Housing in a tube presented several problems, but primary among them was that there was no way for the missile's seeker to lock-on before launch. The original concept would be firing against interceptor aircraft that were slowly approaching the B-52 and would be somewhere fairly close to directly behind the aircraft. In the case of a fighter, the target might not be so conveniently located, and with no way to know if it could see the target while inside the tube, this meant it might never lock-on properly.