Project Apollo for the Reentry Space Simulator (UWP)


A quick update from the development of Project Apollo for Reentry. For those of you who are unfamiliar with my project, Reentry is a Windows 10 UWP app that lets you fly the Mercury, Gemini and soon the Apollo spacecraft’s from NASA’s earlier space programs. The purpose is to give you a realistic feeling of how it was to be an astronaut in these machines in full 3D. You are able to follow the real checklists the astronauts used, and study the space crafts using the real manuals created by NASA.

In addition, the simulator comes with an in-game academy, as well as the game manuals found here:

In this post I wish to give you a state if the project, how things fit together and how it looks!


Before visiting Apollo, let me show you what you currently have access to.

The game is in Technical Preview II, and new updates and modules are just submitted as updates. Your installation will stay up-to-date once they roll out.

Technical Preview II gives you access to both the Mercury and the Gemini spacecraft. These are still WIP, but in a state that allows you to perform complex maneuvers in space, as well as follow real checklists and so on. They also comes with some missions you can do, however the mission system is not final.

You can find some videos at

Mercury cockpit

Gemini cockpit

Mercury-Atlas launching


The Apollo Module has been my main goal since I started working on this project, but I wanted to start with the basics and also where NASA started (given the complexity of the entire Apollo program). Mercury and Gemini has been two long projects, a total of 3 years. This has given me some good insights into the how the technology of the space program was developed, astrophysics/orbital mechanics and also how I can deal with some of the mistakes I have made during development.

This section will give you an overview of the current state of the project, from a development perspective.


Both the Mercury and the Gemini module for Reentry was based on my physics engine named GeoGravity to enable Orbital Mechanics around Earth. The first major change for Apollo is that I’m now working with a PhD. in astrophysics on combining my engine with his engine to solve a few things:
1) Stability
2) Going to the Moon
3) More accurate and realistic math

I learned a lot from implementing the two first iterations of my physics engine and how to handle scale and double precision in Unity, and with this new engine, these leanings are all incorporated to give the sim more flexibility and better graphics.

In the screenshot above, the calculations required to fly to the Moon is being tested in an isolated environment/completely different project. Once it’s right I will merge it into the Reentry project and start working on the TLI logic in Apollo.


Project Apollo is far from complete, but a version will soon be released into the Technical Preview II found in Windows Store.

Most of the major components of the panel is complete, including both the model and using it as an interface to the mechanics under the hood.



In the screenshot above you can see that a lot of the switches are already in place. Each is connected logically to internal systems. The missing switches are not yet implemented. What you see is the commanders view (left seat) and the controls for both the primary navigation and control systems, as well as the backup Spacecraft Control System.


The above is the lunar module pilots view, and contains the controls for the Electrical Power System, the Service Propulsion System and the Fuel Cells. It also contains the controls for communication.


The center seat is for the Command Module Pilot, and contains the controls for the computer, the Service Module thrusters, joysticks for both rotational and translational maneuvers, the Cautions and Warnings panel, Mission Timer and the Environmental Control Systems. The hole in the middle is the entry to the Lunar Module itself, once docked with it.

Again, as you can see, most of the switches are not yet in place when it comes to the Environmental Control System and the Communication Systems.


With the exception of a stable guidance computer (LVDC), the launch sequence is working. The computer can run programs and works as the interface between the astronauts and the primary navigation and control system.

(Yes, the texture is wrong on keypad number 7)

The computer does not run the real emulator of the Apollo Command Module Computer (due to licensing), however I’m working on an implementation that replicates a lot of its functionality and behavior. All the programs for prep and launch has been implemented.


The launch sequence kicks in once the countdown reaches zero and ignition is triggered. The rocket ascends into low-Earth parking orbit, where it will orbit Earth until the Trans-Lunar Injection burn.



Apollo comes with two independent systems for controlling the spacecraft. The first one is the Primary Guidance, Navigation and Control System, and the backup is the Spacecraft Control System. Basically, the PGN&C system is controlled automatically and/or through the Command Module Computer, while the SCS is controlled manually through switch-configurations on the panels.

Most of these systems has been implemented with exception of the Flight Director and Attitude Indicator (FDAI). The FDAI is functional, but I have not yet implemented the correct rotation it drives to based on the attitude of the spacecraft relative to a stable platform.



Each of the thrusters/quads can be configured/enabled independently with both circuit breakers and switches in the cockpit.



Apollo contains a lot of electronics. From the Saturn V to the Service Module, to the Command Module. These are controlled through circuit breakers, switches and automatic systems. The spacecraft is only connected to external power while on the launch pad. Once the umbilical disconnects, it runs on internal power sources.

These power sources are both battery powered (backup) and Fuel Cell powered (primary). The Fuel Cells are located in the Service Module and is disconnected before reentry. Both of these power sources are able to generate both DC and AC power. AC is powered through Inverters. You have a lot of control when it comes to the electric system, and it’s one of the most important systems to learn and pay attention to.


The command module comes with a lot of internal and external lights. You are able to configure what lights are powered, and their dim-levels. The panels are illuminated, as well as any digit you see.




As you can see from the screenshots above, the panel can be configured independently. You have three light control panels, so you can create a dark atmosphere, or a bright one, or as in the last screenshot configure one side to be bright and the other to be dark.


The SPS is the main engine, often referenced to as The Engine. It is what will alter your orbits (delta-v) after the Launch Vehicle is separated, and most importantly take you home after being in Lunar Orbit. It’s basically the bell shaped engine on the Service Module.


The engine needs to be gimbaled to keep the thrust balanced based on the center of gravity, as well as balanced when it comes to propulsion. This can be controlled on the panel as well.

Using the control panel to the left, you can control the balance of the oxidizer and the fuel. Also, on panel 1 there is a gimbal panel that enables you to gimbal the SPS on the Pitch and Yaw axis.

The SPS is also re-ignitable, meaning you can ignite it multiple times. Once the fuel and oxidizer levels start to get in the mid-range, the engine needs a forward thrust before ignition to make sure the fuel is in the correct spot inside the fuel tanks. Translational thrusters are used to do this.

The SPS is an important piece of equipment onboard, so it’s good to know how it works. Luckily, it’s mostly automatic. Winking smile


From the cockpit of a virtual Apollo Command Module, I wish to thank you for your time!

If you want to follow the project and updates, feel free to join my Facebook page for the project:

This is the first time I share these details about the new module for Reentry. I hope you found it interesting, and feel free to reach out with any questions! Lastly,  happy international women’s day to everyone out there!


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1 Response to Project Apollo for the Reentry Space Simulator (UWP)

  1. I keep folowing snd love the look and feel of it. Goes well with all reading material avilable about those days.

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