Ignition!

Ignition is a plugin for Kerbal Space Program which provides a simple framework for maintaining consistent propellant mixtures across fuel tanks, engines and RCS thrusters, as well as providing a basic simulation of the performance of propellant combinations and the use of resources for ignition. This plugin was developed specifically for the mod Chemical Propulsion, but is designed in a generic way and may find uses elsewhere.

Features

Supported

• Configurable engine ignitors which can require a resource
• Automated computation of bipropellant ignition potential, mixture ratio, thrust multiplier and Isp multiplier
• User-definable override propellant mixtures
• Monopropellant fuel tanks, engines and RCS thrusters
• Bipropellant fuel tanks, engines and RCS thrusters
• Jet engines

Planned

• Tripropellants and more

Usage

IgnitionPropellantConfig

Any resource used as a propellant by Ignition requires a IgnitionPropellantConfig defined in any .cfg file anywhere in your GameData directory, which takes the following fields: - name: Name of the resource to use. - IsOxidizer: Whether this resource acts as the oxidizer in a fuel-oxidizer bipropellant. false (fuel) by default. - MixtureConstant: A dimensionless quantity used to determine mixture ratios of bipropellants. - ThrustMultiplier: Vacuum thrust multiplier, scaled by proportion in a bipropellant mixture. - IspMultiplier: Vacuum Isp multiplier, scaled by proportion in a bipropellant mixture. - IgnitionPotential: A dimensionless quantity representing how readily the propellant will ignite with another, scaled by proportion in a bipropellant mixture.

For example, consider the following set of three propellants:

IgnitionPropellantConfig
{
    name = Hydrazine
    MixtureConstant = 5
    ThrustMultiplier = 1.05
    IspMultiplier = 1.12
    IgnitionPotential = 1.2
}
IgnitionPropellantConfig
{
    name = NTO
    IsOxidizer = true
    MixtureConstant = 6
    ThrustMultiplier = 1.05
    IspMultiplier = 0.92
    IgnitionPotential = 1.2
}
IgnitionPropellantConfig
{
    name = LqdOxygen
    IsOxidizer = true
    MixtureConstant = 5
    ThrustMultiplier = 1
    IspMultiplier = 1
    IgnitionPotential = 0.6
}

Any engine set up using Hydrazine and NTO or Hydrazine and LqdOxygen will identify the presence of both a fuel and an oxidizer and create a bipropellant engine. If both NTO and LqdOxygen are present, only the first propellant will be used, since the use of multiple propellants of the same kind in a single engine is not currently supported.

All final computed parameters for the engine will be rounded to sensible levels of precision. Bipropellant mixture ratios in particular are computed by rounding the ratio of the two MixtureConstants to the nearest multiple of 0.0625 or 0.1, whichever is closer. In this case, Hydrazine+NTO have a 5:6 ratio which is rounded to 7:9 = 0.4375:0.5625, while Hydrazine+LqdOxygen yields 5:5 = 1:1. The thrust multiplier, isp multiplier and ignition potential in the NTO case are calculated as follows: - Thrust: 1.05^0.4375 * 1.05^0.5625 = 1.05 - Isp: 1.12^0.4375 * 0.92^0.5625 = ~1.003 - Ignition potential: 1.2^0.4375 * 1.2^0.5625 = 1.2 And in the LqdOxygen case: - Thrust: 1.05^0.5 * 1^0.5 = ~1.025 - Isp: 1.12^0.5 * 1^0.5 = ~1.058 - Ignition potential: 1.2^0.5 * 0.6^0.5 = ~0.849

The thrust and isp multipliers are applied to the base stats of the engine, while the ignition potential is used to determine whether the engine ignites. Hydrazine+NTO yield an ignition potential of 1.2, which is greater than 1, so this combination ignites hypergolically. Hydrazine+LqdOxygen only reaches ~0.849, so cannot ignite alone and require additional ignition potential from a ModuleIgnitor (see below).

IgnitionPropellantCombinationConfig

The automatic computation of propellant combinations described above can be overridden by defining a IgnitionPropellantCombinationConfig with the following fields: - Any number of PROPELLANT nodes, though currently only monopropellants and bipropellants are supported. - ThrustMultiplier: Total vacuum thrust multiplier. - IspMultiplier: Total Isp thrust multiplier. - IgnitionPotential: Total ignition potential.

IgnitionPropellantCombinationConfig
{
    PROPELLANT
    {
        name = LqdHydrogen
        ratio = 3
        drawStackGauge = True
    }
    PROPELLANT
    {
        name = LqdOxygen
        ratio = 1
    }
    IspMultiplier = 1.4
    ThrustMultiplier = 0.8
    IgnitionPotential = 0.7
}

Controller modules

Controller modules are used to modify engine modules, RCS modules, and resources on a part. Each type of controller module can be configured with the following fields: - moduleID = Unique id of this module. - propellantModuleID = Unique id of a ModuleIgnitionPropellant used by this controller module (see below). Any number of propellantModuleID fields is allowed.

ModuleIgnitionEngineController

Controls propellant combinations and ignition simulation for a ModuleEngines with the following fields: - engineID = Unique id of the targeted engine module. Must be specified for a part with multiple engine modules, can be omitted otherwise.

The engine controller can be configured with any number of IGNITION_RESOURCEs, with the following fields: - name = Name of the resource to use. - Amount = Absolute amount of resource to use. - ScaledAmount = Approximate amount of resource scaled to the max mass flow rate of the engine, used if Amount is not defined. - AddedIgnitionPotential = Ignition potential added to that computed from the propellant combination, used if the engine is configured with Ignition propellants. - AlwaysRequired = Whether the ignitor resource is required regardless of the total ignition potential (default is false).

In the Hydrazine+LqdOxygen case above, the following ignitor would provide enough additional ignition potential to bring the total above 1 and achieve ignition.

MODULE
{
    name = ModuleIgnitionEngineController
    IGNITION_RESOURCE
    {
        name = ElectricCharge
        ScaledAmount = 0.1
        AddedIgnitionPotential = 0.5
    }
}

In a simplified case using a traditional engine without Ignition-configured propellants, a required ignitor can be added like so:

MODULE
{
    name = ModuleIgnitionEngineController
    IGNITION_RESOURCE
    {
        name = ElectricCharge
        Amount = 10
        AlwaysRequired = true
    }
}

ModuleIgnitionRCSController

Controls propellant combinations for a ModuleRCS with the following fields: - moduleID = Unique id of this module.

RCS controllers cannot be configured with an ignitor resource.

ModuleIgnitionTankController

Controls propellant combinations and ignition simulation of a ModuleEngines with the following fields: - moduleID = Unique id of this module. - volume = Total volume for propellant storage in liters NOT stock KSP units of five-liters. - addedMass = Mass added to the part, not counting any resources. - addedCost = Cost added to the part, not counting any resources.

ModuleIgnitionPropellant

ModuleIgnitionPropellant is used to inject propellants into a controller module and take advantage of all of Ignition's automatic performance computation. It has the following fields: - moduleID: Optional arbitrary string identifier. - resourceName: Name of the resource to use, used to look up the corresponding IgnitionPropellantConfig or IgnitionPropellantCombinationConfig where applicable. - ratio: Fixed ratio to override auto-computed mixture ratios. Ratio should be specified on either all the propellants or none of them. Useful for e.g. jet engines with a switchable fuel but a fixed fuel:IntakeAir ratio. - drawStackGauge: Whether this propellant should be used for the volume gauge on the staging panel. - ignoreForIsp: Whether this propellant should be ignored in thrust and isp computations, e.g. for the IntakeAir above.

A propellant module can be used by any number of controller modules. For example, with the propellant configs defined above, the following modules added to the LFB KR-1x2 "Twin-Boar" would convert the engine to run on 3 Kerosene : 5 LqdOxygen and change the in-built tanks to contain a total volume of 32,000 litres of propellant split into 12,000 Kerosene and 20,000 LqdOxygen:

MODULE
{
    name = ModuleIgnitionPropellant
    moduleID = fuel
    resourceName = Kerosene
}
MODULE
{
    name = ModuleIgnitionPropellant
    moduleID = oxidizer
    resourceName = LqdOxygen
}
MODULE
{
    name = ModuleIgnitionEngineController
    propellantModuleID = fuel
    propellantModuleID = oxidizer
}
MODULE
{
    name = ModuleIgnitionTankController
    volume = 32000
}

This design allows for flexibility in the control of the tank volume and propellant combination via ModuleManager patches and switches, for example B9PartSwitch could be used to change the fuel like so:

MODULE
{
    name = ModuleB9PartSwitch
    SUBTYPE
    {
        name = Kerosene
        title = Kerosene
        MODULE
        {
            IDENTIFIER
            {
                name = ModuleIgnitionPropellant
                moduleID = fuel
            }
            DATA
            {
                resourceName = Kerosene
            }
        }
    }
    SUBTYPE
    {
        name = LH2
        title = Liquid Hydrogen
        MODULE
        {
            IDENTIFIER
            {
                name = ModuleIgnitionPropellant
                moduleID = fuel
            }
            DATA
            {
                resourceName = LqdHydrogen
            }
        }
    }
}

Dependencies

• ModuleManager (4.2.3)

License

Distributed under the GNU General Public License.

Special thanks

This is the first plugin I've made for Kerbal Space Program, which was possible with help from several people in the KSP Modding Society Discord server, including but not limited to Greatspace2019KSP, Halbann, HB Stratos, JohnnyOThan, and especially JadeOfMaar.

The engine ignitor logic was loosely based on the mod EngineIgnitor, so thanks also to HoneyFox, Riocrokite, DennyTX and linuxgurugamer for their work on that plugin!