Table of Contents

A Guide to Microgravity for All Ages

Canada's Microgravity Environments

The terms weightlessness and microgravity are used interchangeably. The prefix "micro" means very small in Latin. Scientifically it means one millionth or 10^-6. Microgravity means an environment where the effects of gravity are very small. Note that it does not mean an environment where gravity is very small. There are several facilities the scientific community uses to obtain microgravity environments:

Parabolic Flight Free Fall Environments

• Aircraft

• Sounding Rockets

Simple Free Fall Environments

• Drop Towers

Orbital Free Fall Environments

• Space Shuttle

• Satellites

• Space Station

The Shuttle and Satellites have already been mentioned, but in every case the objects under study are in free fall.

Aircraft

Airplanes can fly in parabolic arcs to achieve short durations of free fall. On the upward arc, the thrust of the airplane is adjusted so that there is no lift: the plane is in free fall since nothing reduces the force of gravity. The plane remains in free fall over the top of the parabola and part of the downward arc. Microgravity conditions are achieved for time periods of 15 to 20 seconds, with g levels of ± 0.02 g. By free floating experiments, low g-levels can be achieved for 5 to 8 seconds.

T-33

Since the inception of the T-33 program in 1988, this aircraft was a successful mini low-gravity laboratory. The National Research Council (NRC) operated this modified jet trainer for one short duration (approximately 20 seconds) microgravity experiment per flight. The T-33 flew up to 16 parabolas per flight. Because of its singular experiment capacity, the T-33 was eventually retired and replaced by aircrafts able to support a greater number of experiments.

KC-135

Since the mid-80s, NASA's KC-135 parabolic flight aircraft provided the Canadian microgravity community with access to a low-gravity environment. The Canadian Space Agency leased the modified Boeing 707 four-engine jet for two campaigns per year. Each campaign consisted of three to four flights during which 40 parabolas were completed. One parabolic manoeuvre provided 15 to 20 seconds of 0.01 g or less which was followed by a 2 g pull-out. The KC-135 carried up to 21 persons performing 12 different experiments. In 1995, the CSA decided to implement a DC-9 parabolic flight program, also leasing from NASA, and leave the KC-135 in the hangar.

Falcon-20

The Flight Research Laboratory of the NRC implemented the Falcon-20 parabolic flight program in 1991; its first parabolic flight with a microgravity experiment onboard was flown in December 1993. This business jet aircraft has the capacity to accommodate a maximum of three experiments and two experimenters. Two flights can be flown in one day, with each flight achieving up to four parabolas. Each parabola lasts approximately 75 seconds, of which 15 to 20 seconds are at 0.01 g or less, followed by a 1.8 g pull-out. The aircraft has proven capable in providing microgravity conditions similar to or better than those experienced onboard the KC-135.

DC-9

The latest parabolic flight program offered to Canadian experimenters by the MSP is centered on the use of NASA's DC-9 aircraft. With its first flight in May 1995, this refurbished jet achieved 35 parabolas per flight. In only a few months, the aircraft's range has been extended to 40-50 parabolas per flight. Each parabola provides 20-30 seconds of low-gravity conditions, followed by a 2.2 g pull-out.

Sounding Rockets

Sounding rockets achieve longer durations and higher quality of microgravity than do airplanes. At an altitude of only 100 km, the air is 10 million times less dense than on Earth's surface and the resistive force of drag is greatly diminished. Once the rocket engine is shut off, the only acting forces are gravity and a negligible drag; the rocket is in free fall. Rockets achieve microgravity qualities of 10^-5 g from six to fifteen minutes.

CSAR

The Microgravity Sciences Program provides researchers and scientists from Canadian industry and universities with low-cost, high-quality microgravity flight opportunities aboard the Canadian Space Agency Rocket (CSAR), a Black Brandt rocket developed by Bristol Aerospace Ltd. The first rocket, CSAR-1, was launched in October 1992 and carried five experiments; CSAR-2 was launched in December 1994 and also carried five experiments. Both launches took place at the White Sands Missile Range in White Sands, New Mexico. The Canadian experiments onboard, subjected to six minutes of high-quality microgravity conditions, were designed to advance our understanding of the processes and behaviours of materials, which will lead Canada to improving product manufacturing on Earth and enhancing the development of erosion-resistant materials.

Drop Towers

A drop tower is a long vertical shaft from which air is evacuated. When experiments are dropped into the shaft, they experience microgravity conditions. Drop towers typically achieve microgravity qualities of 10^-4 g from 2.2 to 10 seconds. Implemented by the MSP in 1992, the Drop Tower Program includes the use of drop tubes. In a drop tube, only the melted sample is dropped whereas, in drop towers and shafts, both the sample and its apparatus are dropped. Although the microgravity time provided by the drop is shorter than that of parabolic aircrafts (15 to 20 seconds), experiments dropped down towers and tubes undergo less disturbance than those flown in an aircraft. Drop towers and tubes have been used for a variety of experiments such as liquid crystal diffusion and containerless processing of metallic materials.

International Space Station

The International Space Station will provide a high quality microgravity environment for practically unlimited durations. The Space Station's facilities will include habitat modules and six laboratory modules.