Mars Pathfinder Passes Major Set of Engineering Milestones

June 14, 1995

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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