PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Contact: Diane Ainsworth
FOR IMMEDIATE RELEASE
June 14, 1995
MARS PATHFINDER PASSES MAJOR SET OF ENGINEERING MILESTONES
Mars Pathfinder, a NASA Discovery program mission designed to
deliver a lander, camera and instrument-laden rover to the Martian
surface on July 4, 1997, has successfully completed an initial
series of engineering tests intended to validate the spacecraft's
unique atmospheric entry, descent and landing techniques.
Mars Pathfinder will employ a new and unconventional approach
to placing a lander on the surface of Mars, in keeping with NASA's
new "faster, better and cheaper" philosophy of planetary
exploration, said Tony Spear, Pathfinder project manager at NASA's
Jet Propulsion Laboratory.
"This series of diverse tests has given us great confidence
that the spacecraft will arrive safely and securely on Mars,"
Spear said. "A truly exciting scientific mission will then be
ready to unfold."
The Viking 1 and 2 Mars landers of the mid-1970s used a
complex, computer-controlled liquid retrorocket system to achieve
a soft landing at about 8 kilometers per hour (5 miles per hour).
In contrast, the smaller, tetrahedral-shaped Pathfinder lander
will instead use a combination of parachutes, solid rockets and
inflatable air bags to perform a safe, relatively hard landing of
about 56 kilometers per hour (35 miles per hour).
Recent parachute drop stability tests were performed by
Pioneer Aerospace of Windsor, Conn., in the desert near Yuma,
Ariz. These tests successfully demonstrated the parachute
configuration that will be used to bring the lander gracefully
through the thin Martian atmosphere, said Ann Mauritz, JPL lead
subsystem engineer.
Another element of the spacecraft's descent subsystems, the
solid rocket motors, were tested at the China Lake Naval Weapons
Center in Ridgecrest, Calif. These tests involved dropping a
simulated lander on a parachute from a helicopter and then firing
three prototype solid rockets to further slow the craft's fall
toward the surface.
The tests went just as predicted, said Dr. Les Compton, JPL
lead subsystem engineer, with the simulated lander essentially
coming to a dead stop in mid-air while at the same time
maintaining a stable orientation with respect to the ground.
Full-scale rocket prototypes, recently tested by Thiokol
Corporation at Elkton, Md., will be used in full-scale subsystem
tests to be carried out at China Lake later this summer.
Pathfinder's landing will be cushioned by four large air bags
attached to the outside of each of the lander's four metallic
exterior "petals." The air bag-based soft landing was recently
demonstrated by the air bag designers, ILC Dover of Frederica,
Del., inside a 36.5-meter (120-foot) vacuum chamber at the NASA
Lewis Research Center's Plum Brook Station near Sandusky, Ohio.
The vacuum chamber provides a way to simulate the very thin
atmosphere of Mars, and the tests demonstrated the viability of
the air bag design in softening the force of the impact on the
lander and its delicate payload.
The air bag was dropped from a height of 21 meters (70 feet)
onto a 12-meter (40-foot) platform containing many large rocks
similar to those found on Mars, said Tom Rivellini, JPL lead
subsystem engineer.
"Initial full-scale prototype drop tests were very
successful," Rivellini said. "Engineers were able to test several
air bag fabric construction techniques simultaneously. The tests
showed that air bags constructed of a double-layered fabric will
be necessary to provide a sufficiently rugged cushioning effect."
A second phase of prototype drop testing later this year will
demonstrate the durability of the new double-layered air bags at
even higher impact levels.
Like Viking, the Pathfinder lander will arrive at Mars
packaged inside a space capsule-shaped entry vehicle. Hitting the
thin upper atmosphere of Mars at more than 27,000 kilometers per
hour (17,000 miles per hour), the entry vehicle's heat shield will
slow the craft to a relatively paltry 1,450 kilometers per hour
(900 miles per hour) in about two minutes. An onboard computer
will sense the slow-down in speed and then eject a large
parachute. The parachute can slow the lander down to about 250
kilometers per hour (155 miles per hour) in the rarified
atmosphere of Mars, which is only 1/100th as dense as Earth's
atmosphere.
An onboard radar altimeter inside the lander will monitor the
distance to the ground. At about 100 meters (330 feet) above the
surface, the computer will inflate the air bags.
Seconds later, three 3/4-ton-thrust solid rocket motors
placed inside the top half of the entry vehicle above the lander
will be fired. In approximately two seconds, the rockets will
bring the lander to a dead stop some 12 meters (40 feet) above the
Martian ground. The parachute will be released, and the lander,
nestled inside its protective air bag cocoon, will fall to the
ground, bouncing and rolling until it stops.
Within about an hour, the air bags will be deflated and
partially retracted toward the lander. Pathfinder will then open
its three metallic petals and stand itself right side up from any
side that it happens to be lying on. The microrover, attached to
the inside of one of the petals, will be exposed to the Martian
terrain for the first time. After the lander camera has taken a
photograph of its position on the Martian surface, engineers will
decide which exit ramp the rover should roll down and instruct it
to drive off and begin exploring the immediate surroundings, part
of an ancient Martian flood plain known as Ares Vallis.
Scheduled for launch in December 1996, Mars Pathfinder is
part of a new generation of low-cost spacecraft with highly
focused science goals designed to explore planets and other
celestial bodies of the solar system. Discovery missions are
capped at $150 million each and must be developed and readied for
launch within 36 months.
Mars Pathfinder is managed by the Jet Propulsion Laboratory
for NASA's Office of Space Science, Washington, D.C.
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