The Tachyon Drive is a very renowned piece of technology, mostly used by the Commonwealth of United Economic Nations as a rather cheap and reliable form of faster-than-light travel. Being invented in the midst of Zythyn planetary colonization, it has since been mass-produced to fit all kinds of ships, from public transport to warships. The Tachyon Drive is also used for mass transport on Hyperlanes, and is constantly improved. These are what make Tachyon Drives still relevant, even far after its invention.
Tachyon Drives operate by creating an exotic matter field, which would be able to influence Tachyons. Small amounts of Tachyons would 'fall out' of Tachyonic Space, being caught by the exotic matter field. Catching Tachyons happens to be an exponential process, with the ship's speed doubling in short amounts of time.
As Tachyons were being captured, and the bubble would then change in a format which would allow for 'Tachyonic Sailing'. With Tachyonic Sailing, a craft could control its speed by strengthening or weakening the exotic matter field. The high energy of the Tachyons could easily push a craft in a desired direction, and accelerate it to near-FTL speeds.
As the craft approached the speed of light, Tachyons would speed it up faster and faster, until it slipped into Tachyonic Space and created a photonic boom. The craft would then hang in a semi-controllable state, with the ability to speed up or slow down the Tachyonic flow. AI was always used for this task, since its prediction algorithms allowed it to fine-tune speeds correctly. In order to slow and stop the craft, the exotic matter field around it would reverse, catching Tachyons from the opposite direction. The Tachyonic wind would then reverse, exponentially slowing the craft until the exotic matter field was shut down.
The 'speed' of the Tachyon Drive has increased heavily in history, with first iterations being purely STL (Slower than light). However, many new editions and high efficiency has been added to the technology, making it better and more versatile than ever. The maximum speed of the Tachyon Drive without Hyperlanes is displayed at 2.177 light years per hour, and about 7.62 light years per hour in Hyperlanes. To put this to scale, this means that an uninterrupted ship with the Tachyon Drive could cross the Via Lactea in approximately 5.6 years. Hyperlanes cut this time down to just 1.6 years.
The Tachyon Drive was first theorized by Zythyn scientists, during their adolescent pre-space age period. Execution of such a device would need exotic matter to create a field and capture Tachyons. This theory would be observed and often tested, with the most advanced scientific equipment that scientists could get. As soon as they confirmed the existence of Exotic Matter and Tachyons, it was only a matter of time before technology would allow for them to be stabilized.
On the day of the Tachyon Drive's invention, billions of Zythyns observed the first instance of FTL travel. With the Tachyon Drive being clunky and expensive back then, it cost a massive amount of funds to send even a small object faster than light. That did not matter too much to the population or scientists, since FTL travel was then proven to be completely possible. Over many decades, this got refined, until items of value were quickly sent over to the far reaches of the Saykyan System. FTL probes were also invented, but their signals still traveled at light speed. (This was eventually beaten when a Tachyon Drive became small enough to be stored on a probe, and therefore physical storage could come back to the Saykyan System at FTL speeds.)
In the years following the use of the Tachyon Drive, Zythyn engineering expanded it even further. This came to the point that manned ships could be fitted with the technology. In a global effort to increase colonization of the Saykyan System, the many Zythyn governments came together and funded this project. Seeing a future of heavily increased resource production, the efficiency of the new technology was immediately seen as a benefit. The Saykyan System soon developed much faster, and FTL soon became commonplace with colonists.
The Tachyon Drive would serve amazingly as an FTL device for centuries, allowing the Zythyns to form a planetary government and expand out to the cosmos. When the Commonwealth of United Economic Nations was formed by the LZF, the Tachyon Drive saw extended use for trade and the military. People could also attain the Tachyon Drive very easily, with it being open to the public at this point.
While these first iterations were fairly primitive in today's comparison, They were still groundbreaking for its time. The release of the Tachyon Drive brought it at 6 light years per year. The second major update to its technology in the 70s BCE brought it up to about 31 light years per year. Changes were very gradual and incremental, resulting in a slowly exponential growth. By the 2000s CE, the Tachyon Drive had advanced to about 400 light years per year. Further iterations by the year 4000 has made it fairly speedy, with special versions going up to 1,900 light years per year. This grew until its current limit, which places the Tachyon Drive at 19070 light years per year.
By the time in which the CUEN discovered the Confederacy of Borealis, the Warp Drive was a very fast technology, challenging that of the Tachyon Drive. Since both nations started out cordially, the CUEN decided to lend the CoB its Tachyon Drive technology, making Warp Drives and Tachyon Drives more or less reserved for all kinds of travel. The invention and wide use of Hyperlanes made traveling FTL much safer, and Tachyon Drives could safely overclock to very immense speeds. In the far future, by 70000 CE, Warp Drives were seen as slower and inefficient, since there were barely any ways to improve on them. They were now used as a cheap and broad way to get around. The limit for Tachyon Drives was also reached in the 70000s, when it plateaued the final time.
With technology advanced slower and breakthroughs become infrequent, the Tachyon Drive became all the more useful as the primary transportation source. Even at the invention of the Dimensional Drive, Tachyon Drives and Warp Drives remained relevant. This was because of their much lower cost, lesser complexity, and lower resource upkeep. However, the Tachyon Drive had reached its limit. It still took a lot of energy to maintain it at such high speeds, and it all leveled off.