diff --git a/tests/orbit_test.cpp b/tests/orbit_test.cpp index acd12fd..4bdac15 100644 --- a/tests/orbit_test.cpp +++ b/tests/orbit_test.cpp @@ -66,3 +66,58 @@ TEST_CASE("orbital period", "[orbits]") double T = orbitGetPeriod(a, mu); REQUIRE_THAT(T, WithinAbs(37863.5, 50e-3)); } + +// NOTE: example 4.1 in "Space Flight Dynamics" by Craig A. Kluever +TEST_CASE("time of flight example 4.1 a", "[orbits]") +{ + double a = 26564.5; // semi-major axis in km + double e = 0.7411; // eccentricity + double mu = 398601.68; // gravitational parameter + double r = 6378; // body radius in km + system_2body sys = systemInit(gravBodyInit(mu, r), orbitInit(a, e)); + + // NOTE: get ToF from periapsis to true anomaly at 154.85 degrees + double theta_0 = 0.0; + double theta_1 = 154.85 * M_PI / 180; + + double n = getMeanMotion(sys.body.mu, sys.ep.a); + REQUIRE_THAT(n, WithinAbs(0.00014582, 1e-8)); + + double ecc_1 = getEccAnomFromTrueAnom(sys.ep.e, theta_1); + REQUIRE_THAT(ecc_1, WithinAbs(2.0927, 1e-4)); + + // NOTE: we really want < 33ms accuracy here, but either there's floating + // point error, or the examples in the book are incorrect or just not + // precise enough + double tof = orbitGetTimeOfFlight(sys, theta_0, theta_1); + REQUIRE_THAT(tof, WithinAbs(9945.2, 0.5)); +} + +TEST_CASE("time of flight example 4.2", "[orbits]") +{ + double a = 26564.5; // semi-major axis in km + double e = 0.7411; // eccentricity + double mu = 398601.68; // gravitational parameter + double r = 6378; // body radius in km + system_2body sys = systemInit(gravBodyInit(mu, r), orbitInit(a, e)); + + // NOTE: get ToF from periapsis to true anomaly at 154.85 degrees + double theta_1 = 230 * M_PI / 180; + double theta_2 = 120 * M_PI / 180; + + double n = getMeanMotion(mu, a); + REQUIRE_THAT(n, WithinAbs(0.00014582, 1e-8)); + + double ecc_1 = getEccAnomFromTrueAnom(e, theta_1); + REQUIRE_THAT(orbitClampAngle(ecc_1), WithinAbs(4.9012, 1e-4)); + + double M1 = getMeanAnomFromEccAnom(ecc_1, e); + REQUIRE_THAT(orbitClampAngle(M1), WithinAbs(5.6291, 1e-4)); + + double ecc_2 = getEccAnomFromTrueAnom(e, theta_2); + REQUIRE_THAT(orbitClampAngle(ecc_2), WithinAbs(1.1778, 1e-4)); + + // NOTE: see note in example 4.1 above about accuracy + double tof = orbitGetTimeOfFlight(sys, theta_1, theta_2); + REQUIRE_THAT(tof, WithinAbs(7867.5, 2 * 0.5)); +}