dcs-retribution/gen/flights/traveltime.py

121 lines
4.1 KiB
Python

from __future__ import annotations
import logging
import math
from datetime import timedelta
from typing import TYPE_CHECKING
from dcs.mapping import Point
from dcs.unittype import FlyingType
from game.utils import (
Distance,
SPEED_OF_SOUND_AT_SEA_LEVEL,
Speed,
kph,
mach,
meters,
)
from gen.flights.flight import Flight
if TYPE_CHECKING:
from gen.ato import Package
class GroundSpeed:
@classmethod
def for_flight(cls, flight: Flight, altitude: Distance) -> Speed:
if not issubclass(flight.unit_type, FlyingType):
raise TypeError("Flight has non-flying unit")
# TODO: Expose both a cruise speed and target speed.
# The cruise speed can be used for ascent, hold, join, and RTB to save
# on fuel, but mission speed will be fast enough to keep the flight
# safer.
# DCS's max speed is in kph at 0 MSL.
max_speed = kph(flight.unit_type.max_speed)
if max_speed > SPEED_OF_SOUND_AT_SEA_LEVEL:
# Aircraft is supersonic. Limit to mach 0.8 to conserve fuel and
# account for heavily loaded jets.
return mach(0.8, altitude)
# For subsonic aircraft, assume the aircraft can reasonably perform at
# 80% of its maximum, and that it can maintain the same mach at altitude
# as it can at sea level. This probably isn't great assumption, but
# might. be sufficient given the wiggle room. We can come up with
# another heuristic if needed.
cruise_mach = max_speed.mach() * 0.8
return mach(cruise_mach, altitude)
class TravelTime:
@staticmethod
def between_points(a: Point, b: Point, speed: Speed) -> timedelta:
error_factor = 1.1
distance = meters(a.distance_to_point(b))
return timedelta(hours=distance.nautical_miles / speed.knots * error_factor)
# TODO: Most if not all of this should move into FlightPlan.
class TotEstimator:
def __init__(self, package: Package) -> None:
self.package = package
@staticmethod
def mission_start_time(flight: Flight) -> timedelta:
startup_time = flight.flight_plan.startup_time()
if startup_time is None:
# Could not determine takeoff time, probably due to a custom flight
# plan. Start immediately.
return timedelta()
return startup_time
def earliest_tot(self) -> timedelta:
if not self.package.flights:
return timedelta(0)
earliest_tot = max(
(self.earliest_tot_for_flight(f) for f in self.package.flights)
)
# Trim microseconds. DCS doesn't handle sub-second resolution for tasks,
# and they're not interesting from a mission planning perspective so we
# don't want them in the UI.
#
# Round up so we don't get negative start times.
return timedelta(seconds=math.ceil(earliest_tot.total_seconds()))
@staticmethod
def earliest_tot_for_flight(flight: Flight) -> timedelta:
"""Estimate fastest time from mission start to the target position.
For BARCAP flights, this is time to race track start. This ensures that
they are on station at the same time any other package members reach
their ingress point.
For other mission types this is the time to the mission target.
Args:
flight: The flight to get the earliest TOT time for.
Returns:
The earliest possible TOT for the given flight in seconds. Returns 0
if an ingress point cannot be found.
"""
# Clear the TOT, calculate the startup time. Negating the result gives
# the earliest possible start time.
orig_tot = flight.package.time_over_target
try:
flight.package.time_over_target = timedelta()
time = flight.flight_plan.startup_time()
finally:
flight.package.time_over_target = orig_tot
if time is None:
logging.warning(f"Cannot estimate TOT for {flight}")
# Return 0 so this flight's travel time does not affect the rest
# of the package.
return timedelta()
return -time