Apollo Mission Diagram
NASA’s Apollo program successfully put men on the Moon in 1969. This chart from NGA’s Aeronautical Chart and Information Center depicts key mission events.
The Columbia was used by astronauts during most of their mission as their living and command center, equipped with an impressive rocket engine to maneuver them into lunar orbit and out again.
The Spacecraft
Project Apollo, conducted by NASA between 1969 and 1972, successfully placed men on the Moon for the first time. It was part of a larger human spaceflight program which also involved one-person Project Mercury and three-person Project Gemini as the initial human voyages into space and back.
Apollo rockets carried both a Command/Service Module (CSM) and Lunar Modules; once at the Moon, these would separate and descend to allow two astronauts to explore its surface before returning back to lunar orbit and making their journey back home.
Each astronaut had their own particular duties during a mission. The Commander (also known as Commander/Command Module Pilot or CDR), for instance, exercised all crew commands during the mission while remaining in the CSM when his companions moved into the Lunar Module (LM). Meanwhile, Lunar Module Pilot or LMP, was responsible for landing on the Moon as well as acting as science officer and flight engineer within this specialized spacecraft.
After three unmanned tests of the Saturn rocket and its components, four manned missions were undertaken. Apollo 1 proved disastrous; with a fire on January 27, 1967 killing astronauts Virgil Grissom, Edward White, and Roger Chaffee before leading to changes in flight procedures implemented for subsequent missions.
Once in lunar orbit, astronauts entered their LM via an interconnecting tunnel. Inside was a cramped capsule about the size of an average car with only enough room for two astronauts at any one time. Once aboard, power was turned up, docking equipment undocked from CSM, call signs were assigned and astronauts used these numbers when communicating with control center during mission activities.
Armstrong and Aldrin utilized an important maneuver during their flight toward the Moon: changing from an orbit that approached perfectly circular to one that was more elliptical in order to prevent collision with its surface.
The Docking Tunnel
The docking tunnel was the port through which astronauts would enter lunar module (LM). I found its engineering quite fascinating, spending many hours gazing upon it at Huntsville’s US Space and Rocket Center. On its left was the probe while on its right stood its conical counterpart drogue; during its docking sequence on Moon, one team would collapse its probe while the other collapsed theirs before popping out from under its tunnel into which a pressure hatch opened between both vessels.
Each maneuver to separate and dock Apollo ships required meticulous timing in order to guarantee safe flight. For instance, depressurisation in the docking tunnel would compromise astronauts’ hatches during separation if it depressurised too rapidly during docking; NASA therefore set a maximum pressure at separation for this tunnel known as “preferred separation pressure”, 2 psi – too much could damage astronauts’ hatches fatally, too little may prevent Lunar Module being moved far enough away, possibly endangering its inhabitants as well.
To do this, the docking tunnel contained a special mechanism which was activated at an appropriate moment by pressing a button on the control panel and detonating a detonating cord which activated an opening in a CSM-LM adapter, unlocking its latches to separate itself from storage near the deck of the payload bay and allow its ring to be pulled up into an incoplanar position by pulling upward against an actuator-attenuator 20 supporting its structure which in turn was pulled downward against an extension spring force of its supporting structure as part of its removal process.
Once the drogue had emerged from its tunnel, the crew would contact Houston via their live TV transmission and report what they witnessed. Next they double-checked all twelve latches connecting LM to CSM as well as pressing one more button to release umbilical lines before stowing together and setting sail towards Moon.
The Service Module
The Apollo service module was the heart and soul of its spacecraft, carrying all of the systems astronauts required for lunar landing – such as life support systems and storage tanks – plus more. Furthermore, it served as the link between command and lunar modules during flight.
The SM was a cylindrical structure measuring 16 feet 7 inches (5.49 meters) wide by 14 feet 10 inches (4.52 meters), featuring an engine nozzle and heat shield at its aft end for service propulsion engine nozzle, with six pie-shaped sectors surrounding a central tunnel section 44 inches (1.11 meter in diameter). A forward bulkhead and fairing were located along its length.
On its exterior, the SM was composed of brazed stainless steel with a thermal blanket covering. It featured an aft end docking tunnel through which Lunar Module would enter for landing on the Moon; tension ties extended from its heat shield onboard the CM to six compression pads on top of SM for holding Lunar Module during reentry.
Once in lunar orbit, astronauts in the Lunar Module would use its engines to return back to its mothership and dock for return home.
Once on the Moon, the crew in the LM would disembark and return to the CSM for docking by inserting a probe from its top into a ring at its rear end; hatches on both modules would then allow passage.
On their journeys to and from the Moon, CM astronauts used CSM’s engine for midcourse corrections, entering lunar orbit, leaving lunar orbit, making an Earth capture, providing oxygen, fuel cells, power-generating equipment as well as life support water for life support circuits after transposition, transfer and docking; they would also use its engine as part of their descent through lunar atmosphere to splashdown in an oceanous location. The LM also utilized this same SM engine during its descent through lunar atmosphere before splashing down onto Earth surface before splashdown in ocean.
The Lunar Module
Lunar Module (LM), one of three primary components of Apollo spacecraft, transported two astronauts from lunar orbit to lunar surface and back, passing through both descent stage and ascent stage stages before returning them back to lunar orbit for further journey. After reaching lunar parking orbit, Commander and Lunar Module Pilot entered their LM through an interconnecting tunnel from Columbia and powered it up. Propulsion came via its descent engine which used hypergolic propellants with adjustable thrust control; its rear bay held the primary guidance, navigation and control system comprised of oxygen/helium tanks for fuel storage; two control actuators; a computer; as well as an Abort Guidance System (AGS) as a backup navigation tool.
Before entering solar orbit, the LM ascent stage was jettisoned, after which both its commander and pilot transferred back to the CM for reentry reorientation, while its landing engine fired to lower its perilune to within 50,000 feet of Moon surface.
On the lunar surface, three probes extending from footpads on the LM touched lunar soil to trigger its contact indicator light and signal it was time to shut off its descent engine and settle on the Moon. Furthermore, its television camera transmitted images back home.
Once the LM had touched down, its Commander and Pilot exited their spacesuits and descended a ladder onto a landing platform. A US flag to be raised on the lunar surface was stored within a Modular Equipment Stowage Assembly (MESA), a drawer which dropped from left side of forward compartment of LM. MESA also held surface excavation tools as well as sample collection boxes used by astronauts during exploration of lunar surface.
The Commander was responsible for controlling the landing and operating the LM’s flight controls, while its pilot handled other systems operations and informed him about LM status. Once visual inspection of landing gear was complete, 30 seconds of engine burning occurred to reduce speed and get within safe distance from Moon, followed by restart of engine for powered descent toward landing site.