From: root@mauve.demon.co.uk   
      
   Lex Spoon  wrote:   
   >>> How about a sort of four legged kangaroo transport truck, that jump up   
   >>> and down on the moon surface?   
   >>>   
   >>> A can imagine now, a truck with four pogo sticks. Perharps also with a   
   >>> little bit assistances with retro rockets.   
   >>>   
   >>> Jumping up and down has been a proved method on traveling on the moon.   
   >>> LOL!   
      
   > The programming is extremely challenging.  Otherwise walking and   
   > hopping have some nice improvements over rolling.  Imagine going down   
   > the highway and your car has the option to hop over someone instead of   
   > ramming into them.  Imagine if a pothole was nothing, and it took a   
   > 2-3 foot ditch before you got even close to worrying about it.   
      
   It's not only that, but it's also got problems energetically.   
      
   While there is no inherent reason you can't regeneratively recover   
   the energy from moving the legs, it's many orders of magnitude   
   more complex than a wheel.   
      
   A wheel only needs a simple bearing, and uses rotational symmetry   
   to generate the force to move the contact surface backwards and   
   forwards.   
      
   A leg needs multiple actuators all able to cycle at high rates, and   
   the ability to swing the leg rapidly and accurately and exert high   
   forces.   
      
   If the control system goes out on a wheel, then you carry on   
   going in the same direction.   
      
   If it goes out on a leg, you fall over pretty much immediately.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)