Gravity gradient torques can be countered by a reaction control system, but at a substantial propellant cost. As an alternative, the column/cable configuration can eliminate the short-period torque by means of about 10 kg of counterweights at the ends of the columns perpendicular to the array (fig. IV-11). Purely on a weight basis, the counterweights are roughly equivalent to a 30-year propellant supply if specific impulse is about 98 000 m/s (10 000 Ib-s/lb), assuming an array length/width ratio of 2. The long-period torque could be countered in a similar fashion by altering the length/width ratio, but the counterweight required is prohibitive (on the order of 7 x 10 kg). Orienting the long axis of the array perpendicular to the orbit plane (POP) eliminates the long-period torque at an annual average power loss of 4 percent; the weight of additional array required to make up the loss is much less than the propellant required. This is the preferred approach. Figure IV-11.- Counterweight location.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==