The cruise stage carries a spacecraft through the void of space and delivers it to Mars.
Similar in design to cruise stages on the Mars Pathfinder and Mars Exploration Rover missions, the cruise stage for Mars Science Laboratory will weigh about 880 pounds (400 kilograms). During launch, it will communicate with the rocket system that will blast it into space. In approaching the atmosphere of Mars, the cruise stage will communicate with the entry vehicle that will carry the rover to the planet's surface.
Along the way to Mars, the cruise stage will perform five or six trajectory corrections to adjust the spacecraft's path toward its final, precise final landing site on Mars. Meanwhile, the flight computer on board the rover will continually check the health of the spacecraft and relay the information to the cruise stage, which will then send the information to mission controllers via two antennas that communicate in the X-band.
A key task of the cruise stage will be to control the temperature of all spacecraft systems. In some cases, fluids will circulate through pumps and radiators in the Heat Rejection System and then dissipate the heat generated by power sources, such as solar cells and motors, into space. In other cases, insulating blankets will keep sensitive science instruments warmer than the near-absolute zero temperature of space. Thermostats will monitor temperatures and switch heating and cooling systems on or off as needed.
Mars Science Laboratory will use the stars to navigate. An onboard star scanner will keep the cruise stage on track by constantly monitoring its position relative to stars in our Milky Way galaxy.
Cruise Mechanical Structure
The cruise stage will have a central aluminum machined structure, with support ribs, solar arrays, a radiator, and an adapter for connecting the vehicle to the rockets that will launch it from Earth. The structure will fit inside a broad, circular fairing about 4 meters (13 feet) in diameter. Upon reaching Mars, a cable cutter will separate the cruise stage at precisely the right moment from the aeroshell that will shield Mars Science Laboratory from frictional heat during its descent through the martian atmosphere.
The cruise stage will have its own miniature propulsion system, consisting of eight thrusters to be fired on command using hydrazine fuel in two titanium tanks. It will also have its own power system, consisting of a solar array and battery for providing continuous power. The vehicle will maintain forward momentum by spinning about its central axis at two revolutions per minute.