Apollo 9 was intended to perform an Earth-orbiting engineering test of the first crewed lunar module, known as LM. Other key objectives were checking of launch vehicle systems, procedures, crewing issues and crew.
Mission goal was the first docking of two spacecraft carrying astronauts into space, known as Spider and Gumdrop respectively by astronauts themselves; much to the displeasure of NASA hierarchy who felt these names weren’t appropriate enough.
Mission Objective 1: Docking of the CSM and LM
Apollo 9 mission’s primary objective was to conduct an engineering test of the Lunar Module (LM). Additionally, active rendezvous and docking maneuvers similar to those planned for Apollo 10 lunar-orbit mission would demonstrate that LM could rendezvous and dock successfully with Command/Service Module (CM).
During the docking procedure, the commander of a CM would push and pull on a large probe protruding from its forward end. When its tip entered a conical drogue on LM, an activated pneumatic system moved three latches from their cocked positions to locked ones before pulling docking tunnel into place and activating 12 other latches for tight pressure bonds between vehicles.
Astronauts had trained extensively for transposition and docking maneuvers, and initially everything looked and felt similar to how it had in their simulators. After some time however, CM Pilot Stu Roosa noticed something was amiss and immediately radioed Houston for assistance. Roosa then called off his attempt to dock and made another try with less success: this time it got closer but just bounced off of him instead of docking.
Once the CM and LM were in lunar parking orbit, its crew would enter the LM to power up and test its systems before replacing hatches and docking equipment. When ready, the LM would separate from its host by using its engine to arc into orbit around the moon before initiating descent towards lunar surface using descent engine while Service Module pilot initiated big engine firestorm to return back into lunar orbit.
On their return journey to CM, the LM descent engine would be fired again to reach their ascent stage. When within 100 miles, the pilot of CM fired their engine and separated both parts from one another before jettisoning their respective ascent stages from their spacecrafts.
Mission Objective 2: Extravehicular Activity (EVA) on the Moon
As with the previous J-series missions, preparation for EVA began almost as soon as Worden and Mattingly woke from their initial post-TEI sleep period. Worden and Mattingly made their first move by methodically working their EVA checklists; by the time they donned their A7LB spacesuits approximately half an hour had passed since EVA launch time.
During their two-hour EVA, the crew utilized MEED to study how gravity affects humans in freefall. They were able to measure and record key factors, including rate of descent in free fall and distance traveled away from LM. Furthermore, rock samples were collected for further lunar geological investigations.
At the conclusion of their EVA, the crew removed and stored various items from the Lunar Module such as a camera, the Lunar Roving Vehicle (LRMV), and Command/Service Module Emergency Equipment Door (MESED). They also conducted several experiments within the Lunar Module itself in order to test equipment and procedures that will be employed on future Apollo lunar surface missions.
Experiments on EVA were essential in helping NASA understand how well the LM could operate in space’s harsh vacuum environment, as well as making improvements to both itself and other spacecraft.
At the time of their return to the LM, the crew did so without incident. CDR and LMP then powered up its systems before deploying its landing gear. Once away from CSM, CDR fired up its descent engine for its journey toward Moon.
The landing in the Sea of Tranquility was one of the most spectacular landings ever witnessed by humanity. The Lunar Module completed a vertical touchdown in just over four minutes – an extraordinary achievement which helped ensure that Apollo program’s goal of landing humans on the Moon before the end of 1960s would be met.
Apollo 9 may not have met traditional definitions of success, but it was still essential in meeting program objectives. It marked the first time ever that an Apollo crew docked their lunar module with the command and service module (CSM), and proved its ability to perform vital functions deep space – just four months before Neil Armstrong and Buzz Aldrin would land on the Moon themselves.
Mission Objective 3: Docking of the CSM and LM
With both spacecraft docked securely in Lunar Orbit, it was time to test an astronaut’s ability to move from one spacecraft to another. For this task, they would open their LM hatch and enter the tunnel between vehicles before pressurising it using umbilical cables and forward hatch opening. To accomplish this task, opening both forward hatches of their vehicle would provide power to release mechanisms for pressurisation of tunnel.
By harnessing the LM’s power, the crew was able to activate both a drogue and tunnel ring on the CM probe, activating twelve latches for creating an airtight tunnel between them both vehicles. After about an hour Roosa noticed some shallow scratches on the drogue assembly which were not expected and reported them back to Mission Control; engineers assessed that their cocked latches may have been scraping against it and thus failing to engage properly.
To correct the problem, Roosa used his drogue again to quickly engage and disengage twelve latches in less than a minute – this time successfully reconnecting them. Once this docking connection had been made, the crew began to collaborate in their work in the new tunnel: powering up LM, unlatching its hatches, and exchanging items between vehicles.
McDivitt and Schweickart conducted various tests over five days, such as their ability to maneuver the LM independently from and back to the CSM, using its descent/ascent engines to simulate lunar surface landing maneuvers, and verify that all aspects were working as designed.
On the seventh day, they prepared to undock. Astronauts Schweickart and McDivitt boarded the LM, and after six hours jettisoned Gumdrop’s descent stage while firing its ascent engine and moving away from Spider. By this point, they had moved away enough that they were about 100 miles below it; giving them ample room to perform simulated lunar landing maneuvers.
Mission Objective 4: Docking of the CSM and LM in Lunar Orbit
To accomplish their objective, astronauts needed to execute several docked vehicle operations in lunar orbit. These included command module docking with the lunar module (LM), transfer between CSM and LM and backup abort maneuvers. Furthermore, crew evaluated LM’s support systems and conducted special tests of its EVA unit allowing astronauts to be self-sufficient during lunar excursions.
Flight Day 4 found Schweickart depressurizing the LM, then exiting through its hatch using the so-called golden slipper foot restraint attached to his foot restraint dubbed by NASA as the PLSS (portable life support system) backpack which would be used on lunar excursions in coming weeks and months. He completed a 37.5 minute spacewalk while testing both EMU (Equipment Monitoring Unit) and PLSS backpack which will be utilized during lunar excursions later on this mission.
McDivitt and Schweickart then used the LM’s descent engine to disengage from the CSM, using its service propulsion system (SPS) engines to maneuver away from and back towards its docked CSM in order to simulate active rendezvous procedures required before and after lunar landing operations.
At this point, Houston told Roosa to attempt the transposition and docking (T&D) process. Houston instructed him to power up the LM, replace its docking latches, retract its reentry probe, and position it against the docking ring on the CSM – until mission control noticed a docking alarm that indicated it hadn’t properly docked with CSM.
Roosa attempted again, this time aligning the LM’s docking mechanism against its SLA panels. Once he realized they weren’t engaged, however, he reversed course and started moving back toward it at about one foot per second; mission control reported it felt like “running right through it.” Finally, though, it retracted its SLA panels and joined up with CM.
Reentry began at T+4 minutes and 46 seconds, 30 seconds before reaching apogee. A drogue parachute was deployed at T+5 minutes 10 seconds, and then the main parachute at T+10 minutes and 14 seconds.