Setting up an Aerobrake

NOTE - My personal experience recently with aerobraking shows that this feature may still require some attention from the developer in regards to accuracy. Your mileage may vary - stay tuned to the official thread for updates.

This entry only focuses on how to set up an aerobrake event in Mission Architect, it does not explain what an aerobrake is or delve into considerations to take into mind when planning an aerobrake.

Gathering drag coefficient data (optional)

For precise results, you will want to determine the drag coefficient of your vessel rather than use the default of 0.2, which will provide approximate results. To do this you simply need to place the vessel into orbit around your target body (HyperEdit is a great tool to achieve this) and have it pass through the atmosphere. Any pass through the atmosphere will be sufficient, the only thing to keep in mind is that you should have it pass through in the same orientation and configuration that you plan to do for your actual aerobrake pass.

For very precise readings, right before the vessel hits the atmosphere use Mod+F5 to create a custom quicksave. Then, immediately after the vessel leaves the atmosphere, make another custom quicksave.

You now have to make note of the following data:

• Periapsis altitude from the quicksave prior to atmospheric entry
• SMA from the quicksave prior to atmospheric entry
• SMA from the quicksave after leaving the atmosphere
• Orbital inclination (from either quicksave)

Creating the event in Mission Architect

Load up your vessel state in Mission Architect and make sure that at some point along your mission plan the orbit of the vessel intersects the atmosphere of the body. Starting from any point outside the atmosphere, select Aerobrake from the list of events to insert. Select your drag model to match the current aerodynamics model you are using in your game. If you collected drag coefficient data, click the button to open the calculator. Otherwise leave the default value and skip to the next section.

If you are plugging in data to get your exact drag coefficient follow these steps:

1. Select your drag model
2. Select the body you are orbiting
3. Enter in your vessel mass (KER or VOID can provide this data in flight)
4. Fill out the remainder of the fields using the data you collected from the quicksaves
5. Calculate the Cd and plug that number into the Aerobrake event

Coasting out of your aerobrake

Once you've created the event, Mission Architect will coast down, through and back out of the atmosphere and onto your new trajectory. To see this, create a Coast to Apoapsis event and you will see that your orbit has been affected by the coast through the atmosphere.

Can I use this to plan orbital landings?

I tried this once on Kerbin with a direct return from Mun and ended up 205km short of my intended landing zone. This was not designed to be used for orbital returns, but it could at least give you a good idea of where you will end up on the surface. And who knows? A single use case isn't all that definitive. Maybe I screwed up my planning.