BE-4 in transport cradle
|Country of origin||United States|
|Propellant||Liquid oxygen / Liquefied natural gas|
|Thrust (SL)||2.4 MN (550,000 lbf)|
|Chamber pressure||13.4 MPa (1,950 psi)|
The Blue Engine 4 or BE-4 is an oxygen-rich liquefied-natural-gas-fueled staged-combustion rocket engine under development by Blue Origin. The BE-4 is being developed with private and public funding. The engine has been designed to produce 2.4 meganewtons (550,000 lbf) of thrust at sea level.
It was initially planned for the engine to be used exclusively on a Blue Origin proprietary launch vehicle New Glenn, the company's first orbital rocket. However, it was announced in 2014 that the engine would also be used on the United Launch Alliance (ULA) Vulcan Centaur launch vehicle, the successor to the Atlas V launch vehicle. Final engine selection by ULA happened in September 2018.
Blue Origin began work on the BE-4 in 2011, although no public announcement was made until September 2014. This is their first engine to combust liquid oxygen and liquid methane propellants. In September 2014—in a choice labeled "a stunner" by SpaceNews—the large launch vehicle manufacturer and launch service provider United Launch Alliance selected the BE-4 as the main engine for a new primary launch vehicle.
As of April 2015, the engine development work was being carried out in two parallel programs. One program is testing full-scale versions of the BE-4 powerpack, which are the set of valves and turbopumps that provide the proper fuel/oxidizer mix to the injectors and combustion chamber. The second program is testing subscale versions of the engine's injectors. Also in early 2015, the company indicated it is planning to begin full-scale engine testing in late 2016, and that they expected to complete development of the engine in 2017.
As of September 2015, Blue Origin had completed more than 100 development tests of several elements of the BE-4, including the preburner and a "regeneratively-cooled thrust chamber using multiple full-scale injector elements". The tests were used to confirm the theoretical model predictions of "injector performance, heat transfer, and combustion stability", and data collected is being used to refine the engine design. There was an explosion on the test stand during 2015 during powerpack testing. Blue Origin built two larger and redundant test stands to follow, capable of testing the full thrust of the BE-4.
In January 2016, Blue Origin announced that they intended to begin testing full engines of the BE-4 on ground test stands prior to the end of 2016. Following a factory tour in March 2016, journalist Eric Berger noted that a large part of "Blue Origin's factory has been given over to development of the Blue Engine-4".
Initially, both first-stage and second-stage versions of the engine were planned. The second stage of the initial New Glenn design was to have shared the same stage diameter as the first stage and use a single vacuum-optimized BE-4, the BE-4U.
The first engine was fully assembled in March 2017. Also in March, United Launch Alliance indicated that the economic risk of the Blue Origin engine selection option had been retired, but that the technical risk on the project would remain until a series of engine firing tests were completed later in 2017. A test anomaly occurred on 13 May 2017 and Blue Origin reported that they lost a set of powerpack hardware.
The BE-4 was first test fired, at 50% thrust for 3 seconds, in October 2017. By March 2018, the BE-4 engine had been tested at 65% of design thrust for 114 seconds with a goal expressed in May to achieve 70% of design thrust in the next several months. By September 2018, multiple hundreds of seconds of engine testing had been completed, including one test of over 200 seconds duration.
In October 2018, Blue Origin President Bob Smith announced that the first launch of the New Glenn had been moved back to 2021, which will be the first flight test of the BE-4.
By February 2019, the BE-4 had acquired a total of 1800 seconds of hot fire testing on ground test stands, but had yet to be tested above 1.8 meganewtons (400,000 lbf) pounds of thrust, about 73 percent of the engine's rated thrust of 2.4 MN (550,000 lbf).
In August 2019, Blue Origin announced that BE-4 was undergoing full power engine tests.
In August 2020, Tory Bruno stated that the second test BE-4 is going to be delivered soon followed quickly by the first flight-qualified ones.  Speaking to the Denver Business Journal 21 August 2020, ULA CEO Tory Bruno noted an ongoing issue with BE-4’s turbopumps. Blue Origin is still troubleshooting the 75,000-horsepower pumps that bring fuel to the BE-4’s main combustion chamber, Bruno said, adding that’s he confident the issues will soon be solved. In October, he stated that the issue was resolved and that the engine moved into production.
By 2017, the BE-4 was being considered for use on two launch vehicles then under development. Prior to this, a modified derivative of the BE-4 was also being considered for the experimental XS-1 spaceplane for a US military project, but was not selected. By 2018, it was the selected engine for both the Blue Origin New Glenn and the ULA Vulcan launch vehicles.
Atlas V successor - Vulcan
In late 2014, Blue Origin signed an agreement with United Launch Alliance to co-develop the BE-4 engine and to commit to use the new engine on the Vulcan launch vehicle, a successor to the Atlas V, which would replace the Russian-made RD-180 engine. Vulcan will use two of the 2.4 MN (550,000 lbf) BE-4 engines on each first stage. The engine development program began in 2011.
The ULA partnership announcement came after months of uncertainty about the future of the Russian RD-180 engine that has been used in the ULA Atlas V rocket for over a decade. Geopolitical concerns had come about that created serious concerns about the reliability and consistency of the supply chain for the procurement of the Russian engine. Initially, ULA expected the first flight of the new launch vehicle no earlier than 2019 but by 2018, that target had moved out to 2021.
Since early 2015, the BE-4 had been in competition with the AR1 engine for the Atlas V RD-180 replacement program. While the BE-4 is a methane engine, the AR1, like the RD-180, is kerosene-fueled. In February 2016, the US Air Force issued a contract that provides partial development funding of up to US$202 million to ULA in order to support use of the Blue BE-4 engine on the ULA Vulcan launch vehicle.
Initially, only US$40.8 million was to be disbursed by the government with US$40.8 million additional to be spent by a ULA subsidiary on Vulcan BE-4 development. Although US$536 million was the original USAF contract amount to Aerojet Rocketdyne (AJR) to advance development of the AR1 engine as an alternative for powering the Vulcan rocket, by June 2018, the USAF had renegotiated the agreement with AJR and decreased the Air Force contribution—5/6ths of the total cost—to US$294 million. AJR put no additional private funds into the engine development effort after early 2018.
Bezos noted in 2016 that the Vulcan launch vehicle is being designed around the BE-4 engine; ULA switching to the AR1 would require significant delays and money on the part of ULA. This point had also been made by ULA executives, who clarified that the BE-4 is likely to cost 40% less than the AR1, as well as benefit from Bezos capacity to "make split-second investment decisions on behalf of BE-4, and has already demonstrated his determination to see it through. [whereas the] AR1, in contrast, depends mainly on U.S. government backing, meaning Aerojet Rocketdyne has many phone numbers to dial to win support".
New Glenn launch vehicle
The engine is to be used on the Blue Origin large orbital launch vehicle New Glenn, a 7.0-meter (23 ft)-diameter two-stage orbital launch vehicle with an optional third stage and a reusable first stage. The first flight and orbital test is planned for no earlier than 2021, although the company had earlier expected the BE-4 might be tested on a rocket flight as early as 2020.
The first stage will be powered by seven BE-4 engines and will be reusable, landing vertically. The second stage of New Glenn will share the same diameter and use two BE-3 vacuum-optimized hydrolox engines. The second stage will be expendable.
Boeing secured a contract to design and build the DARPA XS-1 reusable spaceplane in 2014. The XS-1 was to accelerate to hypersonic speed at the edge of the Earth's atmosphere to enable its payload to reach orbit. In 2015, it was believed a modified derivative of the BE-4 engine was to power the craft. In 2017, the contract award selected the RS-25-derived Aerojet Rocketdyne AR-22 engine instead and the XS-1 was cancelled in 2020. 
Availability and use
Blue Origin has indicated that they intend to make the engine commercially available, once development is complete, to companies beyond ULA, and also plans to utilize the engine in Blue Origin's own new orbital launch vehicle. As of March 2016, Orbital ATK was also evaluating Blue engines for its launch vehicles.[needs update]
The BE-4 uses liquid methane rather than more commonly used rocket fuels such as kerosene. This approach allows for autogenous pressurization, which is the use of gasified propellant to pressurize liquid propellant. This is beneficial because it eliminates the need for pressurization systems that require the storage of a pressurizing gas, such as helium.
Although all early BE-4 components and full engines to support the test program were built at Blue's headquarters location in Kent, Washington, production of the BE-4 will be in Huntsville, Alabama. Testing and support of the reusable BE-4s will occur at the company's orbital launch facility at Exploration Park in Florida, where Blue Origin is investing more than US$200 million in facilities and improvements.
The BE-4 is a staged combustion engine, with a single oxygen rich preburner, and a single turbine driving both the fuel and oxygen pumps. The cycle is similar to the kerosene-fueled RD-180 currently used on the Atlas V, although it uses only a single combustion chamber and nozzle.
The BE-4 is designed for long life and high reliability, partially by aiming the engine to be a "medium-performing version of a high-performance architecture". Hydrostatic bearings are used in the turbopumps rather than the more typical ball and roller bearings specifically to increase reliability and service life.
- Thrust (sea level): 2.4 MN (550,000 lbf) at full power
- Chamber pressure: 13.4 MPa (1,950 psi), substantially lower than the 26 MPa (3,700 psi) of the RD-180 engine that ULA wants to replace
- Designed for reusability
- Design life: 100 launches and landings
- Restartable during flight, via head-pressure start of the turbine during coast
- Deep throttling capability to 65% power or lower
- BE-3 - hydrogen-fueled engine currently in operation by Blue Origin
- Raptor - methane-fueled engine under development by SpaceX
- Merlin - kerosene-fueled operational engine by SpaceX
- RD-180 - modern Russian kerosene-fueled engine of comparable size
- Comparison of orbital rocket engines
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Also this year, we'll start full-engine testing of the BE-4
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the two-stage New Glenn is 270 feet tall, and its second stage is powered by a single vacuum-optimized BE-4 engine (the BE-4U).
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It's performing quite well," Blue Origin Chief Executive Bob Smith said of BE-4 on the same panel as Bruno. "We've gone through several hundred seconds of firing, including an over 200-second firing of that engine, so we're feeling very good about its progress and what we're going to be able to deliver to the market, as well as for our own consumption.
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United Launch Services LLC, a majority owned subsidiary of United Launch Alliance, Centennial, Colorado, has been awarded a $46,629,267 other transaction agreement for the development of the Vulcan BE-4 and Advanced Cryogenic Evolved Stage (ACES) rocket propulsion system prototypes for the Evolved Expendable Launch Vehicle program. ... This other transaction agreement requires shared cost investment with United Launch Services for the development of prototypes of the Vulcan BE-4 rocket propulsion system, which is a booster stage engine, and .... The Vulcan BE-4 award is for $45,820,515, or 98.3 percent of the total awarded amount. ... intended for use on United Launch Alliance's Vulcan launch vehicle. ... The work is expected to be completed no later than Dec. 31, 2019. Air Force fiscal 2015 research, development, test and evaluation funds in the amount of $26,344,603 are being obligated at the time of award. United Launch Services is contributing $40,828,213 at the time of award. The total potential government investment, including all options, is $201,655,584. The total potential investment by United Launch Services, including all options, is $134,196,971.
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[550,000 lbf thrust rocket engine] performance can involve a lot of wear and tear, particularly if you're using traditional ball and roller bearings. To maximize the engine's reusability, Blue Origin's team is taking a different approach. To keep the BE-4 running smoothly, Bezos says the turbine at the heart of the engine's turbopump will use a thin film of the fluid propellants as its bearings.
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