Later this year, the United Launch Alliance will sunset its workhorse rocket, the Atlas V, and begin the era of the Vulcan rocket.

Atlas V has seen an impressive 93 launches in its nearly 20-year-long history, making it the longest active launch vehicle in the United States. What’s more is that Atlas V had only one partial failure, when the rocket couldn’t insert a payload for the National Reconnaissance Office into its intended orbit — but after the satellites were able to compensate for the issue, the NRO deemed it a mission success.

With 23 launches left, Atlas V’s impressive run is ending — but why? There are many reasons, but Russian aggression in Ukraine plays a major role.

Vulcan: Vulcan-Centaur configuration and specs

Replacing a core launch vehicle is no easy task, and ULA has every reason to stick with Atlas V. Despite this, the company feels confident in replacing it with a bigger, better rocket. Enter Vulcan. Vulcan has a more complicated “modular” upper stage, and the entire rocket is built upon a completely different system than Atlas V.

Currently, ULA will launch Vulcan with a “Vulcan-Centaur” configuration. This “Centaur” upper stage comes equipped with two RL10C engines, which marks nearly 60 years’ worth of use for this engine model. The RL10 series has been fired almost 700 times in space and represents a continuation of ULA’s “play it safe” attitude. Similarly, Vulcan Centaur can come equipped with up to 6 solid rocket boosters, similar to variants found on Delta II and Delta IV rockets.

In stark contrast, the lower stage is powered by a pair of the controversial BE-4 engines, manufactured by Jeff Bezos’ aerospace company Blue Origin. Originally planned to be custom-made for Blue Origin’s New Glenn launch vehicle, ULA ultimately agreed with the company to use these engines for Vulcan Centaur.

Marred by constant development and production delays, Blue Origin initially claimed the engines would be “flight ready” by 2017, but this was pushed back repeatedly. Reportedly, the relationship between ULA and Blue Origin has been rocky due to the five-year delay. BE-4 has never been flight-tested, so Vulcan’s maiden launch later this year will mark its first real-life use — a possible risk point for a risk-averse company like the ULA.

Atlas V customers and launch history

The Atlas V rocket was a workhorse for not only ULA but for its clients as well. In particular, the Atlas V has been a favorite launch vehicle of the military, thanks to its near-perfect track record. The ULA has launched several payloads, including “military comsat” satellites, reconnaissance satellites for NRO, and GPS satellites managed by the Department of Defense.

It is also the launch vehicle of choice for the Boeing Starliner, which recently completed its first mission to the International Space Station.

Atlas V isn’t a slacker when it comes to science missions, either. In 2005, an Atlas V rocket launched the coveted Mars Reconnaissance Orbiter, which continues to send back beautiful images and conducts valuable research about Mars’ geology.

Other NASA missions launched on an Atlas V include:

• The Pluto-flyby mission New Horizons, currently on its way out of the Solar System
• The Solar Dynamics Observatory, which keeps a continuous eye on our home star
• Juno, a Jupiter orbiter that studies the interior of our Solar System’s largest planet
• The Curiosity rover, a nuclear-powered workhorse that investigates Mars for signs of past water activity
• Its follow-on, the Perseverance rover, which is searching for signs of ancient life
• Solar Orbiter, an ESA mission to investigate the polar regions of the Sun
• And most recently, Lucy, a mission that will study a group of asteroids in front of and behind Jupiter called the Trojans, which could represent some of the most pristine materials in the Solar System

With such an extensive catalog, Atlas V has enabled NASA to accomplish much.

ULA Vulcan cost and first launch

The first launch date of the Vulcan is set for this year, though there’s no official date yet. SpaceflightNow, which keeps a robust calendar of space launches, has the flight listed for “late 2022.” A 2022 launch date was reiterated by Tony Bruno, ULA chief executive, in March.

The payload of this first mission will reportedly be the Peregrine lunar lander, a private vehicle built by Astrobotic. It will carry with it a secondary payload from Celestis containing the ashes of among others, Star Trek creator Gene Roddenberry and his wife, Majel Barrett Roddenberry, who played many roles in the franchise. Roddenberry died in 1991, while Barrett Roddenberry died in 2008.

Reuters reported in 2020 that Vulcan will cost about $100-200 million per launch, depending on configuration. The Atlas V can cost up to $153 million per launch but with less heavy lift capability.

Launch capabilities between Atlas V and Vulcan (and Starship)

As demonstrated by its mission history, Atlas V is a pretty flexible rocket. It’s capable of sending payloads in a wide variety of locations, including low Earth orbit (LEO), medium Earth orbit (MEO), geostationary transfer orbit (GTO), heliocentric orbit, and more. This diversity of orbits is possible because of the rocket’s launch capabilities. In its 551 configuration, Atlas V has placed up to 18,800 kg into LEO. Similarly, it has launched 8,900 kg into GTO.

Vulcan, an even more powerful rocket, could theoretically launch up to 27,200 kg to LEO if equipped with six solid rocket boosters. This Vulcan Centaur VC6 configuration could also lift 13,600 kg to GTO. (A proposed Vulcan Centaur Heavy has identical LEO/GTO launch capability as Vulcan Centaur VC6.)

Notably, this would still place ULA behind SpaceX in terms of launch capability if SpaceX’s dreams of Starship come to pass. The company estimates that its behemoth rocket could lift at least 100,000 kg to LEO and 21,000 kg to GTO. Of course, massive rockets like Starship face the question of whether anyone needs that much payload capacity. Both Atlas V and Vulcan are built to launch the payloads of the present, which are also made with the limitations of these rockets in mind.

How Russia’s Annexation of Crimea prompted the switch to Vulcan

Like anything else, Atlas V can’t stay in the spotlight forever. The rocket relies on Russian-made RD-180 engines. The Russian manufacture of the engines is a significant security concern for the US military. Issues arose even before Russia’s current invasion of Ukraine. Particularly after the Russian annexation of Crimea in Ukraine in 2014, the United States government began pursuing contingency plans in the case of sanctions imposed on the Russian Federation. Soon after, a ban on purchasing RD-180s was passed — and rescinded the following year — by Congress.

In response to the tumult caused by Russia’s capture of Crimea and the reaction from Congress, ULA announced that it would contract Blue Origin for its BE-4 engines. Because the BE-4s rely on a less-dense oxygen-rich liquefied natural gas (LNG) than the RD-180’s RP-1/LOX mixture, the engines require much larger fuel tanks. This is one of the main reasons why ULA decided it was time to develop a new rocket to replace Atlas V.

Inverse analysis — In the wake of Russia’s unprecedented invasion of Ukraine, it seems like ULA made the right call in choosing to move away from the RD-180s when they did. Since recent sanctions have deemed “normal trade relations” with Russia void for the foreseeable future, ULA is depending on Blue Origin to provide its BE-4 engines more than ever.