Projectile not destroying game object

I'm making a 2D shooter and trying to make an enemy ship be destroyed when the players shoots a projectile at them. I'm able to get points for shooting at the enemy ship but it does not get destroyed and continues to go down the screen before it reset itself back to the top. Another issue I'm having is the player ship not colliding with the enemy ship and would pass through it instead of getting destroyed.

Script on Projectile

 using UnityEngine;
 using System.Collections;
 
 public class Projectile : MonoBehaviour {
 
     // The game object which spawned us.
     public ShipPlayerController ParentShip;
 
     // used to control how fast the game object moves
     public float MoveSpeed = 5.0f;
 
     // Use this for initialization
     void Start () {
         Destroy (gameObject, 1.5f);
 
         // find the player ship game object by name
         GameObject playerShip = GameObject.Find ("PlayerShip");
         // Acess the player Ship's script component by type
         ParentShip = playerShip.GetComponent<ShipPlayerController> ();
     }
     
     // Update is called once per frame
     void Update () {
 
     transform.position +=
             transform.up * Time.deltaTime * MoveSpeed;
     }
 
     // Called by the engine when this object collides with another object
     void OnTriggerEnter (Collider other) {
         if (other.tag == "EnemyShip") 
         {
             Destroy (gameObject);
 
             //Reward the player with some points
             ParentShip.ModScore(1);
             // Account for this enemy being hit
             ParentShip.ModEnemyHits(1);
         }
     }
 }

Script on Enemy

 using UnityEngine;
 using System.Collections;
 
 public class EnemyControllerBasic : MonoBehaviour {
 
     // List of pickup Types to spawn
     public GameObject[] PickupTypes;
 
     // The game object which spawned us.
     public ShipPlayerController PlayerShipCtrl;
 
     // Used to control how fast the game object moves
     public float MoveSpeed = 5.0f;
 
     // Use this for initialization
     void Start () {
         Destroy (gameObject, 1.0f);
 
         // Find the player ship game object by name
         GameObject playerShip = GameObject.Find("PlayerShip");
         // Access the player ship's component by type
         PlayerShipCtrl = playerShip.GetComponent<ShipPlayerController> ();
     }
     
     // Update is called once per frame
     void Update () {
         transform.position +=
             transform.up * Time.deltaTime * MoveSpeed;
     }
 
     // Called by the engine when this object collides with another
     void onTriggerEnter (Collider other) {
         // Hit the player's projectile?
         if (other.tag == "PlayerProjectile") 
         {
             // A projectile instant kills us
             Destroy(gameObject);
 
             // Drop a pickup
             SpawnPickup();
         }
         // Hit the player's ship
         else if(other.tag == "PlayerShip")
         {
             // Wrecking with the player kills us
             Destroy (gameObject);
             // Remove points from the player for hitting enemy
             PlayerShipCtrl.ModScore(-1);
         }
     }
     // Creates a random Pickup at the game object's current location
     void SpawnPickup () 
     {
         // randmoly choose an index in the pickup array
         int randIndex = Random.Range (0, PickupTypes.Length);
 
         // Use the random index to select one of the enemy tpyes to spawn
         Instantiate (PickupTypes [randIndex],
                     transform.position, transform.rotation);
     }
 
 }