told them, and they said,

“What if it doesn’t start?”

I said,

“It’ll start. I’ll lay it out for you. You probably start your car an average of three times a day. In a year, you’ve started it a thousand times. I’ll bet you at least once, it doesn’t go hmmmm, and, then, it’s going to grind a little. That’s one failure in a thousand.”

The specification I was working with was one failure in 5 million starts. So, I knew it was going to work as long as North American Aviation put that electrical cable on correctly. //


I have collected here some pictures and data about the Apollo era SM.



YouTube video: "Command Module Documentary"

YouTube video: "Apollo Command and Service Module"


/1/ Wikipedia

/2/ Youtube

/3/ Apollo archives

* * *

No comments:

Post a Comment