13.0 LAUNCH PHASE SUMMARY
13.1 WEATHER CONDITIONS
Gentle to moderate southerly winds extended from the surface to an
altitude of 25 000 feet at launch time. The maximum wind was 37 knots at
45 000 feet. Broken thin cirrostratus; clouds covered much of the sky at
25 000 feet, but no low or middle clouds were observed. Surface
temperature was 83 F and visibility was 10 miles.
13.2 ATMOSPHERIC ELECTRICITY
The Apollo 15 launch complex was struck by lightning on five different
days during the checkout activities. In all, eleven separate strikes were
recorded between June 14 and July 21, 1971. The direct damage incurred was
limited to the command and service module ground support equipment.
Launch site lightning strikes have not been documented for program
other than Apollo and Gemini. Incidents reported for these two programs
are as follows:
a. On August 17, 1964, a lightning strike occurred near, but not
directly on, launch complex 19. The Gemini II vehicle was visually
inspected and found to be free of lightning-type markings or burns. Later,
some failed components were discovered which were believed to have
resulted from the lightning incident.
Existing weather data were examined for the May-through-July periods
from 1966 to the launch of Apollo 15. Reported cloud-to-ground lightning
strikes for a period of 90 days within the general vicinity of Cape Kennedy
showed the daily average to be as follows:
b. The first Apollo strike occurred in September 1964. The launch
umbilical tower was struck on launch complex 34 while the S-I launch
vehicle was being prepared for flight. No failures were reported.
c. The second, and final, Gemini incident was a strike near the
launch complex 19 power facility during the Gemini V countdown on
August 19, 1965. No lightning-related damage was reported.
d. At least one lightning strike occurred on the mobile launcher
for the AS-201 vehicle. This occurred sometime between August 9 and
August 27, 1965, at launch complex 39. Only the S-IB stage of the space
vehicle could have been on the pad at the time and no lightning damage
e. At least two strikes were recorded on the mobile launcher for
the AS-50OF vehicle at launch complex 39A. This was a non-flight facility
test vehicle. The first incident occurred on May 27, 1966. On June 21, 1966,
magnetic recording links on the mobile launcher were examined and the reading
indicated at least one strike had occurred between
May 27 and June 21, 1966. During this time, the complete launch vehicle
for the AS-202 mission was on launch pad 37B and the complete launch vehicle
for the AS-203 mission was on launch pad 34. No lightning activity
associated with the latter two complexes was reported.
f. On July 27, 1967, a lightning strike occurred at launch complex
37B. The complete launch vehicle was on the pad at the time of the incident.
Ground support equipment damage was found at a later date, which
may have been caused by the lightning.
g. The only other lightning strike reported prior to the Apollo 15
prelaunch activities occurred during the launch phase of the Apollo 12
mission. This occurrence is documented in reference 6.
Thunderstorms are more prevalent on the west side of the Indian River
and remain west of the launch pad. During the summer of 19T1, however,
the west winds prevailed more frequently than the preceding several years,
thus causing the thunderstorms to move east. The lightning density in
conjunction with the general easterly movement of the storms contributed
to the number of strikes being higher than in the past.
13.3 LAUNCH VEHICLE PERFORMANCE
The eighth manned Saturn V Apollo space vehicle, AS-510, was launched
on an azimuth 90 degrees east of north. A roll maneuver was initiated at
12.2 seconds after lift-off and the vehicle was placed on a flight azimuth
of about 80 degrees. The trajectory parameters from launch through translunar
injection were nominal. Earth-parking-orbit insertion conditions
were achieved 4.4 seconds earlier than planned.
The performance of the S-IC propulsion system was satisfactory and
the specific impulse and mixture ratios were near the predicted values.
Four of the eight S-IC retromotors and all of the S-II stage ullage
motors were removed for this flight; therefore, the S-IC/S-II separation
sequence was revised. This sequence change extended the coast period
between S-IC outboard engine cutoff and S-II engine start command by one
second. The S-IC/S-II separation sequence and S-II engine thrust buildup
performance was satisfactory.
The S-II propulsion system performed normally. The specific impulse
and mixture ratios were near predicted values. This was the second S-II
stage to incorporate a center-engine liquid-oxygen feedline accumulator as
a longitudinal oscillation (POGO) suppression device. The operation of the
accumulator system was effective in suppressing these types of
The S-IVB stage J-2 engine operated satisfactorily throughout the
first and second firings and had normal start and cutoff transients. The
firing time for the first S-IVB firing was 141.5 seconds, 3.8 seconds less
than predicted. Approximately 2.6 seconds of the shorter firing time can
be attributed to higher than predicted S-IVB performance. The remainder
can be attributed to S-IC and S-II stage performances. The specific
impulse and engine mixture ratio were near the predicted values.
Abnormal temperatures were noted in the turbine hot gas system between
the first S-IVB firing engine cutoff and second firing engine start
command. Most noticeable was the fuel turbine inlet temperature. During
liquid hydrogen chilldown, this temperature decreased from +130 to -100 F
at the time of the second engine start command. The oxidizer turbine inlet
temperature also indicated a small decrease. In addition, the fuel turbine
inlet temperature indicated an abnormally fast decrease after engine cutoff
for the first firing. A possible cause of the decrease in turbine inlet
temperature was a small leak past the gas generator fuel inlet valve.
The S-IVB firing time for translunar injection was 350.8 seconds. Upon
completion of the spacecraft separation, transposition, docking, and
extraction operations, the S-IVB evasive maneuver was performed and,
subsequently, the vehicle was placed on a trajectory to impact the lunar
surface in the vicinity of the Apollo
14 landing site. The S-IVB/instrumentation
unit impacted the lunar surface at 1 degree 31 minutes
south latitude and 11 degrees 49 minutes west longitude with a velocity of
8455 ft/sec. This impact point is approximately 146 kilometers (79 miles)
from the target of 3 degrees 39 minutes south latitude and 7 degrees 35
minutes west longitude. Although the impact location was not within the
preferred region, scientific data were obtained from the impact.
The impact point projected from the first auxiliary propulsion system
maneuver was perturbed by unplanned attitude control thrusting that
occurred to counteract forces resulting from a water leak in the
sublimator. Following the second auxiliary propulsion system maneuver, the
small and gradually decreasing unbalanced force from the sublimator water
leak continued to act for a period of 5 hours and further perturbed the
point of impact.
The structural loads experienced during the S-IC boost phase were
well below design values. Thrust cutoff transients experienced were
similar to those of previous flights. During S-IC stage boost, 4- to 5hertz
oscillations were detected beginning at approximately 100 seconds. The
maximum amplitude measured at the instrumentation unit was ±0.06g.
Oscillations in the 4- to 5-hertz range have been observed on previous
flights. The structural loads experienced during the S-IVB stage firings
were well below design values.
The guidance and navigation system provided satisfactory end
conditions for the earth parking orbit and translunar injection. The
control system was different from that of Apollo 14 because of redesigned
filters and a revised gain schedule. These changes were made to stabilize
structural dynamics caused by vehicle mass and structural changes and to
improve wind and engine-out characteristics.
The launch vehicle electrical systems and emergency detection system
performed satisfactorily throughout all phases of flight. Operation of the
batteries, power supplies, inverters, exploding bridge wire firing units,
and switch selectors was normal. Vehicle pressure and thermal environments
in general were similar to those experienced on earlier flights. The
environmental control system performance was satisfactory. All data systems
performed satisfactorily through the flight.
More details of the launch vehicle operation and performance are
given in reference 1.