Electric current refers to streams of electrically charged particles moving past a specific place over a specific duration of time. Atomic current refers to streams of individual atoms delivered to a specific place during a specific time. As charge is the integral of electric current, mass is the integral of atomic current. Homogeneous atomic currents contain the same element exclusively; component streams deliver different atomic species. Nanotube injectors deliver atomic species in regular pattern pressured by atomic impellers. (Such pressure never exceeds any particular reaction energy required to overcome potential reaction barriers.) The pattern permits temporary condensed states that enable superior resolution at the injector.

The Project Von Neumann uses atomic currents to construct eutactic starships. These currents are directed to a somatic target by the injectors found on the deckgrowers. Though parallel currents of different elements are found in the design, generally speaking component streams are avoided since replicators can perform more complex operations more efficiently. The forces of injection and collision induce desired reactions at the target. The timing of ejected species involves coupling all related injector trajectories to somatic target energy to guarantee proper reactions. (Such computations are performed beforehand to serve the deckgrower control systems.)

The construction of the secondary hull commences upon seedshuttle deployment. Carbon and a few other elements preinstalled in the deckgrowers allows immediately work on the crew spaces found on decks seventeen through twenty. Source material is gathered from semi-eutactic feedstock currents. No elements smaller than carbon are used in construction, allowing a lower bound. The mass of a starship is 190000t. An optimum feedstock of solid diamond (3.5 gm/cm^3) would compress this mass to a 54E3 m^3 cube (about thirty-five meters on a side). Roughly a third of this is delivered initially with the seedshuttle.

When delivered by a starship or planetary launch, preformed supplies provide feed currents of additional mass. (Emergency lifeboat conditions involve severe restrictions of ontogeny not covered here.) To a first order approximation let's consider the boundaries of information required. At 12 g/mol that mass is roughly 10^34 atoms. For each it should be sufficient to establish a position to the angstrom, no more than 10^10^3 for three dimensions, for a design envelope of some 10^60 bits. (Somatic compression improves that total to the prototype seedshuttle genetics of 10^12 bits.) Not discussed for now remain issues of alterations to the genetic information, both intentional and mutation, along with error detection and correction schemes. Mutations and selection effects over generations may leave subsequent ships different from the original.