Thrift struct comments

Comments about some thrift struct fields. Not all structs and fields are listed here, only when it's necessary.
Notes:
fields about length/distance are in meters
fields about time are in seconds
fields about temperature are in Kelvin
fields about mass are in Kg
fields about angles are in degrees
COM is short for "center of mass"
struct Vessel {
  5: double MET, // time elapsed since the mission starts
  6: i32 stage, // current stage
  7: string biome, // current biome the vessel is in
  15: optional map<string, observor.VesselResource> totalResources, // the whole vessel's resources
  16: optional map<string, observor.VesselResource> inUseResources, // the resources currently comsumed by parts
}

struct Orbit {
  2: double apoapsis, // the distance from the body's COM to apoapsis
  3: double periapsis, // the distance from the body's COM to periapsis
  4: double apoapsisAltitude, // the distance from sea level of the body to apoapsis
  5: double periapsisAltitude, // the distance from sea level of the body to periapsis
  8: double radius, // current distance from the body's COM to the orbiting object's COM
  9: double speed, // magnitude of velocity in world space
  10: double period, // orbital period
  13: double eccentricity, // https://en.wikipedia.org/wiki/Orbital_eccentricity
  14: double inclination, // https://en.wikipedia.org/wiki/Orbital_inclination
  15: double longitudeOfAscendingNode, // https://en.wikipedia.org/wiki/Longitude_of_the_ascending_node
  16: double argumentOfPeriapsis, // https://en.wikipedia.org/wiki/Argument_of_periapsis
  17: double meanAnomalyAtEpoch, // https://en.wikipedia.org/wiki/Mean_anomaly
  18: double epoch, // https://en.wikipedia.org/wiki/Mean_anomaly
  19: double meanAnomaly, // https://en.wikipedia.org/wiki/Mean_anomaly
  20: double eccentricAnomaly, // https://en.wikipedia.org/wiki/Eccentric_anomaly
  21: double trueAnomaly, // https://en.wikipedia.org/wiki/True_anomaly
  22: double timeToSOIChange, // the time after which the vessel will shift to another body's sphere of influence
  23: double orbitalSpeed, // magnitude of velocity which is relative to the body's COM
}

struct Part {
  4: i32 stage, // (Part.inverseStage)the stage the part appears in the actual stage GUI
  10: double maxTemperature, // the part will be detroyed if temperature is higher than maxTemperature
  11: double maxSkinTemperature, // the part will be detroyed if skin temperature is higher than maxSkinTemperature
  12: optional Resources resources, // resources contained in this part
}

struct CelestialBody{
  4: double gravitationalParameter, // https://en.wikipedia.org/wiki/Standard_gravitational_parameter
  5: double surfaceGravity, // sea level gravity
  6: double rotationalPeriod, // sidereal rotation period
  7: double rotationalSpeed, // sidereal rotational speed, in degrees per second
  8: double rotationAngle, // current body rotation angle, in degrees
  9: double initialRotation, // body rotation angle at UT 0, in degrees
  17: double flyingHighAltitudeThreshold, // a vessel is considered to be flying "high" in atmosphere above this altitude
  18: double spaceHighAltitudeThreshold, // a vessel is considered to be orbiting "high" in space above this altitude
}

struct TargetOrbitInfo {
  1: double closestApproachTime, // UT at which the distance between this object and target object is the closest
  2: double closestApproachDistance, // the distance at "closestApproachTime"
  3: double trueAnomalyAtAN, // angle of true anomaly at ascending node, in degrees, between 0 and 180
  4: double trueAnomalyAtDN, // angle of true anomaly at descending node, in degrees, between 0 and 180
  5: double relativeInclination, // angle of inclination relative to target's orbit, in degrees
}

struct ManeuverNode {
  3: Vector3d deltaVVector, // the planned deltaV vector, won't change
  4: double deltaV, // the planned deltaV magnitude, won't change, in m/s
  5: Vector3d remainingBurnVector, // the remaining deltaV vector, changes as the vessel is maneuvering
  6: double remainingDeltaV, // the magnitude of remaining deltaV vector, changes as the vessel is maneuvering
}

struct AttitudeInfo { // all the fields are from world reference frame, not normalized except prograde, normal and radial
  1: Vector3d position, // position in world space
  2: Vector3d direction, // the direction to which the vessel is pointing to in world space
  3: Vector3d velocity, // velocity in world space
  4: Vector3d prograde, // prograde direction of orbit in world space
  5: Vector3d normal, // normal direction of orbit in world space
  6: Vector3d radial, // radial direction of orbit in world space
  7: Vector3d up, // up direction in world space, equal to "direction"
  8: Vector3d forward, // forward direction in world space
  9: Vector3d right, // right direction in world space
  10: KQuaternionD rotation, // rotation in world space
}

struct Wheel {
  3: double radius, // wheel radius, in meters
  6: double brakeForce, // brake force percentage
  8: double manualFrictionControl, // only take effect when auto-friction-control is disabled
  11: bool powered, // true if the wheel is powered by motors
  15: double motorOutput, // current torque generated, in Newton meters.
  16: bool tractionControlEnabled, // can be enabled only when the wheel is powered by motors
  17: double tractionControl, // take effect if traction control is enabled
  18: double driveLimiter, // take effect if traction control is disabled
  27: double stress, // current stress on the wheel, in kPA
  28: double stressTolerance, // stress above which the wheel will be broken, in kPA
  29: double stressPercentage, // percentage of stress to tolerance
}

struct ConverterResource {
  // for example, ratios of input resource A and B are 0.3 and 0.7, 
  // then for each 1 unit output resource (in total), 0.3 units of A and 0.7 units of B are consumed.
  2: double ratio, 
}

struct Propellant {
  2: double currentAmount, //  current flow speed, in Units per second
  3: double currentRequirement, // current Maximum flow speed with current throttle, in Units per second
  4: double totalResourceAvailable, // total resource amount reachable 
  5: double totalResourceCapacity, // total resource capacity reachable 
  6: bool isDeprived, // whether the object has ran out of given resource
}

struct Engine {
  2: double thrust, // current thrust, in Newtons
  3: double maxVacuumThrust, // amount of thrust in vacuum with thrustPercentage set to 100%, in Newtons
  4: double thrustPercentage, // percentage to which the max thrust is limited
  5: double specificImpulse, // current specific impulse, in seconds
  6: double vacuumSpecificImpulse, // specific impulse in vacuum, in seconds
  7: double kerbinSeaLevelSpecificImpulse, // specific impulse at sea level at Kerbin
  9: map<string, Propellant> propellants, // propellants reachable and used by this engine
  11: double throttle, // current throttle, may be different from vessel's mainThrottle if the engine takes time to change
  15: bool hasModes, // true if this is a multi-mode engine
  20: double gimbalRange, // in degrees
  22: double gimbalLimit, // gimbal limit range, range from -100(reversed) to 100
}

struct Decoupler {
  1: bool decoupled, // true if fired
  2: bool stagingEnabled, // true if enabled in staging sequence
  3: double ejectionForce, // impulse, in Newton seconds
}

struct ControlSurface {
  4: double authorityLimiter, // the range it can move, in percentage
  7: double surfaceArea, // in m^2
}

struct Antenna {
  3: bool allowPartial, // true if partial data transmission is allowed
  5: bool combinable, // true if can be conbined with other antennas to increase signal strengh
  6: double combinableExponent, // the exponent used to calculate conbined power
  7: double packetInterval, // in second.
  8: double packetSize, // in Mits
  9: double packetResourceCost, // how many units of electricity is comsumed per packet
}

struct Resource {
  2: double capacity, // capacity amount of resource stored in this part
  3: double amount, // current amount of resource stored in this part
}