Uzay İstasyonu’nda ‘sanayi evrimi’
Scientists are planning to use the space station to grow a new kind of crystal for use in solar cells by 2013.
They say the vacuum conditions in space improve the quality of thin film crystals, giving them properties that are unachievable on Earth.
The technique, called Molecular Beam Epitaxy, could improve electronics, in particular raising the efficiency of solar cells as much as 60%.
Scientists behind the proposed move call it “an industrial evolution”.
Dünya şartlarında üretimi neredeyse imkansız olan kristal türü eğer UUİ’de büyük müktarlarda üretilebilirse, enerji ihtiyacının karşılanmasında güneş enerjisini birinci sıraya yükseltebilir. Rus ve ABD’nin ortak projesinin 2013 yılında başlatılması planlanıyor.
Moleküler Işın Epitaksisi adı verilen teknikle üretilen kristalin uzaydaki havasız ortamda kazanacağı özelliklere dünyada erişmek imkansız. Houston Üniversitesi’nden Prof. Alex Ignatiev’in verdiği bilgiye göre uzayın havasız ortamında bambaşka özellikler kazanacak olan kristalden mamul ultra-ince yarı-iletken materyal, bilgisayar, güneş hücreleri, yüksek hızlı transistörler ve iletişimde büyük bir ilerlemeyi tetikleyecek.
Prof. Ignatiev, bu materyalin UUİ’nin dışında kurulacak bir ‘üretim uydusu’nda üretilebileceğini söylüyor. Uydu UUİ’ye monteli olabileceği gibi, arada istasyona uğrayan bağımsız bir uydu şeklinde de konuşlandırılabilir.
Moleküler ışın epitaksi yöntemiyle üretilen bir güneş hücresi
Rusya Federal Uzay Ajansı Roscosmos’un finansmanı ve Rus ve ABD’li bilimcilerin katılımıyla hazırlanan proje kapsamında, ilk insansız ‘deneme üretim uydusu’, 2013 yılında UUİ’ye gönderilecek. Roscosmos, proje için NASA’nın da mali desteği için bastırıyor.
Moleküler Işın Epitaksisi tekniği daha önceki Uzay Mekiği uçuşları sırasında uzay ortamında denenmiş ve olumlu sonuçlar alınmıştı.
Her şey yolunda giderse, bu kristalle üretilen yeni devre ve enerji panelleri 10 yıl içinde sanayide kullanılmaya başlayacak.
“The unique vacuum environment of space allows us to move forward in terms of computers, solar cells, high speed transistors, high power transistors, energy – all these areas would benefit from advancing materials in space,” Professor Alex Ignatiev from the University of Houston in Texas told BBC News.
The scientist explained that the space-grown extremely pure artificial crystals, known as ultra-thin semiconductor films, would be produced in a space vacuum lab, spinning above Earth.
The lab will either be attached to the International Space Station (ISS) or carried by a small unmanned spacecraft that will periodically dock to the ISS.
The semiconductor films would consist of atomic layers formed from different elements, placed on top of one another. Every layer would be a different element, to ultimately form a very thin film of an extremely complex composition.
The new project is mainly funded by the Russian federal space agency Roscosmos, with both Russian and US scientists involved.
It has already been partially approved, but still needs to be given a final go-ahead in the coming months.
The launch of the mechanism into orbit, if it is given the go-ahead, is scheduled for 2013.
Without sufficient funding, the endeavour might have to be frozen.
But in light of the recent push by the Russian government to step up the efforts with space exploration, many believe the project is likely to go ahead.
“If we’re able to make it work in the next decade, it will be a huge deal for Russia’s prestige,” said Alexandre Ivanov, head of the department of preparation of science programmes at the Roskosmos Research Institute for Machine-Building, TSNIIMASH.
“And it will also be an incentive for other countries to do the same.”
Dr Ivanov said that it would be possible to produce such artificial crystals on Earth, but they would be a lot less pure.
“These structures don’t exist in nature, they’re completely man-made. If produced in space, they will be of a much higher quality than on Earth, and that means that we will get new properties in materials that will allow us to develop new technologies to improve our quality of life.”
Krikalev, Pchelyakov and Ignatiev Cosmonaut Krikalev conducted the first experiments with thin film space crystals on board US shuttles
“Something completely new will appear that will have an even greater impact than when mobile phones came onto the market,” he stressed.
From shuttle to ISS
Besides Russia and the US, Kazakhstan is also involved in the project, and several other nations have expressed an interest.
But the main people working on developing the mechanism are Professor Ignatiev and scientists from Siberia.
“Our main goal with Alex Ignatiev is to research the methods of producing nanomaterials that are highly effective in turning sunlight into electrical light,” said Professor Oleg Pchelyakov from the Institute of Semiconductor Physics in Novosibirsk.
“So the priority now is the solar cells. But such a space-based vacuum lab could also be useful for other things – for any such technological processes where the cleanness of the product is of vital importance.”
Space crystals mechanism The mechanism is ready to be launched into orbit
Professor Ignatiev came up with applying the Molecular Beam Epitaxy technique in the vacuum of space years ago. The recent technology has been based on his earlier experiments aboard the US space shuttles in the 1990s.
He managed to conduct three successful tests of thin film growth in space before the ill-fated shuttle Columbia exploded in 2003.
The US scientist collaborated with Nasa to launch a specially designed vacuum laboratory called the Wave Shield facility.
Even though the lab was flying in space, the vacuum there was not “ultra-high” because of contamination from the shuttle. To achieve the perfect condition of “emptiness”, scientists came up with the idea of using a huge circular shield to disperse atoms behind the mechanism and create an ultra-high vacuum in the cone-shaped space there – impossible to achieve on Earth.
The same thing will happen when the new vacuum lab docks to the ISS – the new shield will be deployed behind the lab, and within the protected space, the thin film crystals will be grown.
Russian cosmonaut Sergey Krikalev carried out the very first experiment with thin films on the Wake Shield Facility aboard the shuttle Discovery in 1994.
Mr Krikalev shot to fame as the “last citizen of the USSR”: in 1991-1992 he spent 311 days, 20 hours and 1 minute aboard the Mir space station as the Soviet Union collapsed.
‘Not good enough’
Despite successfully producing revolutionary artificial crystals during the three shuttle flights, for Professor Ignatiev they were just not good enough.
“We had an ultra-vacuum when we flew on with the space shuttles, but only for a short period of time, only for a couple of days,” he explained.
“It takes a while for the vacuum to essentially stabilise. When we launched the shuttle, it was dirty, it contaminated the environment around it.
Thin film An atomic microscope scan of a thin film grown during the Wake Shield experiments
“So we’re hoping that at the space station we’ll have a longer time available to get a better vacuum environment and then start looking at different material possibilities, especially in the solar cells energy area,” he added.
Professor Ignatiev said the thin film crystals that were produced back then were mostly research films to try to understand how the ultra-vacuum of space improved quality of materials.
Now, if the new vacuum lab joins the ISS, the goal will be quite different and a lot more practical – how to apply the results of the research to everyday life, and in particular, to produce solar cells for use in space and on Earth.
“We’ll be looking at a large number of different elements and the beauty of this technique is that I can take different atomic species and combine them together to make unique atomic structures that have specific performance,” said the researcher.
Professor Pchelyakov said that compared with space, within our planet’s atmosphere conditions were far from ideal.
“A vacuum lab on Earth sort of ‘remembers’ what chemicals you were working with last time and it can’t ever be as clean as in the beginning. But in space, you can use all the periodic table if you wish,” he said.
“Also in space, once the molecules are out of the way, they won’t ever come back. On Earth it’s different – vacuum volume is limited, vacuum chambers are usually quite small, there are walls. It’s impossible to produce absolutely clean materials here.”
If the project is a success, the scientists say their long-term goal is to fabricate solar cells on the Moon by means of power plants set up directly on the lunar surface that would generate electricity from solar energy.
“It sounds like science fiction now, but one day, it may well become a reality,” said Dr Ivanov.