Coronet

A coronet is a large laser emitter in close orbit of stars. To call them merely large is not quite accurate, as they are the largest contiguous structures produced by modern day civilizations. Such an expansive structure would make for a fine weapon, and have occasionally been used as such, but coronets are far more useful as civic infrastructure. A typical coronet has a throughput of billions of tonnes per year, accelerating this load to a glacial speed on the interstellar scale. Coronets beam a staggering amount of energy, far more than could be supplied by fusion power, to spacecraft. Coronet-powered vessels capture this energy on a kilometers-wide ultra-reflective sail. This pushes them forward much like the sea-faring sailing ships of old. Since starlight is essentially free, the only costs associated with this are the maintenance of the coronet itself.

The output of a coronet is measured in Gross Ergs, the amount of energy it takes to accelerate 1,000 tonnes by 1 standard gravity over 10 light minutes. The average ship fusion drive can output dozens or even hundreds of gross ergs over their journey (not limited to 10 light minutes since they carry their engines with them). Most vessels accelerating via a coronet will get about one or two gross ergs. The resulting speeds are on the order of 500 Km/s. To travel between the nearest stars at this speed means spending over a decade flying in transit (for stars about 8500 light minutes apart). Once arriving at their destinations, the almost always automated vessels will unfurl their sails and receive more energy from their destination's coronet, slowing them down.

Most sails are made of a special material called Gentle Brass which reflects over 99.9% of the light which hits it. However, its low melting point means that there is a limit to how much energy a coronet can send to a vessel. While the coronet structure itself enjoys state-of-the-art cooling systems, most ships cannot afford to lug around heavy cooling equipment. Thus, the maximum amount of energy is typically 8 to 10 Gross Ergs, reaching a top speed of 5000 Km/s. This cuts down the trip to a year. Some high-priority but non-perishable goods get this expedited travel time.

Companies are the largest buyer of Coronet Time. Queues for shipping resources via coronet can be years long, but the cost savings compared to loading up a fusion vessel is immense. Very few people will waste years of their life traveling via coronet when fusion drives offer far faster interstellar transit, but it is not unheard of.

The oldest continually-operating coronets are either around Matoehdahn in Aylathiya or Andekai in Florathel. Since these structures had been in use for as long as 7,000 years, their long history suggests that other stars once had coronets but since lost them. Currently there are two hundred and ten coronets in existence, with three under construction and one planned. The star with the highest number of coronets is Maea, whose ten coronets decelerate millions of tonnes of material each day.