th an American Delta IV Heavy launcher put another American spy satellite into orbit, a job the Space Shuttle had handled for three decades. This was the seventh use of the Delta IV Heavy in the last nine years. Six of those launches were successful. Details of the spy satellite recently put into orbit were not released, they rarely are. But based on what is known, this was a big bird, because the Delta IV Heavy is the largest satellite launcher in service. The Delta IV series has been in use for nine years. The American Delta IV Heavy is basically a replacement for the Space Shuttle. The Delta IV family has had a 96 percent success rate (one failure in 24 launches) and has successfully replaced the Space Shuttle. Because Shuttle missions were always manned, and the system was even more complex than any unmanned rocket, maintenance and quality control expenses were much higher. But so was the success rate, with the Shuttle surviving 98.5 percent of its missions. In the end, there was enough money for unmanned expendable launchers but not for the Shuttle.
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The Delta IV is a modular system, allowing engine and fuel tank parts to be configured to launch satellites carrying up to 25 tons into low (for the space station and some surveillance satellites) orbit, 13 tons into GTO (communications satellites), and 6.2 tons into GEO (stationary) orbit. Another feature of the Delta IV is a second stage that can put itself into orbit and restart its engine for precise placement of satellites. Launch cost is $10 million to $20 million per ton of payload versus $25 million a ton for the Shuttle. The Delta IV is expensive for commercial satellites, but the Delta IV Heavy is one of the few rockets that can put up larger and heavier military satellites, so most of its work has come from the Department of Defense.
The Delta IV was built to take up some of the slack created by the end of the Space Shuttle program. The Space Shuttle was the most expensive way to get stuff into orbit. Moreover, latest version of the Delta IV Heavy has a max payload of 25 tons for low orbit while the Space Shuttle could lift up to 24 tons. As a result, the 733 ton Delta IV Heavy is a cheaper and effective substitute for the 2,000 ton Space Shuttle (which is more spacious and reusable but withdrawn from service because it was too expensive to operate). The Space Shuttle was supposed to provide a cheaper, reusable manned satellite launcher and general-purpose manned orbital vehicle. In the end, the expendable unmanned launchers, like the Delta IV Heavy, proved to be an effective and cheaper competitor.