The hands and eyes of the near-human computers that ran the various vehicles on 
the expedition were embodied in a repair and maintenance motile used by the 
computer, popularly called the "Christmas Bush" because of the twinkling laser 
lights on the bushy multibranched structure. The bushlike shape for the robot has 
a parallel in the development of life forms on Earth. The first form of life on 
Earth was a worm. The stick-like shape was poorly adapted for manipulation or 
even locomotion. Then these stick-like animals then grew smaller sticks, called 
legs, and the animals could walk, although they were still poor at manipulation. 
Then the smaller sticks grew yet smaller sticks, and hands with manipulating 
fingers evolved.

 The Christmas Bush is a manifold extension of this idea. The motile has a 
six-"armed" main body that repeatedly hexfurcates into copies one-third the 
size of itself, finally ending up with millions of near-microscopic cilia. 
Each subsegment has a small amount of intelligence, but is mostly motor and 
communication system. The segments communicate with each other and transmit 
power down through the structure by means of light-emitting and 
light-collecting semiconductor diodes. It is the colored lasers sparkling 
from the various branches of the Christmas Bush that give the motile the 
appearance of a Christmas tree. The main computer in the spacecraft is the 
primary controller of the motile, communicating with the various portions 
of the Christmas Bush through color-coded laser beams. It takes a great 
deal of computational power to operate the many limbs of the Christmas 
Bush, but the built-in "reflex" intelligence in the various levels of 
segmentation lessen the load on the main computer.

 The Christmas Bush shown in Figure 8 is in its "one gee" form. Three of 
the "trunks" form "legs", one the "head", and two the "arms." The head 
portions are "bushed" out to give the detector diodes in the subbranches a 
three-dimensional view of the space around it. One arm ends with six 
"hands," demonstrating the manipulating capability of the Christmas Bush 
and its subportions. The other arm is in its maximally collapsed form. The 
six "limbs", being one-third the diameter of the trunk, can fit into a 
circle with the same diameter as the trunk, while the thirty-six 
"branches," being one-ninth the diameter of the trunk, also fit into the 
same circle. This is true all the way down to the sixty million cilia at 
the lowest level.

 An interesting property of the Christmas Bush is its ability to change 
size. Just as a human can go from a crouch to an arms outstretched position 
and change in height from less than one meter to almost three meters, the 
Christmas Bush can shrink or stretch by almost a factor of five, from a 
short, squat bush to a tall, slender tree.
 
 
 
 
 The "hands" of the Christmas Bush have capabilities that go way beyond 
that of the human hand. The Christmas Bush can stick a "hand" inside a 
delicate piece of equipment, and using its lasers as a light source and 
its detectors as eyes, rearrange the parts inside for a near 
instantaneous repair. The Christmas Bush also has the ability to detach 
portions of itself to make smaller motiles. These can walk up the walls 
and along the ceilings with the tiny cilia holding onto microscopic 
cracks in the surface. The smaller twigs on the Christmas Bush are 
capable of very rapid motion. In free fall, these rapidly beating twigs 
allow the motile to propel itself through the air. The speed of motion 
of the smaller cilia is rapid enough that the motiles can generate sound 
and thus can talk directly with the humans.

 Each astronaut in the crew has a small subtree or "imp" that stays with 
him or her to act as the communication link to the main computer. Most 
of the crew have the tiny imp ride on their shoulder, although some of 
the women prefer to keep theirs in their hairdo. In addition to acting 
as the communication link to the computer, the imps also act as health 
monitors and personal servants. They are the ideal solution to the 
perennial problem of spacesuits ... scratching an itchy nose.

 The imps go into the spacesuit with the humans, and more than one human 
life was saved by an imp detecting and repairing a suit failure or 
patching a leak. In fact, there are two computer motiles with each 
suited human. The personal one that stays with the human, and the 
spacesuit motile that stays with the suit. This motile is usually 
outside in the life-support backpack, but can worm its way inside 
through the air supply hose.