There are two near term technologies which could be applied to making Death Star sized structures:
1. Space bubbles
2. Robotic spiderfab construction
Giant Space Bubbles
Bubbles on earth have been made that cover a rectangular 11 meter-by-7.5 meter area.
In 2007 Devon Crowe of PSI corporation created a study for NASA Advanced Innovative conceps for making large space structures from bubbles that are made rigid using metals or UV curing
A single bubble can be 10 meters in earth gravity, 100 kilometer in low earth orbit or 1000 kilometers in deep space. Foams made of many bubbles could be far larger in size.
A 140 kilometer diameter sphere would have 61600 square kilometers of surface area. If a structure could be made that was one gram per square meter, then that bubble sphere would be 61600 tons.
Reusable Spacex falcon heavy launchers could bring up the material to expand a large bubble in space. It would take about 2000 launches of a Spacex Falcon heavy to place the amount of material in orbit for a 140 kilometer sphere if the mass budget of one gram per square meter could be maintained. Every additional gram per square meter would be another 2000 launches
The size of a 1000 kilometer bubble is nearly the size of Charon, the moon of Pluto. Charon is 1200 kilometers in diameter. Saturn's moon Tethys is 1050-1080 kilometers in diameter Ceres the largest object in the asteroid belt is 970 kilometers in diameter. A single tesselation foam (like in the picture) of 1000 kilometer bubbles would be about the size of Earth's moon. A Penrose tesselation like the one in the picture of 1000 kilometer bubbles would be in between the size of Neptune or Saturn. A Tesselation foam of 100 kilometer bubbles in earth orbit could form an object the size our existing moon or larger.
A tesselation of many bubbles would make a large death star size structure that would be more resilient than the movie Death Star. The Death Star was destroyed with one well placed shot. Thousands of bubbles would need thousands of shots to destroy. Very low pressure or no pressure inside bubbles would mean that bubbles would not pop with a hole.
Metal can be evaporated to coat the inside of the bubble for reflective sails and telescopes. A reflective giant space bubble could be used to focus sunlight into a beam.
Russian theorists had proposed solar reflector systems that could constantly illuminate areas the size of several cities every night. The most ambitious proposal foresees a constellation of 100 reflectors, each 1,300 feet in diameter with a surface area of 30 acres.
The Nazi considered making giant mirrors to heat cities to several hundred degrees.
On Orbit Construction
NASA had funded studies and small demonstrations of SpiderFab which would robotic construction of Kilometer-Scale Apertures
Improving and testing reliability and a lot of engineering should be able to get us to 100 kilometer structures.
Again reusable rockets could bring down the cost of materials
Making 6U cubesat trusselator to put out 50 meter trusses and make truss of trusses from several
They are using Baxter robot to work with trusselators.
Firmamentum, a division of Tethers Unlimited, Inc. (TUI), announced that it has signed a contract with Space Systems Loral (SSL), a leading provider of innovative satellites and spacecraft systems, to prepare a flight demonstration of in-space manufacture of a component on a communications satellite. Firmamentum’s in-space manufacturing hardware is intended to fly as part of SSL’s “Dragonfly” program, which will demonstrate in-space robotic assembly of geostationary (GEO) communications satellites, enabling dramatic improvements in GEO satellite performance and mission flexibility. The Dragonfly program is funded under NASA’s Space Technology Mission Directorate’s (STMD) Tipping Point initiative to work with industry to advance the goals for robotic and human exploration of the solar system through the development of critical space technologies.
Firmamentum’s demonstration will validate a technology for on-orbit additive manufacturing of carbon-fiber composite structures. This technology, called the “Trusselator”, enables space systems to fabricate large, lightweight, and high-performance truss structures to support antennas, sensors, solar arrays, and other key components. Manufacturing the structure after the satellite has reached orbit allows these components to be significantly larger than if they had to be stowed within a rocket shroud. Increasing the size of these key elements of a satellite enables higher data throughput, higher resolution, higher sensitivity, and higher power than achievable by satellites manufactured entirely on the ground
In May, 2016, Firmamentum, a division of Tethers Unlimited, Inc. (TUI) dedicated to developing in-space manufacturing and construction services, announced that had signed a contract with DARPA to design a persistent geostationary orbit (GEO) satellite platform. Under the “Constructable™ Platform” Small Business Innovation Research (SBIR) award, Firmamentum will collaborate with Space Systems Loral (SSL), NanoRacks LLC, and Vulcan Aerospace to develop a modular architecture for constructing stations in Earth orbit capable of supporting multiple government and commercial payloads. Firmamentum’s Constructable approach entails launching suitcase-sized modular elements at low cost using DARPA’s PODS payload delivery system and then robotically assembling these modules to form a space station in GEO capable of providing power, communications, stationkeeping, and other key services to ‘tenant’ payloads. Firmamentum’s technologies for manufacturing satellite components such as trusses and reflectors on-orbit will enable integration of these small modules to form large, stable platforms that can grow and evolve to meet the needs of many different payloads over multiple decades of operation.
SOURCES- Firmamentum, NASA, NIAC, Star Wars