Reliability

From MegaTravellerWiki

In MegaTraveller, no provision is made for vehicles and starships which are more or less reliable than their competitors. All vehicles and starships can last indefinitely until they suffer some form of combat damage or collide with some form of satellite object (though they do require annual overhauls at a fixed cost). This is an attempt to address these concerns and add in the possibility of routine non-critical malfunctions in vehicles and craft due to simple wear and tear. To represent this possibility, all unit designs are given an additional "Reliability" factor which determines how prone they are to mechanical failure.

Note that in this document, vehicle, craft, and starship are used interchangeably. Reliability applies to all pilotable machines that are designed using the rules in the Referee's Manual.

Reliability Points

All vehicles, small craft, and starships have by default a number of Reliability Points (hereafter referred to as RP) equal to their Tech Level - 5, multiplied by 2; if this is zero or less, the vehicle has no RP by default. For example, a TL7 vehicle will have {(7-5)*2} 4 RP by default. A TL15 starship will have {(15-5)*2} 20 RP by default.

Additional RP may be purchased during the vehicle design process: the designer can increase the craft's base cost by 1% in order to buy 1 RP — the resulting cost is called the adjusted cost and is tracked separately from the base cost, though the adjusted cost is what is used when the vehicle is purchased or manufactured. Fractional allotments of RP are not allowed; all RP must be integers, meaning that a vehicle could not be increased in cost by 2.5% to buy 2.5 RP.

The maximum increase in the number of RP that a design has is equal to its Tech Level - 5 multiplied by 10; another way to remember this is that the design cannot be given more than five times its default RP. A TL8 vehicle, for example, cannot be increased in value to have more than 30 RP, and has a default of 6 RP.

If a vehicle has more than zero RP, these RP can be exchanged back for a discount of up to 20% in the vehicle's final cost, at a ratio of 1 RP per 1% cost return. A vehicle may never have less than 0 RP.

Wear Points and Tear Points

In spite of the somewhat obvious play on "wear and tear", Wear Points are defined as natural deterioration in the engine systems due to sustained use, while Tear Points are defined as cracking, bending, and other forms of naturally-occurring damage to the mechanical parts of the vehicle's suspension or thrusters during what is assumed to be the occasional nasty bump or chunk of foreign debris.

As Wear Points accumulate beyond a certain threshold, a unit suffers a chance of a power system breakdown. As Tear Points accumulate beyond a certain threshold, a unit suffers a chance of a locomotive system breakdown. The process continues indefinitely until eventually the unit's power system or locomotive system become too damaged to function, whereupon the unit becomes "dead in the water" until it can obtain proper repairs.

Spending Reliability Points

When a pool of Reliability points has been bought for a given vehicle during that vehicle's design, each point can then be spent on one of three categories: Lifespan, Drivespan, or Durability.

Lifespan

Each point of Reliability placed into lifespan gives 120 Wear Points of guaranteed continuous operation. Continuous operation means that the craft will never check for a power failure while it still has Lifespan remaining.

Various power plants accrue Wear Points at different rates. In general, any engine which consumes hydrocarbons involves a lot of moving parts and is more prone to failure. Antimatter or radioactive engines are by their nature self-destructive and are also relatively prone to failure, though they last twice as long as an internal combustion engine. Fusion powered engines are more efficient than nuclear or matter-conversion engines, with two-and-a-half times more reliability than hydrocarbon engines. Batteries and fuel cells are so simple in design that they are the most trustworthy; these are three times more reliable than hydrocarbon-powered engines. Naturally, of course, batteries and fuel cells are bulky and weak.

A vehicle powered by an internal combustion engine with a Lifespan of 15 (a very high-quality engine) will be able to run its engine for a total cumulative time of 1800 hours (225 eight-hour days) before it has a chance to suffer a single mechanical failure. Given that an average passenger vehicle on 21st-Century Earth sees less than 2 hours of use per day, this vehicle would last nearly 3 years before it had a chance of failing.

Drivespan

Each point of Reliability placed into drivespan gives 100 Tear Points of guaranteed operation range. Guaranteed operation range means that the craft will never check for a locomotion failure while it still has Drivespan remaining.

Contact-based locomotion on vehicles involve the most moving parts and they will break down sooner than any other motive system, with ranges measured in thousands of kilometres (or megametres if you prefer). Thrust-based locomotion is a considerable improvement -- the reason that most vehicles became Nap-Of-Earth thrust-based vehicles at TL9 and above -- with five times the operational range of contact-based vehicles before breakdowns begin occurring. Spaceship Maneuver Drives are extremely reliable and are measured in multiples of Astronomical Units instead of multiples of 1,000 km. Jump Drives are measured in multiples of parsecs.

Durability

Each point of Reliability placed into Durability gives the vehicle Die Modifiers to its mechanical failure throws, proportional to the total Durability divided by 5 and rounded down (to a maximum of 3).

Durability cannot be larger than Lifespan or Drivespan, whichever is greater. For instance, if a vehicle has Lifespan 5 and Drivespan 10, Durability must be 10 or less.

Durability can be larger than 15, but will not provide any immediately tangible benefit (as the maximum DM to mechanical failure rolls is always 3). However, a vehicle's Durability begins to deteriorate if the vehicle's Lifespan or Drivespan has been completely exhausted, so a Durability greater than 15 can provide benefits in the long run.

Accumulation of Wear Points

While a craft is "online" and operating under its own power, it gains 1 Wear Point when any of the following conditions are met:

• Every 1 hour of continuous use if the power plant consumes Hydrocarbons

The power plant involves many moving parts and suffers considerable wear and tear due to heat.

• Every 2 hours of continuous use if the power plant consumes Antimatter or Radioactives.

The power plant involves few moving parts, but the energy released from nuclear or matter-conversion reactions is very destructive and produces a lot of waste heat.

• Every 2.5 hours of continuous use if the power plant consumes Hydrogen.

The power plant involves few moving parts and the fusion reaction, though high-energy, is relatively safe.

• Every 3 hours of continuous use if the "power plant" is a fuel cell or battery.

The power plant involves almost no moving parts and offers a steady supply of "soft" electricity.

Count the number of hours of use separately for each power plant type if the vehicle has more than one, but keep a single pool of Wear Points for the vehicle as a whole. For instance, if a vehicle runs on battery power only for 75 hours and then switches on an internal combustion engine for 50 hours, it accrues 75 hours towards its battery (working out to 25 Wear Points) and 50 hours towards its ICE (working out to 50 Wear Points), for a total wear of 75 Wear Points.

Alternatively, you can track all of these in terms of fractional numbers of Tear Points per exact number of hours of any given engine being run, but this can be costly in terms of mathematics. Use whatever method of tracking the acquisition of Wear Points that suits you best.

If you are using a proportional fuel consumption system which makes it so engines only produce exactly as much power as they need to, the number of hours required to accrue a Wear Point is proportional to the percentage of maximum power being used. For instance, if an internal combustion engine is good for driving at 125 km/h and you are driving only at 50 km/h, your vehicle accrues Wear Points at only 40% of the usual rate. Assume that there is an absolute minimum consumption rate of 10% (idle) if the vehicle has not been shut off and is using any other power plant than a battery or fuel cell. (For instance, the above-mentioned vehicle will consume 10% of its normal consumption per hour at any speed from 0 km/h up to 12.5 km/h.)

Accumulation of Tear Points

As a craft is piloted under its own power, it gains 1 Tear Point when any of the following conditions are met:

• Every 1,000 kilometres it drives using a contact-based suspension.

The suspension of contact-style locomotion must be elastic. One assumes that a contact-based suspension is not operating on perfectly glass-like terrain, and encounters situations which stress the suspension from time to time.

• Every 5,000 kilometres it moves using a thrust-based suspension.

The suspension of thrust-style locomotion relies on air or superheated air and does not suffer physical deformation, rendering a smoother ride and less strain on the thrusters.

• Every 1 AU it traverses under Maneuver Drive.

Maneuver Drive is the de-facto standard thruster used in space.

• Every 1 pc it traverses under Jump Drive.

Jump Drive is the de-facto standard means of creating a capsule field to enter jump space.

All of these conditions should be tracked with full precision individually from one another, but the total number of Tear Points a unit has should be tracked as a single pool. For instance, a wheeled vehicle that drives 100 kilometres is 1/10th of the way towards accruing a Tear Point. If it drives 900 more kilometres at any point in the future, it has travelled a total of 1,000 kilometres and receives a Tear Point. If a spacecraft has running wheels as well as Maneuver Drive, the unit can drive 500 kilometres on its running wheels, then take off and travel 0.5 AU without accruing a single Tear Point. If it travels back the same way, landing after travelling 0.5 AU and then driving for 500 km, it accrues 2 Tear Points, once for the Maneuver Drive and once for the running wheels.

Alternatively, you can track all of these in terms of fractional numbers of Tear Points per exact distance travelled, but this can be costly in terms of mathematics. Use whatever method of tracking the acquisition of Tear Points that suits you best.

Failures

When a unit has accrued 120 Wear Points, the design loses 1 Lifespan point. If the design has no Lifespan points remaining, 2d6 are thrown. The craft's Durability divided by 5, rounded down, is added to the roll as a DM (maximum DM is +3), and then one point of Durability is lost (i.e., only subtract one point of Durability after the roll) if any is remaining. If the roll (after DMs) is 5-, the unit will suffer an engine malfunction at some point in the near future: roll 2d6 and multiply by 10 to determine the number of further Wear Points to be accrued before rolling on the Power Malfunction Table corresponding to the type of power plant aboard your vehicle that was being used when the final Wear Point was accrued (most vehicles have only one power plant).

 Hydrocarbon Engine Malfunction
Roll    Failure
-----  -------------------------
   2    Total Engine Failure
   3    Severe Engine Damage
   4    Moderate Engine Damage
   5    Moderate Engine Damage
   6    Minor Engine Damage
   7    Minor Engine Damage
   8    Engine Shutdown
   9    Fuel Consumption +100%
  10    Fuel Consumption +200%
  11    Power Output -25%
  12    Power Output -50%

TODO: POWER MALFUNCTION TABLES

When a unit has accrued 100 Tear Points, the design loses 1 Drivespan point. If the design has no Drivespan points remaining, 2d6 are thrown. The craft's Durability divided by 5, rounded down, is added to the roll as a DM (maximum DM is +3), and then one point of Durability is lost (i.e., only subtract one point of Durability after the roll) if any is remaining. If the roll (after DMs) is 5-, the unit will suffer a locomotion malfunction at some point in the near future: roll 2d6 and multiply by 10 to determine the number of further Tear Points to be accrued before rolling on the Locomotion Malfunction Table corresponding to the type of locomotion aboard the vehicle. The locomotion that receives the malfunction will be the one being used when the final Tear Point is accrued, if your vehicle has more than one motive system.

TODO: LOCOMOTION MALFUNCTION TABLES

Notes on Failures

• Routine mechanical failures cannot occur in combat. They occur only in "campaign time". However, it is possible that a vehicle may suffer a mechanical failure immediately before or after a combat situation. You should never attempt deliberately to cause a failure before a combat situation occurs, but if it coincidentally happens, there's no need to intervene in the players' fate.

• If a failure is going to occur, you may opt to delay the failure until an inopportune moment, but the failure should never be life threatening, only inconvenient. Good times for failures are when players must race to complete an objective, to make a rendezvous, or to make a deadline. Be sure to remind the players that such failures can be avoided by overhauling their vehicle on a regular basis so they don't accuse you of being pointlessly adversarial.

• A mechanical failure which strands the ship in an uninhabited system can be deadly. Consider ignoring the mechanical failure or delaying the failure until the ship arrives in a system where it can call for help. If players start to appear to be taking advantage of this fact, however (such as "Hey, Jeremy won't give us mechanical failures if we take uncharted routes!"), be sure to respond to that line of thinking in whatever way you see fit...

Repairing Failures

Most malfunctions are of a temporary, non-critical nature and can be fixed with relatively little effort. The rarer malfunctions which cause damage can result in more permanent breakdown of the power plant or locomotion system and require extensive repairs.

TODO: DECIDE ON POWER MALFUNCTIONS AND LOCOMOTION MALFUNCTIONS
  Can't give tasks to repair malfunctions without having tables of possible
  malfunctions in the first place!

Restoring Reliability

Reliability can be restored by spending money on parts and materials and by spending time making "overhauls". Ultimately, however, it is sometimes more practical to buy a brand new unit at a higher tech level than to continue to repair and restore a unit at a lower tech level, due to the simple fact that the unit at the higher tech level is more powerful and more innately reliable.

Note that while vehicles that do not have a default Reliability do not require annual overhauls, they will frequently fail.

Overhaul Cost

Total the number of points of Lifespan, Drivespan, and Durability lost and divide by 10. This is the percentage of the vehicle's base cost (not its adjusted cost!) that it will take in raw parts and materials in order to effect the overhaul.

Example: if a vehicle has a standard Reliability of 20 and has lost 4 points of Lifespan and 3 points of Drivespan, the vehicle will cost {((4+3)/10)%} 0.7% of its base cost in raw materials and parts in order to be overhauled. This is a fair bit greater than the 0.1% cost for an annual overhaul cited in the Imperial Encyclopedia, so be forewarned.

Overhaul Time

The vehicle must undergo overhaul for a number of hours equal to the vehicle's UCP multiplied by the total number of points lost.

Example: If a UCP 1000 vessel has lost 5 Lifespan and 3 Drivespan, it will take {1000*(5+3)} 8000 engineer-hours to overhaul.

Professional Overhaul Crews

The costs of hiring another staff from a starbase to do the work are outlined on the right. The table is explained as follows:

• Starport Class is the class of the starport where the work is being requested.
• Cost/hr. is the cost per engineer-hour of labour required and is not the cost per the total number of hours required (which is usually much less than the total number of engineer hours!).
• Schedule is the number of hours per day that will be devoted to working on the overhaul. See below for the total time taken.
• Staffing is the number of engineers that will be assigned to do the overhauls (rounded to nearest). There is always a minimum of 1 engineer assigned. For instance, if you bring a UCP 2500 starship to a Class B starport for overhaul, the starport will assign {2500/25} 100 skilled engineers to do the overhaul work on each shift.

Calculating the time taken to complete an overhaul is thus a matter of figuring out the total number of engineer hours needed, dividing that by the number of engineers assigned, and then dividing that by the schedule number to determine the total number of days needed for the overhaul to be completed. Any fraction of a day is truncated and multiplied by the schedule number to determine the number of hours it takes on the final day after work begins.

While a unit is in overhaul, it is completely powered down and unfueled; all personnel that normally serve aboard the unit will have to obtain temporary lodging at the starport's hostels. Note that while the unit is emptied of fuel, fuel that was in the tanks before the overhaul will be replenished back into the tank upon completion (if you wish, the tanks can be completely refilled after the overhaul process for standard price with no added time required).

Example: A UCP 440 Corsair with 11 lost points of Reliability is brought into a Class A Starport for overhaul. The Corsair will require 1.1% of its base cost in parts and materials, equal to {138,740,000*0.011} 1,526,140 Cr, in order to complete the overhaul. In addition to the cost of parts and materials, the Corsair also requires {11*440} 4,840 engineer hours to complete the work, which is a further cost of {4840*100} 484,000 Cr in labour. The starport decides that a UCP 440 vessel needs {440/20} 22 skilled engineers in each shift and assigns them to the task. The Corsair thus spends {4840/22/24} 9 days in port, with 0.16667 work days left over. Those 0.16667 days left over work out to {0.16667*24} 4 hours on the final day of labour. At the end of the overhaul, the players fly off a little lighter in the pocket but with a much more reliable vessel.

Independent Overhaul Crews

Characters can also perform overhauls themselves. The task for attempting an engineer-day (8 engineer-hours) of overhaul work is as follows:

Note, of course, that independently overhauling your unit still requires the investment in the parts and materials needed to do the work. You cannot overhaul your vessel in the middle of deep space unless you have a cargo hold full of parts and sheet metal. In all likelihood you will have to put down at a commercial starport to find sufficient supplies of the parts and materials in the first place.

Also note that this task is not absolute. If not important, assume the task is 8 hours absolute. If important, roll time dice and apply DMs as appropriate to determine how much time it takes the person attempting the task to accomplish the effective work.

E.g.; Bartley has Gravitics-1 and access to a well-stocked automotive shop (DM +1). He is tasked with quickly overhauling an air/raft so that he and his comrades can get out of the city before the subsector police arrive to serve a warrant for their (wrongful) arrest. He rolls 2D6 for task success, achieving 7—2 points above the 5+ needed—and performing nine hours' effective work according to the rules. He then rolls 3D6 for the time—a 10—and subtracts the DMs (2 altogether) to get 8, then multiplies by the time interval (1 hour) to get 8 hours. Bartley has thus subtracted 9 engineer-hours from the time required, taking eight hours to do so.

Bartley immediately gets to work again (succeeding in his Determination roll), rolling 2D6 for task success—achieving a 9 and performing 10 more engineer-hours' effective work. He rolls 3D6 for the time interval, achieving a staggering 4, and subtracts DMs (2) to get 2, set to the minimum possible of 3. Over a span of three more hours, Bartley has achieved 10 more engineer-hours' effective work! After just 11 hours, the vehicle is completely overhauled and Bartley and crew high-tail it out of the city.

Optional Rule: Proportional Cost

Vessels with higher sums of reliability will last longer but will be much more expensive to overhaul -- for instance, if a vehicle has only Reliability 2, that reliability will be spent within a few weeks of continuous use and the vehicle will only require 0.2% of its total cost to repair. As an alternative, you may consider a flat percentage cost for overhauling. Simply compute the ratio of RP lost to total RP; divide RP lost by the maximum RP, yielding an number from 0 to 1, and that will be the percentage cost of the overhaul. For instance, if a vehicle has 10 RP and is currently missing 7 RP, it will cost {(7/10)%} 0.7% of its total cost for spare parts and materials to overhaul. If a vehicle has 50 RP and is currently missing 7 RP, on the other hand, it will only cost {(7/50)%} 0.14% of its total cost for spare parts and materials. This makes more reliable vessels considerably more cost-effective.

Example

CraftID: Confire "Meridian" Luxury Landvan, TL8
   Cost: Cr91,808 (Adj), Cr77,150 (Base)
   Hull: 2/6, Disp = 2.5, Config = 4SL, Armour = 4B,
         Unloaded = 3858 kg, Loaded = 6327 kg
  Power: 1/2, ImprovedInternalCombustion = 200 kW, Duration = 0.83/2.5
   Loco: 1/2, Wheeled, P/W=32, OnRoad=121km/h, OffRoad=40km/h
  Commo: Radio = Regional, Laser = Distant
Sensors: LightAmplif, Headlight ×2, PassiveIR
    Off: None
    Def: None
Control: Panel = Electronic ×13
         Environ = basic env, basic ls
 Accomm: Crew = 1 (Operator = 1), Seats = Roomy × 6
  Other: Cargo = 1,969 litres, Fuel = 500 litres Hydrocarbons
         ObjSize = Small, EmLvl = Moderate
         * Environment and life support applies only to seating area.
         * Cargo area enclosed, but inaccessible from interior of vehicle and
           has no life support.
         * Price does not include fuel.  Filling tank costs 125 Cr.
Reliabl: 25, Lifespan = 10, Drivespan = 5, Durability = 10

The Meridian landvan has a Relability of 25 points. It has a Lifespan of 10, a Drivespan of 5, and a Durability of 10.

This equates to the following:

• The Meridian can run its engine for a cumulative total of 1200 hours before it begins to suffer failures. Assuming it is used only 5 hours per week (like a 21st-century-Earth passenger vehicle), the van will last over 4 years and 6 months before potentially experiencing breakdowns.
• Meridian vans can drive for 500,000 kilometres total before the suspension or transmission begins to suffer failures.
• After exceeding these operation periods, Meridian vans have a DM of -2 on all failure throws, meaning that the van only breaks down on a throw of 3- on 2d6. This is only an 8.3% chance per 120-hour or 10,000-kilometre trip.

Confire warrants their Meridian vans for 10 years/1,000,000 kilometres, so there will be repairs during the warranty period. The first time a Meridian is brought in for servicing, all lost points of Reliability will be overhauled (free of charge to the owner). Thereafter, the company will simply repair malfunctions as they come up (again, free of charge to the owner) until the warranty period expires.

Design Suggestions

• For units that will see continuous use while only occasionally moving, like starships, Lifespan is clearly the more important statistic, and you might consider giving only 5 points to Drivespan and dividing the remainder as evenly as possible between Lifespan and Durability as possible (but bearing in mind that Durability can't be greater than Lifespan).

• For units that will see periodic use and will travel great distances during this use, like ground vehicles that are the subordinate craft of starships, Drivespan is more important, but not majorly so. Consider giving anywhere from one-and-a-half times as many points up to 2 times as many points to Drivespan as you do to Lifespan, with Durability taking on a number at least equal to the lowest of Lifespan or Drivespan and preferably equal to the highest.

• Durability is an extremely valuable stat, particularly because it doesn't deteriorate until the vehicle is past due for an overhaul. Try to give designs as much Durability as possible.

Default Reliability

For the designs that come with the game (such as those presented in Fighting Ships of the Third Imperium, COACC, and/or the Imperial Encyclopedia), assume that they have the default number of Reliability Points, and assume that the points have been allocated according to the following chart. You may alternatively assign numbers of Reliability points and recalculate their prices as you see fit, if you have time and are willing to make the effort.

Tech Level   Reliability   Life  Driv  Dura   Pattern
-----------  ------------  ----  ----  ----   --------------------
  Pre/Early Stellar:
       TL6             2     1     0     1    +1 Life, +1 Dura
       TL7             4     2     1     1    +1 Life, +1 Driv
       TL8             6     3     1     2    +1 Life, +1 Dura
       TL9             8     3     2     3    +1 Driv, +1 Dura
      TL10            10     4     2     4    +1 Life, +1 Dura
  Stellar:
      TL11            12     5     2     5    +1 Life, +1 Dura
      TL12            14     6     3     5    +1 Life, +1 Driv
      TL13            16     7     3     6    +1 Life, +1 Dura
      TL14            18     7     4     7    +1 Driv, +1 Dura
      TL15            20     8     4     8    +1 Life, +1 Dura
  Hypothetical:
      TL16            22     9     4     9    +1 Life, +1 Dura
      TL17            24    10     5     9    +1 Life, +1 Driv
      TL18            26    11     5    10    +1 Life, +1 Dura
      TL19            28    11     6    11    +1 Driv, +1 Dura
      TL20            30    12     6    12    +1 Life, +1 Dura

Tech levels above TL20 can be made by continuing the pattern.
Tech levels below TL6 have a default Reliability of zero.