What are the non-orbiting microgravity facilities?

The non-orbiting microgravity platforms grant experimental samples access to true (real) microgravity. This microgravity is not mimicked (simulated). These platforms include:

·      Drop towers

·      Suborbital Rocket (Sounding Rocket)

·      Parabolic Flight in Specialized Airplane

·      Balloon 

Drop-towers are vertical structures that allow free-fall of payloads under vacuum to generate microgravity conditions. The accessibility is moderate. The time of the free-fall is determined by the height of the tower, which can get up to several meters. Drop tower supply gravity force (g) of 10^-2 to 10^-6; the supply of microgravity can only range from 2 to 10 seconds; possible experiments are on cells, microbes, gravitropic reactions in fungi, and for other electrophysiological studies; the limitation is that the duration of study is very short (Figure 1).

Figure 1: Drop-tower, Bremen, Germany. Source: https://en.wikipedia.org/wiki/Drop_tower

 

Suborbital or sounding rockets are rockets launched on ballistic trajectory in vacuum with a free-fall at a high altitude. The accessibility is moderate. Sounding rockets can achieve up to a height of about 145 km; have possible gravity force (g) of 10^-3 to 10^-4; the supply of microgravity ranges from 10 to 20 minutes; possible experiments can be on membrane transport, cell morphology and physiology, free-flow electrophoresis, gene expression, signal transduction pathways, and other experiments in biotechnology; the limitations are the associated costs and how to recover the modules of experiment from the remote sites (Figure 2).

Figure 2: Sounding Rocket. Source: https://en.wikipedia.org/wiki/Sounding_rocket

 

Parabolic flight in specialized airplane is another platform aimed to attain free-fall conditions in an aircraft in a ballistic trajectory of a parabola. The accessibility is moderate. The parabolic flight maneuvers to get to an altitude of at least 3 km. Parabolic flight supplies gravity force (g) of 10^-2 to 10^-3; supplies microgravity for about 20 to 30 seconds in a cyclic manner; possible experiments had been signal transduction in human immune cells and osteoblasts, neuron responses in experimental animals and protein crystallization; the limitation is that hypergravity acceleration interrupts the microgravity phase (Figure 3).

Figure 3: Parabolic flight in Specialized Airplane. Source: https://en.wikipedia.org/wiki/Reduced-gravity_aircraft

 

Latex high-altitude balloons used for meteorological measurements allow for a simple and moderate cost approach to achieving microgravity conditions. An example is the use of a capsule carried aloft in helium weather balloon. An altitude of more than 25 km can be achieved and then the capsule carrying the experiment will be separated from the balloon for free-falls towards the Earth. This free-fall grants access to the microgravity conditions that is required for the experiment payload. On-board are: sensors to measure the capsule’s acceleration, cameras, and sub-transmitters. These experimental balloons can supply gravity force (g) of up to ±10^-4; can provide microgravity for 30 to 60 seconds. Parachute recovery system must be deployed to safely recover the capsule and the experimental data. Possible experiment was observing behaviors and brain activities of fishes; and the limitation is that only a small mass of payload could be accommodated, and launching of helium weather balloons necessitates detailed checks over the local weather, environmental conditions, wild-life and aviation regulations (Figure 4).

Figure 4: Microgravity Experimental Balloon. Source: https://en.wikipedia.org/wiki/Hot_air_balloon

 

The benefits of the access to the non-orbital microgravity platforms cannot be overemphasized over the socioeconomic benefits granted via the experiments.

 

Further reading

Oluwafemi, F.A., Neduncheran, A., 2022. Analog and simulated microgravity platforms for life sciences research: Their individual capacities, benefits and limitations. Advances in Space Research. https://doi.org/10.1016/j.asr.2022.01.007.

 

Oluwafemi, F.A., Neduncheran, A., 2021. Real and simulated microgravity platforms: Their individual capacities, benefits and limitations. 71^st International Astronautical Congress (IAC) – The CyberSpace Edition, 12-14 October, 2020. IAC-20-A2,5,10,x56924.