dlrk2 edited this page Oct 31, 2018 · 36 revisions

USI Life Support (v0.9.0.0)


USI Life Support (USI-LS) is a simplified life support system. It can be used by itself, or together with USI Modular Kolonization System (MKS). USI-LS allows you to simulate your Kerbals needing resources to stay alive, and consequences for running out of those resources.

Configuration options are detailed on the configuration page. It is recommended you use the defaults until you become familiar with USI-LS. To try out USI-LS without any negative consequences for failure, see the changes on the configuration page under 'Common Configuration Changes'. You can also make the 'exceptional' Kerbals (orange-suits) immune to negative effects. Doing this while learning will let you rescue stranded Kerbals or avoid some mistakes.

Life Support Resources

Kerbals need two resources to stay alive and happy: Supplies and Habitation.

Supplies are the abstraction of everything you consume to live: Oxygen, water, food, etc. Habitation is space to live, work, sleep and move around. USI-LS keeps a timer for each Kerbal for these resources. If any counter runs out, bad things happen to your Kerbal. In the default install, your Kerbal will become a Tourist; he or she won't be able to do anything until the situation is corrected.

Supplies has a 'grace period'. This is bonus time after the Supplies are used up that you are given. The idea is that your Kerbal can go for a while without food or water. The default value for this is 90 hours, or 15 Kerbin days. During this time your Supplies timer will show in negative values.

The Habitation countdown timer comes in two types: the current vessel your Kerbal is crewing, and the total amount of time the Kerbal can be away from Kerbin (in other words, on a mission). This will be explained further in the Habitation section.


Supplies, or Nutritional Organic Meal Substitute (N.O.M.S.), are carried in USI-LS containers. They can be added to your vessel at launch. New Supplies can also be created by farming. A single Kerbal consumes .0005 Supplies per second, which is 1.8 Supplies per hour. This is 10.8 Supplies per Kerbin-day.

The other resources involved in using Supplies are:

  • ElectricCharge, a stock game resource
  • Mulch, a byproduct of Supplies consumption. Excess Mulch is thrown overboard (destroyed) if you do not have a container to hold it
  • Fertilizer, used to produce more Supplies when combined with Mulch.

ElectricCharge is part of the stock game, produced by solar panels, batteries, etc. Kerbals require 0.01 ElectricCharge per second which can be the major life support limitation in the early game, particularly before solar panels are available. At 0.01 ElectricCharge per second, a single Kerbal will exhaust a Z-100 Battery Pack in about 2.8 hours. Note that kerbals only consume ElectricCharge when they have Supplies available to eat. (They need the electricity to operate their coffee makers, bagel toasters, microwave ovens, and refrigerators.)

Kerbals consume Supplies and convert them directly to Mulch:

Supplies Consumed Mulch Produced
A single Kerbal 1.8/hr (.0005 per second) 1.8/hr (.0005 per second)

Kerbals can go 90 hours without Supplies without incident. After 90 hours, bad things happen. In the default install, they become tourists - they will stop working, will not EVA and they will not command the ship. This is sometimes referred to as 'being grouchy' or 'striking'. Once provided Supplies, they'll return to work. By default this includes exceptional veteran Kerbals (Jeb, Bill, Bob, Valentina - those in orange suits). This and the penalties for running out of Supplies can be configured: See the configuration page for details.

Additionally, on Kerbin, Kerbals will not strike if below 25km altitude. They will still consume resources but will happily keep working. Assume they find some berries to eat if they run out of food. No need to manage Supplies for ground bases on Kerbin and low-flying atmospheric craft on Kerbin.

Parts for Supplies in USI-LS Install

  • Life Support MiniPak (Supplies): 100 Supplies, surface mount
  • Life Support MiniPak (Fertilizer): 100 Fertilizer, surface mount
  • Life Support MiniPak (Mulch): 100 Mulch, surface mount
  • Life Support Tank (1.25): 500 Supplies, 10 Mulch, inline mount
  • Life Support Tank (2.5): 4,500 Supplies, 150 Mulch, inline mount
  • Life Support Tank (3.75): 15,000 Supplies, 300 Mulch, inline mount
  • Fertilizer Tank (1.25): 500 Fertilizer, inline mount
  • Fertilizer Tank (2.5): 4,500 Fertilizer, inline mount
  • Fertilizer Tank (3.75): 15,000 Fertilizer, inline mount
  • Nom-O-Matic 5000 Greenhouse: Produces Supplies using Mulch and ElectricCharge and Fertilizer
  • Nom-O-Matic 25000 Greenhouse: Produces Supplies using Mulch, ElectricCharge and Fertilizer

Quick Reference for how many days Supplies will support a single Kerbal

Supplies Kerbin Days
100 9.3
500 46.3
4,500 416.7
15,000 1,388.9

Supply Recyclers, Converters, and ISRU

To extend the value of your Supplies, you can use two types of modules: Recyclers and Converters.

Converters create new Supplies from Fertilizer and Mulch. Recyclers reduce the per-second consumption of Supplies by Kerbals, extending the existing supply. Recyclers are listed in 'Efficiency' and 'Capacity' values, meaning they will reduce the consumption of Supplies by the efficiency value for up-to the capacity number of Kerbals. Kerbals beyond the capacity value are not effected and consume Supplies at the regular value. ISRU (In Situ Resource Utilization) is the process of using resources found on other celestial bodies to extend life support. USI-LS allows you to use the stock Convert-O-Tron 125 to convert stock Ore to Fertilizer. Though this is inefficient, it can allow you to create new Fertilizer, decreasing or eliminating the need for resupply.

USI-LS uses three converters, two recyclers, and one ISRU from a combination of USI-LS and stock game parts. Additional recyclers, producers, and ISRUs are available if MKS is installed.

Converter Image Source Mass Mulch Input (per day) Fertilizer Input (per day) Supply Output (per day) Supplies to Fertilizer Ratio
Nom-O-Matic 5000 USI-LS 0.154t 2.592 0.2592 2.8512 11
Nom-O-Matic 25000 USI-LS .708t 12.96 1.296 14.256 11
Nom-O-Matic 25000-I USI-LS 1.52t 25.92 2.592 28.512 11
Recycler Image Source Mass Efficiency Crew Capacity
Mobile Processing Lab MPL-LG-2 Stock 3.50 50% 4
RT-500 Recycling Module USI-LS 0.1 60% 1
ISRU Image Source Mass Ore Input (per day) Fertilizer Output (per day) EC Used (per day)
Convert-O-Tron 125 Stock 1.25 54,000 54 648,000


Kerbals need a certain amount of space to live in to stay happy, which is called Habitation. Even if a Kerbal has all the requirements to live off Kerbin, it's still not Home. In order to prevent them from getting homesick, you can station them (even briefly) in a well-built vessel designed for Habitation, and/or move them to a different vessel. A Kerbal will count down its time in a single vessel against that vessel's Habitation rating, but this is reset each time it transfers to a different vessel - even if just stretching their legs in the rover and returning! A Kerbal will also count down how long until they get homesick. If they are away longer than the BEST Habitation rating they've ever seen, they will become homesick. This value never resets until they return to Kerbin.

By default a Kerbal is willing to live about a week away from Kerbin before he gets homesick and wants to return. However if he's placed in a well built vessel, he can be tempted to forget about Kerbin for longer periods. If you then move your crew to a smaller, less well built vessel, they'll get upset much more quickly and they'll long to return to the well built vessel.

The Habitation value is tracked as two values:

  • A max number of days for the current vessel before a crew member gets upset. There is a counter that tracks against this number that is reset every time a crew member enters a new vessel.

  • A total maximum number of days a crew member is willing to be away from Kerbin. The max value for this counter will be set to the largest "current vessel" Habitation value that a crew member sees. The max value will only change if the crew member visits a better vessel than the best they've visited so far. The counter for this value never resets until the crew member returns to Kerbin, no matter how many vessels they transfer to.

Habitation Values

Habitation is calculated in Kerbal-Months. A part with 1 Kerbal-Month will rather obviously support a single kerbal for one month, or 30 days. Please note this is for Kerbin days. You can also think of one Kerbal-Month as 180 hours.

Every part that can hold crew will provide one Kerbal-Week per seat, so a Mk1 Command Pod provides 1 Kerbal-Week, while a Mk1-2 Command Pod provides 3 Kerbal-Week. In addition, the stock Hitchhiker Can provides a bonus 12.5 Kerbal-Months (in addition to the 4 kerbal-Week provided by its 4 seats) and is excellent for building bases. If you use MKS, other parts provide bonus Habitation.

Finally, special modules can provide Habitation multipliers. The only stock module which provides a 'Habitation multiplier' is the PPD-12 Cupola. Kerbals get less cranky if they can use huge windows to view the awesomeness of space.

The Kerbal-Months provided by your habitat space is multiplied by the vessel's total Hab Multiplier value. Every vessel has a base Hab Multiplier of 1. Any additional multipliers provided by parts are added to that to get the vessel's final Hab Multiplier. For example, a Cupola has a Hab Multiplier of 1.76. If a vessel has two Cupolae, its final Hab Multiplier is 1 + (1.76 * 2) = 4.52. If the vessel provides a base Habitation of 100 kerbal-months, the Hab Multiplier increases the ship's total Habitation to 452 kerbal-months.

Please note that all Modules that provide extra Habitation Time or a Habitation Multiplier will need to be activated through the right click menu once you have launched the craft.

Habitation Example

A crew member launches from KSC in a small rocket with a single pod. They initially have a Current Vessel max value of 30 days and a Home max value of 30 days. Each day they spend on that small rocket will be counted against both counters.

He docks after 2 days on to a station with 1 Hitchhiker Can and 1 PPD-12 Cupola. The base has a total of 45.54 Kerbal-Months of Habitation: 1 Hitchhiker = 12.5 + 4 seats = 16.5, multiplied by 2.76 (base 1, plus 1.76 for Cupola). Our single Kerbal can spend 1366 days on this station; the the max value for both Current Vessel and Home counters will be increased to 1366. The Current Vessel count for the current vessel will be reset to zero and start counting anew, however the count for Home will remain at 2 days and continue to increment.

If the crew member then transfers to a small Mun Lander (with a Habitation value of 45) after being aboard the station for 10 days, then the Current Vessel Max will drop to 45 days, the count for the current vessel will drop to 0, but the Total Time counter will be at 12 days and continue to increase with the max remaining that of the largest vessel they've visited (the 1366 from the station).

You can’t perform that action at this time.
You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Reload to refresh your session.
Press h to open a hovercard with more details.