Questions tagged [delta4]

The Delta 4 booster family is an evolution of the Delta boosters but shares little in common at this point.

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Why does Delta IV have a programmed hold at T-4 minutes? [duplicate]

Why is this hold a planned part of the launch sequence? Can the delay at this point vary to allow for better launch conditions (eg weather, range obstruction)?
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Why are some rockets orange?

After many successful launches with the Delta II, ULA made the Delta IV rocket orange. What's the reason for this strange color change? Also the Atlas V's first stage is orange, is there any ...
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With 31/32 successful launches why isn't the Delta IV a category 3 certified launch vehicle

I'm having some trouble understanding the requirements for launch vehicle certification. According to NPD 8610.7D the requirements for a category three LV are "a demonstrated flight record of a ...
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What are the advantages of Delta IV over Atlas V

I have read many times that the Delta IV is more expensive to launch than the Atlas V. Outside of the Delta IV Heavy configuration, which is in a class by itself for certain payloads and missions, are ...
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What does the US Govt get out of its Assured Access funding of ULA?

ULA gets a so called subsidy (currently purported to be $800 million a year, since it is being considered to be cancelled) for Assured Access to space. Their lack of a bid on the GPS3 launch contract ...
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Could a Delta 4 Heavier be built?

The Delta 4 vehicle is a common booster core (CBC) design, where a single booster design can be used to launch in single stick mode, or in triple stick (Heavy) mode. The single stick model also has ...
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Technical reasons for Delta 4 medium phase out

This news item quotes Elon Musk as saying it would make sense for the government to rely on ULA's Delta 4 and the SpaceX Falcon 9, phasing out the venerable Atlas 5. "You don't need both of ...
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Why is the nozzle of Delta IV capped?

Source: Lockheed Martin press release: Boosters for Orion’s Launch Vehicle Arrive to Cape Canaveral, Image credit: NASA In the above image you can see that the nozzles are not open; instead they are ...
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Are the three core boosters in a Delta 4-Heavy interchangeable?

I was reading an article about the 2 of the 3 cores arriving by barge from Decatur at CCAFS and it noted that the two would be the Starboard and center cores. This made me wonder what differences in ...
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Why not use Sparklers on Delta-4 Heavy launches to burn off the hydrogen?

With three CBC (Common Booster Core) modules firing their RS-68A engines simultaneously, a Delta 4 Heavy launch is an impressive sight. The RS-68 is a LOX/LH2 engine. As part of the launch sequence, ...