Full Resolution Launch vehicle waits. Note the plume coming from the middle. The basic idea with New Horizons is to build the smallest-possible spacecraft and put that on the largest rocket that money can buy. The Atlas V is 200' high and weighs 1.2M lbs. The spacecraft itself is 480 kg, and the science instruments are < 20 kg of that, so it's a tiny parasite on the tip of the launch vehicle. Various parts of the vehicle are powered by solid rocket fuel, kerosene (!), and liquid oxygen (which is what's venting).
