Final Project

Curtis R.

Legislator:  Ignacio Salinas, Representative

(Click on image above to enlarge.)

A New Rover

Nearly everyone has heard of the Pathfinder mission that landed on Mars on July 4, 1997.  It was highly successful, returning many photographs and information from the Martian Surface.  But there were limitations and problems.  For example, the range of the rover was half of a kilometer from the lander base.  The batteries were not rechargeable.  These are not design flaws; they were the best technology available in 1996 and 1997.  It is now 2001.  You can’t buy a computer now without something better coming along in a few months.  Technological advancements occur every day.  We’ve had over one thousand days since 1997.  I propose that we send a new mission to Mars.  This mission would include sending a rover, lander base and a satellite to Mars.  Looking at the success of the Pathfinder mission, we should not build a new rover from the ground up, but improve on the old mission.

Let’s look at a few problems that we could improve on.  First:  we can enlarge the size of the rover.  This will allow it to go over more rugged terrain, will make it more survivable, and will allow for larger components such as equipment or computers.

Next:  The object avoidance system.  This wasn’t really a problem.  But if we can improve on it, we should.  The original system used a laser ranging system and vehicle tilt and turn sensors.  This should be replaced with the new LADAR system.  LADAR is a laser-radar.  This allows a very detailed look at the surroundings.  This used with object avoidance software could be better than the old system.

Then there is the battery problem.  The batteries used on the Sojourner were not rechargeable.  At the time, no low mass/low complexity/low cost solutions for batteries were available.  The batteries selected were good enough for the 30 day extended mission, which is relatively short.  After the batteries were expended, the solar panel became the primary power source.  This disabled certain functions.  By using rechargeable batteries (which many missions now use), the length of the mission could be substantially extended without loosing effectiveness.  The batteries

The solar panel on the Sojourner was fixed in place.  The panel on the new rover should be able to tilt to follow the sun.  This will allow the rover to get maximum power from the sun at all times.  When the rover senses that the power received has dropped, it will check the Martian clock against its position and move the panel accordingly.  If the power level drops and the panel is still in the optimum position, the rover assumes that the cause is weather.  It will move the panel into the optimum position every fifteen minutes until the storm clears.  The rover will check with the satellite for positioning and weather data.  This mobile panel could also be useful if the panel became covered with dust.  The Sojourner solar panel is covered with glass.  The panel on the new rover is covered with hard clear plastic.  This makes it much stronger.

The speed of the rover will be improved.  The speed of the old rover was .4 meters per second.  This was because of the gear ratio, optimized for crawling through sand.  The new rover is larger, with larger and better wheels, so the rover could move faster.  This would deplete the batteries quicker, but since they are rechargeable, it doesn’t matter.  This would also allow objectives to be completed quicker.

Now that we have more speed and more power, we need more room to work with.  The Sojourner’s range was about 500 meters from the lander base.  This must be improved upon.  The data transfer rate from the lander base to the rover was about 2400 bps.  Our modems are much better now.  We could probably double that in clear weather.  This will give us much more room to work in.

The Sojourner’s computer was good for its time, but now there have been huge advancements in processor speeds and disk size.  The Sojourner had a 2 MHz processor and 64 KB of RAM.  The new rover could have a much faster processor, such as an 800 MHz to a 1 GHz processor, with 128 KB of RAM, and a 20 GB hard drive for storage of software and temporary data.

The Sojourner’s antenna allowed it to communicate adequately to the lander base.  The new rover’s satellite dish will allow a greater communications range.  This will always stay pointed to the lander base.

The new rover has a pair of robotic arms.  This is a great improvement over the old rover.  This allows for the rover to be able to scan the bottom of small rocks.  Certain obstacles can be moved instead of traversed or gone around.  In case the rover is flipped over, the arms could be used to right its self.

Now, there are enhancements that were not part of the Pathfinder mission, such as the satellite.  The satellite included in the mission would be a communications/weather/positioning satellite.  The rover would transmit to the lander base, which would then relay that to the satellite in geo-synchronous orbit with the base.  The satellite would then relay the information to Earth.  The chain would work in reverse when receiving data from Earth.  If the satellite were unable to communicate with the Earth for some reason (such as Mars blocking the line of site to Earth), the satellite would save the data and retry every minute.  The satellite would also send information to the rover to stop and wait for communications with Earth to resume.  The satellite could also help planning of the rover’s tasks by mapping the area and tracking the rover, then sending the data to Earth.  This satellite would also be a weather satellite.  In case of an unexpected upcoming severe storm, the satellite would command the rover to return to the base into its housing.  The satellite is solar powered with rechargeable batteries.

The lander is a cube with parachutes and inflatable airbags.  There are four airbags per face of the cube.  When the lander gets to a certain distance from the ground, the airbags inflate mostly full.  The reason they don’t fully inflate is so they absorb the shock of the landing better.  The bags on the bottom are smaller so to help land on the right side.  If the lander stops on the wrong side, the two bags on the current bottom on the side needed to turn over begin to deflate.  The other two fully inflate, causing the lander to turn over.  This process repeats until the lander is right side up.  Then the bags deflate.  The lander base then unfolds, uncovering a satellite dish, a rover housing, and a large solar panel.  This panel powers the satellite dish.  In case of a severe storm, the rover will return to the housing and the lander will fold itself back up to protect the equipment.

Mars is an important step in exploring space.  If we can successfully send a man to Mars, we will have more than a giant leap for mankind.  Learning about the planet is vital to inhabiting it.  If we find life on Mars, we will have proved the existence of life on another planet.  A rover will help us by scanning rocks for signs of life.  This rover mission could be singularly the most important mission to Mars ever.

Sources Cited:

http://mars3.jpl.nasa.gov/MPF/rover/faqs_sojourner.html/

http://www.atk.com/defense/descriptions/products/smart-weapons/ladar.htm/

http://www.jpl.nasa.gov/calendar/1997.html/

Last Updated:  09/10/01