DEMONSTRATOR DESCRIPTION

The demonstrator provides approximately 0.1g for 0.6sec. It consists of four essential parts: (1) an experiment carriage, (2) a drop structure to hoist the carriage to the top and then release it into a free-fall drop, (3) a deceleration system at the bottom to catch the experiment, and (4) a computer and a monitor to record the experiment during the drop and replay it afterwards.

(1) The experiment carriage consists of a video camera and one of several interchangeable physics or chemistry experiments (described later). The carriage is hoisted to the top of the drop structure via a rope and pulley.

 Figure 1. - Experiment Carriage

(2) The drop structure provides a rigid means by which one can easily raise and release the experiment carriage. The structure is segmented for easy assembly and provides a fall distance of approximately 2m. Based on this height, one can calculate the time it will take for the package to hit the bottom (neglecting air resistance), from the following equation:

where h is the height that the carriage falls, g is the Earth's local gravitational acceleration (=9.8m/s2) and t is the time of free-fall. Hence, for h=2m, the carriage will fall for approximately 0.6 seconds.

(3) The deceleration system consists of a shipping crate lined with foam to cushion the impact of the video camera and experiment payload when they hit the bottom. The drop structure is mounted on internal side walls of the crate. The crate is also designed to hold the drop structure and experiment payloads during shipping.

(4) The video system consists of a video converter and a computer that are connected to the output of the video camera mounted on the experiment carrier. It is used to record the experiment during free-fall. The software is used to "replay" the video as frame-by-frame to slow down the video to clearly show what happens during the drop.

 Figure 2. - Schematic of Reduced-Gravity Demonstrator

SUGGESTIONS ON HOW TO BUILD YOUR OWN DEMONSTRATOR

(1) Experiment Carriage: The experiment carriage can be as simple as a wooden board to which the experiment and video camera are mounted. However, It is suggested that you include some sort of "roll bar" to protect the hardware if the carriage bounces and lands upside down.

(2) Drop Structure: A drop structure is useful, but not required for reduced-gravity demonstrations. The structure merely provides a convenient way of hoisting and releasing the experiment carriage. Instead, someone could simply hold the experiment carriage in their hands and let go to initiate a drop. If an increased fall distance is required, the experiment carriage could be dropped by someone standing on a chair or stepladder. Alternately, in some rooms it may be possible to hang a pulley from the ceiling or from a basketball hoop.

(3) Deceleration System: The experiment carriage can be caught in a large cardboard box or a large container filled with some cushioning. The Reduced-Gravity Demonstrator uses layers of foam, but down pillows (fluffed up of course) or Styrofoam "peanuts" would probably be even better. Instead of slowing down the carriage, the foam tends to simply make it bounce.

(4) Video System: For the demonstrator to work, you must be willing to drop a video camera on the experiment carrier. Modern video cameras are relatively rugged and are used in the NASA microgravity facilities. A board camera (literally a circuit board with a lens) is a good option, since it is both small and inexpensive. Modern digital cameras with video modes may also be used. If a camera is used with on-board SD-type memory card, that card can be removed from the camera after several drops or a cable can be connected to a computer to extract the video files. A video converter is sometimes required between the camera and a computer for real-time recording by the computer.  Since the experiment only takes a fraction of second, it is very useful to be able to play back the recorded video in slow motion. Computer software should be capable of relatively quickly replaying the recorded video and it should also be able to play either frame-by-frame, slow-motion, or both.

 Reduced Gravity Demonstrator Related Information
 Webmaster: Tim Reckart NASA Official:Nancy R. Hall Last Updated: November 28, 2011