The excavation transport rate (ETR) is a new parameter we introduce that can represent the overall transportation and excavation efficiency of a hybrid mobility-excavation system. ETR is defined in Equation \ref{ETR}, where \(R_E\) is the excavation rate, \(m_c\) is the craft mass, and \(COT\) is the cost of transport.
\(\begin{equation} ETR = \frac{R_E}{m_c\cdot{}COT} \label{ETR} \end{equation}\)
    It should be noted that a higher value of ETR provides higher performance because more mass is being collected at a lower cost of transport. Figure \ref{328829} shows a clear trend that is consistent across all configurations, angular velocities, and load times. The ETR increases in a quasi-linear fashion with load time.  Interestingly, as the load time increases, the ETR appears to asymptotically approach a maximum value. A similar trend exists between ETR and angular velocity. Increasing the angular velocity from 20 to 30 RPM has a significantly larger increase in ETR than increasing it from 30 to 40 RPM in all cases. There does not appear to be a significant difference between the wide and narrow configurations C2 and C4, as both of these follow very similar trends and end up approaching the same maximum ETR values at each given ramp angle.
    Note that only the 45 degree cases have nonzero values for C1 and C3 because they were the only ones that had nonzero excavation rates. When comparing the inward/outward churning configurations, it is obvious that the inward churning configurations have significantly higher ETR values. This dramatic difference is illustrative of the fact that the inward churning configurations are more efficient for excavation than their outward churning counterparts while maintaining a similar cost of transport. Additionally, it is evident that increasing the ramp angle, load time, and RPM all lead to the most efficient configurations. Furthermore, for both of the outward churning configurations at the 40 and 45 degrees ramp angles, there does not appear to be a significant difference in ETR between the four and six second load time cases at 30 and 40 RPM. These would appear to be the most efficient configuration of all settings. In a space environment, one might opt for 30 RPM to be at peak efficiency with lower total power required. The lower angular velocity would provide a lower total power requirement, which in turn would lower the mass of the spacecraft. For terrestrial applications, it would be likely to favor the faster angular velocity which would maximize the excavation rate. Ultimately it appears that there is an optimum ETR value that can be achieved with many different configurations of load time, ramp angle, and angular velocity. 
    In general, it was found that the inward churning configurations C2 and C4 were able to collect significantly more mass at practically the same total power while traveling at the same or greater speeds in comparison to their outward churning counterparts C1 and C3 across all load times, ramp angles, and angular velocities.
    It was observed that the inward churning configurations created an elevated wake behind the front screws, directly in the path of the ramp. Conversely, the outward churning configurations diverted the sand away from the ramp, leaving a strip of undisturbed flat sand in front of the ramp. A detailed image of the wake patterns for each configuration is shown in Figure \ref{264239}. It is noteworthy that the length of the depression cut by the ramp is directly proportional to the independent variable, load time. Additionally, since the outward churning configurations did not have the elevated wake, the ramp angle needed to be 45 degrees to just barely make contact with the soil. As a result, C1 and C3 were only able to collect mass at the 45 degree ramp angle. Attempts were made to collect material at 35 and 40 degrees, but were unsuccessful. This phenomenon makes it evident that having the front screws churn material inward provided a significant benefit to act as an auxiliary mechanism for excavation. 
    In order to compare CASPER to other ISRU excavation systems, a table of characteristic values is presented in Table \ref{Performance}. Note that the presented values correspond to CASPER's optimal configuration of C2, 40 RPM, 45 degree ramp angle, and 4 second load time. A comprehensive performance comparison between many ISRU excavators was performed by Just et al. \cite{Just_2020} and the metrics reported in Table \ref{Performance} are the same as those used in that comparison.