The size and weight of the MSL and its spacecraft will require a more powerful launch vehicle than the Boeing Delta II used for the previous Mars rover missions. The entire MSL spacecraft payload is expected to be 2,800 kilograms with a heat shield/spacecraft diameter of 4.5 meters. The Viking 1 and 2 landers and their orbiters were launched aboard Titan/Centaur rockets with solid rocket motor boosters. The Titan IV rocket was retired in 2005 so available alternatives have been studied. The Titan IV was replaced by Boeing's new Delta IV and Delta IV Heavy, and the Lockheed Martin Atlas V with Centaur upper stage is also a possible launch vehicle. The Delta IV family of launch vehicles is very versatile. The Delta IV Medium+ with Delta III upper stage, five-meter-diameter payload fairing and two strap-on Alliant 1.5-meter solid rocket graphite epoxy motors is capable of boosting 4,640 kilograms to geosynchronous transfer orbit (GTO) and on to Mars. The Atlas V family of launch vehicles is equally varied. The Atlas V (version 501) with five-meter fairing and no additional boosters is capable of launching a 3,971 kilogram payload to GTO. Both Delta IV and Atlas V are capable and reliable launch vehicles, and NASA's decision on which to use may have simply been based on costs for the launch vehicle and launch support. NASA considered both of these launch vehicles carefully before selecting Lockheed Martin Commercial Launch Services, Inc. in June 2006. They will deliver an Atlas V to launch the MSL from Launch Complex 41 at Cape Canaveral Air Force Station in Florida.
The MSL spacecraft that will go atop the Atlas rocket will have a similar configuration as that for the Mars Exploration Rover mission. It will include the cruise stage, the aeroshell with backshell and heat shield and, within the aeroshell, the parachute system, powered descent stage with Sky Crane, and the MSL rover. The cruise stage will make several trajectory corrections and will separate from the aeroshell prior to entering the Martian atmosphere. After atmospheric entry and maximum deceleration, the parachute will deploy, slowing the spacecraft further.
The heat shield will be jettisoned and start of the MARDI phase of descent and once powered descent is initiated, the backshell and parachute will separate from the Sky Crane. The MSL, with its suspension and wheels fully deployed, will be slowly lowered from the Sky Crane to the Martian surface by cables as the powered descent stage hovers in position. Once the MSL is on the planet's surface, the cables will be severed and the descent stage with Sky Crane will fly away and crash land a safe distance from the MSL.
Once on the surface, the MSL will go through a complete system checkout phase and verification of system health with JPL. Landing in 2010, the MSL will begin a new decade of Martian exploration with countless new discoveries to be made.
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