May 1997 Volume 6 Number 2
Mars Pathfinder Landing Sequence
by Amalia Kingsbury, ASU College of Education and Arizona Mars K-12 Education Program
On July 4, 1997, a bright streak, like a "shooting star," will zip across the cold, crisp, nightime martian sky. Mars Pathfinder will enter the atmosphere at speeds of more than 17,000 miles per hour. The spacecraft will finally be reaching the Red Planet after a 7 month, 500 million mile journey.
The first step in the "Entry, Descent, and Landing (EDL)" sequence takes place about 30 minutes and 5,000 miles above the planet. The cruise module separates from the lander as Mars Pathfinder barrels its way toward Mars. The cruise module, which includes solar panels, fuel tanks, and rocket thrusters is the stage that, up to this point, was used to get the lander to Mars.
About four minutes before touchdown, Mars Pathfinder will enter the atmosphere. The entry stage uses the spacecraft's own velocity to slow down. This creates friction or drag, much like the sensation you get when you put your hand out the window of a moving car. This process is called aerobraking, and it will slow the spacecraft to about 900 miles per hour. All of the energy lost during aerobraking is converted to heat and is absorbed by the heat shield.
Two minutes before landing, a parachute is released. A few seconds later, the heat shield separates and the lander is lowered on a 65-ft tether.
Eight seconds before landing, Mars Pathfinder will inflate its giant airbags. It will also fire braking thrusters to further slow the descent. Two seconds before landing, the tether is cut, and the lander/airbags drop toward the ground at about 60 miles per hour.
Touchdown! Mars Pathfinder will bounce and roll for about 5 minutes. Once it has stopped, the airbags will deflate and retract. Next, the solar panels open. Mars Pathfinder is ready for exploration!
In the U.S., the first pictures should come back in the evening of July 4th. Watch for these events on T.V.!
TES News is published quarterly by the Arizona Mars K-12 Education
Program. This newsletter may be copied for EDUCATIONAL PURPOSES ONLY.
EDITED BY Kenneth S. Edgett, Arizona Mars K-12 Education Program,
Arizona State University, Tempe, Arizona, USA.