Space scientists dealing with life sciences and physical sciences use various platforms to carry out their experiments; although each platform allows them to do their work under microgravity conditions, it also has specific characteristics and advantages.
The ISS serves as an Earth observation platform and as a laboratory for life sciences and materials science. The station environment accommodates a large number of long-term experiments in microgravity. Use of the ISS considerably improves the quality of space research results because it allows experiments to be repeated, so that the results obtained can be compared.
The space shuttles have often been used by Canada to conduct various experiments. Their main role is in the assembly of the International Space Station, until it is completed. Since Marc Garneau's first flight in 1984, a number of Canadian experiments and astronauts have flown aboard the shuttles. The shuttles can remain in orbit for more than two weeks and accommodate large experiment modules as well as complex experiments.
Parabolic flights are a less costly alternative to space flights. A parabolic flight by an aircraft can generate conditions similar to zero gravity. These flights are readily accessible to space science researchers for situations such as preliminary studies in zero gravity.
To replicate zero gravity conditions, a specially modified commercial jet is used. The aircraft climbs into a steep arc trajectory in the sky, then descends. During the upward arc of the parabola, the thrust of the motors is controlled. The craft is in freefall when it reaches the top of the parabola and during part of the downward arc. This freefall creates the zero gravity conditions (15 to 20 seconds) that can be used to perform experiments.
The Flight Research Laboratory of the National Research Council of Canada (NRC) undertook a parabolic flight program in 1991. In Canada, researchers mainly use a Falcon 20 airplane belonging to NRC.
Sounding rockets make it possible to obtain longer-lasting, higher-quality microgravity conditions than with aircraft. Only 100 km up, the air is 10 million times less dense than at the Earth's surface and air resistance is considerably weaker. When the motors cut out, the rocket goes into free fall, and zero gravity conditions are present for between 6 and 15 minutes.
A drop tower consists of a tall empty column. Experimental equipment that is dropped from the top of the tower is in zero gravity just for a few seconds (between 2.2 and 10 seconds). Though they afford a shorter period of microgravity than can be produced by airplanes in parabolic flight, the towers have the advantage of providing more stable conditions.