Developed at the beginning of the 1960s, the Martin Titan II was a major improvement over the Titan I, using an upgraded Aerojet-General LR87 first-stage rocket engine capable of producing 430,000 lbs of thrust and burning the hypergolic propellants Aerozine-50 fuel and nitrogen tetroxide oxidizer. Its first stage was lengthened by 10 ft to carry more propellant and increase range, while the second stage was modified with a 100,000 lb thrust LR91 rocket engine and a body diameter increased to 10 ft to match the first stage. The basic Titan II launch vehicle served various heavy-lift and spaceflight programs, including the Gemini manned space program and the X-20 Dyna-soar re-entry vehicle program, and it was designed for launch from within its underground silo, unlike the Titan I, which had to be raised to the surface before launch. Titan IIs began replacing Titan Is in the early 1960s and remained on alert well into the 1980s, when the last Titan II missile squadrons were deactivated. The nose-cone on display came from a missile that sat alert under the command of the 381st Missile Wing at McConnell AFB, Kansas, until the Titan II's retirement from Air Force service, and this Titan Re-entry Vehicle stands as a tribute to the numerous ground and missile crews that maintained the strategic deterrent force. It was donated to the 8th AF Museum in 1995. Specifications included a length of 103 ft in ICSM configuration, a diameter of 10 ft for both stages, a launch weight of 341,000 lbs, no crew, a General Electric Mk. 6 nuclear warhead, and a cost of $3,046,000. Performance included a maximum speed of 15,000 mph, an approximate maximum range of 10,000 statute miles, a maximum altitude of 700 statute miles, and engine thrust of 430,000 lbs in the first stage and 100,000 lbs in the second stage.