INFLATABLE TECHNOLOGIES FOR SCULPTURE IN EARTH ORBIT
A number of artists have made proposals for creating monumental artworks to be placed in Earth orbit which could be seen with unaided vision by those on Earth. While there has been a variety of technologies suggested most of the proposals have utilized some form of inflatable space technology.
The idea of using inflatable structures goes back to the first Echo satellites launched by the US in the 60's - although a number of inflatable concepts for space applications pre-dated these satellites. These were passive communication satellites and carried no other payload. However, they were significant because, in addition to their scientific objectives, many people actually saw these quite visible objects passing overhead in the night sky.
Echo 1A launched on August 12, 1960 was a sphere with a diameter of 30.5 meters made out of metallic coated plastic film called Mylar which was 0.0127 mm thick and gave a total mass of 76 kg.
Echo 2 launched in 1964 incorporated improvements in satellite surface fabrication and overall shape, and featured a larger diameter of 41 meters and had a total mass of 256 kg.
Echo-1A and Echo-2 continued in orbit until 1968 and 1969, respectively. Reflected light from the Echo satellites, essentially spherical "mirrors" in orbit, was extremely bright and could be observed from a wide range of points on Earth due to relatively high orbital altitude of 1,000-2,000 km. As a result, Echo-1 and -2 became well-known among sky-gazers as representative artificial satellites of the 1960's.
There are several problems with the use of Mylar as a material for inflatable objects in orbit. First, its hydrocarbon basis is attacked by oxygen atoms in lower orbits and long exposure to UV light causes it to degrade becoming brittle and opaque. So a new polyamide material called Kapton was developed which had more resistance to this problem and Kapton has since been used successfully. Most of the gold foil material you see on spacecraft and satellites is usually Kapton.
Two other problems affecting the use of inflatable structures in orbit are atmospheric drag and the potential for meteorite penetration. To minimize atmospheric drag one must select an orbit well above 300 km or the atmospheric drag will immediately de-orbit the structure. Of course a higher orbit has less atmospheric drag but in order for the sculpture to be visible, a higher orbit also means a larger structure and this increases both the manufacturing and launch costs.
Furthermore, a "stiffer" object will be more stable and more resistant to the effects of atmospheric drag. The advantages of "stiffness" combined with a possible solution to the penetration problem by meteorites and space debris led to the development of a new kind of inflatable space technology and an exotic material referred to as "Inflatable Space Rigidizable Structures" (ISRS) also called "Chemically Rigidizable Expandable Membranes" ( CREM) structures.
This ISRS material is a laminated sandwich of metallic coated Kapton and Kevlar which has been impregnated with a UV sensitive resin . The material is very lightweight and flexible permitting it to be easily folded and packaged. Once it is inflated in space, it must "cure" in sunlight which causes the resin to harden and the membrane to rigidize which stabilizes the shape of the inflated object. In the late 80's and early 90's this technology was under development at Contraves Space A.G. in Switzerland which was funded by the European Space Agency. Recently, several companies in Europe and in the U.S. have renewed their development of this type of technology.Orbital Sculptures Using Inflatable Technology
In the mid 80's several proposals for large orbital sculptures were made that utilized some type of inflatable space technology.In 1986 - the Eiffel Tower Corporation held a competition for an orbiting space sculpture to celebrate its 100th anniversary. The winning entry was submitted by a group of architects from Paris called "Groupe Spirale" led by Jerome Gerber who proposed a large circular structure named: Anneau de Lumiere or Ring of Light consisting of 100 Echo like balloons connected to a thin tubular ring approximately 7.6 km in diameter. Placed in a 700 km orbit this sculpture would appear to an observer on Earth as a circle slightly larger than the Moon. French artist Pierre Comte was the second place finalist with his Arsat a 45 m rectangular solar sail that would have created a bright artificial star in the sky. Dieter Kassing proposed a 50 meter in diameter Space Disk with Morse Code message. Also designed a bright blinking star in the sky.
Ultimately the design Anneau de Lumiere proved to be too unstable to maintain its shape in orbit and, as there was also much resistance from the astronomers, the project to celebrate the Eiffel Tower Anniversary with a visible orbital artwork was eventually canceled by the Eiffel Tower Corporation.
For the 1990 Goodwill Games, artist James Pridgeon proposed an orbital sculpture called the "Goodwill Constellation" which connected several inflatable spheres along a tether creating a precise line of lights in the sky.
In the mid 80's I proposed to celebrate the new millennium by placing "Circle in the Sky " which would be visible to the entire Earth's population as a symbol of planetary unity and peace. I called this sculpture the Orbiting Unification Ring Satellite or O.U.R.S. It was designed to be a global artwork including participation by artists from all nations in the world in its development. Thus the acronym "OURS" also stood for "belonging to us".
In 1986 I got into contact with Contraves Space A.G. in Switzerland and with their chief engineer of inflatable technology development - Dr. Marco C. Bernasconi - who later joined my project as vice president of the OURS Foundation.Subsequently, to meet the requirements of space deployment and visibility we designed the O.U.R.S. using ISRS technology to be a continuous torus with a diameter of 1 km and a ring thickness of 10 meters. Placed at a 400 km orbit this structure would be visible to viewers on Earth as a "Circle in the Sky" approximately 1/4 the size of Moon. With a magnitude of -7.28 the sculpture would have been much brighter than the brightest star Sirius which has a magnitude of -1.142, or Jupiter -2.0 or Venus -4.4.
The ISRS material that was available at that time had an area/mass ratio of 0.2 kg/m2 resulting in a total launch mass of approximately 19,739 kg. Such a structure would require the total payload capacity of an Ariane 5 or Titan 4 launcher. Since then, advances in CREM materials have reduced the mass of such a sculpture by approximately 35% and, while the mass is less, the volume of the packaged sculpture would still require most of the payload volume of either of these launchers.In the development of the O.U.R.S. project we planned to fly a smaller "prototype" version of the sculpture in order to test both the concept and the technology. Contraves Space A.G. had developed a six-meter ISRS torus for testing purposes. As most of the technical design work had already been done I proposed to Contraves to build a similar structure for our prototype project which was called the "OUR-Space Peace Sculpture". This sculpture was circle divided by a central cross - a symbolic form which was the astronomical symbol of the Earth and an ancient symbol found in many cultures . As the Cold War was still going on and "space" was seen as a great environment for international cooperation, the idea was to launch the sculpture to the Mir space station and have a cosmonaut deploy it during a space walk with the deployment being transmitted by video to Earth. In 1988, I signed a preliminary agreement with the Soviet space officials at Glavkosmos for the space flight of the sculpture. However, due to some technological uncertainties, Contraves turned out to be very slow in committing to the project and the Soviets had their own inflatable technology which they promoted very strongly. The material they were using was a type of thick space rubber that required permanent pressurization. In 1984, they had successfully flown two 20 m diameter inflatable antennae on a Progress vehicle shown above. The Russian engineers said they were also developing a rigidizable inflatable technology as well. Subsequently, in 1990 NPO Energia, built and delivered to the OURS Foundation a full size mock-up of the sculpture which we were able to inflate and display to space and art communities on several occasions.
Our target date for the deployment of the OUR-SPS was in 1992 to celebrate the International Space Year. To make a long story short, the dissolution of the Soviet Union resulted in many uncertainties in that time frame which affected sponsor support for the project. In the end the project had to be postponed.
However, this development and the connections established with the Russian space program led to the spaceflight of my Cosmic Dancer Sculpture on the Mir station just one year later in 1993.
In the meantime, the idea of the launching the O.U.R.S. did not die. Some years ago, before anyone knew it was going to be filmed, the producers of "Lord of the Rings" contacted the OURS Foundation to see if I was still working on the O.U.R.S. project and that they might be interested in putting a "ring" in the sky to announce their new film. However, it was quickly realized that the costs of an Ariane 5 and the costs of manufacturing such a sculpture in a such short time was not possible.Recently, there has been renewed interest in the space community for inflatable and rigidizable space structures. The OURS Foundation was asked to re-examine the O.U.R.S concept and to suggest feasible alternative designs to the continuous torus concept. This study, which was completed in September 2003, looked at several new designs for inflatable sculptures that would create a visible "circle in the sky" and have a mass in the vicinity of 4,000 kg. One of these designs is shown above.
As the "new space age" begins in ernest, the demand for inflatable space technology will increase. Solar Sail missions launched from Earth orbit to destinations throughout the Solar System, orbiting Solar Power Satellites supplying terrestrial civilization with the necessary clean energy and maybe even visible art works may become the "signs of the times" in the sky as all of these may rely on inflatable structures.
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©copyright archphoto-Arthur Woods