Kinda works, improve intercept

src/calculations/constants.ts

@@ -39,7 +39,7 @@ export const Eve: Body = {
 	rotationPeriod: 80500,
 	sphereOfInfluence: 85109365,
 	closestSafeDistance: 790000,
-	initialMeridianLongitude: 0
+	initialMeridianLongitude: 0.00040726270866286995
 };
 
 export const Gilly: Body = {
@@ -50,7 +50,7 @@ export const Gilly: Body = {
 	rotationPeriod: 28255,
 	sphereOfInfluence: 126123.27,
 	closestSafeDistance: 19400,
-	initialMeridianLongitude: 0.0859373
+	initialMeridianLongitude: 0.08784209395031439
 };
 
 export const Kerbin: Body = {

src/calculations/mathematics.ts

@@ -133,6 +133,27 @@ export function addVector(vectorOne: number[][], vectorTwo: number[][]): number[
 	return result;
 }
 
+export function addMatrix(matrixOne: number[][], matrixTwo: number[][]): number[][] {
+	if (!checkIfValidMatrix(matrixOne) || !checkIfValidMatrix(matrixTwo)) {
+		throw new TypeError("Two valid matrices are required");
+	}
+
+	if (matrixOne.length != matrixTwo.length || matrixOne[0].length != matrixTwo[0].length) {
+		throw new TypeError("The two matrices need to have the same dimensions");
+	}
+
+	var result = [];
+	for (var i = 0; i < matrixOne.length; i++) {
+		let row = [];
+		for (var j = 0; j < matrixOne[0].length; j++) {
+			row.push(matrixOne[i][j] + matrixTwo[i][j]);
+		}
+		result.push(row);
+	}
+
+	return result;
+}
+
 export function subtractVector(vectorOne: number[][], vectorTwo: number[][]): number[][] {
 	if (!checkIfValidMatrix(vectorOne) || !checkIfValidMatrix(vectorTwo)) {
 		throw new TypeError("Two valid matrices are required");

src/calculations/orbit-calculations.ts

@@ -1,5 +1,6 @@
+import type { InterpolationParameters } from "../gui/interpolate";
 import type { Body } from "./constants";
-import { addVector, getVectorMagnitude, multiplyMatrixWithScalar, normalizeVector, subtractVector, vectorCrossProduct, vectorDotProduct } from "./mathematics";
+import { addMatrix, addVector, getVectorMagnitude, matrixMultiply, multiplyMatrixWithScalar, normalizeVector, subtractVector, vectorCrossProduct, vectorDotProduct } from "./mathematics";
 
 export interface Orbit {
 	semiLatusRectum: number,
@@ -32,12 +33,42 @@ export interface Manoeuvre {
 
 export interface Transfer {
 	transferOrbit: Orbit,
+	transferOrbitTrueAnomalyAtManoeuvreOne: number,
+	transferOrbitTrueanomalyAtManoeuvreTwo: number,
 	firstManoeuvre: Manoeuvre,
 	secondManoeuvre: Manoeuvre,
 	farthestPointDistance: number,
 	closestPointDistance: number,
 }
 
+export interface Landing {
+	transferOrbit: Orbit,
+	transferManoeuvre: Manoeuvre,
+	brakingDeltaV: number,
+	brakingAltitude: number,
+	brakingTimestamp: number,
+	totalDeltaV: number
+}
+
+export interface ShipParameters {
+	mass: number,
+	thrust: number,
+	specificImpulse: number
+};
+
+export interface LandingParameters {
+	targetLatitude: number;
+	targetLongitude: number;
+	targetAltitude: number;
+	minimumAngle: number;
+};
+
+export const DefaultShipParameters: ShipParameters = {
+	mass: 1000,
+	thrust: 100,
+	specificImpulse: 100
+};
+
 export class LambertSolutions {
 	// Pre-calculate some values to make finding an orbit based on the parameter gamma faster
 	// Naming these in a good way is very hard. To see where they came from, look at
@@ -161,6 +192,11 @@ export class LambertSolutions {
 			transferGoalTrueAnomaly -= 2 * Math.PI;
 		}
 
+		if (transferStartTrueAnomaly < 2 * Math.PI && transferGoalTrueAnomaly > 2 * Math.PI) {
+			transferStartTrueAnomaly -= 2 * Math.PI;
+			transferGoalTrueAnomaly -= 2 * Math.PI;
+		}
+
 		let closestPoint;
 		if (transferStartTrueAnomaly < 0 && transferGoalTrueAnomaly >= 0) {
 			closestPoint = semiLatusRectum / (1 + eccentricity);
@@ -220,6 +256,8 @@ export class LambertSolutions {
 
 		return {
 			transferOrbit: transferOrbit,
+			transferOrbitTrueAnomalyAtManoeuvreOne: transferStartTrueAnomaly,
+			transferOrbitTrueanomalyAtManoeuvreTwo: transferGoalTrueAnomaly,
 			firstManoeuvre: startManoeuvre,
 			secondManoeuvre: goalManoeuvre,
 			closestPointDistance: closestPoint,
@@ -308,14 +346,15 @@ export function getEccentricAndTrueAnomalyFromMeanAnomaly(meanAnomaly: number, e
 			keplerEquationDerivative = (guess: number) => eccentricity * Math.cosh(guess) - 1;
 		}
 
-		while (Math.abs(keplerEquation(eccentricAnomaly)) > 0.000001) {
+		while (Math.abs(keplerEquation(eccentricAnomaly)) > 0.0000000001) {
 			eccentricAnomaly = eccentricAnomaly - keplerEquation(eccentricAnomaly) / keplerEquationDerivative(eccentricAnomaly);
 		}
 
 		if (eccentricity < 1) {
-			trueAnomaly = 2*Math.atan(Math.sqrt((1 + eccentricity) / (1 - eccentricity)) * Math.tan(eccentricAnomaly / 2));
+			let beta = eccentricity / (1 + Math.sqrt(1 - eccentricity**2));
+			trueAnomaly = eccentricAnomaly + 2 * Math.atan(beta * Math.sin(eccentricAnomaly) / (1 - beta * Math.cos(eccentricAnomaly)));
 		} else {
-			trueAnomaly = 2*Math.atan(Math.sqrt((eccentricity + 1) / (eccentricity - 1)) * Math.tanh(eccentricAnomaly / 2));
+			trueAnomaly = Math.atan2(Math.sqrt(eccentricity**2 - 1) * Math.sinh(eccentricAnomaly), (eccentricity - Math.cosh(eccentricAnomaly)));
 		}
 	}
 
@@ -378,7 +417,7 @@ export function getOrbitalCoordinatesFromAltitude(altitude: number, headingInwar
 		meanAnomaly = eccentricAnomaly;
 	} else if (orbit.eccentricity < 1) {
 		eccentricAnomaly = Math.atan2(Math.sqrt(1 - orbit.eccentricity**2)*Math.sin(trueAnomaly), orbit.eccentricity + Math.cos(trueAnomaly));
-		meanAnomaly = eccentricAnomaly - eccentricAnomaly * Math.sin(eccentricAnomaly);
+		meanAnomaly = eccentricAnomaly - orbit.eccentricity * Math.sin(eccentricAnomaly);
 	} else {
 		eccentricAnomaly = 2 * Math.atanh(Math.sqrt((orbit.eccentricity - 1) / (orbit.eccentricity + 1)) * Math.tan(trueAnomaly / 2));
 		meanAnomaly = orbit.eccentricity * Math.sinh(eccentricAnomaly) - eccentricAnomaly;
@@ -625,6 +664,7 @@ export function findCheapestLambertSolution(lambertSolutions: LambertSolutions):
 }
 
 export type ProgressCallbackFunction = (transfersChecked: number, totalNumberOfTransfers: number, currentBestDeltaV: number | null, currentBestTransfer: Transfer | null) => void;
+export type LandingProgressCallbackFunction = (pathsChecked: number, totalNumberOfPaths: number, currentBestDeltaV: number | null, currentBestLanding: Landing | null) => void;
 
 export function findCheapestTransfer(startingSituation: OrbitalCoordinates, targetOrbit: Orbit, body: Body, progressCallback?: ProgressCallbackFunction): Transfer | null {
 	// First, create a set of starting true anomalies
@@ -647,7 +687,7 @@ export function findCheapestTransfer(startingSituation: OrbitalCoordinates, targ
 	} else {
 		let finalAnomaly = Math.abs(Math.acos((startingSituation.orbit.semiLatusRectum - body.sphereOfInfluence) / (body.sphereOfInfluence * startingSituation.orbit.eccentricity)));
 		let step = (finalAnomaly - startingSituation.trueAnomaly) / 100;
-		for (var i = 1; i < 101; i++) {
+		for (var i = 0; i < 101; i++) {
 			startingTrueAnomalies.push(startingSituation.trueAnomaly + i * step);
 		}
 	}
@@ -712,70 +752,56 @@ export function findCheapestTransfer(startingSituation: OrbitalCoordinates, targ
 	return bestTransfer;
 }
 
-export function findLambertSolutionsWithCorrectTime(lambertSolutions: LambertSolutions, expectedTime: number): Transfer | null{	
+export function findLambertSolutionsWithCorrectTime(lambertSolutions: LambertSolutions, expectedTime: number): Transfer | null {	
-	const step = lambertSolutions.parabolaGamma - lambertSolutions.extremalGamma;
+	// Do a secant method search. Start near the parabola
+	let scale = Math.abs(lambertSolutions.parabolaGamma - lambertSolutions.extremalGamma);
+	let x0 = lambertSolutions.parabolaGamma;
+	let x1 = lambertSolutions.parabolaGamma + scale / 100;
 
-	const getGamma = (steps: number) => {
+	let t0 = lambertSolutions.getTransfer(x0);
-		return lambertSolutions.extremalGamma + steps*step;
+	let t1 = lambertSolutions.getTransfer(x1);
-	}
 
-	let lowerSteps = 0;
+	let f0 = t0.secondManoeuvre.time - expectedTime;
-	let lowerTransfer = lambertSolutions.getTransfer(getGamma(lowerSteps));
+	let f1 = t1.secondManoeuvre.time - expectedTime;
-	let lowerTime = 0;
 
-	let upperSteps = 1;
+	let f2 = 100;
-	let upperTransfer = lambertSolutions.getTransfer(getGamma(upperSteps));
+	let t2 = null;
-	let upperTime = upperTransfer.secondManoeuvre.time;
 
-	let foundWindow = false;
+	let counter = 0;
-	// Find window that contains transfer
+
-	for (let windowAttempts = 0; windowAttempts < 100; windowAttempts++) {
+	while (Math.abs(f2) > 0.5 && counter < 100) {
-		if (upperTime < 0 || expectedTime < upperTime) {
+		counter++;
-			foundWindow = true;
+		let divisor = 1;
+		let step = f1 * (x1 - x0) / (f1 - f0);
+
+		let manoeuvreTime = -1;
+		let x2 = 0;
+		let innerCounter = 0;
+		while ((isNaN(manoeuvreTime) || manoeuvreTime < 0) && innerCounter < 10) {
+			innerCounter++;
+			x2 = x1 - step / (2**divisor);
+			t2 = lambertSolutions.getTransfer(x2);
+			manoeuvreTime = t2.secondManoeuvre.time;
+			divisor += 1;
+		}
+
+		if (innerCounter == 10) {
 			break;
 		}
 
-		lowerSteps = upperSteps;
+		f2 = manoeuvreTime - expectedTime;
-		lowerTransfer = upperTransfer;
-		lowerTime = upperTime;
 
-		upperSteps += 1;
+		x0 = x1;
-		upperTransfer = lambertSolutions.getTransfer(getGamma(upperSteps));
+		x1 = x2;
-		upperTime = upperTransfer.secondManoeuvre.time;
+		f0 = f1;
+		f1 = f2;
 	}
 
-	if (!foundWindow) {
+	if (Math.abs(f2) <= 0.5) {
+		return t2;
+	} else {
 		return null;
 	}
-
-	const acceptablyClose = 0.5;
-	const numberOfAttempts = 200;
-
-	for (let attempts = 0; attempts < numberOfAttempts; attempts++) {
-		if (Math.abs(lowerTime - expectedTime) < acceptablyClose) {
-			return lowerTransfer;
-		}
-
-		if (Math.abs(upperTime - expectedTime) < acceptablyClose) {
-			return upperTransfer;
-		}
-
-		let middleSteps = (upperSteps + lowerSteps) / 2;
-		let middleTransfer = lambertSolutions.getTransfer(getGamma(middleSteps));
-		let middleTime = middleTransfer.secondManoeuvre.time;
-
-		if (middleTime > 0 && middleTime < expectedTime) {
-			lowerSteps = middleSteps;
-			lowerTransfer = middleTransfer;
-			lowerTime = middleTime;
-		} else {
-			upperSteps = middleSteps;
-			upperTransfer = middleTransfer;
-			upperTime = middleTime;
-		}
-	}
-
-	return null;
 }
 
 export function findCheapestIntercept(startingSituation: OrbitalCoordinates, targetSituation: OrbitalCoordinates, body: Body, extraTrueAnomaly: number, progressCallback?: ProgressCallbackFunction): Transfer | null {
@@ -823,12 +849,14 @@ export function findCheapestIntercept(startingSituation: OrbitalCoordinates, tar
 		if (!startingOrbitStable) {
 			maxStartTrueAnomaly = Math.abs(Math.acos((startingSituation.orbit.semiLatusRectum - body.sphereOfInfluence) / (body.sphereOfInfluence * startingSituation.orbit.eccentricity)));
 			maxStartTime = getTimeBetweenTrueAnomalies(startingSituation.trueAnomaly, maxStartTrueAnomaly, startingSituation.orbit, body);
-			maxEndTime = 2*maxStartTime;
 		}
 
 		if (!interceptOrbitStable) {
 			maxEndTrueAnomaly = Math.abs(Math.acos((targetSituation.orbit.semiLatusRectum - body.sphereOfInfluence) / (body.sphereOfInfluence * targetSituation.orbit.eccentricity)));
 			maxEndTime = getTimeBetweenTrueAnomalies(targetSituation.trueAnomaly, maxEndTrueAnomaly, targetSituation.orbit, body);
+		} else {
+			// Set the max end time to the max start time plus two full orbits of the target
+			maxEndTime = maxStartTime + 4 * Math.PI * Math.sqrt((targetSituation.orbit.semiLatusRectum / (1 - targetSituation.orbit.eccentricity**2))**3 / body.gravitationalParameter);
 		}
 	}
 
@@ -900,3 +928,486 @@ export function findCheapestIntercept(startingSituation: OrbitalCoordinates, tar
 	
 	return bestTransfer;
 }
+
+export function findCheapestLanding(startingCoordinates: OrbitalCoordinates, startTime: number, ship: ShipParameters, landingParameters: LandingParameters, body: Body, progressCallback?: LandingProgressCallbackFunction): Landing | null {
+	// Starting points are a list of true anomalies with corresponding times
+	let startingPoints: [number, number][] = [];
+
+	let minimumStartingTrueAnomaly = startingCoordinates.trueAnomaly;
+	let maximumStartingTrueAnomaly = startingCoordinates.trueAnomaly + 2 * Math.PI;
+
+	let boundedAbove = false;
+
+	// Check if we're on a collision course with the planet
+	let minimumAltitude = startingCoordinates.orbit.semiLatusRectum / (1 + startingCoordinates.orbit.eccentricity);
+
+	// If we're colliding, we need to do our manoeuvre quickly
+	if (minimumAltitude < body.closestSafeDistance) {
+		let criticalAnomaly = Math.acos((startingCoordinates.orbit.semiLatusRectum - body.closestSafeDistance) / (body.closestSafeDistance * startingCoordinates.orbit.eccentricity));
+
+		// We might be in a weird orbit where we're on the way away from the planet, in which case we shouldn't bound our starting
+		if (minimumStartingTrueAnomaly < -criticalAnomaly) {
+			boundedAbove = true;
+			maximumStartingTrueAnomaly = -criticalAnomaly;
+		}
+	}
+
+	// If we're on a parabolic or hyperbolic orbit, or one that will leave the planet's sphere of influence, set an upper bound for the anomaly
+	if (!boundedAbove) {
+		let goesOutsideSphereOfIncluence = false;
+		if (startingCoordinates.orbit.eccentricity < 1) {
+			let maximumAltitude = startingCoordinates.orbit.semiLatusRectum / (1 - startingCoordinates.orbit.eccentricity);
+			if (maximumAltitude > body.sphereOfInfluence) {
+				goesOutsideSphereOfIncluence = true;
+			}
+		} else {
+			goesOutsideSphereOfIncluence = true;
+		}
+
+		if (goesOutsideSphereOfIncluence) {
+			maximumStartingTrueAnomaly = Math.acos((startingCoordinates.orbit.semiLatusRectum - body.sphereOfInfluence) / (body.sphereOfInfluence * startingCoordinates.orbit.eccentricity));
+		}
+	}
+
+	// Our set of starting points is decided
+	let stepLength = (maximumStartingTrueAnomaly - minimumStartingTrueAnomaly) /  100.0;
+	for (let i = 0; i < 100; i++) {
+		let testAnomaly = minimumStartingTrueAnomaly + i * stepLength;
+		let timeUntilAnomaly = getTimeBetweenTrueAnomalies(minimumStartingTrueAnomaly, testAnomaly, startingCoordinates.orbit, body);
+		startingPoints.push([testAnomaly, timeUntilAnomaly + startTime]);
+	};
+
+	let bestLanding: Landing | null = null;
+	let bestLandingDeltaV: number | null = null;
+
+	// We need to simulate the ship braking, in order to refine the manoeuvre
+	const simulateBraking = (transferTrueAnomaly: number, transferOrbit: Orbit, body: Body, ship: ShipParameters) => {
+		let localVectors = getLocalVectors(transferTrueAnomaly, transferOrbit);
+		let speed = getSpeed(transferTrueAnomaly, transferOrbit, body);
+		let velocity = multiplyMatrixWithScalar(speed, localVectors.prograde);
+
+		let radius = transferOrbit.semiLatusRectum / (1 + transferOrbit.eccentricity * Math.cos(transferTrueAnomaly));
+		let localX = radius * Math.cos(transferTrueAnomaly);
+		let localY = radius * Math.sin(transferTrueAnomaly);
+
+		let startingPosition = addVector(
+			multiplyMatrixWithScalar(localX, transferOrbit.coordinateAxes[0]),
+			multiplyMatrixWithScalar(localY, transferOrbit.coordinateAxes[1])
+		);
+
+		let position = startingPosition;
+
+		let mass = ship.mass;
+		let massUse = ship.thrust / ship.specificImpulse;
+
+		let timeSteps = 0;
+		let lengthOfStep = 0.01;
+
+		let totalDeltaV = 0;
+
+		while (true) {
+			let radius = getVectorMagnitude(position);
+			let downwardsVector = multiplyMatrixWithScalar(-1 / radius, position);
+			let gravityAcceleration = body.gravitationalParameter / radius**2;
+			let gravityVector = multiplyMatrixWithScalar(gravityAcceleration, downwardsVector);
+
+			let latitude = Math.atan2(position[2][0], Math.sqrt(position[0][0]**2 + position[1][0]**2));
+			let longitude = Math.atan2(position[1][0], position[0][0]);
+
+			let surfaceSpeed = body.radius * Math.cos(latitude) * 2 * Math.PI / body.rotationPeriod;
+			let surfaceVelocity = [
+				[-surfaceSpeed * Math.sin(longitude)],
+				[surfaceSpeed * Math.cos(longitude)],
+				[0]
+			];
+
+			let excessVelocity = subtractVector(velocity, surfaceVelocity);
+			let excessSpeed = getVectorMagnitude(excessVelocity);
+
+			let engineAcceleration = ship.thrust / mass;
+			if (excessSpeed < lengthOfStep * engineAcceleration) {
+				break;
+			}
+
+			let engineAccelerationVector = multiplyMatrixWithScalar(-engineAcceleration, normalizeVector(excessVelocity));
+			let totalAcceleration = addVector(engineAccelerationVector, gravityVector);
+
+			position = addVector(position, addVector(multiplyMatrixWithScalar(lengthOfStep, velocity), multiplyMatrixWithScalar(lengthOfStep**2 / 2, totalAcceleration)));
+			velocity = addVector(velocity, multiplyMatrixWithScalar(lengthOfStep, totalAcceleration));
+			mass -= massUse * lengthOfStep;
+			totalDeltaV += engineAcceleration * lengthOfStep;
+
+			if (mass < 0) {
+				return null;
+			}
+
+			timeSteps += 1;
+		}
+
+		return {
+			timeSpent: timeSteps * lengthOfStep,
+			finalPosition: position,
+			deltaVSpent: totalDeltaV
+		};
+	};
+
+	const createFakeOrbit = (position: number[][]): Orbit => {
+		let radius = getVectorMagnitude(position);
+		let longitude = Math.atan2(position[1][0], position[0][0]);
+		let latitude = Math.atan2(position[2][0], Math.sqrt(position[0][0]**2 + position[1][0]**2));
+
+		if (latitude > 0) {
+			return getOrbit(radius, radius, latitude, longitude - Math.PI / 2, Math.PI / 2);
+		} else {
+			return getOrbit(radius, radius, -latitude, longitude + Math.PI / 2, -Math.PI / 2);
+		}
+	}
+
+	let freefallMultiplier = Math.PI / (2 * Math.sqrt(2 * body.gravitationalParameter));
+	startingPoints.forEach(([trueAnomaly, startTime], startingIndex) => {
+		// Test 100 different landing times at each true anomaly. We'll set the upper bound for the transfer time to be one and a
+		// half the time it takes to free fall from the current position
+		let currentRadius = startingCoordinates.orbit.semiLatusRectum / (1 + startingCoordinates.orbit.eccentricity * Math.cos(trueAnomaly));
+		let freeFallTime = freefallMultiplier * currentRadius ** (3 / 2);
+
+		for (let i = 1; i < 101; i++) {
+			let targetTime = 1.5 * freeFallTime * i / 100;
+			let rotatedTargetLongitude = landingParameters.targetLongitude + body.initialMeridianLongitude + (targetTime + startTime) * 2 * Math.PI / body.rotationPeriod;
+
+			let targetX = (landingParameters.targetAltitude + body.radius) * Math.cos(landingParameters.targetLatitude) * Math.cos(rotatedTargetLongitude);
+			let targetY = (landingParameters.targetAltitude + body.radius) * Math.cos(landingParameters.targetLatitude) * Math.sin(rotatedTargetLongitude);
+			let targetZ = (landingParameters.targetAltitude + body.radius) * Math.sin(landingParameters.targetLatitude);
+
+			let target = [[targetX], [targetY], [targetZ]];
+
+			// Make up an orbit that goes through this point, so we can use it with the Lambert solver I made earlier that always
+			// assumes you want to go between two orbits
+			let fakeTargetOrbit = createFakeOrbit(target);
+
+			[true, false].forEach(backwards => {
+				let lambertSolutions = new LambertSolutions(startingCoordinates.orbit, trueAnomaly, fakeTargetOrbit, 0, body, backwards);
+				let possibleTransfer = findLambertSolutionsWithCorrectTime(lambertSolutions, targetTime);
+
+				if (possibleTransfer) {
+					// Throw out any transfers that go below the surface and come up on our rendezvous
+					if (possibleTransfer.closestPointDistance < landingParameters.targetAltitude + body.radius - 1) {
+						return;
+					}
+
+					// Check if the transfer comes in steep enough
+					let localVectors = getLocalVectors(possibleTransfer.transferOrbitTrueanomalyAtManoeuvreTwo, possibleTransfer.transferOrbit);
+					let targetDownwardsVector = multiplyMatrixWithScalar(-1, normalizeVector(target));
+
+					let maximumAngle = Math.PI / 2 - landingParameters.minimumAngle;
+					let angle = Math.acos(vectorDotProduct(localVectors.prograde, targetDownwardsVector));
+					if (angle > maximumAngle) {
+						return;
+					}
+
+					// Do some iterative searching to find a transfer that lands in the middle
+					let foundGoodLanding = false;
+					let previousTargetPosition = target;
+					let previousTargetTime = targetTime;
+
+					let landingCounter = 0;
+
+					while (!foundGoodLanding && landingCounter < 100) {
+						landingCounter++;
+						let massAfterTransfer = ship.mass / (Math.exp(possibleTransfer.firstManoeuvre.totalDeltaV / (9.81 * ship.specificImpulse)));
+						let testShip: ShipParameters = {
+							thrust: ship.thrust,
+							mass: massAfterTransfer,
+							specificImpulse: ship.specificImpulse
+						};
+
+						let simulationResult = simulateBraking(possibleTransfer.transferOrbitTrueanomalyAtManoeuvreTwo, possibleTransfer.transferOrbit, body, testShip);
+						if (simulationResult == null) {
+							return;
+						}
+						let difference = subtractVector(simulationResult.finalPosition, target);
+						let timeDifference = possibleTransfer.secondManoeuvre.time + simulationResult.timeSpent - targetTime;
+						let differenceMagnitude = getVectorMagnitude(difference);
+
+						if (timeDifference > 100 || differenceMagnitude > 10) {
+							// We're too far away, try another maneuver
+							let newTarget = subtractVector(previousTargetPosition, difference);
+							let newTime = previousTargetTime - timeDifference;
+							let newTargetOrbit = createFakeOrbit(newTarget);
+
+							previousTargetPosition = newTarget;
+							previousTargetTime = newTime;
+
+							lambertSolutions = new LambertSolutions(startingCoordinates.orbit, trueAnomaly, newTargetOrbit, 0, body, backwards);
+							possibleTransfer = findLambertSolutionsWithCorrectTime(lambertSolutions, newTime);
+
+							if (!possibleTransfer) {
+								return;
+							}
+						} else {
+							foundGoodLanding = true;
+
+							possibleTransfer.firstManoeuvre.time += startTime;
+							possibleTransfer.secondManoeuvre.time += startTime;
+
+							let totalDeltaV = possibleTransfer.firstManoeuvre.totalDeltaV + simulationResult.deltaVSpent;
+							if (bestLandingDeltaV == null || totalDeltaV < bestLandingDeltaV) {
+								let secondManoeuvreAltitude = possibleTransfer.transferOrbit.semiLatusRectum / (1 + possibleTransfer.transferOrbit.eccentricity * Math.cos(possibleTransfer.transferOrbitTrueanomalyAtManoeuvreTwo)) - body.radius;
+
+								let landing: Landing = {
+									transferOrbit: possibleTransfer.transferOrbit,
+									transferManoeuvre: possibleTransfer.firstManoeuvre,
+									brakingDeltaV: simulationResult.deltaVSpent,
+									brakingAltitude: secondManoeuvreAltitude,
+									brakingTimestamp: possibleTransfer.secondManoeuvre.time,
+									totalDeltaV: totalDeltaV
+								};
+
+								bestLanding = landing;
+								bestLandingDeltaV = totalDeltaV;
+							}
+						}
+					};
+				}
+			});
+
+			if (progressCallback) {
+				progressCallback(startingIndex * 100 + i, 100*100, bestLandingDeltaV, bestLanding);
+			}
+		}
+	});
+
+	return bestLanding;
+}
+
+export function findOrbitThroughInterpolation(ownCoordinates: OrbitalCoordinates, interpolationParameters: InterpolationParameters, body: Body): [OrbitalCoordinates, number] | null {
+	let targetPeriapsis = interpolationParameters.targetPeriapsis;
+
+	let targetEccentricity;
+	let targetSemiLatusRectum;
+	if (interpolationParameters.orbitChoice == "apoapsis") {
+		let targetApoapsis = interpolationParameters.targetApoapsis;
+		const semiMajor = (targetPeriapsis + targetApoapsis) / 2;
+		const linearEccentricity = semiMajor - targetPeriapsis;
+		targetEccentricity = linearEccentricity / semiMajor;
+		targetSemiLatusRectum = semiMajor * (1 - targetEccentricity**2);
+	} else {
+		let semiMajorInverse = 2 / interpolationParameters.targetAltitude - interpolationParameters.targetSpeed**2 / body.gravitationalParameter;
+		
+		// If this is zero, we have a parabolic trajectory
+		if (Math.abs(semiMajorInverse) < 0.0001) {
+			targetEccentricity = 1;
+			targetSemiLatusRectum = 2 * targetPeriapsis;
+		} else {
+			let semiMajor = 1 / semiMajorInverse;
+			// If this is positive, we have an elliptical orbit
+			if (semiMajor > 0) {
+				const linearEccentricity = semiMajor - targetPeriapsis;
+				targetEccentricity = linearEccentricity / semiMajor;
+				targetSemiLatusRectum = semiMajor * (1 - targetEccentricity**2);
+			} else {
+				const linearEccentricity = semiMajor + targetPeriapsis;
+				targetEccentricity = linearEccentricity / semiMajor;
+				targetSemiLatusRectum = semiMajor * (targetEccentricity**2 - 1);
+			}
+		}
+	}
+
+	// Now, we have a pretty good description of the orbit, we only need to find the plane it lies in
+	// Given the first measurement of distance to planet, distance to target, and target to planet, there exists a circle
+	// that the target could be in
+	let ownShipHeadedInwards = interpolationParameters.secondOwnAltitude < interpolationParameters.firstOwnAltitude;
+	let targetHeadedInwards = interpolationParameters.secondTargetAltitude < interpolationParameters.firstTargetAltitude;
+
+	// Define some helper functions for later
+	const getRandomPerpendicularVector = (vector: number[][]) => {
+		let perpendicularX = Math.random();
+		let perpendicularY = Math.random();
+		let perpendicularZ = Math.random();
+
+		let normalVector: number[][];
+		if (Math.abs(vector[0][0]) > 0.0001) {
+			normalVector = [
+				[(-vector[1][0] * perpendicularY - vector[2][0]*perpendicularZ) / vector[0][0]],
+				[perpendicularY],
+				[perpendicularZ]
+			];
+		} else if (Math.abs(vector[1][0]) > 0.0001) {
+			normalVector = [
+				[perpendicularX],
+				[(-vector[0][0] / perpendicularX - vector[2][0] / perpendicularZ) / vector[1][0]],
+				[perpendicularZ]
+			];
+		} else {
+			normalVector = [
+				[perpendicularX],
+				[perpendicularY],
+				[(-vector[0][0] * perpendicularX - vector[1][0] * perpendicularY) / vector[2][0]]
+			]
+		};
+
+		return normalizeVector(normalVector);
+	};
+
+	const getTrueAnomalyFromAltitude = (altitude: number, semiLatusRectum: number, eccentricity: number, headingInwards: boolean) => {
+		let trueAnomaly = Math.acos((semiLatusRectum - altitude) / (altitude * eccentricity));
+		if (headingInwards) {
+			trueAnomaly = -trueAnomaly;
+		}
+		return trueAnomaly;
+	}
+
+
+	const getPossibleTargetLocationFunction = (ownOrbit: Orbit, ownAltitude: number, targetAltitude: number, distanceToTarget: number): ((angle: number) => number[][]) => {
+		let ownTrueAnomaly = getTrueAnomalyFromAltitude(ownAltitude, ownOrbit.semiLatusRectum, ownOrbit.eccentricity, ownShipHeadedInwards);
+
+		let ownLocalX = interpolationParameters.firstOwnAltitude * Math.cos(ownTrueAnomaly);
+		let ownLocalY = interpolationParameters.firstOwnAltitude * Math.sin(ownTrueAnomaly);
+
+		let ownDirection = normalizeVector(
+			addVector(
+				multiplyMatrixWithScalar(ownLocalX, ownOrbit.coordinateAxes[0]),
+				multiplyMatrixWithScalar(ownLocalY, ownOrbit.coordinateAxes[1])
+			)
+		);
+
+		let perpendicularOne = getRandomPerpendicularVector(ownDirection);
+		let perpendicularTwo = normalizeVector(vectorCrossProduct(ownDirection, perpendicularOne));
+
+		// Find phase angle to target
+		let phaseAngle = Math.acos((ownAltitude**2 + targetAltitude**2 - distanceToTarget**2) / (2 * ownAltitude * targetAltitude));
+
+		let distanceAlongDirection = targetAltitude * Math.cos(phaseAngle);
+		let distanceAlongNormal = targetAltitude * Math.sin(phaseAngle);
+
+		let root = multiplyMatrixWithScalar(distanceAlongDirection, ownDirection);
+
+		return function(angle: number) {
+			let addition = addVector(
+				multiplyMatrixWithScalar(distanceAlongNormal * Math.cos(angle), perpendicularOne),
+				multiplyMatrixWithScalar(distanceAlongNormal * Math.sin(angle), perpendicularTwo)
+			);
+
+			return addVector(root, addition);
+		}
+	}
+
+	let firstTargetFunction = getPossibleTargetLocationFunction(ownCoordinates.orbit, interpolationParameters.firstOwnAltitude, interpolationParameters.firstTargetAltitude, interpolationParameters.firstDistance);
+	let secondTargetFunction = getPossibleTargetLocationFunction(ownCoordinates.orbit, interpolationParameters.secondOwnAltitude, interpolationParameters.secondTargetAltitude, interpolationParameters.secondDistance);
+
+	// Since we know a lot about the target orbit, we can figure out how far it is supposed to be between the two points
+	let firstTargetTrueAnomaly = getTrueAnomalyFromAltitude(interpolationParameters.firstTargetAltitude, targetSemiLatusRectum, targetEccentricity, targetHeadedInwards);
+	let secondTargetTrueAnomaly = getTrueAnomalyFromAltitude(interpolationParameters.secondTargetAltitude, targetSemiLatusRectum, targetEccentricity, targetHeadedInwards);
+
+	// Use cosine rule
+	let targetMovement = Math.sqrt(interpolationParameters.firstTargetAltitude**2 + interpolationParameters.secondTargetAltitude**2 - 2 * interpolationParameters.firstTargetAltitude * interpolationParameters.secondTargetAltitude * Math.cos(secondTargetTrueAnomaly - firstTargetTrueAnomaly));
+
+	// Now, we need to do multivariate optimization to find the two angles to give to the functions that make the distance between
+	// two target positions as equal to the target movement as possible
+	const functionToOptimize = (angleOne: number, angleTwo: number) => {
+		let firstTargetPosition = firstTargetFunction(angleOne);
+		let secondTargetPosition = secondTargetFunction(angleTwo);
+
+		return Math.abs(getVectorMagnitude(subtractVector(secondTargetPosition, firstTargetPosition)) - targetMovement);
+	}
+
+	let bestAngleOne = 0;
+	let bestAngleTwo = 0;
+	let bestValue = 1e99;
+
+	for (var i = 0; i < 100; i++) {
+		for (var j = 0; j < 100; j++) {
+			let angleOne = 2 * Math.PI * i / 100;
+			let angleTwo = 2 * Math.PI * j / 100;
+
+			let value = functionToOptimize(angleOne, angleTwo);
+			if (value < bestValue) {
+				bestAngleOne = angleOne;
+				bestAngleTwo = angleTwo;
+				bestValue = value;
+			}
+		}
+	}
+
+	// Do some gradient descent on the best values found so far
+	while (bestValue > 0.5) {
+		let estimateDfDx = (functionToOptimize(bestAngleOne+0.0000001, bestAngleTwo) - bestValue) / 0.0000001;
+		let estimateDfDy = (functionToOptimize(bestAngleOne, bestAngleTwo+0.0000001) - bestValue) / 0.0000001;
+
+		let slopeNormal = vectorCrossProduct(
+			[[1], [0], [estimateDfDx]],
+			[[0], [1], [estimateDfDy]]
+		);
+
+		let direction = normalizeVector([[slopeNormal[0][0]], [slopeNormal[1][0]], [0]]);
+		let estimateDfDv = (functionToOptimize(bestAngleOne + direction[0][0]*0.0001, bestAngleTwo + direction[1][0]*0.0001) - bestValue) / 0.0001;
+
+		let bestValueImprovement = bestValue;
+		let bestAngleOneUpdate = bestAngleOne;
+		let bestAngleTwoUpdate = bestAngleTwo;
+		let divisor = 0;
+		let deadEnd = false;
+
+		while (bestValueImprovement >= bestValue) {
+			bestAngleOneUpdate = bestAngleOne - bestValue * direction[0][0] / (estimateDfDv * 2**divisor);
+			bestAngleTwoUpdate = bestAngleTwo - bestValue * direction[1][0] / (estimateDfDv * 2**divisor);
+			bestValueImprovement = functionToOptimize(bestAngleOneUpdate, bestAngleTwoUpdate);
+			divisor += 1;
+
+			if (divisor >= 32) {
+				deadEnd = true;
+				break;
+			}
+		}
+
+		if (deadEnd) {
+			break;
+		}
+		bestAngleOne = bestAngleOneUpdate;
+		bestAngleTwo = bestAngleTwoUpdate;
+		bestValue = bestValueImprovement;
+	}
+
+	let bestFirstPosition = firstTargetFunction(bestAngleOne);
+	let bestSecondPosition = secondTargetFunction(bestAngleTwo);
+
+	if (bestFirstPosition == null || bestSecondPosition == null) {
+		return null;
+	}
+	// We can now find the vector that defines the plane the target is in
+	let normalVector = normalizeVector(vectorCrossProduct(bestFirstPosition, bestSecondPosition));
+	let firstTargetPositionDirection = normalizeVector(bestFirstPosition);
+
+	// Rotate the position vector about the normal vector by the true anomaly to find the vector pointing to the periapsis
+	let identityMatrix = [[1, 0, 0], [0, 1, 0], [0, 0, 1]];
+	let crossProductMatrix = [
+		[0, -normalVector[2][0], normalVector[1][0]],
+		[normalVector[2][0], 0, -normalVector[0][0]],
+		[-normalVector[1][0], normalVector[0][0], 0]
+	];
+	let outerProductMatrix = [
+		[normalVector[0][0]**2, normalVector[0][0]*normalVector[1][0], normalVector[0][0]*normalVector[2][0]],
+		[normalVector[0][0]*normalVector[1][0], normalVector[1][0]**2, normalVector[1][0]*normalVector[2][0]],
+		[normalVector[0][0]*normalVector[2][0], normalVector[1][0]*normalVector[2][0], normalVector[2][0]**2]
+	];
+
+	let rotationMatrix = addMatrix(
+		multiplyMatrixWithScalar(Math.cos(-firstTargetTrueAnomaly), identityMatrix),
+		addMatrix(
+			multiplyMatrixWithScalar(Math.sin(-firstTargetTrueAnomaly), crossProductMatrix),
+			multiplyMatrixWithScalar(1 - Math.cos(-firstTargetTrueAnomaly), outerProductMatrix)
+		)
+	);
+
+	let targetOrbitXVector = matrixMultiply(rotationMatrix, firstTargetPositionDirection);
+	let targetOrbitYVector = vectorCrossProduct(normalVector, targetOrbitXVector);
+
+	let targetOrbit: Orbit = {
+		semiLatusRectum: targetSemiLatusRectum,
+		eccentricity: targetEccentricity,
+		coordinateAxes: [targetOrbitXVector, targetOrbitYVector, normalVector]
+	};
+
+	let timePassed = getTimeBetweenTrueAnomalies(ownCoordinates.trueAnomaly, getTrueAnomalyFromAltitude(interpolationParameters.secondOwnAltitude, ownCoordinates.orbit.semiLatusRectum, ownCoordinates.orbit.eccentricity, ownShipHeadedInwards), ownCoordinates.orbit, body);
+
+	return [getOrbitalCoordinatesFromAltitude(interpolationParameters.secondTargetAltitude, targetHeadedInwards, targetOrbit, body), timePassed];
+}

src/gui/common.ts

@@ -1,5 +1,5 @@
 import type { Body } from "../calculations/constants";
-import { getOrbit, getOrbitalCoordinates, getOrbitalCoordinatesFromAltitude, getOrbitFromEccentricity, type Orbit, type OrbitalCoordinates } from "../calculations/orbit-calculations";
+import { getOrbit, getOrbitalCoordinates, getOrbitalCoordinatesFromAltitude, getOrbitFromEccentricity, type LandingParameters, type Orbit, type OrbitalCoordinates } from "../calculations/orbit-calculations";
 
 export interface OrbitalParameters {
 	periapsis: number;
@@ -33,20 +33,26 @@ export const DefaultOrbitalParameters: OrbitalParameters = {
 	currentTimeAtReading: 0
 }
 
-export function encodeOrbitalParameters(orbitalParameters: OrbitalParameters): string {
+export const DefaultLandingParameters: LandingParameters = {
-	return JSON.stringify(orbitalParameters);
+	targetLatitude: 0,
+	targetLongitude: 0,
+	targetAltitude: 0,
+	minimumAngle: Math.PI / 4
+};
+
+export function encodeJsonObject<Type>(object: Type): string {
+	return JSON.stringify(object);
 }
 
-export function decodeOrbitalParameters(jsonString: string): OrbitalParameters {
+export function getDecoderFunction<Type>(defaultValue: Type): (jsonString: string) => Type {
-	let parsedObject = JSON.parse(jsonString);
+	return function(jsonString: string): Type {
-	var orbitalParameters: OrbitalParameters;
+		let parsedObject = JSON.parse(jsonString);
-	if (parsedObject as OrbitalParameters === undefined) {
+		if (parsedObject as Type === undefined) {
-		orbitalParameters = DefaultOrbitalParameters;
+			return defaultValue;
-	} else {
+		} else {
-		orbitalParameters = parsedObject;
+			return parsedObject;
+		}
 	}
-
-	return orbitalParameters;
 }
 
 export function createLabel(forId: string, labelText: string): HTMLLabelElement {

src/gui/intercept.ts

@@ -1,10 +1,20 @@
-import { createLabel, createNumberInput, getCoordinatesFromParameters, type OrbitalParameters } from "./common";
+import { createLabel, createNumberInput, createRadioButton, getCoordinatesFromParameters, type OrbitalParameters } from "./common";
 import { OrbitalParametersGui } from "./orbit";
 import { type Body } from "../calculations/constants";
 import type { FindBestInterceptMessage, ProgressMessage } from "./worker";
 import type { ChangingStorageValue } from "../storage";
 import { ManoeuvresGui } from "./manoeuvres";
-import { extrapolateTrajectory, type OrbitalCoordinates } from "../calculations/orbit-calculations";
+import { extrapolateTrajectory, findOrbitThroughInterpolation, type OrbitalCoordinates } from "../calculations/orbit-calculations";
+import { InterpolateOrbitGui, type InterpolationParameters } from "./interpolate";
+
+export type TargetOrbitChoice = "KnownOrbit" | "InterpolateOrbit";
+export function decodeTargetOrbitChoice(s: string): TargetOrbitChoice {
+	if (s == "KnownOrbit" || s == "InterpolateOrbit") {
+		return s;
+	}
+
+	return "KnownOrbit";
+}
 
 export class InterceptTargetGui {
 	currentTime: ChangingStorageValue<number>;
@@ -12,33 +22,72 @@ export class InterceptTargetGui {
 	startingOrbitalParameters: ChangingStorageValue<OrbitalParameters>;
 	targetOrbitalParameters: ChangingStorageValue<OrbitalParameters>;
 	additionalTrueAnomaly: ChangingStorageValue<number>;
+	targetOrbitChoice: ChangingStorageValue<TargetOrbitChoice>;
+	interpolationParameters: ChangingStorageValue<InterpolationParameters>;
 
 	parentDiv: HTMLDivElement;
 	orbitGui: OrbitalParametersGui;
+	interpolateGui: InterpolateOrbitGui;
 	manoeuvresGui: ManoeuvresGui;
 
 	sourceId: string;
 
 	worker: Worker | null;
 
-	constructor(currentTime: ChangingStorageValue<number>, body: ChangingStorageValue<Body>, startingOrbitalParameters: ChangingStorageValue<OrbitalParameters>, targetOrbitalParameters: ChangingStorageValue<OrbitalParameters>, additionalTrueAnomaly: ChangingStorageValue<number>) {
+	constructor(currentTime: ChangingStorageValue<number>, body: ChangingStorageValue<Body>, startingOrbitalParameters: ChangingStorageValue<OrbitalParameters>, targetOrbitalParameters: ChangingStorageValue<OrbitalParameters>, additionalTrueAnomaly: ChangingStorageValue<number>, targetOrbitChoice: ChangingStorageValue<TargetOrbitChoice>, interpolationParameters: ChangingStorageValue<InterpolationParameters>) {
 		this.currentTime = currentTime;
 		this.body = body;
 		this.startingOrbitalParameters = startingOrbitalParameters;
 		this.targetOrbitalParameters = targetOrbitalParameters;
 		this.additionalTrueAnomaly = additionalTrueAnomaly;
+		this.targetOrbitChoice = targetOrbitChoice;
+		this.interpolationParameters = interpolationParameters;
 
 		this.orbitGui = new OrbitalParametersGui(targetOrbitalParameters, "orbitWithPosition");
+		this.interpolateGui = new InterpolateOrbitGui(this.interpolationParameters);
 		this.manoeuvresGui = new ManoeuvresGui(true);
 
 		this.worker = null;
 
 		this.parentDiv = document.createElement("div");
+		let choiceHeader = document.createElement("h3")
+		choiceHeader.appendChild(document.createTextNode("Choose target orbit type"));
+
+		this.parentDiv.appendChild(choiceHeader);
+
+		let targetChoiceId = crypto.randomUUID();
+		let knownOrbitId = crypto.randomUUID();
+		let knownOrbitButton = createRadioButton(targetChoiceId, knownOrbitId);
+		let knownOrbitLabel = createLabel(knownOrbitId, "Known orbit");
+		this.parentDiv.appendChild(knownOrbitButton);
+		this.parentDiv.appendChild(knownOrbitLabel);
+
+		let interpolateOrbitId = crypto.randomUUID();
+		let interpolateOrbitButton = createRadioButton(targetChoiceId, interpolateOrbitId);
+		let interpolateOrbitLabel = createLabel(interpolateOrbitId, "Interpolate orbit");
+		this.parentDiv.appendChild(interpolateOrbitButton);
+		this.parentDiv.appendChild(interpolateOrbitLabel);
+		
+		let orbitContainer = document.createElement("div");
+		this.parentDiv.appendChild(orbitContainer);
+		
+		let knownOrbitContainer = document.createElement("div");
+		
 		let parametersHeader = document.createElement("h3");
 		parametersHeader.appendChild(document.createTextNode("Target orbit:"));
-		this.parentDiv.appendChild(parametersHeader);
+		knownOrbitContainer.appendChild(parametersHeader);
+		knownOrbitContainer.appendChild(this.orbitGui.parentDiv);
 
-		this.parentDiv.appendChild(this.orbitGui.parentDiv);
+		let interpolateOrbitContainer = document.createElement("div");
+
+		let interpolateOrbitHeader = document.createElement("h3");
+		interpolateOrbitHeader.appendChild(document.createTextNode("Interpolate orbit:"));
+		interpolateOrbitContainer.appendChild(interpolateOrbitHeader);
+		interpolateOrbitContainer.appendChild(this.interpolateGui.parentDiv);
+
+		let offsetHeader = document.createElement("h3");
+		offsetHeader.appendChild(document.createTextNode("Offset:"));
+		this.parentDiv.appendChild(offsetHeader);
 
 		let additionalTrueAnomalyContainer = document.createElement("div");
 		additionalTrueAnomalyContainer.classList.add("orbitalParameter");
@@ -49,7 +98,6 @@ export class InterceptTargetGui {
 		let additionalTrueAnomalyInput = createNumberInput(additionalTrueAnomalyId, -360, 360);
 		[additionalTrueanomalyLabel, additionalTrueAnomalyInput].forEach(child => additionalTrueAnomalyContainer.appendChild(child));
 
-
 		let searchButton = document.createElement("button");
 		searchButton.appendChild(document.createTextNode("Search for cheapest intercept"));
 		this.parentDiv.appendChild(searchButton);
@@ -72,25 +120,52 @@ export class InterceptTargetGui {
 				let body = this.body.getCurrentValue();
 				let startingOrbitalParameters = this.startingOrbitalParameters.getCurrentValue();
 				let targetOrbitalParameters = this.targetOrbitalParameters.getCurrentValue();
+				let additionalTrueAnomaly = this.additionalTrueAnomaly.getCurrentValue();
+				let targetOrbitChoice = this.targetOrbitChoice.getCurrentValue();
+				let interpolationParameters = this.interpolationParameters.getCurrentValue();
+
+				interpolationParameters = structuredClone(interpolationParameters);
+				interpolationParameters.firstOwnAltitude += body.radius;
+				interpolationParameters.firstTargetAltitude += body.radius;
+				interpolationParameters.secondOwnAltitude += body.radius;
+				interpolationParameters.secondTargetAltitude += body.radius;
+				interpolationParameters.targetAltitude += body.radius;
+				interpolationParameters.targetPeriapsis += body.radius;
+				interpolationParameters.targetApoapsis += body.radius;
+
 
 				let startingCoordinates: OrbitalCoordinates | null = getCoordinatesFromParameters(startingOrbitalParameters, body);
-				let targetCoordinates: OrbitalCoordinates | null = getCoordinatesFromParameters(targetOrbitalParameters, body);
+				let startTime: number | null = null;
 
-				let startTime = Math.max(currentTime, startingOrbitalParameters.currentTimeAtReading, targetOrbitalParameters.currentTimeAtReading);
+				let targetStartTime = 0;
 
-				if (startTime > startingOrbitalParameters.currentTimeAtReading) {
+				let targetCoordinates: OrbitalCoordinates | null = null;
-					let addedTime = startTime - startingOrbitalParameters.currentTimeAtReading;
+				if (targetOrbitChoice == "InterpolateOrbit") {
-					startingCoordinates = extrapolateTrajectory(addedTime, startingCoordinates, body);
+					let result = findOrbitThroughInterpolation(startingCoordinates, interpolationParameters, body);
+					if (result) {
+						targetCoordinates = result[0];
+						targetStartTime = startingOrbitalParameters.currentTimeAtReading + result[1];
+					}
+				} else if (targetOrbitChoice = "KnownOrbit") {
+					targetCoordinates = getCoordinatesFromParameters(targetOrbitalParameters, body);
+					targetStartTime = targetOrbitalParameters.currentTimeAtReading;
 				}
 
-				if (startTime > targetOrbitalParameters.currentTimeAtReading) {
-					let addedTime = startTime - targetOrbitalParameters.currentTimeAtReading;
-					targetCoordinates = extrapolateTrajectory(addedTime, targetCoordinates, body);
-				}
-
-				let additionalTrueAnomaly = this.additionalTrueAnomaly.getCurrentValue();
-
 				if (startingCoordinates && targetCoordinates) {
+					startTime = Math.max(currentTime, startingOrbitalParameters.currentTimeAtReading, targetStartTime);
+
+					if (startTime > startingOrbitalParameters.currentTimeAtReading) {
+						let addedTime = startTime - startingOrbitalParameters.currentTimeAtReading;
+						startingCoordinates = extrapolateTrajectory(addedTime, startingCoordinates, body);
+					}
+
+					if (startTime > targetStartTime) {
+						let addedTime = startTime - targetStartTime;
+						targetCoordinates = extrapolateTrajectory(addedTime, targetCoordinates, body);
+					}
+				}
+
+				if (startingCoordinates && targetCoordinates && startTime) {
 					this.worker = new Worker(new URL('./worker.ts', import.meta.url), {type: 'module'});
 					this.worker.addEventListener("message", event => {
 						let transferResponse = event.data as ProgressMessage;
@@ -101,8 +176,8 @@ export class InterceptTargetGui {
 							}
 
 							if (transferResponse.bestTransfer) {
-								transferResponse.bestTransfer.firstManoeuvre.time += currentTime;
+								transferResponse.bestTransfer.firstManoeuvre.time += startTime;
-								transferResponse.bestTransfer.secondManoeuvre.time += currentTime;
+								transferResponse.bestTransfer.secondManoeuvre.time += startTime;
 							}
 
 							this.manoeuvresGui.displayProgress(transferResponse);
@@ -143,5 +218,19 @@ export class InterceptTargetGui {
 			let additionalTrueAnomaly = parseFloat(additionalTrueAnomalyInput.value) * Math.PI / 180.0;
 			this.additionalTrueAnomaly.set(additionalTrueAnomaly, this.sourceId);
 		});
+
+		knownOrbitButton.addEventListener("change", () => targetOrbitChoice.set("KnownOrbit", this.sourceId));
+		interpolateOrbitButton.addEventListener("change", () => targetOrbitChoice.set("InterpolateOrbit", this.sourceId));
+
+		targetOrbitChoice.listenToValue((_, value) => {
+			orbitContainer.innerHTML = "";
+			if (value == "KnownOrbit") {
+				knownOrbitButton.setAttribute("checked", "");
+				orbitContainer.appendChild(knownOrbitContainer);
+			} else if (value == "InterpolateOrbit") {
+				interpolateOrbitButton.setAttribute("checked", "");
+				orbitContainer.appendChild(interpolateOrbitContainer);
+			}
+		});
 	}
 }

src/gui/interpolate.ts

@@ -0,0 +1,171 @@
+import type { ChangingStorageValue } from "../storage";
+import { createLabel, createNumberInput, createRadioButton } from "./common";
+
+export interface InterpolationParameters {
+	targetPeriapsis: number,
+	orbitChoice: "apoapsis" | "speedAndAltitude",
+	targetApoapsis: number,
+	targetSpeed: number,
+	targetAltitude: number,
+	firstOwnAltitude: number,
+	firstTargetAltitude: number,
+	firstDistance: number,
+	secondOwnAltitude: number,
+	secondTargetAltitude: number,
+	secondDistance: number,
+}
+
+export const DefaultInterpolationParameters: InterpolationParameters = {
+	targetPeriapsis: 100000,
+	orbitChoice: "apoapsis",
+	targetApoapsis: 200000,
+	targetSpeed: 0,
+	targetAltitude: 0,
+	firstOwnAltitude: 0,
+	firstTargetAltitude: 0,
+	firstDistance: 0,
+	secondOwnAltitude: 0,
+	secondTargetAltitude: 0,
+	secondDistance: 0
+}
+
+export class InterpolateOrbitGui {
+	parentDiv: HTMLDivElement;
+	interpolationParameters: ChangingStorageValue<InterpolationParameters>
+	sourceId: string;
+
+	constructor(interpolationParameters: ChangingStorageValue<InterpolationParameters>) {
+		this.parentDiv = document.createElement("div");
+		this.interpolationParameters = interpolationParameters;
+		
+		let targetOrbitHeader = document.createElement("h4");
+		targetOrbitHeader.appendChild(document.createTextNode("Describe target orbit:"));
+		this.parentDiv.appendChild(targetOrbitHeader);
+
+		let addToParent = (elements: HTMLElement[]) => {
+			let container = document.createElement("div");
+			container.classList.add("orbitalParameter");
+			elements.forEach(child => container.appendChild(child));
+			this.parentDiv.appendChild(container);
+		}
+
+		let createInputWithLabel = (label: string, minimum: number, maximum?: number, size?: number) => {
+			let inputId = crypto.randomUUID();
+			let labelElement = createLabel(inputId, label);
+			let numberInput = createNumberInput(inputId, minimum, maximum, size);
+			addToParent([labelElement, numberInput]);
+
+			return numberInput;
+		}
+
+		let periapsisInput = createInputWithLabel("Target peripasis:", 0);
+
+		let descriptorChoiceId = crypto.randomUUID();
+		let apoapsisButtonId = crypto.randomUUID();
+		let apoapsisButton = createRadioButton(descriptorChoiceId, apoapsisButtonId);
+		let apoapsisButtonLabel = createLabel(apoapsisButtonId, "Use apoapsis");
+
+		let speedAndAltitudeId = crypto.randomUUID();
+		let speedAndAltitudeButton = createRadioButton(descriptorChoiceId, speedAndAltitudeId);
+		let speedAndAltitudeLabel = createLabel(speedAndAltitudeId, "Use speed and altitude");
+		addToParent([apoapsisButton, apoapsisButtonLabel, speedAndAltitudeButton, speedAndAltitudeLabel]);
+
+		let apoapsisInput = createInputWithLabel("Target apopasis:", 0);
+		let speedInput = createInputWithLabel("Target speed:", 0);
+		let altitudeInput = createInputWithLabel("Target altitude:", 0);
+
+		let instantOneHeader = document.createElement("h4");
+		instantOneHeader.appendChild(document.createTextNode("Measurement one:"));
+		this.parentDiv.appendChild(instantOneHeader);
+
+		let firstOwnAltitudeInput = createInputWithLabel("Own altitude:", 0);
+		let firstTargetAltitudeInput = createInputWithLabel("Target altitude:", 0);
+		let firstDistanceInput = createInputWithLabel("Distance to target:", 0);
+
+		let instantTwoHeader = document.createElement("h4");
+		instantTwoHeader.appendChild(document.createTextNode("Measurement two:"));
+		this.parentDiv.appendChild(instantTwoHeader);
+
+		let secondOwnAltitudeInput = createInputWithLabel("Own altitude:", 0);
+		let secondTargetAltitudeInput = createInputWithLabel("Target altitude:", 0);
+		let secondDistanceInput = createInputWithLabel("Distance to target:", 0);
+
+		this.sourceId = crypto.randomUUID();
+		const onChange = () => {
+			let periapsis = parseFloat(periapsisInput.value);
+			let apoapsis = parseFloat(apoapsisInput.value);
+			let speed = parseFloat(speedInput.value);
+			let altitude = parseFloat(altitudeInput.value);
+			let firstTargetAltitude = parseFloat(firstTargetAltitudeInput.value);
+			let firstOwnAltitude = parseFloat(firstOwnAltitudeInput.value);
+			let firstDistance = parseFloat(firstDistanceInput.value);
+			let secondTargetAltitude = parseFloat(secondTargetAltitudeInput.value);
+			let secondOwnAltitude = parseFloat(secondOwnAltitudeInput.value);
+			let secondDistance = parseFloat(secondDistanceInput.value);
+
+			let orbitChoice: "apoapsis" | "speedAndAltitude" = "apoapsis";
+			if (speedAndAltitudeButton.checked) {
+				orbitChoice = "speedAndAltitude"
+			};
+
+			interpolationParameters.set({
+				targetPeriapsis: periapsis,
+				orbitChoice: orbitChoice,
+				targetApoapsis: apoapsis,
+				targetSpeed: speed,
+				targetAltitude: altitude,
+				firstTargetAltitude: firstTargetAltitude,
+				firstOwnAltitude: firstOwnAltitude,
+				firstDistance: firstDistance,
+				secondTargetAltitude: secondTargetAltitude,
+				secondOwnAltitude: secondOwnAltitude,
+				secondDistance: secondDistance,
+			}, this.sourceId)
+		};
+
+		[
+			periapsisInput,
+			apoapsisButton,
+			speedAndAltitudeButton,
+			apoapsisInput,
+			speedInput,
+			altitudeInput,
+			firstOwnAltitudeInput,
+			firstTargetAltitudeInput,
+			firstDistanceInput,
+			secondOwnAltitudeInput,
+			secondTargetAltitudeInput,
+			secondDistanceInput
+		].forEach(input => input.addEventListener("change", onChange));
+
+		interpolationParameters.listenToValue((source, value) => {
+			if (value.orbitChoice == "apoapsis") {
+				apoapsisInput.removeAttribute("disabled");
+				speedInput.setAttribute("disabled", "");
+				altitudeInput.setAttribute("disabled", "");
+				apoapsisButton.setAttribute("checked", "");
+			} else if (value.orbitChoice == "speedAndAltitude") {
+				apoapsisInput.setAttribute("disabled", "");
+				speedInput.removeAttribute("disabled");
+				altitudeInput.removeAttribute("disabled");
+				speedAndAltitudeButton.setAttribute("checked", "");
+			}
+
+			if (source == this.sourceId) {
+				return;
+			}
+
+			periapsisInput.value = value.targetPeriapsis.toString();
+			apoapsisInput.value = value.targetApoapsis.toString();
+			speedInput.value = value.targetSpeed.toString();
+			altitudeInput.value = value.targetAltitude.toString();
+			firstOwnAltitudeInput.value = value.firstOwnAltitude.toString();
+			firstTargetAltitudeInput.value = value.firstTargetAltitude.toString();
+			firstDistanceInput.value = value.firstDistance.toString();
+
+			secondOwnAltitudeInput.value = value.secondOwnAltitude.toString();
+			secondTargetAltitudeInput.value = value.secondTargetAltitude.toString();
+			secondDistanceInput.value = value.secondDistance.toString();
+		});
+	}
+}

src/gui/landing.ts

@@ -0,0 +1,177 @@
+import type { Body } from "../calculations/constants";
+import { extrapolateTrajectory, findCheapestLanding, getOrbitalCoordinates, type OrbitalCoordinates, type ShipParameters } from "../calculations/orbit-calculations";
+import type { ChangingStorageValue } from "../storage";
+import { createDisabledInput, createLabel, getCoordinatesFromParameters, getOrbitFromParameters, type OrbitalParameters } from "./common";
+import { type LandingParameters } from "../calculations/orbit-calculations";
+import { LandingParametersGui } from "./landingparameters";
+import { ShipGui } from "./ship";
+import type { FindBestLandingMessage, LandingProgressMessage } from "./worker";
+
+export class LandingGui {
+	parentDiv: HTMLDivElement;
+
+	currentTime: ChangingStorageValue<number>;
+	body: ChangingStorageValue<Body>;
+	orbitalParameters: ChangingStorageValue<OrbitalParameters>;
+	shipParameters: ChangingStorageValue<ShipParameters>;
+	landingParameters: ChangingStorageValue<LandingParameters>;
+
+	shipGui: ShipGui;
+	landingParametersGui: LandingParametersGui;
+
+	worker: Worker | null = null;
+
+	constructor(currentTime: ChangingStorageValue<number>, body: ChangingStorageValue<Body>, orbitalParameters: ChangingStorageValue<OrbitalParameters>, shipParameters: ChangingStorageValue<ShipParameters>, landingParameters: ChangingStorageValue<LandingParameters>) {
+		this.parentDiv = document.createElement("div");
+
+		this.currentTime = currentTime;
+		this.body = body;
+		this.orbitalParameters = orbitalParameters;
+		this.shipParameters = shipParameters;
+		this.landingParameters = landingParameters;
+
+		this.shipGui = new ShipGui(shipParameters);
+		this.landingParametersGui = new LandingParametersGui(this.landingParameters);
+		
+		let shipHeader = document.createElement("h3");
+		shipHeader.appendChild(document.createTextNode("Ship attributes:"));
+		this.parentDiv.appendChild(shipHeader);
+		this.parentDiv.appendChild(this.shipGui.parentDiv);
+
+		let landingHeader = document.createElement("h3");
+		landingHeader.appendChild(document.createTextNode("Landing parameters"));
+		this.parentDiv.appendChild(landingHeader);
+		this.parentDiv.appendChild(this.landingParametersGui.parentDiv);
+
+		let findLandingButton = document.createElement("button");
+		findLandingButton.appendChild(document.createTextNode("Search for landing"));
+		this.parentDiv.appendChild(findLandingButton);
+
+		let landingSolutionHeader = document.createElement("h3");
+		landingSolutionHeader.appendChild(document.createTextNode("Landing:"));
+		this.parentDiv.appendChild(landingSolutionHeader);
+
+		let searchExplanation = document.createElement("p");
+		this.parentDiv.appendChild(searchExplanation);
+
+		const addToParent = (elements: HTMLElement[]) => {
+			let containerDiv = document.createElement("div");
+			containerDiv.classList.add("orbitalParameter");
+			this.parentDiv.appendChild(containerDiv);
+			elements.forEach(child => containerDiv.appendChild(child));
+		}
+
+		let manoeuvreHeader = document.createElement("h4");
+		manoeuvreHeader.appendChild(document.createTextNode("Manoeuvre:"));
+		this.parentDiv.appendChild(manoeuvreHeader);
+
+		let manoeuvreTimeId = crypto.randomUUID();
+		let manoeuvreTimeLabel = createLabel(manoeuvreTimeId, "Time:");
+		let manoeuvreTimeInput = createDisabledInput(manoeuvreTimeId);
+		addToParent([manoeuvreTimeLabel, manoeuvreTimeInput]);
+
+		let progradeId = crypto.randomUUID();
+		let progradeLabel = createLabel(progradeId, "Prograde delta-v:");
+		let progradeInput = createDisabledInput(progradeId);
+		addToParent([progradeLabel, progradeInput]);
+
+		let normalId = crypto.randomUUID();
+		let normalLabel = createLabel(normalId, "Normal delta-v:");
+		let normalInput = createDisabledInput(normalId);
+		addToParent([normalLabel, normalInput]);
+
+		let radialId = crypto.randomUUID();
+		let radialLabel = createLabel(radialId, "Radial delta-v:");
+		let radialInput = createDisabledInput(radialId);
+		addToParent([radialLabel, radialInput]);
+
+		let totalId = crypto.randomUUID();
+		let totalLabel = createLabel(totalId, "Total delta-v:");
+		let totalInput = createDisabledInput(totalId);
+		addToParent([totalLabel, totalInput]);
+
+		let brakingHeader = document.createElement("h4");
+		brakingHeader.appendChild(document.createTextNode("Braking:"));
+		this.parentDiv.appendChild(brakingHeader);
+
+		let brakingTimeId = crypto.randomUUID();
+		let brakingTimeLabel = createLabel(brakingTimeId, "Time to start braking:");
+		let brakingTimeInput = createDisabledInput(brakingTimeId);
+		addToParent([brakingTimeLabel, brakingTimeInput]);
+
+		let brakingAltitudeId = crypto.randomUUID();
+		let brakingAltitudeLabel = createLabel(brakingAltitudeId, "Altitude to start braking:");
+		let brakingAltitudeInput = createDisabledInput(brakingAltitudeId);
+		addToParent([brakingAltitudeLabel, brakingAltitudeInput]);
+
+		let brakingDeltaVId = crypto.randomUUID();
+		let brakingDeltaVLabel = createLabel(brakingDeltaVId, "Delta-v required:");
+		let brakingDeltaVInput = createDisabledInput(brakingDeltaVId);
+		addToParent([brakingDeltaVLabel, brakingDeltaVInput]);
+
+		findLandingButton.addEventListener("click", () => {
+			if (this.worker !== null) {
+				this.worker.terminate();
+				this.worker = null;
+				findLandingButton.innerHTML = "Search for landing";
+			} else {
+				findLandingButton.innerHTML = "Cancel search";
+
+				let currentTime = this.currentTime.getCurrentValue();
+				let orbitalParameters = this.orbitalParameters.getCurrentValue();
+				let shipParameters = this.shipParameters.getCurrentValue();
+				let landingParameters = this.landingParameters.getCurrentValue();
+				let body = this.body.getCurrentValue();
+
+				let coordinates: OrbitalCoordinates | null = getCoordinatesFromParameters(orbitalParameters, body);
+
+				let startTime = Math.max(currentTime, orbitalParameters.currentTimeAtReading);
+				if (startTime > orbitalParameters.currentTimeAtReading) {
+					let addedTime = startTime - orbitalParameters.currentTimeAtReading;
+					coordinates = extrapolateTrajectory(addedTime, coordinates, body);
+				}
+
+				if (coordinates) {
+					this.worker = new Worker(new URL('./worker.ts', import.meta.url), {type: 'module'});
+
+					this.worker.addEventListener("message", e => {
+						let landingResponse = e.data as LandingProgressMessage;
+						if (landingResponse) {
+							searchExplanation.innerHTML = `Search is ${landingResponse.percentDone}% finished`;
+							if (landingResponse.bestDeltaV != null && landingResponse.bestLanding != null) {
+								searchExplanation.appendChild(document.createElement("br"));
+								searchExplanation.appendChild(document.createTextNode(`Current best landing costs ${landingResponse.bestDeltaV.toFixed(3)} m/s`));
+
+								manoeuvreTimeInput.value = landingResponse.bestLanding.transferManoeuvre.time.toFixed(0);
+								progradeInput.value = landingResponse.bestLanding.transferManoeuvre.progradeDeltaV.toFixed(3);
+								normalInput.value = landingResponse.bestLanding.transferManoeuvre.normalDeltaV.toFixed(3);
+								radialInput.value = landingResponse.bestLanding.transferManoeuvre.radialDeltaV.toFixed(3);
+								totalInput.value = landingResponse.bestLanding.transferManoeuvre.totalDeltaV.toFixed(3);
+
+								brakingTimeInput.value = landingResponse.bestLanding.brakingTimestamp.toFixed(0);
+								brakingAltitudeInput.value = landingResponse.bestLanding.brakingAltitude.toFixed(0);
+								brakingDeltaVInput.value = landingResponse.bestLanding.brakingDeltaV.toFixed(3);
+							};
+
+							if (landingResponse.finished) {
+								this.worker?.terminate();
+								this.worker = null;
+								findLandingButton.innerHTML = "Search for landing";
+							}
+						}
+					});
+
+					let message: FindBestLandingMessage = {
+						type: "FindBestLandingMessage",
+						startingCoordinates: coordinates,
+						startTime: startTime,
+						shipParameters: shipParameters,
+						landingParameters: landingParameters,
+						body: body
+					};
+					this.worker.postMessage(message);
+				}
+			}
+		});
+	}
+}

src/gui/landingparameters.ts

@@ -0,0 +1,71 @@
+import type { ChangingStorageValue } from "../storage";
+import { createLabel, createNumberInput } from "./common";
+import { type LandingParameters } from "../calculations/orbit-calculations";
+
+export class LandingParametersGui {
+	parentDiv: HTMLElement;
+
+	landingParameters: ChangingStorageValue<LandingParameters>;
+	sourceId: string;
+
+	constructor(landingParameters: ChangingStorageValue<LandingParameters>) {
+		this.parentDiv = document.createElement("div");
+		this.landingParameters = landingParameters;
+
+		let addToParent = (elements: HTMLElement[]) => {
+			let containerDiv = document.createElement("div");
+			containerDiv.classList.add("orbitalParameter");
+			this.parentDiv.appendChild(containerDiv);
+
+			elements.forEach(child => containerDiv.appendChild(child));
+		}
+
+		let targetLatitudeId = crypto.randomUUID();
+		let targetLatitudeLabel = createLabel(targetLatitudeId, "Target latitude:");
+		let targetLatitudeInput = createNumberInput(targetLatitudeId, -90, 90);
+		addToParent([targetLatitudeLabel, targetLatitudeInput]);
+
+		let targetLongitudeId = crypto.randomUUID();
+		let targetLongitudeLabel = createLabel(targetLongitudeId, "Target longitude:");
+		let targetLongitudeInput = createNumberInput(targetLongitudeId, -360, 360);
+		addToParent([targetLongitudeLabel, targetLongitudeInput]);
+
+		let targetAltitudeId = crypto.randomUUID();
+		let targetAltitudeLabel = createLabel(targetAltitudeId, "Target altitude:");
+		let targetAltitudeInput = createNumberInput(targetAltitudeId, 0);
+		addToParent([targetAltitudeLabel, targetAltitudeInput]);
+
+		let minimumAngleId = crypto.randomUUID();
+		let minimumAngleLabel = createLabel(minimumAngleId, "Minimum incoming angle:");
+		let minimumAngleInput = createNumberInput(minimumAngleId, 0, 90);
+		addToParent([minimumAngleLabel, minimumAngleInput]);
+
+		this.sourceId = crypto.randomUUID();
+		const onChange = () => {
+			let targetLatitude = parseFloat(targetLatitudeInput.value) * Math.PI / 180.0;
+			let targetLongitude = parseFloat(targetLongitudeInput.value) * Math.PI / 180.0;
+			let targetAltitude = parseFloat(targetAltitudeInput.value);
+			let minimumAngle = parseFloat(minimumAngleInput.value) * Math.PI / 180.0;
+
+			landingParameters.set({
+				targetLatitude: targetLatitude,
+				targetLongitude: targetLongitude,
+				targetAltitude: targetAltitude,
+				minimumAngle: minimumAngle
+			}, this.sourceId);
+		};
+
+		[targetLatitudeInput, targetLongitudeInput, targetAltitudeInput, minimumAngleInput].forEach(child => child.addEventListener("change", onChange));
+
+		landingParameters.listenToValue((source, value) => {
+			if (source == this.sourceId) {
+				return;
+			}
+
+			targetLatitudeInput.value = (value.targetLatitude * 180 / Math.PI).toString();
+			targetLongitudeInput.value = (value.targetLongitude * 180 / Math.PI).toString();
+			targetAltitudeInput.value = value.targetAltitude.toString();
+			minimumAngleInput.value = (value.minimumAngle * 180 / Math.PI).toString();
+		});
+	}
+}

src/gui/ship.ts

@@ -0,0 +1,65 @@
+import type { ShipParameters } from "../calculations/orbit-calculations";
+import type { ChangingStorageValue } from "../storage";
+import { createLabel, createNumberInput } from "./common";
+
+export class ShipGui {
+	parentDiv: HTMLElement;
+
+	shipParameters: ChangingStorageValue<ShipParameters>;
+
+	sourceId: string;
+
+	constructor(shipParameters: ChangingStorageValue<ShipParameters>) {
+		this.parentDiv = document.createElement("div");
+		
+		this.shipParameters = shipParameters;
+
+		let addToParent = (elements: HTMLElement[], parent: HTMLElement) => {
+			let containerDiv = document.createElement("div");
+			containerDiv.classList.add("orbitalParameter");
+
+			elements.forEach(child => containerDiv.appendChild(child));
+			parent.appendChild(containerDiv);
+		}
+
+		let shipMassId = crypto.randomUUID();
+		let shipMassLabel = createLabel(shipMassId, "Mass of ship (kg):")
+		let shipMassInput = createNumberInput(shipMassId, 0);
+		addToParent([shipMassLabel, shipMassInput], this.parentDiv);
+
+		let shipThrustId = crypto.randomUUID();
+		let shipThrustLabel = createLabel(shipThrustId, "Thrust of ship (N):");
+		let shipThrustInput = createNumberInput(shipThrustId, 0);
+		addToParent([shipThrustLabel, shipThrustInput], this.parentDiv);
+
+		let specificImpulseId = crypto.randomUUID();
+		let specificImpulseLabel = createLabel(specificImpulseId, "Specific impulse of ship (m/s):");
+		let specificImpulseInput = createNumberInput(specificImpulseId, 0);
+		addToParent([specificImpulseLabel, specificImpulseInput], this.parentDiv);
+
+		this.sourceId = crypto.randomUUID();
+		const onChange = () => {
+			let shipMass = parseFloat(shipMassInput.value);
+			let shipThrust = parseFloat(shipThrustInput.value);
+			let shipSpecificImpulse = parseFloat(specificImpulseInput.value);
+
+			this.shipParameters.set({
+				mass: shipMass,
+				thrust: shipThrust,
+				specificImpulse: shipSpecificImpulse
+			}, this.sourceId);
+		};
+
+		[shipMassInput, shipThrustInput, specificImpulseInput].forEach(child => child.addEventListener("change", onChange));
+
+		shipParameters.listenToValue((source, value) => {
+			if (source == this.sourceId) {
+				return;
+			}
+
+			shipMassInput.value = value.mass.toString();
+			shipThrustInput.value = value.thrust.toString();
+			specificImpulseInput.value = value.specificImpulse.toString();
+		});
+	}
+}

src/gui/simpleplanechange.ts

@@ -82,6 +82,8 @@ export class SimplePlaneChangeGui {
 			let bestDeltaV = Math.min(planeChange.firstManoeuvre.totalDeltaV, planeChange.secondManoeuvre.totalDeltaV);
 			let bestTransfer: Transfer = {
 				transferOrbit: {semiLatusRectum: 0, eccentricity: 0, coordinateAxes: [[], [], []]},
+				transferOrbitTrueAnomalyAtManoeuvreOne: 0,
+				transferOrbitTrueanomalyAtManoeuvreTwo: 0,
 				firstManoeuvre: planeChange.firstManoeuvre,
 				secondManoeuvre: planeChange.secondManoeuvre,
 				closestPointDistance: 0,

src/gui/targetorbit.ts

@@ -79,8 +79,8 @@ export class TargetOrbitGui {
 							}
 
 							if (transferResponse.bestTransfer) {
-								transferResponse.bestTransfer.firstManoeuvre.time += currentTime;
+								transferResponse.bestTransfer.firstManoeuvre.time += startingTime;
-								transferResponse.bestTransfer.secondManoeuvre.time += currentTime;
+								transferResponse.bestTransfer.secondManoeuvre.time += startingTime;
 							}
 
 							this.manoeuvresGui.displayProgress(transferResponse);

src/gui/worker.ts

@@ -1,5 +1,6 @@
 import type { Body } from "../calculations/constants";
-import { findCheapestIntercept, findCheapestTransfer, type Orbit, type OrbitalCoordinates, type Transfer } from "../calculations/orbit-calculations";
+import { findCheapestIntercept, findCheapestLanding, findCheapestTransfer, type Orbit, type OrbitalCoordinates, type ShipParameters, type Transfer } from "../calculations/orbit-calculations";
+import type { Landing, LandingParameters, LandingProgressCallbackFunction, Manoeuvre } from "../calculations/orbit-calculations";
 
 const ctx: Worker = self as any;
 
@@ -18,6 +19,15 @@ export interface FindBestInterceptMessage {
 	body: Body;
 }
 
+export interface FindBestLandingMessage {
+	"type": "FindBestLandingMessage",
+	startTime: number,
+	startingCoordinates: OrbitalCoordinates,
+	shipParameters: ShipParameters,
+	landingParameters: LandingParameters,
+	body: Body
+}
+
 export interface ProgressMessage {
 	type: "ProgressMessage"
 	finished: boolean,
@@ -26,6 +36,14 @@ export interface ProgressMessage {
 	bestTransfer: Transfer | null
 }
 
+export interface LandingProgressMessage {
+	type: "LandingProgressMessage",
+	finished: boolean,
+	percentDone: number,
+	bestDeltaV: number | null,
+	bestLanding: Landing | null
+}
+
 ctx.addEventListener("message", event => {
 	const progressCallback = (numberChecked: number, totalNumber: number, bestDeltaV: number | null, bestTransfer: Transfer | null) => {
 		if (numberChecked % 100 == 0) {
@@ -42,9 +60,23 @@ ctx.addEventListener("message", event => {
 		}
 	};
 
-	let message = event.data as FindBestTransferMessage | FindBestInterceptMessage;
+	const landingProgressCallback: LandingProgressCallbackFunction = (pathsChecked: number, totalNumberOfPaths: number, currentBestDeltaV: number | null, currentBestLanding: Landing | null) => {
+		if (pathsChecked % 100 == 0) {
+			let percentDone = pathsChecked * 100 / totalNumberOfPaths;
+			let message: LandingProgressMessage = {
+				type: "LandingProgressMessage",
+				finished: false,
+				percentDone: percentDone,
+				bestDeltaV: currentBestDeltaV,
+				bestLanding: currentBestLanding
+			};
+
+			ctx.postMessage(message);
+		}
+	}
+
+	let message = event.data as FindBestTransferMessage | FindBestInterceptMessage | FindBestLandingMessage;
 	if (message.type == "FindBestTransfer") {
-		console.log("Finding best transfer");
 		let bestTransfer = findCheapestTransfer(message.startingSituation, message.targetOrbit, message.body, progressCallback);
 		let bestDeltaV = null;
 		if (bestTransfer) {
@@ -62,7 +94,6 @@ ctx.addEventListener("message", event => {
 	}
 
 	if (message.type == "FindBestIntercept") {
-		console.log("Finding best intercept");
 		let bestIntercept = findCheapestIntercept(message.startingSituation, message.targetSituation, message.body, message.additionalTrueAnomaly, progressCallback);
 		let bestDeltaV = null;
 		if (bestIntercept) {
@@ -79,4 +110,17 @@ ctx.addEventListener("message", event => {
 
 		ctx.postMessage(finishedMessage);
 	}
+
+	if (message.type == "FindBestLandingMessage") {
+		let bestLanding = findCheapestLanding(message.startingCoordinates, message.startTime, message.shipParameters, message.landingParameters, message.body, landingProgressCallback);
+		let finishedMessage: LandingProgressMessage = {
+			type: "LandingProgressMessage",
+			finished: true,
+			percentDone: 100,
+			bestDeltaV: bestLanding?.totalDeltaV ?? null,
+			bestLanding: bestLanding
+		};
+
+		ctx.postMessage(finishedMessage);
+	}
 });

src/main.ts

@@ -1,6 +1,9 @@
 import { getPlanetByName, Kerbol } from "./calculations/constants";
-import { createLabel, createRadioButton, decodeOrbitalParameters, DefaultOrbitalParameters, encodeOrbitalParameters } from "./gui/common";
+import { DefaultShipParameters } from "./calculations/orbit-calculations";
-import { InterceptTargetGui } from "./gui/intercept";
+import { createLabel, createRadioButton, DefaultLandingParameters, DefaultOrbitalParameters, encodeJsonObject, getDecoderFunction } from "./gui/common";
+import { decodeTargetOrbitChoice, InterceptTargetGui } from "./gui/intercept";
+import { DefaultInterpolationParameters } from "./gui/interpolate";
+import { LandingGui } from "./gui/landing";
 import { OrbitalParametersGui } from "./gui/orbit";
 import { PlanetGui } from "./gui/planet";
 import { SimplePlaneChangeGui } from "./gui/simpleplanechange";
@@ -8,7 +11,7 @@ import { TargetOrbitGui } from "./gui/targetorbit";
 import { TimeGui } from "./gui/time";
 import { ChangingStorageValue } from "./storage";
 
-type CalculationType = "planeChange" | "targetOrbit" | "intercept";
+type CalculationType = "planeChange" | "targetOrbit" | "intercept" | "landing";
 function decodeCalculationType(input: string): CalculationType {
 	let calculationType = input as CalculationType;
 	if (calculationType !== undefined) {
@@ -20,11 +23,15 @@ function decodeCalculationType(input: string): CalculationType {
 
 let currentTime = new ChangingStorageValue(0, "currentTime", parseInt, n => n.toString());
 let body = new ChangingStorageValue(Kerbol, "planet", s => getPlanetByName(s), p => p.planetName);
-let orbitalParameters = new ChangingStorageValue(DefaultOrbitalParameters, "orbitalParameters", decodeOrbitalParameters, encodeOrbitalParameters);
+let orbitalParameters = new ChangingStorageValue(DefaultOrbitalParameters, "orbitalParameters", getDecoderFunction(DefaultOrbitalParameters), encodeJsonObject);
 let calculationType = new ChangingStorageValue("planeChange", "calculationType", decodeCalculationType, s => s);
-let targetOrbitalParameters = new ChangingStorageValue(DefaultOrbitalParameters, "targetOrbitalParameters", decodeOrbitalParameters, encodeOrbitalParameters);
+let targetOrbitalParameters = new ChangingStorageValue(DefaultOrbitalParameters, "targetOrbitalParameters", getDecoderFunction(DefaultOrbitalParameters), encodeJsonObject);
 let circularizeOrbit = new ChangingStorageValue(false, "circularizeOrbit", s => s == "true", b => b ? "true" : "false");
+let targetOrbitChoice = new ChangingStorageValue("KnownOrbit", "targetOrbitChoice", decodeTargetOrbitChoice, s => s);
+let interpolationParameters = new ChangingStorageValue(DefaultInterpolationParameters, "InterpolationParameters", getDecoderFunction(DefaultInterpolationParameters), encodeJsonObject);
 let additionalInterceptTrueanomaly = new ChangingStorageValue(0, "additionalTrueAnomaly", parseFloat, s => s.toString());
+let shipParameters = new ChangingStorageValue(DefaultShipParameters, "shipParameters", getDecoderFunction(DefaultShipParameters), encodeJsonObject);
+let landingParameters = new ChangingStorageValue(DefaultLandingParameters, "landingParameters", getDecoderFunction(DefaultLandingParameters), encodeJsonObject);
 
 let dateGui = new TimeGui(currentTime, true);
 let currentTimeDiv = document.getElementById("currentTimeDiv");
@@ -40,7 +47,8 @@ orbitalParametersDiv?.appendChild(orbitalParametersGui.parentDiv);
 
 let simplePlaneChangeGui = new SimplePlaneChangeGui(currentTime, body, orbitalParameters, targetOrbitalParameters, circularizeOrbit);
 let targetOrbitGui = new TargetOrbitGui(currentTime, body, orbitalParameters, targetOrbitalParameters);
-let interceptTargetGui = new InterceptTargetGui(currentTime, body, orbitalParameters, targetOrbitalParameters, additionalInterceptTrueanomaly);
+let interceptTargetGui = new InterceptTargetGui(currentTime, body, orbitalParameters, targetOrbitalParameters, additionalInterceptTrueanomaly, targetOrbitChoice, interpolationParameters);
+let landingGui = new LandingGui(currentTime, body, orbitalParameters, shipParameters, landingParameters);
 
 let calculationChoiceDiv = document.getElementById("calculationChoice");
 
@@ -59,6 +67,11 @@ interceptTargetButton.addEventListener("change", () => calculationType.set("inte
 let interceptTargetLabel = createLabel("interceptTarget", "Intercept target");
 [interceptTargetButton, interceptTargetLabel].forEach(child => calculationChoiceDiv?.appendChild(child));
 
+let landingButton = createRadioButton("calculationChoice", "landing");
+landingButton.addEventListener("change", () => calculationType.set("landing", "main"));
+let landingLabel = createLabel("landing", "Landing");
+[landingButton, landingLabel].forEach(child => calculationChoiceDiv?.appendChild(child));
+
 let calculationsDiv = document.getElementById("calculation") as HTMLDivElement;
 calculationType.listenToValue((_, value) => {
 	calculationsDiv.innerHTML = "";
@@ -71,6 +84,9 @@ calculationType.listenToValue((_, value) => {
 	} else if (value == "intercept") {
 		interceptTargetButton.setAttribute("checked", "");
 		calculationsDiv.appendChild(interceptTargetGui.parentDiv);
+	} else if (value == "landing") {
+		landingButton.setAttribute("checked", "");
+		calculationsDiv.appendChild(landingGui.parentDiv);
 	}
 });