The Blue Engine 4[2] or BE-4 is an oxygen-rich[3] liquefied-natural-gas-fueled[4] staged-combustion rocket engine under development by Blue Origin. The BE-4 is being developed with private and public funding.[5] The engine has been designed to produce 2.4 meganewtons (550,000 lbf) of thrust at sea level.[6]

Blue Engine 4
Blue Origin BE-4 rocket engine, sn 103, April 2018 -- LCH4 inlet side view.jpg
BE-4 in transport cradle
Country of originUnited States
ManufacturerBlue Origin
Liquid-fuel engine
PropellantLiquid oxygen / liquid methane
Under development
Thrust, sea-level2.4 MN (240 tf; 540,000 lbf)
Chamber pressure134 bar (1,940 psi; 13.4 MPa)
Gimbal range±5°
Used in
Vulcan Centaur
New Glenn

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.[7] Final engine selection by ULA happened in September 2018.[8]

Although previously planned to fly as early as 2019, the first flight test of the new engine is now expected no earlier than 2022 on the Vulcan rocket. The engine is running four years behind as of August 2021, and Blue has experienced a number of problems, both technical and managerial, with the engine development program, leaving the engine still not yet flight-qualified. While flight engines have not been delivered, pathfinder engines are currently undergoing testing at ULA facilities, and flight engines are being built.[9]


Following Aerojet’s acquisition of Pratt & Whitney Rocketdyne in 2012, Blue Origin president Rob Meyerson saw an opportunity to fill a gap in the defense industrial base.[10] Blue Origin publicly entered the liquid rocket engine business by partnering with ULA on the development of the BE-4, and working with other companies. Meyerson announced the selection of Huntsville, AL as the location of Blue Origin’s rocket production factory in June 2017.[11]

Blue Origin began work on the BE-4 in 2011,[12] although no public announcement was made until September 2014.[13] This was their first engine to combust liquid oxygen and liquified natural gas propellants. In September 2014—in a choice labeled "a stunner" by SpaceNews[14]—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.[14] Blue Origin said the "BE-4 would be 'ready for flight' by 2017."[5]

By April 2015, two parallel development programs were under way. One program was 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 was testing subscale versions of the engine's injectors.[15] The company planned to begin full-scale engine testing in late 2016 and expected to complete development of the engine in 2017.[15] By 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 was being used to refine the engine design.[16] 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.[17]

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.[18] 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".[7]

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.[19] In the event, they backed away from this plan.

The first engine was fully assembled in March 2017.[20][non-primary source needed] 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.[21] A test anomaly occurred on 13 May 2017 and Blue Origin reported that they lost a set of powerpack hardware.[22]

In June 2017, Blue Origin announced that they would build a new facility in Huntsville, Alabama to manufacture the large BE-4 cryogenic rocket engine.[23][needs update]

The BE-4 was first test fired, at 50% thrust for 3 seconds, in October 2017.[24] By March 2018, the BE-4 engine had been tested at 65% of design thrust for 114 seconds[25] with a goal expressed in May to achieve 70% of design thrust in the next several months.[26][non-primary source needed] By September 2018, multiple hundreds of seconds of engine testing had been completed, including one test of over 200 seconds duration.[27]

Blue Origin BE-4 rocket engine powerhead and combustion chamber, April 2018—liquified natural gas inlet side view. This was the first BE-4 engine to be hotfire tested; the test occurred on 18 October 2017.

In October 2018, Blue Origin President Bob Smith announced that the first launch of the New Glenn had been moved back to 2021,[28] and in 2021 an additional slip to late 2022 was announced.[29] This caused the first flight test of the BE-4 to be scheduled for the initial Vulcan Centaur launch rather than on New Glenn.

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).[30]

By August 2019, BE-4 was undergoing full power engine tests.[31][non-primary source needed]

In July 2020, the first pathfinder BE-4 was delivered to United Launch Alliance for integration testing with Vulcan Centaur.[32][33]

In August 2020, ULA CEO Tory Bruno stated that the second test BE-4 would be delivered soon, followed quickly by the first flight-qualified ones.[34] He noted an ongoing issue with the BE-4’s turbopumps. At the time, Blue Origin was still troubleshooting the 75,000-horsepower pumps that bring fuel to the BE-4’s main combustion chamber, Bruno said, adding that he was confident the issues would be resolved soon.[35] In October, Bruno stated that the issue was resolved and that the engine was moved into production;[36] but it was not.[citation needed]

By August 2021, it had become clear, even publicly, that the BE-4 engine program was in trouble. Delays had been accruing in the program for four years, including turbopump problems, combustion instability, overheating, and shorter-than-planned engine life. In addition, company management issues have left insufficient hardware to build development engines, leading to extended periods where no testing could be done, as well as issues related to company CEO Bob Smith and Jeff Bezos' distractions. Blue Origin has had difficulty getting the engines to run successfully at full power for a full-duration burn. The company made the "risky decision"[5] to ship the flight engines—currently not fully assembled—to their customer, ULA, before they had completed full qualification testing, meaning formal delivery may still occur in early 2022 rather than the earlier promised dates. According to long-time space reporter Eric Berger of Ars Technica, the relationship with ULA has deteriorated, in part because Blue tried to renegotiate for a higher price in 2017 than had been agreed to in 2014.[5]


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,[citation needed] but was not selected. By 2018, it was the selected engine for both the Blue Origin New Glenn and the ULA Vulcan launch vehicles.


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.[14] 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.[1][37][13]

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.[38] Initially, ULA expected the first flight of the new launch vehicle no earlier than 2019[13][14] but by 2018, that target had moved out to 2021.[39]

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 liquified natural gas engine, the AR1, like the RD-180, is kerosene-fueled.[40] 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.[41][42]

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.[43] Although US$536 million was the original USAF contract amount to Aerojet Rocketdyne (AR) to advance development of the AR1 engine as an alternative for powering the Vulcan rocket,[41] by June 2018, the USAF had renegotiated the agreement with AR and decreased the Air Force contribution—5/6ths of the total cost—to US$294 million. ARR put no additional private funds into the engine development effort after early 2018.[27]

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.[44] 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".[45]

New GlennEdit

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 late 2022,[29] although the company had earlier expected the BE-4 might be tested on a rocket flight as early as 2020.[19]

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.[46] The second stage will be expendable.[19]


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.[47] In 2015, it was believed a modified derivative of the BE-4 engine was to power the craft.[48] In 2017, the contract award selected the RS-25-derived Aerojet Rocketdyne AR-22 engine instead. The XS-1 was cancelled in 2020.[49][50]

Availability and useEdit

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.[38] As of March 2016, Orbital ATK was also evaluating Blue engines for its launch vehicles.[7][needs update]

The BE-4 uses liquified natural gas 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.[51] 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.[44]

Technical specificationsEdit

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.[4] 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".[7] Hydrostatic bearings are used in the turbopumps rather than the more typical ball and roller bearings specifically to increase reliability and service life.[52]

  • Thrust (sea level): 2.4 MN (550,000 lbf) at full power[52][13]
  • 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[7]
  • Designed for reusability — up to 100 flights and landings[7][52][53][non-primary source needed][54]
  • Relightable in-flight via head-pressure start of the turbine during coast[17]
  • Deep throttling capability to 65% power or lower[55]

See alsoEdit


  1. ^ a b Achenbach, Joel (2014-09-17). "Jeff Bezos's Blue Origin to supply engines for national security space launches". The Washington Post. Archived from the original on 2014-09-25. Retrieved 2014-09-27.
  2. ^ Alan Boyle (17 September 2014). "Bezos vs. Musk: Blue Origin and ULA Turn Up the Heat in Rocket Battle". NBC News. Archived from the original on 11 June 2015. Retrieved 11 June 2015.
  3. ^ "Rocket Engines Designed for Reuse". Blue Origin. Archived from the original on 3 February 2019. Retrieved 28 February 2019.
  4. ^ a b "BE-4". Blue Origin.[permanent dead link]
  5. ^ a b c d Berger, Eric (5 August 2021). "Blue Origin's powerful BE-4 engine is more than four years late—here's why". Ars Technica. Retrieved 6 August 2021.
  6. ^ "BE-4 Rocket Engine" (PDF). ULA. Archived (PDF) from the original on 2020-07-27. Retrieved 2020-07-27.
  7. ^ a b c d e f Berger, Eric (2016-03-09). "Behind the curtain: Ars goes inside Blue Origin's secretive rocket factory". Ars Technica. Archived from the original on 2016-03-09. Retrieved 2016-03-09.
  8. ^ "United Launch Alliance Building Rocket of the Future with Industry-Leading Strategic Partnerships". 28 Sep 2018. Archived from the original on 28 September 2018. Retrieved 27 September 2018.
  9. ^ @torybruno (24 September 2021). "@CelloRocket Testing continues. Performance continues to look great. Some momentary worry beads about the nationw…" (Tweet) – via Twitter.
  10. ^ #01 Building Blue Origin with Rob Meyerson, retrieved 2021-05-19
  11. ^ Berger, Eric (2017-06-28). "Why is Jeff Bezos building rocket engines in Alabama? He's playing to win". Ars Technica. Retrieved 2021-05-19.
  12. ^ Foust, Jeff (2015-09-30). "Blue Origin Reaches Milestone in BE-4 Engine Development". Space News. Retrieved 2021-12-30.
  13. ^ a b c d Ferster, Warren (2014-09-17). "ULA To Invest in Blue Origin Engine as RD-180 Replacement". Space News. Retrieved 2021-06-11.
  14. ^ a b c d Mike Gruss (April 24, 2015). "Evolution of a Plan: ULA Execs Spell Out Logic Behind Vulcan Design Choices". Space News. Archived from the original on April 25, 2015. Retrieved April 25, 2015.
  15. ^ a b Jeff Foust (April 7, 2015). "Blue Origin Completes BE-3 Engine as BE-4 Work Continues". Space News. Archived from the original on April 8, 2015. Retrieved April 8, 2015.
  16. ^ "Blue Origin Completes More Than 100 Staged-Combustion Tests in Development of BE-4 Engine". Blue Origin. 20 September 2015. Archived from the original on 21 September 2017. Retrieved 12 January 2016.
  17. ^ a b de Selding, Peter B. (2016-03-16). "ULA intends to lower its costs, and raise its cool, to compete with SpaceX". SpaceNews. Archived from the original on 2016-03-17. Retrieved 2016-03-19. [Blue Origin] did blow up one of their engines on the test stand ... restart the engine ... head pressure start of the turbine ... [Blue] blew up a powerpack under test ... [Bezos] opened up his checkbook, ... need to rebuild test stand, move up to 500 k powerpack for the Vulcan BE-4 engine; not one but two test stands ... agility to ... write with own checkbook is just refreshing
  18. ^ Berger, Brian (2016-01-23). "Launch. Land. Repeat: Blue Origin posts video of New Shepard's Friday flight". SpaceNews. Retrieved 2016-01-24. Also this year, we'll start full-engine testing of the BE-4
  19. ^ a b c Bergin, Chris (12 September 2016). "Blue Origin introduce the New Glenn orbital LV". Archived from the original on 13 September 2016. Retrieved 13 November 2018. 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).
  20. ^ @JeffBezos (2017-03-06). "1st BE-4 engine fully assembled. 2nd and 3rd following close behind. #GradatimFerociter" (Tweet). Archived from the original on 2017-03-07. Retrieved 2017-03-06 – via Twitter.
  21. ^ "Bruno: Vulcan engine downselect is Blue's to lose". SpaceNews. April 5, 2017. Archived from the original on April 6, 2017. Retrieved March 17, 2021.
  22. ^ "Blue Origin suffers BE-4 testing mishap". SpaceNews. May 15, 2017. Archived from the original on August 18, 2017. Retrieved March 17, 2021.
  23. ^ Berger, Eric (28 June 2017). "Why is Jeff Bezos building rocket engines in Alabama? He's playing to win". Archived from the original on 2017-07-03. Retrieved 2017-07-06.
  24. ^ Berger, Eric (19 October 2017). "Blue Origin just sent a jolt through the aerospace industry". Ars Technica. Archived from the original on 19 October 2017. Retrieved 19 October 2017.
  25. ^ Blue Origin (2018-03-14), BE-4 Engine test: 65% power level and 114 seconds, archived from the original on 2018-09-28, retrieved 2018-03-20
  26. ^ @jeff_foust (22 May 2018). "Ariane Cornell, Blue Origin: key for us in the next few months is continued BE-4 engine testing. Up to 70% thrust,…" (Tweet) – via Twitter.
  27. ^ a b Foust, Jeff (25 September 2018). "Aerojet Rocketdyne seeks other customers for AR1 engine". SpaceNews. Retrieved 27 September 2018. 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.
  28. ^ @b0yle (10 October 2018). "Latest schedule from @blueorigin CEO Bob Smith at #afasummit2018: People to fly on #NewShepard starting n first hal…" (Tweet) – via Twitter.
  29. ^ a b "Blue Origin delays first launch of New Glenn to late 2022". SpaceNews. 25 February 2021. Archived from the original on 22 September 2021. Retrieved 25 February 2021.
  30. ^ Mosher, Dave (23 February 2019). "Jeff Bezos just gave a private talk in New York. From utopian space colonies to dissing Elon Musk's Martian dream, here are the most notable things he said". Business Insider. Archived from the original on 24 February 2019. Retrieved 2019-02-25.
  31. ^ @blueorigin (2019-08-02). "BE-4 continues to rack up time on the test stand. Here's a great shot of our full power engine test today…" (Tweet). Archived from the original on 2019-08-07. Retrieved 2019-08-09 – via Twitter.
  32. ^ "Blue Origin delivers the first BE-4 engine to United Launch Alliance". SpaceNews. July 2, 2020. Archived from the original on July 4, 2020. Retrieved August 14, 2020.
  33. ^ "Blue Origin Rocket Engine Delivered to US' United Launch Alliance, to End Russian Imports". Archived from the original on 2020-08-07. Retrieved 2020-08-14.
  34. ^ "Tory Bruno on ULA's big win: 'We knew we were going to be competitive'". SpaceNews. August 11, 2020. Retrieved August 14, 2020.
  35. ^ "United launch alliance space force spacex contract". August 20, 2020. Archived from the original on 2021-02-05. Retrieved 2021-03-17.
  36. ^ "With turbopump issues "sorted out," BE-4 rocket engine moves into production". 26 October 2020. Archived from the original on 26 October 2020. Retrieved 26 October 2020.
  37. ^ "ULA taps Blue Origin for powerful new rocket engine". September 17, 2014. Archived from the original on December 20, 2016. Retrieved 2015-04-08.
  38. ^ a b Foust, Jeff (2014-09-22). "Commercial crew and commercial engines". The Space Review. Archived from the original on 2021-03-26. Retrieved 2014-10-01.
  39. ^ Foust, Jeff (25 October 2018). "ULA now planning first launch of Vulcan in 2021". SpaceNews. Retrieved 13 February 2020.
  40. ^ Mike Gruss (27 February 2015). "Timing of Russian Engine Ban Puts ULA, Air Force, in a Bind". Space News. Archived from the original on 2015-02-28. Retrieved 2015-04-08.
  41. ^ a b Gruss, Mike (2016-02-29). "Aerojet Rocketdyne, ULA win Air Force propulsion contracts". SpaceNews. Archived from the original on 2016-12-18. Retrieved 2016-03-01.
  42. ^ "". Archived from the original on 2016-03-01. Retrieved 2016-03-01.
  43. ^ "Contracts: Press Operations Release No: CR-037-16". U.S. DEPARTMENT OF DEFENSE. 2016-02-29. Archived from the original on 2016-03-01. Retrieved 2016-03-01. 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.
  44. ^ a b Price, Wayne T. (2016-03-12). "Jeff Bezos' Blue Origin could change the face of space travel". Florida Today. Archived from the original on 2018-01-06. Retrieved 2016-03-13.
  45. ^ Foust, Jeff (2016-03-17). "ULA VP resigns following remarks on company's competitive position, strategy". SpaceNews. Archived from the original on 2016-12-18. Retrieved 2016-03-17.
  46. ^ "Blue Origin switches engines for New Glenn second stage". 2018-03-29. Archived from the original on 2018-03-29. Retrieved 2018-04-28.
  47. ^ "Work Commences on Experimental Spaceplane (XS-1) Designs". 15 July 2014. Archived from the original on 30 October 2016. Retrieved 20 September 2016.
  48. ^ David Axe (2015-08-03). "Pentagon Preps for Orbital War With New Spaceplane". The Daily Beast. Archived from the original on 2015-08-04. Retrieved 2015-08-03.
  49. ^ Jason Rhian (2017-05-07). "DARPA selects rocket engine for XS-1 experimental spaceplane". SpaceFlightInsider. Archived from the original on 2017-06-27. Retrieved 2017-07-12.
  50. ^ "Boeing drops out of DARPA Experimental Spaceplane program". 2020-01-22. Archived from the original on 2020-08-26. Retrieved 2020-07-02.
  51. ^ Emre Kelly (2017-06-26). "Blue Origin selects Alabama for rocket engine production, ending Florida's hopes". Florida Today. Archived from the original on 2021-03-26. Retrieved 2017-07-12.
  52. ^ a b c Boyle, Alan (2017-03-20). "Jeff Bezos does a deep dive into bearings in Blue Origin's BE-4 rocket engine update". Yahoo Finance. Archived from the original on 2018-04-23. Retrieved 2018-04-23. [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.
  53. ^ @CHenry_QA (2018-06-25). "Correction from Ariane: New Glenn first stage can do 25 missions, BE-4 engines designed for 100 flights each" (Tweet). Archived from the original on 2021-03-26. Retrieved 2019-05-27 – via Twitter.
  54. ^ Sheetz, Michael (2018-04-18). "Blue Origin's new rocket engine will be able to launch '100 full missions', CEO says". CNBC. Archived from the original on 2019-05-27. Retrieved 2019-05-27.
  55. ^ "Archived copy". Archived from the original on 2018-09-28. Retrieved 2018-03-14.{{cite web}}: CS1 maint: archived copy as title (link)

External linksEdit

  • ULA February 2016 statement following US Air Force partial-funding of BE-4 development
  • BE-4 in Transport Cradle
  • Irene Klotz (Oct 27, 2017). "Blue Origin Fires Up BE-4 Methane-Fuel Rocket Engine". Aviation Week & Space Technology. Blue Origin marks successful first hotfire of BE-4 rocket engine.
  • BE-4 update video, Blue Origin, February 2020.