Additional orbit properties #717
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## master #717 +/- ##
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+ Coverage 86.09% 86.14% +0.04%
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Files 52 52
Lines 2640 2648 +8
Branches 221 221
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+ Hits 2273 2281 +8
Misses 310 310
Partials 57 57
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| orbit = Orbit.from_classical(attractor, a, ecc, _a, _a, _a, nu) | ||
| orbit_M = orbit.M | ||
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| assert_allclose(orbit_M.value, expected_mean_anomaly.value, rtol=1e-2) |
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There is an assert_quantity_allclose in Astropy that you can use https://astropy.readthedocs.io/en/stable/api/astropy.tests.helper.assert_quantity_allclose.html
| orbit = Orbit.from_classical(attractor, a, ecc, _a, _a, _a, nu) | ||
| orbit_h_mom = orbit.h_mom | ||
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| assert_allclose(orbit_h_mom.value, expected_ang_mom.value, rtol=1e-2) |
| nu = 120 * u.deg | ||
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| orbit = Orbit.from_classical(attractor, a, ecc, _a, _a, _a, nu) | ||
| orbit_h_mom = orbit.h_mom |
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Not a fan of h_mom, what about h_mag (of "magnitude")?
| orbit = Orbit.from_classical(attractor, a, ecc, _a, _a, _a, nu) | ||
| orbit_t_p = orbit.t_p | ||
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| assert_allclose(orbit_t_p.value, expected_t_p.value, rtol=1e-2) |
src/poliastro/twobody/orbit.py
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| @property | ||
| def h_mom(self): | ||
| """Angular momentum. """ | ||
| h_mom = np.linalg.norm(self.h_vec) * u.km ** 2 |
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Instead of using np.linalg.norm, you can use poliastro.util.norm, which respects the units
src/poliastro/twobody/orbit.py
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| @@ -216,12 +216,29 @@ def h_vec(self): | |||
| h_vec = np.cross(self.r.to(u.km).value, self.v.to(u.km / u.s)) * u.km ** 2 / u.s | |||
| return h_vec | |||
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| @property | |||
| def h_mom(self): | |||
| """Angular momentum. """ | |||
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Notice that this is the specific angular momentum. In mechanics, they call "specific" to the magnitudes without mass, like this case, see https://www.wikiwand.com/en/Specific_relative_angular_momentum
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Merging, thanks! |
Adds 3 orbit properties:
Angular momentum
Mean anomaly
Time elapsed from last perifocal passage
Tests taken from Curtis, H. D. (2005). Orbital mechanics for engineering students, p115, Example 3.1