One of the biggest problems with interstellar space flight is that communication and power supply can become a problem. Some years ago I had an idea which I called "Energy Link", which would be able to solve the problem. The solution is very simple: The interstellar space craft has a manufacturing facility on board to manufacture satellites that are used to link back to Earth. During flight, in strategic locations, a satellite is dropped that communicates with satellites dropped earlier. Energy is transmitted by using microwaves, for instance. This way, not only communication could be maintained over vast distances, but also power supply in mid-space when there's no sun around. The satellites would be powered by the energy transmitted to them, or by internal power plants. Supporting vehicles transporting freight could travel to the remote craft and between satellites. If enough support vehicles exist, then a bucket-chain like system can be used, so that there's always one vehicle arriving when another is leaving. Such a system could also be used to establish or maintain space infrastructures.