Working with Slava Turyshev and others on a new mission concept to reach the SDolar Gravity Lens Focus (>600 AU) and use it to image a potentially habitable exo-planet at high resolution.  Described in an award winning article.Finding Earth 2.0 at the Solar Gravity Lens Focus

Laser Sailing Demonstration Technology Assessment Study,  Keck Institute for Space Studies, Caltech Final Report  [pdf]

  Asteroid Redirect Mission, Co-Lead of Technical Development Project, Keck Institute for Space Studies, Caltech
http://www.kiss.caltech.edu/study/asteroid/technology.html

Currently consulting with JPL on the development of this mission

  Exploring the Interstellar Medium, Co-Leader of Study, Keck Institute for Space Studies, Caltech
Final report 

Human Spaceflight: From Mars to the Stars: author of book published by the University of Arizona Press — Nov 2015

Co-Inventor of the Living Interplanetary Flight Experiment now being studied by NASA for flight on the Asteroid Retrieval Mission
  http://www.planetary.org/explore/projects/life/