BBC News Magazine August 17, 2005
Is the Shuttle green?
The Space Shuttle crew have been warning of the destruction of the Earth's environment. But what damage does it do to get a shuttle into space in the first place?
By Zoe Smeaton
Observing the planet from her vantage-point in space, Discovery Commander Eileen Collins spoke last Thursday of the environmental destruction visible on Earth, likening the atmosphere to "an eggshell on an egg, it's so very thin". She added: "We know that we don't have much air - we need to protect what we have."
But is Nasa itself really observing this need for the protection of Earth as it sends shuttles into orbit?
The image of a shuttle at lift-off, enveloped in clouds of exhaust, is now iconic. As crowds gather to witness the dramatic displays as shuttles are made airborne though, many may wonder whether all those exhaust fumes are damaging our environment.
'Eco-friendly' main engines
According to Nasa, the Space Shuttle Main Engine design, three of which powered Discovery, is "the most advanced liquid-fuelled rocket engine ever built".
The fuel used by these engines is super-cold liquid hydrogen, kept at a temperature of -253C, which Nasa reports is "the second coldest liquid on Earth".
Inside the engines, this hydrogen fuel is combusted with liquid oxygen in a reaction that reaches temperatures of up to 3136C, "hotter than the boiling point of iron". This creates a high-speed stream of gas which ultimately generates the thrust necessary for launching the shuttle.
Professor George Fraser, director of Leicester University's Space Research Centre says this exhaust gas, made from the combination of hydrogen and oxygen, consists of water vapour and as such does not harm the atmosphere, making the use of Nasa's main shuttle engines fairly environmentally safe.
Fuel cell technology is often thought of as being an answer to the world's energy problems. Carbon dioxide can, however, be a by-product from the production of hydrogen, depending how it is made.
Discovery was also made more environmentally friendly by the use of a certain type of insulating foam on its surface.
Before 1997, Nasa preferred to use freon-based foam on the shuttles, but as a chlorofluorocarbon (CFC), freon is now linked to ozone depletion and so has been phased out. Opting to follow Environmental Protection Agency guidelines, Nasa switched to an environmentally friendly version of the foam.
Despite these factors, however, all shuttle launches can nonetheless have damaging impacts on the local environment.
Hydrochloric acid
Professor Fraser said: "The classic example of environmental impact is in Kazakhstan at the Baikonur launch site, where there are reports of quite serious environmental damage."
For most shuttles, the damage comes from the solid rocket boosters, or SRBs, require at shuttle launch to provide 71.4% of the thrust at lift-off and elevate the shuttle to an altitude of 45km (28 miles).
As a shuttle launches, a "cloud" becomes visible which contains SRB exhaust products, either dissolved or as particles in the water vapour released by the main engines.
Hydrochloric acid formed in this launch cloud leads to acidic deposits in the surrounding area, a phenomenon which may also be observed some distance away if exhausts are carried on prevailing winds.
John Pike, president of GlobalSecurity.org, and an expert on the US space programme says: "The hydrochloric acid can pit the paint on your car if it is too close to the launch site."
A 1993 Nasa technical manual considered environmental effects of space shuttle launches at Kennedy Space Centre, and stated that some cumulative effects of launches in the nearby area are "reduction in the number of plant species present and reduction in total cover".
The manual also pointed out that acid deposits from the launch cloud can also impact nearby water lagoons and their wildlife.
If hydrochloric acid is deposited, the pH value near the surface of the water may drop and prove too acidic for fish, although these impacts on wildlife do "appear minimal and manageable".
Professor Fraser points out also that while shuttles may cause a small amount of damage to the ozone layer this will be "far less marked than that from the large number of high altitude aircraft in the World all the time".
© Copyright 2005, BBC
