The Mission Design Center at NASA Ames has published an online tool to perform preliminary analysis of deep space missions to a celestial body.
“The Trajectory Browser website is best used as a first-cut tool to assess the existence of trajectories to small bodies and planets and provide ball-park values on launch date, duration and trajectory requirements,” said Cyrus Foster, an aerospace engineer at the NASA Ames Mission Design Center and lead developer of the Trajectory Browser.
Trajectory Browser allows a user to specify a particular destination or a class of destinations, such as all asteroids of a given magnitude. Plug in constraints such as maximum duration and ΔV, launch window, and fly-by or rendezvous, and click Search. The program turns up a list of potential trajectories, optimized for either ΔV or duration.
Try it yourself at http://trajbrowser.arc.nasa.gov/index.php. Below, graphical results for a sample return mission to an asteroid larger than1 km.