Our hackathon group discussed interstellar communications. The group was Robert Freeland, Nathan Morrison, Lukas Schrenk, Bruno Doussau, Matt Johnson and Larry Papincak. We used an example of a ship at Alpha Centauri communicating back to Earth. The specific details were provided by Robert Freeland, based on Project Icarus. Once the ship gets to Alpha Centauri we will want high bandwidth communications. After all the effort to get there, it has to pay off.
Using lasers to communicate over those long distances seemed like the obvious first choice. However that will be very difficult since the pointing precision needed is so high. Using radio frequency seems like the only viable approach.
This communications design by Peter Milne (and provided by Robert Freeland) requires a one kilometer diameter antenna at the Alpha Centauri end and a 40 kilometer diameter antenna at the Earth end. (See diagram below.)
We started by discussing how to build such a large antenna. Could the antenna be a mesh instead of a solid shell? Could the antenna be built in space, or constructed from materials extracted and refined in space? The idea of an array of smaller antennas was proposed, and we spent most of our time discussing that.
We did not reach conclusions, but we came up with some new ideas and asked more refined questions. It was an interesting discussion, I hope it continues.