How is energy transferred so that HERCULES can travel? How do communities face change? Objective The learner will virtually explore the layout of the historic 1907 tugboat and predict how it was powered. Preparation 1. Print worksheets. 2. Obtain class set of laptops or tablets which can support Google Play or Apple App Store apps. 3. Download San Francisco Maritime Time Looper Xplore App for student use during class. Materials Brief activity to compare different explanations for how Hercules was powered and justify decision. Download Science Probe Comprehensive curriculum for 14-lesson Hercul Duration: 60 Minutes.