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Jul 30, 2012

The Recovery of Apollo Flight Crew and Command Module

Since the Apollo Command Module rescue operation is rather interesting I add an article about it here. This text is mostly from resource /1/.

Apollo 17 CM rescue - On 19 December 1972, the Apollo 17 crew jettisoned the no-longer-needed Service Module, leaving only the Command Module for return to Earth. The Apollo 17 spacecraft reentered Earth's atmosphere and landed safely in the Pacific Ocean at 2:25 PM, 6.4 kilometres (4.0 mi) from the recovery ship, the USS Ticonderoga. Cernan, Evans and Schmitt were then retrieved by a recovery helicopter (Sikorsky SH-3 Sea King) and were safely aboard the recovery ship fifty-two minutes after landing.


The recovery of Apollo flight crews and Command Modules with their contained lunar materials and mission equipment from the lunar landing missions requires rapid retrieval, maintenance of biological isolation during postflight operations, and special handling equipment for the preservation and preliminary examination of lunar samples prior to their distribution to principal investigators.

The following is a description of the prime recovery equipment and facilities, and the Lunar Receiving Laboratory.


The Recovery Control Room (RCR) at the Mission Control Center (MCC) is the command and control center for all recovery operations.

The Recovery Control Room (RCR)

Mission Control Center (MCC)

Department of Defense (DOD) personnel command and control the recovery forces and NASA personnel interchange recovery information for mission support requirements. Primary command and control functions are exercised through two major Recovery Control Centers (RCC's) - at Kunai, Hawaii (Task Force 130) and at Norfolk, Virginia (Task Force 140). 

Helicopter pickup


Primary Recovery Ship

The primary recovery ship (PRS) is an aircraft carrier-type ship. Its primary purpose is retrieval of the Command Module (CM) and recovery of the astronauts within allowable limits of access/retrieval times in the primary landing area. The PRS is also utilized to support the secondary landing areas on the mid-Pacific recovery line during the translunar coast phase of the lunar landing mission.

USS Ticonderoga (CV/CVA/CVS-14) was one of 24 Essex-class aircraft carriers built during World War II for the United States Navy.

The PRS is provided with specialized equipment in accordance with the requirements of each mission. The specialized equipment and facilities may include search and rescue helicopters with swimmer pelsonnel, medical personnel and facilities, a complete bioastronautic recovery set, firefighting equipment capable of containing hypergolic fuel fires, and communications circuits to coordinate recovery, medical, and public affairs activities. The recovery ship uses existing equipment to hoist the CM onto the spacecraft dolly. 

Support Aircraft 

Airborne elements in the primary landing area during recovery operations will include:

* SARAH-equipped helicopters, each carrying a three-man swimmer team, to conduct electronic search. At least one of the swimmers on each team will be equipped with an underwater (Calypso) 35mm camera. 

* A helicopter to carry photographers, as designated by the NASA Recovery Team Leader assigned to the PRS, in the vicinity of the target point. 

* Aircraft to function as communications relay, stationed overhead at the scene of action. 

* HC-130 aircraft with operational AN/ARD-17 (Cook Tracker), three-man pararescue team, and complete  Apollo recovery equipment uprange and one downrange.

Prior to CM entry, an Apollo Range Instrumentation Aircraft is on station near the primary landing area for network support. It is used to support the entry phase and recovery operations if required. 

The recovery helicopters are equipped with "Billy Pugh" Rescue Nets (BIPURN) (above figure) and transport specially trained underwater demolition team swimmers.

Recovery units are equipped with flotation collars for the spacecraft, an auxiliary recovery loop (nylon) to supplement the integral recovery loop attached to the spacecraft for hoisting, an Apollo liferaft, 
isolation garments, disinfectant, an appropriate communication and direction finding equipment. The CM may be in the Stable I position (apex up), or in the Stable II position (apex down).

See also:

YouTube video about Apollo rescue

YouTube video about Apollo 15 splashdown

Apollo 11: Mission Control During Spacecraft Recovery (1969)

U.S.S. Hornet recovers the Apollo 11 Command Module.

Recovery Control Room at Mission Control Center During Apollo 11 Recover


/1/ NASA Apollo Program Office - Report No. M-933-71 - MISSION OPERATION REPORT APOLLO SUPPLEMENT - 1971

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Jul 16, 2012

Lunar Module Windows

Since LM operated in space and was pressurized and was imposed under heavy space radiation of different types and also temperature differences its window design is of some interest. The following text is from references /1/ /2/ and /3/.


The ascent stage was configured with three windows as shown in the following figure.

LM had small windows to save weight

The outer pane is of Vycor glass with a thermal (multilayer blue-red) coating on the outboard surface and an antireflective coating on the inboard surface. The antireflective coating is metallic oxide, which reduces the mirror effects of the windows and increases their normal light-transmission efficiency.

LM Vycor and Chemcor windows

The inner pane of each window is of chemically tempered, high-strength structural glass. It is sealed with a Raco seal (the docking window inner pane has a dual seal) and has a defog coating on the outboard surface and an antireflective coating on the inboard surface. Both panes are bolted to the window frame through retainers. All three windows are electrically heated to prevent fogging.


Two triangular windows in the front-face bulkhead of the forward cabin section provide the required visibility during the descent-, transfer-orbit, lunar-landing, lunar-stay, and rendezvous phases of the mission. Both windows have approximately 2 square feet of viewing area and are canted down and to the side to permit adequate peripheral and downward visibility. Each window consists of two panes separated from each other by a cavity that is vented to the space environment (see the following figure).

LM forward window cross section

Lunar Module forward window

The outer non-structural pane is a micro meteoroid / radiation protective window made from annealed (Vycor) glass. The inner pane is the structural window made from tempered (Chemcor) glass. The outer window is clamped on; the inner window is a "floating" window on a seal constructed from metallic spring surrounded by a Teflon jacket. Both windows on the commander's side (left-hand side) have a landing point designator painted on them that provides the astronaut with the capability to target the desired final landing point.


An overhead docking window on the left side of the vehicle, directly over the commander's head, provides the required visibility during the final phase of the docking maneuver. The docking window has approximately 60 square inches (5 by 12 inches) of viewing area.

LM docking window cross section

LM docking window

The construction of this rectangular window (see the above figure) is similar to that of the two forward windows. One exception is that the inner structural window is not a floating window; it is attached rigidly to the cabin skin by a Kovar edge member bonded to the Chemcor glass and bolted to the cabin structure. Another exception is that the window is curved to match the 92-inch diameter of the cabin skin and is not flat like the forward windows.

All three inner windows have an electrical conductive coating that is used to heat the window and to remove any moisture (fog or ice) that may accumulate during the mission. The electrical connection, which provides the required power of 115 volts ac for the forward windows and 28 volts dc for the docking window, is a spring-loaded contact against the bus bars that are integral to the glass. The original design required that the electrical wire be soldered directly to the bus bar.

VYCOR 7913

VYCOR brand glass is a 96% silica glass that is ideally suited for high temperature applications. VYCOR can be used at continuous temperatures up to 900 °C. Due to its extremely low coefficient of thermal expansion VYCOR also provides excellent thermal shock resistance.

See also:

CHEMCOR 0312 (or Gorilla Glass)

Gorilla Glass isn't a new invention. Actually, the glass, originally named "Chemcor", was developed by Corning in 1960. At that time its only practical application was for use in racing cars, where strong, lightweight glass was needed (and Apollo space vehicles).

See also:

OmniSeal® RACO™ 1100A Series

The OmniSeal RACO 1100A Face Seal is a rugged seal, recommended for extreme static sealing conditions such as those involving cryogenic fluids, ultra high vacuum and positive sealing of light gases. The RACO seal is also used dynamically in marine loading arm swivels and similar applications where high torque and clamping forces are employed. Larger cross sections and diameters are common with this seal design. RACO™ 1100A series are available in internal or external face seal only.

OmniSeal RACO 1100A Face Seal

Iron-nickel-cobalt (Glass-to-metal seal) /4/ /5/

Kovar, an iron-nickel-cobalt alloy, has low thermal expansion similar to glass and is frequently used for glass-metal seals. It can bond to glass via the intermediate oxide layer of nickel(II) oxide and cobalt(II) oxide; the proportion of iron oxide is low due to its reduction with cobalt. The bond strength is highly dependent on the oxide layer thickness and character. The presence of cobalt makes the oxide layer easier to melt and dissolve in the molten glass. A grey, grey-blue or grey-brown color indicates a good seal. A metallic color indicates lack of oxide, while black color indicates overly oxidized metal, in both cases leading to a weak joint.

Kovar (trademark of Carpenter Technology Corporation) is a nickel-cobalt ferrous alloy designed to be compatible with the thermal expansion characteristics of borosilicate glass (~5×10-6 /K between 30 and 200°C, to ~10×10-6 /K at 800°C) in order to allow direct mechanical connections over a range of temperatures. It finds application in electroplated conductors entering glass envelopes of electronic parts such as vacuum tubes (valves), X-ray and microwave tubes and some lightbulbs. The name Kovar is often used as a general term for Fe-Ni alloys with these particular thermal expansion properties. Note the related particular Fe-Ni alloy Invar which exhibits minimum thermal expansion.

Carpenter Technology Corporation


The LM windows had three different coatings applied to the glass (see figure).

LM window coatings

1) ECC (Electrical Conductive Coating)

An electrical conductive coating (ECC) was applied to the outboard surface of each inner pane. An electrical connection was made to the silver bus bar on each side of the window to provide the ECC current. The bus bars on the forward windows were powered at 45 to 76 watts to defog the panel. The inner docking window was smaller and therefore required only 18 to 24 watts to defog the panel.

The ECC was applied evenly on the docking window but unevenly on the forward window to obtain the required electrical power and thermal dissipation needed to defog the panels. The approximate thickness of the ECC was 400 to 700 angstroms for the forward window and 2500 angstroms for the docking window. The original light transmission of the chemically tempered glass before the ECC was applied was approximately 88 percent. After ECC application, light transmission was reduced to approximately 76 percent.

2) HEA (High-Efficiency Antireflection)

To increase the light transmission and decrease the reflection caused by the ECC, an HEA coating was applied to the inboard surface of each inner and outer pane. When a pane was completely coated and a black edge (black velvet paint) was applied to the periphery, the light transmission was increased to approximately 82 percent and the reflection was reduced from approximately 14 percent to 5 percent.

3) BR (Blue-Red)

A final BR coating was applied to the outer surface of each outer pane to restrict the amount of infrared and ultraviolet light to the cabin.


Computer reconstruction of Neil Armstrong’s view out the Lunar Module on Apollo 11, 520 feet above the lunar surface just as he transferred from automatic control to semi-manual “attitude hold” (note his hand reaching for the switch), to fly the vehicle past West crater (visible out the window) to a smooth area for landing. Note the landing point designator, the graded angles on the window that would guide Armstrong’s eye to the computers estimate of a landing spot, and the 1202 program alarm indications on the guidance computer display at lower right. (Image: digitalapollo/ aboutcover.html)

Apollo 14: A View from Lunar Module "Antares"

Buzz Aldrin in front of the left LM forward window


/1/ NASA TN D-7084 - Apollo Experience Report - Lunar Module Structural Subsystem - 1973

/2/ NASA TN D-7439 - Orvis E. Pigg and Stanley P. Weiss, JSC - Apollo Experience Report - Spacecraft Structural Windows - 1973

/3/ Grumman - LMA790-2 - Lunar Module Vehicle Familiarization Manual, LM10-14 - 1969
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Jul 14, 2012

Lunar Module Control Subsystems (Part 8, Apollo Control Systems)

Lunar Module control system was divide to 12 subsystems. We have already described some of them in our previous parts. Here is now a simplified picture of the LM complete control system and its subsystems.

LM Control System. Many LM subsystems were heavily connected to each other. For example the Instrumentation (IS) collected data from all subsystems. This is sown as C.M.S. (connected to many subsystems).

Jul 10, 2012

LEM RCS, Lunar Module Reaction Control Subsystem (Part 7, Apollo Control Systems)

The Reaction Control Subsystem (RCS) consisted of 4 clusters of thrusters (16 all together), fuel feeding system and its control electronics and computers.

Lunar Module (LM) Reaction Control Subsystem (RCS) Thrust Chamber Assembly Clusters (4)

Jul 9, 2012

LEM EDS, Lunar Module Explosive Devices Subsystem (Part 6, Apollo Control Systems)

Lunar Module Explosive Devices Subsystem (EDS) and its control was duplicated as most LM systems were.

Lunar Module (LM) EDS devices locations

Jul 6, 2012

Heat Transport Section of LM ECS (Part 5, Apollo Control Systems)

Lunar Module ECS (Environmental Control Subsystem) included a section called HTS (Heat Transport Section). Its job was to remove excessive heat from mostly electrical circuits and batteries. It did it by circulating water-glycol through cold plates that were placed under those circuits and sublimated the heat to the space using water sublimators.

Typical cold plate with primary and secondary loop connections