Analog and simulated microgravity platforms for life sciences research: Their individual capacities, benefits and limitations

Gravity is always present on Earth. However, the influence of gravity can be modified or compensated. Generally, the products created under microgravity have important properties that usually surpasses the best terrestrial counterparts. Commercially, these products have striking features that aids marketing. Fast responding microgravity platforms can be used for short-term experiments, where the reactions or observations takes less time. This can be provided in drop towers, parabolic flights and sounding rockets. To study long-term effects of microgravity, human tended space laboratories have been used, such as the International Space Station. Scientists have developed various kinds of ground-based facilities and equipment for some of them to achieve the condition of functional weightlessness as a result of limited access to space laboratories. Slow responding microgravity platforms can be used for long-term experiments, where the reactions or observations takes more time. Microgravity analog, model or simulations are slow responding platforms and are able to provide long-term effects of microgravity. This includes long-duration bedrests, water immersions and in magnetic levitation, clinostats, random positioning machines, rotating wall vessels and even centrifuges. This study compares and gives an overview of currently known real, analog, model or simulated microgravity environments and platforms, and demonstrates their individual capacities, benefits and limitations.