Apollo 9: Crewed Orbital Validation of the Lunar Module

Apollo 9 was the lunar module's first crewed flight, conducting about ten days of tests in Earth orbit in March 1969. Commander James McDivitt, Command Module Pilot David Scott and Lunar Module Pilot Russell Schweickart tested two kinds of spacecraft. The crew had to operate the command and service modules and enter the lunar module, then maneuver, rendezvous and redock after separation.

During a lunar mission, the lunar module could not return through the atmosphere to the ground, so its crew ultimately had to rejoin the command module. This test therefore combined crew operations, loads at the connection between the spacecraft, propulsion systems and the route back in a single flight plan. The lunar module used the call sign Spider and the command module Gumdrop, distinguishing radio addressees during separated flight.

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The LM-3 lunar module arrived at Kennedy Space Center from Bethpage in June 1968. Its ascent stage underwent altitude-chamber tests simulating vacuum conditions, and the two stages were repeatedly joined and checked. When cracks were found in the ascent engine, staff replaced it. The command and service modules arrived from Downey in October. Ground work also included docking tests and installation of rendezvous radar, antennas and separation devices.

In January 1969, the assembled vehicle moved to Launch Complex 39, and flight simulations were linked with Mission Control in Houston. Cabin airtightness, power, spacesuits and other equipment underwent separate checks and reviews. The three astronauts developed colds around the planned late-February launch, delaying the mission until they recovered.

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At 16:00 Greenwich Mean Time, or 11:00 U.S. Eastern Standard Time, on 3 March, Saturn V lifted off from Kennedy Space Center, placing the spacecraft in an orbit with a perigee of about 189 kilometers and an apogee of about 192 kilometers. After initial checks, the command and service modules separated from the final rocket stage, turned around to dock with the lunar module, and extracted the joined spacecraft from the launcher.

During the first few days, the crew fired the service module engine several times while docked to observe the combined vehicle's dynamics. On the third day, McDivitt and Schweickart entered the lunar module, activated its systems and conducted a descent-engine burn of about 372 seconds. The test used the digital autopilot for attitude control and also tested manual throttle adjustment, examining the response and interface loads while the spacecraft remained connected.

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On the fourth day, both spacecraft were depressurized and their hatches opened. Wearing a spacesuit and portable life-support backpack, Schweickart moved from the lunar module onto its forward platform, checked handrails, took engineering photographs and retrieved thermal samples. Scott stood with his upper body through the command module's side hatch, relying on spacecraft-supplied life support to observe and recover samples.

Schweickart had been unwell the previous day, and rendezvous preparations were due the following day, so the planned two-hour-and-fifteen-minute EVA was shortened to 47 minutes. He did not transfer externally to the command module, but checked the handrails intended for that route. NASA's mission report judged the spacesuit and extravehicular life-support tests that were performed to have worked well.

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On the fifth day, McDivitt and Schweickart undocked in the lunar module, leaving Scott alone in the command module. The lunar module first used its descent engine to change orbit and relative distance, then discarded the descent stage and fired its ascent engine to adjust its orbit. The primary guidance system conducted the actual rendezvous, while the command module calculated corresponding backup maneuvers to assist recovery if needed.

During final approach, the lunar module used its attitude-control thrusters to close the distance. The spacecraft held a close relative position for photography, then redocked about 99 hours into the flight. Separated flight lasted more than six hours, testing the complete sequence of active pursuit, braking and docking by the lunar module. The mission report recorded lunar-module attitude-control propellant consumption during rendezvous at about 30 percent below prediction.

After both astronauts returned to the command module, the ascent stage was jettisoned. Ground controllers then ran its engine without a crew for about 362 seconds until oxidizer depletion, obtaining additional propulsion-system data.

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During the remaining days, the crew conducted landmark tracking, multispectral photography and service-engine tests, with the multispectral experiment producing 584 images. One burn was delayed by an orbit because of an incorrect autopilot configuration for the propellant-settling maneuver; it was completed after reconfiguration. Another, extended burn tested a propellant-gauging system that had previously shown anomalous readings.

Poor weather in the planned recovery area also delayed the deorbit maneuver by one revolution. At about 17:01 Greenwich Mean Time on 13 March, the command module splashed down in the Atlantic, and helicopters took the crew to USS Guadalcanal. NASA considered all principal objectives achieved: the complete spacecraft had demonstrated in Earth orbit the combined and separated operations needed for a crewed lunar landing. Further validation in the lunar environment remained for subsequent flights.

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