The catcher is equipped with radar capable of detecting payloads 10 s before arrival, that is, 2000 m away. A signal from the radar is processed to locate the spot at which the payload will cross the catch area, and the net is manipulated into that position for interception. Having captured the payload, the net and reel assemblies (rigs) act to decelerate it from its incoming velocity of 200 m/s to 20 m/s. The payload is then released into a storage depot and the rigs return to their original position by means of the closed loop tracks. The estimated cycle time is 60 s.
With 60 such rigs on a single catcher, it can catch 0.32 X 10^6 t/yr on a 100 percent duty cycle. In order to catch 11 X 10^6 t in 10 yr, 3.5 catchers on the average have to be operational at all times, each catching from a separate stream of payloads shot from the same mass driver. The installation of 5 catchers at L2 provides adequate margin for downtime for maintenance.
The time history of a payload and the rigs is shown in a two-dimensional representation in figure 5-29 and is detailed as follows: The payload enters the catcher area with a velocity v = 200 m/s where it is decelerated constantly by 30 m/s^2. When its velocity reaches 20 m/s it is released to a storage depot attached to the rear end of the catcher frame. The reel assemblies and net motions are divided into three stages:
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