Orbital elements: Difference between revisions
Added Kotlin
m (→{{header|Sidef}}: minor fix: returns now an array of Number objects) |
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TODO: pick an example from a reputable source, and bring the algorithm description onto this site. (Restating those pages in concise a fashion comprehensible to the coders and readers of this site will be a good exercise.)
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=={{header|Kotlin}}==
{{trans|Sidef}}
<lang scala>// version 1.1.4-3
class Vector(val x: Double, val y: Double, val z: Double) {
operator fun plus(other: Vector) = Vector(x + other.x, y + other.y, z + other.z)
operator fun times(m: Double) = Vector(x * m, y * m, z * m)
operator fun div(d: Double) = this * (1.0 / d)
fun abs() = Math.sqrt(x * x + y * y + z * z)
override fun toString() = "($x, $y, $z)"
}
fun orbitalStateVectors(
semimajorAxis: Double,
eccentricity: Double,
inclination: Double,
longitudeOfAscendingNode: Double,
argumentOfPeriapsis: Double,
trueAnomaly: Double
): Pair<Vector, Vector> {
var i = Vector(1.0, 0.0, 0.0)
var j = Vector(0.0, 1.0, 0.0)
var k = Vector(0.0, 0.0, 1.0)
fun mulAdd(v1: Vector, x1: Double, v2: Vector, x2: Double) = v1 * x1 + v2 * x2
fun rotate(i: Vector, j: Vector, alpha: Double) =
Pair(mulAdd(i, +Math.cos(alpha), j, Math.sin(alpha)),
mulAdd(i, -Math.sin(alpha), j, Math.cos(alpha)))
var p = rotate(i, j, longitudeOfAscendingNode)
i = p.first; j = p.second
p = rotate(j, k, inclination)
j = p.first
p = rotate(i, j, argumentOfPeriapsis)
i = p.first; j = p.second
val l = semimajorAxis * (if (eccentricity == 1.0) 2.0 else (1.0 - eccentricity * eccentricity))
val c = Math.cos(trueAnomaly)
val s = Math.sin(trueAnomaly)
val r = l / (1.0 + eccentricity * c)
val rprime = s * r * r / l
val position = mulAdd(i, c, j, s) * r
var speed = mulAdd(i, rprime * c - r * s, j, rprime * s + r * c)
speed /= speed.abs()
speed *= Math.sqrt(2.0 / r - 1.0 / semimajorAxis)
return Pair(position, speed)
}
fun main(args: Array<String>) {
val (position, speed) = orbitalStateVectors(
semimajorAxis = 1.0,
eccentricity = 0.1,
inclination = 0.0,
longitudeOfAscendingNode = 355.0 / (113.0 * 6.0),
argumentOfPeriapsis = 0.0,
trueAnomaly = 0.0
)
println("Position : $position")
println("Speed : $speed")
}</lang>
{{out}}
<pre>
Position : (0.7794228433986797, 0.45000003465368416, 0.0)
Speed : (-0.5527708409604438, 0.9574270831797618, 0.0)
</pre>
=={{header|Perl}}==
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