The major question for planning operations on the lunar surface includes which experiments or tasks will be performed. Comments regarding overplanning of the Apollo timelines and having little time to explore and think while performing an EVA are certainly ones that have been voiced by the crews and some of the PIs of the era, but it is a complex question that must be traded off against what one would have been willing to forego in order to do more "thinking and exploring." How do we measure the improvement in sample selection vs. a greater number of samples, an increased number of measurements, or an improved deployment of an instrument? How many samples are we willing to give up? How much poorer a documentation of the samples? How many fewer magnetometer or gravimeter measurements? Each discipline would have a different set of answers.
The Apollo traverse planners tried to take these considerations into account by providing some time at most of the stations for general observations and descriptions, and by trying to arrive at an overall science consensus before the mission via the Science Working Panel, as to what was a reasonable balance of time allocations among the various experiments. Certainly, in the early missions the EVA timelines were scheduled very tightly. In the later J missions, however, more EVA time, better training, and an emphasis on exploration resulted in a more relaxed approach to the field geology experiment. It is questionable whether Apollo would be done any differently today if we were going back to the Moon with the same constraints on time available at a given site. When we have a permanent outpost and an opportunity to have longer visits to an area, this approach may change. It must be realized, however, that this won't happen even in the first few years of an outpost. The number of potentially interesting things to do near just about any site can quickly consume all possible EVA time. Also, Apollo had months to plan and train for each mission. Similar Earth support for an equivalent effort when EVAs happen daily is probably not realistic, so more "local" planning may be essential. Add to this the realization during Skylab 4, and practiced during Shuttle missions today, that some crew autonomy is necessary, and it is likely that an approach to the desired "thinking and exploring time" may result, even if some loss of efficiency also arises.
Many of the problems dealt with on the lunar surface arose from just a few novel conditions that manifested themselves in various nasty forms. Low gravity caused cables to stick up and get caught on feet, and also made it easy for instruments to tip over. Dust was a constant problem and caused abrasion, visibility, and thermal control difficulties. Operating in a pressure suit limited a person's activity, especially in the hands and waist. From the operations described in this document, the lessons learned are listed below.
Cables were used to carry power and commands from, and data to, the ALSEP central station. Ribbon type cables were used, and these were tightly wound on spools weeks before launch and tended to retain this "set." Normal round cables were used for other equipment, such as the television camera and the S-band antenna. All the cables were constantly getting under foot since the low gravity was not enough to cause them to lay flat. This was probably the biggest nuisance (and also a hazard) during EVA operations on the moon. After the Heat Flow Experiment was damaged by pulling the cable loose from the central station by tripping over it, the connections were strengthened and strain relief was added, but the cables themselves were still a problem. Also, instruments with a high center of gravity, such as the SIDE, were easily pulled over by the normal tension of the cables. Future missions might consider including "tent stakes" to anchor cables or instruments. Also, using some other way of transmitting data to (optical pulses? would this work in the bright lunar environment?) and power from (microwave or laser beaming?) a central station would avoid cables. If each instrument were individually powered by its own solar panels and returned data directly to Earth, as the PSEP on Apollo 11, the problem would go away. Of course, power during the night is still required for many experiments and the benefit of a common power source is considerable.
Orientation of the experiments was mostly done using a bubble level and sun compass. Leveling the experiments was generally not a problem since fairly gentle slopes were usually available. The very sensitive seismometers needed to be releveled frequently by command from Earth, especially during terminator crossing. The Far UV camera presented something of a problem in leveling. Two of its three feet needed to pushed deeply into the soil to level it. Most likely, leveling will not be a major problem in the future. It is an engineering problem that is constrained by mass available to the design.
Since Apollo missions always occurred in the lunar morning, and since the missions were short and the geometry of the sun at emplacement was known, the shadow technique worked well for directional orientation. Shadow position for the planned landing site was marked on the instruments before Earth launch. If EVAs from a future lunar base are performed under varying sun angles, a new orientation procedure for directional pointing will be needed. This could be as simple as using the same sun compass concept with updated information from MCC (except near lunar noon - during which EVAs may be restricted due to thermal loads anyway), or as complex as having the equivalent of a global positioning network around the moon. EVAs performed with only Earthshine obviously cannot use sun orientation for emplacement.
Dust got everywhere. It even got into the areas where the release bolts were located and made it difficult to even deploy some experiments. Future thermal and mechanical designs must allow for this. Dust covers that encase the entire instrument, not just a sample port, might be included that are left on until everything is set up correctly, and only then should they be removed.
Intricate manipulation was extremely difficult with the pressure suit gloves on. Even carrying the ALSEP out to the deployment site, a task which required gripping, was difficult because of the constant effort required to close the hand. Simple operations which don't rely on a closed hand will be easiest until glove design improves. Bending of the arms and wrist was also difficult. Tasks near the chest, such as putting a sample into a bag, were therefore awkward and became a two-man operation. Bending the legs was easy, but kneeling in the dust would create a housekeeping problems upon entering a spacecraft or habitat.
While the LRV worked very well, negotiating slopes sidewise was difficult for the downhill crewman who felt like he could easily fall off despite the seat belt. Also, once the mass of the LRV started going downhill, steering was marginal since the inertia would keep it going in a straight line. Perhaps the suspension can be made to compensate for some amount of side slope, and the wheel design can grab the surface more. Cone wheels seem to have some advantages and will probably be used instead of the wire mesh wheels of the LRV. If the weight of the vehicle is increased by filling empty containers with regolith would that improve traction? Would this also increase the downhill steering problem and power consumption? Is there one optimum or does it depend on the particular mission on that EVA?
Low gravity is the norm on the moon, therefore equipment easily tipped over if the center of gravity was too high and cables pulled on them. Perhaps future experiments could include "tent stakes" or incorporate pockets for weight to be added if this is a problem. The use of loose regolith as the weight could create a dust problem, so rocks, sintered soil, or cast basalt might be used as the ballast.
Digging and drilling was very difficult below the top few centimeters of the lunar regolith. The soil very quickly becomes consolidated beyond any normal soil here on Earth. Core tubes and drill stems were redesigned to work properly. To assist the removal of the long core tubes, the treadle and jack were designed. While much of this is now understood, it would be wise to reconsider how these operations can best be accomplished in the future.
Since each crewman had to place his geological samples into a bag which hung on the PLSS of the other crewman, their proximity to each other was necessarily close. Future sampling operations might benefit from allowing a crewman to place samples in a bag hanging on his own PLSS (requiring high flexibility in the suit or tools) or perhaps from using a sack that can rest on the ground with a handle that can be reached for carrying like a shopping bag. In general, teamwork which is required only due to mobility and dexterity limitations should force consideration of other ways of accomplishing the task. This could effectively double the sampling activity of an EVA team.
On foot, navigation appears to have been the most difficult problem encountered during lunar surface activities. Unexpected terrain features, as compared to relief maps available from orbital reconnaissance, were the source of these problems. The ridges and valleys had an average change in elevation of ~3 to 5 meters. Landmarks that were clearly apparent on the maps were not at all apparent on the surface. Even when the crewmen climbed to a ridge, the landmark often was not clearly in sight. During their short stay times, at least one landmark, the sun, was always in site and always reliable. This won't be the case at a future outpost when long stay times are the norm.
Later crews used the LRV, which had excellent navigation aids. A total of 5 hours was spent at traverse station stops on A-15, and the astronauts transmitted excellent descriptions of the lunar surface while in transit between stations. A-16 and 17 improved upon this. While most future EVAs can also expect to be supported by a rover, emergency walk-backs might need to be supported with better navigational aids.
In a more general sense, the interaction of experiments during Apollo created a logistical quagmire that had to be carefully considered. The magnets in the SIDE and CCG had to be a minimum distance from the magnetometer. The lunar neutron probe had to be emplaced a minimum distance from the RTG. The vibrations of the LRV due to moving the TV camera were a concern to the traverse gravimeter team. The layout of the ALSEP packages was driven by interactions of the instruments and their various orientation requirements. While intermingling many experiments from both a hardware and a timeline perspective may be necessary for efficiency, there is always a price to pay in compromising the data or operations required.
During the Apollo EVAs, the planned timelines were carefully followed by teams of mission controllers and science support people in the back rooms. Rarely were the crews "allowed" to get far behind this timeline. Some tasks, such as deploying the rover or transferring the fuel rod to the RTG, were critical, and whatever was needed to accomplish them was done. In these cases, something else had to give. That usually meant shortening the time at one of the stations on the geology traverse, or eliminating the station altogether. Some special samples were eliminated or obtained at alternate locations. It is doubtful that this much support will be provided to future crews when EVA is a daily occurance. What is lost in efficiency will hopefully be made up for in sheer quantity of time at the outpost.
As our experience with training for and performing lunar surface EVAs grew with later missions, our ability to plan realistic timelines increased. The A-14 crew said that, by the end of training, they were consistently ahead of the timeline by 25 to 30 minutes, and felt that this would be adequate to take care of the extra time that they would use on the surface in being more careful, and to allow for problems. As it turned out, it wasn't enough. "The fact is that you're just a bit more careful with the actual flight equipment." They recommended a 25 to 30 % pad.
An analysis of the three EVAs of Apollo 15 was performed and is documented in a series of charts and tables on file at the JSC History Office under the title "Apollo 15 Realtime Lunar Surface Summary Timelines, Activity Completion Percentages Attached." It compares the actual time required to complete all the tasks on the surface to the planned timelines. It also shows percentage of completion of each task and has some comments on the comparisons. A similar document could not be found in the Apollo Collection for the other missions. One would need to view the mission video and audio tapes and compare them to the timelines to get this information.
The Apollo 16 Time and Motion Study looked at the ratio of time to perform tasks related to ALSEP deployment on the lunar surface on A-15 and A-16 vs. the time the crew took on their third 1-g training session. This ratio ranged from 1.16 for simple tasks to 2.18 for more complex ones. The average ratio on A-15 was 1.41, and that on A-16 was 1.66. The difference is not statistically significant. This suggests that tasks take about 50% longer to perform under the lunar EVA constraints than in training.
A number of factors can be proposed to explain the differences in lunar EVA and 1 g training comparisons. The more obvious of these are rooted in the differences associated with lunar and Earth-bound conditions -- g level, differences in soil and terrain, visibility, etc. There are also attitudinal influences which are important. Central to these is the attitude of care or carefulness. The equipment was not indestructible and the crew had very limited repair capability. During lunar EVA the astronaut had no one to correct mistakes or to help in difficult situations, in contrast to a training session where numerous individuals were available to check experiment deployment. The simulated lunar surface at KSC was not only smoother than the actual lunar terrain, but was also more familiar and created no problems relative to site selection for experiment deployment. When on the moon, the astronaut was keenly aware of the fact that he had only one chance to complete his task, that his performance must be efficient, and that he was being intently observed by a large portion of the world population. In short, lunar EVA induced an attitude of great care in the execution of the allotted tasks.
There are also matters of rest and pacing. During training, it is not possible to continue working for very long in the suited condition. Work periods are shorter and astronauts tend to mobilize their energies for swift but effective performance. Training time, then, would tend to be shorter.
A future lunar program will have to learn from its mistakes as well as its successes, just as the Apollo missions did. It is important to build upon what we have already learned, however. This document will hopefully help us to retain the corporate knowledge of Apollo operations until we get back to do it even better next time.