Scientists say it is not difficult to realize temperature control in an enclosed structure on ground, but to do so in space is a different thing.
Shenzhou-6, China's second manned spacecraft, boasts a "matured technology in capsule temperature control", according to Fan Hanlin, a senior designer with the heat control sub-system of spaceship system.
"Capsule temperature will be controlled automatically within a range of 17 degrees Celsius to 25 degrees Celsius. Of course, the temperature can also be adjusted manually," Fan said.
In space flight, the sunny side of the Shenzhou-6 has a temperature of 100 degrees Celsius outside the capsule, while its shady side, minus 100 degrees Celsius. To allow human to survive and capsule equipment to work well against the sharp contrast and extreme changes in temperature, an isolation layer is laid on the capsule wall, according to Fan.
The multi-layer isolation material for the spacecraft's orbiter is made of alluminum-coated polyester film, totaling one centimeter in thickness. The film, which cannot isolate temperature on the ground, performs well in vacuum environment, Fan said.
The isolation layer for the spacecraft's re-entry module is made of a sort of ablative material, which not only isolates temperature outside the capsule in space flight, but also, more importantly, burns itself to take away extreme heat produced by vehicle's piercing into aerosphere during its return.
According to Fan, only when sunlight shines into the portholes of the spacecraft will temperature in the isolated capsule be affected a little bit. This may help the quantity of heat produced by working equipment and the two taikonauts, or Chinese term of astronauts, scatter in the capsule. If the heat accumulates gradually, disastrous consequence will likely ensue, Fan said.
In this regard, Fan and his colleagues have developed a kind of liquid circuit technology, which is more or less similar to the condensation approach adopted for car engines. With the technology, liquid is pumped to circulate inside a closed pipeline system. When it flows to a certain set of equipment, it will absorb the heat on the equipment and take the heat it collects eventually to a radiation device fixed outside the capsule, which will radiate the useless heat into space.
As for the heat remaining in the air inside, a condensation drier is arranged, which is similar to air conditioners on the Earth.
All heat control equipment aboard the Shenzhou-6 weighs 300 kilograms in total, Fan said.