This view of a portion of the descent stage of NASA's Mars Science
Laboratory shows two of the stage's three spherical fuel tanks flanking
the bridle device assembly. The photograph was taken in early October 2008
from the center of the descent stage looking outward. The top of the
descent stage is toward the top of the image.
The bridle device assembly is about two-thirds of a meter, or 2 feet, from
top to bottom, and has two main parts. The cylinder on the top is the
descent brake. The conical-shaped mechanism below that is the bridle
assembly, including a spool of nylon and Vectran cords that will be
attached to the rover.
When pyrotechnic bolts fire to sever the rigid connection between the
rover and the descent stage, gravity will pull the tethered rover away
from the descent stage. The bridle or tether, attached to three points on
the rover, will unspool from the bridle assembly, beginning from the
larger-diameter portion. The rotation rate of the assembly, hence the
descent rate of the rover, will be governed by the descent brake. Inside
the housing of that brake are gear boxes and banks of mechanical resistors
engineered to prevent the bridle from spooling out too quickly or too
slowly. The length of the bridle will allow the rover to be lowered about
7.5 meters (25 feet) while still tethered to the descent stage.
The Starsys division of SpaceDev Inc., Poway, Calif., provided the descent
brake. NASA's Jet Propulsion Laboratory, Pasadena, Calif., built the
bridle assembly. Vectran is a product of Kuraray Co. Ltd., Tokyo. JPL, a
division of the California Institute of Technology, manages the Mars
Science Laboratory Project for the NASA Science Mission Directorate,
Washington.