Into Orbit Around the Moon

After suiting, the Lunar Module Pilot entered the lunar module, the drogue and probe were installed, and the hatch was closed.

Continuing First Men on Moon,
our selection from Apollo 11 Mission Report by NASA Mission Evaluation Team and by The Astronauts: Neil Armstrong, Edwin “Buzz” Aldrin, and Michael Collins published in 1971. The selection is presented in eight easy 5-minute installments. For works benefiting from the latest research see the “More information” section at the bottom of these pages.

Previously in First Men on Moon

Time: July 19, 1969
Place: Lunar Orbit

The digital autopilot was used to initiate the passive thermal control mode at a positive roll rate of 0.3 deg/sec, with the positive longitudinal axis of the spacecraft pointed toward the ecliptic North Pole during translunar coast. (The ecliptic South Pole was the direction used during transearth coast.) After the roll rate had been established, thruster firing was prevented by turning off all 16 switches for the service module thrusters. In general, this method was highly successful in that it maintained a satisfactory spacecraft attitude for long periods of time and allowed the crew to sleep without fear of either entering gimbal lock or encountering unacceptable thermal conditions. However, a procedural refinement in the form of a new computer routine is required to make the operation foolproof from an operator’s viewpoint. * On several occasions and for several different reasons , an incorrect computer-entry procedure was used, resulting in a slight waste of reaction control propellants. Satisfactory platform alinements (program P52, option 3) using the optics in the resolved mode and medium speed were possible during rotation at 0.3 deg/sec.

[* A new routine (routine 64) was available for Apollo 12. -NASA’s Editor]

Lunar Orbit Insertion

A 6-minute service propulsion maneuver was performed, and the spacecraft was inserted into a 169.9- by 60.9-mile orbit, as determined by the onboard computer. Procedurally, this firing was the same as all the other service propulsion maneuvers , except that it was started by using the bank B propellant valves instead of the bank A valves. The steering of the docked spacecraft was exceptionally smooth, and the control of the applied velocity change was extremely accurate, as evidenced by the fact that residuals were only D. 1 ft/sec in all axes.

The circularization maneuver was targeted for a 66- by 54-mile orbit, a change from the 60-mile circular orbit which had been executed in previous lunar flights . The firing was normally accomplished by using the bank A propellant valves only, and the onboard solution of the orbit was 66.1 by 54.4 miles. The ellipticity of this orbit was supposed to disappear slowly because of irregularities in the lunar gravitational field, such that the command module would be in a 60-mile circular orbit at the time of rendezvous. However, the onboard estimate of the orbit during the rendezvous was 63,2 by 56.8 miles, indicating that the ellipticity decay rate was less than expected. As a result, the rendezvous maneuver solutions differed from the preflight estimates.

Lunar Module Checkout

Two entries were made into the lunar module prior to the final activation on the day of landing. The first entry was made at approximately 57 hours g.e.t. on the day before lunar orbit insertion. Television and still cameras were used to document the hatch probe and drogue removal and the initial entry into the lunar module. The command module oxygen hoses were used to provide circulation in the lunar module cabin. A leisurely inspection period confirmed the proper positioning of all circuit breaker and switch settings and of all stowage items. All cameras were checked for proper operation.

Descent Preparation

Lunar module — The crew was awakened according to the flight plan schedule. The liquid cooling garments and biomedical harnesses were donned. In anticipation of the donning, these items had been unstowed and prepositioned the evening before. Following a hearty breakfast, the Lunar Module Pilot transferred into the lunar module to accomplish initial activation before returning to the command module for suiting. This staggered suiting sequence served to expedite the final checkout and resulted in only two crewmembers being in the command module during each suiting operation,

The sequence of activities was essentially the same as that developed for Apollo 10, with only minor refinements. Numerous Manned Space Flight Network simulations and training sessions, including suited operations of this mission phase, ensured the completion of this exercise within the allotted time. As in all previous entries into the lunar module, the repressurization valve produced a loud “bang” when it was positioned to CLOSE or AUTO and when the cabin regulator was off. Transfer of power from the command module to the lunar module and then electrical power system activation were completed on schedule.

The primary glycol loop was activated approximately 30 minutes early, with a slow but immediate decrease in glycol temperature. The activation continued to progress smoothly 30 to 40 minutes ahead of schedule. With the Commander entering the lunar module early, the Lunar Module Pilot had more than twice the normally allotted time to don his pressure suit in the command module. The early power-up of the lunar module computer and inertial measurement unit enabled the ground to calculate the fine gyro torquing angles for aligning the lunar module platform to the command module platform before the loss of communications on the lunar far side. This early alinement added more than an hour to the planned time available for analyzing the drift of the lunar module guidance system.

After suiting, the Lunar Module Pilot entered the lunar module, the drogue and probe were installed, and the hatch was closed. During the ascent-battery checkout, the variations in voltage produced a noticeable pitch and intensity variation in the already loud noise of the glycol pump. Suit-loop pressure integrity and cabin regulator repressurization checks were accomplished without difficulty. Activation of the abort guidance system produced only one minor anomaly. An illuminated portion of one of the data readout numerics failed, and this failure resulted in some ambiguity in data readout. (See 11Electroluminescent Segment on Display Inoperative11 in section 16.)

Following command module landmark tracking, the lunar module was maneuvered to obtain steerable antenna acquisition, and state vectors were uplinked into the primary guidance computer. The landing-gear deployment was evidenced by a slight jolt to the spacecraft. The reaction control system, the descent propulsion system, and the rendezvous radar system were activated and checked out. Required pressurization was confirmed both audibly and by instrument readout.

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