Add general planetary info

doc/RTD/source/EquationOfState/index.rst

 .. Equations of State
    Loic Hausammann, 6th April 2018
-   Jacob Kegerreis, 3rd February 2019
+   Jacob Kegerreis, 13th March 2020
 
 .. _equation_of_state:
 
@@ -50,6 +50,9 @@ density-entropy scheme or the internal enegy in a density-energy SPH
 formulation) written to the snapshots is meaningless. The pressure,
 however, is always correct in all scheme.
 
+
+.. _planetary_equation_of_state:
+
 Planetary EoS
 -------------
 Configuring SWIFT with the ``--with-equation-of-state=planetary`` and 
@@ -63,15 +66,15 @@ So far, we have implemented several Tillotson, SESAME, and Hubbard \& MacFarlane
 The material's ID is set by a base type ID (multiplied by 100), plus a minor 
 type:
 
-+ Tillotson (Melosh, 2007): ``1``
++ Tillotson (Melosh, 2007): Base type ``1``
     + Iron: ``100``
     + Granite: ``101``
     + Water: ``102``
-+ Hubbard \& MacFarlane (1980): ``2``
++ Hubbard \& MacFarlane (1980): Base type ``2``
     + Hydrogen-helium atmosphere: ``200``
     + Ice H20-CH4-NH3 mix: ``201``
     + Rock SiO2-MgO-FeS-FeO mix: ``202``
-+ SESAME (and similar): ``3``
++ SESAME (and similar): Base type ``3``
     + Iron (2140): ``300``
     + Basalt (7530): ``301``
     + Water (7154): ``302``
@@ -82,14 +85,15 @@ do not always include transformations between the internal energy,
 temperature, and entropy. At the moment, we have only implemented 
 \\(P(\\rho, u)\\) and \\(c_s(\\rho, u)\\). 
 This is sufficient for the simple :ref:`planetary_sph` hydrodynamics scheme, 
-but makes these materials currently incompatible with other entropy-based 
-schemes.
+but makes these materials currently incompatible with entropy-based schemes.
 
 The Tillotson sound speed was derived using 
 \\(c_s^2 = \\left. \\dfrac{\\partial P}{\\partial \\rho} \\right|_S \\)
-as described in Kegerreis et al. (2019).
+as described in `Kegerreis et al. (2019) <https://doi.org/10.1093/mnras/stz1606>`_.
 The table files for the HM80 and SESAME-style EoS can be downloaded using 
-the ``examples/EoSTables/get_eos_tables.sh`` script.
+the ``swiftsim/examples/EoSTables/get_eos_tables.sh`` script.
+
+See :ref:`planetary` for other related information.
 
 
 How to Implement a New Equation of State

doc/RTD/source/HydroSchemes/index.rst

@@ -15,7 +15,7 @@ schemes available in SWIFT, as well as how to implement your own.
 
    traditional_sph
    minimal_sph
-   planetary
+   planetary_sph
    hopkins_sph
    anarchy_sph
    sphenix_sph

doc/RTD/source/HydroSchemes/minimal_sph.rst

 .. Minimal SPH
    Josh Borrow 4th April 2018
 
+.. _minimal:
+
 Minimal (Density-Energy) SPH
 ============================
 

doc/RTD/source/HydroSchemes/planetary.rst → doc/RTD/source/HydroSchemes/planetary_sph.rst

 .. Planetary SPH
-    Jacob Kegerreis, 3rd February 2019
+    Jacob Kegerreis, 13th March 2020
 
 .. _planetary_sph:
 
@@ -11,9 +11,12 @@ Planetary (Density-Energy, Multi-Material) SPH
    :hidden:
    :caption: Contents:
 
-This scheme is the same as the Minimal SPH scheme but also allows multiple 
+This scheme is based on the :ref:`minimal` scheme but also allows multiple 
 materials, meaning that different SPH particles can be assigned different 
-:ref:`equation_of_state` (EoS).
+:ref:`equation_of_state` (EoS). 
+
+The Balsara viscosity switch is also used, but can be disabled by 
+compiling SWIFT with ``make CFLAGS=-DPLANETARY_SPH_NO_BALSARA``.
 
 To use the planetary scheme and the corresponding planetary EoS, use 
 
@@ -23,4 +26,6 @@ To use the planetary scheme and the corresponding planetary EoS, use
 
 Every SPH particle then requires and carries the additional ``MaterialID`` flag 
 from the initial conditions file. This flag indicates the particle's material 
-and which EoS it should use. 
\ No newline at end of file
+and which EoS it should use. 
+
+See :ref:`planetary` for other related information.

doc/RTD/source/Planetary/index.rst

+.. Planetary Simulations
+   Jacob Kegerreis, 13th March 2020
+
+.. _planetary:
+   
+Planetary Simulations
+=====================
+
+SWIFT is also designed for running planetary simulations
+with a focus on giant impacts, as presented in 
+`Kegerreis et al. (2019) <https://doi.org/10.1093/mnras/stz1606>`_, MNRAS 487:4.
+
+New features for planetary simulations are in active development
+so please let us know if you are interested in using SWIFT 
+or have any implementation requests. For example a new equation of state
+or extensions to the tools for creating initial conditions.
+    
+You can find an example simulation in ``swiftsim/examples/Planetary/``
+under ``EarthImpact/``.
+The tabulated equations of state files can be downloaded using 
+``EoSTables/get_eos_tables.sh``.
+
+Planetary simulations are currently intended to be run with 
+SWIFT configured to use the planetary hydrodynamics scheme and equations of state:
+``--with-hydro=planetary`` and ``--with-equation-of-state=planetary``.
+These allow for multiple materials to be used,
+chosen from the several available equations of state (more coming soon!).
+See :ref:`planetary_sph` and :ref:`planetary_equation_of_state` for more details.

doc/RTD/source/index.rst

@@ -23,6 +23,7 @@ difference is the parameter file that will need to be adapted for SWIFT.
    TimeStepping/index
    SubgridModels/index
    random
+   Planetary/index
    FriendsOfFriends/index
    EquationOfState/index
    ExternalPotentials/index