Acknowledgments

We would like to thank Minh B. Do, Romeo Sanchez, Terry Zimmermam, Satish Kumar Thittamaranahalli, and Will Cushing for helpful discussions and feedback, Jussi Rintanen for help with the YKA planner, and Piergiorgio Bertoli for help with the MBP planner. This work was supported in part by NASA grants NCC2-1225 and NAG2-1461, the NSF grant IIS-0308139, the 2003 NASA RIACS SSRP, the ARCS Foundation, and an IBM faculty award.