Space

Plastic phantom shows space travel may be safer than thought

Plastic phantom shows space tr...
Interior structure of the phantom used in the experiment Matroshka (Photo: DLR)
Interior structure of the phantom used in the experiment Matroshka (Photo: DLR)
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Interior structure of the phantom used in the experiment Matroshka (Photo: DLR)
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Interior structure of the phantom used in the experiment Matroshka (Photo: DLR)
The Matroshka phantom with astronauts S. Krikaliew and J. Philips on board of the International Space Station (Photo: NASA)
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The Matroshka phantom with astronauts S. Krikaliew and J. Philips on board of the International Space Station (Photo: NASA)
Matroshka covered by a container simulating a spacesuit (Photo: DLR)
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Matroshka covered by a container simulating a spacesuit (Photo: DLR)
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A European Space Agency (ESA) experiment aboard the International Space Station (ISS) suggests that space travelers may have less to worry about when it comes to radiation ... thanks to a phantom. Called the Matroshka, the "phantom" is a plastic mannequin that is the key component of the first comprehensive study of the effects of radiation on astronauts on long-term space missions that indicates that the hazard may not be as severe as previously thought.

Of all the perils of space travel, the most pervasive as it is intangible is radiation. Each day that an astronaut spends outside the protective confines of the Earth's atmosphere brings an increased chance of cancer and other conditions. According to ESA, a person on the ground soaks up about 2.5 mSv/year, while an astronaut on the space station can receive up to 1 mSv/day. This is the reason the European Astronaut Corps limits its members to 500 mSv/year and 1Sv for an entire career. (Sv or sievert is a unit used to measure of the health effect of small amounts of radiation on the body).

Surprisingly, despite this awareness, very little is actually known about exactly how much and what kind of radiation an astronaut is actually exposed to. It's to fill this gap that the Matroshka was sent to the ISS. Named after the famous Russian nesting dolls, it was built and operated by ESA in cooperation with Roscosmos and various European institutions, and was flown to the station in 2004. Its purpose was to measure the type and amount of radiation astronauts are exposed to both inside and outside the space station over a period of several years.

Matroshka covered by a container simulating a spacesuit (Photo: DLR)
Matroshka covered by a container simulating a spacesuit (Photo: DLR)

The Matroshka is technically a phantom. That is, a radiological doll designed as a stand-in for a human being while testing radiation equipment or, in this case, space radiation. It consists of a head and torso made of 33 horizontal cross sections of plastic, each measuring 2.5 cm (1 in) thick. Layers are used, so the mannequin can be assembled around a central dowel, which makes it easy to install and remove sensors. Each layer is made of a special plastic that simulates the soft tissues of the body with different densities standing in for the muscles, liver, spleen, lungs, and so forth. In addition, there are pieces of real human bone inserted into the cross sections to provide the proper radiological properties and a battery of sensors.

Space radiation is composed mainly of cosmic rays made up of protons and other heavy ions instead of the more common gamma rays found in terrestrial radiation sources. Since there are many different kinds of radiation, a number of different active and passive sensors are needed to detect them. The Matroshka includes about a dozen different sensors, including detectors for recording pressure and temperature.

Among the sensors are six thousand passive thermoluminescent detectors – many of which were made by the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Kraków, Poland. They are constructed of doped lithium fluoride placed in plastic tubes set in a 3D lattice. The dopants upset the detector's crystalline structure, which sets up "forbidden" energy levels that capture electrons generated by cosmic rays. When the tubes are returned to Earth and heated in a laboratory, they release light in proportion to the amount of radiation they've absorbed.

The Matroshka phantom with astronauts S. Krikaliew and J. Philips on board of the International Space Station (Photo: NASA)
The Matroshka phantom with astronauts S. Krikaliew and J. Philips on board of the International Space Station (Photo: NASA)

Over the Matroshka is a not very fashionable jacket, which isn't just there for looks. It also acts as a mounting for cables and additional detectors. The latter need to be placed on the outside of the mannequin in order to measure incoming radiation and skin exposure, and to simulate the dosimeters carried by all space station personnel.

From 2004 to 2009, the Matroshka sat inside one of the Russian modules on the ISS, but radiation hazards outside the station are many times greater than inside, so the phantom made a spacewalk for the first such exposure measurements ever made. Like a human astronaut, the Matroshka was clad in a spacesuit – or, at least, a simulated one made of layers of carbon fiber and plastic and filled with dry oxygen gas.

According to IFJ PAN, the Matroshka measurements indicate that exposure estimates for inside the station were 15 percent too high, while those outside the station were off by 200 percent. This indicates that travel to the Moon and perhaps Mars may be safer than previously thought. However, the team emphasizes that the ISS sits in a very protected orbit.

“We must remember that measurements within the Matroshka experiment were performed at low Earth orbit where the Earth’s magnetosphere significantly reduces the number of charged particles from cosmic radiation. In interplanetary space there is no such shielding,” says Dr. Pawel Bilski of IFJ PAN.

Source: Institute of Nuclear Physics PAN

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11 comments
Darin Selby
This article is B.S. because they haven't even left earth's orbit with the test. Last sentence: "In interplanetary space there is no such protective magnetosphere shielding,”
VirtualGathis
If this thing is riding on the ISS it is of marginal value for analyzing radiation exposure in "space" The ISS is in LEO very close to the atmosphere. That is inside both of the Van Allen belts which deflect charged particles and radiation.
Put it in a system at the L2 or Lunar Orbit and I think it would give a better understanding of how much radiation deep space astronauts will endure. As it is it is kind of like trying to get an idea of how much radiation exposure a body would absorb inside a nuclear reactor by measuring exposure in a lead lined bunker next door.
William Johnson
So when will they send this on a trip around the moon or at least far enough out in space to eliminate Earth's protection?
justme70
"...space travel may be safer than thought"
Well then, we'd better stop thinking and start space travelling!
Bob Komarek
An interesting posit: When man finally has the technology to establish an off world colony on a permanent basis....those inhabitants according to the law of natural selection, will have to adapt to a different set of environmental variables. A new species entirely may develop.
Don Duncan
The magnetosphere is our main protection against radiation. Any test done within that protected region is useless. It says nothing about space.
Reason
Radiation levels have been measured outside of LEO and are not deemed to be 'showstoppers' for say ... a return trip to Mars;
http://www.npr.org/blogs/health/2013/05/30/187164731/Headed-To-Mars-Watch-Out-For-Cosmic-Rays
Jessie Janson
they should have gotten this on nasas test of their capsule, it went out farther then the ISS. im sure nasa would have done it for free if they shared the data.
Jesse Jenkins
What effect does the sun's magnetosphere have on interplanetary radiation exposure, if any? It's much stronger than earth's magnetosphere, albeit we are inside of it. does it only effect interstellar radiation? I wonder if the radiation is less intense between planets since planetary gravity tends to attract massive particles.
Slowburn
ISS passes through the South Atlantic Anomaly of the Van Allen belt.