SPACE ENVIRONMENT & SCALE RULES

Starfinder 2nd Edition Compatible Supplement

Quick Reference Available: Space Environment Quick Reference

Rules for personal-scale encounters in space environments and interactions between different combat scales

TABLE OF CONTENTS

1. Vacuum & Decompression
2. Radiation Exposure
3. Gravity Effects
4. Atmospheric Hazards
5. Scale Interactions (Personal vs. Starship)
   • Spells and Starship Scale
6. Vehicle-Starship Interactions
7. Survival Equipment

VACUUM & DECOMPRESSION

Vacuum Exposure

Space is a hostile environment that can kill unprotected creatures in moments.

Immediate Effects

When a creature without environmental protection is exposed to vacuum:

1. Suffocation Begins Immediately
   • Creature can hold breath for rounds equal to Constitution modifier (minimum 1)
   • After that, creature begins dying (as suffocation rules)
2. Pressure Damage
   • Take 1d6 bludgeoning damage per round (no save)
   • This damage cannot be reduced by resistance or immunity
3. No Temperature Damage
   • Contrary to popular belief, vacuum has no effective temperature
   • Heat loss through radiation is slow; cold damage does not apply

Decompression

When a pressurized area suddenly loses atmosphere:

Immediate Damage: 3d6 bludgeoning damage to all creatures in the area

Decompression Pull:
All creatures must attempt a Reflex save (DC 18) or be pulled toward the breach.

Breach Sizes

Sealing a Breach

Crafting DC: Based on breach size (see above)
Time: 2 actions

Surviving Vacuum

Environmental Protection

The following provide protection from vacuum:

Running Out of Air

When environmental protection runs out:

1. Warning: Most systems provide 10-minute warning
2. Rationing: Can extend duration by 50% with DC 15 Survival check (must rest)
3. Sharing: Two creatures can share one suit's air at half duration each

RADIATION EXPOSURE

Radiation Levels

Exposure Frequency

Radiation Save Results

Fortitude Save vs. Radiation DC:

Radiation Sickness

Creatures who fail radiation saves accumulate radiation sickness:

• Stage 1 (1-2 failures): Sickened value persists for 1 day
• Stage 2 (3-4 failures): Sickened value persists for 1 week; Drained 1
• Stage 3 (5+ failures): Sickened value persists for 1 month; Drained 2; lose 1d4 HP per day

Treating Radiation

Medicine DC: 15 + (Radiation Level × 2)
Time: 1 hour

Radiation Protection

GRAVITY EFFECTS

Gravity Categories

Standard Gravity

Normal Earth-like gravity. No special rules.

Low Gravity (≤1/3 Standard)

Benefits:

• Jump distances tripled
• Carrying capacity doubled
• Thrown weapon ranges doubled
• +2 circumstance bonus to Athletics checks for jumping/climbing

Drawbacks:

• Ranged weapons: -2 to attacks beyond first range increment
• Acrobatics DC to land safely increased by 2

High Gravity (≥2× Standard)

Penalties:

• Speed reduced by half
• Jump distances halved
• Carrying capacity halved
• Thrown weapon ranges halved
• -2 circumstance penalty to Athletics checks
• Fatigued after 1 hour without rest (Fort DC 18 to resist)

Extreme Gravity (≥5× Standard)

All high gravity effects plus:

• Take 1d6 bludgeoning damage per round
• Prone creatures cannot stand without DC 20 Athletics check
• Flying creatures must land or fall

Zero Gravity

Movement:

• Cannot walk; must push off surfaces or use propulsion
• Move speed becomes "drift" speed (usually 10 feet)
• Can push off to move up to 30 feet in a straight line

Combat:

• Melee attacks: -2 circumstance penalty unless trained
• Ranged attacks: No penalty
• No flanking bonuses (no clear "ground")

Maneuvering:DC 18 to change direction or stop:

• Acrobatics: For fine adjustments, stopping, or controlled maneuvers
• Athletics: For pushing off surfaces or generating initial momentum

Carrying Capacity: ×10 (but inertia still applies)

Variable Gravity

Some locations have fluctuating gravity.

Gravity Shift (every 1d4 rounds):

• Roll 1d6: 1-2 = Low, 3-4 = Standard, 5 = High, 6 = Zero
• All creatures must succeed DC 15 Reflex or fall prone
• Unsecured objects drift/fall based on new gravity

Artificial Gravity

Most starships and stations have artificial gravity.

Gravity Generator Failure

When artificial gravity fails:

1. Immediate: Zero-G takes effect
2. Unsecured Objects: Begin floating
3. Liquids: Form floating spheres
4. Duration: Until repaired (Crafting DC 20, 10 minutes)

Gravity Manipulation

Some effects can locally alter gravity:

ATMOSPHERIC HAZARDS

Atmospheric Types

Thin Atmosphere

Insufficient oxygen for normal breathing.

Effects:

• Fortitude save (DC 15) every hour or become Fatigued
• Strenuous activity requires Fortitude save (DC 18) every 10 minutes
• Failed saves by 5+ cause Exhausted instead

Thick Atmosphere

Dense atmosphere that impedes movement and breathing.

Effects:

• Fortitude save (DC 15) every hour or become Sickened 1
• +4 to Piloting/flying checks (denser medium)
• Ranged weapons: -1 per range increment
• Fire damage reduced by 2 (harder to burn)

Corrosive Atmosphere

Atmosphere contains damaging chemicals.

Standard environmental seals protect against Mild and Moderate.

Toxic Atmosphere

Atmosphere contains poisonous gases.

Inhaled Poison (varies by atmosphere):

Fortitude DC: Low 15, Medium 20, High 25

Unbreathable Atmosphere

Cannot sustain humanoid life but not actively harmful.

Effects:

• Suffocation: Creature can hold breath for rounds equal to Constitution modifier (minimum 1), then begins dying
• No other effects (non-toxic, non-corrosive)
• Environmental protection required (breathing apparatus sufficient)

No Atmosphere

Vacuum conditions apply (see Vacuum & Decompression).

Environmental Extremes

Extreme Heat

Extreme Cold

SCALE INTERACTIONS

Personal vs. Starship Scale

When personal-scale creatures and starship-scale objects interact, use these conversion rules.

Distance Conversion

Personal Weapons vs. Starships

Personal weapons are not designed to damage starships.

General Rule: Personal weapons cannot damage starship systems or hull.

Exceptions:

• Weapons with the "starship-scale" property
• Weapons specifically designed for anti-vehicle use
• Magical effects that ignore physical limitations
• Attacking exposed crew or external components

Attacking Exposed Components: Some starship components (sensors, weapons, engines) may be targetable from the exterior.

Starship Weapons vs. People

Starship weapons are devastating against personal-scale targets.

Damage Conversion: Starship weapon damage × 10 = Personal damage

Example: A light laser cannon (2d4 starship damage) deals 20d4 damage to a person.

Targeting Limitations:

• Starship weapons cannot target individual creatures
• Must target a 50-foot area minimum
• All creatures in area take damage (Reflex DC 20 for half)

Starship Collision with Creatures

When a starship collides with a creature:

Creature Damage: 10d6 per starship speed
Starship Damage: None (unless creature is Gargantuan+)

Gargantuan+ Creatures:

• Deal damage equal to their level × 2 to the starship
• Take normal collision damage

Combat Scale Options

Close Combat Scale

For fights involving Medium and smaller ships at close range.

1 Hex = 200 feet

Effects:

• Personal-scale weapons can target exposed components
• Boarding is easier (DC -5)
• Tracking weapons less effective (-2)

Standard Scale

Default starship combat scale.

1 Hex = 1,000 feet (approximately)

Effects:

• Normal starship combat rules apply

Fleet Action Scale

For large battles with many ships.

1 Hex = 10 miles

Effects:

• Use Armada rules for large forces
• Individual ships represented by fleet markers
• Personal-scale completely abstracted

Mixed-Scale Encounters

When both personal and starship combat occur simultaneously:

Initiative

All combatants roll normally. Ships and creatures act in initiative order.

Action Timing

• 1 starship round = 1 personal round
• Crew actions occur during the ship's turn
• Personal combatants not crewing ships act normally

Targeting Across Scales

Personal → Starship:

• Can target exposed components
• Can attempt to board
• Cannot damage hull/systems with normal weapons

Starship → Personal:

• -10 to target individual creatures
• Area attacks work normally
• Collisions handled as above

Spells and Starship Scale

When spellcasters encounter starships, the differences in scale create significant limitations on magical effectiveness.

General Principles

Scale Mismatch: Most personal-scale spells are designed to affect creatures, small objects, or localized areas. Starships operate at a vastly larger scale where personal magic is generally ineffective.

Key Limitations:

1. Size: Starship components are too large for most targeted spells
2. Area: Spell areas of effect are minuscule compared to starship scale
3. Magnitude: Damage from personal spells is negligible against ship structures
4. Targeting: Many spells require creature targets, which starships are not

Design Principle: Spell effects do not automatically scale up. A fireball that devastates a room cannot meaningfully damage a starship's hull.

Spells That CAN Affect Starships

The following categories of spells can have meaningful effects on starships:

Structure/Object Targeting

Spells with explicit "structure" or "unattended object" targeting can affect starship components.

Limitation: Spell level must be sufficient for the component's size/complexity. Most starship components require high-rank spells.

Teleportation Magic

Teleportation spells work normally for moving creatures but cannot transport entire starships.

Note: Teleporting requires knowing or seeing the destination. Ship interiors are difficult to target blindly.

Buff/Debuff Magic

Spells affecting crew members work normally and can indirectly help ship performance.

Remember: Crew bonuses apply to their skill checks during ship actions, not to the ship's statistics directly.

Divination Spells

Information-gathering spells are particularly useful in starship encounters.

Spells That CANNOT Affect Starships

The following spell categories are ineffective against starship-scale targets:

Direct Damage Spells

Personal-scale damage magic cannot meaningfully harm starships.

Example: A 3rd-rank fireball (8d6 damage, ~28 average) cannot damage a starship with 100 HP and armor 10. The scale difference is absolute.

Single-Target Attack Spells

Most offensive spells require creature targets.

Cannot Target Starships:

• disintegrate (creature or object up to 10-ft cube)
• finger of death (creature only)
• phantasmal killer (creature only)
• harm (living creature or undead)

Why: Starships are neither creatures nor appropriately-sized objects for these spells.

Mind-Affecting Spells

Starships are objects without minds (unless sentient AI is involved).

Ineffective Against Ships:

• charm, dominate, suggestion
• confusion, fear, sleep
• detect thoughts, mindlink, telepathy

Exception: If a ship has a sentient AI system, mind-affecting spells might work on the AI (GM discretion).

Condition-Inflicting Spells

Most conditions (frightened, sickened, clumsy) apply only to creatures.

No Effect on Starships:

• Conditions cannot be applied to objects
• Ship status conditions (Glitching, Malfunctioning) are separate systems
• Use appropriate Engineering/Piloting actions instead

Spell-Like Starship Abilities

Starship combat already includes magical effects at the appropriate scale.

Magic Officer Actions

These represent ship-scale magical effects:

Design Note: These actions use the same magical principles as personal spells but operate at starship scale. A Magic Officer channels far more energy than a personal spellcaster.

Magical Systems

Some starship components are inherently magical:

These systems are built to operate at starship scale from the start.

Optional Rule: Heightened Ship-Scale Spells

GM Discretion Rule: For high-level campaigns, GMs may allow 9th-rank or higher spells to affect starship components.

Requirements

1. Spell Level: Must be 9th-rank or higher
2. Target: Can only affect exposed external components
3. Casting Time: Normal casting time (starship combat uses same action economy)
4. Line of Sight: Caster must be able to see the component

Effects

Damage Spells: 9th-rank spells deal 1/10 normal damage to starship components (minimum 1).

Example: A 9th-rank fireball deals 14d6 damage (average 49). Against a starship component, this deals 4-5 points of damage.

Heightened DCs: Saving throws against spells targeting starship systems use the spell DC + 5.

Component Targeting:

Transmutation Effects: Spells like disintegrate or fabricate can destroy/create components of up to 100 cubic feet (2nd-tier ship components maximum).

Limitations of Optional Rule

Still Cannot:

• Directly damage hull or internal systems
• Affect ship-wide systems (computers, life support, power core)
• Scale up area effects automatically
• Target moving ships without clear line of sight

Balance Consideration: This rule allows high-level spellcasters to contribute to starship combat without overshadowing ship weapons. Spells remain less effective than dedicated ship systems.

GM Guidance: Consider whether allowing this rule fits your campaign. In hard sci-fi settings, personal magic may be completely ineffective against starships. In high-fantasy space opera, 9th-rank spells might be more potent.

VEHICLE-STARSHIP INTERACTIONS

Vehicles in Starship Combat

Vehicles are generally too small and slow for effective starship combat but may appear in certain scenarios.

Vehicle Limitations

Space-Capable Vehicles

Some vehicles can operate in vacuum:

Requirements:

• Environmental seal
• Maneuvering thrusters
• Radiation shielding

In Starship Combat:

• Considered stationary (cannot move hexes under own power)
• Can occupy same hex as starships
• May attack starship exposed components at close range

Vehicle vs. Starship Weapons

Vehicle Weapons → Starship:

• Heavy vehicle weapons deal 1/10 damage (round down)
• Anti-vehicle weapons deal 1/5 damage
• Minimum 1 damage on hit

Starship Weapons → Vehicle:

• Light weapons: ×5 damage
• Heavy weapons: ×10 damage (usually instant destruction)
• Capital weapons: Instant destruction (no save)

Deploying Vehicles from Starships

Launch Bays

Ships with appropriate expansion bays can deploy vehicles.

Launch Time: 1 round per vehicle
Recovery Time: 2 rounds per vehicle
Maximum Deployed: Equal to bay capacity

Drop Deployment

Vehicles can be dropped from ships in atmosphere.

Piloting DC: Expert DC 20

SURVIVAL EQUIPMENT

Environmental Protection

Armor Environmental Seals

Emergency Equipment

Breathing Apparatus

Survival Skills in Space

Survival Skill Uses

Avoid Hazard (Survival):
Identify and avoid environmental dangers.

DC: Varies by hazard (typically 15-25)

Extend Supplies (Survival):
Make environmental protection last longer.

DC: Expert DC 20
Time: 1 hour of maintenance

Emergency Shelter (Survival/Crafting):
Create temporary protection from environment.

DC: Trained DC 15 (basic) to Master DC 30 (hostile environment)
Time: 10 minutes to 1 hour (based on complexity)

This supplement is a fan work and is not affiliated with Paizo Inc.Starfinder is a registered trademark of Paizo Inc.