Apollo 15 Mission Report

accomplished using the reaction control system maneuver program. All pre-maneuver
checks were completed nominally and the maneuver was performed satisfactorily.

9.6.2 Lunar Module Activation, Undocking and Separation

On the day scheduled for landing, entry into the lunar module was about 40 minutes
early. Final closure of the suit zippers was accomplished in the lunar module. One
procedural change was made in order to purge the suit umbilical hoses: Both suit
isolation valves were placed in the FLOW position for 15 seconds, then in the
DISCONNECT position, after which the suit gas diverter valve was placed in the CABIN
position. Checklist functions were generally performed 10 minutes ahead of schedule.

As noted in earlier flights, stars were difficult to see through the alignment optical
telescope while docked with the command module. However, the results of a two-star
sighting using the cursor-spiral technique indicated platform realignment could be
achieved with the optics.

The suit loop integrity check was unsuccessful on the first attempt. The checklist
procedure was followed, but there was obviously a leak because the pressure drop was
approximately 1 psi in 30 seconds. The valve detents were checked, the regulator was
rechecked, and then another integrity check was made. This time, the pressure drop
was acceptable at 0.1 psi in 1 minute. The time a1lowed to accomplish the required
functions for powered descent is more than sufficient. This became apparent when a
number of unanticipated events occurred. Condensate had formed on the lunar module
windows and the heaters had to be activated in order to clear them. Undocking was
delayed for approximately 40 minutes because the command module/lunar module
power transfer umbilical connections were not electrically engaged. A descent engine
throttle check had to be redone because the descent engine control assembly circuit
breaker was in the open position during the first check. The timeline was regained by
the time of the scheduled guidance and navigation system platform realignment and the
pace was very leisurely as the time for powered descent initiation approached; the crew
even had time to eat lunch. The rendezvous radar self-test was normal but, after
separation, the range indicated by the rendezvous radar was approximately twice that
indicated by VHF ranging (see sec. 7.4).

9.7 POWERED DESCENT AND LANDING

The angle of the final descent trajectory after high gate was increased from 14 degrees
to 25 degrees for Apollo 15. This afforded improved dispersion conditions during the
braking phase over the Apennine Mountains, better visibility after pitchover, and more
precise control of manual landing site redesignations.

After receiving final uplinks from the Manned Space Flight Network, the powered
descent program was called up in the lunar module guidance computer 10 minutes prior
to ignition. The landing radar circuit breaker was closed 5 minutes prior to ignition, as
planned, and all events were nominal through the first minute of powered flight.
Automatic ullage and ignition were clearly evident by physiological cues. A correction
was manually entered into the computer to move the targeted landing site about 853
meters (2800 feet) west (downrange) just prior to ignition plus 2 minutes. The indicated

quantity of onboard fuel was 2 percent low at this time, but this was considered
acceptable by ground control. Three minutes after ignition, the spacecraft was yawed to
the planned inplane face-up attitude. Immediately thereafter, at approximately 43 000
feet altitude, landing radar data became acceptable and computer updates were
initiated. Landing radar data were solid throughout the remainder of powered flight.

Throttle recovery occurred on time, and manual attitude hold was evaluated with the
following expected results: positive response, considerable reaction control system
activity, and rapid return to smooth automatic guidance at the Completion of the check.
Predicted pitchover time (high gate) was checked in the computer, and conformed to
the preflight nominal time of 9 minutes 22 seconds.

At an altitude of approximately 9000 feet, the upper fourth of Hadley Delta Mountain
(11,000 feet high) was visible out of the left window. The feeling of slow, forward,
floating motion was experienced and, because of the relative position and motion with
respect to the mountain, an impression of a downrange overshoot was experienced. At
about 8000 feet altitude, ground control informed the crew that the expected landing site
was to be approximately 915 meters (3000 feet) south of the targeted site.

Pitchover occurred on time and the only positive recognizable lunar surface feature was
Hadley Rille. Topographic relief was much less than had been anticipated from the
enhanced 20-meter (65-foot) resolution photography and the associated preflight lunar
terrain models. Sharp landmark recognition features within the Plain of Hadley were
almost nonexistent; however the South Cluster was soon identified. Based upon the
apparent position relative to this feature, plus the 915-meter miss distance to the south
given by ground control, several landing point redesignations were made to the right
(north).

At an altitude of approximately 5000 feet, a pair of subdued craters, which appeared to
be Salyut and its northerly adjacent neighbor, were identified. Uprange landing point
redesignations were made so that the landing could be made in the correct area
northwest of Salyut Crater. The touchdown point was selected from an altitude of 2000
feet and the lunar module was maneuvered to land on what appeared to be a smooth
level surface. The low-gate phase (manual control) of the trajectory was manually
selected and confirmed at an altitude of 400 feet. Descent rate reduction was initiated at
a height of about 200 feet, and visual reference was maintained by watching several
fragments on the lunar surface which were located 30 to 40 meters (100 to 130 feet)
west of the selected site. A trace of blowing surface dust was observed at a height of
130 feet with only a slight increase down to 60 feet. Beginning at this altitude, out-of-the
window visibility was completely obscured by dust until after touchdown.

Tapemeter altitude and altitude rate data readings, provided orally by the Lunar Module
Pilot, appeared to be consistent with the visual observations throughout the terminal
phase of the landing. Surface features and texture became well defined at an altitude of
approximately 1000 feet and, based on preflight experience with visual simulator
displays, descent rates appeared completely nominal and comfortable. Sensations after
manual takeover at 400 feet were almost identical with those experienced in lunar
landing training vehicle operations. The combination of visual simulations and lunar

landing training vehicle flying provided excellent training for the manual portion of the
lunar landing. Comfort and confidence existed throughout this phase.

Additional manual maneuvering south and west could easily have been made below
400 feet; however, because of increased surface mobility afforded by the lunar roving
vehicle, a landing anywhere within the 3-sigma dispersion ellipse was considered a
precise landing, and additional maneuvering within this ellipse, other than for terrain
obstacle avoidance, was considered unnecessary.

The engine stop button was activated shortly after the contact lights were illuminated to
preclude excessive pressure buildup within the nozzle of the descent engine (which had
been extended 10 inches since Apollo 14). Touchdown was firm but only slightly more
so than nominal lunar landing training vehicle landings. Roll and pitch rates were
evident at touchdown as the rear and left foot pads came to rest in a shallow subdued
crater which was not visible during the final phase of the landing. The posttouchdown
events were nominal; no spurious reaction control system firings occurred, and
permission for the lunar stay was voiced by Houston in a timely manner.

9.8 LUNAR SURFACE OPERATIONS

9.8.1 Lunar Module Cabin Activity

Standup extravehicular activity This operation went very smoothly. No problem was
encountered in removing and stowing the drogue. There was no direct sunlight on the
lunar module panels as observations were made and pictures taken from the high
vantage point. The base of the Apennine Front at Hadley Delta, as well as the North
Complex, was visible from this point, and because of the lack of obstacles, acceptable
lunar roving vehicle trafficability over all traverse routes was verified.

The secondary water separator was selected during this period because of a caution
light during primary separator operation. After the standup extravehicular activity, the
primary separator was reselected.

A picture taken during the standup extravehicular activity which reveals the stratigraphy
of Silver Spur is shown in

Figure 9-2

. The sun angle during subsequent extravehicular

activities did not allow this observation.

Sleep.- The crew was able to sleep fairly well. Noise was minimized by configuring the
environmental control system in accordance with the checklist and by using earplugs.
The temperature was ideal for sleeping in the constant-wear garment and sleeping bag,
or in the constant-wear garment and coveralls. A wider hammock would improve the
conditions for sleeping. Aslight light leak through the stitching on the window shades
interfered with getting to sleep.

Extravehicular activity preparation and post -extravehicular activity. The times for
preparation were consistently shorter than the times allowed on the checklist. The only
difficulty encountered was movement in the cabin when in the pressurized suits. Several
areas presented obstacles: the forward corner on the data file, the portable life support
system stowage handle, and the stowed water hose. The portable life support system
recharge was accomplished during the eat period in order to save time and the Lunar
Module Pilot had difficulty in turning the portable life support system water valve off. The
suit was easy to don and doff in 1/6 earth gravity. The crew found that it was possible to
lift themselves up, using the overhead bar, and place both feet in the suit
simultaneously.

Housekeeping.- When doffing the pressure garment assembly after lunar surface
extravehicular operations, the Commander stood on the midsection step and the Lunar

Module Pilot stood on his oxygen purge system to avoid the dirty floor. A jettison bag
was placed over the legs of the suit to contain the dirt.

9.8.2 Lunar Geology

The geological setting of the Hadley-Apennine landing site is such that a great variety of
features and samples were expected. Lack of high resolution Photography of the site
insured that variations in preflight estimates of topographic relief, and surface debris
and cratering could also be expected. In all cases, actual conditions exceeded
expectations.

In general, the mare surface at Hadley is characterized by a hummocky lunar terrain
produced by a high density of rounded, subdued, low-rimmed craters of all sizes. The
craters range in size up to several hundred meters in diameter and are poorly sorted.
There is a notable absenc of large areas of fragmental debris or boulder fields. Unique,
fresh, 1- to 2- meter-diameter, debris-filled craters, with glass-covered fragments in their
central 10 percent, occurred on less than 1 percent of the mare surface.

The large blocks comprising the Apennine Mountains have extremely rounded profiles
with less than 0.1 percent exposed surface outcroppings or fresh young craters.
However, massive units of well-organized uniformly parallel lineations appear within all
blocks, each block having a different orientation within the Hadley area. Mount Hadley is
the most dramatic of these blocks, where at least 200 lineations (

Fig. 9-3

), dipping

approximately 30 degrees to the west-northwest, are exposed on its southwest slope.
Discontinuous, linear, patterned ground is visible superimposed over these lineations. A
more definitive exposure of these units was observed at Silver Spur (

Fig. 9-2

) where an

upper unit of seven 60-meter (200-foot) thick layers is in contact with a lower section of
somewhat thinner parallel layering having evidence of crossbedding and subhorizontal
fractures. Also, three continuous, subhorizontal, non-uniform lineations are visible
within, and unique to, the lower 10 percent of the Mount Hadley vertical profile.

The most distinctive feature of Hadley Rille is the exposed layering within the bedrock
on the upper 15 percent of the rille walls (Fig. 9-4). Two major units can be identified in
this region; the upper 10 percent appears as poorly organized massive blocks with an
apparent fracture orientation dipping approximately 45 degrees to the north. The lower 5
percent is a distinct horizontal unit exposed as discontinuous outcrops partially covered
with talus and fines. Each exposure is characterized by approximately 10 different
multilayered parallel horizontal bedding planes. The remainder of the slope is covered
with talus, 20 to 30 percent of which is fragmental debris, with a suggestion of another
massive unit with a heavy cover of fines at a level 40 percent downward from the top.
The exposures at this level appear lighter in color and more rounded than the general
talus debris. No significant collection of talus is apparent at any one level. The upper 10
percent of the eastern side of the rille is characterized by massive subangular blocks of
fine-grained vesicular porphyritic basalt containing up to 15 percent phenocrysts. This
unit, as viewed toward the south, has the same character as the upper unit on the
western wall. The bottom of the rille is gently sloping and smooth with no evidence of
flow in any direction. No accumulation of talus was evident on the bottom except for
occasional boulders up to 2 meters (6.6 feet) in size.

The major concentration of craters, depicted on preflight maps, is the South Cluster on
the Hadley Plain. Because of the general lack of morphological features on the slopes
of Mount Hadley and Hadley Delta, a linear concentration of craters up the slope of
Hadley Delta, directly south of the Cluster, indicates that a sweep of secondary
fragments from the north may have been the origin of the South Cluster. A buildup of
debris on the southern rim of these craters was not evident, although the approximately
10-percent coverage of the surface by fragmental debris in the region of the South
Cluster is unique within the Hadley region.

Sampling was accomplished in the general vicinity of all preplanned locations with the
exception of the North Complex, which was unfortunately excluded because of higher
priorities of activities associated with lunar surface experiments. A great variety of
samples were collected; some are obviously associated with their location, while others
will require further study to determine a relationship. The capability to identify rock types
at the time of collection was comparable to a terresterial exercise and was unhampered
by the unique environment of the moon. Identifiable sample features include:
anorthosite; basalts with vesicules of various sizes, distribution, and orientation; basalts
with phenocrysts of various quantities, sizes, shapes, and orientation; olivine- and
pyroxene-rich basalts; third-order breccias with a variety of well-defined clasts; rounded

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glass fragments; glass-filled fractures and glass-covered fragments; and other surface
features such as slickensides.

9.8.3 Lunar Surface Mobility Systems Performance

Extravehicular mobility unit.- The mobility of the modified suit allowed the lunar roving
vehicle to be mounted easily. It was also possible to bend down on one knee to retrieve
objects from the surface.

The cooling performance of the portable life support system was excellent. The
Commander used maximum cooling for tasks such as the drilling operations. The Lunar
Module Pilot never used more than intermediate cooling. For the driving portion of the
lunar surface exploration, minimum cooling was quite comfortable. During the first
extravehicular activity, the Lunar Module Pilot experienced several warning tones. The
suspected cause was a bubble in the portable life support system water supply. When
switchover to auxiliary water was required, ground control recommended minimum
cooling, which was new information to the crew. The temperature in the suits gradually
increased over the three extravehicular activities.

The portable life support system straps were adjusted during the preflight crew
compartment fit and function procedure. The Commander's straps worked fine.
However, the Lunar Module Pilot's seemed short since the controls were located too
high and too far to the left for him to reach. The Commander's portable life support
system seemed loose at the end of the third extravehicular activity.

Lunar roving vehicle.- The major hardware innovation for the lunar exploration phase of
the Apollo 15 mission was the lunar roving vehicle (

Fig. 9-5

) Because of geological

requirements during surface traverses, time was limited for evaluating the
characteristics of the vehicle. However, during the traverses, a number of qualitative
evaluations were made. The following text discusses the performance, and the stability
and control of "Rover 1", as well as other operational considerations pertaining to the
vehicle.

101

The manual deployment technique worked very well. Simulations had demonstrated the
effectiveness of this technique and, with several minor exceptions, it worked exactly as
in preflight demonstrations. The first unexpected condition was noticed immediately
after removing the thermal blanket when both walking hinges were found open. They
were reset and the vehicle was deployed in a nominal manner. The support saddle,
however, was difficult to remove after the vehicle was on the surface. No apparent
cause was evident. Additionally, both left front hinge pins were out of their normal detent
positions; both were reset with the appropriate tool. After removal of the support saddle,
the rover was manually positioned such that "forward" would be the initial driving mode.

Front steering was inoperative during the first extravehicular activity. All switches and
circuit breakers were cycled a number of times during the early portion of the first
extravehicular activity with no effect on the steering. Subsequently, at the beginning of
the second extravehicular activity, cycling of the front steering switch apparently
enabled the front steering capability which was then utilized throughout the remaining
traverses.

Mounting and dismounting the rover was comparable to preflight experience in 1/6-
gravity simulations in the KC-135 aircraft. Little difficulty was encountered. The normal
mounting technique included grasping the staff near the console and, with a small hop,
positioning the body in the seat. Final adjustment was made by sliding, while using the
footrest and the back of the seat for leverage. It was determined early in the traverses

102

that some method of restraining the crew members to their seats was absolutely
essential. In the case of Rover 1, the seatbelts worked adequately; however, excessive
time and effort were required to attach the belts. The pressure suit interface with the
rover was adequate in all respects. None of the preflight problems of visibility and suit
pressure points were encountered.

The performance of the vehicle was excellent. The lunar terrain conditions in general
were very hummocky, having a smooth texture and only small areas of fragmental
debris. A wide variety of craters was encountered. Approximately 90 percent had
smooth, subdued rims which were, in general, level with the surrounding surface.
Slopes up to approximately 15 percent were encountered. The vehicle could be
maneuvered through any region very effectively. The surface material varied from a thin
powdered dust [which the boots would penetrate to a depth of 5 to 8 centimeters (2 to 3
inches) on the slope of the Apennine Front to a firm rille soil which was penetrated
about 1 centimeter (one-quarter to one-half inch) by the boot. In all cases, the rover's
performance was changed very little.

The velocity of the rover on the level surface reached a maximum of 13 kilometers (7
miles) per hour. Driving directly upslope on the soft surface material at the Apennine
Front, maximum velocities of 10 kilometers (5.4 miles) per hour were maintained.
Comparable velocities could be maintained obliquely on the slopes unless crater
avoidance became necessary. Under these conditions, the downhill wheel tended to dig
in and the speed was reduced for safety.

Acceleration was normally smooth with very little wheel slippage, although some soil
could be observed impacting on the rear part of the fenders as the vehicle was
accelerated with maximum throttle. During a "Lunar Grand Prix", a roostertail was noted
above, behind, and over the front of the rover during the acceleration phase. This was
approximately 3 meters (10 feet) high and went some 3 meters forward of the rover. No
debris was noted forward or above the vehicle during constant velocity motion. Traction
of the wire wheels was excellent uphill, downhill, and during acceleration. A speed of 10
kilometers per hour could be attained in approximately three vehicle lengths with very
little wheel slip. Braking was positive except at the high speeds. At any speed under 5
kilometers (2.7 miles) per hour, braking appeared to occur in approximately the same
distance as when using the 1-g trainer. From straight-line travel at velocities of
approximately 10 kilometers per hour on a level surface, the vehicle could be stopped in
a distance of approximately twice that experienced in the 1-g trainer. Braking was less
effective if the vehicle was in a turn, especially at higher velocities.

Dust accumulation on the vehicle was considered minimal and only very small
particulate matter accumulated over a long period of time. Larger particles appeared to
be controlled very well by the fenders. The majority of the dust accumulation occurred
on the lower horizontal surfaces such as floorboards, seatpans, and the rear wheel
area. Soil accumulation within the wheels was not observed. Those particles which did
pass through the wire seemed to come out cleanly. Dust posed no problem to visibility.

Obstacle avoidance was commensurate with speed. Lateral skidding occurred during
any hardover or maximum-rate turn above 5 kilometers per hour. Associated with the
lateral skidding was a loss of braking effectiveness. The suspension bottomed out

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approximately three times during the entire surface activity with no apparent ill effect. An
angular 30- centimeter (1-foot) high fragment was traversed by the left front wheel with
no loss of controllability or steering, although the suspension did bottom out. A relatively
straight-line traverse was easily maintained by selection of a point on the horizon for
directional control, in spite of the necessity to maneuver around the smaller subdued
craters. Fragmental debris was clearly visible and easy to avoid on the surface. The
small, hummocky craters were the major problem in negotiating the traverse, and the
avoidance of these craters seemed necessary to prevent controllability loss and
bottoming of the suspension system.

Vehicle tracks were prominent on the surface and very little variation of depth occurred
when the bearing on all four wheels was equal. On steep slopes, where increased loads
were carried by the downhill wheels, deeper tracks were encountered - perhaps up to 3
or 4 centimeters (an inch or two) in depth. There was no noticeable effect of driving on
previously deposited tracks, although these effects were not specifically investigated.
The chevron tread pattern left distinct and sharp imprints. In the soft, loose soil at the
Apollo lunar surface experiment package site, one occurrence of wheel spin was
corrected by manually moving the rover to a new surface.

The general stability and control of the lunar roving vehicle was excellent. The vehicle
was statically stable on any slopes encountered and the only problem associated with
steep slopes was the tendency of the vehicle to slide downslope when both crewmen
were off the vehicle. The rover is dynamically stable in roll and pitch. There was no
tendency for the vehicle to roll even when traveling upslope or downslope, across
contour lines or parallel to contour lines. However, qualitative evaluation indicates that
roll instability would be approached on the 15-degree slopes if the vehicle were traveling
a contour line with one crewmember on the downhill side. Both long- and short-period
pitch motions were experienced in response to vehicle motion over the cratered,
hummocky terrain, and the motion introduced by individual wheel obstacles. The long-
period motion was very similar to that encountered in the 1-g trainer, although more
lightly damped. The "floating" of the crewmembers in the 1/6-g field was quite
noticeable in comparison to 1- g simulations. Contributions of shortperiod motion of
each wheel were unnoticed and it was difficult to tell how many wheels were off the
ground at any one time. At one point during the "Lunar Grand Prix", all four wheels were
off the ground, although this was undetectable from the driver's seat.

Maneuvering was quite responsive at speeds below approximately 5 kilometers per
hour. At speeds on the order of 10 kilometers per hour, response to turning was very
poor until speed was reduced. The optimum technique for obstacle avoidance was to
slow below 5 kilometers per hour and then apply turning correction. Hardover turns
using any steering mode at 10 kilometers per hour would result in a breakout of the rear
wheels and lateral skidding of the front wheels. This effect was magnified when only the
rear wheels were used for steering. There was no tendency toward overturn instability
due to steering or turning alone. There was one instance of breakout and lateral
skidding of the rear wheels into a crater approximately 1/2 meter (1-112 feet) deep and
1-1/4 meters (4 feet) wide. This resulted in a rear wheel contacting the far wall of the
crater and subsequent lateral bounce. There was no subsequent roll instability or
tendency to turn over, even though visual motion cues indicated a roll instability might

104

develop.

The response and the handling qualities using the control stick are considered
adequate. The hand controller was effective throughout the speed range, and
directional control was considered excellent. Minor difficulty was experienced with
feedback through the suited crewmember to the hand controller during driving.
However, this feedback could be improved by a more positive method of restraint in the
seat. Maximum velocity on a level surface can be maintained by leaving the control stick
in any throttle position and steering with small inputs left or right. A firm grip on the
handle at all times is unnecessary. Directional control response is excellent although,
because of the many dynamic links between the steering mechanism and the hand on
the throttle, considerable feedback through the pressure suit to the control stick exists.
A light touch on the hand grip reduces the effect of this feedback. An increase in the
lateral and breakout forces in the directional hand controller should minimize feedback
into the steering.

Two steering modes were investigated. On the first extravehicular activity, where rear-
wheel-only steering was available, the vehicle had a tendency to dig in with the front
wheels and break out with the rear wheels with large, but less than hardover, directional
corrections. On the second extravehicular activity, front-wheel-only steering was
attempted, but was abandoned because of the lack of rear wheel centering. Four-wheel
steering was utilized for the remainder of the mission. It is felt that for the higher speeds,
optimum steering would be obtained utilizing front steering provided the rear wheels are
center-locked. For lower speeds and maximum obstacle avoidance, four-wheel steering
would be optimal. Any hardover failure of the steering mechanism would be recognized
immediately and could be controlled safely by maximum braking.

Forward visibility was excellent throughout the range of conditions encountered with the
exception of driving toward the zero-phase direction. Washout, under these conditions,
made obstacle avoidance difficult. Up-sun was comparable to cross-sun if the opaque
visor on the lunar extravehicular visor assembly was lowered to a point which blocks the
direct rays of the sun. In this condition, crater shadows and debris were easily seen.
General lunar terrain features were detectable within 10 degrees of the zero phase
region. Detection of features under high-sun conditions was somewhat more difficult
because of the lack of shadows, but with constant attention, 10 to 11 kilometers (5-1/2
to 6 miles) per hour could be maintained. The problem encountered was recognizing the
subtle, subdued craters directly in the vehicle path. In general, 1-meter (3 1/4-foot)
craters were not detectable until the front wheels had approached to within 2 to 3
meters (6-1/2 to 10 feet).

The reverse feature of the vehicle was utilized several times, and preflight-developed
techniques worked well. Only short distances were covered, and then only with a
dismounted crewmember confirming the general condition of the surface to be covered.

The 1-g trainer provides adequate training for lunar roving vehicle operation on the lunar
surface. Adaptation to lunar characteristics is rapid. Handling characteristics are quite
natural after several minutes of driving. The major difference encountered with respect
to preflight training was the necessity to pay constant attention to the lunar terrain in
order to have adequate warning for obstacle avoidance if maximum average speeds

105

were to be maintained. Handling characteristics of the actual lunar roving vehicle were
similar to those of the 1-g trainer with two exceptions: braking requires approximately
twice the distance, and steering is not responsive in the 8- to 10-kilometer (4- to 5 1/2-
mile) per hour range with hardover control inputs. Suspension characteristics appeared
to be approximately the same between the two vehicles and the 1/6-g suspension
simulation is considered to be an accurate representation with the exception of the
crewmembers' weight.

The navigation system is accurate and a high degree of confidence was attained in a
very short time. Displays are also adequate for the lunar roving vehicle systems.

Lunar communications relay unit.- The lunar communications relay unit and associated
equipment operated well throughout the lunar surface activities. The deployment
techniques and procedures are good, and the operational constraints and activation
overhead are minimum. Alignment of the high-gain antenna was the only difficulty
encountered, and this was due to the very dim image of the earth presented through the
optical sighting device. The use of signal strength as indicated on the automatic gain
control meter was an acceptable back-up alignment technique.

9.8.4 Lunar Surface Science Equipment Performance

Apollo lunar surface experiment package.- The packages were manually removed from
the scientific equipment bay. During unstowing of equipment, the universal handling
tools were difficult to remove from the stowed position and the scientific equipment bay
doors required cycling to the fully closed position. In deploying the central station, the
strings which pull the rear pins on the sun shield cover were broken, requiring the Lunar
Module Pilot to pull the pins with his fingers. Connection of the suprathermal ion
detector experiment to the central station was very difficult. The task required the Lunar
Module Pilot to use both hands and all the weight that he could bring to bear on the
locking collar. Another difficulty was in the deployment of the suprathermal ion detector
experiment. The universal handling tool was not locked, which caused the suprathermal
ion detector experiment to fall off the tool when positioning the experiment.

Emplacement of the heat flow experiment and collection of the deep core sample were
difficult and required far more time and effort than anticipated. Operation of the
hardware components was acceptable with the exception of the vise on the geology
pallet. The vise was installed incorrectly and was useless for separating the assembled
stems.

The primary cause of the working difficulties encountered with the lunar drill was the
lack of knowledge of the regolith encountered at the Hadley site. Because of the
hardness of the material 1 meter (3 1/4 feet) below the surface, the bore stems for
drilling the holes for the heat flow experiment did not penetrate at the expected rates
and did not excavate deep material to the surface. Because of the resulting high torque
levels on the chuck-stem interface, the chuck bound to the stems and, in one case,
required destruction of the stem to remove the chuck and drill. The deep core sample
could not be extracted from the hard soil by normal methods and required both
crewmen lifting on the drill handles to remove it. The exterior flutes contributed to this
condition since the core stems were pulled into the lunar surface when the drill was

106

activated. See section 14.4.1 for further discussion.

Soil mechanics.- The classic trench was easily dug in the vicinity of the Apollo lunar
surface experiment deployment site. Penetrometer measurements were made at the
trench and in the lunar roving vehicle tracks. The floor of the trench was a very hard
resistant layer. In making the penetrometer measurements, the trench side was
collapsed by pushing on the flat plate positioned about 10 centimeters (4 inches) from
the trench wall. A problem with the penetrometer was that the ground plane would not
stay in the extended position because of excessive spring force (see section 4.13).

Geology tools.- The retractable tethers (yo-yo's) failed during the first extravehicular
activity. These devices were used by the Commander to secure tongs and by the Lunar
Module Pilot to secure the extension handle during the geology work. They would have
been used to hold the universal handling tools during deployment of the Apollo lunar
surface experiment package. Unfortunately, both yo-yos failed before the experiment
package was deployed. Cord was used for the flight equipment instead of wire, as on
the training equipment. The tongs, scoop, hammer, and rake worked well, and the rake
also functioned well as a scoop. The newly designed core tube worked well in that the
sample was completely retained. Penetration of the surface with the core tube was
usually accomplished with a hard push; however, the hammer was required to obtain a
double core. The locking and unlocking of the buddy secondary life support system bag
attached to the rear of the geology pallet was very difficult because the locking tab was
hidden behind the bag. Sample return container 2 was not sealed because a portion of
the collection bag was caught in the rear hinge.

Cameras.- The film in the 16-mm data acquisition camera would not pull through the
camera. Only one magazine worked on the lunar surface. Also, the Lunar Module Pilot's
70-mm Hasselblad electric data camera malfunctioned at the end of the second
extravehicular activity. An inspection in the lunar module cabin revealed excessive lunar
material on the film drive. The camera failed again on the third extravehicular activity
and was returned to earth. These anomalies are discussed in sections 14.5.3 and 14-
5.4.

9.9 LUNAR ORBITAL SOLO OPERATIONS

9.9.1 Maneuvers

Solo maneuvers in lunar orbit included circularization and a plane change. Both of these
maneuvers were accomplished using service propulsion system bank B only because of
the aforementioned circuit problem with bank A. The maneuvers were nominal and were
accomplished with residual velocities of an order that required no further maneuvering.

9.9.2 Science and Photography

Scientific instrument module experiments.- The scientific instrument module was
operated during the three days of lunar surface activity according to carefully detailed
preflight planning. Because of the complexity of the scientific instrument module, all
operations during this period were to be accomplished without deviation from the flight
plan. In the event that difficulties were encountered, items were to be dropped from the

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flight plan. Some flight difficulties were experienced with the scientific instrument
module operations. These difficulties were associated with the retraction of the mass
spectrometer boom and with the extension and retraction of the mapping camera. The
mass spectrometer boom extended normally but did not always indicate full retraction. It
was suspected that the boom was retracting into the carriage, but not far enough to
cause an indication of full retraction. The monitoring, as well as the timing of the boom
extensions and retractions, required an expenditure of time which had not been
anticipated preflight. The mapping camera extended and retracted more slowly than had
been anticipated and it eventually failed in the extended position. This also required
additional monitoring time on the part of the Command Module Pilot. The mass
spectrometer boom retraction problem is discussed in more detail in section 14.1.6 and
additional discussion on the mapping camera problem is given in section 14.3.3.

The scientific instrument module bay activity was essentially a monitoring operation.
Functions were performed at a prescribed time and required very careful attention to the
details in the flight plan. One procedure that was used to assist in this monitoring activity
was the use of computer time on the display keyboard in the lower equipment bay. The
procedure required the initiation of an external delta-velocity program at a prescribed
time. The clock in the computer would then count down to, and up from, that time.
However, because of the calculations required by the computer during operation of this
program, the spacecraft actually deviated out of the attitude control dead bands.
Therefore, after the first day in lunar orbit, the computer program was used for very
short intervals of time only. Consequently, the monitoring of the scientific instrument
module bay became much more difficult because the timing of these events had to be
accomplished using ground elapsed time, and not time relative to an event. Also
complicating the monitoring was the fact that the lights in the lower equipment bay could
no longer illuminate the mission timer because of the previously described short in the
a-c electrical system.

All of the solo operations in lunar orbit were accomplished well within the capability of
the Command Module Pilot with respect to the amount of work that had to be done in
the time available. There were times when visual observation of the surface and hand-
held photography were accomplished in conjunction with the operation of the scientific
instrument module bay. This posed no problem and was accomplished as prescribed.

Command and service module photography.- The onboard photography was
accomplished generally as prescribed in the flight plan except that the operation was
more detailed than had been anticipated prior to flight. Acquisition of all photographic
targets was based on flight plan time. However, with additional training just prior to
flight, the Command Module Pilot attained a sufficient degree of proficiency in target
recognition and in the geology of the lunar surface so that detailed flight plan times were
not required.

The photography was accomplished using the settings prescribed in the flight plan and
additional photographs were taken utilizing the settings based on sun angles that were
listed in both the orbit monitor charts and by an orbit monitor wheel which was
developed for that purpose. The photography from window 5 posed some problems
because of a Lexan filter installed inside of the spacecraft (since no ultraviolet filter
existed within the window). The Lexan filter, at this time, was scratched and it did not

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appear that good photography could be taken through that window, so the filter was
removed for the photography and then replaced.

Visual observations.- In conjunction with the photography, visual observations of
selected surface features were made. These observations were designed to allow a
better understanding of large-scale geologic processes. Three areas of special interest
were centered around the crater Tsiolkovsky, the Littrow area, and the Aristarchus
Plateau.

Tsiolkovsky is a large impact crater centered at 128 degrees east latitude, and uniquely
placed in the region between the large mare basins and the upland areas on the back
side. It is a deep crater with a prominent central peak and steep rim walls; the crater
walls are cut by several faults. The smooth, dark crater floor resembles the mare
surfaces visible on the moon's near side. There is much evidence of volcanic processes
on the eastern side of the crater as shown by numerous lava flows originating along
fault zones and filling minor craters around Tsiolkovsky. On the western side, there is a
large rock avalanche that extends from the rim northwest into the subdued crater Fermi.

The Littrow area was viewed because of distinct color banding extending out into Mare
Serenitatis. This banding appears to have been produced by volcanism in the form of
flows or volcanic ash deposits. Within the darkest band, there were numerous small
positive features believed to be cinder cones. These are the first well-documented
cinder cones observed on the moon.

The Aristarchus Plateau appears to be the most active volcanic area on the moon.
There are many lava flows and rille-like features in the central plateau area.

One of the mysteries about the rilles has been the rille termini. If these features were
formed by lava flows, there would be delta-shaped flow tongues formed at the outlets.
Inflight observation resulted in the conclusion that if these delta-shaped flow tongues
were present, they were covered by lava flows that inundated the rilles.

9.10 ASCENT, RENDEZVOUS AND DOCKING

9.10.1 Ascent

Ascent ignition was automatic, the programmed pitchover was smooth and positive, and
the trajectory appeared nominal throughout the maneuver. Five minutes after lift-off,
radar lock-on was attempted with negative results; 5 seconds of high slew in each
direction also resulted in no signal strength. Approaching insertion, Houston advised of
a radial error in the primary guidance and navigation system and recommended an in-
plane trim of the abort guidance system velocity residuals. At automatic primary
guidance and navigation system shutdown, the abort guidance system indicated a
residual velocity of minus 3.5 ft/sec. This was trimmed to minus 2 ft/sec along the
longitudinal axis. No vernier adjustment was required, and the ground advised that the
terminal phase initiate maneuver would be off-nominal and that final approach would be
from near horizontal; these factors were due to the command and service module orbit.

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9.10.2 Rendezvous

Lunar module.- The abort guidance system warning light came on shortly after insertion.
The light was reset normally and the abort guidance system self-test was satisfactory.
After insertion, there was early confirmation of rendezvous radar, primay guidance and
navigation system, and abort guidance system guidance data. Automatic updating was
enabled in both the primary guidance system and the abort guidance system. At final
computation for terminal phase initiation, there were 26 marks in the primary guidance
and navigation system, and 13 range marks and 13 range-rate marks in the abort
guidance system. Another accelerometer bias update was made on the primary
guidance system before terminal phase initiation. The primay guidance and navigation
system solution was used.

Nominal procedures were used for primary guidance and navigation system midcourse
corrections. For the abort guidance system, several rangerate inputs were manually
inserted to insure that there were sufficient marks to obtain good solutions. The
technique used was to watch the mark counter until the range changed to a plus value,
then the range rate was manually entered. The command and service module tracking
light was not visible until 40 minutes after sunset at a range of approximately 18 miles.

When approaching the last braking gate (1500 feet separation distance), the
Commander was surprised to see that no line-of-sight rates were indicated by the
rendezvous radar crosspointers. (Refer to sec. 14.2.7 for a discussion of this anomaly.)
Line of site rates were verified by the Command Module Pilot. Thrusting left and up
approximately 4 ft/sec was required to null the line-of-site rates. The resulting out-of-
plane angle at station keeping was approximately 20 degrees.

Command and service module.- The command and service module was prepared for
the rendezvous by deactivating all of the scientific instrument module bay experiments,
retracting all of the booms, and closing the camera and experiment covers. All but four
reaction control jets were activated 3 hours before lunar module ascent initiation to
allow proper ground tracking and orbit determination. On the rendezvous revolution
itself, VHF contact was made just prior to ascent and the Manned Space Flight Network
relay was deactivated. All communications with the lunar module were accomplished
using the VHF. Just prior to insertion, VHF ranging was activated. Several resets were
required before the ranging was locked, and subsequently, lock was broken only once.

After insertion, a lunar module state vector was uplinked from the ground and an
automatic maneuver was made to the rendezvous tracking attitude. The rendezvous
was completed using a minimum-key-stroke (automatic sequencing) computer program.
This program was new for this flight, and was designed to relieve the Command Module
Pilot's workload. The computer automatically sequenced through the rendezvous
maneuvers and tracking periods. It was initiated at the pre-terminal phase initiation
program and was terminated with the final rendezvous computer program, which
maneuvered the command and service module to the desired tracking attitude just prior
to docking. The program functioned as anticipated and allowed the Command Module
Pilot much greater time for optical tracking and systems monitoring.

There was same difficulty at first in actually seeing the lunar module tracking light

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because the lunar module was not centered in the scanning telescope. After going into
darkness, the light was observed at about 15 degrees from the center of the telescope.
After two marks were taken, the optics tracked the lunar module in the center of the
sextant. A total of 18 optical and 19 VHF marks were taken before the final solution was
initiated. The maneuver to the terminal phase initiate attitude was a small maneuver of
approximately 20 to 30 degrees in pitch. After the lunar module performed the terminal
phase initiation maneuver, the actual velocity changes were inserted into the computer.
The command and service module then was maneuvered automatically to the tracking
attitude. Ten optics and nine VHF marks were taken prior to the first midcourse
correction and 18 optics and 11 VHF marks were taken prior to the second midcourse
correction. All solutions were compared with the lunar module solutions and were within
the prescribed limits. The lunar module subsequently accomplished the maneuvers
based on its own solutions.

9.10.3 Docking and Crew Transfer

Beginning at terminal phase finalization, the spacecraft was maneuvered to the crew-
optical-alignment-sight tracking attitude to monitor the lunar module and to verify line-of-
sight rates. The lunar module assumed a station keeping position with the command
and service module and a maneuver was initiated to allow photographs to be taken of
the scientific instrument module bay. After this was accomplished, the spacecraft were
maneuvered to the docking attitude. The docking was initiated and completed by the
command and service module. Again, the closing rates were approximately 0.1 ft/sec,
and the docking was completed by thrusting along the longitudinal axis on contact until
capture latch engagement was indicated. After the capture latches were engaged and
the attitudes were stabilized, the probe was retracted and a hard dock was
accomplished.

Several operations were initiated almost simultaneously after the docking. The scientific
instrument module bay experiments were activated and operated throughout the time of
transfer of equipment from the lunar module to the command and service module. The
experiments operations hindered the transfer to some extent because the Command
Module Pilot was required to monitor and observe the scientific instrument panel in the
command and service module. However, the transfer was successfully completed and
all transfer bags were stowed in the proper locations. The lunar module crew transferred
back into the command and service module and preparations were made for undocking.

9.11 POST-DOCKING LUNAR ORBITAL OPERATIONS

9.11.1 Lunar Module Jettison

After all equipment was stowed, the crew donned their helmets and gloves and
prepared the tunnel for lunar module Jettison. Some difficulty was experienced with
venting the pressure in the tunnel. The differential pressure across the tunnel hatch
would not increase as expected. The hatch was removed and the seals on both the
lunar module hatch and the command module hatch were checked. Both hatches were
replaced and the differential pressure check was completed satisfactorily. A pressure
suit integrity check was then accomplished; again, with some difficulty. The crew

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considered that the liquid cooled garment connector was responsible for the failure of
one of the suits to pressurize properly, so a plug was inserted into the Commander's
suit. After the plug was installed and the suits were rezipped, the suit circuit pressure
integrity check was accomplished normally. Because of the difficulty with the tunnel and
with the suit circuit integrity check, the lunar module jettison was delayed approximately
one revolution, after which it was accomplished normally. However, because of the
difference in orbital position from the planned position at the time of the lunar module
jettision, the separation maneuver was recomputed to assure a positive separation
distance. This was accomplished about 20 minutes after jettision and all subsequent
events were nominal.

9.11.2 Flight Plan Updating

After rendezvous and with all three crewmen aboard the command and service module,
the flight plan was updated to utilize the full capability of the scientific instrument module
bay. The flight plan changes were considerable, but with one crewman free to copy the
updates, the other two crewmen were available to monitor and perform the scientific
instrument module activities. This meant that all three crewmen were utilized a good
percentage of the time. The operation was performed satisfactorily and the real-time
changing of the flight plan was accomplished without difficulty. The philosophy that
there would be no changes in the flight plan during the solo operations and that the
flight plan would be subject to real-time change when all three crewmen were aboard
was satisfactory.

9.11.3 Maneuvers

Prior to the transearth injection maneuver, an orbital shaping maneuver was performed
to launch the subsatellite into an orbit guaranteeing a long lifetime. This was a relatively
short thrusting maneuver and was accomplished using service propulsion system bank
B. The subsatellite was jettisoned as scheduled and it was observed approximately 15
to 20 feet away from the spacecraft. All arms were extended and it was rotating with a
coning angle of approximately 10 degrees.

The next maneuver was the transearth injection maneuver which was accomplished
without difficulty. The service propulsion system was again activated by the special
procedure. Gimbal position indications were very smooth and there was very little
attitude excursion. The maneuver was completed nominally.

9.11.4 Command and Service Module Housekeeping

Particular emphasis was placed on housekeeping throughout the flight in order to
maintain organization within the command module crew compartment with the
additional stowage requirements for the Apollo 15 mission. Normal cabin living activities
required more time than anticipated preflight because of additional equipment, onboard
stowage conditions, new pressure suits, a strict adherence to nutrition schedules, and
limitations on overboard dump periods. The most efficient manner of completing these
activities was to perform all cleaning, dumping, canister change, and chlorination
operations just prior to a rest period, exclusive of any scientific instrument module

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activities. Similarly, an exclusive waking and eat period just after the rest period and
prior to any other activities (such as scientific instrument module activation and flight
plan updates) conforms to normal daily activities on earth and results in far more
efficient utilization of time during flight.

9.12 TRANSEARTH FLIGHT OPERATIONS

9.12.1 Transearth Coast Extravehicular Activity

Approximately 16 hours after the transearth injection maneuver, the crew had
completed preparations for an extravehicular activity which was specifically planned to
retrieve the panoramic and mapping camera cassettes from the scientific instrument
module. The preparation for the extravehicular activity was accomplished in a nominal
fashion and required approximately 5 112 hours. Preparation of the command module
was partially accomplished during the night preceding the extravehicular activity and
was completed approximately 2 hours before the flight plan time for the event. This
allowed an unhurried, careful preparation of all equipment and resulted in an
extravehicular activity that was accomplished on time and without difficulty. The final
preparation associated with the extravehicular activity involved the relocation of some
rock bags and containers, removal of the center couch, donning of pressure suits, suit
integrity checks, and the donning of the special extravehicular activity umbilical and
pressure suit equipment by the Command Module Pilot. This was accomplished
satisfactorily per the check- list. The spacecraft was maneuvered to the extravehicular
activity sun-angle attitude which allowed illumination of the scientific instrument module
bay, while insuring that the sun did not shine directly into the command module hatch.
In this attitude the sun angle was low with respect to the scientific instrument module,
but reflections in and around the module illuminated all of the equipment. After side
hatch opening, the television and 16-mm cameras were installed on the hatch to record
the extravehicular activity. The 16-mm camera operated for only 3 or 4 frames and
produced only one recoverable picture (

Fig. 9-6

). The camera had apparently been

turned on and then inadvertently turned off after a three-second interval while set at a
frame rate of one frame per second. The television camera operated properly. The
Command Module Pilot proceeded to the scientific instrument module bay in a fashion
similar to that used during training. The operation required about 16 minutes and was
completed in an efficient manner even though an off-nominal condition existed in that
the mapping camera was extended and could not be retracted. The panoramic camera
cassette was returned to the hatch and was tethered inside the command module. The
mapping camera cassette was returned on the second trip. Because of the difficulty with
the mass spectrometer boom, and the mapping camera extension and retraction
mechanism, a third trip was made to the scientific instrument module to investigate
these pieces of equipment. The spectrometer was observed to have retracted to the
point of capture by the guide pins in the carriage but had not retracted fully. No external
jamming of the mapping camera carriage was seen. One additional problem, associated
with the panoramic camera, was investigated during the third trip. The panoramic
camera velocity/altitude sensor malfunctioned during lunar orbit operations. The sensor
was examined and nothing was in the line of sight of the velocity/altitude sensor to
account for the failure. Following the extravehicular activity, the Command Module Pilot
ingressed, the hatch was closed, and the command module was pressurized using the

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three 1-pound oxygen bottles from the rapid repressurization system, the Command
Module Pilot's extravehicular umbilical flow, and the oxygen purge system.

9.12.2 Science and Photography

The instruments in the scientific instrument module were operated during the transearth
coast to obtain background data needed for interpretation of data obtained in lunar orbit
and to acquire information on celestial sources. These operations, at times, required
specific attitude pointing, and at other times, were accomplished during passive thermal
control periods. The operations, although accomplished in large part based upon real-
time planning, posed no difficulty in adhering to the preflight-planned timeline. During
transearth flight, ultraviolet photographs were taken of both the earth and the moon, star
patterns were photographed through the sextant, and photographs were taken in an
attempt to record the particulate matter around the spacecraft following a waste water
dumping operation.

9.12.3 Navigation

During transearth flight, a large portion of time was devoted to cislunar midcourse
navigation. This was done to demonstrate the capability to perform onboard navigation
to achieve safe entry conditions in the event Manned Space Flight Network
communications are lost. Calibrations having been accomplished on translunar coast,
the midcourse exercises were performed, as closely as possible, according to the
schedule in the contingency checklist. This navigational exercise was accomplished by
maintaining a separate state vector stored in the command module computer registers
normally used for lunar module state vectors. It was discovered that the navigation

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could, in fact, be performed onboard to at least validate the state vector during a
nominal transearth coast. The techniques for accomplishing the cislunar sightings were
essentially the same as had been used during translunar coast. The earth at this time
appeared as a very thin crescent because of the earth-sun relationship, but the horizon
was easily discernible. The sightings were taken with the spacecraft in minimum-
impulse control, and all but the last set of sightings were accomplished using uncoupled
thrusters for attitude control. Low attitude rates were maintained and the sightings were
easier than had been experienced preflight. The onboard state vector was maintained
until just prior to entry and it would have been satisfactory in the event that a loss of
communications had been experienced.

9.13 ENTRY AND LANDING

The preparation for entry was accomplished normally and the third midcourse correction
was performed to insure that the target point was acceptable. In preparation for service
module separation, all systems were checked, chill-down of the spacecraft was
accomplished as prescribed, and the spacecraft was maneuvered to the service module
jettison attitude. The jettison was accomplished as planned. Entry was nominal, with the
entry interface occurring at the proper time. The entry monitor system indicated 0.05g at
the expected time and the entry monitor system, the guidance and navigation system,
and the accelerometers were all in agreement during entry. The lack of entry monitor
system background lighting did not affect observation of the scroll. The entry was
normal, but during descent on the main parachutes, one of the parachutes partially
deflated. The main parachutes deployed normally at 10 000 feet, and checklist items
were performed. However, following the reaction control system depletion firing, the
partially-deflated parachute was observed. The condition resulted in a higher rate of
descent than with three fully-inflated parachutes. Calls were received from the recovery
team indicating that the situation was being observed by ground personnel. All checks
subsequent to this were made according to the checklist and, because of the higher rate
of descent, touchdown was accomplished about 32 seconds earlier than it would have
with all parachutes fully inflated. The landing loads were higher than normal; however, it
did not appear that the couch struts had stroked. The only internal indication of a hard
landing was that the crew optical alignment sight was detached from its stowage
bracket and fell to the aft bulkhead.

All events after landing were normal. The parachutes were released and, because of
the low wind condition, settled around the command module. The recovery ship and
forces were near the spacecraft at landing and recovery operations were normal.