rather than an overfilled balloon. Consciousness is retained for up to 15 seconds as the effects of oxygen starvation set in. No snap freeze effect occurs because all heat must be lost through thermal radiation or the evaporation of liquids, and the blood does not boil because it remains pressurized within the body. In space, there are many different highly energized subatomic protons that will expose the body to extreme radiation. Although these compounds are minimal in amount, their high energy is liable to disrupt essential physical and chemical processes in the body, such as altering DNA or causing cancers. Exposure to radiation can create problems via two methods: the particles can react with water in the human body to produce free radicals that break DNA molecules apart, or by directly breaking the DNA molecules. Temperature in space can vary extremely depending on where the Sun is. Temperatures from solar radiation can reach up to and lower down to . Because of this, space suits must provide proper insulation and cooling. The vacuum in space creates zero pressure, causing the gases and processes in the body to expand. In order to prevent chemical processes in the body from overreacting, it is necessary to develop a suit that counteracts against the pressure in space. The greatest danger is in attempting to hold one's breath before exposure, as the subsequent explosive decompression can damage the lungs. These effects have been confirmed through various accidents (including in very-high-altitude conditions, outer space and training vacuum chambers). Human skin does not need to be protected from vacuum and is gas-tight by itself. Instead, it only needs to be mechanically compressed to retain its normal shape. This can be accomplished with a tight-fitting elastic body suit and a helmet for containing breathing gases, known as a space activity suit (SAS). Design concepts A space suit should allow its user natural unencumbered movement. Nearly all designs try to maintain a constant volume no matter what movements the wearer makes. This is because mechanical work is needed to change the volume of a constant pressure system. If flexing a joint reduces the volume of the space suit, then the astronaut must do extra work every time they bend that joint, and they have to maintain a force to keep the joint bent. Even if this force is very small, it can be seriously fatiguing to constantly fight against