And the Delta Rocket Family is Done

We watched the final Delta IV Heavy launch early this afternoon, watching the coverage on Spaceflight Now, and going outside to watch at about a minute to go in the count. The trajectory was said to be going East and that appeared to be close if not exactly right. It was definitely more visible than flights to the northeast while not as visible as the ones going south into a polar orbit. The rumble from the three large boosters was very notable and got better as the rocket continued down its trajectory. 

The Delta IV Heavy, one of the world's most powerful rockets, launched for the 16th and final time Tuesday. It was the 45th and last flight of a Delta IV launcher and the final rocket named Delta to ever launch, ending a string of 389 missions dating back to 1960.

At this point it appears the Delta family now belongs to history and we'll never see another Delta launch. The payload niche that Delta IV family has carried for those 45 missions will transfer over to the Vulcan Centaur. United Launch Alliance still has Atlas missions left to fly, but no Atlas Vs have been built for years and once the remaining Atlas Vs fly, their payloads will also switch to Vulcan. As of the start of this year 17 more Atlas V missions were scheduled. It appears the next one will be the Crewed Flight Test of Boeing's Starliner capsule, NET May 6.

Screen capture of today's video, 20 seconds after launch.

Today's payload, NROL-70, was classified. Practically that means that coverage of the mission from onboard cameras is restricted and little is said publicly about the success of the mission. The estimates were that by six hours after launch, they'd have a pretty good idea of the orbit and whether it had gone as designed. That time would have been by 7:00 PM EDT, but nothing solid has been seen online yet. 

While the payload is classified, experts can glean a few insights from the circumstances of its launch. Only the largest NRO spy satellites require a launch on a Delta IV Heavy, and the payload on this mission is "almost certainly" a type of satellite known publicly as an "Advanced Orion" or "Mentor" spacecraft, according to Marco Langbroek, an expert Dutch satellite tracker.

...  In 2010, Bruce Carlson, then-director of the NRO, referred to the Advanced Orion platform as the "largest satellite in the world."
...

When viewed from Earth, these satellites shine with the brightness of an eighth-magnitude star, making them easily visible with small binoculars despite their distant orbits, according to Ted Molczan, a skywatcher who tracks satellite activity.

"The satellites feature a very large parabolic unfoldable mesh antenna, with estimates of the size of this antenna ranging from 20 to 100 (!) meters," Langbroek writes on his website, citing information leaked by Edward Snowden.

Today's launch, though, is more about the launcher than the payload. I've seen this picture in a couple of places but without a key, so I'll try to SWAG one.

Left to right, an early Delta, Delta II, Delta III, Delta IV and Delta IV Heavy.  

Final words to ULA:

"Everything that Delta has done ... is being done better on Vulcan, so this is a great evolutionary step," said Bill Cullen, ULA's launch systems director. "It is bittersweet to see the last one, but there are great things ahead."

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Changing gears rapidly, here's something different for anyone who might want to collect a piece of space program history.