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ABSTRACT
Our purpose in this paper is to develop an approach which will promote more timely, and wide ranging human presence on the Moon. In the event that the nation does not commit itself to a fully equipped Lunar Base, the hostel approach described herein could offer a less expensive alternative, a minimal but functional "tended beachhead", a humble yet significant step beyond the Apollo achievement. "Hostel", a term for sheltered sleeping space available to traveling campers, here refers to a pressurized structure offering minimally and inexpensively furnished "Big Dumb Volume" space for the private and communal use of visiting staff. The concept co-signifies a visiting vehicle to be close-coupled to the hostel for the duration, to provide a complementary "Small Smart Cranny" component. Such a partnership promises to allow hostel and vehicle to function conjointly as an integral, reasonably complete outpost in support of exploration, scientific research, prospecting, and processing experiments, allowing longer, more comfortable stays at minimum expense. In some later time of expanding presence, roadside hostels would facilitate safer, more regular travel between fully equipped distant outposts or settlements across the globe. By not duplicating equipment and facilities that are standard equipment aboard the visiting spacecraft, both the total amount of cargo landed on the Moon and the number of crew EVA hours necessary for establishing a given level of capability, are minimized. Thus the hostel approach has the potential to keep the economic threshold for an initial operational beachhead significantly lower than in other mission paradigms.
We have four objectives:
- to define the logical division of functions between visiting vehicle and shelter,and how these differ with the particular purpose of the hostel and the prospects for its future
- to define design constraints on the visiting vehicle. Such co-design will be necessary if the potential of the hostel approach is to be realized
- to outline logical paths of evolution towards stand alone status
- to examine possible architectures, whether for prefabrication on Earth or for construction on the Moon using native materials.
INTRODUCTION
During the six Apollo Moon landings, the landing craft did double duty by offering minimal camp shelter on the exposed surface. The Lunar Excursion Module, or LEM, offered hammock-type sleeping and enough floor space to permit two whole steps at a time in a single direction. No one has yet slept in a bed on the Moon, or taken an indoor walk, basic humble everyday functions. As shelter from the elements, this Grumman-built lunar camper protected those within from the incessant soft mist of micrometeorite infall and from the Sun's ultraviolet rays. It actually offered negative protection from cosmic rays or the occasional solar flare, for its thin unshielded hull served as a source of troublesome secondary radiation.
After a lengthy retreat, we now propose to return in style with a fully shielded permanently staffed base complex long on scientific and experimental capability and exploration support, but short on personal and communal space. Several missions would be required to set it up and render it operational As has proven to be the case with the Space Station, such overreaching skip-step designs must inexorably work to defeat the timeliness of their realization. Is there indeed a middle ground, a reasonable set of design choices which will lower that threshold enough to let us get on with the show within this generation? The hostel paradigm combines the complimentary assets of a relatively inexpensively equipped but more spacious shelter space with base-relevant compact and expensive standard equipment aboard a coupled visiting spacecraft or other vehicle in a synergetic partnership that allows the two to function together as an integral "starter base". The hostel paradigm is offered as a strong statement, even a protest, about the need for more elbow-room in lunar outposts than the more orthodox approaches can affordably provide. But to evaluate the feasibility and practicality of the hostel concept, we have to explore both sides of that special relationship, consider how this dynamic balance may change over time, and suggest how it might be realized in the concrete.
I. THE VISITING VEHICLE
Design Constraints
The design and outfitting of the visiting vehicle is critical to the workability of the hostel concept. The visiting craft must close-connect with the hostel structure if the facilities and equipment it brings are to be used to support any sort of practical routine,and the linked pair are to function together in an integral way. Exercising reasonable precaution, a visiting spacecraft would land a prudent distance from the waiting shelter. Even bridged by some sort of pressurized passageway, the tens or hundreds of meters between would prevent efficient use. Thus craft must be designed (a) to "taxi" en masse to the porch step of the hostel, or (b)* to lower a conveniently underslung detachable crew compartment, with its relevant equipment, to the surface so that it can separately taxi the distance on a chassis provided for the purpose. We suggest that this is the design choice to make, as it leaves the unneeded and ungainly landing frame, with the rocket engines and primary tankage, sitting on the pad site. When the crew's visit to the hostel is completed in a couple of weeks or months, this mobile cabin would uncouple from the shelter and taxi back to the pad site, reconnecting to the waiting descent/ascent portion for the trip back to LLO or LEO. To highlight the amphibious space/surface character of such a vehicle configuration, we have dubbed it the "frog". The descent/ascent stage could also be designed to take off without the crew module, picking up a new one at LLO or LEO. The original crew compartment vehicle would continue to serve as a lunar surface transport. This "toad" version, would require a more rugged chassis, more serviceable engine, and some sort of refueling arrangement. If we are to settle the Moon in a self-leveraging way,"toads" introduced to serve remote outposts, may be the ideal 'dues-paying' way of importing the surface craft needed before the settlement is able to self-manufacture its own coaches. Thus, whether the crew's came through open space or across lunar terrain, the vehicle that actually couples with the hostel structure will be functioning as a surface vehicle at the time.
KEY: 1 Frog (detachable mobile crew cabin) wheel on right retracted, wheel on left extended
2 Winch to lower/raise frog
3 Main rocket engines
4 Fuel tanks - 5 Oxidizer tanks - 6 Cargo pods
7 Overhead crane/winch for cargo
8 Central clear-vision area for top viewport navigation
Frog vehicle docked/coupled to Hostel under shielded open-vac canopy for duration of crew visit.
1 Frog - 2 Hostel - 3 Canopy - 4 EVA airlock - 5 Open-vac rover
The frog/toad/coach arriving on site could
- be designed to hard-dock, in which case it must
- be able to level, orient, and align itself properly for the task, and
- be able to either lock or deactivate its suspension, perhaps with retractable legs. (If the suspension were allowed to continue floating, the hard-dock seal would be under continual stress with personnel moving back and forth.) Alternately, the vehicle could
- be designed to link-up with the shelter via a somewhat
flexible and alignment-forgiving, short pressurized vestibular
passageway
- extending from itself to the shelter, or more logically
- tele-extended from the shelter to itself by a prompt from within the vehicle. There would seem to be engineering, weight, and safety tradeoffs between these hard- and soft-dock options and we do not suggest which would be the more practical in the short run..
Outfitting constraints
To play its part, the coupling vehicle be outfitted in a way that the capabilities it offers are complementary to those offered by the hostel shelter. It would seem that the repertoire offered would vary according to the customary length of trip for which the vehicle was designed. The possibilities suggest two general classes, the 'commuter and the traveler.
(1) Commuter class vehicles would include shuttlecraft plying between the lunar surface and either an orbiting depot or a more substantial orbiting mother craft such as an Earth to Moon (or LEO to LLO) ferry. Also fitting the description would be suborbital hopper linking mutually remote lunar sites. In either case the commuting craft is occupied for only a few hours at time. Thus it may not contain berthspace, galley (though food stores are likely to be a major part of the cargo), or head, though some emergency-use only arrangements would be a prudent option should the craft go astray or be forced to land far from its destination. Even here, we have a vehicle which could bring something to a hostel partnership. For both shuttle or hopper will have communications, navigation, and computing equipment which do not need to be duplicated in the hostel. And either will likely have an emergency first aid compartment complete enough to serve the crew in its hostel stay, as well as other emergency survival provisions. Finally, its air recycling equipment (a water recycling capacity is less likely) and ventilation fans, might easily be oversized without too much weight penalty, so as to also serve the hostel space well enough in a close-coupled configuration.
(2) Traveler class vehicles would include landing craft that consists of a shuttle module delivering a "through-cabin" crew-module transferred from an Earth-Moon (LEO-LLO) ferry. As on the coast to coast Pullman sleeper cars switched from one railroad to the next in an era now long gone, the crew coming to staff the hostel would ride the same "through-cabin" all the way from LEO, or even all the way from the Earth's surface. Also in the cruiser category is the "overland" coach (from an established settlement or full base) designed for trips cross-lunar excursions of a day or more in duration. In either scenario, the visiting craft will contain serviceable if cramped "hot-rack" berthspace that can serve in the hostel-hookup as emergency infirmary beds if isolation or quarantine is called for. And certainly the craft will have at least a minimally equipped galley and head (possibly with shower) as well as a compact entertainment center with some recreational extras. Such more fully equipped vehicles would serve especially well as hostel complements, leaving the hostel to provide what it can offer most economically and efficiently: hard shelter from the cosmic elements, and plenty of elbow-room to serve the less expensive low-tech but space-appreciative aspects of daily life -- private bedrooms and communal areas for dining, gaming, exercising, etc.
II. THE HOSTEL'S SHARE OF THE WORKLOAD
General Philosophy
Approaching the suggested vehicle-shelter functional partnership from the point of view of the hostel itself, we must keep in mind both the economies to be gained by keeping the shelter as low-tech and inexpensively simple as possible while still serving its purpose, and the competing consideration that we might want it to design it so it can evolve over time into a fully configured autonomous base. The underlying concept of the lunar hostel is that base functions can be physically and spatially separated into two broad types.
(1) Cranny-loving functions. The first includes the compact but expensive equipment that is needed to maintain human existence outside our native biosphere, to maintain the health of the crew, to support the crew's scientific and exploratory research tasks, and to maintain contact with the rest of humanity from which it is physically isolated. The whole evolution of vacuum-worthy craft has been to make such equipment ever more compact and lightweight while ever more functional, productive, and capable. This first category thus principally includes those things that the crew must always have access to, whether it is settled-in on the Moon, or in transit between Earth and Moon, or simply orbiting the Earth.
(2) Room-loving functions. In contrast, there is a second broad category of functions which principally includes those things that are not missed in the short run (and so need not be provided for periods of the order of Earth-Moon transit times or shorter) but are needed over the long term (and thus are ideally provided by durable in-place shelter to be visited for extended periods. These are the functions which, because we lacked the lifting capacity or out of sheer economic necessity have been at best shoe-horned-in on spacecraft and orbiting stations, but which for personal and group morale and psychological well-being should really be offered on a far less space-stingy basis: honest to goodness personalizable private quarters with ample space to move about, arrange one's personal effects, display (if only for oneself) any personal treasures or hobbywork; pleasant dining, assembly, and meeting space (wardrooms); quiet places for reading; places for shared entertainment or gaming; places for space-hungry exercise routines. These long-term needs were necessarily ignored on Mercury, Gemini, and Apollo because the space to serve them could not be set aside. Nor have such spaces been more than suggestively and teasingly provided on the Shuttle or even aboard the relatively voluminous Sky-Lab. True, sardine-can packing can be sustained even for months if there is light at the end of the tunnel, as ample submarine experience has demonstrated. Yet it hardly contributes to morale. More to the point, such elbow-to-elbow jostling may prove to be much less tolerable over any length of time in settings where the outside environment is one of unsurvivable desolation, however magnificent; where a play of sterile grays and blacks, is nowhere relieved with soft and friendly greens and blues; where there is no wildlife to be found at all, not even 'alien'. Space Station planners have endeavored to give some consideration to these needs, exploring design innovations that might make the station's unavoidably cozy spaces more human. Since on the Moon, the task of maintaining individual and communal morale and mental health will be much more challenging than in low Earth orbit, if there is a way to provide both more generous private and communal space - not just workspace - without undue expense, it should be prioritized. It is our premise in this paper that by not unnecessarily duplicating equipment and facilities already needed aboard the visiting craft to sustain life in space, appreciable dollar and fuel savings can be gained which can be spent to this purpose.
Gray Areas
Before we consider how in the concrete such liberal campspace shelter can be offered (that is, building materials, construction methods, architectures, and deployment options), we wish to consider some gray areas, facilities and outfitting whose proper placement - in the coupled visiting craft or in the hostel space - might be debated. We did not attempt to reach definitive answers. But in each case we list considerations that seem pertinent.
(1) Communications/computer center: The need for redundant systems is inarguable. But there placement may be a matter for dispute. Accepting that the hostel would never be occupied without a visiting vehicle coupled to it, one might still argue that the various systems aboard the visiting craft necessary to maintain life and contact with metropolitan humanity should be duplicated within the base structure itself as a matter of simple precaution. Here one should keep in mind that spacecraft systems are already by themselves provided redundantly. But the point might still be made that the coupled spacecraft is unshielded and therefore could be knocked out by a rare meteorite of sufficient size. A testy rejoinder would be that anyone that concerned about remote possibilities, doesn't have 'the right stuff' and shouldn't volunteer for such duty. But accepting the challenge made, we can more constructively reply that it would be possible to offer shielding protection, not to an intact conventional lander, but to the detachable crew-compartment become bus (i.e. the frog or toad), under a shielded but vacuum-exposed carport-like canopy extension of the hostel structure. Such a "ramada" would also shield routine doorstep and porch outside activities: outside vehicle maintenance, storage areas for surplus supplies and discarded items; items awaiting shipment, etc.. But if such sheltered parking space is provided, the vehicle's antenna would be effectively blinded. Therefore the hostel must be equipped with the necessary antenna(s) for joint operation.
(2) Electric Power Generating Capacity: The power systems aboard the docked vehicle will be sufficient to take care of its own needs in transit, probably via fuel cells with a couple of weeks of emergency reserve power at best. While the activities the hostel itself is designed to support within its own confines will consume relatively little power, and even less to run whatever minimal housekeeping equipment, if any, is needed in between visits, we are left with some real challenges.
- (a) Compact workstations aboard the vehicle may need more power when the vehicle is parked and functioning as an integral part of the base combo than when it is in transit.
- (b) If the landing vehicle does have a modest solar power array, this is most likely to be a part of that apparatus left on the pad. Connected to the detachable crew compartment or frog, such arrays might be effectively disabled if the frog docks with the hostel underneath a shielding canopy out of sunlight's reach, as recommended.
- (c) Nightspan power needs must be taken into consideration, even if these are minimized by apportioning base operations into energy- vs. labor-intensive tasks reserved for dayspan and nightspan respectively. Thus for a stay of any real duration, the location within the integrated base (frog or hostel) where the power is actually consumed becomes irrelevant. The apparatus to generate it and store reserve supplies will be weighty, no matter which path is taken. Therefore principal power generation and reserve storage must be the contribution of the hostel component, with the apparatus necessary a part of the original hostel endowment package. This hostel-provided power system could also electrolyze whatever water that had been generated in the frog's fuel cells en route to the hostel, so that its hydrogen and oxygen fuel reserves were fully replenished for the return trip. Any surplus gas could be stored in shielded tanks outside the hostel as a handy and welcome fuel/water reserve for the next visitation. Under this arrangement, fuel cells aboard the frog, which would go off-line for the duration of the coupling, would be fully available as backup for short routine repairs to the principal system or for 'mayday' emergencies.
(3) Air Quality and Ventilation: Any crew-rated spacecraft is going to have redundant systems serving this need. It would seem that it would be cheaper to oversize these aboard the visiting vehicle so as to handle the extra coupled volume, than to install separate and independent air management systems in the hostel. However, it may be necessary to put complimentary equipment in the hostel to dehumidify and sterilize the air within after the crew departs, so that the next crew to visit doesn't walk into a dank and moldy place. An automatic cycle that would dehumidify and then heat the air to perhaps 70o C for a relatively short time would possibly do the trick, allowing the air to stand without further treatment or control until the next visit, when a short, perhaps vehicle-assisted procedure would restore the proper humidity, temperature, and ionization level. This still allows the bulk of the equipment needed to treat air currently being used to be housed by the visiting craft.
(4) Thermal Management Systems: This need includes tasks that could be appropriately apportioned between the partner elements. With suitable architectural attention, the hostel could be built and shielded to be thermally stable. Between occupations, the hostel could either be designed so that the interior temperature falls to that of the the surrounding soil blanket (-4oF or -20oC). Alternatively, the hostel could be designed to harvest and store heat from dayspan sunlight so as to coast at some higher but still level still on the cool side but from which recovery to (and maintenance of) comfortable room temperatures will be easier and quicker. Most of the activities for which the hostel space is designed to make room should generate little heat. If the coupled vehicle is parked under a shielding canopy, extensive heat rejection arrays for excess heat generated within might likewise be unnecessary. But if a thermal surplus is expected nonetheless, the radiators indicated would best be a hostel feature, easily integrated with a solar array, or possible placed on the permanently shaded underside of attached ramada areas. Meanwhile, the control apparatus could be housed in the visiting vehicle if it doesn't require much space, since the vehicle already houses ventilation and air quality apparatus which would have to be integrated with the thermal management system.
(5) EVA Airlock and Open-vac Rover: An airlock for suited exit onto the surface needs to be a part of any functioning lunar base. For this purpose, if the visiting crew vehicle already has its own EVA airlock as standard equipment in addition to its docking adaptor, as seems likely, this should serve the joint vehicle-hostel operation quite adequately. The hostel need only have a docking adaptor and connecting vestibule with which to interface with the visiting vehicle. Personnel would then exit onto the surface through the coupled vehicle. Again the hostel would not be occupiable without the pressurized vehicle attached, and any contingency which is likely to make the latter unusable or unenterable, is likely to doom the combined base at any rate. In sum an additional airlock as part of the hostel proper, would be an option of definite eventual value but not an immediately pressing need. If not original equipment, such an accessory could be added latter, as part of a docking port extension, as increasing use of the facility and the prospects for its evolution into a fully equipped base warrant. For exploratory sorties to nearby spots of geological interest of resource potential or for recreational change-of-scenery jaunts, a separate unpressurized Apollo-type rover would be carried along by the first vehicle to visit the readied hostel, to be left on site.