The Apollo Mission Stages

apollo mission stages

The Saturn V rocket consisted of three sections, which included: (1) The command module (CM), which contained astronaut quarters and flight control systems; (2) the service module, for propulsion and spacecraft support; and (3) Eagle, its lunar module – together these comprised the CSM.

On its 27th orbit around the Moon, Columbia docked with the gold-and-black descent stage of LM and brought together Armstrong, Aldrin and Collins before jettisoning it.

First Stage

NASA sent 24 Apollo astronauts to the Moon during its Apollo program of 1960-71, with 12 landing on its surface to help propel America ahead in its space race with Soviet Russia during the Cold War years of 1960-71. Saturn rockets powered this success; each used roughly one million gallons of kerosene, liquid oxygen, and hydrogen as fuel.

NASA needed a rocket 100 times more powerful than Mercury to successfully reach the Moon, consuming over one million gallons of kerosene and liquid oxygen on each launch of Saturn V, its three-stage rocket that launched astronaut John Glenn into space in 1961. To meet this goal, three stages of Saturn V rocket were built that measured as long as a Navy destroyer and weighed over one million pounds; their three stages could each transport four people.

After leaving Kennedy Space Center in Florida, Saturn V completed one full rotation around Earth before firing its third stage J-2 engine to propel Apollo on an orbit towards the Moon – this maneuver, known as translunar injection or TLI, placed Apollo on a free-return trajectory toward lunar gravity that reduced fuel requirements on its return home, providing both time and expense savings.

Once on their lunar-insertion trajectory, Apollo began its descent engine burns to slow its spacecraft down. Once complete, its Lunar Module, or LM, descent engine initiated an elliptical lunar orbit that put it 50,000 feet from the Moon while also blocking communications with mission control in Houston.

As soon as they were unable to contact Earth, astronauts used this time for critical activities that ensured mission success: installing a television camera to relay images back, collecting lunar samples for study by still and motion picture cameras, studying lunar terrain with still and motion picture cameras as well as gathering environmental information by installing solar wind composition experiments, seismic experiment packages and Laser Ranging Retroreflectors.

Second Stage

The second stage was at the core of Saturn V rocket’s design. Combusting liquid hydrogen and oxygen fuel, it generated 33 million newtons (3.4 million kilograms, 7.5 million pounds of thrust) for two and a half minutes to overcome Earth’s gravitational attraction and put Apollo into parking orbit.

The spacecraft consisted of two modules, the Command Module and Lunar Module. The Command Module featured a pressurized cabin with control console, living quarters, navigational controls for astronauts as well as primary propulsion system, communications systems, power supplies, environmental control system and batteries for powering its operation.

It was designed to transport three astronauts on a circumlunar and lunar mission, including landing on the Moon. The Lunar Module (LM), attached to the Command Module, carried surface equipment for landing as well as ladders to aid astronauts on taking their initial steps on lunar soil.

After two hours and 45 minutes of coasting, Saturn’s S-IVB third stage engine was given orders to fire for six minutes and propel LM into orbit around the Moon. The engine used a mixture of high velocity oxygen and low velocity nitrogen fuel in its design to propel it toward lunar space.

As soon as it arrived at Moon orbit, the LM fired two reaction control thrusters to enter a circular orbit at an altitude 69 miles concentric with CSM and began performing maneuvers under direction from its commander to rendezvous and dock with it.

Once docked, Armstrong and Aldrin were able to make TV transmissions between Eagle and Columbia and launch a lunar surface program. After 21.5 hours on the Moon, Armstrong and Aldrin undocked Eagle from both Columbia and their command module’s descent stage; leaving Eagle stranded but easily dockable back with Columbia so the crew could safely return home to Earth.

Separating the ascent and descent stages was accomplished using multiple signal paths and redundant pyrotechnic charges, in order to guarantee its successful separation. If this had failed, astronauts would have become trapped in orbit and in need of a launch escape system to reach safety.

Third Stage

Saturn V’s S-IVB stage was the third element in Apollo rocketry. Manufactured by Douglas Aircraft and equipped with one J-2 rocket engine generating 200,000 pounds of thrust, this upper stage provided access to astronauts traveling towards the Moon via their Command & Service Module (CSM).

Once the first stage burned out, the S-IVB used an intense two-minute burn to speed the CSM and LM away from Earth’s gravity and towards translunar injection. Once attached to the CSM, it performed one and a half Earth orbits before heading toward translunar injection.

To initiate the TLI burn, the S-IVB’s J-2 engine was fired for six and a half minutes to accelerate it to an altitude of around 190 miles and close to an orbital velocity of 24,500 mph – this slingshot maneuver aimed to use Moon gravity’s pull on our spacecraft as fuel is reduced during return trips home from lunar orbit.

As it neared its destination, the S-IVB reoriented itself by firing another set of ullage motors pointing it toward the Moon’s horizon, followed by firing the third set of J-2 engines to put itself into an elliptical lunar orbit.

Once in lunar orbit, the S-IVB was placed to allow for Lunar Module docking so astronauts could return to CSM; once this had taken place, LM could then either fly back toward solar orbit or crash into Moon surface.

Starting with Apollo 13, for this option the S-IVB was aimed to strike against the Moon rather than simply hit Earth; this produced an identifiable seismic event and allowed testing of preloaded seismometers. Otherwise it fell into the Atlantic ocean; part of it was recovered by divers 14,000 feet below.

Lunar Module

The Lunar Module, or “LM”, transported astronauts from and to the Moon. Its pressurized crew compartment dominated the front of spacecraft and included flight stations for both commander and lunar module pilot (LMP). Furthermore, equipment such as television cameras with tripod mounts were included for surface exploration by astronauts using it on surface exploration missions such as Apollo 13, 14 and 15. On Apollo 13, 14 and 15, additional features such as hand-pulled Modular Equipment Transporters that opened like inverted umbrellas on tripods would carry tools and samples during extended moonwalks collected during extended moonwalks.

As soon as the second stage had separated, the Lunar Module began traveling at 28,000 miles per hour under control of its third stage into an Earth parking orbit. Five minutes after this point, however, the S-IVB stage fired again for five minutes to put it into a translunar injection trajectory towards the Moon; for three days during which time ground controllers at Mission Control guided its progress towards lunar orbit.

After taking a short rest period, the CSM and LM parted ways and the former used its ascent engine to climb back into space using its descent stage as a launchpad. Once back in space, however, LM ditched its ascent engine and prepared for its landing on the Moon.

As soon as the LM arrived at the Moon, its astronauts docked it with the CSM, transferred any rocks or soil samples between modules and then started EVAs (extravehicular activities) which typically included pairs conducting multiple activities for up to 15 hours at a time before returning to power up its systems and fire its descent engine for Descent Orbit Insertion which took them 50,000 feet above its surface.

Once astronauts were back aboard the LM, it fired its ascent engine and set course back toward the CSM to dock again. Following some course correction burns, it met up with CSM again and docked, then transferred astronauts and rock samples between spacecraft. Finally, its ascent stage would either fall back onto Earth without incident, or on Apollo 13 it would be intentionally driven into Moon for seismic readings.

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