Architect Teresa Hoskyns and formTL engineers have developed a large-scale mobile tent called ‘Lunar Dome’ for the Apollo 11 roadshow. The structure will enable visitors to relive the milestones of the moon landing via a 3D video show.
In 1969, Apollo 11 took the first humans to the moon—an event that moved the world. On the occasion of its 50th anniversary, the roadshow has been planned through several cities in the United States to allow visitors to experience the moon landing first hand.
The venue is provided by a mobile theater tent, conceived by architect Matthew Churchill and designed by Hoskyns. With its considerable size, accommodating 1600 visitors, the Lunar Dome was conceived as a temporary structure. One particular feature of this lightweight tent structure with its membrane skin is that all its individual elements are optimized for quick assembly and easy transport. This applies both to the outer skin and to the 3D 360-degree projection dome inside the structure. The supporting steel structure, substructure, outer skin, and projection surface along with the ethylene tetrafluoroethylene (ETFE) foyer façade for the mobile theater were developed by consulting engineers formTL from Radolfzell.
Tent roof under arch supports
Four steel trussed arches form the supporting structure for Lunar Dome. The greatest load of the 73-m (240-ft) long theater tent is borne by both main arches, which are arranged in the central area, symmetrically inclined and visible from the outside. These have a span of 55.8 m (183 ft) and at their highest point they tower up to 27 m (89 ft) above ground.
At the front and rear side of the Lunar Dome above the foyer and backstage area are located two more approximately 11-m (36-ft) high trussed arches. All four arches consist of rectangular framework elements connected together with bolts. Steel cables link the whole structure to keep the arches in position. The base points of the arch frames are pin connected to the steel base plates that are anchored into the ground with large pegs and serve as a foundation. The formTL engineers paid attention to ease of assembly in their plans: the individual segments of the arch supports can therefore be composed with plug-in connectors while lying on the ground. They are then erected with cranes, positioned over the foundation plates, fastened to the foundations with bolts, and finally locked with steel cables.
The skin of the tent roof consists of a polyvinyl chloride (PVC)-coated polyester fabric approximately 4900 m2 (52,743 sf) in surface area. It is coated white on the outside and black on the inside. To transfer the load of the enveloping surface to the structure, steel ridge cables are integrated into the membrane beneath the arched support structure. Realized as double cables, they simultaneously serve as a field joint. While translucent ETFE cushions close off the foyer to the outside—front wall supports up to 10 m (33 ft) height beneath the trussed arch bear the cushion façade—the membrane above the backstage area provides tension on the opposite side. It is anchored to the ground at its base points with pegs. The projection dome in the interior, with a diameter of 46 m (151 ft) and 15 m (49 ft) in height likewise offers an impressive spatial sensation for visitors. It consists of a sound-absorbing PVC-coated polyester membrane that was also optimised for easy set-up. A large-format cut-out toward the backstage area allows a clear view to the screen located behind it (Ground Control).
For assembly, the first stage involves the individual panels being connected on the ground with shackles, then electric winches integrated into the arch supports pull the membrane upwards on so-called boomerang mountings. They are attached to the ridge cables of the membrane. When the membrane dome has reached its final position the mountings are bolted onto the cross struts of the trussed girders. The membrane is then tensioned onto the arch bases where it is attached.
The lightweight concept by formTL meets the ideal requirements for the Lunar Dome. The video projection dome forms a protected space where visitors are carried quietly back to the time of the first moon landing. Additionally, the light construction made from a supporting steel structure and a membrane skin enables the flexibility needed, so that the Apollo 11 roadshow can be moved quickly and easily.