When health is depleted a "capture" bar shows, and when full the town will be conquered.

It took the astronauts three full days to attach the capture bar to the satellite, a relatively simple task for which they had two years to prepare.

"We have lots of experience of building equipment like this," referring to the capture bar.

But they said the 15-foot capture bar fell victim to the limits of knowledge about how to work in the weightlessness of space.

Two astronauts could steady the satellite while a third put on the capture bar, he said.

Three of the shuttle astronauts successfully captured the satellite by hand on May 14, 1992, after several failed attempts using a capture bar.

Any attackers who enter the building (even if it is currently being liberated) start the capture bar moving up again.

Unfolded, it becomes a capture bar that can be attached with built-in suction cups to any white board or other flat writing surface.

Markers or a special eraser are inserted into jackets that communicate with the capture bar using infrared and ultrasound.

With the satellite motionless, the astronauts installed the balky capture bar, which was then grabbed by the shuttle's 50-foot robot arm.