A likelife dummy is being used to measure how well humans might survive space radiation on a long journey to Mars, writes Dick Ahlstrom
A "human" dummy has been hired to help make space travel safer. Named Matroschka, scientists hope it will enable them to reduce space radiation hazards on a manned trip to Mars.
The research team includes a Dublin-based scientist, emeritus professor Denis O'Sullivan, of the Dublin Institute for Advanced Studies. O'Sullivan is a noted world expert in the field of upper atmosphere and space-based radiation exposure caused by cosmic rays.
He headed a major EU study on aircraft flight-crew exposures to cosmic rays, producing a report that showed flight crew received doses akin to nuclear plant workers and uranium miners.
"I have been working in this area of cosmic rays for some time," says O'Sullivan. He developed a sensor that can detect incoming cosmic rays and solar particles in all their variety, from electrons and protons to neutrons and heavier galactic cosmic rays.
"It is a detector we have been developing for some time," he says. "It measures the radiation one gets from all the particles you encounter in space."
We ignore cosmic rays on earth because our exposures are low given the protection afforded by the atmosphere. Exposures are higher for those on transatlantic flights and higher still for the space travellers who venture up in the shuttle and the space station.
"The damage cosmic rays can do to human organs is quite extensive," says O'Sullivan. "Cosmic rays come in at very high energies."
They do damage to cells on their own, but also kick off a cascade of particles in anything they hit, spreading out to increase the damage done.
"Our knowledge on this matter is still fairly basic," O'Sullivan says of the cascade effects. "It is going to be very important from the point of view of long-duration space flights."
Cosmic rays can vary in their molecular weights, but they travel on average at about 90 per cent of the speed of light. Even something as light as an electron packs a lot of punch when travelling at that speed.
Their energies are measured in electron volts and the typical cosmic ray will have an energy level of about one billion electron volts.
O'Sullivan's detectors have flown on many shuttle flights, including the three immediately preceding the tragic loss of the shuttle Columbia in February 2003. A detector package was due to fly on the "return to flight" launch of STS-114, which was expected to fly this month. NASA announced in late April, however, that STS-114 would not now fly until July 15th.
The Matroschka project is a European/Russian collaboration. The dummy has been flying tethered outside the International Space Station since February 2004. Scientists hope to bring Matroschka back to earth this September or October, O'Sullivan says.
Matroschka is a mannequin fitted with an array of radiation detectors.
"It has been constructed from natural bone and material that simulates human flesh," O'Sullivan says. "The detectors are placed at the locations of critical organs." These include the kidneys, heart, eyes, colon and other sensitive tissues.
Matroschka has been on a "space walk" over the past months in an effort to understand the exposures to astronauts doing Evas (extra vehicular activity) outside the space station. The advantage of the mannequin is that the detectors are recording exposure information at "tissue" depths that match those from an actual human.
"We are planning to send another one up to do measurements in the space station's living quarters," says O'Sullivan.
The scientist is officially past retirement age but he is as busy as ever. His departure from the institute was delayed for 18 months so that he could finish his aircraft flight-crew research. He is now involved in a collection of international collaborations aimed at measuring cosmic-ray exposures.