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The Forefront of Space Science

Development and Future of Microgravity Experiment System Using a Balloon
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We are now developing a system to conduct microgravity experiments using a balloon. The term “microgravity” denotes literally a world where gravity is almost nonexistent. In that world, there is no “up” or “down” and all things float, without falling. Water mixed with oil will not separate, hence the “relation of water and oil” is not formed. Recently on TV we’ve seen that astronauts float inside the Space Shuttle. It is one example that no gravity world can produce. It is expected that the utilization of a microgravity environment will yield a variety of new scientific knowledge in various fields such as material, life and combustion sciences. To conduct more easily high-quality microgravity experiments, we thought of using a balloon.

This article outlines our microgravity experiment system using a balloon and the secondary effects that will be achieved as the system is developed.

Microgravity experiment methods performed in the past

How and what is to be done to produce a microgravity environment? One of the easiest methods is to “drop an object (i.e., freefall).” Place the object you wish to test under a microgravity environment in a container and then drop the container from a height. No gravity exists in the container. In fact, there are several so-called drop-test facilities using this principle around the world including Japan where containers housing test samples are dropped from the top of a deep hole for example. While this method provides a pure microgravity environment, its weakness is that the environment lasts only for a few seconds. To test for a longer time, we need an unrealistically deep hole (or high tower). To create a microgravity condition lasting for 20 seconds, a 2km-deep hole is required.

One other method for the experiment is to use “an aircraft flying in a ballistic trajectory.” With this method, a microgravity environment lasting for tens of seconds can be obtained. Strictly speaking, however, some gravity remains with the aircraft method and thus it is not appropriate for some studies such as the creation of perfectly even-mixed materials.

By using space vehicles such as the Space Shuttle, we can obtain a good microgravity condition lasting several days. While this method is very attractive in terms of technology, it is naturally very expensive and time consuming.

In the circumstances, we looked for a method that could easily create and maintain a good microgravity environment for over tens of seconds. As a result, we came up with the idea to use a balloon. Headed by principal investigator Tatsuaki Hashimoto, professor of ISAS, we are proceeding with the development of the experimental system. The first trial vehicle has already been completed and is ready for launch by balloon.

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