If you're going on a space walk, you need to be shielded from cosmic rays, temperature, and possibly other issues.

What components of cosmic rays are dangerous? What sort of protection is used to shield from these as well as from the temperature issues?

  • $\begingroup$ ...scheduling. Keeping EVAs away from South Atlantic Anomaly and solar flares/CMEs... $\endgroup$ Jul 22, 2013 at 20:17

2 Answers 2


A newspaper article from september 1995 says that even when the astronauts tried to get cold, by staying in the shadow of the shuttle out in the vacuum of space they were still warm and comfortable.

But to NASA's delight, Endeavour's two spacewalking astronauts kept warm Saturday thanks to new heated gloves, thermal socks, boot liners and toasty long underwear.

In this scenario the spacewalk lasted at least an hour at temperatures as cold as -120 or -130 degrees Fahrenheit.

This kept them warm even though

the spacewalkers remained motionless on the robot arm in an attempt to get cold

Though this apparently had no effect as at one point one of the spacewalkers

had to turn off the fingertip heaters in his gloves

This information is probably quite old as this occurred about 18-19 years ago and technology is likely to have advanced. Though i imagine the basics would be the same as it appears relatively simplistic to maintain heat.

On the front of protection from radiation on spacewalks it seems like, other than the suit, there is none!

This website talks about the plans for the EVARM badges to be attached to various parts of the space suit to allow measurement of exposure to radiation to see if any further protection is needed.

Actually, I told a small lie, there is one other form of protection that they get from radiation other than the space suit. Timing. Much like launches, NASA make sure to monitor the sun for solar flares and generally make sure there is no astronauts about when one is going off. Making sure to only send them out into space when radiation is at its lowest provides one of the highest forms of protection at this time.

Coming from a hopefully more recent, though perhaps not entirely reliable, source we have this HowStuffWorks article on spacesuits.

There is a section on temperature control which talks about how they layer the fabrics of the space suit to ensure as much heat is kept in as possibble. It also bring up the interesting point of heat removal, heat builds up seemingly easily and if not released on occassion then the astronaut risks dehydration and a foggy visor from perspiration.

Cooling systems range from fans which blow air to water cooled systems to remove heat.

That same article also gives us a little more insight onto how they are protected from radiation. It shows that the spacesuit is reflective to purposefully reduce the amount of radiation. It concurs with my previous point about spacewalks being planned to avoid solar flares. Being caught in a solar flare in just a space suit would be about as effective as trying to walk on the sun wearing tin foil and leaves.


Modern Orion Suit ISS

EVA suits need to meet the following requirements:

  • A stable internal pressure. This can be less than earth's atmosphere, as there is usually no need for the space suit to carry nitrogen (which comprises about 78% of earth's atmosphere and is not used by the body). Lower pressure allows for greater mobility, but requires the suit occupant to breathe pure oxygen for a time before going into this lower pressure, to avoid decompression sickness.

  • Mobility. Movement is typically opposed by the pressure of the suit; mobility is achieved by careful joint design. See the Theories of space suit design section.

  • Supply of breathable oxygen and elimination of carbon dioxide; these gases are exchanged with the spacecraft or a Primary Life Support System (PLSS)

  • Temperature regulation. Unlike on Earth, where heat can be transferred by convection to the atmosphere, in space, heat can be lost only by thermal radiation or by conduction to objects in physical contact with the exterior of the suit. Since the temperature on the outside of the suit varies greatly between sunlight and shadow, the suit is heavily insulated, and air temperature is maintained at a comfortable level.

  • A communication system, with external electrical connection to the spacecraft or PLSS

  • Means of collecting and containing solid and liquid bodily waste (such as a Maximum Absorbency Garment)

  • Advanced suits better regulate the astronaut's temperature with a Liquid Cooling and Ventilation Garment (LCVG) in contact with the astronaut's skin, from which the heat is dumped into space through an external radiator in the PLSS.

  • Shielding against ultraviolet radiation

  • Limited shielding against particle radiation

  • Means to maneuver, dock, release, and/or tether onto a spacecraft

  • Protection against small micrometeoroids, some traveling at up to 27,000 kilometers per hour, provided by a puncture-resistant Thermal Micrometeoroid Garment, which is the outermost layer of the suit. Experience has shown the greatest chance of exposure occurs near the gravitational field of a moon or planet, so these were first employed on the Apollo lunar EVA suits.

To your question specifically:

What components of cosmic rays are dangerous? What sort of protection is used to shield from these as well as from the temperature issues?

Radiation: High energy particles destroy organic matter at a fundamental level, breaking DNA chains and killing tissue. Exposure greatly increases the risk that during the lifetime of the exposed person will develop some form of cancer. To reduce exposure they sometimes position the craft to use it as additional shielding against exposure.

Despite considerable efforts, the cancer and the toxicity risks remain to be quantified: 1) the nature and the frequency of secondary heavy ions need to be better characterized in order to estimate their contribution to the dose and to the final biological response; 2) the diversity of radiation history of each astronaut and the impact of individual susceptibility make very difficult any epidemiological analysis for estimating hazards specifically due to space radiation exposure. 3) Cytogenetic data undoubtedly revealed that space radiation exposure produce significant damage in cells. However, our knowledge of the basic mechanisms specific to low-dose, to repeated doses and to adaptive response is still poor. The application of new radiobiological techniques, like immunofluorescence, and the use of human tissue models different from blood, like skin fibroblasts, may help in clarifying all the above items. (http://www.ncbi.nlm.nih.gov/pubmed/21436608)

A number of parameters affect astronaut exposure to radiation. These parameters include the structure of the spacecraft, the materials used to construct the vehicle, the altitude and inclination of the spacecraft, the status of outer zone electron belts, the interplanetary proton flux, geomagnetic field conditions, solar cycle position, and EVA start time and duration.

A NASA Study found:

The results from EVARM have shown that EVA doses are elevated from those inside the ISS, but not significantly. In addition, this time period recorded doses during a time of increased geomagnetic activity (October/November 2002). It was determined that during this event doses to EVA participants were increased due to elevated levels of electrons in Earth orbit. These electrons are easily shielded by spacecraft materials and thus not measured inside the ISS. Fortunately, proper positioning of the spacecraft can dramatically reduce the radiation field encountered during EVA missions.

Temperature: Requirement for protection here is pretty self-explanatory. Suit for ISS - Low Earth Orbit (LEO), typically cover -250°F to +250°F for human protection. This is accomplished by the Liquid Cooling and Ventilation system.



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