Where are you observing from?
Location estimated from your device's time zone. Pass times change from one city to the next: set your location for accurate times. It is stored only on this device.
Model rocketry
Plan a launch from
Hourly launch weather, upper winds and parachute drift, to plan an amateur rocket launch.
Launch weather
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Daytime hours only. Highlighted rows: hours within your limits. Tap an hour to make it the launch time. Mean wind 10 m above ground and the direction it blows from; gusts and rain over the preceding hour; low cloud: up to 3 km altitude.
Limits
Cautious default values (wind 15 km/h, gusts 25 km/h, low cloud 50%, no rain), chosen for this tool: they are not official rules. The Planète Sciences specification and the launch supervisor have the final say.
Upper winds
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Wind speed at launch time, from the ground to about 3 km. Arrow: the way the wind blows, north up. Dashes: parachute opening altitude. Open-Meteo levels: 10, 80, 120 and 180 m above ground, then the 1000 to 700 hPa pressure levels at their forecast height.
Parachute
Terminal speed v = √(2·m·g ÷ (ρ·Cd·A)), where A is the area of a disc of diameter D and ρ the air density; the diameter for a target speed is the inverse, D = √(8·m·g ÷ (π·ρ·Cd·v²)), at ground level. ρ comes from the pressure and temperatures forecast for the launch time (dry air), otherwise from the standard atmosphere. An entered speed is the one measured near the ground; higher up, thinner air makes it larger. Dual deployment: the drogue slows the descent from apogee down to the opening altitude, then the main parachute takes over.
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Waiting for the forecast
Based on your limits, at the launch time. The launch supervisor has the final say.
Drift
Waiting for the forecast…
Estimate: descent rate recomputed at each altitude from the forecast air density, then drift added up in 5 m layers with the wind forecast for the launch time. The parachute is assumed open at the given altitude, with no free fall and no drift during the climb. Search area: a circle around the landing point that covers the same descent one hour earlier and one hour later, and with each wind level increased by the gap between gusts and mean wind at 10 m. A cautious envelope, not a guarantee.
Drift hour by hour
Daytime hours of the chosen day. Coloured: the launch time; solid bars: hours within your limits. Tap a bar to make it the launch time.
About this tool
What it does
A calculator to plan an amateur rocket launch: pick an hour when wind, gusts, low cloud and rain stay within your limits, see the wind up to about 3 km and estimate where the parachute will land.
The calculations
Descent rate from the parachute's mass, diameter and drag coefficient, with the air density derived from the forecast pressure and temperatures (1976 US Standard Atmosphere as a fallback). Drift added up in 5 m layers, with the wind interpolated between forecast levels, hour by hour, with a search area. Everything is computed on your device.
The sources
Hourly Open-Meteo forecasts over three days: wind at 10, 80, 120 and 180 m, wind and temperature at the 1000 to 700 hPa pressure levels, pressure and temperature at ground level, low cloud, rain and visibility. Limits and parachute settings are saved on this device.
How is parachute drift calculated?
Descent speed comes from v = √(2mg / (ρ·Cd·A)), with the forecast air density at each altitude. From deployment to the ground, drift is added up in 5 m layers, each pushed by the wind forecast at its height. The search area repeats the calculation an hour before and after, and with gusts: a cautious estimate, not a guarantee.
What wind limits for a launch?
By default: mean wind 15 km/h, gusts 25 km/h, low cloud 50%, no rain. These cautious values were chosen for this tool and are not official: the Planète Sciences specification and the launch supervisor have the final say.
What about real launchers?
To follow orbital launches worldwide, including those from Kourou, see upcoming rocket launches.