feat(astro): apsis radii from orbital elements#403
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Add orbit::apoapsis_radius_from_elements(a, e) = a*(1+e) and periapsis_radius_from_elements(a, e) = a*(1-e), the farthest and closest orbital radii (m) from the conic elements. Together they are the forward (a, e) -> apsides direction, completing the apsides<->elements bijection: eccentricity_from_apsides (#372) and semi_major_axis_from_apsides (#378) go apsides -> (e, a); these go (a, e) -> apsides. Guard mirrors semi_latus_rectum_from_elements (a > 0, 0 <= e < 1). Analytic test apsis_radius_from_elements_completes_the_apsides_bijection: (a) worked a=7e6, e=0.1 -> r_a=7.7e6, r_p=6.3e6; (b) double round-trip threading #372 + #378 (non-tautological): the computed apsides recover BOTH e and a; (c) threads semi_latus_rectum_from_elements (#384): the harmonic mean of the apsides is the semi-latus rectum p = a(1-e^2); (d) ordering r_p <= a <= r_a and r_a + r_p = 2a; (e) circular: e=0 -> both apsides collapse to a; (f) Err guards for a<=0, e>=1, non-finite (both fns). Free fns in orbit.rs (reached via valenx_astro::orbit::), no lib.rs change. valenx-astro 222 lib tests (was 221), cargo clippy --all-targets -D warnings clean.
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Add report::mach_from_stagnation_pressure_ratio(p0_over_p, gamma), the Mach number recovered from a measured total-to-static pressure ratio: M = sqrt(2*((p0/p)^((gamma-1)/gamma) - 1)/(gamma - 1)) the inverse of isentropic_stagnation_pressure_ratio -- the SUBSONIC pitot-static (Rayleigh-pitot) airspeed reduction, the most common compressible airspeed measurement. Mirrors the #403 temperature-ratio inverse's sentinel style: returns the at-rest 0.0 (the inverse of the ratio's 1.0 no-rise identity) for non-physical input (non-finite, p0/p < 1, or gamma <= 1). Analytic test mach_from_stagnation_pressure_ratio_inverts_the_ratio: (a) round-trip threading isentropic_stagnation_pressure_ratio (both directions); (b) worked: at M=1, gamma=1.4 the critical ratio p0/p = 1.2^3.5 -> M=1; (c) consistency with the temperature-ratio inverse (#403): for the same Mach, the pressure-ratio and temperature-ratio reductions agree; (d) at rest: p0/p = 1 -> M = 0; (e) 0-sentinel guard for p0/p < 1, gamma <= 1, non-finite. Free fn in report.rs (not re-exported), no lib.rs change. valenx-aero 213 lib tests (was 212), cargo clippy --all-targets -D warnings clean.
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…421) Add report::mach_from_stagnation_density_ratio(rho0_over_rho, gamma), the Mach number recovered from a measured total-to-static density ratio: M = sqrt(2*((rho0/rho)^(gamma-1) - 1)/(gamma - 1)) the inverse of isentropic_stagnation_density_ratio. With the temperature- (#403) and pressure-ratio (#409) inverses it completes the stagnation- ratio inverse trio. Mirrors their sentinel style: returns the at-rest 0.0 (the inverse of the ratio's 1.0 no-compression identity) for non-physical input (non-finite, rho0/rho < 1, or gamma <= 1). Analytic test mach_from_stagnation_density_ratio_inverts_the_ratio: (a) round-trip threading isentropic_stagnation_density_ratio (both directions); (b) worked: at M=1, gamma=1.4 the sonic ratio rho0/rho = 1.2^2.5 -> M=1; (c) consistency with the temperature- and pressure-ratio inverses: for the same Mach all three stagnation-ratio reductions return the same Mach; (d) at rest: rho0/rho = 1 -> M = 0; (e) 0-sentinel guard for rho0/rho < 1, gamma <= 1, non-finite. Free fn in report.rs (not re-exported), no lib.rs change. valenx-aero 214 lib tests (was 213), cargo clippy --all-targets -D warnings clean.
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What
Adds the apsis-radius pair from orbital elements:
Why
orbit.rshaseccentricity_from_apsides(#372) andsemi_major_axis_from_apsides(#378) — theapsides -> (e, a)inverses — but not the forward direction. These two complete the apsides <-> elements bijection:(a, e) -> apsides. Guard mirrorssemi_latus_rectum_from_elements(a > 0,0 <= e < 1).Test
apsis_radius_from_elements_completes_the_apsides_bijection:a=7e6, e=0.1 -> r_a=7.7e6, r_p=6.3e6;eanda;semi_latus_rectum_from_elements(chore(deps)(deps): bump sha2 from 0.10.9 to 0.11.0 #384) — the harmonic mean of the apsides is the semi-latus rectump = a(1-e^2);r_p <= a <= r_aandr_a + r_p = 2a;e=0 -> both apsides collapse to a;a<=0,e>=1, non-finite (both fns).Free fns in
orbit.rs(reached viavalenx_astro::orbit::), nolib.rschange.valenx-astro222 lib tests (was 221);cargo clippy -p valenx-astro --all-targets -- -D warningsclean. Research-grade two-body primitives.