  The design of mission scenarios for the flyby investigation of nearby star
systems by probes launched using directed energy is addressed. Multiple probes
are launched with a fixed launch infrastructure, and download of scientific
data occurs following target encounter and data collection. Assuming the
primary goal is to reliably recover a larger volume of collected scientific
data with a smaller data latency (elapsed time from launch to complete recovery
of the data), it is shown that there is an efficient frontier where volume
cannot be increased for a given latency and latency cannot be reduced for a
given volume. For each probe launch, increasing the volume along this frontier
is achieved by increasing the probe mass, which results in a reduced probe
speed. Thus choosing the highest feasible probe speed generally does not
achieve an efficient tradeoff of volume and latency. Along this frontier the
total distance traveled to the completion of data download does not vary
significantly, implying that the download time duration is approximately a
fixed fraction of the launch-to-target transit time. Due to longer propulsion
duration when probe mass is increased, increasing data volume incurs a cost in
the total launch energy expended, but with favorable economies of scale. An
important characteristic of any probe technology is the scaling law that
relates probe mass to transmit data rate, as this affects details of the
efficient frontier.
