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109-592: EELV may refer to: Evolved Expendable Launch Vehicle, the former name of the National Security Space Launch program Europe Ecology – The Greens (French: Europe Écologie – Les Verts ), a political party in France Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title EELV . If an internal link led you here, you may wish to change

218-797: A 5 m payload fairing. Delta IV CBCs and DCSSs were integrated horizontally before being transported to the launchpad. In 2020, ULA announced retirement of the Delta IV after 5 more launches. The final flight occurred in April 2024. Each Atlas V launch vehicle is based on a Common Core Booster powered by one NPO Energomash RD-180 engine with two combustion chambers and a Centaur upper stage powered by one or two Pratt & Whitney Rocketdyne RL10A-4-2 engines. Up to five Aerojet Rocketdyne Graphite-Epoxy Motor solid rocket boosters can be added to increase vehicle performance, and two diameters of payload fairing are available. A three-digit naming convention

327-486: A chamber pressure of 3,172 psi (21,870 kPa). The three participating companies submitted their engine development bids in April 1971, with Rocketdyne being awarded the contract on July 13, 1971—although work did not begin on engine development until March 31, 1972, due to a legal challenge from P&W. Following the awarding of the contract, a preliminary design review was carried out in September 1972, followed by

436-403: A common shaft. Mixing of the fuel-rich hot gases in the turbine section and the liquid oxygen in the main pump can create a hazard and, to prevent this, the two sections are separated by a cavity that is continuously purged by the engine's helium supply during engine operation. Two seals minimize leakage into the cavity; one seal is located between the turbine section and the cavity, while the other

545-461: A competitive contract award to launch national security spacecraft was conducted between United Launch Alliance (ULA), Northrop Grumman Innovation Systems (NGIS), Blue Origin , and SpaceX. Two providers were to be selected to launch spacecraft to a number of reference orbits. In October 2018, the USAF awarded development funding to ULA, NGIS, and Blue Origin to further the design of their rockets before

654-558: A contract under the EELV program to launch a GPS Block III satellite payload to MEO . The USAF began the process of competitively selecting the next generation NSSL vehicles in 2018. Announced performance requirements include: Category A payloads fit within a 4 m diameter payload envelope , category B payloads fit within a 5 m diameter payload envelope, and category C payloads require an extended 5 m diameter envelope. The USAF and United States Space Force (USSF) plan to use

763-484: A critical design review in September 1976 after which the engine's design was set and construction of the first set of flight-capable engines began. A final review of all the Space Shuttle's components, including the engines, was conducted in 1979. The design reviews operated in parallel with several test milestones, initial tests consisting of individual engine components which identified shortcomings with various areas of

872-413: A draft RFP for "Phase 3" of NSSL, which covers the five fiscal years 2025-2029. Unlike the earlier NSSL contracts, Phase 3 is divided into two "lanes". Lane 1 covers less demanding missions and is structured to encourage new launch providers. Lane 2 is more similar to Phase 2 and requires each provider to be able to handle all NSSL requirements. However, Lane 2 allows for up to three providers instead of just

981-632: A first launch of New Glenn in 2021. In the event, no phase 2 funding from the US government was forthcoming after August 2020 when ULA Vulcan and SpaceX were selected by the Air Force. Blue Origin is considered likely to continue building and testing New Glenn, in part since they were already privately funding development prior to the Air Force NSSL competition. Northrop Grumman was awarded US$ 792 million of phase 1 funding in 2018 for development of OmegA. OmegA

1090-491: A hot-gas manifold cooling circuit. The gaseous hydrogen and liquid oxygen enter the chamber at the injector, which mixes the propellants. The mixture is ignited by the "Augmented Spark Igniter", an H 2 /O 2 flame at the center of the injector head. The main injector and dome assembly are welded to the hot-gas manifold, and the MCC is also bolted to the hot-gas manifold. The MCC comprises a structural shell made of Inconel 718 which

1199-498: A mass of approximately 3.5 tonnes (7,700 pounds), and is capable of throttling between 67% and 109% of its rated power level in one-percent increments. Components of the RS-25 operate at temperatures ranging from −253 to 3,300 °C (−400 to 6,000 °F). The Space Shuttle used a cluster of three RS-25 engines mounted at the stern of the orbiter , with fuel drawn from the external tank . The engines were used for propulsion throughout

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1308-505: A milestone that was reached on March 23, 1980, with the engine having undergone 110,253 seconds of testing by the time of STS-1 both on test stands at Stennis Space Center and installed on the Main Propulsion Test Article (MPTA). The first set of engines (2005, 2006 and 2007) was delivered to Kennedy Space Center in 1979 and installed on Columbia , before being removed in 1980 for further testing and reinstalled on

1417-406: A new design based on a high-pressure combustion chamber running around 3,000 psi (21,000 kPa), which increases the performance of the engine. Development began in 1970, when NASA released a request for proposal for 'Phase B' main engine concept studies, requiring development of a throttleable, staged combustion , de Laval-type engine. The request was based on the then-current design of

1526-444: A number of pad failures (redundant set launch sequencer aborts, or RSLSs) and other issues during the course of the program: During the period preceding final Space Shuttle retirement , various plans for the remaining engines were proposed, ranging from them all being kept by NASA, to them all being given away (or sold for US$ 400,000–800,000 each) to various institutions such as museums and universities. This policy followed changes to

1635-643: A series of studies on high-pressure engines, developed from the successful J-2 engine used on the S-II and S-IVB upper stages of the Saturn V rocket during the Apollo program . The studies were conducted under a program to upgrade the Saturn V engines, which produced a design for a 350,000 lbf (1,600 kN) upper-stage engine known as the HG-3 . As funding levels for Apollo wound down

1744-568: A six-stage turbine powered by high-pressure liquid oxygen from the high-pressure oxidizer turbopump (HPOTP). It boosts the liquid oxygen's pressure from 0.7 to 2.9 MPa (100 to 420 psi), with the flow from the LPOTP then being supplied to the HPOTP. During engine operation, the pressure boost permits the high-pressure oxidizer pump to operate at high speeds without cavitating . The LPOTP, which measures approximately 450 by 450 mm (18 by 18 in),

1853-449: A subsequent competition for award to build the launch vehicles. SpaceX received none of this funding to develop their designs, as both the Falcon 9 and Falcon Heavy had completed development and were already flying. Blue Origin was awarded $ 500 million of phase 1 funding for further development of New Glenn as a potential competitor in future contracts. As of 2019, Blue Origin expected

1962-501: A subsequent flight. A total of 46 reusable RS-25 engines, each costing around US$ 40 million, were flown during the Space Shuttle program, with each new or overhauled engine entering the flight inventory requiring flight qualification on one of the test stands at Stennis Space Center prior to flight. Over the course of the Space Shuttle program, the RS-25 went through a series of upgrades, including combustion chamber changes, improved welds and turbopump changes in an effort to improve

2071-479: A thermal barrier between hot gaseous combustion products and the metallic shell. A TBC applied to the Inconel 718 shell during production could extend engine life and reduce cooling costs. Further, CMCs have been studied as a replacement for Ni-based superalloys and are composed of high-strength fibers (BN, C) continuously dispersed in a SiC matrix. An MCC composed of a CMC, though less studied and farther from fruition than

2180-410: A two-stage hot-gas turbine. It boosts the pressure of the liquid hydrogen from 1.9 to 45 MPa (276 to 6,515 psia), and operates at approximately 35,360 rpm with a power of 71,140  hp (53.05  MW ). The discharge flow from the turbopump is routed to, and through, the main valve and is then split into three flow paths. One path is through the jacket of the main combustion chamber, where the hydrogen

2289-499: A working 350,000 lbf (1,600 kN) concept engine during the year) and Aerojet General's prior experience in developing the 1,500,000 lbf (6,700 kN) M-1 engine , Rocketdyne was forced to put a large amount of private money into the design process to allow the company to catch up to its competitors. By the time the contract was awarded, budgetary pressures meant that the shuttle's design had changed to its final orbiter, external tank, and two boosters configuration, and so

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2398-402: Is 100% open before the engine start. During engine operation, it is 100% open for throttle settings of 100 to 109%. For throttle settings between 65 and 100%, its position ranged from 66.4 to 100%. Each engine is installed with a gimbal bearing , a universal ball and socket joint which is bolted to the launch vehicle by its upper flange and to the engine by its lower flange. It represents

2507-580: Is a super heavy-lift rocket developed and produced by SpaceX. It has been certified for the NSSL program after the STP-2 launch completed on 25 June 2019, as confirmed by the commander of the Air Force Space and Missile Systems Center, Lt. Gen. Thompson. He clarified: "I certified them to compete last year" and "one of the requirements behind certification is to fly three missions." This requirement has been satisfied by

2616-409: Is between the pump section and cavity. Loss of helium pressure in this cavity results in automatic engine shutdown. The low-pressure fuel turbopump (LPFTP) is an axial-flow pump driven by a two-stage turbine powered by gaseous hydrogen. It boosts the pressure of the liquid hydrogen from 30 to 276 psia (0.2 to 1.9 MPa) and supplies it to the high-pressure fuel turbopump (HPFTP). During engine operation,

2725-407: Is connected to the vehicle propellant ducting and supported in a fixed position by being mounted on the launch vehicle's structure. Then, mounted before the HPOTP, is the pogo oscillation suppression system accumulator. For use, it is pre-and post-charged with He and charged with gaseous O 2 from the heat exchanger, and, not having any membrane, it operates by continuously recirculating

2834-404: Is lined with a copper - silver - zirconium alloy called NARloy-Z, developed specifically for the RS-25 in the 1970s. Around 390 channels are machined into the liner wall to carry liquid hydrogen through the liner to provide MCC cooling, as the temperature in the combustion chamber reaches 3300 °C (6000 °F) during flight – higher than the boiling point of iron . An alternative for

2943-419: Is made of titanium alloy. The low-pressure oxygen and low-pressure fuel turbopumps were mounted 180° apart on the orbiter's aft fuselage thrust structure. The lines from the low-pressure turbopumps to the high-pressure turbopumps contain flexible bellows that enable the low-pressure turbopumps to remain stationary while the rest of the engine is gimbaled for thrust vector control, and also to prevent damage to

3052-433: Is tapped off and sent to the oxidizer heat exchanger . The liquid oxygen flows through an anti-flood valve that prevents it from entering the heat exchanger until sufficient heat is present for the heat exchanger to utilize the heat contained in the gases discharged from the HPOTP turbine, converting the liquid oxygen to gas. The gas is sent to a manifold and then routed to pressurize the liquid oxygen tank. Another path enters

3161-476: Is then discharged into the main combustion chamber. A second hydrogen flow path from the main fuel valve is through the engine nozzle (to cool the nozzle). It then joins the third flow path from the chamber coolant valve. This combined flow is then directed to the fuel and oxidizer pre-burners. The HPFTP is approximately 550 by 1,100 mm (22 by 43 in) in size and is attached to the hot-gas manifold by flanges. The oxidizer and fuel pre-burners are welded to

3270-792: Is used for the Atlas V configuration identification. The first digit represents the payload fairing diameter, either 4.2 meters (indicated by a 4) or 5.4 (indicated by a 5) meters. The second digit is for the number of solid rocket boosters (0 to 5) to be used, and the third digit the number of RL-10 engines on the Centaur upper stage (1 or 2). As an example, an Atlas V 551 has a 5.4-meter payload fairing, 5 SRBs, and 1 RL-10. In August 2021, ULA announced that Atlas V would be retired, and all 29 remaining launches had been sold. The last launch for NSSL happened on 30 July 2024. As of July 2024 , fifteen launches remain, all for non-DoD launches. The main features of

3379-418: Is used in-flight to purge the engine and provides pressure for actuating engine valves within the propellant management system and during emergency shutdowns. During entry, on the Space Shuttle, any remaining helium was used to purge the engines during reentry and for repressurization. The history of the RS-25 traces back to the 1960s when NASA 's Marshall Space Flight Center and Rocketdyne were conducting

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3488-518: Is used on the Space Launch System (SLS). Designed and manufactured in the United States by Rocketdyne (later Pratt & Whitney Rocketdyne and Aerojet Rocketdyne ), the RS-25 burns cryogenic (very low temperature) liquid hydrogen and liquid oxygen propellants, with each engine producing 1,859 kN (418,000 lb f ) thrust at liftoff. Although RS-25 heritage traces back to

3597-477: Is used to cool the chamber walls. It is then routed from the main combustion chamber to the LPFTP, where it is used to drive the LPFTP turbine. A small portion of the flow from the LPFTP is then directed to a common manifold from all three engines to form a single path to the liquid hydrogen tank to maintain pressurization. The remaining hydrogen passes between the inner and outer walls of the hot-gas manifold to cool it and

3706-610: The Delta IV based around Common Booster Cores and the Delta Cryogenic Second Stage , while Lockheed Martin developed the Atlas V based around Common Core Boosters and the Centaur upper stage. In 2003, Boeing was found to be in possession of proprietary documents from Lockheed Martin. The USAF moved 7 launches from Delta IV to Atlas V. To end litigation and competition for a limited market, both companies agreed to form

3815-548: The Evolved Expendable Launch Vehicle launch system program, the initial program goal was to make government space launches more affordable and reliable , leading to the development of the Boeing Delta IV and Lockheed Martin Atlas V EELV families. These remained the primary launch vehicles for U.S. military satellites , and were later joined by the Falcon 9 developed by SpaceX . On 1 March 2019,

3924-689: The Falcon Heavy test flight in February 2018, Arabsat-6A in April 2019, and the STP-2 launch in June 2019. Falcon Heavy has been certified for two Phase 1A reference orbits and as of 2019, "it's not certified for all of our most stressing national security space orbits," Thompson said. The USAF is working with SpaceX to mature their Falcon Heavy's design. As of December 2023, it has flown three classified national security flights: USSF-44, USSF-67, and USSF-52. In 2018,

4033-617: The Michoud Assembly Facility ; they will be installed in the Space Station Processing Facility at Kennedy beginning with Artemis III . Once the remaining RS-25Ds are exhausted, they are to be replaced with a cheaper, expendable version designated the RS-25E. In 2023, Aerojet Rocketdyne reported reductions in manufacturing time and labour requirements during manufacturing of new-production RS-25 engines, such as

4142-675: The Space Shuttle Solid Rocket Boosters (SRBs), which committed the shuttle to the launch. At launch, the engines would be operating at 100% RPL, throttling up to 104.5% immediately following liftoff. The engines would maintain this power level until around T+40 seconds, where they would be throttled back to around 70% to reduce aerodynamic loads on the shuttle stack as it passed through the region of maximum dynamic pressure, or max. q . The engines would then be throttled back up until around T+8 minutes, at which point they would be gradually throttled back down to 67% to prevent

4251-782: The United Launch Alliance (ULA) joint venture. Each company has a 50% stake in ULA. Prior to 2012, the USAF was advancing another program, the Reusable Booster System and other follow-on technologies, and up to early 2012 issued contract awards for various aspects of it, before the program was cancelled in October 2012. In December 2012, the DoD announced a re-opening of the EELV-class launch vehicle market to competition while authorizing

4360-401: The 1960s, its concerted development began in the 1970s with the first flight, STS-1 , on April 12, 1981. The RS-25 has undergone upgrades over its operational history to improve the engine's thrust, reliability, safety, and maintenance load. The engine produces a specific impulse ( I sp ) of 452 seconds (4.43 kN-sec/kg) in vacuum, or 366 seconds (3.59 kN-sec/kg) at sea level, has

4469-607: The Ares I and Ares V rockets, the RS-25 was to be replaced with a single J-2X engine for the Ares I second stage and six modified RS-68 engines (which was based on both the SSME and Apollo-era J-2 engine) on the Ares V core stage; this meant that the RS-25 would be retired along with the Shuttle fleet. In 2010, however, NASA was directed to halt the Constellation program, and with it development of

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4578-525: The Ares I and Ares V, instead of focusing on building a new heavy-lift launcher. On 14 September 2011, following the retirement of the Space Shuttle , NASA announced that it would be developing a new launch vehicle, known as the Space Launch System (SLS), to replace the shuttle fleet. The design for the SLS features the RS-25 as part of its core stage , with different versions of the rocket being equipped with between three and five engines. The initial flights of

4687-452: The EELV program in 1994, following many years of government-funded studies into improved systems and architecture. The intent was to replace legacy vehicles, including Delta II , Atlas II , and Titan IV . EELVs were to reduce costs by being based on standardized fairings, liquid core vehicles , upper stages, and solid rocket boosters . A Standard Payload Interface bus was also proposed as a way to save money and improve efficiency. Reducing

4796-468: The Falcon 9 in its Block 5 version include two stages , both powered by LOX and RP-1 , with nine Merlin 1D engines on the first stage and one Merlin 1D Vacuum engine on the second stage. This launcher features a reusable first stage and fairings, which lowers the cost per mission. GPS-IIIA USA-289 was the first NSSL-type B5 Falcon 9 launch. The launch occurred on December 23, 2018. The Falcon Heavy

4905-557: The HG-3 was cancelled as well as the upgraded F-1 engines already being tested. It was the design for the HG-3 that would form the basis for the RS-25. Meanwhile, in 1967, the US Air Force funded a study into advanced rocket propulsion systems for use during Project Isinglass , with Rocketdyne asked to investigate aerospike engines and Pratt & Whitney (P&W) to research more efficient conventional de Laval nozzle -type engines. At

5014-513: The HPOTP and HPFTP turbines depends on the position of the corresponding oxidizer and fuel pre-burner oxidizer valves. These valves are positioned by the engine controller, which uses them to throttle the flow of liquid oxygen to the pre-burners and, thus, control engine thrust. The oxidizer and fuel pre-burner oxidizer valves increase or decrease the liquid oxygen flow, thus increasing or decreasing pre-burner chamber pressure, HPOTP and HPFTP turbine speed, and liquid oxygen and gaseous hydrogen flow into

5123-458: The HPOTP second-stage pre-burner pump to boost the liquid oxygen's pressure from 30 to 51 MPa (4,300 psia to 7,400 psia). It passes through the oxidizer pre-burner oxidizer valve into the oxidizer pre-burner and through the fuel pre-burner oxidizer valve into the fuel pre-burner. The HPOTP measures approximately 600 by 900 mm (24 by 35 in). It is attached by flanges to the hot-gas manifold. The HPOTP turbine and HPOTP pumps are mounted on

5232-526: The MEC operates five hydraulically actuated propellant valves on each engine; the oxidizer pre-burner oxidizer, fuel pre-burner oxidizer, main oxidizer, main fuel, and chamber coolant valves. In an emergency, the valves can be fully closed by using the engine's helium supply system as a backup actuation system. In the Space Shuttle, the main oxidizer and fuel bleed valves were used after shutdown to dump any residual propellant, with residual liquid oxygen venting through

5341-530: The MPS hardware from Space Shuttles Atlantis and Endeavour in their core stages. The SLS's propellants are supplied to the engines from the rocket's core stage, which consists of a modified Space Shuttle external tank with the MPS plumbing and engines at its aft, and an interstage structure at the top. For the first two Artemis missions, the engines are installed on the SLS core stage in Building 103 of

5450-485: The Space Launch System are throttled to 109% power during normal flight, while new RS-25 engines produced for the Space Launch System are to be run at 111% throttle, with 113% power being tested. These increases in throttle level made a significant difference to the thrust produced by the engine: Specifying power levels over 100% may seem nonsensical, but there was a logic behind it. The 100% level does not mean

5559-518: The Space Shuttle program. Subsequent flights will make use of a simplified RS-25E engine called the Production Restart, which is under testing and development. The RS-25 engine consists of pumps, valves, and other components working in concert to produce thrust . Fuel ( liquid hydrogen ) and oxidizer ( liquid oxygen ) from the Space Shuttle's external tank entered the orbiter at the umbilical disconnect valves and from there flowed through

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5668-496: The Space Shuttle which featured two reusable stages, the orbiter and a crewed fly-back booster, and required one engine which would be able to power both vehicles via two different nozzles (12 booster engines with 550,000 lbf (2,400 kN) sea level thrust each and 3 orbiter engines with 632,000 lbf (2,810 kN) vacuum thrust each). Rocketdyne, P&W and Aerojet General were selected to receive funding although, given P&W's already-advanced development (demonstrating

5777-431: The USAF to proceed with a block buy of "up to" 36 boosters from ULA. At the same time, another 14 boosters were to be procured competitively beginning in 2015, with the initial launches to be performed in 2017. The USAF signed a contract at that time with SpaceX for two launches in 2014 and 2015 to serve as proving flights to support the certification process for the Falcon 9 v1.1 and Falcon Heavy . In April 2014, after

5886-585: The USSF selected SpaceX (F9 and FH) and ULA's yet-to-be-certified Vulcan Centaur to supply US military launch requirements in 2022–2027. New Glenn was considered for the first time in NSSL Phase 3 Lane 1 bidding. Delta IV Medium flew with two or four SRBs on a single Common Booster Core . The DCSS had 4 m diameter and 5 m diameter versions, with matching diameter payload fairings. Delta IV CBCs and DCSSs were integrated horizontally before being transported to

5995-428: The application of a TBC, could offer unprecedented levels of engine efficiency. The engine's nozzle is 121 in (3.1 m) long with a diameter of 10.3 inches (0.26 m) at its throat and 90.7 inches (2.30 m) at its exit. The nozzle is a bell-shaped extension bolted to the main combustion chamber, referred to as a de Laval nozzle . The RS-25 nozzle has an unusually large expansion ratio (about 69:1) for

6104-402: The award of two development agreements, the total amount was more than $ 3 billion. Boeing was awarded a contract for 19 out of the 28 launches; Lockheed Martin was awarded a contract for the other 9. Boeing received $ 1.38 billion, and Lockheed Martin received $ 650 million for the launches. Boeing and Lockheed Martin were each awarded US$ 500 million for the final phase of the bid. Boeing developed

6213-463: The cancellation of OmegA. ULA was awarded $ 967 million of phase 1 funding for further development of Vulcan Centaur as a potential competitor in future contracts. On 12 August 2019, ULA submitted Vulcan Centaur for phase 2 of the USAF's launch services competition. As of July 2024, Vulcan Centaur has completed one certification flight launch and another is left be fully certified for national security launches. On 12 August 2019, at least three of

6322-510: The chamber coolant valve. The fuel passing through the MCC cooling system then passes back through the LPFTP turbine before being routed either to the fuel tank pressurization system or to the hot gas manifold cooling system (from where it passes into the MCC). Fuel in the nozzle cooling and chamber coolant valve systems is then sent via pre-burners into the HPFTP turbine and HPOTP before being reunited again in

6431-416: The chamber pressure. At sea level, a nozzle of this ratio would normally undergo flow separation of the jet from the nozzle, which would cause control difficulties and could even mechanically damage the vehicle. However, to aid the engine's operation Rocketdyne engineers varied the angle of the nozzle walls from the theoretical optimum for thrust, reducing it near the exit. This raises the pressure just around

6540-442: The charge gas. A number of baffles of various types are present inside the accumulator to control sloshing and turbulence, which is useful of itself and also to prevent the escape of gas into the low-pressure oxidizer duct to be ingested in the HPOTP. The HPOTP consists of two single-stage centrifugal pumps (the main pump and a pre-burner pump) mounted on a common shaft and driven by a two-stage, hot-gas turbine. The main pump boosts

6649-410: The combustion process is then self-sustaining. The pre-burners produce the fuel-rich hot gases that pass through the turbines to generate the power needed to operate the high-pressure turbopumps. The oxidizer pre-burner's outflow drives a turbine that is connected to the HPOTP and to the oxidizer pre-burner pump. The fuel pre-burner's outflow drives a turbine that is connected to the HPFTP. The speed of

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6758-487: The conclusion of the study, P&W put forward a proposal for a 250,000 lb f engine called the XLR-129 , which used a two-position expanding nozzle to provide increased efficiency over a wide range of altitudes. In January 1969 NASA awarded contracts to General Dynamics, Lockheed, McDonnell Douglas, and North American Rockwell to initiate the early development of the Space Shuttle. As part of these 'Phase A' studies,

6867-434: The construction of RS-25 engines to be used in SLS missions is the use of advanced structural ceramics, such as thermal barrier coatings (TBCs) and ceramic-matrix composites (CMCs). These materials possess significantly lower thermal conductivities than metallic alloys, thus allowing more efficient combustion and reducing the cooling requirements. TBCs are thin ceramic oxide layers deposited on metallic components, acting as

6976-412: The controller; giving redundancy to the system. The failure of controller system A automatically leads to a switch-over to controller system B without impeding operational capabilities; the subsequent failure of controller system B would provide a graceful shutdown of the engine. Within each system (A and B), the two M68000s operate in lock-step , thereby enabling each system to detect failures by comparing

7085-643: The cost of launches and ensuring national access to space were the two main goals of the USAF space launch/EELV program. Some of the reasons why assured access to space is a priority for the United States are stated in National Presidential Directive Number 40, which reads: Access to space through U.S. space transportation capabilities is essential to: The United States, therefore, must maintain robust, responsive, and resilient U.S. space transportation capabilities to assure access to space. Procurement of EELV boosters for military space launch

7194-535: The design, including the HPFTP, HPOTP, valves, nozzle, and fuel pre-burners. The individual engine component tests were followed by the first test of a complete engine (0002) on March 16, 1977, after its final assembly line was established in the main Rocketdyne factory in Canoga Park, Los Angeles . NASA specified that, prior to the Shuttle's first flight, the engines must have undergone at least 65,000 seconds of testing,

7303-468: The engine and residual liquid hydrogen venting through the liquid hydrogen fill and drain valves. After the dump was completed, the valves closed and remained closed for the remainder of the mission. A coolant control valve is mounted on the combustion chamber coolant bypass duct of each engine. The engine controller regulates the amount of gaseous hydrogen allowed to bypass the nozzle coolant loop, thus controlling its temperature. The chamber coolant valve

7412-401: The engine was only required to power the orbiter during ascent. During the year-long 'Phase B' study period, Rocketdyne was able to make use of their experience developing the HG-3 engine to design their SSME proposal, producing a prototype by January 1971. The engine made use of a new Rocketdyne-developed copper - zirconium alloy (called NARloy-Z) and was tested on February 12, 1971, producing

7521-408: The engine's functions (through the use of valves) and monitors its performance. Built by Honeywell Aerospace , each MEC originally comprised two redundant Honeywell HDC-601 computers, later upgraded to a system composed of two doubly redundant Motorola 68000 (M68000) processors (for a total of four M68000s per controller). Having the controller installed on the engine itself greatly simplifies

7630-566: The engine's performance and reliability and so reduce the amount of maintenance required after use. As a result, several versions of the RS-25 were used during the program: The most obvious effects of the upgrades the RS-25 received through the Space Shuttle program were the improvements in engine throttle. Whilst the FMOF engine had a maximum output of 100% RPL, Block II engines could throttle as high as 109% or 111% in an emergency, with usual flight performance being 104.5%. Existing engines used on

7739-426: The engine's thrust vector to be altered, thus steering the vehicle into the correct orientation. The comparatively large gimbal range is necessary to correct for the pitch momentum that occurs due to the constantly shifting center of mass as the vehicle burns fuel in flight and after booster separation. The bearing assembly is approximately 290 by 360 mm (11 by 14 in), has a mass of 105 lb (48 kg), and

7848-415: The engine, the propellants flow through low-pressure fuel and oxidizer turbopumps (LPFTP and LPOTP), and from there into high-pressure turbopumps (HPFTP and HPOTP). From these HPTPs the propellants take different routes through the engine. The oxidizer is split into four separate paths: to the oxidizer heat exchanger , which then splits into the oxidizer tank pressurization and pogo suppression systems; to

7957-418: The four companies submitted their final bids for the launch services competition. SpaceX bid the existing Falcon 9 and Falcon Heavy , while Blue Origin was expected to bid New Glenn, ULA bid Vulcan Centaur, and NGIS's bid status was not reported. Blue Origin also filed a pre-award protest of the request for proposal arguing that the requirements were ambiguous. The US Department of the Air Force announced

8066-428: The hot gas manifold, from where it passes into the MCC injectors. Once in the injectors, the propellants are mixed and injected into the main combustion chamber where they are ignited. The ejection of the burning propellant mixture through the throat and bell of the engine's nozzle creates the thrust. The low-pressure oxidizer turbopump (LPOTP) is an axial-flow pump which operates at approximately 5,150 rpm driven by

8175-462: The hot-gas manifold. The fuel and oxidizer enter the pre-burners and are mixed so that efficient combustion can occur. The augmented spark igniter is a small combination chamber located in the center of the injector of each pre-burner. Two dual-redundant spark igniters are activated by the engine controller and are used during the engine start sequence to initiate combustion in each pre-burner. They are turned off after approximately three seconds because

8284-517: The involved companies selected an upgraded version of the XLR-129, developing 415,000 lbf (1,850 kN), as the baseline engine for their designs. This design can be found on many of the planned Shuttle versions right up to the final decision. However, since NASA was interested in pushing the state of the art in every way they decided to select a much more advanced design in order to "force an advancement of rocket engine technology". They called for

8393-461: The launches over the five-year period. The contract type for the phase 2 contracts is new for NSSL launches as it will be a "firm-fixed-price, indefinite-delivery" type of launch contract. The awards in August 2020 are a major part of "the transition of the national security launch program to take advantage of commercial innovation and private investments in launch vehicles." In 2023, USSF released

8502-772: The launches were contracted, SpaceX sued the United States Air Force, arguing that the RD-180 engines, produced in Russia by the government owned NPO Energomash and used by the Atlas V, violated sanctions against the Russian government. The USAF and SpaceX settled the lawsuit in Jan 2015 by opening up more launches to competitive bidding. The USAF certified the Falcon 9 in May 2015, and in 2016 SpaceX won

8611-451: The launchpad. The Delta IV Medium retired after the 22 August 2019 launch of a GPS-III satellite . The mission used a Delta IV M+(4,2) two SRBs, and a 4 m diameter DCSS and payload fairing, the final use of the 4 m fairing. The Delta IV Heavy launch vehicle used three Common Booster Cores (CBCs) each powered by a Pratt and Whitney Rocketdyne RS-68A engine, a Delta Cryogenic Second Stage 5 m (DCSS) powered by an RL10 , and

8720-441: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=EELV&oldid=1251022777 " Category : Disambiguation pages Hidden categories: Articles containing French-language text Short description is different from Wikidata All article disambiguation pages All disambiguation pages National Security Space Launch Started in 1994 as

8829-399: The liquid oxygen's pressure from 2.9 to 30 MPa (420 to 4,350 psi) while operating at approximately 28,120 rpm, giving a power output of 23,260  hp (17.34  MW ). The HPOTP discharge flow splits into several paths, one of which drives the LPOTP turbine. Another path is to, and through, the main oxidizer valve and enters the main combustion chamber. Another small flow path

8938-425: The low-pressure oxidizer turbopump (LPOTP); to the high-pressure oxidizer pre-burner, from which it is split into the HPFTP turbine and HPOTP before being reunited in the hot gas manifold and sent on to the main combustion chamber (MCC); or directly into the main combustion chamber (MCC) injectors. Meanwhile, fuel flows through the main fuel valve into regenerative cooling systems for the nozzle and MCC, or through

9047-506: The main combustion chamber, which increases or decreases engine thrust. The oxidizer and fuel pre-burner valves operate together to throttle the engine and maintain a constant 6.03:1 propellant mixture ratio. The main oxidizer and main fuel valves control the flow of liquid oxygen and liquid hydrogen into the engine and are controlled by each engine controller. When an engine is operating, the main valves are fully open. The engine's main combustion chamber (MCC) receives fuel-rich hot gas from

9156-502: The maximum physical power level attainable, rather it was a specification decided on during engine development—the expected rated power level. When later studies indicated the engine could operate safely at levels above 100%, these higher levels became standard. Maintaining the original relationship of power level to physical thrust helped reduce confusion, as it created an unvarying fixed relationship so that test data (or operational data from past or future missions) can be easily compared. If

9265-481: The new launch vehicle are making use of previously flown Block II RS-25D engines, with NASA keeping such engines in a "purged safe" environment at Stennis Space Center, "along with all of the ground systems required to maintain them." For Artemis I, the RS-25D units with serial numbers E2045, E2056, E2058, and E2060 from all three orbiters were used. They were installed on the core stage by November 6, 2019. For Artemis II,

9374-515: The next generation NSSL launch vehicles until at least 2030. See EELV_Secondary_Payload_Adapter (ESPA rings with radial ports) Since 2019 there have been four vehicles certified by the Department of Defense to conduct NSSL launches: Atlas V, Delta IV Heavy, Falcon 9 and Falcon Heavy. Delta IV Medium was retired in August 2019 and Delta IV Heavy retired in April 2024. After a two-year solicitation and competition process in 2018–2020, in August 2020

9483-444: The nozzle is the engine attach point to the orbiter-supplied heat shield. Thermal protection is necessary because of the exposure portions of the nozzles experience during the launch, ascent, on-orbit and entry phases of a mission. The insulation consists of four layers of metallic batting covered with a metallic foil and screening. Each engine is equipped with a main engine controller (MEC), an integrated computer which controls all of

9592-472: The orbiter being transferred to the Vehicle Assembly Building . If necessary the engines could be changed on the pad. The engines, drawing propellant from the Space Shuttle external tank (ET) via the orbiter's main propulsion system (MPS), were ignited at T−6.6 seconds prior to liftoff (with each ignition staggered by 120  ms ), which allowed their performance to be checked prior to ignition of

9701-455: The orbiter's main propulsion system (MPS) feed lines; whereas in the Space Launch System (SLS), fuel and oxidizer from the rocket's core stage flow directly into the MPS lines. Once in the MPS lines, the fuel and oxidizer each branch out into separate paths to each engine (three on the Space Shuttle, four on the SLS). In each branch, pre-valves then allow the propellants to enter the engine. Once in

9810-561: The orbiter. The engines, which were of the first manned orbital flight (FMOF) configuration and certified for operation at 100% rated power level (RPL), were operated in a twenty-second flight readiness firing on February 20, 1981, and, after inspection, declared ready for flight. Each Space Shuttle had three RS-25 engines, installed in the aft structure of the Space Shuttle orbiter in the Orbiter Processing Facility prior to

9919-491: The planned configurations of the Constellation program 's Ares V cargo-launch vehicle and Ares I crew-launch vehicle rockets, which had been planned to use the RS-25 in their first and second stages respectively. While these configurations had initially seemed worthwhile, as they would use then-current technology following the shuttle's retirement in 2010, the plan had several drawbacks: Following several design changes to

10028-400: The power level was increased, and that new value was said to be 100%, then all previous data and documentation would either require changing or cross-checking against what physical thrust corresponded to 100% power level on that date. Engine power level affects engine reliability, with studies indicating the probability of an engine failure increasing rapidly with power levels over 104.5%, which

10137-411: The pressure boost provided by the LPFTP permits the HPFTP to operate at high speeds without cavitating. The LPFTP operates at around 16,185 rpm , and is approximately 450 by 600 mm (18 by 24 in) in size. It is connected to the vehicle propellant ducting and is supported in a fixed position by being mounted to the launch vehicle's structure. The HPFTP is a three-stage centrifugal pump driven by

10246-517: The program name was changed from EELV to National Security Space Launch (NSSL) to better reflect the growing commercial launch market and the changing nature of launch contracts, including the potential for reusable launch vehicles. The NSSL program launches the nation's most valuable military satellites; contracts to launch lower value payloads, such as those of the Space Test Program , are awarded using different methodologies. The USAF began

10355-407: The pumps when loads were applied to them. The liquid-hydrogen line from the LPFTP to the HPFTP is insulated to prevent the formation of liquid air. In addition to fuel and oxidizer systems, the launch vehicle's main propulsion system is also equipped with a helium system consisting of ten storage tanks in addition to various regulators, check valves, distribution lines, and control valves. The system

10464-440: The results of the approximately US$ 3.5 billion National Security Space Launch Phase 2 Launch Service Procurement on 7 August 2020. SpaceX and ULA were the two vendors selected via the competition to supply launches to the US military in the 2022–2026 timeframe. The US Space Force (USSF) plans 30–34 launches during these five fiscal years. ULA is expected to handle 60 percent of the launches while SpaceX will handle 40 percent of

10573-405: The rim to an absolute pressure between 4.6 and 5.7 psi (32 and 39 kPa), and prevents flow separation. The inner part of the flow is at much lower pressure, around 2 psi (14 kPa) or less. The inner surface of each nozzle is cooled by liquid hydrogen flowing through brazed stainless steel tube wall coolant passages. On the Space Shuttle, a support ring welded to the forward end of

10682-406: The seafloor, were delivered to Honeywell Aerospace for examination and analysis. One controller was broken open on one side, and both were severely corroded and damaged by marine life. Both units were disassembled and the memory units flushed with deionized water . After they were dried and vacuum baked , data from these units was retrieved for forensic examination. To control the engine's output,

10791-503: The signal levels on the buses of the two M68000 processors within that system. If differences are encountered between the two buses, then an interrupt is generated and control turned over to the other system. Because of subtle differences between M68000s from Motorola and the second source manufacturer TRW , each system uses M68000s from the same manufacturer (for instance system A would have two Motorola CPUs while system B would have two CPUs manufactured by TRW). Memory for block I controllers

10900-521: The spacecraft ascent, with total thrust increased by two solid rocket boosters and the orbiter's two AJ10 orbital maneuvering system engines. Following each flight, the RS-25 engines were removed from the orbiter, inspected, refurbished, and then reused on another mission. Four RS-25 engines are installed on each Space Launch System, housed in the engine section at the base of the core stage, and expended after use. The first four Space Launch System flights use modernized and refurbished engines built for

11009-526: The stack exceeding 3  g of acceleration as it became progressively lighter due to propellant consumption. The engines were then shut down, a procedure known as main engine cutoff (MECO), at around T+8.5 minutes. After each flight the engines would be removed from the orbiter and transferred to the Space Shuttle Main Engine Processing Facility (SSMEPF), where they would be inspected and refurbished in preparation for reuse on

11118-402: The thrust interface between the engine and the launch vehicle, supporting 7,480 lb (3,390 kg) of engine weight and withstanding over 500,000 lbf (2,200,000 N) of thrust. As well as providing a means to attach the engine to the launch vehicle, the gimbal bearing allows the engine to be pivoted (or "gimballed") around two axes of freedom with a range of ±10.5°. This motion allows

11227-506: The two providers of Phase 2. Proposals were due December 15, 2023 and awards are expected in mid to late 2024. Phase 3 Lane 1 awardees were SpaceX, Blue Origin and ULA. The vehicles being: Falcon 9 , New Glenn and Vulcan Centaur , respectively. RS-25 The RS-25 , also known as the Space Shuttle Main Engine ( SSME ), is a liquid-fuel cryogenic rocket engine that was used on NASA 's Space Shuttle and

11336-604: The units with serial numbers E2047, E2059, E2062, and E2063 will be used. They were installed on the core stage by September 25, 2023. In addition to the RS-25Ds, the SLS program makes use of the Main Propulsion Systems (MPS, the "plumbing" feeding the engines) from the three remaining shuttle orbiters for testing purposes (having been removed as part of the orbiters' decommissioning), with the first two launches ( Artemis I and Artemis II ) originally predicted to make use of

11445-431: The wiring between the engine and the launch vehicle, because all the sensors and actuators are connected directly to only the controller, each MEC then being connected to the orbiter's general purpose computers (GPCs) or the SLS's avionics suite via its own engine interface unit (EIU). Using a dedicated system also simplifies the software and thus improves its reliability. Two independent dual-CPU computers, A and B, form

11554-402: Was a rocket design with two main solid stages, a cryogenic upper stage, and the possibility of additional solid-rocket strap-on boosters. As of 2019, the first flight has been stated by NGIS to be expected in 2021. In the event, no phase 2 funding from the US government was forthcoming after August 2020 when ULA Vulcan and SpaceX were selected by the Air Force. In 2020, Northrop Grumman announced

11663-499: Was of the plated-wire type, which functions in a manner similar to magnetic core memory and retains data even after power is turned off. Block II controllers used conventional CMOS static RAM . The controllers were designed to be tough enough to survive the forces of launch and proved to be extremely resilient to damage. During the investigation of the Challenger accident the two MECs (from engines 2020 and 2021), recovered from

11772-473: Was to evolve to more closely match commercial practice. The initial bids came from four major defense contractors: Lockheed Martin , Boeing , McDonnell Douglas , and Alliant Techsystems . Each of the bids included a variety of concepts. Boeing initially proposed using the RS-25 Space Shuttle main engine. In October 1998 two initial launch services contracts (known as Buy 1) were awarded. Along with

11881-505: Was why power levels above 104.5% were retained for contingency use only. During the course of the Space Shuttle program, a total of 46 RS-25 engines were used (with one extra RS-25D being built but never used). During the 135 missions, for a total of 405 individual engine-missions, Pratt & Whitney Rocketdyne reports a 99.95% reliability rate, with the only in-flight SSME failure occurring during Space Shuttle Challenger 's STS-51-F mission. The engines, however, did suffer from

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