United Launch Alliance is in the process of considering several engines for its Vulcan rocket. Representatives from ULA have previously stated that the BE-4 engine developed by Blue Origin was their top contender, but they have not made any formal decision. This lack of an announcement has led many to speculate that the Vulcan rocket itself may not be completed on schedule. While representatives had said that they were reserving their final decision until after the testing on the BE-4 engine was complete.

The BE-4 engine was developed by Blue Origin for their own vehicle launch, the New Glenn. While the New Glenn is being constructed near the Kennedy Space Centre, the BE-4 is currently being built in Huntsville, Alabama. Testing began in West Texas last year, disclosing very few details about the results except to say that they are making very good process. The company is also in the process of testing the thrust levels and burn times, both independently and together. They anticipate testing to occur for several more months.

ULA was expected to make their decision on an engine for their Vulcan rocket toward the end of last year, coinciding with the timing of the BE-4 testing. Despite the lack of a decision regarding the ideal engine, ULA representatives insist that development of their Vulcan rocket remains on schedule. They have planned their first flight for some time in mid-2020. When asked directly about the possibility of a delay, a spokesperson told reporters that they are in the competitive procurement phase and were not able to disclose any additional details.

Engine choice is an important factor in launches. This is primarily because certain engines use different types of propellants. For example, while the BE-4 relies on methane and liquid oxygen, other engines rely on RP-1, which is a type of kerosene, along with liquid oxygen. Many modern rockets rely on both liquid oxygen and kerosene set ups as well as liquid oxygen and hydrogen systems.

There are several challenges involved in trying to find a system that is compatible with the rocket itself. The team designing the BE-4 engine has to build a system that is compatible with methane at the same time as the Atlas system is also being developed. This involves an open mind in the design process. Engineers are working through the design to be sure that the design is completely compatible.

(Source: http://spacenews.com/be-4-engine-tests-continue-as-ula-waits-to-make-vulcan-engine-decision/)