Slowing to Mars Speed

When the Mars Science Laboratory (MSL) goes streaking through the Martian atmosphere at more than twice the speed of sound, it’s going to need one of the largest parachutes ever used in a space mission to successfully land a car-sized rover on the Red Planet. The parachute, built by Pioneer Aerospace, has 80 suspension lines, measures more than 50 meters (165 feet) in length, and opens to a diameter of nearly 17 meters (55 feet). It is the largest so called “disk-gap-band” parachute (more on that in a minute) ever built. To get ready for the scheduled 2009 launch of MSL, engineers have begun testing different parts of the parachute in preparation for the ultimate test of the entire parachute system.

Recent successful trials of two parachute packing techniques were performed in the world’s largest wind tunnel at NASA’s Ames Research Center. Engineers loaded chutes into a cannon and fired them out at 85 mph to simulate events during the real landing, looking for damage to line attachments and other parts. All four tests were successful, and high-speed video data is now being analyzed to select a final parachute design for the mission. But the large parachute is just the beginning of the unique landing technique MSL will use.

MSL will be the first planetary mission to use precision landing techniques, using a rocket-guided entry with a heat shield to steer itself toward the Martian surface similar to the way the space shuttle controls its entry through the Earth’s upper atmosphere. In this way, the spacecraft will fly to a desired location above the surface of Mars before deploying its parachute for the final landing. MSL will use a scaled-up version of parachutes used for the Viking and Mars Exploration Rovers mission. Called a Disk-Gap-Band parachute, the name describes the construction of the parachute: a disk forms the canopy, then a small gap, followed by a cylindrical band.

The parachute is deployed using a mortar that is triggered when the vehicle reaches a fixed planet-relative velocity. The parachute is designed to survive loads in excess of 36,000 kilograms (80,000 pounds).

Twice as long and three times as heavy as the Mars Exploration Rovers, MSL is too massive to use airbags like MER. MSL’s large parachute will only be deployed 3 minutes before touchdown which should slow the incoming vehicle enough for retro rockets to fire for the final 500 meters (1,640 feet) of the descent. But after that is where it gets interesting: In the final seconds, the hovering upper stage would act as a crane, lowering the upright rover on a tether to the surface. This is first the “Sky Crane” system will be used in a space mission.

MSL, a roving analytical laboratory, will collect Martian soil and rock samples and analyze them for organic compounds and environmental conditions that could have supported microbial life now or in the past.

Original News Source: JPL Press Release