My previous posts about my new starship construction system generated a bunch of interest and several people expressed a desire to see more. So I thought I’d post up bits and pieces of this over a series of posts. I’ll start by posting the things that are new relative to the starship construction system in the Star Frontiers Knight Hawks Campaign Book.

I already posted the introduction the the “A New Starship Construction System” post back in early November. Although it wasn’t labeled as such, the “Starship Engines” post that came shortly after the first one was part 2 as that was taken from the new system as well.

The timing of these posts will be probably be fairly sporadic as I’m using them as filler between posts on other topics and when I’m working on things that I’m not ready to post about.

I’ve already posted about the engines. The next major change is the life support system which is the topic of this post. With each of these posts going forward, I’ll try to include some of the rationale and thinking behind the choices I made and the way I designed it. So let’s get going.

Design Considerations

One of the things that I found problematic with the life support system as described in the standard rules was that it always felt way too small. For example say you had a ship that could support 9 people. According the the standard rules, all of the life support equipment for the entire ship, including all the food, oxygen, and water for 200 days of operation would weigh only 9 kg (20 lbs)!

That 9 kg is split half and half between the equipment and the consumables so there is 4.5 kg (10 pounds) of equipment to get all that food, water, and air throughout the ship and then 4.5 kg of the food and water itself. Now I don’t know about you, but there is no way I can feed my family of 9 for a week, let alone 200 days on 10 lbs of food. Maybe if it was all just a nutrient pill that you took once a day that had all your calories, vitamins, and minerals. But I think even that is stretching it and definitely not very satisfying.

One could argue for transmutation/replicator technology ala Star Trek but that just doesn’t jive with the feel of Star Frontiers for me and I don’t want that in my game. Beside the rules state that the life support systems “include food storage and preparation, and water, atmosphere and wast processing and disposal.” (KHCB p 14) That sounds like it should include a bunch of machinery and storage space.

So looking at the life support systems I saw two things that needed to address. One was food storage and preparation, and the other was water, air, and waste circulation and processing. All of that was going to take up space. I needed to make sure the system had enough mass and volume associated with it to include all the various bits of machinery and storage and pipes and duct work needed to get the various bits around the ship as needed.

Another aspect was that I wanted it to be completely configurable by the ship designer. The default rules were for a 200 day supply in the system. Since I knew this new system was going to be bulkier, I wanted to give the option to go for a smaller system if you knew that was all your needed. For example, a shuttle, that just goes up and down from the ground to orbit probably doesn’t need a life support system that can go 200 days without recharging. It probably only needs a few days at most and so can have a much lighter system.

Related to that I wanted to have different types of system for shuttles, system ships, standard interstellar ships, and first class accommodations. Each of those have different requirements and therefore should have different costs, volumes, and masses.

Taking all of that into account results in the following system. The excerpt of the rules that follows assumes that you’ve determined the crew size and number of the various passenger cabins you will have on the ship before to select the life support system.

Life Support Equipment

Now that you know the number of crew and passengers, you can select the amount of life support equipment the ship needs. It is recommended that you have at least one backup life support system in case there are problems with (or damage to) the primary system.  The life support system includes a variety of systems such as air filtering and circulation, food preparation, sanitation facilities, and waste management.  Life support on starships are mostly a closed system, almost everything gets recycled.  However there are some consumables that do need to be replaced (mainly foodstuffs) every so often.

Your life support system needs to be at least large enough to support the crew and passengers.  Typically, ships are designed with a little extra capacity as a safety margin or for emergencies.  There are four basic levels of life support available for ships, depending on the ship’s needs:

Rudimentary – This is an air supply system only.  It doesn’t handle food or waste materials and just provides an air supply and air circulation system with filtering.  This is the life support system you find on launches, workpods, fighter craft, and other ships that are not designed to be occupied for a long time.

Basic – This level of life support adds basic food storage and preparation, sanitation facilities, and waste management to the air supply system of the rudimentary life support level.  Supplies are stored and consumed and waste material has to be removed regularly.  There is little to no recycling of materials except for air and water.  This level of life support is typical of shuttles and some short distance system ships that typically operate for only short periods of time between calling on bases where their life support can be resupplied and waste material removed.  It may also be found on some lifeboats.  While you could equip a starship with this type of life support system, making it large enough to support long missions uses up valuable space in the ship and tends to be more expensive in the long run.

Standard – This is the typical system for any starship.  It consists of complete air and water recycling, as well as recycling of waste material.  It typically includes some sort of hydroponics system for both growing fresh food and recycling carbon dioxide back into oxygen.  There are full food preparation facilities as well as complete sanitation facilities.  This level of life support is required for Journey class passenger accommodations.

Deluxe – This is a more advanced version of the Standard system.  It provides better recycling, larger food preparation facilities, more variety in the fresh foodstuffs, and better (nicer) sanitation and waste management facilities.  This level of life support is required for any First Class passenger accommodations.

A ship can have different life support levels for different parts of the ship.  This is quite common on passenger liners.  For example, if a passenger liner has 20 First Class cabins and 100 Journey class cabins.  It is not very likely that the owners will invest in Deluxe life support for the entire ship (although if they did, it would figure prominently in their advertising).  Rather they would invest in a Deluxe life support system to cover the First Class cabins and a standard system to cover the Journey Class cabins and the crew.

The volume listed for the life support system includes both the machinery and hardware for processing the air, water, food, and waste material as well as storage space for raw materials and duct work to move material around the ship.

Every life support system has two ratings.  The first is the maximum number of beings the system can support.  This determines the amount of mass and volume allocated for the life support machinery (pumps, filters, ducts, pipes, etc.).  The second is the maximum number of days that the system can support those beings without being refilled/recharged.  This determines the amount of volume committed to storage of life support supplies.

Base hardware costs and volumes per being supported

All values except base system volume are multiplied by the maximum number of beings the system can support at one time.

Type	Cost	Mass	Base system volume	Volume
Rudimentary	500 cr	0.2 tons	1 cu m	0.1 cu m *
Basic	1500 cr	2 tons	6 cu m	5 cu m
Standard	3000 cr	4 tons	15 cu. m	8 cu m
Deluxe	5,000 cr	6 tons	30 cu. m	10 cu m.

* This volume assumes you are equipping a small one or two room craft with this system like a fighter or launch.  If you try to put this into a larger ship the volume goes up by a factor of 10 for the ducting and pipes needed.

For example, our passenger liner has 20 First Class cabins and 100 Journey class cabins for crew and passengers.  It would need two life support systems.  The Deluxe system would support 20 beings.  It would cost 20 x 5000 = 100,000 cr, have a mass of 20 x 6 = 120 tons, and take up 30 (base volume) + 20 x 10 (volume per being) = 230 cubic meters.  The Standard system for the Journey class cabins would cost 100 x 3000 = 300,000 cr, have a mass of 100 x 4 = 400 tons and take up 15 + 100 x 8 = 815 cubic meters.  Thus the Standard system while being just a little more than 3x the size of the Deluxe system, supports 5x as many beings.

Supply cost per being per day

In addition to the base machinery costs, there is the cost of the food, air, and water needed for the beings on board.  Multiply each value times the maximum number of beings the system can support and then by the number of days you want to be able to support those beings without a reload/refill of the system.

Type	Cost	Mass	Volume
Rudimentary	10 cr	0.05 tons	.1 cu m
Basic	15 cr	0.15 tons	.4 cu m
Standard	25 cr	0.1 tons	.15 cu m
Deluxe	40 cr	0.15 tons	.25 cu m

So if our passenger liner wanted to support its full complement of crew and passengers for 200 days without a resupply, the cost of the supplies and storage areas would be as follows:  For the Deluxe system the cost is 40cr x 20 beings x 200 days = 160,000 cr, the mass would be 0.15 tons x 20 x 200 = 600 tons, and the volume would be 0.25 cu m x 20 x 200 = 1000 cubic meters.  The standard system supplies would cost 25 cr x 100 beings x 200 days = 500,000 cr, the mass would be 0.1 tons x 100 x 200 = 2000 tons, and the volume would be 0.15 cu m x 100 x200 = 3000 cubic meters.

Thoughts and Comments

That’s the life support system rules in the the new system. Let me know what questions or thoughts you have in the comments below.

I was going to post another ship next but realized that I should probably talk a little bit about the way I redesigned the engines in my new starship construction system.  Otherwise, some of the bits of information about the ships won’t make sense.  I’ve published some of this on-line before but I don’t remember exactly where so I’m repeating it here for completeness.  Here is the section on engines from the starship construction system document.

Engines

Now that we know the mass of our ship, it’s finally time to determine its propulsion. Each type and size of engine is rated to have a specific thrust and fuel capacity. Your ship’s hull size determines the maximum number of engines it can support. You don’t have to have to fill all your engine slots if that number of engines is not needed to achieve the performance you desire.  And regardless of hull size and engine type, the maximum acceleration of any ship is 6g.

Hull Size	Max Engines
1	1
2-4	2
5-8	4
9-12	6
12+	8

(Note:  I didn’t even follow my own rules when I created the PGC C-10 Fast Courier as I gave it 4 engines at HS 4.  This is something I’m still thinking about/working on.)

Engine thrust is given as an arbitrary thrust rating that has been scaled to work with the mass of the ship as given in tons. To determine the maximum acceleration of your ship, add up the thrust ratings of all your engines and divide that by the total mass of your ship in tons. The resulting number is the maximum acceleration of your ship in multiples of one standard gravity (10 m/s/s). Round all fractions down to the nearest tenth of a g.

Chemical Engines

These engines use a high efficiency chemical fuel that burns and is expelled out the engine nozzle to provide thrust.  These engines are relatively cheap and easy to produce.  While very powerful, because of the large volume of fuel needed, these engines have limited capability in regards to how long the engines can operate on a single fuel load.  These engines are typically used for ground-to-space shuttles and system ships.

Ion Engines

Ion engines work by ionizing hydrogen and accelerating the resulting protons and electrons to high velocity and expelling them out the back of the engine to provide thrust.  Each engine contains a small nuclear reactor to provide the power needed to ionize the hydrogen and accelerate the particles to the relativistic speeds needed to generate thrust.  This reactor uses the same atomic fuel pellet as an atomic engine but only needs to be replaced once every 10 years.  The initial fuel pellet is included in the cost of the engine.

While not as powerful as chemical or atomic engines, Ion engine fuel is relatively cheap and if a ship is properly equipped, can be harvested from any gas giant for free. 

Because of the nature of the engine, ships with ion engines cannot land on or take off from planets.

Atomic Engines

An Atomic engine is a supercharged version of the chemical engine and uses the same fuel.  The engine works by generating a quantum field that temporarily increases the momentum of particles by a factor of hundreds. These temporarily super-massive particles are ejected out of the back of the engine to generate thrust for the ship.  Because each particle is effectively much more massive, less fuel is needed to achieve the same thrust and instead of a single fuel load lasting for only few minutes of thrust, it can last for days and allow the ship to accelerate to Void jump speeds.

However, generating this field requires a huge amount of energy (which is transferred to the particles) during operation.  To provide this power, each engine contains its own nuclear reactor, similar in design to the reactor in the ion engine.  However, the large power requirement of the atomic engine means that it consumes one atomic fuel pellet after only 10,000 minutes of full thrust operations (about 8.5 days) instead of the 10 year life span for the atomic fuel pellet in an ion engine.

In addition, atomic engines require an overhaul every few jumps, again depending on the size of the engines.  This overhaul is necessary to make sure that the quantum field generators are properly aligned and positioned to only affect the fuel and not the body of the engine itself.  The number of trips that a ship can go between overhauls depends on the size of the engine and is given in the table with the fuel costs below.

Engine Costs

The following table gives the cost and thrust values for each of the different types and sizes of engines.  Determine the number, size, and type of engines your ship will use and then record the engines chosen for your ship.

	Class A		Class B		Class C
Engine Type	Thrust	Cost	Thrust	Cost	Thrust	Cost
Chemical	6,250	50,000	20,000	175,000	80,000	770,000
Ion	3,000	100,000	10,000	400,000	40,000	2,000,000
Atomic	6,250	250,000	20,000	1,100,000	80,000	6,000,000

Fuel

Next you need to provide fuel for your engines and determine how much acceleration each fuel load will provide for your ship.  Each engine uses different types of fuel and has different storage capabilities and requirements.

Chemical Engines

Each fuel load allows a chemical engine to operate at maximum thrust for 60 minutes.  This is typically enough to allow the ship to make one round trip between the ground and orbit or limited acceleration and maneuvering in space.  Each engine can only hold a single fuel load and must be refueled after each load is expended.  The cost of a fuel load depends on the size of the engine and is given in the following table.

Engine Class	Cost of a fuel load
Class A	300 cr
Class B	1000 cr
Class C	4200 cr

Ion engines

Although not as powerful as chemical or atomic engines, these engines are reliable and can hold more fuel.  While they can technically run off any material, the fuel of choice is hydrogen.  Using any other fuel source decreases the thrust provided by the engines by a factor of two.  Each engine can hold 10,000 fuel units and each unit provides 10 minutes of operation at maximum thrust (A fully fueled ion engine can operate continuously for over 80 days without refueling).  A fuel unit costs 5, 17, or 70 cr per unit for Class A, B, or C engines respectively.

Once every 10 years, the atomic fuel pellet in the ion engine’s reactor needs to be replaced, the cost for this fuel pellet is the same as that for a similarly sized atomic engine.

Atomic engines

Like the other engines, Atomic engines store all their fuel internally.  The fuel for these engines consists of two parts.  The first is a load of fuel like the chemical rockets, the second consists an atomic fuel pellet (typically uranium) to power the reactor. The amount of fuel that can be stored depends on the size of the engine and is given in the table below.

Each atomic fuel pellet and load of chemical fuel provides enough fuel for 10,000 minutes (about 8.3 days) of operation at maximum thrust.  The cost of a fuel pellet depends on the size of the engine, given in the table below.  The cost of the chemical fuel is identical to that of the chemical engines of the same size.

Consult the table below to determine the number of fuel loads & pellets held and time between each overhaul for each engine size.

Engine Class	Trips between overhauls	Maximum Fuel Loads & Pellets loaded	Cost per pellet (cr)
Class A	1	3	10,000
Class B	3	6	32,000
Class C	10	12	125,000

Compute total acceleration per fuel load

Acceleration is measured in ADF.  One ADF is defined as 10 minutes of acceleration at 1g. (For you Star Frontiers grognards out there, I’ve redefined the boardgame hex scale to 3600 km so that 1 ADF does equal 1g acceleration for 10 minutes, and 1 g is defined as 10 m/s/s not 9.8.)

If you want to keep it simple, you can simply assume the following:

• a load of fuel in a chemical rocket provides just enough thrust to make one round trip between the ground and orbit around a planet or can provide a total of 8 ADF in space. 
• Ion engines use one fuel unit per engine per ADF and a total of 1000 fuel units per engine for a single interstellar jump
• Atomic engines use one chemical fuel load and one atomic fuel pellet for a single interstellar jump or the same fuel provides enough thrust for a total of 1000 ADF if operating solely in-system.

If you want to be a bit more exact and track the exact fuel usage you can do the following to compute the total number of ADF that a load of fuel will provide for your ship.  This will depend on the type of engine you have.  It requires more bookkeeping but actually results in less fuel being needed in the long run, sometimes significantly if the ship has a high maximum ADF.

• Chemical Engines – Take the maximum acceleration you calculated for the ship earlier and multiply it by 6.  This is the total number of ADF your ship gets from using one load of fuel in each engine.
• Ion Engines – The maximum acceleration calculated above is the number of ADF provided by expending a single ion fuel unit in each engine.
• Atomic Engines – Take the maximum acceleration calculated earlier and multiply by 1000. This is the total ADF provided by using one unit of chemical fuel and one atomic fuel pellet in each of your engines.

Round all fractions down.  Assume that that small difference is used up in minor station keeping and maneuvering

Examples

Chemical Engine

Fully loaded a Digger Shuttle (HS 2) has one Class A chemical engine and a maximum acceleration of 4.7g.  Since it has chemical engines, the total ADF provided by the single load of fuel in its engine is 4.7 x 6 = 28.2 or 28 ADF.   

Ion Engine

A small (HS 7) freighter is equipped with four Class B ion engines.  Fully loaded, its maximum acceleration is 1.1g.  Thus by using up one fuel unit in each of its four engines, it has 1.1 ADF available.  If each engine carries it’s maximum fuel load (10,000 units each), the total ADF available to the ship is 11,000 ADF.  Since each interstellar jump typically takes 1000 ADF to complete, the ship can make 11 trips without refueling if it needed to.

Atomic Engine

The newly designed Swift class assault scout has a total mass of 2470.83 tons and two Class A atomic engines for a total thrust of 12500.  This gives a maximum acceleration of 5.059g which rounds to 5.0.  The total ADF available to the assault scout from one load of fuel in each engine is therefore 5×1000 = 5000 ADF.  After expending this much thrust, the assault scout will have used two loads of chemical fuel and two atomic fuel pellets, one in each engine.