Video replay: Parker Solar Probe launches atop Delta 4-Heavy

Ground crews finished the initial build-up of the last “single stick” medium-lift variant of United Launch Alliance’s Delta 4 rocket on its launch pad at Cape Canaveral last week in preparation for liftoff with a GPS navigation satellite July 25.

The attachment of a mounting bracket for Virgin Orbit’s smallsat launcher under the wing of a modified passenger jetliner portends the start of a series of captive carry tests with a full-scale model of the rocket, culminating in a drop of the vehicle before the first orbital launch attempt.

A Falcon 9 rocket ignites its nine Merlin first stage engines on June 24 for a routine static test fire ahead of the planned launch of the tenth batch of Starlink broadband internet satellites.