# Announcing two extensions to ModelingToolkit.jl

**URL:** https://discourse.julialang.org/t/announcing-two-extensions-to-modelingtoolkit-jl/62445
**Category:** Package Announcements
**Tags:** package, modelingtoolkit
**Created:** [June 5, 2021, 5:08pm UTC](https://discourse.julialang.org/t/announcing-two-extensions-to-modelingtoolkit-jl/62445 "2021-06-05T17:08:45Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![cadojo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cadojo/32/25328_2.png) [@cadojo](https://discourse.julialang.org/u/cadojo)
#### Post date: [June 5, 2021, 5:08pm UTC](https://discourse.julialang.org/t/announcing-two-extensions-to-modelingtoolkit-jl/62445/1 "2021-06-05T17:08:45Z")

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I’ve been rewriting all of my hard-coded dynamics with [ModelingToolkit.jl](https://github.com/SciML/ModelingToolkit.jl). Here are two new extensions! They are set to automerge into the General registry in 3 days.

#### Astrodynamics

See [AstrodynamicalModels.jl](https://github.com/cadojo/AstrodynamicalModels.jl) for restricted two-body and circular-restricted three-body dynamics (the latter includes local linearization dynamics). More to come!

#### NASA’s GTM

[Chakraborty et al](https://www.sciencedirect.com/science/article/abs/pii/S0967066110002595)  
published a polynomial approximation for longitudinal GTM dynamics. This approximation is available at [PolynomialGTM.jl](https://github.com/cadojo/PolynomialGTM.jl). I feel this would be a cool test bed for control theory Pluto notebooks, I’m hoping to make some of those this summer!