Moved all of the vessel parsing code into the new RelayDatabase, which
Moved all of the vessel parsing code into the new RelayDatabase, which
watches some events to dirty the cache when states change. Also modules
will no longer offer to transmit if their part is dead or deactivated.

file:b/ARTools.cs (new)
--- /dev/null
+++ b/ARTools.cs
@@ -1,1 +1,130 @@
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
 
+using System;
+
+namespace AntennaRange
+{
+	public static class Tools
+	{
+		private static ScreenMessage debugmsg = new ScreenMessage("", 2f, ScreenMessageStyle.UPPER_RIGHT);
+		// Function that posts messages to the screen and the log when DEBUG is defined.
+		[System.Diagnostics.Conditional("DEBUG")]
+		public static void PostDebugMessage(string Msg)
+		{
+			if (HighLogic.LoadedScene > GameScenes.SPACECENTER)
+			{
+				debugmsg.message = Msg;
+				ScreenMessages.PostScreenMessage(debugmsg, true);
+			}
+
+			KSPLog.print(Msg);
+		}
+
+		/*
+		 * MuMech_ToSI is a part of the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
+		 * */
+		public static string MuMech_ToSI(double d, int digits = 3, int MinMagnitude = 0, int MaxMagnitude = int.MaxValue)
+		{
+			float exponent = (float)Math.Log10(Math.Abs(d));
+			exponent = UnityEngine.Mathf.Clamp(exponent, (float)MinMagnitude, (float)MaxMagnitude);
+
+			if (exponent >= 0)
+			{
+				switch ((int)Math.Floor(exponent))
+				{
+					case 0:
+						case 1:
+						case 2:
+						return d.ToString("F" + digits);
+						case 3:
+						case 4:
+						case 5:
+						return (d / 1e3).ToString("F" + digits) + "k";
+						case 6:
+						case 7:
+						case 8:
+						return (d / 1e6).ToString("F" + digits) + "M";
+						case 9:
+						case 10:
+						case 11:
+						return (d / 1e9).ToString("F" + digits) + "G";
+						case 12:
+						case 13:
+						case 14:
+						return (d / 1e12).ToString("F" + digits) + "T";
+						case 15:
+						case 16:
+						case 17:
+						return (d / 1e15).ToString("F" + digits) + "P";
+						case 18:
+						case 19:
+						case 20:
+						return (d / 1e18).ToString("F" + digits) + "E";
+						case 21:
+						case 22:
+						case 23:
+						return (d / 1e21).ToString("F" + digits) + "Z";
+						default:
+						return (d / 1e24).ToString("F" + digits) + "Y";
+				}
+			}
+			else if (exponent < 0)
+			{
+				switch ((int)Math.Floor(exponent))
+				{
+					case -1:
+						case -2:
+						case -3:
+						return (d * 1e3).ToString("F" + digits) + "m";
+						case -4:
+						case -5:
+						case -6:
+						return (d * 1e6).ToString("F" + digits) + "μ";
+						case -7:
+						case -8:
+						case -9:
+						return (d * 1e9).ToString("F" + digits) + "n";
+						case -10:
+						case -11:
+						case -12:
+						return (d * 1e12).ToString("F" + digits) + "p";
+						case -13:
+						case -14:
+						case -15:
+						return (d * 1e15).ToString("F" + digits) + "f";
+						case -16:
+						case -17:
+						case -18:
+						return (d * 1e18).ToString("F" + digits) + "a";
+						case -19:
+						case -20:
+						case -21:
+						return (d * 1e21).ToString("F" + digits) + "z";
+						default:
+						return (d * 1e24).ToString("F" + digits) + "y";
+				}
+			}
+			else
+			{
+				return "0";
+			}
+		}
+	}
+}
+
+

--- a/AntennaRange.cfg
+++ b/AntennaRange.cfg
@@ -1,50 +1,50 @@
-//

-// AntennaRange © 2013 toadicus

-// 

-// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a

-// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

-//

-// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike

-// 3.0 Uported License.

-//

-// Specifications:

-// nominalRange:	The distance from Kerbin at which the antenna will perform exactly as prescribed by packetResourceCost

-// 					and packetSize.

-// maxPowerFactor:	The multiplier on packetResourceCost that defines the maximum power output of the antenna.  When the

-//					power cost exceeds packetResourceCost * maxPowerFactor, transmission will fail.

-// maxDataFactor:	The multipler on packetSize that defines the maximum data bandwidth of the antenna.

-// 

-

-@PART[longAntenna]

-{

-	@MODULE[ModuleDataTransmitter]

-	{

-		@name = ModuleLimitedDataTransmitter

-		nominalRange = 1500000

-		maxPowerFactor = 8

-		maxDataFactor = 4

-	}

-}

-

-@PART[mediumDishAntenna]

-{

-	@MODULE[ModuleDataTransmitter]

-	{

-		@name = ModuleLimitedDataTransmitter

-		nominalRange = 30000000

-		maxPowerFactor = 8

-		maxDataFactor = 4

-	}

-}

-

-@PART[commDish]

-{

-	@MODULE[ModuleDataTransmitter]

-	{

-		@name = ModuleLimitedDataTransmitter

-		nominalRange = 80000000000

-		maxPowerFactor = 8

-		maxDataFactor = 4

-	}

-}

+//
+// AntennaRange © 2013 toadicus
+// 
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// Specifications:
+// nominalRange:	The distance from Kerbin at which the antenna will perform exactly as prescribed by packetResourceCost
+// 					and packetSize.
+// maxPowerFactor:	The multiplier on packetResourceCost that defines the maximum power output of the antenna.  When the
+//					power cost exceeds packetResourceCost * maxPowerFactor, transmission will fail.
+// maxDataFactor:	The multipler on packetSize that defines the maximum data bandwidth of the antenna.
+// 
 
+@PART[longAntenna]
+{
+	@MODULE[ModuleDataTransmitter]
+	{
+		@name = ModuleLimitedDataTransmitter
+		nominalRange = 1500000
+		maxPowerFactor = 8
+		maxDataFactor = 4
+	}
+}
+
+@PART[mediumDishAntenna]
+{
+	@MODULE[ModuleDataTransmitter]
+	{
+		@name = ModuleLimitedDataTransmitter
+		nominalRange = 30000000
+		maxPowerFactor = 8
+		maxDataFactor = 4
+	}
+}
+
+@PART[commDish]
+{
+	@MODULE[ModuleDataTransmitter]
+	{
+		@name = ModuleLimitedDataTransmitter
+		nominalRange = 80000000000
+		maxPowerFactor = 8
+		maxDataFactor = 4
+	}
+}
+

file:a/AntennaRange.cs (deleted)
--- a/AntennaRange.cs
+++ /dev/null
@@ -1,256 +1,1 @@
-/*

- * AntennaRange © 2013 toadicus

- * 

- * AntennaRange provides incentive and requirements for the use of the various antenna parts.

- * Nominally, the breakdown is as follows:

- * 

- *     Communotron 16 - Suitable up to Kerbalsynchronous Orbit

- *     Comms DTS-M1 - Suitable throughout the Kerbin subsystem

- *     Communotron 88-88 - Suitable throughout the Kerbol system.

- * 

- * This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a

- * copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/

- * 

- * This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike 3.0 Uported License.

- * 

- */

-

-using System;

-using System.Collections.Generic;

-using KSP;

-

-namespace AntennaRange

-{

-	/*

-	 * ModuleLimitedDataTransmitter is designed as a drop-in replacement for ModuleDataTransmitter, and handles range-

-	 * finding, power scaling, and data scaling for antennas during science transmission.  Its functionality varies with

-	 * three tunables: nominalRange, maxPowerFactor, and maxDataFactor, set in .cfg files.

-	 * 

-	 * In general, the scaling functions assume the following relation:

-	 * 

-	 *     D² α P/R,

-	 * 

-	 * where D is the total transmission distance, P is the transmission power, and R is the data rate.

-	 * 

-	 * */

-	public class ModuleLimitedDataTransmitter : ModuleDataTransmitter, IScienceDataTransmitter

-	{

-		// Stores the packetResourceCost as defined in the .cfg file.

-		protected float _basepacketResourceCost;

-

-		// Stores the packetSize as defined in the .cfg file.

-		protected float _basepacketSize;

-

-		// We don't have a Bard, so we're hiding Kerbin here.

-		protected CelestialBody _Kerbin;

-

-		// Returns the current distance to the center of Kerbin, which is totally where the Kerbals keep their radioes.

-		protected double transmitDistance

-		{

-			get

-			{

-				Vector3d KerbinPos = this._Kerbin.position;

-				Vector3d ActivePos = base.vessel.GetWorldPos3D();

-

-				return (ActivePos - KerbinPos).magnitude;

-			}

-		}

-

-		// Returns the maximum distance this module can transmit

-		public double maxTransmitDistance

-		{

-			get

-			{

-				return Math.Sqrt (this.maxPowerFactor) * this.nominalRange;

-			}

-		}

-

-		// The distance from Kerbin at which the antenna will perform exactly as prescribed by packetResourceCost

-		// and packetSize.

-		[KSPField(isPersistant = false)]

-		public double nominalRange = 1500000d;

-

-		// The multiplier on packetResourceCost that defines the maximum power output of the antenna.  When the power

-		// cost exceeds packetResourceCost * maxPowerFactor, transmission will fail.

-		[KSPField(isPersistant = false)]

-		public float maxPowerFactor = 8f;

-

-		// The multipler on packetSize that defines the maximum data bandwidth of the antenna.

-		[KSPField(isPersistant = false)]

-		public float maxDataFactor = 4f;

-

-		// Build ALL the objects.

-		public ModuleLimitedDataTransmitter () : base() { }

-

-		public override void OnStart (StartState state)

-		{

-			base.OnStart (state);

-

-			if (state >= StartState.PreLaunch && this._Kerbin == null)

-			{

-				// Go fetch Kerbin, because it is tricksy and hides from us.

-				List<CelestialBody> bodies = FlightGlobals.Bodies;

-

-				foreach (CelestialBody body in bodies)

-				{

-					if (body.name == "Kerbin")

-					{

-						this._Kerbin = body;

-						break;

-					}

-				}

-			}

-		}

-

-		public override void OnLoad(ConfigNode node)

-		{

-			base.OnLoad (node);

-			this._basepacketSize = base.packetSize;

-			this._basepacketResourceCost = base.packetResourceCost;

-		}

-

-		// Post an error in the communication messages describing the reason transmission has failed.  Currently there

-		// is only one reason for this.

-		protected void PostCannotTransmitError()

-		{

-			string ErrorText = string.Format (

-				"Unable to transmit: out of range!  Maximum range = {0}; Current range = {1}.",

-				this.maxTransmitDistance,

-				this.transmitDistance);

-			ScreenMessages.PostScreenMessage (new ScreenMessage (ErrorText, 4f, ScreenMessageStyle.UPPER_LEFT));

-		}

-

-		protected void PreTransmit_SetPacketResourceCost()

-		{

-			if (this.transmitDistance <= this.nominalRange)

-			{

-				base.packetResourceCost = this._basepacketResourceCost;

-			}

-			else

-			{

-				base.packetResourceCost = this._basepacketResourceCost

-					* (float)Math.Pow (this.transmitDistance / this.nominalRange, 2);

-			}

-		}

-

-		protected void PreTransmit_SetPacketSize()

-		{

-			if (this.transmitDistance >= this.nominalRange)

-			{

-				base.packetSize = this._basepacketSize;

-			}

-			else

-			{

-				base.packetSize = Math.Min (

-					this._basepacketSize * (float)Math.Pow (this.nominalRange / this.transmitDistance, 2),

-					this._basepacketSize * this.maxDataFactor);

-			}

-		}

-

-		// Override ModuleDataTransmitter.GetInfo to add nominal and maximum range to the VAB description.

-		public override string GetInfo()

-		{

-			string text = base.GetInfo();

-			text += "Nominal Range: " + this.nominalRange.ToString() + "\n";

-			text += "Maximum Range: " + this.maxTransmitDistance.ToString() + "\n";

-			return text;

-		}

-

-		// Override ModuleDataTransmitter.CanTransmit to return false when transmission is not possible.

-		public new bool CanTransmit()

-		{

-			if (this.transmitDistance > this.maxTransmitDistance)

-			{

-				return false;

-			}

-			return true;

-		}

-

-		// Override ModuleDataTransmitter.TransmitData to check against CanTransmit and fail out when CanTransmit

-		// returns false.

-		public new void TransmitData(List<ScienceData> dataQueue)

-		{

-			PreTransmit_SetPacketSize ();

-			PreTransmit_SetPacketResourceCost ();

-

-			Tools.PostDebugMessage (

-				"distance: " + this.transmitDistance

-				+ " packetSize: " + this.packetSize

-				+ " packetResourceCost: " + this.packetResourceCost

-			);

-			if (this.CanTransmit())

-			{

-				base.TransmitData(dataQueue);

-			}

-			else

-			{

-				this.PostCannotTransmitError ();

-			}

-		}

-

-		// Override ModuleDataTransmitter.StartTransmission to check against CanTransmit and fail out when CanTransmit

-		// returns false.

-		public new void StartTransmission()

-		{

-			PreTransmit_SetPacketSize ();

-			PreTransmit_SetPacketResourceCost ();

-

-			Tools.PostDebugMessage (

-				"distance: " + this.transmitDistance

-				+ " packetSize: " + this.packetSize

-				+ " packetResourceCost: " + this.packetResourceCost

-				);

-			if (this.CanTransmit())

-			{

-				base.StartTransmission();

-			}

-			else

-			{

-				this.PostCannotTransmitError ();

-			}

-		}

-

-		#if DEBUG

-		[KSPEvent (guiName = "Show Debug Info", active = true, guiActive = true)]

-		public void DebugInfo()

-		{

-			PreTransmit_SetPacketSize ();

-			PreTransmit_SetPacketResourceCost ();

-

-			string msg = string.Format(

-				"'{0}'\n" + 

-				"_basepacketSize: {1}\n" +

-				"packetSize: {2}\n" +

-				"_basepacketResourceCost: {3}\n" +

-				"packetResourceCost: {4}\n" +

-				"maxTransmitDistance: {5}\n" +

-				"transmitDistance: {6}\n" +

-				"nominalRange: {7}\n" +

-				"CanTransmit: {8}",

-				this.name,

-				this._basepacketSize,

-				base.packetSize,

-				this._basepacketResourceCost,

-				base.packetResourceCost,

-				this.maxTransmitDistance,

-				this.transmitDistance,

-				this.nominalRange,

-				this.CanTransmit()

-				);

-			ScreenMessages.PostScreenMessage (new ScreenMessage (msg, 30f, ScreenMessageStyle.UPPER_RIGHT));

-		}

-		#endif

-	}

-

-	public static class Tools

-	{

-		[System.Diagnostics.Conditional("DEBUG")]

-		public static void PostDebugMessage(string Str)

-		{

-			ScreenMessage Message = new ScreenMessage (Str, 4f, ScreenMessageStyle.UPPER_RIGHT);

-			ScreenMessages.PostScreenMessage (Message);

-		}

-	}

-}

-

 

file:b/AntennaRelay.cs (new)
--- /dev/null
+++ b/AntennaRelay.cs
@@ -1,1 +1,268 @@
-
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace AntennaRange
+{
+	public class AntennaRelay : IAntennaRelay
+	{
+		// We don't have a Bard, so we'll hide Kerbin here.
+		protected CelestialBody Kerbin;
+
+		protected System.Diagnostics.Stopwatch searchTimer;
+		protected long millisecondsBetweenSearches;
+
+		/// <summary>
+		/// Gets the parent Vessel.
+		/// </summary>
+		/// <value>The parent Vessel.</value>
+		public Vessel vessel
+		{
+			get;
+			protected set;
+		}
+
+		/// <summary>
+		/// Gets or sets the nearest relay.
+		/// </summary>
+		/// <value>The nearest relay</value>
+		public IAntennaRelay nearestRelay
+		{
+			get;
+			protected set;
+		}
+
+		/// <summary>
+		/// Gets the transmit distance.
+		/// </summary>
+		/// <value>The transmit distance.</value>
+		public double transmitDistance
+		{
+			get
+			{
+				this.nearestRelay = this.FindNearestRelay();
+
+				// If there is no available relay nearby...
+				if (nearestRelay == null)
+				{
+					// .. return the distance to Kerbin
+					return this.DistanceTo(this.Kerbin);
+				}
+				else
+				{
+					/// ...otherwise, return the distance to the nearest available relay.
+					return this.DistanceTo(nearestRelay);
+				}
+			}
+		}
+
+		/// <summary>
+		/// The maximum distance at which this relay can operate.
+		/// </summary>
+		/// <value>The max transmit distance.</value>
+		public virtual float maxTransmitDistance
+		{
+			get;
+			set;
+		}
+
+		/// <summary>
+		/// Gets a value indicating whether this <see cref="AntennaRange.ProtoDataTransmitter"/> has been checked during
+		/// the current relay attempt.
+		/// </summary>
+		/// <value><c>true</c> if relay checked; otherwise, <c>false</c>.</value>
+		public virtual bool relayChecked
+		{
+			get;
+			protected set;
+		}
+
+		/// <summary>
+		/// Determines whether this instance can transmit.
+		/// </summary>
+		/// <returns><c>true</c> if this instance can transmit; otherwise, <c>false</c>.</returns>
+		public virtual bool CanTransmit()
+		{
+			if (this.transmitDistance > this.maxTransmitDistance)
+			{
+				return false;
+			}
+			else
+			{
+				return true;
+			}
+		}
+
+		/// <summary>
+		/// Finds the nearest relay.
+		/// </summary>
+		/// <returns>The nearest relay or null, if no relays in range.</returns>
+		public IAntennaRelay FindNearestRelay()
+		{
+			if (this.searchTimer.IsRunning && this.searchTimer.ElapsedMilliseconds < this.millisecondsBetweenSearches)
+			{
+				return this.nearestRelay;
+			}
+
+			if (this.searchTimer.IsRunning)
+			{
+				this.searchTimer.Stop();
+				this.searchTimer.Reset();
+			}
+
+			this.searchTimer.Start();
+
+			// Set this relay as checked, so that we don't check it again.
+			this.relayChecked = true;
+
+			// Get a list of vessels within transmission range.
+			List<Vessel> nearbyVessels = FlightGlobals.Vessels
+				.Where(v => (v.GetWorldPos3D() - vessel.GetWorldPos3D()).magnitude < this.maxTransmitDistance)
+					.ToList();
+
+			nearbyVessels.RemoveAll(v => v.vesselType == VesselType.Debris);
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Non-debris vessels in range: {1}",
+				this.GetType().Name,
+				nearbyVessels.Count
+				));
+
+			// Remove this vessel.
+			nearbyVessels.RemoveAll(v => v.id == vessel.id);
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Vessels in range excluding self: {1}",
+				this.GetType().Name,
+				nearbyVessels.Count
+				));
+
+			// Get a flattened list of all IAntennaRelay modules and protomodules in transmission range.
+			List<IAntennaRelay> nearbyRelays = nearbyVessels.SelectMany(v => v.GetAntennaRelays()).ToList();
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Found {1} nearby relays.",
+				this.GetType().Name,
+				nearbyRelays.Count
+				));
+
+			// Remove all relays already checked this time.
+			nearbyRelays.RemoveAll(r => r.relayChecked);
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Found {1} nearby relays not already checked.",
+				this.GetType().Name,
+				nearbyRelays.Count
+				));
+
+			// Remove all relays that cannot transmit.
+			// This call to r.CanTransmit() starts a depth-first recursive search for relays with a path back to Kerbin.
+			nearbyRelays.RemoveAll(r => !r.CanTransmit());
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Found {1} nearby relays not already checked that can transmit.",
+				this.GetType().Name,
+				nearbyRelays.Count
+				));
+
+			// Sort the available relays by distance.
+			nearbyRelays.Sort(new RelayComparer(this.vessel));
+
+			// Get the nearest available relay, or null if there are no available relays nearby.
+			IAntennaRelay _nearestRelay = nearbyRelays.FirstOrDefault();
+
+			// If we have a nearby relay...
+			if (_nearestRelay != null)
+			{
+				// ...but that relay is farther than Kerbin...
+				if (this.DistanceTo(_nearestRelay) > this.DistanceTo(Kerbin))
+				{
+					// ...just use Kerbin.
+					_nearestRelay = null;
+				}
+			}
+
+			// Now that we're done with our recursive CanTransmit checks, flag this relay as not checked so it can be
+			// used next time.
+			this.relayChecked = false;
+
+			// Return the nearest available relay, or null if there are no available relays nearby.
+			return _nearestRelay;
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="AntennaRange.ProtoDataTransmitter"/> class.
+		/// </summary>
+		/// <param name="ms"><see cref="ProtoPartModuleSnapshot"/></param>
+		public AntennaRelay(Vessel v)
+		{
+			this.vessel = v;
+
+			this.searchTimer = new System.Diagnostics.Stopwatch();
+			this.millisecondsBetweenSearches = 5000;
+
+			// HACK: This might not be safe in all circumstances, but since AntennaRelays are not built until Start,
+			// we hope it is safe enough.
+			this.Kerbin = FlightGlobals.Bodies.FirstOrDefault(b => b.name == "Kerbin");
+		}
+
+		/*
+		 * Class implementing IComparer<IAntennaRelay> for use in sorting relays by distance.
+		 * */
+		internal class RelayComparer : IComparer<IAntennaRelay>
+		{
+			/// <summary>
+			/// The reference Vessel (usually the active vessel).
+			/// </summary>
+			protected Vessel referenceVessel;
+
+			// We don't want no stinking public parameterless constructors.
+			private RelayComparer() {}
+
+			/// <summary>
+			/// Initializes a new instance of the <see cref="AntennaRange.AntennaRelay+RelayComparer"/> class for use
+			/// in sorting relays by distance.
+			/// </summary>
+			/// <param name="reference">The reference Vessel</param>
+			public RelayComparer(Vessel reference)
+			{
+				this.referenceVessel = reference;
+			}
+
+			/// <summary>
+			/// Compare the <see cref="IAntennaRelay"/>s "one" and "two".
+			/// </summary>
+			/// <param name="one">The first IAntennaRelay in the comparison</param>
+			/// <param name="two">The second IAntennaRelay in the comparison</param>
+			public int Compare(IAntennaRelay one, IAntennaRelay two)
+			{
+				double distanceOne;
+				double distanceTwo;
+
+				distanceOne = one.vessel.DistanceTo(referenceVessel);
+				distanceTwo = two.vessel.DistanceTo(referenceVessel);
+
+				return distanceOne.CompareTo(distanceTwo);
+			}
+		}
+	}
+}
+
+

file:b/Extensions.cs (new)
--- /dev/null
+++ b/Extensions.cs
@@ -1,1 +1,92 @@
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
 
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace AntennaRange
+{
+	/*
+	 * A class of utility extensions for Vessels and Relays to help find a relay path back to Kerbin.
+	 * */
+	public static class Extensions
+	{
+		/// <summary>
+		/// Returns the distance between this Vessel and another Vessel.
+		/// </summary>
+		/// <param name="vesselOne">This <see cref="Vessel"/><see ></param>
+		/// <param name="vesselTwo">Another <see cref="Vessel"/></param>
+		public static double DistanceTo(this Vessel vesselOne, Vessel vesselTwo)
+		{
+			return (vesselOne.GetWorldPos3D() - vesselTwo.GetWorldPos3D()).magnitude;
+		}
+
+		/// <summary>
+		/// Returns the distance between this Vessel and a CelestialBody
+		/// </summary>
+		/// <param name="vessel">This Vessel</param>
+		/// <param name="body">A <see cref="CelestialBody"/></param>
+		public static double DistanceTo(this Vessel vessel, CelestialBody body)
+		{
+			return (vessel.GetWorldPos3D() - body.position).magnitude;
+		}
+
+		/// <summary>
+		/// Returns the distance between this IAntennaRelay and a Vessel
+		/// </summary>
+		/// <param name="relay">This <see cref="IAntennaRelay"/></param>
+		/// <param name="Vessel">A <see cref="Vessel"/></param>
+		public static double DistanceTo(this AntennaRelay relay, Vessel Vessel)
+		{
+			return relay.vessel.DistanceTo(Vessel);
+		}
+
+		/// <summary>
+		/// Returns the distance between this IAntennaRelay and a CelestialBody
+		/// </summary>
+		/// <param name="relay">This <see cref="IAntennaRelay"/></param>
+		/// <param name="body">A <see cref="CelestialBody"/></param>
+		public static double DistanceTo(this AntennaRelay relay, CelestialBody body)
+		{
+			return relay.vessel.DistanceTo(body);
+		}
+
+		/// <summary>
+		/// Returns the distance between this IAntennaRelay and another IAntennaRelay
+		/// </summary>
+		/// <param name="relayOne">This <see cref="IAntennaRelay"/></param>
+		/// <param name="relayTwo">Another <see cref="IAntennaRelay"/></param>
+		public static double DistanceTo(this AntennaRelay relayOne, IAntennaRelay relayTwo)
+		{
+			return relayOne.DistanceTo(relayTwo.vessel);
+		}
+
+		/// <summary>
+		/// Returns all of the PartModules or ProtoPartModuleSnapshots implementing IAntennaRelay in this Vessel.
+		/// </summary>
+		/// <param name="vessel">This <see cref="Vessel"/></param>
+		public static IEnumerable<IAntennaRelay> GetAntennaRelays (this Vessel vessel)
+		{
+			return RelayDatabase.Instance[vessel].Values.ToList();
+		}
+
+
+	}
+}
+
+

file:b/IAntennaRelay.cs (new)
--- /dev/null
+++ b/IAntennaRelay.cs
@@ -1,1 +1,61 @@
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
 
+using KSP;
+using System;
+
+namespace AntennaRange
+{
+	/*
+	 * Interface defining the basic functionality of AntennaRelay modules for AntennaRange.
+	 * */
+	public interface IAntennaRelay
+	{
+		/// <summary>
+		/// Gets the parent Vessel.
+		/// </summary>
+		/// <value>The parent Vessel.</value>
+		Vessel vessel { get; }
+
+		/// <summary>
+		/// Gets the distance to the nearest relay or Kerbin, whichever is closer.
+		/// </summary>
+		/// <value>The distance to the nearest relay or Kerbin, whichever is closer.</value>
+		double transmitDistance { get; }
+
+		/// <summary>
+		/// The maximum distance at which this relay can operate.
+		/// </summary>
+		/// <value>The max transmit distance.</value>
+		float maxTransmitDistance { get; }
+
+		/// <summary>
+		/// Gets a value indicating whether this <see cref="AntennaRange.ProtoDataTransmitter"/> has been checked during
+		/// the current relay attempt.
+		/// </summary>
+		/// <value><c>true</c> if relay checked; otherwise, <c>false</c>.</value>
+		bool relayChecked { get; }
+
+		/// <summary>
+		/// Determines whether this instance can transmit.
+		/// </summary>
+		/// <returns><c>true</c> if this instance can transmit; otherwise, <c>false</c>.</returns>
+		bool CanTransmit();
+	}
+}
+
+

--- /dev/null
+++ b/ModuleLimitedDataTransmitter.cs
@@ -1,1 +1,467 @@
-
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using KSP;
+using UnityEngine;
+
+namespace AntennaRange
+{
+	/*
+	 * ModuleLimitedDataTransmitter is designed as a drop-in replacement for ModuleDataTransmitter, and handles range-
+	 * finding, power scaling, and data scaling for antennas during science transmission.  Its functionality varies with
+	 * three tunables: nominalRange, maxPowerFactor, and maxDataFactor, set in .cfg files.
+	 * 
+	 * In general, the scaling functions assume the following relation:
+	 * 
+	 *     D² α P/R,
+	 * 
+	 * where D is the total transmission distance, P is the transmission power, and R is the data rate.
+	 * 
+	 * */
+
+	/*
+	 * Fields
+	 * */
+	public class ModuleLimitedDataTransmitter : ModuleDataTransmitter, IScienceDataTransmitter, IAntennaRelay
+	{
+		// Stores the packetResourceCost as defined in the .cfg file.
+		protected float _basepacketResourceCost;
+
+		// Stores the packetSize as defined in the .cfg file.
+		protected float _basepacketSize;
+
+		// Every antenna is a relay.
+		protected AntennaRelay relay;
+
+		// Keep track of vessels with transmitters for relay purposes.
+		protected List<Vessel> _relayVessels;
+
+		// Sometimes we will need to communicate errors; this is how we do it.
+		protected ScreenMessage ErrorMsg;
+
+		// The distance from Kerbin at which the antenna will perform exactly as prescribed by packetResourceCost
+		// and packetSize.
+		[KSPField(isPersistant = false)]
+		public float nominalRange;
+
+		[KSPField(isPersistant = false, guiActive = true, guiName = "Transmission Distance")]
+		public string UItransmitDistance;
+
+		[KSPField(isPersistant = false, guiActive = true, guiName = "Maximum Distance")]
+		public string UImaxTransmitDistance;
+
+		[KSPField(isPersistant = false, guiActive = true, guiName = "Packet Size")]
+		public string UIpacketSize;
+
+		[KSPField(isPersistant = false, guiActive = true, guiName = "Packet Cost")]
+		public string UIpacketCost;
+
+		// The multiplier on packetResourceCost that defines the maximum power output of the antenna.  When the power
+		// cost exceeds packetResourceCost * maxPowerFactor, transmission will fail.
+		[KSPField(isPersistant = false)]
+		public float maxPowerFactor;
+
+		// The multipler on packetSize that defines the maximum data bandwidth of the antenna.
+		[KSPField(isPersistant = false)]
+		public float maxDataFactor;
+
+		protected bool actionUIUpdate;
+
+		/*
+		 * Properties
+		 * */
+		// Returns the parent vessel housing this antenna.
+		public new Vessel vessel
+		{
+			get
+			{
+				return base.vessel;
+			}
+		}
+
+		// Returns the distance to the nearest relay or Kerbin, whichever is closer.
+		public double transmitDistance
+		{
+			get
+			{
+				return this.relay.transmitDistance;
+			}
+		}
+
+		// Returns the maximum distance this module can transmit
+		public float maxTransmitDistance
+		{
+			get
+			{
+				return Mathf.Sqrt (this.maxPowerFactor) * this.nominalRange;
+			}
+		}
+
+		/*
+		 * The next two functions overwrite the behavior of the stock functions and do not perform equivalently, except
+		 * in that they both return floats.  Here's some quick justification:
+		 * 
+		 * The stock implementation of GetTransmitterScore (which I cannot override) is:
+		 * 		Score = (1 + DataResourceCost) / DataRate
+		 * 
+		 * The stock DataRate and DataResourceCost are:
+		 * 		DataRate = packetSize / packetInterval
+		 * 		DataResourceCost = packetResourceCost / packetSize
+		 * 
+		 * So, the resulting score is essentially in terms of joules per byte per baud.  Rearranging that a bit, it
+		 * could also look like joule-seconds per byte per byte, or newton-meter-seconds per byte per byte.  Either way,
+		 * that metric is not a very reasonable one.
+		 * 
+		 * Two metrics that might make more sense are joules per byte or joules per byte per second.  The latter case
+		 * would look like:
+		 * 		DataRate = packetSize / packetInterval
+		 * 		DataResourceCost = packetResourceCost
+		 * 
+		 * The former case, which I've chosen to implement below, is:
+		 * 		DataRate = packetSize
+		 * 		DataResourceCost = packetResourceCost
+		 * 
+		 * So... hopefully that doesn't screw with anything else.
+		 * */
+		// Override ModuleDataTransmitter.DataRate to just return packetSize, because we want antennas to be scored in
+		// terms of joules/byte
+		public new float DataRate
+		{
+			get
+			{
+				this.PreTransmit_SetPacketSize();
+
+				if (this.CanTransmit())
+				{
+					return this.packetSize;
+				}
+				else
+				{
+					return float.Epsilon;
+				}
+			}
+		}
+
+		// Override ModuleDataTransmitter.DataResourceCost to just return packetResourceCost, because we want antennas
+		// to be scored in terms of joules/byte
+		public new float DataResourceCost
+		{
+			get
+			{
+				this.PreTransmit_SetPacketResourceCost();
+
+				if (this.CanTransmit())
+				{
+					return this.packetResourceCost;
+				}
+				else
+				{
+					return float.PositiveInfinity;
+				}
+			}
+		}
+
+		// Reports whether this antenna has been checked as a viable relay already in the current FindNearestRelay.
+		public bool relayChecked
+		{
+			get
+			{
+				return this.relay.relayChecked;
+			}
+		}
+
+		/*
+		 * Methods
+		 * */
+		// Build ALL the objects.
+		public ModuleLimitedDataTransmitter () : base()
+		{
+			this.ErrorMsg = new ScreenMessage("", 4f, false, ScreenMessageStyle.UPPER_LEFT);
+		}
+
+		// At least once, when the module starts with a state on the launch pad or later, go find Kerbin.
+		public override void OnStart (StartState state)
+		{
+			base.OnStart (state);
+
+			if (state >= StartState.PreLaunch)
+			{
+				this.relay = new AntennaRelay(vessel);
+				this.relay.maxTransmitDistance = this.maxTransmitDistance;
+
+				this.UImaxTransmitDistance = Tools.MuMech_ToSI(this.maxTransmitDistance) + "m";
+
+				GameEvents.onPartActionUICreate.Add(this.onPartActionUICreate);
+				GameEvents.onPartActionUIDismiss.Add(this.onPartActionUIDismiss);
+			}
+		}
+
+		// When the module loads, fetch the Squad KSPFields from the base.  This is necessary in part because
+		// overloading packetSize and packetResourceCostinto a property in ModuleLimitedDataTransmitter didn't
+		// work.
+		public override void OnLoad(ConfigNode node)
+		{
+			this.Fields.Load(node);
+			base.Fields.Load(node);
+
+			base.OnLoad (node);
+
+			this._basepacketSize = base.packetSize;
+			this._basepacketResourceCost = base.packetResourceCost;
+
+			Tools.PostDebugMessage(string.Format(
+				"{0} loaded:\n" +
+				"packetSize: {1}\n" +
+				"packetResourceCost: {2}\n" +
+				"nominalRange: {3}\n" +
+				"maxPowerFactor: {4}\n" +
+				"maxDataFactor: {5}\n",
+				this.name,
+				base.packetSize,
+				this._basepacketResourceCost,
+				this.nominalRange,
+				this.maxPowerFactor,
+				this.maxDataFactor
+			));
+		}
+
+		// Post an error in the communication messages describing the reason transmission has failed.  Currently there
+		// is only one reason for this.
+		protected void PostCannotTransmitError()
+		{
+			string ErrorText = string.Format (
+				"Unable to transmit: out of range!  Maximum range = {0}m; Current range = {1}m.",
+				Tools.MuMech_ToSI((double)this.maxTransmitDistance, 2),
+				Tools.MuMech_ToSI((double)this.transmitDistance, 2)
+				);
+
+			this.ErrorMsg.message = string.Format(
+				"<color='#{0}{1}{2}{3}'><b>{4}</b></color>",
+				((int)(XKCDColors.OrangeRed.r * 255f)).ToString("x2"),
+				((int)(XKCDColors.OrangeRed.g * 255f)).ToString("x2"),
+				((int)(XKCDColors.OrangeRed.b * 255f)).ToString("x2"),
+				((int)(XKCDColors.OrangeRed.a * 255f)).ToString("x2"),
+				ErrorText
+			);
+
+			Tools.PostDebugMessage(this.GetType().Name + ": " + this.ErrorMsg.message);
+
+			ScreenMessages.PostScreenMessage(this.ErrorMsg, false);
+		}
+
+		// Before transmission, set packetResourceCost.  Per above, packet cost increases with the square of
+		// distance.  packetResourceCost maxes out at _basepacketResourceCost * maxPowerFactor, at which point
+		// transmission fails (see CanTransmit).
+		protected void PreTransmit_SetPacketResourceCost()
+		{
+			if (this.transmitDistance <= this.nominalRange)
+			{
+				base.packetResourceCost = this._basepacketResourceCost;
+			}
+			else
+			{
+				base.packetResourceCost = this._basepacketResourceCost
+					* (float)Math.Pow (this.transmitDistance / this.nominalRange, 2);
+			}
+		}
+
+		// Before transmission, set packetSize.  Per above, packet size increases with the inverse square of
+		// distance.  packetSize maxes out at _basepacketSize * maxDataFactor.
+		protected void PreTransmit_SetPacketSize()
+		{
+			if (this.transmitDistance >= this.nominalRange)
+			{
+				base.packetSize = this._basepacketSize;
+			}
+			else
+			{
+				base.packetSize = Math.Min(
+					this._basepacketSize * (float)Math.Pow (this.nominalRange / this.transmitDistance, 2),
+					this._basepacketSize * this.maxDataFactor);
+			}
+		}
+
+		// Override ModuleDataTransmitter.GetInfo to add nominal and maximum range to the VAB description.
+		public override string GetInfo()
+		{
+			string text = base.GetInfo();
+			text += "Nominal Range: " + Tools.MuMech_ToSI((double)this.nominalRange, 2) + "m\n";
+			text += "Maximum Range: " + Tools.MuMech_ToSI((double)this.maxTransmitDistance, 2) + "m\n";
+			return text;
+		}
+
+		// Override ModuleDataTransmitter.CanTransmit to return false when transmission is not possible.
+		public new bool CanTransmit()
+		{
+			PartStates partState = this.part.State;
+			if (partState == PartStates.DEAD || partState == PartStates.DEACTIVATED)
+			{
+				Tools.PostDebugMessage(string.Format(
+					"{0}: {1} on {2} cannot transmit: {3}",
+					this.GetType().Name,
+					this.part.partInfo.title,
+					this.vessel.name,
+					Enum.GetName(typeof(PartStates), partState)
+				));
+				return false;
+			}
+			return this.relay.CanTransmit();
+		}
+
+		// Override ModuleDataTransmitter.TransmitData to check against CanTransmit and fail out when CanTransmit
+		// returns false.
+		public new void TransmitData(List<ScienceData> dataQueue)
+		{
+			if (this.CanTransmit())
+			{
+				base.TransmitData(dataQueue);
+			}
+			else
+			{
+				this.PostCannotTransmitError ();
+			}
+
+			Tools.PostDebugMessage (
+				"distance: " + this.transmitDistance
+				+ " packetSize: " + this.packetSize
+				+ " packetResourceCost: " + this.packetResourceCost
+			);
+		}
+
+		// Override ModuleDataTransmitter.StartTransmission to check against CanTransmit and fail out when CanTransmit
+		// returns false.
+		public new void StartTransmission()
+		{
+			PreTransmit_SetPacketSize ();
+			PreTransmit_SetPacketResourceCost ();
+
+			Tools.PostDebugMessage (
+				"distance: " + this.transmitDistance
+				+ " packetSize: " + this.packetSize
+				+ " packetResourceCost: " + this.packetResourceCost
+				);
+
+			if (this.CanTransmit())
+			{
+				StringBuilder message = new StringBuilder();
+
+				message.Append("[");
+				message.Append(base.part.partInfo.title);
+				message.Append("] ");
+
+				message.Append("Beginning transmission ");
+
+				if (this.relay.nearestRelay == null)
+				{
+					message.Append("directly to Kerbin.");
+				}
+				else
+				{
+					message.Append("via ");
+					message.Append(this.relay.nearestRelay);
+				}
+
+				ScreenMessages.PostScreenMessage(message.ToString(), 4f, ScreenMessageStyle.UPPER_LEFT);
+
+				base.StartTransmission();
+			}
+			else
+			{
+				this.PostCannotTransmitError ();
+			}
+		}
+
+		public void Update()
+		{
+			if (this.actionUIUpdate)
+			{
+				this.UItransmitDistance = Tools.MuMech_ToSI(this.transmitDistance) + "m";
+				this.UIpacketSize = this.CanTransmit() ? Tools.MuMech_ToSI(this.DataRate) + "MiT" : "N/A";
+				this.UIpacketCost = this.CanTransmit() ? Tools.MuMech_ToSI(this.DataResourceCost) + "E" : "N/A";
+			}
+		}
+
+		public void onPartActionUICreate(Part eventPart)
+		{
+			if (eventPart == base.part)
+			{
+				this.actionUIUpdate = true;
+			}
+		}
+
+		public void onPartActionUIDismiss(Part eventPart)
+		{
+			if (eventPart == base.part)
+			{
+				this.actionUIUpdate = false;
+			}
+		}
+
+		public override string ToString()
+		{
+			return string.Format(
+				"{0} on {1}.",
+				this.part.partInfo.title,
+				vessel.name
+			);
+		}
+
+		// When debugging, it's nice to have a button that just tells you everything.
+		#if DEBUG
+		[KSPEvent (guiName = "Show Debug Info", active = true, guiActive = true)]
+		public void DebugInfo()
+		{
+			PreTransmit_SetPacketSize ();
+			PreTransmit_SetPacketResourceCost ();
+
+			string msg = string.Format(
+				"'{0}'\n" + 
+				"_basepacketSize: {1}\n" +
+				"packetSize: {2}\n" +
+				"_basepacketResourceCost: {3}\n" +
+				"packetResourceCost: {4}\n" +
+				"maxTransmitDistance: {5}\n" +
+				"transmitDistance: {6}\n" +
+				"nominalRange: {7}\n" +
+				"CanTransmit: {8}\n" +
+				"DataRate: {9}\n" +
+				"DataResourceCost: {10}\n" +
+				"TransmitterScore: {11}\n" +
+				"NearestRelay: {12}",
+				this.name,
+				this._basepacketSize,
+				base.packetSize,
+				this._basepacketResourceCost,
+				base.packetResourceCost,
+				this.maxTransmitDistance,
+				this.transmitDistance,
+				this.nominalRange,
+				this.CanTransmit(),
+				this.DataRate,
+				this.DataResourceCost,
+				ScienceUtil.GetTransmitterScore(this),
+				this.relay.FindNearestRelay()
+				);
+			ScreenMessages.PostScreenMessage (new ScreenMessage (msg, 4f, ScreenMessageStyle.UPPER_RIGHT));
+		}
+		#endif
+	}
+}

--- /dev/null
+++ b/ProtoAntennaRelay.cs
@@ -1,1 +1,106 @@
+// AntennaRange © 2014 toadicus
+//
+// AntennaRange provides incentive and requirements for the use of the various antenna parts.
+// Nominally, the breakdown is as follows:
+//
+//     Communotron 16 - Suitable up to Kerbalsynchronous Orbit
+//     Comms DTS-M1 - Suitable throughout the Kerbin subsystem
+//     Communotron 88-88 - Suitable throughout the Kerbol system.
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+//
+// This software uses the ModuleManager library © 2013 ialdabaoth, used under a Creative Commons Attribution-ShareAlike
+// 3.0 Uported License.
+//
+// This software uses code from the MuMechLib library, © 2013 r4m0n, used under the GNU GPL version 3.
 
+using System;
+using System.Linq;
+
+namespace AntennaRange
+{
+	/*
+	 * Wrapper class for ProtoPartModuleSnapshot extending AntennaRelay and implementing IAntennaRelay.
+	 * This is used for finding relays in unloaded Vessels.
+	 * */
+	public class ProtoAntennaRelay : AntennaRelay, IAntennaRelay
+	{
+		// Stores the relay prefab
+		protected IAntennaRelay relayPrefab;
+
+		// Stores the prototype part so we can make sure we haven't exploded or so.
+		protected ProtoPartSnapshot protoPart;
+
+		/// <summary>
+		/// The maximum distance at which this transmitter can operate.
+		/// </summary>
+		/// <value>The max transmit distance.</value>
+		public override float maxTransmitDistance
+		{
+			get
+			{
+				return relayPrefab.maxTransmitDistance;
+			}
+		}
+
+		/// <summary>
+		/// Gets a value indicating whether this <see cref="AntennaRange.ProtoDataTransmitter"/> has been checked during
+		/// the current relay attempt.
+		/// </summary>
+		/// <value><c>true</c> if relay checked; otherwise, <c>false</c>.</value>
+		public override bool relayChecked
+		{
+			get;
+			protected set;
+		}
+
+		public string Title
+		{
+			get
+			{
+				return this.protoPart.partInfo.title;
+			}
+		}
+
+		public override bool CanTransmit()
+		{
+			PartStates partState = (PartStates)this.protoPart.state;
+			if (partState == PartStates.DEAD || partState == PartStates.DEACTIVATED)
+			{
+				Tools.PostDebugMessage(string.Format(
+					"{0}: {1} on {2} cannot transmit: {3}",
+					this.GetType().Name,
+					this.Title,
+					this.vessel.name,
+					Enum.GetName(typeof(PartStates), partState)
+				));
+				return false;
+			}
+			return base.CanTransmit();
+		}
+
+		public override string ToString()
+		{
+			return string.Format(
+				"{0} on {1}.",
+				this.Title,
+				vessel.name
+			);
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="AntennaRange.ProtoAntennaRelay"/> class.
+		/// </summary>
+		/// <param name="ms">The ProtoPartModuleSnapshot to wrap</param>
+		/// <param name="vessel">The parent Vessel</param>
+		public ProtoAntennaRelay(IAntennaRelay prefabRelay, ProtoPartSnapshot pps) : base(pps.pVesselRef.vesselRef)
+		{
+			this.relayPrefab = prefabRelay;
+			this.protoPart = pps;
+			this.vessel = pps.pVesselRef.vesselRef;
+		}
+	}
+}
+
+

file:b/RelayDatabase.cs (new)
--- /dev/null
+++ b/RelayDatabase.cs
@@ -1,1 +1,236 @@
-
+// AntennaRange © 2014 toadicus
+//
+// This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a
+// copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
+
+using KSP;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEngine;
+
+namespace AntennaRange
+{
+	public class RelayDatabase
+	{
+		/*
+		 * Static members
+		 * */
+		protected static RelayDatabase _instance;
+
+		public static RelayDatabase Instance
+		{
+			get
+			{	
+				if (_instance == null)
+				{
+					_instance = new RelayDatabase();
+				}
+
+				return _instance;
+			}
+		}
+
+		/*
+		 * Instance members
+		 * */
+
+		/*
+		 * Fields
+		 * */
+		protected Dictionary<Guid, Dictionary<int, IAntennaRelay>> relayDatabase;
+
+		protected Dictionary<Guid, int> vesselPartCountDB;
+
+		/*
+		 * Properties
+		 * */
+		public Dictionary<int, IAntennaRelay> this [Vessel vessel]
+		{
+			get
+			{
+				if (!this.ContainsKey(vessel.id))
+				{
+					this.AddVessel(vessel);
+				}
+				if (this.vesselPartCountDB[vessel.id] != vessel.Parts.Count)
+				{
+					this.UpdateVessel(vessel);
+				}
+
+				return relayDatabase[vessel.id];
+			}
+		}
+
+		/* 
+		 * Methods
+		 * */
+		public bool AddVessel(Vessel vessel)
+		{
+			if (relayDatabase.ContainsKey(vessel.id))
+			{
+				Debug.LogWarning(string.Format(
+					"{0}: Cannot add vessel '{1}' (id: {2}): Already in database.",
+					this.GetType().Name,
+					vessel.name,
+					vessel.id
+				));
+
+				return false;
+			}
+			else
+			{
+				this.UpdateVessel(vessel);
+
+				return true;
+			}
+		}
+
+		public void UpdateVessel(Vessel vessel)
+		{
+			if (!relayDatabase.ContainsKey(vessel.id))
+			{
+				Tools.PostDebugMessage(string.Format(
+					"{0}: Update called vessel '{1}' (id: {2}) not in database: vessel will be added.",
+					this.GetType().Name,
+					vessel.name,
+					vessel.id
+				));
+			}
+			else
+			{
+				// Remove stuff?
+			}
+
+			this.relayDatabase[vessel.id] = this.getVesselRelays(vessel);
+			this.vesselPartCountDB[vessel.id] = vessel.Parts.Count;
+		}
+
+		public bool ContainsKey(Guid key)
+		{
+			return (this.relayDatabase.ContainsKey(key) & this.vesselPartCountDB.ContainsKey(key));
+		}
+
+		public bool ContainsKey(Vessel vessel)
+		{
+			return this.ContainsKey(vessel.id);
+		}
+
+		public void onVesselWasModified(Vessel vessel)
+		{
+			if (this.ContainsKey(vessel))
+			{
+				if (this.vesselPartCountDB[vessel.id] != vessel.Parts.Count)
+				{
+					Tools.PostDebugMessage(string.Format(
+						"{0}: vessel '{1}' (id: {2}) was modified.",
+						this.GetType().Name,
+						vessel.name,
+						vessel.id
+					));
+
+					this.vesselPartCountDB[vessel.id] = -1;
+				}
+			}
+		}
+
+		protected Dictionary<int, IAntennaRelay> getVesselRelays(Vessel vessel)
+		{
+			Dictionary<int, IAntennaRelay> relays;
+
+			if (this.ContainsKey(vessel))
+			{
+				relays = this.relayDatabase[vessel.id];
+				relays.Clear();
+			}
+			else
+			{
+				relays = new Dictionary<int, IAntennaRelay>();
+			}
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: Getting antenna relays from vessel {1}.",
+				"IAntennaRelay",
+				vessel.name
+			));
+
+			// If the vessel is loaded, we can fetch modules implementing IAntennaRelay directly.
+			if (vessel.loaded) {
+				Tools.PostDebugMessage(string.Format(
+					"{0}: vessel {1} is loaded, searching for modules in loaded parts.",
+					"IAntennaRelay",
+					vessel.name
+				));
+
+				// Gets a list of PartModules implementing IAntennaRelay
+				foreach (Part part in vessel.Parts)
+				{
+					foreach (PartModule module in part.Modules)
+					{
+						if (module is IAntennaRelay)
+						{
+							relays.Add(part.GetHashCode(), module as IAntennaRelay);
+							break;
+						}
+					}
+				}
+			}
+			// If the vessel is not loaded, we need to build ProtoAntennaRelays when we find relay ProtoPartSnapshots.
+			else
+			{
+				Tools.PostDebugMessage(string.Format(
+					"{0}: vessel {1} is not loaded, searching for modules in prototype parts.",
+					"IAntennaRelay",
+					vessel.name
+				));
+
+				// Loop through the ProtoPartModuleSnapshots in this Vessel
+				foreach (ProtoPartSnapshot pps in vessel.protoVessel.protoPartSnapshots)
+				{
+					ProtoAntennaRelay protoRelay;
+					Part partPrefab = PartLoader.getPartInfoByName(pps.partName).partPrefab;
+
+					foreach (PartModule module in partPrefab.Modules)
+					{
+						if (module is IAntennaRelay)
+						{
+							protoRelay =
+								new ProtoAntennaRelay(module as IAntennaRelay, pps);
+							relays.Add(pps.GetHashCode(), protoRelay);
+							break;
+						}
+					}
+				}
+			}
+
+			Tools.PostDebugMessage(string.Format(
+				"{0}: vessel '{1}' has {2} transmitters.",
+				"IAntennaRelay",
+				vessel.name,
+				relays.Count
+			));
+
+			// Return the list of IAntennaRelays
+			return relays;
+		}
+
+		protected RelayDatabase()
+		{
+			relayDatabase =	new Dictionary<Guid, Dictionary<int, IAntennaRelay>>();
+			vesselPartCountDB = new Dictionary<Guid, int>();
+
+			GameEvents.onVesselWasModified.Add(this.onVesselWasModified);
+			GameEvents.onVesselChange.Add(this.onVesselWasModified);
+		}
+
+		~RelayDatabase()
+		{
+			GameEvents.onVesselWasModified.Remove(this.onVesselWasModified);
+			GameEvents.onVesselChange.Remove(this.onVesselWasModified);
+
+			Tools.PostDebugMessage(this.GetType().Name + " destroyed.");
+		}
+	}
+}
+
+