Apollo (spacecraft)
The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The design was based on the lunar orbit rendezvous approach where two docked spacecraft were sent to the Moon and went into lunar orbit. While the Lunar Module separated and landed, the Command and Service Module remained in orbit. After the lunar excursion, the two craft rendezvoused and docked in lunar orbit before the Command Module returned the crew to Earth. This strategy dictated that only one part of the space vehicle would return with the crew to the Earth's surface. Two additional components complemented the spacecraft stack for space vehicle assembly including a spacecraft, LM adapter and a launch escape system. The expendable single-use spacecraft consisted of a combined command and service module plus an Apollo Lunar Module.
The command module served as the control center for the Apollo spacecraft and living quarters for the three crewmen. It contained the pressurized main crew cabin, crew couches, control and instrument panel, Primary Guidance Navigation and Control System, communications systems, environmental control system, batteries, heat shield, reaction control system to provide attitude control, forward docking hatch, side hatch, five windows, and a parachute recovery system. It was the only part of the Apollo/Saturn space vehicle that returned to Earth intact. North American Aviation built this major part of the Apollo spacecraft which was designed for Earth orbital, translunar, and lunar orbital flight. The vehicle carried three men on missions ranging from low Earth orbit to the Moon itself. Five windows allowed crews to view their surroundings while the heat shield protected them during atmospheric reentry. Parachutes deployed to slow the capsule before it splashed down in the ocean for recovery by naval ships.
The service module was unpressurized and contained a main service propulsion engine and hypergolic propellant to enter and leave lunar orbit. A reaction control system provided attitude control and translational capability while fuel cells with hydrogen and oxygen reactants generated power. Radiators dumped waste heat into space and a high gain antenna facilitated communication. The oxygen was also used for breathing and the fuel cells produced water for drinking and environmental control. On Apollo 15, 16 and 17 it carried a scientific instrument package with a mapping camera and a small sub-satellite to study the Moon. A major portion of the service module was taken up by propellant and the main rocket engine capable of multiple restarts. This engine placed the Apollo spacecraft into and out of lunar orbit and was used for mid-course corrections between the Earth and the Moon. The service module remained attached to the command module throughout the mission until jettisoned just prior to reentry into the Earth's atmosphere.
The Apollo Lunar Module was a separate vehicle designed to land on the Moon and return to lunar orbit as the first true spaceship since it flew solely in the vacuum of space. It consisted of a descent stage and an ascent stage manufactured by the Grumman Aircraft Company. The descent stage contained landing gear, landing radar antenna, descent propulsion system, and fuel to land on the Moon. Several cargo compartments carried items including the Apollo Lunar Surface Experiment Packages ALSEP, the modularized equipment transporter MET used on Apollo 14, the Lunar Rover on Apollo 15, 16 and 17, surface television cameras, tools, and sample collection boxes. The ascent stage held the crew cabin, instrument panels, overhead hatch docking port, forward hatch, optical and electronic guidance systems, reaction control system, radar and communications antennas, ascent rocket engine and propellant to return to lunar orbit. Life support systems supplied two astronauts for up to four to five days on the final three missions.
The Apollo launch escape system was built by the Lockheed Propulsion Company with the purpose to abort the mission by pulling the Command Module away from the launch vehicle in an emergency. Three wires ran down the exterior of the launch vehicle so if signals from any two were lost the system would activate automatically. Alternatively the Commander could activate the system manually using one of two translation controller handles switched to a special abort mode for launch. When activated the LES fired a solid fuel escape rocket and opened a canard system to direct the CM away from the path of a launch vehicle in trouble. If the emergency happened on the launch pad the LES lifted the CM to sufficient height to allow recovery parachutes to deploy safely before coming in contact with the ground. The system carried but never used on four uncrewed Apollo flights and fifteen crewed Apollo Skylab and Apollo-Soyuz Test Project flights.
The spacecraft, LM adapter built by North American Aviation Rockwell was a conical aluminum structure that connected the service module to the Saturn S-IVB rocket stage. It protected the LM, the service propulsion system engine nozzle, and the launch-vehicle-to-service-module umbilical during launch and ascent through the atmosphere. The SLA was composed of four fixed panels bolted to the Instrument Unit on top of the S-IVB stage which were connected via hinges to four panels opening from the top similar to flower petals. Once in space astronauts pressed the CSM/LV Sep button on the control panel to separate the CSM from the launch vehicle. Detonating cord ignited around the flange between the SM and SLA along the joints between the four SLA panels releasing the SM and blowing apart connections. Dual-redundant pyrotechnic thrusters at the lower end of the SLA panels fired to rotate them around the hinges at 30 to 60 degrees per second. A redesign using a spring-loaded hinge release system pushed panels away from the S-IVB at velocity putting them safe distance away by the time astronauts pulled the CSM away rotated it through 180 degrees and came back for docking.
Two uncrewed Command Service Modules one uncrewed Lunar Module and one crewed Command Module were carried into space by Saturn IB launch vehicles for low Earth orbit Apollo missions. Larger Saturn Vs launched two uncrewed CSMs on high Earth orbit test flights the CSM on one crewed lunar mission the complete spacecraft on one crewed low Earth orbit mission and eight crewed lunar missions. After conclusion of the Apollo program four CSMs were launched on Saturn IBs for three Skylab Earth orbital missions and the Apollo-Soyuz Test Project. All flown service modules burned up in the Earth's atmosphere at termination of the missions while command modules and lunar modules had specific dispositions listed in NASA records. The Apollo 5 flight did not carry a CSM with an aerodynamic nose cone fastened to the top of the SLA instead. One panel on Apollo 7 did not fully open to the designed 45 degree angle raising concern about collision during docking and extraction of the LM in a lunar mission.
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Common questions
What were the three main parts of the Apollo spacecraft?
The Apollo spacecraft consisted of a Command and Service Module, an Apollo Lunar Module, and a launch escape system. These components worked together to land astronauts on the Moon and return them safely to Earth.
Who manufactured the Command Module for the Apollo program?
North American Aviation built the Command Module which served as the control center and living quarters for the crew. This module was the only part of the space vehicle that returned to Earth intact after missions ranging from low Earth orbit to the Moon itself.
When did the Apollo program aim to land astronauts on the Moon?
The American Apollo program aimed to land astronauts on the Moon by the end of the 1960s. The strategy involved sending two docked spacecraft to lunar orbit where the Lunar Module would separate and land while the Command and Service Module remained in orbit.
How many windows were installed in the Apollo Command Module?
Five windows allowed crews to view their surroundings during flight through the vacuum of space. These windows provided visibility while the heat shield protected the crew during atmospheric reentry before parachutes deployed for ocean recovery.
Which company produced the Apollo Lunar Module descent stage?
Grumman Aircraft Company manufactured both the descent stage and ascent stage of the Apollo Lunar Module. The descent stage contained landing gear, radar antennas, and fuel to land on the Moon while carrying cargo like the Lunar Rover on later missions.