Have Moonsuit, will travel
by Dwayne A. Day
|Connors and Eppler sought to “set the record straight about Apollo EVA” and learn something about it from the astronauts who walked on the Moon.|
Now that NASA is planning on sending humans back to the Moon in five years, they will need new spacesuits. The suits regularly used for spacewalks on the International Space Station cannot be used on the Moon for various reasons, including the fact that the legs don’t bend. NASA has studied planetary spacesuits off and on ever since Apollo, but usually not in much depth. Although there was some planetary spacesuit research performed as part of the Constellation program, it ended several years ago before proceeding to a full prototype spacesuit. Planetary spacesuits are not simple pieces of equipment, and the Apollo program highlighted many of the difficult engineering challenges.
In the early 1990s, after NASA had been given lunar marching orders by a previous President Bush, the agency had consulted with a number of its surviving moonwalkers about designing extra vehicular activity (EVA) systems for the lunar surface. Their recollections were compiled in a 1993 summary document. Its lessons are still valid today.
The authors of this document, Mary Connors of Ames Research Center and Dean Eppler of Johnson Space Center, explained that they conducted the study to offset what they called two “syndromes that affected some (by no means all) people in the exploration program.”
The first was what they called Apollo Nostalgia Syndrome, or Appollonious Memorilapsus, an affliction that struck white males in the 50–60 year age range who could remember little about what, if anything, they had done with Apollo EVA. The second was Apollo Ignorance Syndrome, Appollonious Ignoramous, which struck males under 40 who had been with the agency less than ten years. “Symptoms are a blank expression, and the repetition of the phrase, ‘What do you mean we went to the Moon once!?’”
Connors and Eppler sought to “set the record straight about Apollo EVA” and learn something about it from the astronauts who walked on the Moon. So they extended invitations to the surviving moonwalkers and seven of them responded. The astronauts were Apollo 11 moonwalker Buzz Aldrin, Apollo 12’s Alan Bean, Apollo 14’s Ed Mitchell, Dave Scott from Apollo 15, Charlie Duke from Apollo 16, and Gene Cernan and Jack Schmitt from Apollo 17.
The former astronauts agreed to participate in a half-day session. This started with a briefing about NASA’s baseline lunar mission in 1992, known as First Lunar Outpost (see “The last lunar outpost”, The Space Review, March 15, 2004). They were then asked to conduct a hands-on session with various pieces of EVA equipment. This included the Apollo spacesuit, known as the Extravehicular Mobility Unit (EMU), the Shuttle EMU, and advanced EMUs. They were also interviewed for approximately two hours. The hands-on session was intended to jog what Connors and Eppler called “physical memories,” or what it was actually like to move inside the spacesuits. This also included a session with the Apollo glove, the Series 4000 glove, and advanced development gloves, all mounted inside a glove box where the atmosphere had been removed, resulting in the glove puffing up like a balloon, just like in actual operation.
The interviewers sought to develop a consensus to be used in planning future EVAs. They discussed topics such as mission approach and structure, EVA suits, the life support systems for the suits, the use of automation in the suits and life support systems, information displays and controls, lunar rovers, EVA tools, operational procedures and philosophy, and training.
|The Apollo astronauts also felt that they had been too rigidly scheduled during their missions and that this should change for future lunar missions.|
The moonwalkers said that future lunar mission design philosophy should include the complete system, achieving a seamless integration of the crew into the facilities and the equipment, with the equipment designed to fit the tasks that the crew is assigned, rather than the opposite. They emphasized that simplicity and reliability were important, with routine tasks and simple emergencies driving the design, not worst-case scenarios. The crew should also be “essentially autonomous” and take a more active role in planning the mission than they had during Apollo.
The Apollo astronauts also felt that they had been too rigidly scheduled during their missions and that this should change for future lunar missions. A two-man crew should be the basic unit, although they thought that contingency EVAs performed by a single moonwalker were reasonable. They also felt that EVAs lasting seven to eight hours every other day were acceptable, and most of them felt that conducting them every day was the way to operate. The Apollo 15 astronauts had conducted the first seven-hour EVA. Apollo 16’s astronauts had conducted two surface EVAs of this duration, and Cernan and Schmitt had conducted three EVAs over seven hours long. However, they felt that the schedule depended upon the crew’s autonomy. On Apollo they had to stay on a rigid schedule, but in the future it should be up to the crew to decide if they were safe and ready for a day’s work.
The astronauts felt that when it came to designing EVA suits, simplicity and reliability were the most important factors. They believed that the key to suit flexibility is low operating pressure and a pure oxygen atmosphere. They thought that variable pressure suits were an interesting concept that held potential, but were unacceptable if they were not simple and reliable. There was no consensus on the suit mass. Some felt that the Apollo suit’s mass was too high, whereas others thought that it was acceptable.
The Apollo spacesuits were essentially disposable—after the last EVA they were not reused and in fact both the astronauts and suit engineers were shocked at the amount of erosion the suits had suffered in their moving parts due to abrasive lunar dust. The moonwalkers stressed that maintenance simplicity was a key design provision for long duration missions. They also were somewhat mixed about more advanced suit designs, such as hard suits, rear-entry suits, and docking a suit to the outside of a hab. The rear-entry design, where the life support backpack of the suit swung open to allow the astronaut to slide into the suit, made it easy for a single astronaut to don his suit unassisted. This is the approach that the Russians take with their Orlan spacesuit, and it was also the approach chosen by the Soviets for their Krechet lunar EVA suit. But many of the moonwalkers were concerned that the large seal would be damaged by lunar dust.
One possible method for keeping lunar dust out of the habitation module was to keep the spacesuit outside, “docking” it to the habitat module. Although the former astronauts considered this to be an interesting idea, they felt that it required more study.
Any spacesuit consists of two major components: the pressure suit itself and the Personal Life Support System, or PLSS. The moonwalkers gave the Apollo PLSS high marks for reliability, functionality, and capabilities. They felt that future PLSS design should stress low mass and high reliability.
|Another subject that the astronauts were passionate about was the spacesuit gloves. They all felt that the gloves they had used were barely adequate and better gloves were necessary.|
They were also asked about the possibility of recharging their PLSS during EVA, but some of them were skeptical. They thought that this could reduce mass, but they were concerned about safety and leaving the hab on a long EVA without enough consumables to make it back. They also ruled out the use of umbilical oxygen tubes as unworkable and dangerous.
There was one subject that the moonwalkers were in violent agreement about: lunar dust was a major problem. It got into everything and was very abrasive. They suggested keeping equipment exposed to dust separated from the living quarters. Suits would have to be cleaned after every EVA, both inside and out.
Apollo 17 astronaut Harrison Schmitt has publicly talked about the minor respiratory problems he suffered from the dust, which he has compared to having allergies. Although the moonwalkers did not consider the dust they encountered during their short surface stays to be a health issue, they conceded that it could be hazardous on a longer mission, posing problems such as silicosis.
Another subject that the astronauts were passionate about was the spacesuit gloves. They all felt that the gloves they had used were barely adequate and better gloves were necessary. The Apollo gloves imposed major limitations on hand mobility, finger dexterity and tactility, and resulted in serious arm fatigue. This began within minutes of the start of the EVA and continued throughout the day. They approved of the improvements in the Series 4000 space shuttle gloves compared to the Apollo glove, but felt that more work was necessary. Custom gloves are a necessity—in fact, it is current NASA policy to produce custom gloves for all astronauts training for EVAs. Although the Apollo astronauts were intrigued by the possibility of end effectors instead of gloves, they felt that they required greater study.
The moonwalkers also said that tool control was difficult, with the major problem being gripping the tool. The Apollo glove made it hard to grip the tools, and hand tools caused much fatigue. They thought that it was an absolute must that there be a way of holding the tool in the hand without continuous gripping.
The moonwalkers were not opposed to increased use of automation, but they still wanted manual backups and overrides. They agreed that automated suit checkout was a good idea. They also liked the idea of visual displays for displaying task information, and aural alarms to notify the astronaut of problems. They also felt that heads-up displays and voice-activated controls were interesting, but were concerned that this would add complexity and possibly overload the moonwalker. Electronic checklists were a good idea, but they had to be updateable.
Three of the Apollo missions included rovers. The astronauts who used them agreed that loading, storage, and access to tools was not very good on the rovers. They also felt that the rovers had to be repairable with dedicated tools. Nobody wanted to repeat the makeshift repairs that Cernan and Schmitt had to make to their lunar rover using such supplies as maps, tape, and clamps borrowed from utility lights.
They also felt that experiments should be sturdy. Several pieces of equipment had been damaged by the astronauts who were clumsy in their big spacesuits. They felt that problems with equipment or experiments on Apollo could have been avoided if they had understood the effects of one-sixth gravity. During their missions the astronauts also found that storing samples was problematic, especially when they were in a hurry. One of the astronauts recommended that a simple shopping bag with handles would have been very useful.
When it came to operations, crews on long-term missions required greater autonomy. They needed to hold a daily planning meeting with the operations and science personnel, plotting out the next day’s activities based on previous results. Several of them were frustrated that there was never enough time to properly investigate a given site, and felt that it was important to give the crew as much time as necessary to document and investigate the exploration site.
The astronauts considered it possible to walk back to the hab from distances as far as 20 kilometers. They also felt that operating under Earthshine or lunar noon were feasible, as long as thermal conditions were understood. They also thought that teleoperation of robotic rovers should be integrated into operations planning.
When it came to training, the former astronauts were emphatic: “Train hard: you’re going to the Moon or Mars, dammit, not on a vacation!” Many of the moonwalkers had been in the military and repeated a lesson that had been hammered into them there, and they had seen work well in the field: practice everything “so you don’t have to make it up as you go.”
|When it came to training, the former astronauts were emphatic: “Train hard: you’re going to the Moon or Mars, dammit, not on a vacation!”|
Those discussions with the Apollo moonwalkers took place over a quarter of a century ago—in fact, more years have passed since the astronauts all gathered at NASA to talk about EVAs on the Moon in the early 1990s than had passed since those men had walked on the Moon—an indication of just how long NASA has been discussing a lunar return. When President George W. Bush announced in 2004 that the United States would begin a new effort to eventually return Americans to the surface of the Moon no later than 2020, the people tasked with that job immediately began addressing how they would accomplish it. NASA held several discussions of lunar operations in the spring of 2005 and again called on some of the astronauts who had walked on the Moon three decades before. In particular, at a public hearing in April 2005, a special committee tasked with outlining the steps needed to return to the Moon heard presentations about some of the proposed lunar surface equipment that could be used, including a talk by Apollo 17 astronaut Harrison Schmitt and Apollo 17 commander Gene Cernan, who participated by telephone. But the Apollo astronauts are dying out, and are no longer the resource they once were.
Since the early 1990s, NASA has gained a tremendous amount of EVA experience and made efforts to improve glove dexterity for tasks such as the Hubble servicing missions. In the late 2000s and into this decade, NASA also went through another period of planetary spacesuit study and design, although that work succumbed to bureaucratic morass. If the current plans for a return to the Moon do not fall apart, NASA will once again spin up its spacesuit efforts and review their previous work, possibly going all the way back to Apollo. If they choose to talk to any of the remaining Apollo astronauts, according to Connors and Eppler, they will likely hear about one requirement that the astronauts felt outweighed all the others: “Better gloves, better gloves, better gloves.”
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