LRS Micro-g LaCoste FG5, Руководство пользователя, Страница: 14 / 149

Design: Components and Function
2
2.1.1.CART/DRAG-FREE CHAMBER
The cart /drag-free chamber (Figure 2-4 and Figure 2-5) houses the test mass .
The purpose of the drag-free chamber is to reduce the residual air drag inside the
evacuated dropping chamber. The chamber also reduces magnetic and
electrostatic forces on the test mass, and provides a convenient method for
dropping and catching the test mass, as well as returning it to the top of the
chamber for the next drop. A
L ight E mitting D iode (LED) , located on the cart,
directs light through an optical glass sphere attached to the test mass. The
sphere focuses the light onto a linear detector , also mounted on the cart. This
system senses the position of the cart with respect to the test mass. A servo-
motor/drive belt system (Figure 2-2) moves the cart inside the Dropping
Chamber, using active feedback from the position sensor to maintain the cart in a
constant position relative to the test mass during free-fall. Since there is
essentially no relative motion between the test mass and the drag-free chamber,
the effects of residual air drag are eliminated.
Figure 2-4
Front view of the cart/drag-free chamber
2-4