Model Rocket Wind Drift Calculator
Enter expected wind aloft, descent rates, and recovery altitude to estimate where a rocket may land after deployment. The result separates the contribution of each wind layer and checks it against the usable radius of your field.
Nominal drift distance (ft)635.56
- Estimated descent time (s)
- 66.67
- Landing direction
- 90.0° from the pad
- East/west offset (ft)
- 635.56
- North/south offset (ft)
- 0
- Low-, middle-, and upper-layer drift
- Low: 33.3 s; +244.4 ft east, +0.0 ft north; 244.4 ft vector Middle: 33.3 s; +391.1 ft east, +0.0 ft north; 391.1 ft vector Upper: 0.0 s; +0.0 ft east, +0.0 ft north; 0.0 ft vector
- Drogue and main drift
- 66.7 s; +635.6 ft east, +0.0 ft north; 635.6 ft vector
- Planning recovery radius (ft)
- 953.34
- Field clearance (ft)
- 246.66
- Field-fit result
- Within the entered recovery radius after the uncertainty margin.
Assumes steady horizontal wind in each altitude band and the entered vertical descent rates.
Drift is measured from the pad; it excludes ascent drift and recovery events before full descent.
How to use this calculator
- Enter the predicted apogee above the launch field and choose single or dual deployment.
- Use a measured or manufacturer-supported descent rate for the full recovery configuration in each phase.
- Enter representative wind speed and meteorological “from” direction for the low, middle, and upper altitude bands.
- Measure the available radius from the pad to the nearest recovery boundary in the likely drift direction.
- Apply a deliberately conservative uncertainty margin before deciding whether the field is suitable.
How the drift estimate is calculated
The calculator divides the descent at every relevant altitude: the low-layer top, the middle-layer top, and, for dual deployment, the main-parachute deployment altitude. Each resulting segment has one wind vector and one vertical descent rate. This matters because the wind close to the field can differ materially from the wind near apogee.
For a segment with vertical thickness h and descent rate r, time under that segment is t = h / r. Wind speed S in mph is converted to feet per second as V = 1.46667 × S. Meteorological direction is the direction the wind comes from, so a wind from 270° moves the rocket east. With θ expressed in radians, the downwind components are vE = −V sin(θ) and vN = −V cos(θ).
The segment offsets are x = vE × t and y = vN × t. The calculator adds every segment to get total east offset X, north offset Y, and nominal drift D = sqrt(X² + Y²). It reports the landing bearing clockwise from north as (atan2(X, Y) + 360) mod 360. When all vector components cancel to zero, there is no meaningful landing bearing.
Single and dual deployment
Single deployment uses one descent rate for the complete path from apogee to ground. Dual deployment uses the drogue rate above the chosen main deployment altitude and the main-parachute rate at or below it. A higher main deployment altitude gives the slower main canopy more time in the wind; a main altitude of zero leaves the entire modeled descent in the drogue phase. If the main altitude is at or above apogee, the calculation treats the full descent as main-canopy descent.
Using the field comparison
The planning recovery radius is Dp = D × (1 + P / 100), where P is the uncertainty margin. Field clearance is C = F − Dp, where F is the available recovery radius. A positive clearance is only a planning result, not permission to launch. UKRA’s launch-site guidance, for example, applies site dimensions separately from expected altitude and motor impulse.
What changes the result and what it leaves out
Descent rate, apogee, and low-altitude wind usually have the largest practical effect because the main parachute can spend substantial time close to the ground. Winds from different layers can reinforce one another, cancel, or change the final bearing. Use winds aloft and repeat the calculation for gusty or uncertain forecasts rather than relying only on a surface reading.
This is a steady-wind recovery estimate, not a flight simulation. It does not model ascent displacement, weathercocking, deployment delay, canopy inflation, thermals, turbulence, canopy oscillation, terrain, trees, ground drag, or a recovery-system failure.
Worked example
Suppose a rocket reaches 1,000 ft AGL and descends at 10 ft/s under a single parachute. The low layer reaches 500 ft and has a 10 mph wind from 270°, which moves the rocket east. The middle layer extends from 500 to 1,000 ft and has a 10 mph wind from 0°, which moves it south.
Each layer takes 500 / 10 = 50 s. A 10 mph wind is 14.6667 ft/s, so each layer contributes 733.3 ft along its axis. The combined offset is +733.3 ft east and −733.3 ft north, giving nominal drift of 1,037.1 ft toward 135°. With a 50% margin, the planning radius is 1,555.6 ft; a 1,200 ft field radius therefore has −355.6 ft of clearance.
Common questions
How do I estimate model rocket wind drift?
Establish the expected deployment altitude, use a representative vertical descent rate, and multiply the time spent in each wind layer by that layer’s horizontal wind vector. Add the east and north components instead of adding distances, because winds from different heights can point in different directions.
Should I use surface wind or winds aloft?
Use both when the rocket will descend through more than one altitude band. Surface wind is important near landing, but it may not represent the wind near apogee; a forecast sounding, local pilot report, or a carefully observed wind profile can provide a better planning input.
What does wind from 270 degrees mean?
Meteorological wind direction describes where the wind comes from. Wind from 270° comes from the west and blows toward the east, so this calculator gives it a positive eastward component. A direction of 360° is treated as north, the same as 0°.
How does dual deployment reduce recovery drift?
Dual deployment can keep the rocket descending faster under a drogue at high altitude, then use the main parachute closer to the ground for a safer landing speed. Whether it reduces total drift depends on the main altitude, the two descent rates, and the wind profile; it is not automatic.
How much extra recovery margin should I allow?
Choose enough margin to account for forecast uncertainty, gusts, varying descent rate, canopy motion, and errors in predicted altitude. The calculator leaves the percentage to you because the appropriate amount depends on the quality of the wind data, the site, and the consequence of an overrun.
Does this calculator determine the minimum legal or code-compliant launch field?
No. It is a recovery-planning estimate only. Follow the current rules and safety code that apply to your location, club, motor class, airspace, landowner permission, and launch organizer; use the more conservative constraint when they differ.