Tires on the ground ...

Okay, doing that will allow it to fall over but it will have a shorter wheel base if it does. The "L" shaped arms would stop that but would bring in two more bearings, and the clearance for them would open a gap between the tread and body.

On these dust storms; do they generate electrostatic charges and even huge explosions?

Is this better.

Stoat, thanks for the rendering. I am not sure about the electrostatic nature of the martian storms, but would infer that particle sliding will genenerate static charge. This is normally solved on earth by trailing a chain behind a vehicle. This is quick and dirty but a more high tech method could be involved. I think this is a problem that further study of the large operating rovers would reveal. NASA has most likely hammered this problem out as well as many others we haven't considered. Next week I want to attempt to find some material lists for current rovers to see which materials are used and in what frequency for each component. This may shed some light on how to solve some technical problems.

Mark

Stoat,

The prototype can be simplified. Remove the two middle/upper wheels.

As long as the the diameter of the four corner wheels is larger than the thickness of the rover body and the wheel axels are centered on the body thickness, there will be equal ground clearance, and no change in wheel base, whichever side is up.

WheelDiameter = BodyThickness + (DesiredClearance * 2)

agreed on the four wheel variant.

What about adding a trailer bar type hitch structure to the rear, perhaps a high torque model could pull and deploy sensors/experiment transmitter trailers, sort of like an arctic crawler train. What do you think?

Mark

In the initial message of this topic, Larry Burford wrote <blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"> A GPS-like system would need to be set up around Mars so that these little rovers would be able to navagate and communicate. <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
The communications relay function is clearly necessary, and not particularly difficult (in comparison with the rover design, delivery, navigation/control, etc.). However, a GPS-like positioning system, with sufficient accuracy to be useful in guidance/navigation of small rovers would be exceedingly difficult to deploy around Mars, and should not be a required element of this system concept.

The difficulty arises because GPS is not just a constellation of satellites carrying atomic clocks -- GPS is a <b>closed-loop</b> system, and its accuracy depends on this. The GPS satellites are continuously tracked, using precise, two-way ranging from five, terrestrial control stations with precisely-known locations. The measured oscillator drifts and ephemeris corrections are uploaded to the satellites and broadcast on their downlink signals to permit accurate position calculation at the GPS receivers. The major contributors to ephemeris changes are atmospheric drag, which ought to be considerably smaller for Mars; and orbital pertubations, which ought to be considerably greater for Mars, due to the offset of its center-of-mass from center-of-figure, its greater orbital eccentricity, and its periodic (relative) proximity to Jupiter.

Rather than depend on GPS-like positioning for rover navigation, I recommend that the rovers navigate strictly from commands and inputs from local sensors. Determination of rover locations on the Martian surface can be accomplished using a small set of data-relay satellites, each equipped to perform bidirectional ranging to individual rovers (facilitated by a transponder function in the rover communication software). Approximate determination of rover position will require several orbital passes, and positional accuracy will improve with time-on-site. Once located, maintaining knowledge of rover position is fairly simple, due to the low speed of the rovers across the Martian surface. Another advantage of this approach is that the complex calculations are done on earth, hence the location function has minimal impact on the computational and energy budgets of the rovers and relay satellites.

When you find yourself on the side of the majority it is time to reform. -- Mark Twain