Could Not Start Coroutine "Destroy"

#pragma strict
var projectile : Rigidbody;
var clone : Rigidbody;
function OnTap():IEnumerator {

 StartCoroutine("destroy");
		yield WaitForSeconds (5);
		Destroy (clone);
		 StopCoroutine("destroy");

}

function Update () {
	// Ctrl was pressed, launch a projectile
	if (Input.GetButtonDown("Fire1")) {
		// Instantiate the projectile at the position and rotation of this transform

		clone = Instantiate(projectile, transform.position, transform.rotation);
		
		// Give the cloned object an initial velocity along the current 
		// object's Z axis
		clone.velocity = transform.TransformDirection (Vector3.forward * 100);
		OnTap();
		
	}
}

Your coroutine is missing.

Try this one:

IEnumerator Destroy () {
yield WaitForSeconds(5);
Destroy (clone);
}