The NASA/Grumman Apollo Lunar Module (LM) after descending to the lunar surface from lunar orbit, provides a base from which the astronauts explore the landing site and enables the astronauts to take off from the lunar surface to rendezvous and dock with the orbiting Command and Service Modules (CSM). The LM consists of an ascent stage and a decent stage. Both stages function as a single unit during separation from the CM, lunar decent, and lunar stay. The decent stage serves as a launching platform from which the ascent stage lifts off from the lunar surface. The ascent stage operates independently during the lunar ascent, rendezvous, and docking phase of the Apollo Mission.The ascent and decent stages are joined by four interstage fittings that are explosively severed at staging. Subsystem lines and unbilicals required for subsystem continuity between the stages are either explosively severed or automatically disconnected when the stages are separated.
Ascent Stage
The ascent stage, control center of the LM, is comprised of three main areas: crew compartment, midsection, and equipment bay.
The Ascent StageThe crew compartment and midsection make up the cabin, which has an overall volume of 235 cubic feet. The basic structure is primarily aluminum alloy; titanium is used for fittings and fasteners. Aircraft-type construction methods are used. Skin and web panels are chemically milled to reduce weight. Mechanical fasteners join the major structural assemblies with epoxy as a sealant. Structural members are fusion welded wherever possible, to minimize cabin air pressurization leaks. The basic structure includes supports for thrust control engine clusters and various antennas. The entire basic structure is enveloped by thermal insulation and a micrometeoroid shield.
The ascent stage is designed to:
- Provide a controlled environment for the two astronauts while separated from the CSM.
- Provide required visibility for lunar landing, stay, and ascent; and for rendezvous and docking with the CM.
- Provide for astronaut and equipment transfer between the LM and CM and between the LM and the lunar surface.
- Protect the astronauts and the equipment from micrometeoriod penetration.
Crew Compartment
The crew compartment is the frontal area of the ascent stage; it is cylindrical (92 inches in diameter and 42 inches deep). The Commander's flight station is at the left; the LM Pilot's at the right. The flight-station centerlines are 44 inches apart. For maximum downward vision the upper part of the crew compartment is constructed to extend forward of the lower portion. The area has control and display panels, body restraints, landing aids, a front window for each astronaut, a docking window above the Commander's station and other accessory equipment. Each flight station has an attitude controller, a thrust/translation controller, and adjustable armrests. There is a hatch in the front face assembly of the compartment.
A portable life support system (PLSS) donning station is behind the optical alignment station. Attachment points for an S-band in-flight antenna are provided on the front face assembly and for a rendezvous radar antenna on the upper structural beams of the crew compartment.
The crew compartment deck (flight station floor) measures approximately 36 by 55 inches. Nonflammable Velcro pile is bonded to the deck's top surface; a hooked Velcro on the soles of the astronaut's boots provides a restraining force to hold the astronaut to the deck during zero-g flight. Handgrips, aligned with the forward hatch and recessed in the deck, aid ingress and egress.
The control and display panels contain all devices necessary to control, monitor, and observe subsystems performance. The arrangement of the panels permits either astronaut to fly the LM to the CSM. All panels are canted to facilitate viewing. Six of the panels are in front of the flight stations. The upper two panels -- one inboard of each flight station -- are at eye level. These panels are shock mounted to dampen vibrations. The next two lower panels are centered between the flight stations to enable sharing of the control functions. One of the remaining two front panels is in front of each flight station, at waist height. The Commander's panel contains lighting, mission timer, engine, and thrust chamber controls. The LM Pilot's panel has abort guidance subsystem controls. To the left of the Commander's station are three panels: a five-tier circuit breaker panel at the top, an explosive devices and communications audio control panel, and an earth and lunar orbital rate display panel. To the right of the LM Pilot's station are three panels: the uppermost is a four-tier circuit breaker panel, the center panel contains controls and displays for electrical power, and the bottom panel contains communications controls and displays. The circuit breaker panels are canted to the line of sight so that the white band on each circuit breaker can be seen when the breakers are open.
Forward Hatch
The forward hatch is in the front face assembly, just below the lower display panels. The hatch is used for transfer of astronauts and equipment between the LM and lunar surface, or for in-flight extravehicular activity (EVA) while docked with the CM. The hatch is approximately 32 inches square; it is hinged to swing inboard when opened. A cam latch assembly forces a lip, around the outer circumference of the hatch, into a preloaded elastometric silicone compound seal secured to the LM structure. Cabin pressurization forces the hatch lip further into the seal, ensuring a pressure-tight contact. A handle is provided on both sides of the hatch, for latch operation. To open the hatch, the cabin must be completely depressurized by opening a cabin relief and dump valve on the hatch. When the cabin is completely depressurized, the hatch can be opened by rotating the latch handle. The cabin relief and dump valve can also be operated from outside the LM. Quick-release pins in the latch plate and hinges may be pulled from inside the LM to open the hatch in an emergency.
Windows
The two triangular windows in the front face assembly each have approximately 2 square feet of viewing area; they are canted down to the side to permit adequate peripheral and downward visibility. The docking window above the Commander's flight station has approximately 80 square inches of viewing area and provides visibility for docking maneuvers. All three windows consist of two separated panes, vented to space. The outer pane is of low-strength, annealed material that inhibits micrometeoroid penetration. The outer surface of this pane is coated with 59 layers of blue-red thermal control, metallic oxide, to reduce infrared and ultraviolet light transmission. The inner surface of the outer pane has a high-efficiency, antireflective coating. This coating is also a metallic oxide, which reduces the mirror effect of the widows and increases their normal light-transmission efficiency. The inner pane of each window is of chemically tempered, high-strength, structural glass. The inner pane of the front widows has a seal (the docking window has two seals) between it and the window frame and is bolted to the frame through a metal retainer. The inner pane has the high-efficiency antireflective coating on it outer surface.
All three windows are electrically heated to prevent fogging. The temperature of the windows is not monitored. Heater operation directly affects crew visibility; proper operation is, therefore, visually determined by the astronauts.
A window shade, with an antireflective coating on its outboard side, is provided for each window. Normally, the shade is rolled up at the window edge. A glareshield mounted between each front window and the control and flight display panels reduces window reflection of internal panel lighting.
Equipment Storage
Underneath the control and display panels to the right of the LM Pilot's station is a compartmented cabinet. Equipment used during the mission is stowed in this cabinet. This equipment includes food, personal hygiene items, EVA waist tethers, a camera, camera lens filters, a spare light bulb, and a multipurpose special tool having a modified Allen-head. A similar cabinet to the left of the Commander's station contains a spare Environmental Control Subsystem (ECS) lithium hydroxide canister, waste collection containers, a PLSS lithium hydroxide cartridge, and a PLSS condensate container.
Midsection
From the flight stations, the astronauts have an 18-inch step up into the midsection, which is immediately aft of the crew compartment. Normally, the midsection is not manned; it is transversed by the astronauts upon entering and exiting the LM after docking. The midsection is 54 inches deep and approximately 5 feet high. The internal shape is elliptical, with a minor axis of approximately 56 inches. The midsection houses the ascent engine assembly, part of which protrudes up through the lower deck. ECS components, a water-dispensing fire extinguisher, a container for lunar samples, and life support and communications umbilicals are installed on the right side of the midsection. Along the left side, is the waste management system and an oxygen purge system. This side also contains stowage for food, lunar overshoes, a pilot's reference kit, and miscellaneous containers. Components of the Electrical Power Subsystem (EPS) and the Guidance, Navigation, and Control Subsystem (GN&CS) are mounted on the aft bulkhead. A cylindrical cover protects the accessories section from the protruding part of the engine. The top of the cover is used as a rest position for one of the astronauts and as a platform for initially observing the lunar surface through the overhead (docking) hatch. Above the hatch is a docking tunnel; directly forward of the hatch, PLSS fittings are mounted. These fittings aid the astronauts in donning their PLSS units.
Construction of the midsection is similar to that of the crew compartment, but the midsection has a bulkhead at each end. The aft bulkhead supports the aft equipment bay structure. In addition to the lower deck to which the ascent engine is mounted, there are two others. One of these supports the overhead hatch and the lower end of the docking tunnel; the other, supports the upper end of the docking tunnel and absorbs some of the stresses imposed during docking. All decks are made of integrally stiffened machined aluminum alloy, or reinforced chemically milled web. The exterior structure forms a cradle around the midsection to absorb or transmit all stress loads applied to the ascent stage. Stress loads applied to beams on top of the crew compartment are transmitted through midsection beams, to the aft bulkhead and, in turn, to the interstage fittings. The external structure along the sides of the midsection, supports propellant subsystem storage tanks and S-band steerable and VHF flight antennas. The aft midsection bulkhead supports propellant and ECS tanks, and aft equipment rack assembly and the Reaction Control Subsystem (RCS) two aft thrust clusters. A docking target, used for aligning the LM with the CSM during docking, is mounted on the upper left structure of the midsection exterior.
Overhead Hatch
The overhead hatch, approximately 33 inches in diameter, is at the top centerline of the midsection. When the LM and CM are docked, the hatch permits transfer of astronauts and equpment. The astronauts pass through the hatch, head first. Handgrips in the docking tunnel immediately above the hatch aid in crew and equipment transfer. The hatch has an off-center latch that can be operated from either side of the hatch. The hatch is opened inward by rotating the latch handle 90 degrees. A preloaded elastrometric silicone compound seal is mounted in the latch frame structure. When the latch is closed, a lip near the outer circumference of the hatch enters the seal, ensuring a pressure tight contact. Normal cabin pressurization forces the hatch into its seal. To open the hatch, the cabin must be depressurized by opening a cabin relief and dump valve, which is within the hatch structure. The valve can be operated with a handle on each side of the hatch.
Docking Tunnel
The docking tunnel, immediately above the overhead hatch, provides a structual interface between the LM and the CM to permit transfer of equipment and astronauts without exposure to space environment. The tunnel is 32 inches in diameter and 16 inches long. A ring at the top of the tunnel is compatible with a docking ring on the CM. The CM docking ring has automatic clamping latches. The ring is concentric with the nominal centerline of thrust of the ascent and descent engines. The drogue, a portion of the docking mechanism, is secured below the ring to three mounts in the LM tunnel so that it can mate with the docking probe of the CM. When the CM and LM are docked, the rings are joined; this ensures structural continuity for transmitting midcourse correction and lunar orbit injection stresses throughout vehicle basic structure.
Aft Equipment Bay
The Aft Equipment Bay (NASA Photo #690300)
The aft equipment bay is an unpressurized area formed by the aft midsection bulkhead and the equipment rack, which is cantilevered approximately 33 inches aft of the bulkhead. The equipment rack assembly has integral cold rails that transfer heat from electronic and electrical equipment (components of the GN&CS, EPS, and Communications Subsystems) mounted on the rack. The cold rails are mounted vertically in the rack structural frame. Water-glycol flows through the cold rails.
Two gaseous oxygen tanks and two gaseous helium tanks are secured to the truss members between the midsection aft bulkhead and the equipment rack. ECS and Main Propulsion Subsystem components that do not require a pressurized environment or access by the astronauts are mounted to the outboard side of the aft bulkhead. The equipment rack and the aft bulkhead support the aft RCS thrust clusters.
Copyright 1997, 1998, 1999 by John
Duncan |
