Apollo Expeditions to the Moon
THE DRESS REHEARSAL
Launching was routine, as was the establishment of the Earth
parking orbit that followed. After systems checks, and approval
from Mission Control, the crew fired the S-IVB stage engine to
leave the parking orbit and enter the translunar trajectory. Then
they separated the command and service modules from the S-IVB,
and turned to dock with the lunar module. Ejection of the docked
spacecraft followed, as the crew performed a separation maneuver
to increase the distance between the docked spacecraft and the
S-IVB stage. Then they eased the S-IVB into a solar orbit by
propulsive venting of its excess propellants.
The translunar trajectory had been established so precisely
that it was not necessary to make the first midcourse correction,
generally a routine step during the early phases of the flight
toward the Moon. Finally, after a little more than a day in
flight, a single translunar midcourse correction was done to make
the flight path of Apollo 10 coincide with the trajectory planned
for the Apollo 11 mission. Three days and four hours away from
the launch pad, the crew fired the service propulsion system for
almost six minutes, inserting the spacecraft into a lunar orbit.
Apollo 10 now was orbiting the Moon in a circular flight path
about 60 miles above its surface.
Stafford and Cernan entered the lunar module about six hours
later to check the systems. They transferred some needed
equipment, and moved back into the command module for a normal
sleep period. They then recentered the lunar module to go through
a complete systems check to prepare for the lunar-orbit
rendezvous, the final check of the flight mechanics of the Apollo
Just after two hours into the fourth day, the two spacecraft
were undocked and separated. The crew performed its routine
communications and radar checks, and then Stafford and Cernan
began their descent toward the lunar surface by firing the
descent stage engine. They let down to an altitude of about eight
miles above the surface, the closest they were to go in that
mission. Over one of the selected landing sites, they checked the
landing radar, which worked successfully. After this descent,
Stafford and Cernan maneuvered the LM into an elliptical orbit.
11 by 190 miles, to establish the conditions for their rendezvous
with Young in the command module. They completed one swing around
the Moon? and then staged the lunar module, firing its ascent
engine in a simulation of a return from the lunar surface.
These words read rapidly, as if the performance they
describe were done swiftly. But it must be appreciated that this
rehearsal, which was planned to follow the schedule for the
Apollo 11 as closely as possible, actually took more than six and
one-half hours from the beginning of the descent toward the Moon
until both spacecraft had docked for the second time for crew
transfer back to the CSM.