Transfer Window

Launch-window maps computed live on your GPU, one Lambert solve per pixel

Depart–

Arrive–

Flight–

C3–

v∞ arrival–

Total Δv–

GPU redraw–

Try

Pick a route. Drag the map to move the date window, scroll to zoom, click a pixel to select that transfer; every control below stays live.

Transfer

Origin Destination

Depart from to

Arrive from to

Colour by

Iso-contours Time-of-flight lines Colour range

Resolution Solution

Retrograde transfers

The map on screen is float32 from the shader. Hover shows the Float64 CPU numbers for the cell under the cursor; this button recomputes the whole grid in Float64 in a worker and reports how far the two disagree.

Selected transfer

Click the map to select a transfer, or let the presets pick the cheapest cell.

Δv budget (patched conics)

Parking orbit altitude at origin, km

Capture orbit altitude, km

Next windows

Scans forward from today for the next three launch windows to each destination and lists the minimum total Δv with the current budget settings.

Gravity assist

Launch window from to

Every flyby is unpowered: differential evolution followed by Nelder–Mead searches the launch date and every leg time jointly for the lowest total Δv. Any mismatch between incoming and outgoing v∞ is charged as a manoeuvre, and a turn that cannot be made above the minimum altitude is charged too.

N-body check

Dormand–Prince RK45 in Float64 with the Sun and all eight planets as point masses. SOI exit starts on the real departure hyperbola at the edge of the sphere of influence with everything attracting; planet centre starts from the conic's own state and leaves the departure planet out, which isolates what the other planets do. A differential corrector then finds the change to the departure velocity that actually hits the target.

Launch vehicles

Approximate payload to the selected C3, read off published performance curves (Falcon 9 and Falcon Heavy expendable, Atlas V 551). Treat as ±15%.

3D view

Planet orbits Ecliptic grid Labels

Drag to orbit, scroll to zoom, shift-drag or right-drag to pan. The scrubber moves every planet along its real orbit; the spacecraft rides the transfer arc. transfer N-body path gravity-assist legs. Planet sizes are not to scale.

What you're looking at

A porkchop plot is the mission designer's map of a launch window: departure date across, arrival date up, and at every point the cost of the transfer that connects the two planets on those dates. Each pixel is a solution of Lambert's problem, the two-body boundary-value problem: given two positions and a time of flight, find the orbit. Here a WebGL2 fragment shader evaluates the planetary ephemerides and solves Lambert's problem for every pixel, so dragging the date window redraws a quarter of a million orbits at once.

The numbers come from the same physics on the CPU in Float64: JPL's approximate Keplerian elements for the planets, Izzo's 2015 Lambert solver, and patched conics for the Δv budget, which treat the departure and arrival as hyperbolic escapes and captures around each planet and the cruise as a Sun-only orbit. The bright islands are the windows; the ridge running through them is where the transfer angle passes 180° and the orbit plane has to tilt to reach the target's out-of-plane position.

A gravity assist bends the trajectory around a planet without burning propellant, but only by an angle the planet's gravity can supply above a safe altitude, and only while conserving the speed relative to the planet. The optimiser searches whole sequences under those rules. The N-body check then integrates the chosen transfer with every planet's gravity and shows how far the tidy conic picture is from the real thing.

Keys: 1 and 2 switch views, arrows nudge the selected cell, space plays the animation, R resets. Accuracy: see the benchmark page. Built by Lukas Schulz.

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