rigidbody.velocity = transform.forward * Time.deltaTime * sheepSpeed;  

using UnityEngine;
using System.Collections;

public class ShipControll : MonoBehaviour {

   public float SpeedRotation = 1.0f;
     
   public float Speed = 0.0F;
   public float MaxSpeed;
   public float MinSpeed;
     
   void  Update (){
    transform.Translate(Vector3.forward * Time.deltaTime * Speed);
      
    transform.Rotate(0, Input.GetAxis("Horizontal") * SpeedRotation, 0);

    transform.Rotate(Input.GetAxis("Vertical") * SpeedRotation, 0, 0);
      
    transform.Rotate(0,0,Input.GetAxis("Strafe")*SpeedRotation*2 );
      
    Speed += Input.GetAxis("Mouse ScrollWheel")*3;
      
    if(Speed >= MaxSpeed) Speed = MaxSpeed;
    if(Speed <= MinSpeed) Speed = MinSpeed;

   }
     
   void OnGUI(){
       GUI.color = Color.red;
      
    GUI.Label (new Rect(Screen.width/2+35, Screen.height-49, 100, 500), "скорость:" + Speed);
          Speed = GUI.HorizontalSlider(new Rect(Screen.width/2, Screen.height-30, 300, 30), Speed, -5.0f, MaxSpeed);
   }

}