Page 72 - Apollo Moonships

70 On bOard apOllO mOOnships
THE DESCENT STAGE
The lower section of the Lunar Excursion Module (LEM) was the descent stage, which stored the landing engine of the spacecraft, the associated propellant tanks, and different types of exploration equipment. In the J-class missions (Apollos 15, 16, and 17), which used an extended version of the LEM capable of carrying more payload and supporting the crewmen for 75 hours on the moon, the descent stage even housed a Lunar Roving Vehicle (LRV). This section, which weighed two-thirds of the total weight
of the LEM, consisted of five equally sized compartments arranged in a cruciform configuration with decks on the upper and lower surfaces. The center compartment housed the descent engine, while the others contained the fuel and oxidizer tanks that fed it. The outboard compartments were linked by struts, forming triangular bays or quadrants that housed critical components from different LEM’s systems, as well as much of the scientific and exploration equipment that astronauts would require on the moon’s surface. The descent stage was not only a cargo section; it provided support for the manned ascent stage and served as a launch platform when the astronauts took off from the moon. To do this, it stood on four cantilevered but robust landing legs equipped with footpads able to settle and avoid tipping over the LEM on surfaces up to 6° of slope. To protect the entire descent stage from the space environment, it was enveloped in a thermal and micrometeoroid shield similar to that used on the ascent stage.
LUNAR LANDER INCLINATION
The lunar lander Falcon lies in the Hadley-Apennine lunar region on July 31, 1971, with the equipment of quadrant IV partially unloaded. Note that the descent stage sat safely on a steep slope. In fact, the lunar lander was tilted back 6.9° and left 8.6°..
DESCENT STAGE STRUCTURE
1 Aft interstage fitting (2)
2 Thermal and micrometeoroid shield
3 Descent engine compartment
4 Forward interstage fitting (2)
5 Ascent stage egress–ingress platform
6 Reaction control thruster plume deflector
7 LEM/SLA (Saturn V) attachment point (4)
8 Landing gear assembly
9 Landing gear deployment and downlock mechanism
10 Ladder
11 Metallic structural skin (nickel)
12 Fuel tank
13 Modularized Equipment Stowage
5
10
Assembly (MESA) pallet
14 Forward interstage fitting
15 Oxidizer tank
16 Parallel beams
17 Descent engine
QUADRANT IV
This quadrant contained the MESA pallet, an electrical cable cutter, and explosive device batteries.
13
12
14
15 16
18
18 Descent engine skirt
19 End closure bulkhead
20 Fuel tank
This quadrant contained a deployable antenna, batteries from the Electrical Power System (EPS), and space suit backpack spares.
21 Aft interstage fitting 22 Water tank
23 Oxidizer tank
QUADRANT I