The most successful American rocket launches—for one of the last times

After Saturday night's successful delivery of a US Air Force communications satellite to orbit, the medium variant of the Delta IV rocket has now launched 26 times. All of the Delta IV medium launches, which primarily have served the US armed forces, have ended in mission success.

Other US-based rockets have launched more, but no modern rocket with all-American components, from the engines and solid-rocket motors to the upper stage, can boast of such a record of success as the Delta IV Medium. And yet now the rocket's parent company, United Launch Alliance, desperately wants to retire the booster. Why?

The answer is cost; it's about twice as expensive as competitors. “Great rocket,” the chief executive of United Launch Alliance, Tory Bruno, said in 2015 of the Delta IV. “But it’s more expensive than the equivalent Atlas rocket." The only problem with the Atlas V, which has launched about twice as many times as the Delta V, is that it uses Russian RD-180 engines rather than American-made ones.

As the US military doesn't want to be entirely reliant on Russian rocket engines to get its sensitive communications and spy satellites into space, lawmakers have been putting pressure on United Launch Alliance (ULA) to keep the Delta IV Medium flying. Even the emergence of SpaceX, and its equally capable and far less expensive Falcon 9 rocket, has done little to quell the ardor of some on Capitol Hill to keep the Delta IV flying, both in its medium and heavy variants.

Rocket politics

In a late February letter to Lisa Disbrow, the acting secretary of the US Air Force, and James MacStravic, who is performing the duties of the undersecretary of defense for acquisition, two congressmen said the Delta IV Medium and Heavy should continue to fly. US Representatives Mike Rogers (R-Ala.) and Mac Thornberry (R-Texas) required the company to report back on how it could make the Delta IV "a more cost-effective and modern launch system" for the US government.

Moreover, the letter said, the company should provide to Congress, "A detailed summary of the mechanics and costs for the Department to use the Defense Production Act to require ULA to continue to produce the Delta family of launch vehicles should it be deemed necessary."

This seems like a bit of overkill. In addition to the Atlas V and Falcon 9 vehicles, by as early as 2019 the US Department of Defense may have two or three other medium- and heavy-lift rockets to choose from for delivery of satellites to geostationary orbit: ULA's next-generation Vulcan rocket, SpaceX's Falcon Heavy, and Blue Origin's New Glenn vehicle. (The Department of Defense, to date, hasn't been interested in using NASA's even more muscular Space Launch System, primarily due to its very high cost.)

The political subtext here seems pretty clear—some congressmen don't seem to like (or trust) new space companies such as SpaceX or Blue Origin. Parochially, they also seem to like the fact that ULA does a lot of business in Alabama with its Delta IV rocket.

In any case, the medium variant of the Delta IV rocket will continue to fly a few more times. There are currently three more flights of the vehicle planned, with the final launch possibly occurring in late 2018 with another Air Force communications satellite, Wideband Global SATCOM, similar to the one that launched Saturday night.

Listing image by ULA/Jeff Spotts