First came the superfast X2 helicopter. Now Sikorsky Aircraft has put that experimental technology into a more mature package, the S-97 Raider. According to Sikorsky, the S-97 will be much faster than conventional helicopters, with a cruising speed of up to 220 knots, or 253 mph. Sikorsky hopes that the sleek, speedy design of the S-97, unveiled Thursday, will win the favor of the US Army as a potential replacement for OH-58D Kiowa Warrior helicopter. The Kiowa, which has been the Army’s primary scout helicopter since the mid-1990s, by contrast has a cruising speed in the area of 120 mph.