# `Sidereon.Lambert`
[🔗](https://github.com/neilberkman/sidereon-ex/blob/main/lib/sidereon/lambert.ex#L1)

Lambert problem solver (Battin's method).

Given two position vectors and time of flight, find the transfer orbit
velocities. Algorithm 61, Vallado 2022, pp. 505-510.

# `vec3`

```elixir
@type vec3() :: {number(), number(), number()}
```

# `solve`

```elixir
@spec solve(vec3(), vec3(), vec3(), integer(), integer(), non_neg_integer(), number()) ::
  {{float(), float(), float()}, {float(), float(), float()}}
```

Solve Lambert's problem using Battin's method.

## Parameters

  * `r1`, `r2` - initial and final ECI position vectors in km
  * `v1` - initial velocity in km/s (needed for 180° transfers)
  * `dm` - direction of motion: `0` = short way, `1` = long way
  * `de` - direction of energy: `0` = low, `1` = high
  * `nrev` - number of revolutions (0, 1, 2, ...)
  * `dtsec` - time of flight in seconds

## Returns

`{v1t, v2t}` - transfer velocity vectors at r1 and r2 in km/s.

---

*Consult [api-reference.md](api-reference.md) for complete listing*