The space is far less dangerous than in real life. Any block of rock starting from few kilometers of radius have air. In the vacuum of the space there is no air, but no deadly cosmic rays or extreme temperatures. Relativity never comes to play. When leaving for a space walk there is no need for decompressions to avoid risk of aneurysms… Besides, character are all trained to work in such environments, so no nausea or vertigo will happen.
Just like fighting monsters non-stops does not give long term problems to characters we take lots of artistic licences because it is meant to be fun.
Sci-Fi and Fantasy often differs in term of Armor. In a “tipical fantasy inn” you can easily find a fighter in full plate and nobody beats an eye. Instead in Sci-Fi it would be extremely weird that a bunch of soldiers enter a bar in heavy bulletproof vests.
To compensate and help classes that depend on armors, we use this variant rule:
* Without armor or a shield, your character's AC equals 8 + his or her Proficency Bonus + his or her Dexterity modifier
As usual if you have multiple ways to compute your base Armor Class, you take the highest.
The gun is empty or the hero has no more arrows or bolts in his hands… The Reload Action is needed to make certain weapons able to shoot again. Weapons with this property have a number nearby the Reload property that shows how many times it is possible to attack before a Reload is needed. Of course, to actually reload the character needs the correct type of projectile (e.g., bullets, arrows, rounds, bolts…). Projectiles are not counted by shells, charges or rounds, but by how many rounds you can use the weapon at normal efficiency. To tone down Fantasy Ranged weapons, also bows and crossbow have the Reload property; basically it is how many arrows or bolt the hero can keep ready.
Since the game is equilibrated on the existing number of skills we cannot add more. However, we can add new effects to existing ones.
Religion now includes also Science and technology. So understanding a mysterious clockwork would be Knowledge Religion. Arcana is renamed “Magic” to make more clear that is about “lore about spells, magic items, eldritch symbols, magical traditions, the planes of existence, and the inhabitants of those planes.”
“Animal” is now in a extended sense, constructs with AI can be considered animals and to try to handle them use the same skill.
Medicine is also now more general, from the mechanics of human bodies to mechanics of complex clockwork this skill can help fix them all.
Here are the monsters types and how the four knowledge skills maps to them. The list is not mandatory, it is just meant to help masters as a quick reference. It is possible to play around with different skills, for example a Wizard may get information about a Magical Plant using Knowledge Arcana; possibly with an increased difficulty class.
History does not appear in any as it is actually a catch-all. If any creature type had a significant historical effect on the settings then it is a good candidate to learn about it using Knowledge (History).
Constructs are under Religion as Knowledge Religion in space operas also includes technology.
We consider the environments to have normal, heavy, light or no gravity. Usually no gravity is used for spaceship of when characters are in a very small planet. Heavy for large planets and light for small compared to Earth.
Normal gravity. No special rules needed.
Light gravity. Advantage in Athletics and Acrobatics. All the rules around weights consider weights halved, all weapon ranges and jumps heights are doubled, and falling damage is halved. Lots of terrains that are normally considered difficult do not slow down.
Heavy gravity. Disadvantage in Athletics and Acrobatics. All the rules around weights consider weights doubled, all weapon ranges and jumps heights are halved. and falling damage is doubled. Most terrains are difficult.
No gravity. Most Athletics and Acrobatics checks are automatic successes. All weights are zero, but beware of the difference between mass and weight, some checks might be still needed. For example, a large boulder is floating slowly, but steadily, toward the control panel. Krusk wants to deviate its trajectory, so he goes with a Strength (Athletics) Skill Check. All weapon ranges are quadrupled (it is impossible to keep precise shoots longer). Movement follows the following rules.
Interstellar distance is huge in real life. In our settings the distances are similar, but the TecnoMagic invented ways to traverse the void of space at unreal speeds. The distance between systems is usually measured in “HyperSpace days” that basically means how long one has to travel on the hyperspace to be nearby the destination. Two nearby stars are usually distant around seven–eight HyperSpace days. Similarly the distance between planets in the same system is usually in “Space days.”
Normal space travel. Used to leave planets, around destinations, or to move between planets in the same system. Slow, but perfectly precise, it is able to put someone exactly where it needs to.
HyperSpace travel. To move in the HyperSpace is not simply going very fast. HyperSpace is another dimension where any point in the HyperSpace maps with one on the regular space. However this mapping is not straightforward, so a body in one dimension is actually scattered in the other.
It is critical to compute the HyperSpace travel correctly (normal space ship computers can do it in few minutes) to avoid to have the travel finishing with the ship scattered in tiny fragments or with missing parts.
For this reasons HyperSpace travels start and finish at least from a distance of three–six Space days from a system.
Wormhole travel. The industrial use of kind of travel is just theoretical, but it may happen naturally and there is at least one recorded and verified case where one small ship did manage to arrive from one border of the universe to the center in just 16 days.