Allocating Tasks 2
In recognition of the value to science of having astronaut geologists walking on the lunar surface and directly observing the rocks and landscape, most tasks were mandated to be done as EVAs in the second study. The sponsors instructed us that, for purposes of this study, the pressurized vehicle would not have a robotic arm, and therefore no IVAs would be possible. Further, the UPR in this study would be equipped only for drilling core samples. However, safety was still given foremost priority, and so the objective function remained minimizing EVA time.
Instead of traveling to Science Zone 2 while the astronauts drove to Science Zone 1 as in the first study, the UPR in this study would simply follow the astronauts to each of the two science zones, drastically reducing the need for the Earth-based teleoperators to painstakingly keep the robot from running into trouble. The astronauts would perform the geological surveys that are needed to determine where to collect the core samples, and would place marker beacons on the lunar surface to tell the UPR where to set up its drill. Without the need to find its own drilling locations, the time required for UPR drilling was dramatically reduced to equal the 1.75 hours the astronauts would require, working EVA, to perform the same task. (As in the first study, the parameter values in this study have not yet been validated by independent peer review.)
Other parameters were changed as well. Total allowable astronaut work time was reduced to 15 hours, of which no more than 8 could be EVA. And the astronauts would no longer be allowed to multitask. Unlike the first scenario, they would not be able to set up the core-drilling operation, leave it to operate while they performed other tasks, and then return to it for completion.
This study compared a scenario in which the astronauts perform all tasks with a scenario in which the UPR conducts the core-drilling activity at both science zones and carries the cores back to the habitat for the astronauts to unload. While the study simplified many aspects of the mission, it also introduced one area of complexity: temporal dependencies. The UPR could not drill until after the astronauts placed their marker beacons. The astronauts could not unload the core samples until both the astronauts and the UPR had returned to the habitat. For the first time, the planner would need to synchronize schedules.
The results were displayed as a timeline, a portion of which appears below.
Portion of the timeline of astronaut and robot activities. "FRED" was the term used for the SPR at the time of this study.
The second scenario was found to save 1.9 hours of EVA time if the astronauts unload the core samples during the same day, and 3.2 hours of EVA time if the astronauts unload the core samples as the first activity of the next day (1.3 hours of unloading time would be on lien for the next day). However, two gaps appeared in the UPR's timeline, during which it had to stand by and wait for the astronauts to catch up. It was calculated to consume 400 W during this idle time, an undesirable waste of power.
For more information, contact Charles Weisbin at Charles.R.Weisbin@jpl.nasa.gov