...
var shoot_var = 1;
...
function space_ship()
{
 ...
 if (key_space)  
  {	
   shoot_1(i);
  }
 ...
}


function shoot_1(i)
{ 

 if (shoot_var == 1)
 { 
  shoot_var = 0;
  wait(25);
  			
  
  snd_play(laser, 90, 0); 

  _shoot[i] = pan_create("bmap = shot.bmp;",1);
  _shoot[i].pos_x = _ship.pos_x+30;
  _shoot[i].pos_y = _ship.pos_y-20;  
  _shoot[i].flags = VISIBLE;
  shoot_var = 1;
  
  
  
 while(_shoot[i] != NULL)
 {
  if(_shoot[i].pos_y > 5)
  {
   _shoot[i].pos_y -= 1*time_step;	      
  }
  else
  {
   reset(_shoot[i],VISIBLE); 
   break;
  }   
  
  wait(1);
 }
 _shoot[i] = NULL;	
 
 } 
}