Tractor And Pressor Beams

See:

Gadgets
James Blish On Poul Anderson IV
search result for Gantok (Scroll down) 

In Poul Anderson's "Margin of Profit":

the Borthudian frigate, Gantok, having matched phase with the merchant ship, Mercury, then issued a radio warning, seizes the Mercury with a tractor beam and pulls herself closer;

Mercury responds with a repellent pressor beam five times stronger than the Borthudian tractor;

Gantok is repulsed but returns and reapplies the tractor;

within Mercury, deckplate buckles and metal shears;

the pressor again repels Gantok;

van Rijn, piloting Mercury, pursues and applies both a tractor and a pressor, balances them, then changes phase;

the phase change does not sever the gravitic forces linking the ships because their masses remain unchanged but does render Gantok's weapons useless against Mercury unless the Borthudian pilot re-matches phase;

Mercury begins random phase variations;

when Gantok begins to accelerate away, van Rijn equalizes his beams, thus welding the ships together, then reverses, dragging Gantok with him;

varying the linkage to avoid being torn apart, he meanwhile shortens the distance between the two ships;

when an outer plate bursts, van Rijn hands control of Mercury to Torres and goes EVA for the repair job;

Gantok continues to spurt and fire at random but then stops because otherwise it will be torn apart first;

the Borthudian captain, Rentharik, returns to normal state, knowing that such an abrupt withdrawal will stress the linking force-beams enough to destroy both ships;

however, Mercury has a detector and an automatic cutoff to counteract this maneuver;

Torres narrowly avoids a collision, then holds Mercury where Gantok's weapons cannot be brought to bear;

any Borthudians attempting to board can be flicked away with a smaller pressor beam;

enveloping Gantok in her more powerful hyperfield, Mercury takes her prisoner to the nearest League base.

In "A Tragedy of Errors," Roan Tom, in the landed Firedrake, focuses a tractor beam on an attacking fighter aircraft, which tries unsuccessfully to escape, then pulls it down under nearby trees and holds it there. Next, he uses a combined tractor-pressor beam to clear away the undergrowth so that he can see the captured craft although it is concealed from above.

Both van Rijn and Tom think of themselves as fishing.