A new fulldome presentation system offers advantages over boring old "video projection on a dome" projection systems.
The heart of the new system is the Digital Micro-Mortar Device (DMD) electro-mechanical chip. Each DMD contains nearly one million carfully alligned mortar tubes, each of which can launch a microscopic shell which is similar to a fireworks charge. Through careful miniaturization, each fully loaded DMD chip is slightly smaller than 1 cm square.
Light production element
Shells have launch charge, a delay fuse, and a charge of flash powder. They are manufactured in green, red, blue, and 'dud'. Since the DMD launches its entire load of shells at one instant it is important to launch something from each tube to prevent instabilities. By pre-loading a DMD chip with the proper arrangement of shells it is possible to fire a full-color image into the space above the DMD. When the individual mortar tubes are properly splayed out near the edge of the chip, the outermost shells arch over the audience and flash below head height, thus eliminating the 'spring line' common in conventional planetarium presentations. Note there is no planetarium dome; the shells explode in open air in a dome-shaped space above the audience.
While a single DMD can offer a colorful picture, the presentation would be entirely static and quite brief -- a mere 'flash in the pan'. To present longer-format programs with moving images additional DMD chips are added to the system -- the firing of each DMD is similar to a video frame. All the chips are identical except for the arrangement of colors in the shells, thus allowing for efficiencies in production. Rather than forcing the theater to stock pre-loaded DMD chips in all possible combinations, a rapid micromechanical loading system selects the proper combination of colors and loads the mortar tubes in the DMD shortly before use. DMD chips are arranged on a wheel and go through the load, fire, cool down sequence once per second.
Conventional digital theater presentations sometimes suffer from audio sync problems. This system eliminates this problem, and indeed saves the cost of conventional amps and speakers, by using the sound of the shells directly. Thus the theater need not be concerned with the exact time-of-flight calculations -- the flash of each shell coincides exactly with the report. Each color of shell is available in LOUD or ..sssh.. versions; the loader selects the proper combination under computer control. To produce the full audio range, the DMD firing rate in the theater is increased to 44,100 frames per second to synchronize with the audio sampling rate. This slightly increases to size of the rotating wheel (to approximately 14 meters) to accomodate the 44,100 DMD chips. The wheel is driven by a high-horsepower stepper motor.
Conventional theaters offer 16-bit audio with mere stereo or 5.1 channel sound whereas the DMD theater has sound coming at the audience from literally a million directions (but at only 1-bit sample depth). Audience members do not need special glasses to view the presentation, but since they are in an area with 44 thousand million explosions per second, are offered motorcycle helmets with sound-reducing earmuffs built in. These earmuffs are specially designed to have flat frequency response across the audible range and offer approximately 120 dB volume reduction. These helmets also protect audience members from the occasional misfire.
Since audience members will be essentially inside an explosion for some 40 to 50 minutes, they might experience some discomfort due to heat. To counteract this adequate ventilation must be provided. Therefore, after signing the necessary wavers, having an opportunity to purchase optional short-term-life insurance, and donning fire-retartant coveralls, audience members are strapped to a grid (conventional chairs would impede airflow too much) and suspended above counter-rotating high speed turbines. The updraft from these turbines -- some 35-40 miles per hour -- also helps waft the smell of spent powder away from the audience. Thunderdome theaters will be easily identifiable from the outside due to their distinctive dome-shaped containment vessel, the cooling towers, and the surrounding high voltage power lines.
Loading and firing of the DMDs is controlled by a cluster of quad-core computers running Microsoft Vista Ultimate Super Special Edition. One computer is required per pixel displayed. To reduce expenses sound cards may be omitted from the computers. Substantial power savings may be achieved by routing all the computers through a million-input KVM switch.