 Under the original plan, HTV-1 was to feature a hypersonic lift-to-drag ratio of 2.5, increasing to 3.5-4 for the HTV-2 and 4-5 for the HTV-3.The actual lift-to-drag ratio of HTV-2 was estimated to be 2.6.HTV-2 was to lead to the development of an HTV-3X vehicle, known as Blackswift, which would have formed the basis for deployment around 2025 of a reusable Hypersonic Cruise Vehicle, an unmanned aircraft capable of taking off from a conventional runway with a 5,400 kg (12,000 lb) payload to strike targets 16,650 km away in under 2 hours.