Open Apexline and go straight to the Altitude tab — no setup required. The default rocket and motor give you an instant simulation. Change the mass, diameter, or motor to explore. Save your rocket profile and it flows across the Stability and Recovery tabs automatically.
Support
Apexline Support
Help and contact information for Apexline: Model Rocket Flight Computer.
Open the Motors tab and tap the arrows icon in the top-right corner. Select up to 8 motors from the catalog — tap a motor to add it, tap again to remove it. Apexline runs the full flight simulation for each motor against your current rocket profile and ranks the results. Use the sort buttons (Apogee, T:W, Rod exit, Opt. delay) to re-order the table. The optional bar chart gives a visual comparison of the apogee spread.
After a flight, open the Log tab and tap + to record it. Enter the motor you flew, your measured apogee (from an altimeter if you have one), notes, and launch site. The log shows your prediction error percentage so you can see how accurate your Cd estimate is getting over time. Use the export button to save all entries as a CSV file. Tap the chart icon in the toolbar to open Flight Stats — a summary of your accuracy trend across all altimeter flights.
Email the App Store product page with your device model, iOS version, and a short description of what happened.
Common Questions
Does the app require an internet connection?
No. Apexline is fully offline. All motor data, guides, calculators, and the Motor Compare tool work without any network connection.
Does the app require an account?
No account is needed. Rocket profiles and flight log entries are stored locally on your device.
Where is my data stored?
All data is stored on your device using the system's local storage. It is included in iCloud and iTunes backups through the normal iOS backup process.
What is Cd and why does it matter?
Cd (drag coefficient) describes how aerodynamically sleek your rocket is. A lower Cd means less drag and a higher predicted apogee. Clean, well-finished model rockets are typically 0.45–0.75. The Cd Calibration tool (Learn → Tools → Cd Calibration) back-calculates your rocket's real Cd from a measured apogee so future predictions improve over time. The Flight Stats view shows you whether accuracy is trending better as you calibrate.
How do I compare motors?
Open the Motors tab and tap the arrows icon (top-right). On the Motor Compare screen, tap "Add / remove motors…" and select the motors you want to compare — up to 8 at once. The table ranks every motor by predicted apogee by default; use the sort buttons to switch to thrust-to-weight, rod-exit speed, or delay match. Your current rocket profile (mass, diameter, Cd, site altitude) is used automatically.
What does the Flight Stats trend chart show?
The chart plots your prediction error percentage (predicted minus measured, as a percentage of measured) in chronological order — oldest flight at the left. Points near zero mean the simulation matched reality well. A downward drift toward zero in recent flights confirms that Cd calibration is working. Points coloured green are within 10 %, amber within 20 %, red beyond 20 %.
What changed in version 1.2?
Version 1.2 adds Motor Compare (run the full simulation for up to 8 motors at once and rank the results), Flight Stats (accuracy trend chart and summary across all altimeter flights), and two new Learn guides on motor comparison and reading your flight statistics.
What changed in version 1.1?
Version 1.1 added the Flight Log (record real flights and compare against predictions), Cd Calibration (back-calculate drag from measured apogee), the Field & Safety Calculator (NAR minimum field sizes, drift estimate, wind limit), and an expanded motor catalog with Apogee Components and additional AeroTech motors.
How accurate is the altitude prediction?
Apexline uses a 2 ms Runge-Kutta integration of the full equation of motion (thrust, drag, gravity, changing mass, and ISA air density) — the same physical model that OpenRocket uses for a basic altitude estimate. Results are close for near-vertical flights with calm wind, but treat them as a careful prediction, not a measurement. An altimeter is the only way to know for sure.
Are the motor specs accurate?
Specifications are typical published headline values compiled for planning — always confirm against the certified data printed on the motor or in its data sheet before flying.