Technology of the Firmament

The technology of the Firmament is advanced by 21st century standards, but still has a lot of limitations. It’s also very limited outside of the core Foundation worlds. Some examples of the kind of technology available include:

• Large fusion generators; the size of a small building, or miniaturised versions small enough to fit into a starship. They are powered by Helium-3, which is most commonly harvested from gas giants.
• Costly but feasible creation of starships that can reach significant percentages of the speed of light.
• Costly metadimensional technology, including the spike drive and stealth system. Not cheap enough to enable interstellar trade of anything but exotic goods. Bottlenecked by rare elements.
• Antigravity technology, most commonly found as a bulky module in starships and space stations. Also used to make vehicles hover, but can only make very light things fly.
• Robots and complex machinery, including heavily automated processing plants and factories.
• Advanced computing technology, including expert and autonomous systems - but not true AI. The datapad in your pocket is as powerful as a cutting-edge 21st century computer. The terminal on your desk is a supercomputer.
• Clunky and obvious cybernetic prosthetics, like limbs or eyes. A wide variety of cyberware and bioware, though the brain is still largely off-limits.
• Brain-computer interfaces, usually using electrodes. Sensory recordings and full immersion into VR environments is feasible, but “skill chips” and technology to modify or copy the human brain is not.
• Hypersleep technology, requiring costly gases but making it possible to enter suspended animation for centuries.
• Limited organ, limb and tissue cloning. Also, limited genetic manipulation of human and alien life - though usually with difficult-to-predict side effects.
• Longevity treatments exist, but dementia is inevitable. Few people remain mentally healthy for more than 200 years, and most die before 300 even with the treatments.
• Force field technology, which is very expensive and almost as power-hungry as a starship. Requires bulky projectors the size of a small building.
• Laser weaponry, which is expensive but feasible as a high-end alternative to kinetic weapons.
• Limited terraforming, mostly using fusion-powered machines to slowly alter a planet’s atmosphere over the course of several decades.

A note on planet killers:

Any society which can accelerate to significant proportions of the speed of light has the ability to create weapons of unavoidable interplanetary destruction. However, this is not fun if you want to have a sci-fi setting where starships aren’t treated as portable WMDs. Relativistic projectiles fired at interplanetary distances are thwarted by the “braker gun”. Usually installed on a moon or orbital station, these enormous emplacements use antigravity technology to nudge relativistic projectiles off their course.

Other forms of WMD are dealt with by a planet’s defensive arrays. Orbital nuclear strikes and kinetic bombardment are trivial to defeat as long as the planet’s defenses are intact - railguns, lasers, missiles, et cetera. Generally speaking, battles for a planet are fought in orbit. Once you’ve overwhelmed a planet’s defenses, the only thing stopping you from scorching the surface with nukes is whatever desire you may have for it to remain inhabitable.

If you’re in the atmosphere, it’s harder to stop you from launching nukes at random. Planetary defenses will be able to shoot down intercontinental missiles, but short-range nukes may get through. There are various precautions to stop this from happening - for example, spacecraft approaching large cities are required to surrender their controls for landing once they get within a few kilometers. Needless to say, nukes and other WMDs are strictly military weaponry that generally aren’t available to the player characters - through legitimate channels, anyway.

Of course, none of this applies to uninhabited worlds, or planets so impoverished that they can’t afford to properly defend themselves. Out on the Rim, anything goes.