To deal with these more capable submarines new ASW weapons were essential. This new generation of diesel electric submarine, like the Type XXI before it, had no deck gun and a streamlined hull tower for greater underwater speed, as well as more storage battery capacity than a comparable WW2 submarine; in addition, they recharged their batteries using a snorkel and could complete a patrol without surfacing. This led to the introduction of longer-ranged forward-throwing weapons, such as Weapon Alpha, Limbo, RBU-6000, and of improved homing torpedoes. Nuclear submarines, even faster still, and without the need to snorkel to recharge batteries, posed an even greater threat; in particular, shipborne helicopters (recalling the blimps of World War I) have emerged as essential anti-submarine platforms. A number of torpedo carrying missiles such as ASROC and Ikara were developed, combining ahead-throwing capability (or longer-range delivery) with torpedo homing.