A ship that takes cares of scrap. The way it works is once it has stored 1000 items of everything, it will discard additional items of that type. One constant combinator can be set to store additional items like holmium, battery, low density and Processing unit. It will stop requesting scrap when its buffer has reached the desired amount.
Mine directly into rocket silos and let this ship provide the additional holmium and batteries your base need. Its a stationary ship but it has some thrusters so that it can be built on other planets or move if it wants.