Solar System: Sun to Outer Rim Territories is a science-fiction universe that takes place entirely in Earth's solar system like Alternate Earth and the Local Solar System and Void of Earth's Solar System 
THE INNER WORLDS The Inner Worlds of Solar System: Sun to Outer Rim Territories refers to the planets Mercury, Venus, Earth, and Mars; Earth's moon Luna, and the Inner Belt (the asteroid belt between Mars and Jupiter orbits) Venus and Mars were terraformed to Earth-like conditions hundreds of years ago. The governments of Earth, Luna, Mercury, Venus, and Mars are all one-world regimes and democratic republics. Each of these five worlds is governed by a popularly elected Senate, each of which divides into Legislative, Executive, and Judicial Councils to execute the functions of government. Each of these five worlds has a multiparty system, including Industralist, Federalist, Technologist, Universalist, Populist, War, Pacifist, and Mercantile Parties.  The asteroid belt is governed by the Belt Mining and Merchant Guild, which is headquartered on the dwarf planet Ceres. Virtually all permanent inhaitants of the asteroid belt join this guild, which is governed as an oligarchy is it is governed by a Guildmeister and Guild Council elected with wealthier guildmembers having as many as 10,000 votes each for Guildneister and the Guild Council, guildmembers with medium income having one or two votes each for Guildmeister and the Guild Council, and the lowest-income members, who have as little as a tenth of a vote each for Guildmeister and council. The Belt Mining and Merchant Guild is based upon asteroid mining and interplanetary trading (mostly in metals and minerals, but sometimes other stuff, too).
THE MIDDLE WORLDS This refers to the gas giant planets Jupiter, Saturn, and Uranus; and their moons. Jupiter's moons have their own mining industry, and there is are gambling enclaves on Jupiter's moons Callisto and Ganymede, Saturn's moon Tethys, and Uranus's moons Titania and Oberon. The atmospheres of the gas giant planets are used (with smaller special spaceplanes used to collect and process fuel) to refuel interplanetary ships with fusion-powered nuclear-pulse drives. The governments and private corporations of the Inner Worlds control the mining colonies and gambling enclaves, though the Belt Mining and Merchant Guild based in the asteroid belt does have a few mining operations in the Middle Worlds.
THE OUTER RIM TERRITORIES This refers to the gas giant planet Neptune, Neptune's moons, and the comets, ice-and-rock asteroids, dwarf planets, and any moons of dwarf planets in the distant Kuiper Belt  and Oort Cloud  Neptune's atmosphere, like that of the gas giants in Middle Worlds space, is used for refueling interplanetary spaceships. Earth has Neptune's moon Triton as it's main colony in the Outer Rim Territories. Luna, Mercury, Mars, and Venus have their own colonies on other moons of Neptune. The dwarf planet Pluto and it's moon Charon for the past two centuries have been the self-governing Plutonian Commonwealth, which is economically based upon Kuiper Belt mining and gambling. The Commonwealth's government is an aristocracy with political rule by a Plutonian Senate with hereditary membership. The countless billions of comets and ice-and-rock asteroids in the Kuiper Belt and Oort Cloud are targeted for mining for metals, minerals, and ice (as a source of water). The Belt Mining and Merchant Guild ruling the Inner Worlds' asteroid belt has in recent decades become a lot more active in the Kuiper Belt and Oort Cloud as a source of profit. It's home base in the Outer Rim Territories is the ice-and-rock dwarf planet Sedna. . There are also dozens of Outer Rim Free States that are essentially small, self-governing nations whose relations with the Inner Worlds' colonies, the Belt Mining and Merchant Guild, the Plutonian Commonwealth, and each other range from friendly (including free trade) to hostile (the Free States are a leading source of space piracy). Shooting wars out here are sometimes fairly common.
SPACESHIPS Spaceships traveling over interplanetary distances use nuclear-pulse drives , especially the use of nuclear-fusion drives . A few older-model interplanetary ships with nuclear-pulse drives use nuclear-fission drive . Some spaceships designed for interplanetary flight in Inner Worlds space only rely on various types of space sails . The large interplanetary ships rely on rotating sections  to provide onboard areas with artificial gravity and use smaller spaceplanes  to shuttle crew, passengers, and cargo to their destinations or from their origins.
WEAPONS & WARFARE On occasion, two or more worlds in the Inner Worlds will go to war with each other. Generally, this means combate between spaceships including chemical-thrust-powered missiles, electromagnetic rail guns shooting metal projectiles, and laser- and particle-beam-powered energy guns. Sometimes, space marines will board enemy spaceships armed with slug-throwing firearms. Warfare in the asteroid belt is almost invariably between the Belt Mining and Merchant Guild and local space pirates. Warfare in the Middle Worlds and the Outer Rim Territories can be between almost any faction.
SPACE PIRACY Space pirates are a perennial problem in the asteroid belt, Middle Worlds, and Outer Rim Territory as some people decide to prey on others for an economic living. Space pirates are of two general sources: the Outer Rim Free States and Inner Worlds military forces who turn rogue.