Rocket Calculator vs Thrustline Rocket Toolkit

ApogeeField is an offline flight calculator for low and mid-power model rocketry. Enter your rocket (dry mass, body diameter, drag coefficient, launch-guide length) and pick a motor, and it predicts your apogee, the best ejection delay, max velocity, and rail-exit velocity right at the pad — with no signal, no account, and no tracking. WHAT IT DOES - Apogee, max velocity and full altitude / velocity / acceleration flight curves — free. - Recommended ejection delay: ideal coast time mapped to the nearest delay you can actually buy, with the offset in seconds. - Rail-exit velocity with a configurable safety threshold, so you can judge whether the rocket will leave the rail under control. - Compare motors side by side and export your flight card and saved rockets. - Built-in motor database (thrust curves and certified statistics) plus import of your own .eng / .rse files. - Switch freely between metric and imperial units. HOW THE MODEL WORKS (and its limits) ApogeeField runs a deterministic 1-DOF (vertical, point-mass, with launch-angle cosine) flight integration: thrust-curve integration, variable-mass burn (propellant mass is subtracted as impulse is consumed), quadratic drag, and an ISA standard-atmosphere density model, coasting to apogee at the velocity zero-crossing. Every assumption is shown on the results screen so you can line your inputs up against OpenRocket or your own altimeter data. It is an engineering estimate for hobby use — a starting point, not a guarantee. The model does not account for wind, airframe stability, roll, or weathercocking, so real flights will differ. Always verify with an altimeter. This is not a safety, airworthiness, or legal document, and it does not replace the NAR / Tripoli safety code or local airspace rules — follow them. PRIVACY & PRICING 100% offline. No account, no network requests, no analytics, no ads. Your rockets and imported motor files stay on your device. One-time unlock — no subscription. Motor data are numerical facts drawn from publicly submitted thrust-curve files and NAR / Tripoli / CAR certification statistics, stored in our own format with the source and database version shown in the app.

Thrustline Rocket Toolkit is a fully offline design and stability companion built for model rocketry hobbyists — from Estes starter kits to high-power NAR/TRA builds. No live data feeds, no sensors, no gimmicks: just real physics you can trust before every launch. Enter your airframe dimensions, fin geometry, and nose cone type to get an instant Barrowman-equation Center of Pressure calculation. Add component masses and positions to compute your Center of Gravity, then see a clear, color-coded stability diagram in calibers so you know at a glance if your rocket is stable, marginal, or unstable. Predict performance with a numeric drag-based altitude and velocity simulator, using your rocket's mass, motor impulse, and frontal area to chart altitude, velocity, and time-to-apogee. Browse a bundled offline motor reference library spanning A through O impulse classes with thrust-curve charts, or add your own custom motor data. Keep your build organized with a parts and inventory tracker for tubes, fins, nose cones, motors, parachutes, and wadding, complete with low-stock reminders. Attach build photos and notes to each rocket, and update weigh-ins to automatically refresh your stability calculation. Before heading to the pad, run a customizable NAR/TRA-style pre-flight safety checklist covering igniter, recovery, and range-safety steps. Then export a clean, shareable one-page PDF flight card summarizing your design specs, stability margin, and predicted altitude for your range safety officer. Thrustline Rocket Toolkit works entirely offline, with no account, no subscription gimmicks, and no network dependency — just a dependable engineering tool for hobbyists who care about doing it right.