Padraig Moloney went straight to Nasa's space centre in Texas after studying nanotechnology at MIT, writes Dick Ahlstrom
The only foreign scientist employed at Nasa's Johnson Space Centre in Texas is an Irishman. He talked his way out of doing a degree in music in favour of a career in aerospace research.
Not yet 30, Padraig Moloney specialises in studying nanotubes, microscopic straw-shaped tubes made from carbon atoms. "I head the applications research part of it," he says.
Carbon nanotubes are most remarkable structures that are almost unimaginably small. He currently "handles" nanotubes measuring from one to four billionths of a metre (one to four nanometres) in diameter and about a millionth of a metre long.
They might seem impossibly small to be good for anything but Moloney and his team are busy finding lots of ways to use them, from scrubbing carbon dioxide from the air inside a spacecraft to delivering cancer-killing drugs to the site of a tumour. This seems a far cry from the career goals sought for him by his parents.
"My family wanted me to do music college but I had other ideas," he says.
The Dubliner had hoped to do aerospace science and after finishing secondary school at St Mary's College Rathmines he got in touch with the US embassy here to help find a university where he could pursue his dreams.
He applied for and got accepted at the Massachusetts Institute of Technology in Boston and did his undergraduate studies there. He has remained in the US since.
"I ended up staying because of the research and the subject I wanted to study, nanomaterials. Our primary material is single wall carbon nanotubes," he says. "It is the strongest material we will ever make."
The tubes are 40 to 60 times stronger than pure steel. Some are conducting and others are semiconducting.
Producing long carbon nanotubes is a challenge, but they hold huge promise. Conducting nanotubes are 100 times more conductive than copper or aluminium and a nanotube wire would be able to carry electricity across thousands of miles with almost no power loss. If twisted together they would produce a super-strong rope, something that could be used to deliver the often discussed "elevator" into space. This idea involves a cable tethered to a geostationary weight placed in orbit, used as a way to lift objects into space.
"Carbon nanotubes are the only material that could theoretically allow that to happen," says Moloney.
Much remains to be done before we can visit space using a 150km sightseeing lift, however.
"There are issues with purifying them," he admits, and it is also difficult to characterise and handle something that is so very small.
Nanotubes are produced using a "laser ablation process". A carbon target is seeded with metal catalysts and then hit with a hot laser that vaporises the carbon. The carbon then reforms into tubes over the catalysts, Moloney says. The goal is to produce single wall nanotubes rather than multiple wall tubes which look like one straw set inside another.
"The single walls are much, much better at being defect-free. They are near perfect," says Moloney.
Two or three years ago big labs could only produce specks of nanotubes, with a gram costing $1,000. Now specialist companies can make 10kg to 15kg of nanotubes a day, costing less than $100 a gram.
One application of interest to Moloney and his team is air-scrubbing or "revitalisation" inside a spacecraft.
"We have a sealed environment on a spacecraft," he says. "Air revitalisation is very important."
Revitalisation systems on the space shuttles are reliable for the short duration flights these craft undertake but "that won't work if we want to do longer distances to the Moon or Mars".
Moloney is working on a renewable system for scrubbing out carbon dioxide, using nanotubes. Existing scrubbers use polymer structures seeded with amine, a chemical that captures carbon dioxide. Nanotubes would do a better job because they could hold much more amine to extract more carbon dioxide.
"Nanotubes offer a higher surface area," he says. "There are well over 100 square metres of surface in a gram of material. I can use those square metres and coat them with amine."
The waste gas is then easily removed from the scrubber either by vacuuming it off or heating it to release the carbon dioxide.
Nanotubes look promising for making composite materials, such as carbon fibre reinforced plastics, even stronger, for very powerful capacitors and in fuel cells to deliver more power density and reliability, says Moloney.
Another novel use is in cancer treatment. Many anti-cancer drugs are hydrophobic and can't easily reach the tumour site. These drugs could be encapsulated in nanotubes or their spherical analogue, fullerenes, and delivered directly to a tumour by piggybacking them on antibodies.