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LunaSim

Design and Run All-Powerful Simulations

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Why Was LunaSim Created?

"System dynamics modeling software allows the user to graphically describe and run simulations of real-world systems. My school's 9th Grade Foundations of Computer Science class uses this kind of software, where students learn about how modeling and simulation works and how it can be applied to the fields of engineering, physics, and biology.

Previously, my school used licensed, commercial (and expensive) software for systems modeling. A system-wide software upgrade made the previous modeling software at our school inoperable on Windows and school-issued Chromebooks, upending students' curriculum.

This motivated me to propose and lead the development of our app LunaSim, a free, open-source alternative that can be accessed from any computer with a standard browser, allowing students to use both the desktop computers and Chromebooks to build their simulations."

- Karthik Vedula, Original Co-Creator of LunaSim

What is LunaSim?

LunaSim is a free, open-source, browser-based system dynamics modeling software designed to make complex simulations accessible to students and educators. Built to replace expensive commercial alternatives, LunaSim enables users to create interactive models of real-world systems through an intuitive drag-and-drop interface. With features like stock-and-flow diagrams, custom equations/referencing, multiple integration methods, and comprehensive visualization tools, LunaSim has revolutionized how system dynamics is taught in classrooms worldwide.

Important Features

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    Reservoirs

    Stocks, conveyors, microwaves, and queues

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    Links

    Flows, influences, and overflows

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    Equations

    Arithmetic, trigonometry, and Java Math

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    References

    Node/link references and time references

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    Integration Methods

    Euler's method and Runge-Kutta 4

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    Visuals

    Charts and tables

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    Import/Export

    Save, reuse, and download models

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    Customization

    Themes, fonts, and keybinds

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    Uncertainty Analysis

    Monte Carlo simulation support

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    Live APIs

    Stock market, weather, and economics data

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    And Much More!

    Ghosting, logic, emphasis, polarity, and more

Our Team

Meet the passionate individuals behind LunaSim who are dedicated to revolutionizing system dynamics education.

Karthik Vedula

Karthik Vedula

Lead Programmer

school Stanford University
2021-2025
Aditya Patil

Aditya Patil

Systems Analyst / Lead Tester

school University of Maryland
2023-2025
Sienna Simms

Sienna Simms

Project Manager / Lead Tester

school University of Maryland
2023-2025
William Park

William Park

Functional Developer

school Poolesville High School
2024+
Ryan Chung

Ryan Chung

Project Manager

school Poolesville High School
2025+
Akash Saran

Akash Saran

Lead Programmer

school Poolesville High School
2025+
Arjun Mujumdar

Arjun Mujumdar

Lead Tester

school Poolesville High School
2025+
Caleb Wen

Caleb Wen

Systems Analyst

school Poolesville High School
2025+
Ben Ross

Ben Ross

Technical Advisor

school Poolesville High School
2023+
Ishan Kheterpal

Ishan Kheterpal

Computer Science Teacher

school Poolesville High School
2023+
Mark Estep

Mark Estep

Computer Science Teacher

school Poolesville High School
2023+
Kevin Lee

Kevin Lee

Program Head

school Poolesville High School
2023+

History of LunaSim

April 2023
LunaSim Begins
Early Development of LunaSim
Initial LunaSim's interface in early 2023
LunaSim began as an initiative to provide a free, open-source alternative to commercial system dynamics modeling software used in our high school's 9th grade Foundations of Computer Science course. The project was born out of necessity: a system-wide device upgrade rendered our school's licensed modeling software incompatible with both Windows and school-issued Chromebooks. To ensure continuity in the curriculum, students Karthik Vedula, Aditya Patil, and Sienna Simms (then sophomores) collaborated to develop the structure of LunaSim from the ground up.
October 2023
First Major Deployment
Photo of a class of students learning LunaSim
Students' first introduction to LunaSim
By October 2023, LunaSim had reached its first major milestone: full deployment to over 60 students in the 9th grade computer science class. The tool empowered students to build interactive models of physical and engineering systems directly in the browser. Its success demonstrated that a browser-based simulation environment could be both powerful and accessible in a classroom setting. Students who used the software were amazed at its simplicity.
April 2024
Congressional App Design Challenge
Congressional App Design Challenge Presentation
Team presenting LunaSim at Capitol Hill
Photo with Congressman Trone
Photo with Congressman David Trone
LunaSim's momentum continued into April 2024, when the project was recognized at the national level. The team had the honor of presenting LunaSim at the U.S. Capitol as part of the Congressional App Challenge event. There, team members met Congressman David Trone and showcased how LunaSim is reshaping STEM education at our high school. The app was then named the winner of the 2023 Congressional App Challenge for Maryland's 6th District!
March 2025
LunaSim Copilot
LunaSim Copilot was developed by Karthik Vedula and William Park (a developer who previously rewrote LunaSim's interface in early 2024). It is an AI-powered assistant, aiding with system dynamics models. This tool uses large language models (LLMs) to interpret user instructions and automatically generate various models, enhancing productivity. The study also evaluated four LLMs, including reasoning models like OpenAI's o3-mini and DeepSeek's R1, demonstrating their capability to create complex models from user instructions with impressive accuracy rates. Learn more about LunaSim Copilot and download the research paper.
April 2025
Website Overhaul
New Team Updating LunaSim
New LunaSim interface in 2025
Following its second full year in use, LunaSim had expanded to over 120 students and became a core part of the 9th grade curriculum. As the original creators graduated and moved on to college, ownership of the project passed to a new team of freshmen (Ryan Chung, Akash Saran, Arjun Mujumdar, and Caleb Wen) — four students who had been part of LunaSim's first pilot run in 2023. Under their leadership, LunaSim received a complete UI refresh and major refinements to the software's infrastructure, laying the groundwork for a new generation of features and broader usability.
June 2025
Official Web Domain
In June 2025, LunaSim was deployed to its official web domain, LunaSim.org, thanks to the support of Ben Ross and Ishan Kheterpal, the school's computer science teacher. This move marked a key milestone in making LunaSim more accessible to everyone outside of our school community. LunaSim continues to evolve with contributions from students passionate about making system dynamics modeling accessible to all learners.

References & Recognition

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Congressional App Video

Watch our presentation video on YouTube
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Congressional App Winner

MD-06 District Winner of Congressional App Challenge
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Poolesville Pulse

SMCS Juniors Develop Software for 9th Grade Class
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Karthik's Blog

Congressional App Challenge – House of Code
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Research Paper

LunaSim: A Lightweight, Web-Based, Open-Source System Dynamics Modeling Software
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Source Code

LunaSim GitHub Repository
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LunaSim Copilot

AI-Powered System Dynamics Assistant

Recent Changelog:

v1.0: Added the ability for users to add their own text boxes to the model canvas.

v1.1: Added the ability for users to select between degrees and radians mode in simulation settings.

v1.2: Added negative and positive polarity for influences and emphasis for selected nodes, which can be toggled by pressing B on the keyboard.

v1.3: Added keybinds that can be modified within settings.

v2.0: Added new reservoirs under Experimental Features: conveyors, queues, and microwaves, plus a new link called the overflow.

v2.01: Added the ability to insert images within the model canvas.

v2.1: Added the ability to adjust model-element colors and change the sizes and colors of label text.

v2.1.1: Added the ability to reference [TIME] in the equation editor.

v2.2: Added PDF as an additional export option when saving a model.

v2.3: Added selectable units within the equation editor. Units are preserved when downloading or uploading a model and appear in charts and visuals.

v2.4: Added experimental Live API equations for weather conditions, the stock market, and economics.

v2.5: Added experimental Monte Carlo simulation support for uncertainty analysis across model parameters.

v2.5.1: Updated the user documentation with all experimental features and added easier Live API references within the equation editor.