Apollo CM Seats (Couch-Restraint System)

 The hatch could also be opened in space

The most difficult couch-development problem was the compromise that had to be made to provide adequate crew protection for a land landing (additional to water landing) and to satisfy the operational requirements, simultaneously. High level crew protection would have required huge shileds around the crew members but operational requirements reduced seats to minimal size and weight. /1/

Command Module used the standard aircraft axis system

The Apollo command module crew-couch/restraint and load-attenuation system was required to support and restrain the crewman during mission phases and to limit the load imposed on the crewman during landing.

 There were also sleep restraints available

Component designs evolved when requirements changed and tests were conducted. Advancement in the state of the art for energy-absorbing devices and changes in restraint philosophies for impact protection resulted from the efforts and experiences presented.

1) LEB Floodlight

2) X-X Foot Attenuator Strut

3) Hand Strap

4) Translation Control

5) Rotation Control

6) Internal Viewing Mirror

7) Y-Y Attenuator Strut

8) Commander's Couch (Left)

9) CM Pilot's Couch (Center)

10) LM Pilot's couch (Right)

11) X-X Head Attenuator Strut

12) Floodlight

13) EVA Stabilizer Strut

14) Z-Z Attenuator Strut

15) L Shaped PGA Bags

The Command Module development process dictated that the couch/restraint-harness and load-attenuation devices should be considered as an integral subsystem.

Only the commander (left seat) had the TC (Translation Control) stick

The Apollo Command Module (CM) crew-couch/restraint system was designed to support and restrain three crewmen during all phases of the mission from launch to landing.

TC (Translation Control) - Provides a means of exercising manual control over rectilinear motion of the spacecraft in both directions along the three spacecraft axes. It also provides the capability for manual abort initiation during launch by CCW rotation. Transfer of SC control from PGNCS to SCS is accomplished by CW rotation.

RC (Rotation Control) - Provides a means of exercising manual control of spacecraft rotation in either direction about each axis. Also the RC may be used for manual thrust vector control. It also provides the capability to control spacecraft communications wit a push-to-talk trigger switch.

The load-attenuation devices connected to the couches was designed to control the impact loads imposed on the crew during landing, and to remain nonfunctional during any other phase of the mission.

TC Translation Control

Several too massive body protection systems were scrapped during the development process due to other requirements and nonnecessity.


Couch

The Block II couch consisted of three individual body supports that were attached by pip pins and clamps to a supporting framework.

Couch Parts

The body supports could be folded at the hip joint and knee joint, had provisions for locking the seat pan at two angles other than that of the folded position, were capable of being folded at approximately the shoulder position, and could be detached from the framework for storage.

The body supports also could be detached and folded in flight by a crewman in a pressurized space suit. As in the case of side-hatch EVA, the center body support is detached and stowed under the couch of the spacecraft commander.

 The adjustable headrest

The headrest was adjustable in flight for any size crewman and for any pressure-suit condition.

 The couch

The backpan portion of the body support was constructed of Teflon-coated fiber glass, which would conform to the crewman for comfortable support.

The restraint harness

 
Restraint of the crewman was the same as in the Apollo 7 couch with the six-point harness and the passive heel restraint.

Final design requirements for the Apollo crew-couch/restraint system were as follows.

1. Support: The couch shall support the crewman during all mission phases.

2. Restraint: The crewman shall be restrained, when necessary, during the mission.

3. Mobility: The crewman shall be allowed adequate freedom, while restrained, to perform spacecraft operations.

4. Accommodation: The couch shall accommodate any size crewman between the 10th- and 90th-percentile dimensions as defined in reference 1. No tools or special equipment shall be required for positioning the couch during flight.

5. Operation: Operation of the couch shall be compatible with a crewman in a pressurized space suit.

6. Disassembly: The couch shall be foldable and stowable in flight to increase the interior working volume of the CM for mission operations.

7. Strength: Structurally, the couch shall be adequate to support a crewman under loads imposed by the attenuator system.

 James Burke shows how the CM couch works

The couches were produced by the Weber Aircraft Division of Walter Kidde and Co., Burbank, Calif (who also produced a range of aircraft ejection seats and the ejection seats used for Gemini).

COUCH DESCRIPTION

The couches support the crew during acceleration and deceleration, position the crew at their duty stations, and provide support for the spacecraft's translation and rotation hand controls, lights, and other equipment. A lap belt and shoulder straps are attached to each of the the couches. The couches are individually adjustable units made of hollow steel tubing and covered with a heavy, fireproof fiberglass cloth (Armalon). The couches are supported by a head beam and two side stabilizer beams, which are in turn supported by eight attenuator struts (two each for the Y and Z axes and four for the X axis), which absorb the impact of landing.

 Couch and seat positions

The couches can be folded or adjusted into a number of seat positions. The one used most is the 85-degree position assumed for launch, orbit entry, and landing. The 170-degree (flat-out) position is used primarily for the center couch, so that crewmen can move into the lower equipment bay.

 Armrest positions

The armrests on either side of the center couch can be folded footward so the astronauts from the two outside couches can readilyt slide over them. The hip pan of the center couch can be disconnected and the couch pivoted around the head beam and laid on the aft bulkhead (floor) of the Command Module. This provides room for the astronauts to stand and provides easier access to the side hatch for extravehicular activity.

The three couches are essentially the same. The head rest can be moved 16 cm (6 1/2 inches) up and down to adjust for crewman height. Two armrests are attached to the back pan of the left and right couches. The center couch, which is occupied by the Lunar Module Pilot during launch, has no armrests. The translation and rotation controls can be mounted to any of the four arm rests. A support at the end of each armrest rotates 100 degrees to provide proper tilt for the controls. The couch seat pan and leg pan are formed of framing and cloth, and the foot pan is all steel. The foot pan contains a boot restraint device which engages the boot heel and holds it in place.

Restraint-harness components

The couch restraint harness consists of a lap belt and two shoulder straps which connect to the lap belt at the buckle. The shoulder straps connect to the shoulder beam of the couch. The lap belt buckle is a lever- operated, three-point release mechanism. By pulling a lever, the shoulder straps and right-lap belt strap will be released. The strap ends and buckle have button snaps which are fastened to mating snaps on the controllers and struts to prevent them from floating during zero gravity.


Attenuators

The Block II attenuators (X- and Z-axis) were double-acting or cyclic struts that used the concept of material deformation in the plastic range to achieve energy absorption. Material is deformed by rolling a ring of metal (reaction ring) between an inner and outer tube. When the space between the tubes is less than the diameter of the ring, the ring is forced out of round, thus absorbing energy as it rolls. Because the ring is free to roll in either direction, load attenuation occurs for compression, for tension, and at any position of the strut. The reaction load was controlled by varying the number of reaction rings installed. Heat-treated, high-strength bearing rings are located at each end of the gang of reaction rings to maintain concentricity of the tubes and to control the deflection of the reaction rings. The final design of the cyclic strut was held to a breakout load of 10 percent over nominal and a stroking load of ~t 5 percent of nominal. For the Apollo 10 and subsequent missions, the Z-axis cyclic attenuator was replaced by a combination cyclic attenuator, which was basically a cyclic attenuator in combination with a low-onset device. The low-onset device consists of a slender, hard rod of very uniform diameter onto which a series of washers has been pressed. The washers are forced onto the straight portion of the rod, thus causing the washer to be deformed plastically and thereby maintaining a squeeze on the rod. When the washer is forced to slide along the rod, drag occurs from metal-to-metal friction and energy is absorbed.

The total load (or total energy consumed) is the cumulative effect of all the washers stroking along the rod. If spaces are left between the washers, the load  is increased each time a washer is picked up and pushed along the rod. This incremental loading produces an approximate ramp function of the applied  force, which, for a given mass, reduces the deceleration-onset rate. Thus, the deceleration-onset rate of a mass can be controlled by selecting the appropriate washer spacing, and the magnitude of the deceleration can be controlled by selecting the proper number of washers. Characteristic load curves for the cyclic strut and combined strut are shown in figures 14 and 15, respectively. The ramp-loading effect is produced only during the initial stroke of the attenuator, and the attenuator remains a lower level cyclic attenuator for subsequent stroking.

Because a reversible loading in the Y-axis for the Block I1 vehicle was not needed, the same honeycomb-type attenuator that was used on the Apollo 7 mission was used for all missions.

The TC Translation Control stick worked also as an abort switch

Final design requirements for the Apollo load-attenuation system were as follows.

1. Stroking level: The stroking level of the attenuators shall limit the loads imposed on the crewman during landing. The attenuators shall not allow the couch to move during any mission phase other than landing.

2. Stroking distance: The attenuators shall absorb the landing energy transmitted to the couch within the stroking distance allowed in the CM.

3. Reversibility: The attenuators shall absorb energy in both tension and compression stroking.

CM trop tests

RESOURCES

/1/ NASA TN D-7440 - Ralph E. Drexel and Howard N. Hunter, JSC - APOLLO EXPERIENCE REPORT COMMAND MODULE CREW-COUCH/RESTRAINT AND LOAD-ATTENUATION SYSTEMS - September 1973

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