A KSP 1.x mod that adds a full Kerbal life-cycle — pregnancy, birth, childhood and aging — with real gameplay consequences for EVA, piloting, science labs, resource harvesters, career upkeep costs and crew caretaking.
| Item | Version / Note |
|---|---|
| KSP | 1.x (tested on 1.12) |
| Game mode | All — Career-specific features activate only in Career mode |
| Breeding vessel | Must have a Science Lab AND a part with crew capacity >= 4 |
- Build the project (Visual Studio) or download a release
.dll. - Copy
BreedTheKerbal.dllandBreedTheKerbal.cfgintoGameData/BreedTheKerbal/. - Launch KSP — the Colony Manager toolbar button appears in the Flight and Space Centre scenes.
Every Kerbal born through the mod passes through four stages.
[Born] -> Newborn (50 days) -> Child (100 days) -> Teenager (150 days) -> Adult
All durations are in Kerbin days (1 Kerbin day = 6 h real-time).
They can be changed in BreedTheKerbal.cfg without recompiling.
| State | EVA | Science Lab / Harvester | Pilot | Notes |
|---|---|---|---|---|
| Newborn | BLOCKED | 0% | 0 stars | Death clock without caretaker (5 d) |
| Child | BLOCKED | 25% | 0 stars | Death clock without caretaker (15 d) |
| Child — Low Support | BLOCKED | 20% | 0 stars | Insufficient career funds |
| Teenager (with caretaker) | OK | 50% | 0 stars | — |
| Teenager (no caretaker) | BLOCKED | 20% | 0 stars | EVA button grays out |
| Teen EVA — chaperone leaves | OK (already out) | — | — | SAS off, jetpack 2% |
| Pregnant — first half | OK | 100% | Full | No penalty |
| Pregnant — second half | BLOCKED | 40% | Level 1 only (basic SAS T-key) | — |
| Postpartum | BLOCKED | 0% | — | 10-day recovery |
The Colony Manager tooltip (hover over a Kerbal name) shows the active penalty in orange/red and a live countdown to death when a Newborn or Child has no caretaker.
- EVA portrait button is permanently grayed out (G-force blackout mechanism).
- Experience level forced to 0 — no pilot SAS modes, no engineer/scientist bonuses.
- Caretaker (adult crew member on same vessel) required.
- Newborn: dies after 5 Kerbin days without caretaker.
- Child: dies after 15 Kerbin days without caretaker.
- Countdown visible in Colony Manager tooltip.
- Moving a Newborn without an adult on the vessel triggers a warning.
- EVA button grayed out when no adult is on EVA within 200 m.
- When a chaperone IS on EVA the button becomes available.
- If the chaperone boards back while the teen is on EVA:
- Jetpack thrust drops to 2% of normal (translation still works).
- Experience level forced to 0.
- Efficiency 50% with caretaker on vessel, 20% without.
- EVA button grayed out.
- Pilot experience capped at level 1 (T-key SAS hold only, no prograde/retrograde modes).
- Science lab and harvester efficiency: 40%.
- After birth the experience level is automatically restored from accumulated XP.
- EVA button grayed out.
- Science lab and harvester efficiency: 0%.
- Part with crew capacity >= 4 (large habitat)
- Science Lab present
- At least one adult male and one adult female (not pregnant / postpartum)
- At least one free seat (auto-reserved during pregnancy)
Open Colony Manager -> select a male and female -> click Start Pregnancy.
Set AutoBreeding = true in BreedTheKerbal.cfg.
Any loaded vessel meeting all conditions will automatically pair once per update cycle.
Pregnant --(30 days)--> Birth --(10 days postpartum)--> Adult again
|
+-> Newborn boards the vessel automatically
(loaded or unloaded — both handled)
If no free seat: stays Available in Astronaut Complex
| Phase | EVA | Efficiency | Pilot SAS |
|---|---|---|---|
| First half (days 0-15) | Yes | 100% | Full |
| Second half (days 15-30) | No | 40% | Level 1 only |
| Postpartum (10 days) | No | 0% | — |
If a birth occurs while the mother's vessel is not the active vessel, the newborn is placed
directly into the vessel's ProtoVessel (no free seat required to be present in IVA).
When you later switch to that vessel, the newborn is already on board.
If the newborn ended up in the Astronaut Complex due to an older save, switching to the vessel where the mother is will automatically re-board the child.
| Parents | Outcome |
|---|---|
| Same + Same | 96% same trait, 2% each other |
| Mixed (e.g. Pilot + Scientist) | 48% trait A, 48% trait B, 4% third trait |
Gender is always 50% male / 50% female.
| Stage | No caretaker — effect | Death timer |
|---|---|---|
| Newborn | Death clock starts + visible in Colony Manager tooltip | 5 Kerbin days |
| Child | Death clock starts + visible in Colony Manager tooltip | 15 Kerbin days |
| Teenager | Efficiency 20% instead of 50%, EVA button grays out | no death |
| Stage | Cost / day |
|---|---|
| Newborn | 150 funds |
| Child | 100 funds |
| Teenager | 50 funds |
If funds are insufficient LOW SUPPORT activates:
| Stage | Normal | Low Support |
|---|---|---|
| Child | 25% | 20% (x 0.80) |
| Teenager (with caretaker) | 50% | 35% (x 0.70) |
LOW SUPPORT clears immediately once funds exceed the daily cost.
Non-adult Kerbals accumulate age at a speed that can be raised or lowered by vessel conditions.
The Colony Manager shows the net modifier in the +X% column next to each Kerbal.
Click the +X% label to open a per-factor breakdown popup.
| Condition | Modifier |
|---|---|
| Each Cupola Module on vessel (max 3) | +5% per cupola |
| Vessel landed or splashed | +10% |
| Active CommNet connection to home | +2% |
| Scientist as best caretaker-adult on vessel | +5% |
| Engineer as best caretaker-adult on vessel | +3% |
| Both biological parents on same vessel | +5% |
| No biological parents on vessel | −5% |
| Crew count > 75% of vessel capacity | −5% |
| Low Support active | −10% |
Modifiers are additive. A negative total slows aging below base rate.
All thresholds and values are configurable in BreedTheKerbal.cfg.
- Toolbar button: Flight and Space Centre scenes.
- Per-vessel list with stage badge, progress bar, efficiency % (orange = penalty, red = 0%), time remaining, and aging speed bonus column.
| Click target | Result |
|---|---|
| Kerbal name | Popup — parents' names, trait, experience stars |
| +X% / ±0% aging label | Popup — per-factor aging speed breakdown with total |
| Clicking outside a popup | Closes the popup |
| Hover target | Result |
|---|---|
| Kerbal name | Tooltip — stage, trait, stars, efficiency, active penalty, caretaker death countdown |
| LOW SUPPORT badge | Tooltip — penalty breakdown and how to fix |
- Pairing panel (manual mode): male / female selectors + Start Pregnancy button.
No recompile needed — edit and restart KSP. All durations in Kerbin seconds (1 Kerbin day = 21 600 s).
| Key | Production default | Description |
|---|---|---|
PregnancyDuration |
648000 (30 d) | Length of pregnancy |
PostpartumDuration |
216000 (10 d) | Postpartum recovery |
NewbornDuration |
1080000 (50 d) | Time as Newborn |
ChildDuration |
2160000 (100 d) | Time as Child |
TeenagerDuration |
3240000 (150 d) | Time as Teenager |
NewbornDeathTimer |
108000 (5 d) | Newborn dies without caretaker after this |
ChildDeathTimer |
324000 (15 d) | Child dies without caretaker after this |
LatePregnancyEfficiency |
0.40 | Efficiency — second half of pregnancy |
PostpartumEfficiency |
0.00 | Efficiency during postpartum |
NewbornEfficiency |
0.00 | Newborn efficiency |
ChildEfficiency |
0.25 | Child efficiency |
TeenagerEfficiency |
0.50 | Teenager efficiency (with caretaker) |
NoCaretakerTeenagerEfficiency |
0.20 | Teenager efficiency (no caretaker) |
LowSupportChildFactor |
0.80 | Low Support multiplier for Child |
LowSupportTeenagerFactor |
0.70 | Low Support multiplier for Teenager |
NewbornDailyCost |
150 | Career funds / Kerbin day (Newborn) |
ChildDailyCost |
100 | Career funds / Kerbin day (Child) |
TeenagerDailyCost |
50 | Career funds / Kerbin day (Teenager) |
HabitatMinCrewCapacity |
4 | Minimum part crew capacity for habitat |
AutoBreeding |
false | Enable automatic pairing |
CupolaAgingBonusPerUnit |
0.05 | Aging bonus per Cupola Module (+5%) |
CupolaAgingMaxCount |
3 | Maximum cupolas counted toward the bonus |
LandedAgingBonus |
0.10 | Bonus when landed or splashed (+10%) |
CommNetBonus |
0.02 | Bonus when connected to home via CommNet (+2%) |
BothParentsAgingBonus |
0.05 | Bonus when both parents are on board (+5%) |
NoParentsAgingPenalty |
0.05 | Penalty when no parents are on board (−5%) |
ScientistCaretakerBonus |
0.05 | Bonus for Scientist as best adult caretaker (+5%) |
EngineerCaretakerBonus |
0.03 | Bonus for Engineer as best adult caretaker (+3%) |
OvercrowdingThreshold |
0.75 | Crew/capacity ratio above which penalty applies |
OvercrowdingPenalty |
0.05 | Penalty when vessel is overcrowded (−5%) |
LowSupportAgingPenalty |
0.10 | Aging speed penalty when Low Support is active (−10%) |
| Shortcut | Action |
|---|---|
| Alt + Shift + B | Print all Kerbal life-stage statuses to screen |
| Alt + Shift + N | Advance all non-adult Kerbals one stage forward |
- Fix: Newborn now boards correctly when the mother's vessel was unloaded at birth (
ProtoPartSnapshot.seatIdxfix). - Fix: Retroactive boarding — switching to the vessel where the mother lives auto-boards any newborn that previously ended up in the Astronaut Complex.
- Initial public beta release.
- Full life-stage system: Newborn / Child / Teenager / Adult.
- Pregnancy and postpartum mechanics.
- Caretaker death timers.
- Aging speed bonus system (9 modifiers).
- Career mode daily upkeep with Low Support fallback.
- Parents & aging breakdown popups.
- AutoBreeding option.
- Custom toolbar icon (
BTK_icon.png).
MIT — free to use, modify and redistribute with attribution.