Communication

Poul Anderson imagines:

practical applications of a technology that might never exist;

the practical problem of communicating with a newly discovered intelligent species on urgent matters like "We need a lift outta here rapido and can pay muchly!" 

Hyperdrive vibrations are instantaneously detectable at about a light-year. Van Rijn's yacht, the Hebe G.B., has uncommonly sensitive detectors and therefore spots an alien ship before being spotted. She accelerates to intercept and the alien tries to flee but not toward Adderkops. Deductions: the aliens are not Adderkops and have reason to fear strangers.

The alien goes off hyperdrive, thus becoming a no longer detectable small object in a vast spatial volume. However, knowing both the superlight vector and the instant of cut-off, the Hebe G.B. has a good idea where to look and adopts a search pattern, regularly reverting to normal space to sample neutrinos. By statistical analysis, the computer differentiates a small close neutrino source from stellar sources. The alien craft is found.

Van Rijn wants his crew to communicate and to develop a common language fast so that they can conduct urgent business. Communicating with new species has become routine and they will devise a simplified common language rather than try to learn each other's.