lambert_izzo

Cargo workspace for Izzo's revisited Lambert solver and its WebAssembly adapter. A standalone Lambert crate — designed for callers who want a focused, correct, no_std/WASM-friendly solver without pulling a full astrodynamics framework just for the boundary-value step.

Reference: D. Izzo, Revisiting Lambert's problem, Celestial Mechanics & Dynamical Astronomy, 2014 (arXiv:1403.2705).

MSRV: Rust 1.85 (first edition-2024 stable). rust-toolchain.toml pins 1.88.0 for development; the published-crate MSRV is 1.85.

Crates

Crate	Path	Distribution
lambert_izzo	crates/lambert_izzo	crates.io — pure Rust, [f64; 3] API, no hard math dep, no_std.
lambert_izzo_wasm	crates/lambert_izzo_wasm	npm via wasm-pack — JS/TS bindings. Published as lambert-izzo.
lambert_izzo_test_support	crates/lambert_izzo_test_support	workspace-internal (publish = false) — astrodynamics constants, Kepler propagator, deterministic random batches for examples / benches / tests.

The core crate stays free of JavaScript concerns. The WASM crate owns TypeScript type generation and JavaScript error conversion. The test support crate is path-only — it never reaches crates.io.

See ARCHITECTURE.md for a code map of the solver pipeline (input validation → geometry → root finding → TOF dispatch → velocity reconstruction).

Rust usage

use lambert_izzo::{lambert, LambertInput, RevolutionBudget, TransferWay};

let input = LambertInput {
    r1: [7000.0, 0.0, 0.0],
    r2: [0.0, 7000.0, 0.0],
    tof: 1457.0, // ~quarter-period of a 7000 km circular Earth orbit
    mu: 398_600.4418,
    way: TransferWay::Short,
    revolutions: RevolutionBudget::SingleOnly,
};

let solutions = lambert(&input)?;
let v1 = solutions.single.v1;
let iters = solutions.diagnostics.single.iters;
# Ok::<(), lambert_izzo::LambertError>(())

For batch / porkchop-plot workloads, enable the rayon feature and pass a slice through lambert_par.

WASM usage

Build the wrapper as an npm package with wasm-pack:

wasm-pack build crates/lambert_izzo_wasm --target bundler --release

--target bundler matches the published npm package and works with Vite, webpack, Rollup, esbuild, and any other bundler that resolves import statements. For direct browser ES-module imports without a bundler, swap in --target web; for CommonJS Node.js consumption, use --target nodejs. The full target table is in crates/lambert_izzo_wasm/README.md.

Then import the generated package from a browser or bundler app:

import init, { solveLambert } from "./pkg/lambert_izzo_wasm";

await init();

const result = solveLambert({
  r1: [7000, 0, 0],
  r2: [0, 7000, 0],
  tof: 1457, // ~quarter-period of a 7000 km circular Earth orbit
  mu: 398600.4418,
  way: "short",
  maxRevs: null, // null = single-rev only; pass 1..=32 to search multi-rev branches
});

if (result.kind === "ok") {
  console.log(result.response.single.v1);
  console.log(result.response.diagnostics.single.iters);
} else {
  console.error(result.error.kind, result.error);
}

maxRevs is validated at request time. Out-of-range values (0 or > 32) reject with a typed RevsOutOfRange error before any solver work runs:

const result = solveLambert({ ...request, maxRevs: 100 });
if (result.kind === "err") {
  // result.error.kind === "RevsOutOfRange"
  // result.error.requested === 100, result.error.max === 32
}

The wrapper response shape (camelCased per serde(rename_all)):

type LambertResponse = {
  single: { v1: [number, number, number]; v2: [number, number, number] };
  multi: Array<{
    nRevs: number;
    longPeriod: { v1: [...]; v2: [...] };
    shortPeriod: { v1: [...]; v2: [...] };
  }>;
  diagnostics: {
    single: { iters: number };
    multi: Array<{ nRevs: number; longPeriod: { iters: number }; shortPeriod: { iters: number } }>;
  };
};

A single-page browser demo lives at crates/lambert_izzo_wasm/examples/web/.

Development

cargo build --workspace
cargo test --workspace
cargo clippy --workspace --all-targets -- -D warnings
cargo build --target wasm32-unknown-unknown -p lambert_izzo --lib
cargo build --target wasm32-unknown-unknown -p lambert_izzo_wasm --lib
cargo run --release -p lambert_izzo --example demo
cargo run --release -p lambert_izzo --example stress

Toolchain is pinned by rust-toolchain.toml.

Release notes

See CHANGELOG.md for per-release changes.

License

MIT OR Apache-2.0