Tech levels are a standard way (probably first used by Traveller) to keep track of the type of technology available in a setting. Traveller has many different worlds, each at different levels of technology, from worlds where society is still banging rocks together, to huge orbital colonies and floating cities in the clouds.
The technology of Traveller is based on the science fiction of the 1970s, and even future tech feels a bit behind the times. The technology level scale that I use is based on the SciFi rules for Yags, which is a modernised view of things, but still keeping to a reign on the level of automation and singularity-type of technologies.
Everything up to TL 8 is similar to the GURPS TL scale - TL 8 is modern day (1980 - 2020), and all lower scales are prior to this. See the Yags Historical notes for details, or lowtech for notes on trade and societies at these tech levels.
The tech levels here make references to the Kardashev Scale.
Type I (TL 10) - At this level, a civilisation has achieved mastery of the resources of its home planet. Most civilised worlds have achieved this level.
Type II (TL 20) - At this level, has harnessed the energy of their entire solar system. The Imperium (at TL 16) has not yet achieved this, though the Ancients did.
Type III (TL 30) - Achieved mastery of the resources of an entire galaxy. As far as anyone knows, no civilisation has managed this, and people would probably have noticed if they had.
The following technology descriptions describe the Third Imperium. Other cultures have varied slightly in how they progressed with technology.
TL 9 is deliberately kept as a buffer zone between the modern day and high science, so there is nothing in here which isn't pretty conservative. This means no jump drives, no anti-gravity and even a restriction on pretty much anything other than chemical slug throwers for weapons.
What it does have is increased power storage (smart devices of the future will need oodles of battery power), improved computers (to an extent - no AI and Moore's law is breaking) and a greater amount of networking, medical science and improvements on standard space drives (ion drives, plasma drives and the like, so that we can start exploring the solar system).
By TL 10 Moore's Law has run its course, and computer technology begins to stabilise. On the medical side, most diseases can be overcome, and the cloning of vital organs for transplants is cheap and routine. For the rich, life expectancy is well over a hundred, with most of that spent being fit and healthy.
Manned exploration of the solar system has become common place, and the colonisation of other worlds has begun, with some people living most of their lives in space.
Fusion power becomes the dominant source of energy, along with large amounts of renewable sources including solar and tidal. Beamed power is possible, though has limited use.
Man portable laser weapons are practical and common, mostly for sniper and battle rifles. Smart materials allow for practical full suited combat armour.
The biggest invention of TL 10 however is the jump drive, which becomes viable in the latter half of the period. It is big and bulky, and not as reliable as might be liked, but it opens up the stars for exploration.
Jump drives are still limited to Jump-1, but they become much smaller and reliable, making large scale colonisation possible. Better understanding of nuclear physics and quantum mechanics leads to the first tweaking of fundamental forces. Fully dial-a-yield micro-nukes become available, as well as the ability to suppress such nuclear reactions through the use of nuclear damper fields.
Medical science greatly improves, and knowledge of cybernetics actually declines as people prefer biological enhancements to mechanical ones. For the wealthy, life spans can approach 200 years, and most diseases and injuries can be cured, either by genetic tampering or regrowing organs and limbs.
Another step forwards in stellar colonisation is the introduction of cold sleep capsules, which allow large numbers of people to be transported to new worlds cheaply.
Particle beams are the common weapon of starship combat, being able to deliver a greater punch than laser weapons, though at shorter ranges. Finally, computer technology has pretty much reached it's limits.
For in-system space travel, the Plasma Torch drive is invented, and combines high efficiency with high thrust.
The invention of the Jump-2 drive opens up far more possibilities for trade, colonisation and war. This was the height of technology achieved during the First Imperium, and wasn't surpassed until the Terran Confederation just before the Long Night.
As nuclear damper technology improves, so other ways to tweak the fundamental forces become understood. The most common applications are ways to generate directed gravitational fields, allowing for tractor and repulsor beams. The latter make flying cars possible and practical. It also starts to be used as a form of artificial gravity in star ships, and though it's more pleasant than zero gravity it's still not as good as the real thing.
On the energy front, a form of Cold Fusion becomes possible, though it is limited to generating micro-power in small devices since it doesn't scale in size. However, PDAs and other electronic tools make good use of it, with most power hungry devices capable of lasting weeks without external power.
In space warfare, particle beams continue to improve in capability, and the introduction of plasma weapons sees more effective ways to damage the new larger breed of warships.
It was the invention of the Jump-3 drive that gave Terrans the edge over the First Imperium, and this level of technology was seen only briefly before the fall into the Long Night. Improvements in repulsor technologies make hover vehicles a common sight, and greatly reduces the difficulties in getting into orbit. Beyond orbit, fusion drives become the de-facto means of propulsion, and plasma cannons give way to fusion beams.
Meanwhile, our conquering of the forces of nature continues, with the creation of Meson weapons, capable of ripping through ship armour as if it wasn't there. Meson screens soon follow, again based on manipulation of the fundamental forces of the universe.
Medical advances continue, though it is more the culmination of a steady stream of advances than any single breakthrough. Genetic manipulation means that everybody is beautiful, even the poor. Unhealthy lifestyles can be fixed with pills. Agriculture is dominated by genetically engineered crops which grow anywhere and can produce any texture or flavour desired. Real meat becomes a luxury across the Imperium.
AIs reach a point where they can act as personal assistants, though using such things is seen as a sign of poverty - anyone who is anyone would rather demonstrate that they can afford a real person to do such a job. Synthetic pets with programmed personalities are all the rage however. Synthetic humans would be outlawed if there were any truths to the rumours.
A new level of technology, a new breed of jump drives, capable of Jump-4. Technology reaches a point where Jump-2 drives become so compact and efficient that anything less isn't worth bothering with.
As if the forces of nature weren't enough, scientists turn their attention to the building blocks of matter, rebuilding them anew. So called Nu-Matter allows the creation of completely artificial materials with exotic properties, allowing new types of armour, textiles and machinery.
Finally, damper fields allow partial gravity nullification, inertial dampers and improved repulsor fields.
Though Jump-5 drives become possible, they are only stable for larger vessels so remain relatively rare. However, the array of deadly weapons such as fusion beams, anti-matter missiles and meson guns are now protected against with black globe shield generators.
There is rapid uptake in the use of anti-gravity and repulsor technology, especially in architecture. Coupled with exotic materials, cities consist of impossibly tall buildings linked by thin walkways which criss cross above the old ground hugging buildings below. Above them, float the estates of the nobility on islands of rock and glass.
Orbital habitats pack the space around many worlds, and streams of repulsor carts provide the transport of cargo and people to and from the planet's surface.
Explorations in the science of gravity and space-time enable the use of Gravity Pulse drives. Not quite reactionless, but the pure liberation of gravitational energy from matter enables a drive efficiency only dreamt of before. Not as powerful as a Plasma Torch, but over time it will come to dominate because of its efficiency advantages.
At the height of Imperial technology, Jump-6 drives become possible, and would seem to be the theoretical limit of technology. Like Jump-5 drives before them, they are limited to larger vessels. Experimentation with micro-jumps begins, though it is mostly impractical for general use. However, it can allow quick movement around a star system.
Improvements in Black Globe generators leads to White Globes, a more practical form of shields.
Cloning, and even brain taping, is possible, though such technology is generally outlawed within the Imperium. Effective immortality may be beneficial on a personal level, but it is believed that it will only lead to stagnation and decay across all of society.
This level of technology and beyond is only theorised by Imperium scientists. Jump drives become smaller and more efficient, and expansion in the use of micro-jumps.