PRECISION EDM 

ON A MISSION TO MARS

After a 310 million-mile space journey, 

Pathfinder landed on Mars on July 4th, 

thanks in part to theMaroney Company

 and their EDMs.

Maroney, a Northridge, CA, company, worked closely with (JPL) in machining more than 150 precision parts using their Mitsubishi wire and sinker EDMs. "This is a very exciting time for Maroney," says company President, John Cameron. "It is an exceptional quest to be a part of, after years of involvement with JPL. This is a project everyone can appreciate."

   About 65% of the parts completed for the six-month trip to Mars required both wire and sinker EDM. Maroney used their V25FS and other Mitsubishi EDMs, including an EX8, an SX20 and a DWC110SA, for the Pathfinder project. Among the pieces machined for the lander and its six-wheeled rock-analyzing rover, were hardware for the air bag retraction housing used during landing and the high-gain antana used to communicate with Earth throughout the mission.  

   The reason for machining with EDM was the need to make infinite adjustments in gear tooth form and shape without using custom hobs and shapers or new master gears for each new  tooth form. Maraging Vascomax C200 steel, a material known for its high yield strength and toughness, was used for the air bag retraction actuator. Almost all the parts used in the high-gain antenna were machined from titanium or aluminum for light weight and high strength.

Mars Mission Details

The Primary mission of NASA's Microrover Flight Experiment (MFEX) is to determine rover vehicle performance in the poorly understood, Martian terrain. Following the many months of cruising through interplanetary space, and a spectacular landing on the Martian surface, the micro rover deployed from the lander to begin a mission consisting of technology experiments, including determining wheel-soil interactions, autonomous and hazard avoidance capabilities, and engineering characterizations power generated performance, etc.

    MFEX has three main mission objectives: technology experiments, including soil mechanics and types, and material abrasion and adhesions; science experiments; and mission experiments. In addition, the rover's alpha proton x-ray spectrometer (APXS) will be deployed on rocks and soil to provide element composition for analysis. Lastly, to enhance the engineering data return of the MPF mission, the rover will image the lander to assist in status/damage assessment. Overall, the rover's mission is designed to show the way for making future rovers more effective in navigating and moving around the surface of Mars.

    Documentation for the rover and the Pathfinder, and drawings of the project, are available at the NASA (National Aeronautics and Space Administration) site on the internet: http//www.nasa.gove.

 Cruising the Martian Landscape 

   The micro rover is a six-wheeled vehicle consisting of a "rocker bogie" design which enables it to traverse obstacles a wheel diameter (13 cm) in size. Each wheel is independently atcuated and geared (2000:1) to provide superior climbing capability with a top speed of 0.4 - 0.7 meters per minute (1 - 2 feet per minute). The front and rear wheels are independently steerable, enabling the vehicle to turn in place.

  The rover itself weighs 11.5 kg. (25.4 lb), with 6kg (13.3 lb) allocated to lander-mounted rover telecommunications equipment, structural support of the vehicle and it's deployment mechanisms. The deployed rover is 630 mm (24.5") long x 480 mm (18.7") wide, with a normal height of 280 mm (10.9") and ground clearance of 130 mm (5"). Space on board the lander forces it to squat to a height of 180 mm (7") when stowed.

    Vehicle power is supplied by a solar panel backed up by 9 lithium D-cell sized primary batteries, providing up to 150 watt-hours. The combined panel/batteries system allows the rover to draw up to 30 watts of peak power while the peak panel production is 16 watts. The normal driving power requirement for the rover is 10 watts.

      Rover components not designed to survive ambient Mars temperatures (-110 C during a Martian night) are contained in the warm electronics box (WEB). The WEB is installed, coated with high and low emissivity paints, and heated by resistive heating under computer control during the day and waste heat produced by the electronics. This design allows the WEB to maintain components between -40* C and + 40* C during a Martian day.

      Vehicle motion control is accomplished by switching power to the drive or steering motors. An average motor encoder (drive) or potentiometer  (steering) readings determine when to power the motors. When motors are off, the computer conducts proximity and hazard detection by using it's laser striping and camera system to determine and presence of obstacles in its path. The vehicle is steering autonomously to avaoid obstacles while continuing toward its goal location.

       Command and telemetry is provided by modems on the rover and lander. During the day, the rover regularly requests transmission of and commands sent from Earth and stored on the lander. When commands are not available, the rover transmits any telementary collected during its last interval between communications sessions. The data received by the lander is stored and forwarded to Earth as part of the lander telementary. In addition, this communication system is used to provide a "heartbeat"  signal during vehicle driving. While stopped, the rover sends a signal to the lander. When the lander responds, the rover proceeds to the next stopping point on the way to it's goal.

        At the end of each sol (Mars day) of rover travel, the camera system on the lander takes a stereo image of the vehicle in its terrain. Those images, portions of a terrain panorama and supporting images from the rover cameras are displayed at the control station on Earth. The operator is then able to designate the goal locations for the rover's next exploratory venture on the terrain's display points.

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