DARPA envisions growing structures hundreds of metres longScience Photo Library / Alamy Stock PhotoThe US military is brainstorming ways to build large structures in space, from telescope antennas to elevator tethers. By growing these objects in microgravity using biological organisms, they hope to avoid the costly and painstaking process of launching components from Earth.We have yet to unlock the potential of biology for space production and manufacturing, says Michael Nayak, program manager for the US Defense Advanced Research Projects Agency (DARPA). The combination of biology and mechanical engineering could unlock new ways to manufacture at unprecedented