ZenRockets models recovery and staging explicitly: recovery devices carry deployment logic the simulator follows during the flight, and stages carry the separation and ignition timing that chains a multi-stage flight together.
Recovery devices#
Two device types cover the standard approaches:
- Parachutes use the canopy diameter, optional spill hole, shroud line count and length, and packed diameter and length. ZenRockets combines these dimensions with the selected fabric and cord materials to calculate the parachute's mass. The canopy geometry determines descent drag, while the packed dimensions show how much room the parachute needs in the bay.
- Streamers are defined by strip length, width and packed size, for the lighter end of the fleet.
Both attach where they'd physically be packed — under a nose cone, in a bay against a bulkhead — and contribute their mass as soon as you add them.
Deployment choices#
Each recovery device has its own deployment settings, which the simulator follows during the flight:
- Apogee
Deploy at apogee, with an optional lag in seconds — the classic single-deploy setup.
- Altitude
Deploy passing a set altitude on descent — the main in a dual-deploy configuration, with a drogue handling apogee.
- Ejection
Deploy on the motor's ejection charge. Pairs with the motor's delay setting: pick an installed delay per motor, from the delays that motor supports (discrete drilled delays or an adjustable range), or plug it entirely.
- Never
The device rides along for mass and volume but never opens — useful for backup chutes or payload configurations.
Multi-stage flights#
Use Add Stage in the toolbar to create another stage. Each stage appears at the top level of the parts tree and has its own motor, recovery hardware, separation and ignition settings. Two settings per stage define how the flight chains:
- Separation — at motor burnout plus an optional delay (the standard booster setup), or at the motor's ejection charge.
- Ignition delay — the coast time before the next stage lights, letting you tune the burnout–separation–ignition sequence.
The simulation continues through stage separation and upper-stage ignition. The sustainer starts from the booster's position, speed and attitude at separation, while each stage keeps its own trajectory, events and recovery.
Common setup issues#
The validation system watches recovery and staging logic specifically, because these are the mistakes that cost airframes:
- A recovery device set to Ejection while its motor is plugged; the simulator skips that deployment because no charge is available.
- Ejection-triggered separation on a stage whose motor has no physical charge configured.
- Every device set to Never — the rocket goes up with nothing coming down slowly.
- No recovery device at all.
Each recovery or staging issue in the validation panel includes the reason it was flagged and possible mitigations. Preparing to Simulate covers the other checks made on the rocket.