CHALLENGER'S LOST LESSONS - ER - NASA

14Another problem to address was the force actuator ortrigger device. Some means had to be provided for the teacher toapply the same amount of force to different objects accurately,repeatedly, without imparting other influences.Using the retraction mechanism of a ball point pen wasconsidered. This posed difficulties. Though the teacher wouldbe able to exert the force through the center of mass of thesphere easily, it would prove difficult to aim the pen whileholding it next to the ball before triggering it to send the ballalong the desired path. Remember, this would be performedwhile the demonstrator and the ball were free-floating, subject toair currents set up by the ventilation system.The resulting actuator uses the vacuum created by suctionon a tube to hold the ball against a flexible cup. The ballcompresses a coil spring protruding from the center of the cup.Thus captured, the ball may be aimed accurately so that it willfollow the desired path in front of the cloth metric measure stripthat will be Velcro attached to the 4'x 6' backdrop affixed to themid-deck locker doors to improve visibility of objects duringfilming. Using two different springs and the vacuum system theteacher can release the spheres at the same time, using the sameforce repeatedly.Ball point pen retractors or something similar may beused in 1 g on a billiard ball and ball bearing sitting on a leveltable or on a V-groove track to duplicate this activity in theclassroom.EFFERVESCENCEThe goal of the effervescence activity was to understand whyproducts may or may not effervesce in a microgravity environment.The object was to show the action of bubbles produced in amicrogravity environment and to observe the lack of buoyancy. Theactivity originally called for a clear plastic container, open on top,an