Features of Space Environment
The space environment has features which cannot be easily obtained on the ground, such as microgravity, high level of vacuum, excellent visibility, and space radiation. A variety of fields of research and experiments or observations is expected to utilize these features.
- Since there is almost no buoyancy in the space environment, light materials and heavy materials can be mixed uniformly.
- Defect-free crystal structures can be formed because there is almost no weight or depth pressure.
Space provides a large-scale high-level vacuum environment. At the ISS altitude about 400km (250mi), the pressure of the environment is about one 100,000th of 1Pa, which is about 0ne 100 milllionth of the pressure on the ground.
Visibility for observing space is excellent since there is almost no atmosphere and no meteorological effects in space close to the Earth. The whole Earth can be observed from outside of the atmosphere. Abundant, constant, and high-density solar energy is also available.
The space radiation environment is composed of various types of particles. These include a radiation belt consisting of particles captured by the Earth’s magnetic field and surrounding the Earth like a donut; protons with energies ranging from 10 through 1016 Mev; galactic radiation composed of many types of nuclei such as helium, carbon, oxygen, and iron; and high levels of particles generated by solar flares.
Means of Conducting Microgravity Experiments
Space is an ideal place for conducting long-term microgravity experiments while microgravity environment can be obtained on Earth via several means. The means and the comparison are shown in the table below.