Propagating 0 seconds with cowell fails

Currently we can only use the basic mean_method function to propagate orbits. As the Orbit.Sample() can now accept other propagators as well, we must be able to use cowell method as well. 🐞 Problem We can’t use the cowell’s method and other propagators to propagate the orbit because of differences in the parameters passed in the normal propagator while using Orbit.Sample().

🖥 Please paste the output of following commands

conda info -a

python -c "import poliastro.testing; poliastro.testing.test()" python3 -c “import poliastro.testing; poliastro.testing.test()” ============================= test session starts ============================== platform linux – Python 3.6.3, pytest-3.4.1, py-1.5.2, pluggy-0.6.0 rootdir: /home/shreyas/poliastro, inifile: setup.cfg plugins: cov-2.5.1 collected 141 items

poliastro/src/poliastro/tests/test_bodies.py … [ 4%] poliastro/src/poliastro/tests/test_coordinates.py … [ 6%] poliastro/src/poliastro/tests/test_hyper.py … [ 14%] poliastro/src/poliastro/tests/test_iod.py … [ 20%] poliastro/src/poliastro/tests/test_jit.py … [ 22%] poliastro/src/poliastro/tests/test_maneuver.py … [ 26%] poliastro/src/poliastro/tests/test_patched_conics.py … [ 28%] poliastro/src/poliastro/tests/test_plotting.py … [ 34%] poliastro/src/poliastro/tests/test_plotting3d.py … [ 39%] poliastro/src/poliastro/tests/test_stumpff.py … [ 41%] poliastro/src/poliastro/tests/test_twobody.py … [ 42%] poliastro/src/poliastro/tests/test_util.py … [ 47%] poliastro/src/poliastro/tests/tests_neos/test_dastcom5.py … [ 53%] poliastro/src/poliastro/tests/tests_neos/test_neos_neows.py … [ 58%] poliastro/src/poliastro/tests/tests_twobody/test_angles.py … [ 63%] poliastro/src/poliastro/tests/tests_twobody/test_decorators.py … [ 64%] poliastro/src/poliastro/tests/tests_twobody/test_orbit.py … [ 74%] … [ 78%] poliastro/src/poliastro/tests/tests_twobody/test_propagation.py … [ 83%] . [ 84%] poliastro/src/poliastro/tests/tests_twobody/test_sample.py … [ 92%] poliastro/src/poliastro/tests/tests_twobody/test_states.py … [100%]

========================= 141 passed in 21.47 seconds ==========================

🎯 Goal To be able to Propagate the orbit using different propagators.

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[astrojuanlu]

I think that iss.sample(method=cowell) won’t raise the error after this was merged:

https://github.com/poliastro/poliastro/pull/330

However, iss.propagate(0 * u.s, method=cowell) or iss.sample([0] * u.s, method=cowell) should do.

[astrojuanlu]

The original issue was, but the problem changed and we continued discussing it here:

https://github.com/poliastro/poliastro/issues/328#issuecomment-391666709

I need to think carefully on the API and which cases do we accept, and also there’s one doctest failing because of it (see #454), so I prefer to take care of it myself.