The Last Ever Single Stick Delta Rocket (Patreon)

Tomorrow morning the last of the single stick Delta IV's will launch, leaving the Delta IV Heavy as the only Delta design still flying. Last year we saw the final Delta II as well. The Delta IV has been more expensive to fly compared to the Atlas V, so it's only found use on military payloads, and a handful of civilian spacecraft which needed every bit of the Heavy's performance - like Parker Solar Probe.

Delta IV Heavy has launches planned out to 2023, but it will eventually stop flying as ULA is transitioning towards Vulcan as its launch vehicle, ultimately replacing both Atlas and Delta.