Complex sentence: Once they were stationkeeping alongside, they were given permission for their EVA, but they were tired and Stafford did not want to waste fuel keeping himself near the ATDA during the EVA when there was little they could do with it.
Split into simpler sentences: Once they were stationkeeping alongside, they were given permission for their EVA. But they were tired and Stafford did not want to waste fuel keeping himself near the ATDA during the EVA when there was little they could do with it.