580 SEEKING THE CITY

Tents: The State of the Art in Deployable

ROBERT CORSER University Of Kansas

INTRODUCTION: DEPLOYABLE SHELTER and a locking mechanism (H2, foglio 30v, 31r) as FROM PRE-HISTORY TO DAVINCI AND seen in Figure 1. It is unlikely that either the TODAY or this structure, described simply as a “padiglion” (pavilion) was intended for emergency use. It is have been a primary form of human shel- clear however that DaVinci is speculating about ter, especially for nomadic cultures, hunting par- systems of deployment that would be far more ties and military expeditions, for as long as we self-contained than a traditional tent’s assemblage have records of human activity. Cave paintings of loose parts. These proposals for more highly supply the earliest evidence of tents dating to the integrated systems may well be the fi rst example Cro-Magnon period in Europe, ten to twenty thou- of what we would today call self-contained, rap- sand years ago.1 Although nomadic peoples have idly deployable shelters. Unfortunately, no other largely disappeared, the plains of Eurasia still host graphic material exists to help further explicate numerous bands of -dwelling shepherds who DaVinci’s thinking, and as with nearly all but the utilize traditional portable shelters. In antiquity, most recent deployable structures, no physical tents came to occupy a central role in the rise evidence of any kind remains. Beyond these in- of empires and in the development of numerous vestigations, there is little evidence of efforts to cultures. The basic unit of the Roman legions was signifi cantly transform age-old approaches to tent the “contubernium,” a party of eight men sharing design until well into the 20th century. Why has a tent and a packhorse.2 The description of the the tent proved to be such an enduring solution portable temple contained in the book of Exodus and why has innovation been so rare? might serve as the archetypal description of tent technology spanning the period from biblical times ARE TENTS THE BEST STRATEGY FOR until very recently.3 In almost every recorded DEPLOYABLE SHELTER? example, tents consist of a loose assemblage of posts with layers of fabric skins held taut by lines The example of history indicates that the tent, in or cables in tension. one form or another, has long been the most wide- spread solution to the problem of deployable shel- Historical evidence of attempts at innovation in the ter. Prior to the 20th century, it is nearly impos- area of tents and temporary structures is sparse at sible to identify any other signifi cant approach to best. Leonardo Da Vinci’s more than 5000 pages of the problem. In general, tent construction offers extant drawings record studies of everything from numerous advantages, among them: simplicity, human anatomy to fl ying machines, siege engines extreme portability, and economy of means. Tents and churches. The collection “Manuscript H” con- are easy for individual users to carry, construct, tains some of his few known sketches for tents or modify if necessary, and maintain. Of course tents portable shelters.4 One view seems to show a sys- also suffer from numerous drawbacks in compari- tem for rapidly raising a fairly traditional tent with son with other possible systems, including relative a tension cables set in a ring. (H1, foglio45r) An- structural instability in severe weather and very other shows a three-dimensional view and details limited thermal performance. Since expeditions, indicating a framework that is foldable with hinges wars and emergencies are generally hoped to be TENTS: THE STATE OF THE ART IN DEPLOYABLE SHELTER 581

Because the western culture of mobility is typically associated with automobiles or aircraft, it should not be surprising that approaches to deployable shelter have also taken a vehicular track. Camp- ers, trailers, and hybrids like pop-ups all share the distinction that they are based on a fi xed chassis on wheels with much or all of their enclosed vol- ume delivered in fi nished form. The advantages of vehicular systems are that they are potentially the most stable and durable approach to deploy- Figure 1 - Roman military tents from the Column of able shelter, and they offer the possibility of the Trajan (L) and details of folding pavilion Leonardo Da most complex layered construction for potentially Vinci, Manuscript H (R) the best thermal performance. The disadvantages, however immediately outweigh the advantages for most situations, because they are the most costly, temporary situations of extremity, little interest least effi cient to deploy, and least fl exible in their has traditionally been focused on comfort or lon- use. As the FEMA trailers of hurricane Katrina so ger-term durability. But as wars, man-made and clearly illustrated, campers are slow to deploy in natural disasters and their associated population large numbers, expensive, wasteful of resources, displacements become more widespread and their and far from user-friendly. Although they might effects longer lasting, rapid shelter technology be the longest lasting option, compared with their needs to respond with better performance. high cost, they are uneconomical in the extreme.6

Do other deployable systems rise to the challenge It is still the case that the most advanced military of offering higher performance shelter than tents? forces in the world rely on tents not only for imme- Panelized, fl at-pack or folding systems, like that diately deployable and temporary shelter, but as shown in one of DaVinci’s sketches, offer some is the case with the Persian gulf wars, also as long advantages because they are potentially more term housing for personnel. The only innovations stable and durable than tents. By virtue of their evident in today’s military tent-cities appear to be more robust construction, they also offer the pos- the adoption of a semi-circular ‘Quonset ’ form sibility of more complex layered enclosure sys- for simplicity and structural integrity, and the ad- tems for potentially better thermal performance. dition of hugely wasteful air conditioning systems. The disadvantages of panelized systems seem According to a Louisiana National Guard unit, typ- to be their increased complexity, higher costs, ical army tents of today: “…measure about 100 x greater risk of construction diffi culties and more 25’ long and sleep 60 people cot-to-cot. As tents limited portability. In recent designs, the desire go, they are comfortable and robust. About every to alleviate some of theses disadvantages has third cot there is a heating/air conditioning unit.”7 produced mixed results. For example, the Global Village Shelter (GVS) by Ferrara Design, is the In the civilian sphere, the two largest organiza- most widely heralded new approach to deployable tions engaged in global disaster relief are the Unit- shelter.5 It is a fl at pack system of custom shaped ed Nations (UN) and Oxfam, and each agency’s plastic-impregnated cardboard panels that as- long-standing choices for deployable shelter are semble like a large box, approximating the shape noteworthy. In response to both natural disasters of a small hut. While this system, intended to last and long-term population displacement, Oxfam for 18 months, is marginally more durable than has maintained a policy of stockpiling corrugated a good tent, its structural geometry, like a house sheet metal for quick delivery to affected areas. of cards, is highly ineffi cient. Further, the GVS Local inhabitants and aid volunteers are then free still requires the addition of plastic tarps to water- to fl exibly deploy this economical material that proof the roof. Perhaps the greatest advantage combines structural stiffness with basic moisture of the GVS is its comforting domestic appearance. protection.8 The UN has long preferred supplying Beyond that, it offers scarcely any more stability, simple 13 by 16 foot blue plastic tarps, for similar insulation or fl exibility than existing tent designs. reasons of simplicity, immediacy, cost-effective- 582 SEEKING THE CITY

ness, and fl exibility. In fact, in current practice, structural systems and the development of new even tents are judged to be too complex by these tent fabrics. agencies. According to the UN High Commission- er for Refugees Handbook for Emergencies: FORMAL AND STRUCTURAL GEOMETRIES

“Except for tents in certain circumstances, pre- A basic rectangular plan shape with some sort of fabricated or special emergency shelter has not triangular roof pitch has long been the most com- proved to be a practical option on either cost or cultural grounds… Refugee housing should be cul- mon structural geometry for tents in the western turally and socially appropriate and familiar. Suit- world. This form has its roots in both traditional able local materials are best, if available… (and) house forms, and also in the rectangular shape Wherever possible, refugees should build their of the woven fabrics produced on hand- and ma- own housing…” 9 chine-operated looms. Since the basic cladding material often comes in rectangular pieces, the Given the priorities and attitudes of these agen- most labor effi cient way of producing tents has cies, it is nearly impossible to imagine any system long been to use these raw materials in rectangu- more complex than a tent gaining widespread ac- lar layouts. Civilizations that produced tents pri- ceptance. Their insistence on fl exibility and the marily from animal skins or felted, as opposed to importance of hybridizing the supplied systems with local materials and ingenuity are also key woven, fabrics, have tended to maintain circular concepts for future deployable shelter designs. plan forms. In Native American building cultures, Given the inherent drawbacks of panelized and examples of round teepees and far out- vehicular systems, the tent appears to remain the weigh what little evidence there is for rectangu- 10 most likely model for the provision of immediate lar tent forms. On the Eurasian plains, nomadic shelter in humanitarian applications. Rather than shepherds construct made of rings of bent trying to make fl at-pack or vehicular systems saplings clad with thick felt. These structures are simpler, more affordable, less complex, or more so sturdy that rather than being disassembled for adaptable; the best approach for higher perfor- transport, they are often lifted and moved intact mance rapid shelter seems to be the making of on the back of wagons. better tents. The inherent structural rigidity of circular forms as EMERGING DEVELOPMENTS IN TENT compared with rectangular ones is fairly obvious. DESIGN Yet, modern attempts to revive circular forms for deployable shelters in both civilian and military Analysis of emerging trends in the areas of mili- applications, like Buckminster Fuller’s Dymaxion tary research and civilian innovation in tent de- Deployment Units, have failed to gain wide ac- sign reveals new potential directions for the cre- ceptance. Fuller’s later Geodesic Dome research ation of higher performance, but still practical tent sought to combine circular plan and semi-circu- technologies. In military engineering, relatively lar cross section shapes with the rigidity and re- little attention has been paid to housing as op- peatability of triangulated systems. Although this posed to other more specialized needs like mobile approach found a receptive audience in the US hospitals and the protection of supplies and deli- Military, and numerous proposals were publicized cate machinery like aircraft. The US military per- showing his domes being deployed by helicopter forms most of its deployable shelter research at for every imaginable purpose, its use in prac- the Natick Soldier Center in Massachusetts. Their tice was limited largely to the protection of radar work is closely tied to parallel and collaborative equipment in arctic deployments.11 The drawbacks efforts in private industry and academic research of Fuller’s dymaxion system for rapidly deployable institutions. While non-military research into de- shelter appear to have included the number and ployable shelter systems has been sponsored by complexity of joints between structural elements, aid agencies in the past, the bulk of contempo- and the complexity of cladding the dome. rary work in this sphere is independent and spec- ulative. Cutting across the boundaries between In contrast to circular plan forms, semi-circular these different research initiatives, two clear and roof shapes have fared much better. Although promising directions are evident: advances in there is evidence of curved or arching tent roof TENTS: THE STATE OF THE ART IN DEPLOYABLE SHELTER 583

This approach puts greater stress on the arches that defi ne the overall cross sectional shape, but solves problems with lateral stability along the length of the cylindrical form. Work in this area, along with basic research into the performance of fabric tension arches and other deployable tent morphologies, is being performed by the Light- weight Structures Unit, a collaboration between the Berlin Kunst Institut and the University of Figure 2 - Global Village Shelter by Ferrara Design (L) Dundee in Scotland.13 One good example is their and Geodesic dome pavilion at Vitra (R) recent work on a new shelter system sponsored by the UK Ministry of Defense, described by the forms in some Native American cultures, it was researchers as a: the US Navy’s civil engineering battalions, based in Quonset Rhode Island, who popularized this “…very lightweight, rapidly deployed, small to me- effi cient roof form during world war two.12 The dium size shelter system (that) uses as the prin- ‘Quonset Hut,’ widely deployed as a semi-perma- ciple structural member, a transformable fabric web braced arch to support a double curved me- nent building with rolled corrugated metal serving chanically prestressed membrane skin. The result- as both structure and skin, is also the model for ing truss is reversibly transformable from a linear the shape of most contemporary military tents. fl at state to its erected two-dimensional form due The advantages of the Quonset hut lie mainly in to the elastic bending of the rib… The truss pro- vides the basis for a very stiff, lightweight, foldable its formal simplicity and its inherent structural structure, packable to a small volume.”14 stability. It is also a shape that accords with cul- turally preferred rectangular plan forms, and that Their approach seems particularly promising be- is capable of being made relatively simply from cause it is a hybrid, combining a simple arch-sup- rectangular materials. ported Quonset hut shape with highly advanced solutions for the arch structure. Research in the basic structural shapes of tents has focused primarily on arched, domed or semi- Their design also generates double curvature domed structures that employ some amount of in the fabric between the arches, thus assuring double curvature to increase structural stability. greater overall rigidity and stability. The “Quonset hut” form, composed of a simple half cylinder, employs only curvature in one direc- MATERIALS RESEARCH BOTH FOR STRUCTURE tion. Generating anticlastic double curvature for AND ENCLOSURE stability in tensile structures has been the sub- ject of both civilian and military research for sev- For millennia, tent materials have consisted of eral decades. The hyberbolic paraboloid form, a compressive frame elements, tensile strands for structurally stable form of double curvature pro- stability and integrity, and pliable skins for enclo- duced by opposing upward and downward forces sure. Frame materials have ranged from animal maintained in balance on diagonally opposite cor- bones in early examples, to the predominance of ners of a stressed fabric, is popular for shading structures, but has found few applications in de- ployable shelters largely because of the need for heavy anchoring points to resist the high tension stresses induced in the system. New research in fabric structures is focusing on ways to gener- ate a second direction of curvature for structural stability in designs based on a simple rectangular arched form.

By inducing curvature perpendicular to the arch- Figure 3 - Lightweight Structures Unit research: Fabric es, a sort of hourglass or scalloped shape can web braced arch (L), Studies of double curvature morphologies (R) be generated in the typical Quonset hut form. 584 SEEKING THE CITY

wood in most cultures.15 Tensile forces have been tem derives its stability from the circular domed handled by animal products or twined fi bers in the form, and the architect recommends adding a fur- form of ropes. Twentieth century developments ther layer of local material to weatherproof the have substituted steel, aluminum and fi berglass exterior. Due to its thermal mass, this system is for compression, and steel fi bers or plastics such well suited to warm climates, but Khalilli claims as nylon for the tensile elements. Further devel- that the system will also work well when fi lled opments have involved the creation of lightweight with snow. Although based on deployable fabric metal trusses for structural spans or arches. elements, this system is clearly not a tent per se. It does however represent a much more durable Recent research sponsored by the Natick Soldier approach that gives priority to local materials and Center has also focused on ways to quickly de- involves end users quite directly in its construc- ploy more traditional metal arches by combining tion. Super Adobe’s major drawback seems to hollow metal truss tubes, hinged together with be the amount of time necessary for deployment, stressing tension cables that run through the bot- making it more useful for the longer-term housing tom (inner) chord of the arched truss. Working of displaced people than as a rapidly deployable together with a stretched tensile skin, this kind emergency shelter. of system can almost literally unroll to produce a sturdy structure that is very lightweight, but made With the possible exception of Super Adobe’s of incredibly intricate and complex assemblies.16 thermal mass, the major drawback of all tents is In the civilian sphere, Chuck Hoberman’s far more the ineffi ciency of fabric as a large scale environ- elegant and even more complex deployable and mental enclosure. Traditional tents are based on transformable shelter systems based on scissor local materials and systems developed to work mechanisms, represent the state of the art in me- with particularized weather conditions. In cold cli- chanically unfolding space trusses and geodesic mates, furs or heavy felts were used while around domes.17 All of these avenues however, seem to the Mediterranean, light colored breathable fab- lack the important aspect of structural simplicity rics like linen predominated. Early modern de- that has always been central to tent design. Be- velopments involved the use of waxes and other cause of its simplicity, the Lightweight Structures treatments to improve water and wind resistance Unit’s previously described fabric arch research and other treatments to provide fi re resistance. seems more promising in the area of arched truss New materials offer a much wider range of envi- design. ronmental responsiveness.

An alternative approach, also being undertaken by Directionally selective materials that are chemi- the US Military and its suppliers, involves the re- cally similar to GoreTex but are also fi re retardant, placement of structural metal arches with infl ated like ToddTex and Tegraltex, can maintain water re- fabric tubes called “air beams.” Once fi lled with sistance from outside while allowing the release of compressed air, the air beams do not need con- water vapor from inside an enclosed space. New stant replenishment, and the pressurized elements materials have also begun to offer improved ther- form a framework that is clad with a loose fabric mal insulation by refl ecting unwanted radiant heat enclosure.18 Although materially effi cient, these away in hot climates or keeping heat refl ected to air-beam tent systems require highly specialized the inside in cold weather. Here again, promising fabrics designed to hold high air pressures without new research is under way at the Natick Soldier leaking or being threatened by punctures. Center. A simple camofl aged tarpaulin intended as a temporary shelter and concealment for for- The general concept of site-fi lled fabric contain- ward scouts and snipers not only protects soldiers ers gets an interesting twist in the work of Ira- from the elements, but also hides their ‘thermal nian-born California architect Nader Khalili. One signatures’ from enemy sensors. Although details of his inventions, called “Super Adobe,” consists of of the material innovations of the “Stealth Surveil- fabric tubes that are fi lled with earth and stacked lance Shelter”20 remain classifi ed, this research in spirals to form earthen domes.19 Each layer is might eventually lead to much more thermally re- secured to the previous by barbed wire placed in sistant fabrics for civilian uses. between to act as mortar or nails. The overall sys- TENTS: THE STATE OF THE ART IN DEPLOYABLE SHELTER 585

Yet no matter the insulation value of a single layer of fabric, achieving the kind of sophisticated en- vironmental responsiveness possible in layered building skins of greater mass and thermal re- sistance will remain a diffi cult challenge for de- ployable shelters. For moisture control, civilian tents have long featured double walled designs with a fully vented airspace between waterproof outer and breathable inner layers. But this con- trols moisture only, giving little if any additional Figure 4 - Thermally responsive low-pressure pneumatic thermal benefi t. By capturing multiple layers of skin, invented by Nickolaus Laing air, and effectively managing the transmission of thermal energy between those layers, the perfor- “The remarkable energy effi ciency of high bright- ness solid state lighting (HBLEDs) means that a mance of even the most thermally insulating fab- bright digital light of 80 lumens per watt (bright ric can be greatly improved. enough to read, work and illuminate areas at night) can be produced by a single miniature diode An interesting approach to thermal adjustability and powered by small areas of fl exible photo-vol- taic (solar) panels.”23 was developed in the 1960’s but has yet to be widely tested. Developed by Nikolaus Laing, this It is clear that this emerging technology could concept involves a low-pressure pneumatically easily be integrated into the fabric of deployable infl ated skin that contains multiple sub-bladders emergency shelters intended for devastated areas capable of selective infl ation in order to maximize where infrastructure, whether preexisting or not, solar shading or solar gain depending upon lo- would be unable to provide power for lighting or cal climatic conditions.21 Inner bladder surfaces other necessary uses. It should not be surprising of differing opacity can be opened or closed like that the military is also following up on this area venetian blinds against either the inside or out- of research, including research into weaving the side surfaces in order to adjust the penetration of photovoltaics directly into the fabrics themselves sunlight into the airspace. With the outer surface in the form of photovoltaic fi bers, a unique break- shaded, sunlight is refl ected away and the bladder through for dye-sensitized nanocomposites.24 becomes a cool insulating layer. With the inner surface closed and the outer one open to sunlight, CONCLUSION the bladder works as a greenhouse, trapping warmth in the airspace in cold climates. This kind For millennia, the tent has been the most widely of thermally selective system, although somewhat employed solution for rapidly deployable shelter. complex and as yet untested, might serve as an Although different forms like the yurt or the tee- inspiration for the kind of innovations needed in pee are identifi able, the basic approach of using a order to further improve the thermal performance lightweight framework to support some sort of a of tent enclosure systems. fabric skin, has always been maintained. Among the major benefi ts of tents are their simplicity, Finally, with new developments in photovoltaic portability, adaptability, and cost-effectiveness. and battery technologies, it is possible to imag- ine tent fabrics that can serve not only to control thermal gains and losses, but that can also pro- duce useful energy. The “portable light project” a collaboration between architect Sheila Kennedy, textile designers, and the electronics industry, has resulted in a prototype for a simple and durable source of light, powered entirely by fl exible pho- tovoltaic panels sown into a fabric handbag.22 Ac- cording to the project’s website:

Figure 5 - Portable Light Project (L) and fi rst generation fl exible photovoltaics in military tent applications (R) 586 SEEKING THE CITY

Although tents have been gradually adapted over 10. Nabokov, Peter. 1989. Native American Architec- centuries to better serve highly localized environ- ture. New York: Oxford University Press. mental conditions and cultural needs, there is little 11. Gorman, Michael John. 2005. Buckminster Fuller: evidence of signifi cant innovation even throughout Designing for Mobility. Milan: Skira; London: Thames & the fi rst half of the 20th century. New research Hudson. in improved structural systems and higher perfor- 12. Decker, Julie and Chiei, Chris, editors. 2005. mance enclosure systems have produced isolated Quonset Hut: Metal Living for a Modern Age. New York: Princeton Architectural Press. results but no wholly new approaches to tent de- sign have yet to emerge. Perhaps the state of the 13. Kronenburg, Robert, editor; co-edited by Lim, art in tent design will be revolutionized by hybrid Joseph and Wong Yunn Chii. 2003. Transportable Envi- ronments 2. London; New York: Spon Press. approaches that combine effi cient structures with thermally responsive and energy producing skins. 14. “The fabric web braced arch is a composite, tensile restrained, post-tensioned truss, utilizing a thin fl exur- Although there are numerous possible responses ally stiff member elastically deformed to a transition- to the growing need for better deployable shel- ally curved arch (the rib). The rib is stiffened in this ters, the inherent simplicity and portability of the geometry and prevented from further large defl ections tent, combined with provocative ongoing research by a specifi cally shaped, bias-cut, fabric diaphragm (the web). The resulting truss is reversibly transform- initiatives, are clear indications that the future of able from a linear fl at state to its erected two-dimen- rapid shelter is likely to come in the age-old form sional form due to the elastic bending of the rib. This of a tent. is initiated by the web which is discretely attached to the chord on movable sliders contained within a ‘luff’ groove on the underside of the compression member.” ENDNOTES http://www.arch.udk-berlin.de/lsu/index.html

1. Hawkes, Jacquetta Hopkins. 1993. The Atlas of 15. Hawkes, Jacquetta Hopkins. 1993. The Atlas of Early Man. New York: St. Martin’s Press. Early Man. New York: St. Martin’s Press. 2. Keppie, L. J. F. The Making of the Roman Army: 16. Natick Soldier Center. http://nsc.natick.army.mil/ From Republic To Empire. London: B.T. Batsford. media/fact/content.html 3. (Exodus 4:26) Yahweh tells Moses to make a taber- 17. Bloemink, Barbara; Hodge, Brooke; Lupton, Ellen nacle, a portable sanctuary and “Tent of Meeting” made and McQuaid, Matilda. 2007. Design Life Now: National of sheets of fi ne twined linen, fi nely brocaded with Design Triennial 2006. New York: Cooper-Hewitt Mu- cherubs on a framework of Acacia wood uprights, 10 seum Smithsonian Institution. cubits high, bronze plated at the ends with two bronze 18. http://nsc.natick.army.mil/media/fact/shelter/Air- bottom tenons fi tting into silver sockets… Joint Com- beam.pdf mittee on the New Translation of the Bible. 1970. The New English Bible: the Old Testament. London: Oxford 19. Adams, Cassandra and Elizabeth, Lynne. 2000. U.P./ Cambridge U.P. Alternative Construction: Contemporary Natural Build- ing. New York: Wiley. And: http://www.calearth.org/ 4. Leonardo Da Vinci, 1452-1519. Manuscript H, emergshelter.html in: The Notebooks of Leonardo da Vinci / Arranged, Rendered into English and Introduced by Edward Mac- 20. http://nsc.natick.army.mil/media/fact/shelter/SSS. Curdy. 1939. New York: Reynal & Hitchcock. pdf 5. Ferrara, Daniel. 2001. Global Village Shelter. GVS 21. Dent, Roger Nicholas. 1971. Principles of Pneu- Website http://www.gvshelters.com. Also in Design for matic Architecture. London: Architectural Press. the Other 90% (exhibition catalog). 2007. Cynthia E. Smith. New York: Editions Assouline. 22. Smith, Cynthia E. 2007. Design for the Other 90% (exhibition catalog). New York: Editions Assouline. 6. Kaye, Jeffrey. 2007. “Controversy Continues over Post-Katrina Spending on Trailers.” http://www.pbs. 23. the website goes on to say that “Portable Light org/newshour/bb/weather/jan-june07/katrina_04- expands the value of miniature solid state electronics 09.html by putting digital light into a textile medium to create cost effective, completely portable, off-the-grid light 7. http://www.la.ngb.army.mil/1244th/244th test web engines that can be deployed at a global scale wher- page_fi les/page0009.html ever energy effi cient electrical power and illumination are needed.” http://www.portablelight.org 8. http://www.oxfamamerica.org/whatwedo/emergen- cies/indonesia/what_oxfam_is_doing 24. http://nsc.natick.army.mil/media/fact/shelter/Fl- exPhoto.pdf 9. United Nations High Commissioner for Refugees. 2000. Handbook for Emergencies (2nd Edition). para- graph 70, p.144. New York: UNHCR. http://www.unhcr. org/publ/PUBL/3bb2fa26b.pdf