Edge of darkness

Plans are afoot to light up the night sky this November. But four days after Guy Fawkes’ Night, the illumination will not be due to fireworks but a 27m solar reflector resembling a giant umbrella. It is due to be launched into space later this month and will beam sunlight on to cities which would […]

Plans are afoot to light up the night sky this November. But four days after Guy Fawkes’ Night, the illumination will not be due to fireworks but a 27m solar reflector resembling a giant umbrella. It is due to be launched into space later this month and will beam sunlight on to cities which would otherwise be in darkness.

This is the second in a series of experiments which will, if all goes according to plan, culminate in the launch of constellations of vast solar reflectors capable of providing as much light as 100 full moons.

This light could then be shone on places around the world, either where sunlight is minimal for example, in the polar regions, which are enshrouded in darkness for up to six weeks during the winter months or where there is no terrestrial power infrastructure, such as in remote areas of developing countries like China and India.

The project is being run by the Space Regatta Consortium (SRC), a group of Russian organisations based in Korolev. Principal funding has come from Russian aerospace giant Rocket Space Corporation Energia in Korolev.

‘A space illumination system has advantages over terrestrial power sources in that it produces an instant infrastructure and is less harmful to the environment,’ says Christopher Faranetta, deputy managing director at Energia. ‘It does not burn fossil fuels and it gives out less waste heat a factor which must be taken seriously in a world which is quite possibly undergoing global warming.

‘Extending daylight hours in the polar regions will increase the efficiency with which people move around in the cities. It may also help reduce crime and accidents, and it may even encourage a second working shift.’

It is also believed a space illumination system could help relief efforts after large-scale industrial or natural disasters and during law enforcement and anti-terrorist campaigns.

The main aim of this year’s experiment is to test a means of deploying and controlling large structures in space. The experiment is called Znamya (Banner) 2.5.

The technology being tested is based on the use of centrifugal force. The reflector, which is made of a thin aluminised plastic similar to Mylar, will be folded into a small package for transportation into space. Once it is in position the package will be released and spun. The centrifugal force caused by the spinning will deploy the reflector, which will unfurl into a flat surface with a large area.

Znamya 2.5 will be carried into space aboard the Progress Automated Cargo Vehicle (Progress M-40) when it takes supplies to the Mir Space Station in September. Three months after arrival at Mir, Progress-M will be filled with rubbish and undocked. Under normal circumstances it would then fall out of orbit and burn up in the Earth’s atmosphere. In November it will first act as an experimental platform.

Once Progress M-40 reaches a safe distance from Mir, the cosmonauts on the space station will initiate deployment of the reflector. If this is successful they will then use teleoperation methods to point the reflector at specific targets on Earth.

‘They will control the reflector much like a stagehand controls a giant spotlight,’ says Faranetta.

Since the reflector will be orbiting the Earth at 17,000mph, its attitude needs to be constantly adjusted to account for the movement if light is to fall on one place for any length of time. Otherwise the light would be no more than a flash as the reflector passed overhead. The aim is to fix the spot on chosen cities, which will include London, Kiev and Calgary, for a duration of five minutes.

The reflector will complete 16 orbits during the 24-hour experiment before burning up in the atmosphere. It is expected to produce a spot of light about 6km in diameter which will be as bright as 10 full moons.

A similar experiment took place in 1993, but the last reflector, Znamya 2, was only 22m in diameter and its attitude could not be controlled. The edges of the new reflector’s panels, arranged like pieces of pie, will also be bowed to prevent gaps appearing between them, which occurred during Znamya 2’s deployment.

Reflected light sightings

Many people reported seeing the reflected light during the previous experiment though, due to heavy cloud cover, it was not very bright. Also, because of poor publicity, few people knew what they were seeing in the sky and a number of them thought that they had seen a UFO. This time Energia is trying to get the word out before the experiment.

The next stage will be the launch of Znamya 3, a 70m reflector, in about 2000. To accommodate a reflector this size, modifications will be needed on the Progress M-40.

The final stage in the experiment will be the launch of clusters of 12 reflectors, each 200m in diameter. Together these would shine as brightly as 100 full moons to provide enough light for five large cities.

Preliminary estimates show an experimental illumination system from space could bring profit within two to three years, according to information on the SRC web site. But this presumes that conventional illumination serving big cities could be reduced by half.

The proposals have brought criticism from environmentalists and astronomers. The UK’s Institution of Lighting Engineers emphasises the energy efficiency of modern public lighting and calls the mirror concept ‘polluting and unnatural’.

But Energia’s technologists say the idea is not to provide 24-hour daylight, but that the system is likely to be used initially to extend daylight in polar regions during the winter.

There would be other applications for the technology used in the space illumination system once it has been proven, SRC hopes. All depend on the technology to enable large structures to be deployed and controlled in space.

The 200m solar reflectors could, for example, be used as the basic component of solar sails to propel spacecraft on interplanetary or interstellar missions. ‘Once a spacecraft manned by solar sails has escaped the Earth’s atmosphere it would continue to accelerate without the need of burning rocket fuel,’ says Faranetta. ‘The very large surface area and low mass of the sails means that the pressure exerted on them by the solar wind (the stream of particles emitted by the sun) would be great enough to propel the spacecraft in the vacuum of space.’

SRC estimates the flight of the first solar sail to escape the Earth’s gravity could take place between 2003 and 2005. It calculates that the cost of building, launching into near Earth orbit and operating a solar sail would be less than $100m.

The technology behind the solar reflectors could also have applications in space-based astronomy, says Faranetta. He predicts that one day it will be possible to manufacture a giant mirror in space for use in space-based telescopes.

‘Reflector-type structures would be sprayed with mirror materials and cooled in the microgravity environment of space. By solidifying away from the distorting effects of gravity, high-quality, very precise mirrors could be made,’ he says.

Lightweight deployable structures resembling the reflectors could also be used as antennas for space-based telescopes. Such telescopes are set in orbit in space where they are away from interference caused by the communication satellites on Earth and well positioned to listen to noise coming from the universe.

The technology being tested in Znamya 2.5 could also be applied in giant thin-film photovoltaic solar cells which could be used to provide energy to Earth. Such cells in orbit around the Earth could be used to convert solar energy to electric energy. This would be transferred to the ground as microwaves, converted back into electrical energy and fed into the national grid.

The Progress Automated Cargo Vehicle carrying Znamya 2.5 is scheduled for launch this month with the illumination experiment set to take place on 9 November.

The SRC hopes it will win support from other organisations and international space agencies wishing to participate. To date, the European and French space agencies have shown an interest.