Delta IV makes a rare retrograde launch

Blasting off a couple of days ago from Vandenberg AFB in California, a cryogenic Delta IV Medium+ launched the NROL-45 spacecraft into orbit.  NROL-45 is an undisclosed payload for the National Reconnaissance Office.  Delta IV is famous for a slightly disconcerting tendency to set its own first stage insulation on fire, particularly in the Heavy variant, but this Medium + still managed to launch in a huge fireball, with flames still alight on its scorched first stage insulation.  The insulation’s function is to reduce boiloff of the cryogenic propellants while it sits on the pad, so the fact that it has caught on fire is not a big a deal as you might think, and the rocket boasts a flawless track record (minus a slightly subpar orbit for the demonstration payload on the first Heavy launch).

The really interesting thing about this launch was that it was retrograde — against the rotation of the Earth.  The amateur satellite spotting community believes this payload to be Topaz 4, a radar-imaging spacecraft that continues the legacy of the Lacrosse constellation, although spotters have not yet offered an opinion on why it must orbit retrograde.  Retrograde orbits are very unusual because they are costly in terms of propellant and usually don’t offer any particular advantage unless one has a very restricted lane in which to launch — Israel launches exclusively retrograde satellites due to unfriendly neighbors to the north, east, and south who would not tolerate an overflight, but that is a unique situation.


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