2. Space food, like ordinary food on the ground, provides energy and nutrition for human body. However, in order to save the space of the spacecraft and the payload when launching, the space food carried by astronauts should be as light and compact as possible. For example, nutritious dry biscuits and sausages can be soaked in water when eating to restore the taste similar to fresh food. In addition to being able to withstand the impact of special space environment factors, such as impact, vibration and acceleration, space food must also make appropriate adjustments to dietary nutrients according to the indicators of astronauts' physiological changes under weightlessness. For example, muscle atrophy requires that food must provide sufficient high-quality protein; Bone loss requires food to provide sufficient calcium, appropriate calcium-phosphorus ratio and vitamins.