Guide
Inflatable projection spheres: size, LED and rigging
An inflatable sphere works as a screen or a lamp: images are projected from outside with several projectors around it, or from inside, from the bottom, onto a diffuse surface; it can also be lit from within with LEDs. Digital Inflatables has made them between 2 m and 15 m in diameter, such as the backlit Astra Festival moon.
Contents · 5 sections
What diameter should an inflatable sphere be?
Diameter depends on how far away the audience is and on the venue: on Digital Inflatables projects it ranges between 2 m for a WAY agency moon and 15 m for the Grand Palais inflatable moon.
In between come a 4 m diameter moon set on a Jura ridge, a 5 m Earth globe and a 9-metre sphere for the Abbaye de Fontevraud, partly printed and then painted by the artist Makiko Furuichi.
For text or a logo printed on the sphere, letter height matters as much as diameter: the FHWA road sign legibility rule allows 30 ft (9 m) of reading distance per inch (2.5 cm) of letter height.
Projecting onto an inflatable sphere: from outside or from inside?
From outside, several projectors spread around the sphere cover its surface; from inside, one projector with a wide-angle lens lights a diffuse surface from the bottom, with no audience shadows.
NOAA’s Science On a Sphere set-up places 4 projectors in a square of 25.5 to 28.5 ft (7.8 to 8.7 m) around a 68-inch sphere, 90 degrees apart; with fewer projectors, one or two quadrants of the sphere stay dark.
From inside, the bottom of the sphere is reserved for the lens and the image covers 290° vertically and 360° horizontally. Quality depends on the sphere’s size, the projector’s brightness, contrast and resolution, and ambient light.
For Illuminate Adelaide, Digital Inflatables designed and made 9 custom inflatable spheres for lucion_media and developed the mapping graphics.
A similar project? Describe it to our team.
Request a quoteCan an inflatable sphere be lit from inside?
Yes: the 2 m and 4 m diameter moons made for WAY agency have a built-in LED system, and the Astra Festival moon is backlit.
LEDs suit a closed fabric volume: according to the US Department of Energy (DOE), they use at least 75 percent less energy than incandescent bulbs, emit virtually no heat, last 25 times longer and are dimmable.
The Digital Inflatables Earth globe combines internal light with continuous rotation, and the 2.4 m diameter balloon made for Gstaad changes colour as an RGB Bluetooth balloon.
Indoors, the fabric must also meet the venue’s fire requirements: the Astra Festival moon received an M1 fire treatment. Fabric choices are covered in the guide to inflatable fabrics and printing.
How do you hang an inflatable sphere in a venue?
Indoors, a sphere hangs from suspension points with a known permitted load; outdoors, it stands on the ground and is held by thin guy lines.
In Switzerland, the rigging guideline published in December 2021 with Suva has the venue operator declare the permitted loads of floors and suspension points, while the organiser has the structural calculation made.
The 4 m diameter moons and the 5 m Earth globe were hung under the roof of large halls, and the Makiko Furuichi sphere stands on thin guy lines in a courtyard of the Abbaye de Fontevraud.
Should an inflatable sphere use air or helium?
An air-filled sphere, constant-air or sealed, stands or hangs; a helium sphere floats on its tethers, but uses gas each time it is filled and falls under the rules for captive balloons.
A small blower is often enough: the WAY agency moons run on a blower of only 120 watts.
To float, one litre of helium lifts 1.02 g, envelope included. In Switzerland, a captive balloon of up to 40 m³ may not be flown within 3 km of the runways of an aerodrome without an exception; in the United States, 14 CFR Part 101 applies to moored balloons more than 6 feet in diameter.
The guide to constant-air, sealed and helium inflatables compares these techniques, power cuts included.
Full specifications
| Astra Festival moon | backlit, sublimation print, M1 fire treatment |
|---|---|
| Grand Palais inflatable moon | 15 m in diameter |
| Makiko Furuichi sphere, Abbaye de Fontevraud | 9 m in diameter |
| Spheres for Illuminate Adelaide | 9 custom inflatable spheres, with mapping |
| WAY agency moons | 2 m and 4 m in diameter, LED system, 120-watt blower |
| Front projection, NOAA set-up | 4 projectors, 90 degrees apart |
Frequently asked questions
How big can an inflatable sphere be?
Digital Inflatables has made a 15 m diameter inflatable moon, and its mirror balloons range between 0.5 m and 10 m in diameter.
How many projectors does a projection sphere need?
From outside, NOAA’s set-up uses 4, 90 degrees apart; from inside, one projector with a wide-angle lens is enough, but the bottom of the sphere is reserved for the lens.
Can an inflatable sphere glow from inside?
Yes, with LED lighting: the WAY agency moons have an LED system and the Astra Festival moon is backlit.
Does an inflatable sphere need helium?
No: a 120-watt blower is enough for the WAY agency moons, and helium is only needed if the sphere must float.
Where do you hang an inflatable sphere in a venue?
From suspension points whose permitted load the venue operator has declared, as the Swiss rigging guideline requires.
Sources
- NOAA, floor plan sos.noaa.gov
- University of Toronto, spherical display dgp.toronto.edu
- Energy.gov, lighting guide energy.gov
- FHWA, sign legibility fhwa.dot.gov
- Artos, rigging guideline artos-net.ch
- Fedlex, ordinance on special category aircraft fedlex.admin.ch
- Cornell, moored balloon rules law.cornell.edu
- UCSB Physics, helium lift web.physics.ucsb.edu
- Digital Inflatables Instagram post instagram.com
- Digital Inflatables Instagram post instagram.com
- Digital Inflatables projects page digital-inflatables.com
Drafted with AI assistance from the company’s verified facts, reviewed and approved by Jodoc Elmiger, founder and managing director of Digital Inflatables.
