By Zoe Smeaton
BBC News Magazine
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?
Discovery launches amid clouds of exhaust emissions
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".
The International Space Station, and Earth, as seen from Discovery
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.
NASA SHUTTLE FOAM
1997: US Environmental Protection Agency ordered many industries to phase out use of Freon
2001: despite an exemption from CFC ban, Nasa continued to use 'green' non-freon-based foam
2003: seven astronauts died when Columbia disintegrated upon re-entry - an investigation reported thermal protection system damage was initiated by sheared off foam striking the wing
2005: non-freon-based foam fell from the Discovery shuttle shortly after launch, and repairs were needed in space
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.
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 Global Security.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."
The scenes of dead fish in Spain could be repeated next to launch sites
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".
Add your comments on this story, using the form below.
Compared to the vast benefits of the space program to conservation here on Earth, I feel that it can be safely suggested that the damage to the environment from these launches is relatively negligible. Although some damage to the local ecosystem can be expected it is almost certainly very limited and has been taken into account for the Space Program.
Peter Humphreys, Cobham, Surrey
Nice to know the Shuttle exhaust isn't damaging the enviroment. I am wondering what damage is done to the Global enviroment by producing all this hydrogen though? There must be a fair amount of enegry used to chill and pressurise the tanks?
Ian Bonham, Gibraltar
But how is the liquid hydrogen manufactured and then maintained at such a low temperature? Because of inevitable inefficiencies in the manufacturing and storage processes, this is bound to use more energy from fossil fuel than the total energy that the rockets use to lift the Shuttle into orbit. Damage to the atmosphere from the release of carbon is thus greater than if the Shuttle burnt fossil fuel direct. While the radiative forcing element of burning fossil fuel at altitude will be missing, the release of vapour at altitude also contributes to the formation of clouds, which also raises the temperature of the atmosphere.
Peter Thomas, London
We are in danger of getting onto the environmental and PR bandwagons here. Compared to the destruction on the rainforests, the close to home environmental degradation through all sorts of human activity and waste, any damage that may be caused by the launch of a few shuttles every few months will pale into insignificance. The benefits that come out of this programme far outweigh any environmental impact. Lets keep things in perspective.
William, Patagonia, Argentina
Since there are only two shuttles left, their environmental impact is minimal. To put things in perspective, there are underground fires around the world that are even more polluting. If we could find a way to put them out, we'd do a lot more for the environment.
John Airey, Peterborough, UK
Although the shuttle take-off without doubt requires a remarkable amount of energy, I'm sure compared to global usage it is a small number. Understanding of the climate system and its response to human burning of fossil fuels (particularly the associated increases in CO2) is getting better all the time, but there still remain some open scientific questions. Observation of Earth from space will help refine the debate about how our climate system operates and changes, and aid policymakers in decisions as to what constitutes "safe" levels of emissions. If shuttle missions are used to place Earth observing Satillites in orbit to provide this data, the little extra energy used achieving this will be worthwhile.
Chris Huntingford, Wallingford
Describing the main engines as "eco-friendly" is misleading. It's true that they only release water vapour as exhaust, but producing such vast quantities of super-cooled liquids consumes extremely large amounts of energy. We must consider the quantity of fossil fuels being burned in power stations to provide this energy - surely it is many times more than if the shuttle were to burn fossil fuels itself!
Alex, Cheshire, UK
The real enviromental effect is the energy consumed in the construction of the shuttle and its components. Not only is the production of the materials that go in to making the shuttle hugely energy intensive but the man hours also take a huge toll on the resources of the planet. Each worker drives to work, uses diposible tools and materials and due to the constant quest for safety the number of rejected components must be phenominal. What is the true cost of a shuttle mission?
James , Vancouver, Canada
ALL human activities effect the environment and shuttle launches are no different. One needs to consider the costs vs the benefits. Launch costs are quantifiable. However, benefits may not be realized for years. Look back on the first lunar landings. How could the benefits of micro-electronics, medical technologies, material sciences, computers, and many other spin-offs be quantified? What could be the benefits of our current program? Clean compact power sources, improved waste recycling, new materials, new manufacturing, and improved medical procedures, to name a few, could be used on Earth.
Dennis Craggs, Flint, MI, US
I could see the greenie's point of view if it was plutonium powered, but it's not. Yes, there is undoubtably some damage, but it could be far more harmful.
Alex, Aylesbury, UK
Many of the astronauts have logged thousands of hours in aircraft(s) during training sessions. I am sure none of them were powered by hydrogen.
I think we are forgetting the main picture here. Hypothetically NASA launches one rocket per year, that won't even compare to the pollution of 1 highway truck running continuously for one year. i won't take it as a danger to the environment as long as we have the millions and millions of trucks and cars that pollute our environment everyday.
Jayachandran Kamaraj, Dunlap US
True, that the benefits of the shuttle far outweigh the manageable environmental impact that it may have. But is there any harm in evaluating the alernatives and trying to constantly improve? For e.g. is the method of sending men and material to the space station using the soviet capsule method less resource intensive and simpler? If yes, then may be there should be a rethink.
I wonder how many 'environmentally concerned' folks are reading this on a computer screen in a fabricated workstation, whilst sitting on a plastic chair, having arrived with aid of a car, after dousing themselves in no less than 10 litres of warm water and scoured themselves with all manner of chemical compunds...of course being largely european, we will forgive them the use of the chemical compounds in their toilette.
Matt O'Neill, San Francisco, US
The BBC may edit your comments and not all emails will be published. Your comments may be published on any BBC media worldwide.