Thursday - the Last Delta IV Heavy Leaves the CCSFS

As we reported last week, Thursday is planned to be the last Delta IV Heavy flight, the NROL-70 mission of the Delta IV Heavy version of the old Delta family. Liftoff is set for 1:40 PM EDT, the start of a four hour launch window. The 45th Weather Squadron of the US Space force gives a 30% chance of acceptable weather (pdf alert) as a cold front clears the Space Coast tomorrow earlier in the day. The specific weather concerns are the launch pad winds and clouds. It goes on to say that if there's a 24 hour hold, that climbs to a 60% chance of acceptable weather.  

The last Delta IV Heavy launch from Vandenberg Space Force Base in 2022, NROL-91.  Image credit ULA.

The Delta IV Heavy got famous for setting itself on fire as it lifts off, earning the title of the Heavy Metal Rocket or Most Metal Rocket. You can see the charred colors on the three boosters in the picture above; the main core and liquid-fueled strap on boosters on either side. More importantly, the Delta IV Heavy was America's most powerful launch vehicle for almost a decade, and a cornerstone for the US military's space program for more than twice that time. This is the last flight of a legend.

"This is such an amazing piece of technology, 23 stories tall, a half-million gallons of propellant and a quarter-million pounds of thrust, and the most metal of all rockets, setting itself on fire before it goes to space," said Tory Bruno, ULA's president and CEO. "Retiring it is (key to) the future, moving to Vulcan, a less expensive higher-performance rocket. But it’s still sad.”

This isn't just the last launch of the Delta IV Heavy configuration, it's the final flight for the entire, historic Delta rocket family—the 389th rocket with the Delta name—since 1960. But those earlier rockets share virtually nothing in common with the Delta IV, which debuted in 2002. Until the Delta IV, the Deltas all had a history going back to the Thor Intermediate Range Ballistic Missiles of the Cold War era. The Delta IV was was a clean-sheet design, initially conceived by McDonnell Douglas, and acquired by Boeing when they bought the competitor in 1997. When Boeing merged with Lockheed Martin to create United Launch Alliance, Delta IV and Atlas V became the ULA vehicles.

The problem with the Delta IV family has nothing to do with its capabilities or reliability; it's the cost. At one time, launches on the D IV Heavy were $400M. The high prices kind of opened the door to SpaceX - the only real competitor to ULA - and drove ULA to develop the Vulcan which will replace both the Delta IV and Atlas V families; another name with a history back to the Cold War. 

"Delta IV Heavy is three rockets bolted together," Bruno said. "With a single core Vulcan, we’re able to collapse that cost (of Delta IV Heavy) by 70 percent and make that mission a lot more practical."

Everything about the mission profile that can be deduced points to NROL-70 being a radio reconnaissance satellite, according to the Ars Technica profile on this mission. The obvious question to the author was if being the last mission before the move to a vehicle that costs 70% less was a problem. 

When asked why not wait for a cheaper ride on Vulcan, Scolese said, "We had the spacecraft ready to go, and we had a rocket that we trust, so it made sense to continue on with this. Something has to be last and we’re proud to be on that vehicle, and we have a lot of confidence in the system."