The Semantic Asteroids: FAQs

A list of questions and answers related to the semantic asteroids project. If you do not find your answer here you may contact us at

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Q: Why is this whole thing called semantic asteroids?

A: The term semantic associated to asteroids is certainly unusual. Here it refers to the nature of the database underlying the list of trajectories to asteroids. Its structure is based on semantic web technology that allows for an improved data visualization. More information on the SIMILE project of the MIT.

Q: How did you evaluate the trajectory delta v?

A: All the trajectories that are based on chemical propulsion account for one impulsive DV increment at each planet / asteroid and one in deep space at each trajectory leg. Thanks to our research on automated trajectory optimisation we could optimise a great number of trajctories by just "pressing a button". The objective function used was the sum of all DVs including the one at planet departure for chemical propelled trajectories.

Q: What asteroid ephemerides did you use?

A: The asteroid ephemerides used where taken from the Jet Propulsion Laboratories NEO web page. Each asteroid was considered to be in a perfectly keplerian orbit.

Q: I am looking for an asteroid, but it is not in your list. Why?

A: We included in our database only those transfers that have a total DV less than 6 km/s and to asetroids having a semi-major axis less than 2 AU. We calculate the trajectories to all asteroids, but as the database technology we use (SIMILE) is relying completely on the web browser to perform the calculations, we had to limit the trajectories to list.

Q: Can a spacecraft actually fly these trajectories?

A: The trajectories are good in preliminary mission design phases when little is known on the launcher that will be used and on the spacecraft design. The numbers provided are only an estimate of what the final trajectory could look like. A more detailed optimisation needs to account for the launcher capabilities as a constraint to meet and has to minimise the on board fuel consumption rather than the total DV.

Q: The total delta V looks good but the launch delta V looks too small!

A: The results we are reporting fpr the chemical propulsion trajectories, are globally optimal with respect to the total delta V. You can still fly a similar trajectory using more of the launcher chemical propulsion energy, in this case the total delta V would increase, but you the on board propellant mass can decrease.

Q: The launch year is not suiting my needs. Can I obtain the same trajectory launching in another time frame?

A: No. The trajectories listed have been obtained by solving a global optimisation problem where the launch date was constrained to be in [2013 2020]. Thus the launch year refers to the globally optimal trajectory and changing it would result in a trajectory with more total DV. On the other hand one can use the total DV information without referring it to any particular date as a 'measure' of the asteroid distance.

Q: What is coming next?

A: We plan to extend incrementally this database including different fly-by sequences and direct transfers with low-thrust engines.