Enlarge / United Launch Alliance's final Delta IV Heavy rocket, seen here in December when ground crews rolled it to the launch pad at Cape Canaveral Space Force Station, Florida. (credit: United Launch Alliance )

This is the rocket that literally lights itself on fire before it heads to space. It's the world's largest rocket entirely fueled by liquid hydrogen, a propellant that is vexing to handle but rewarding in its efficiency.

The Delta IV Heavy was America's most powerful launch vehicle for nearly a decade and has been a cornerstone for the US military's space program for more than 20 years. It is also the world's most expensive commercially produced rocket, a fact driven not just by its outsized capability but also its complexity.

Now, United Launch Alliance's last Delta IV Heavy rocket is set to lift off Thursday from Cape Canaveral Space Force Station, Florida, with a classified payload for the National Reconnaissance Office, the US government's spy satellite agency.

Enlarge / United Launch Alliance's Atlas 5 rocket, seen here in its "501" configuration without any solid rocket boosters. (credit: United Launch Alliance)

Amazon has confirmed it now plans to launch the first two test satellites for the company's Kuiper broadband network on a United Launch Alliance Atlas V rocket as soon as next month, shifting the payloads off of the inaugural flight of ULA's new Vulcan rocket.

The shift has been rumored for several weeks after ULA delayed the first flight of its Vulcan rocket from the summer until the fourth quarter of the year. The delay will allow time for ULA to beef up the structure of the Vulcan upper stage's liquid hydrogen tank , which sprung a leak that resulted in a destructive fireball on a test stand in March.

The first Vulcan rocket was slated to launch the first two prototype satellites for Amazon's Kuiper constellation, a network of more than 3,200 broadband satellites that the retail and tech giant plans to deploy over the next few years. The Kuiper network is similar to SpaceX's Starlink "mega-constellation," which already has more than 4,000 satellites in orbit.

Enlarge / The Super Heavy booster for SpaceX's next Starship test flight is raised onto its launch mount at the Starbase facility in South Texas. (credit: SpaceX )

Welcome to Edition 6.04 of the Rocket Report! SpaceX has a Super Heavy booster on the launch pad in Texas a lot sooner than many thought. There was some pretty extensive damage at the launch site in the aftermath of the Starship test launch in April, SpaceX made quick work with repairs and upgrades to beef up the pad. Meanwhile, SpaceX's Falcon 9 launcher, Rocket Lab's Electron, and China's rocket fleet show no signs of slowing down.

As always, we welcome reader submissions , and if you don't want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

China's Galactic Energy launches sixth successful mission . Galactic Energy, one of several new Chinese startup launch companies, launched its sixth consecutive successful satellite delivery mission on July 22, Space News reports . The company's solid-fueled Ceres 1 rocket lifted off from the Jiuquan launch base in the Gobi Desert with two small satellites on board. Galactic Energy is also developing a medium-lift rocket named Pallas 1 that is designed to eventually be recoverable and reusable.

Enlarge / Tory Bruno (L), CEO of United Launch Alliance, with Amazon founder Jeff Bezos at a news conference in 2014. (credit: Win McNamee/Getty Images)

One of the world's most important rocket companies, United Launch Alliance, may be sold later this year.

The potential sale has not been disclosed publicly, but three sources confirmed to Ars that potential buyers have been contacted about the opportunity. These sources said a deal is expected to be closed before the end of this year and that investment firm Morgan Stanley and consulting firm Bain & Company are managing the transaction.

The sale of United Launch Alliance, or ULA as it is known within the industry, would mark the end of an era that has lasted for nearly two decades. The company was officially formed in 2005 as part of a deal brokered by the US government, ensuring the military had access to both Atlas and Delta rockets to put national security satellites into space. To form ULA, Lockheed Martin and Boeing merged their launch businesses into a single company, each taking a 50 percent stake.

Enlarge / A BE-4 rocket engine undergoes tests in West Texas. (credit: Blue Origin)

Blue Origin appears to have solved some development issues related to the turbopumps in its powerful BE-4 rocket engine .

United Launch Alliance chief executive Tory Bruno said Friday that the problem was "sorted out," and that the full-scale, flight-configured BE-4 engine is now accumulating a lot of time on the test stand. Bruno made his comments about one hour into The Space Show with David Livingston.

Bruno's company, ULA, is buying the BE-4 engine to provide thrust for the first stage of its upcoming Vulcan-Centaur rocket . This booster may make its debut next year, although ULA is still awaiting delivery of BE-4s for the first flight. Two of these large engine—each providing about 25 percent more thrust than the RS-25s used on the Space Shuttle—will power each Vulcan rocket.

Read 5 remaining paragraphs | Comments