Delta IV

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Delta_IV

 

Delta IV (Delta 9000)

Delta IV Medium launch carrying DSCS III-B6
Function	Orbital launch vehicle
Manufacturer	United Launch Alliance
Country of origin	United States
Cost per launch	US$164+ million
Size
Height	63–72 m (207–236 ft)
Diameter	5 m (16 ft)
Mass	249,500–733,400 kg (550,100–1,616,900 lb)
Stages	2
Capacity
Payload to LEO	11,470–28,790 kg (25,290–63,470 lb)
Payload to GTO	4,440–14,220 kg (9,790–31,350 lb)
Associated rockets
Family	Delta (rocket family)
Comparable	Atlas V Falcon 9 H-IIA Long March 3B Proton-M
Launch history
Status	Delta IV Heavy is active; Delta IV Medium, M+(4,2), M+(5,2), and M+(5,4) retired.
Launch sites	SLC-37B, Cape Canaveral SLC-6, Vandenberg AFB
Total launches	40 Medium: 3 M+ (4,2): 15 M+ (5,2): 3 M+ (5,4): 8 Heavy: 11
Successes	39 Medium: 3 M+ (4,2): 15 M+ (5,2): 3 M+ (5,4): 8 Heavy: 10
Partial failures	1 (Heavy)
First flight	Medium/M+: 20 November 2002 (Eutelsat W5) Heavy: 21 December 2004 (USA-181)
Last flight	Medium/M+: 22 August 2019 (USA-293/GPS III-2) Heavy: 19 January 2019 (NROL-71)
Notable payloads	GOES GPS Block IIF NRO classified payloads WGS Exploration Flight Test 1 Parker Solar Probe
Boosters (Medium+) – GEM 60
No. boosters	Medium+ (4,2), Medium+ (5,2): 2 Medium+ (5,4): 4
Gross mass	33,638 kg (74,158 lb)
Thrust	826.6 kN (185,800 lbf)
Specific impulse	245 s (2.40 km/s) (sea level)
Burn time	91 seconds
Fuel	HTPB / Aluminum
Boosters (Heavy) – Common Booster Core (CBC)
No. boosters	2
Gross mass	226,400 kg (499,100 lb)
Engines	1 RS-68A
Thrust	3,140 kN (705,000 lbf) (sea level)
Specific impulse	Sea level: 360 s (3.5 km/s) Vacuum: 412 s (4.04 km/s)
Burn time	242 seconds[2]
Fuel	LH2 / LOX
First stage – CBC
Gross mass	226,400 kg (499,100 lb)
Engines	1 RS-68A
Thrust	3,140 kN (705,000 lbf) (sea level)
Specific impulse	Sea level: 360 s (3.5 km/s) Vacuum: 412 s (4.04 km/s)
Burn time	245 seconds (328 seconds in Heavy configuration)
Fuel	LH2 / LOX
Second stage – Delta Cryogenic Second Stage (DCSS)
Gross mass	4-m: 24,170 kg (53,290 lb) 5-m: 30,700 kg (67,700 lb)
Engines	1 RL10-B-2
Thrust	110 kN (25,000 lbf)
Specific impulse	462 s (4.53 km/s)
Burn time	850-1,125 seconds
Fuel	LH2 / LOX

Delta IV is a group of five expendable launch systems in the Delta rocket family introduced in the early 2000s. Originally designed by Boeing's Defense, Space & Security division for the Evolved Expendable Launch Vehicle (EELV) program, the Delta IV became a United Launch Alliance (ULA) product in 2006. The Delta IV was and is primarily a launch vehicle for United States Air Force military payloads, but has also been used to launch a number of U.S. government non-military payloads and a single commercial satellite.

The Delta IV originally had two main versions which allowed the family to cover a range of payload sizes and masses: the retired Medium (which had four configurations) and Heavy. As of 2019, only the Heavy remains active, with payloads that would previously fly on Medium moving to either the existing Atlas V or the forthcoming Vulcan. Retirement of the Delta IV is anticipated in 2024.

Delta IV vehicles are built in the ULA facility in Decatur, Alabama. Final assembly is completed at the launch site by ULA: at the Horizontal Integration Facility for launches from SLC-37B pad at Cape Canaveral and in a similar facility for launches from SLC-6 pad at Vandenberg Air Force Base.

History

The latest evolutionary development of the Delta rocket family, Delta IV was introduced to meet the requirements of the United States Air Force's (USAF's) Evolved Expendable Launch Vehicle (EELV, now national security space launch/NSSL) program. While the Delta IV retains the name of the Delta family of rockets, major changes were incorporated. Perhaps the most significant change was the switch from kerosene to liquid hydrogen fuel, with new tankage and a new engine required.

During the Delta IV's development, a Small variant was considered. This would have featured the Delta II second stage, an optional Thiokol Star 48B third stage, and the Delta II payload fairing, all atop a single Common Booster Core (CBC). The Small variant was dropped by 1999.

In 2002, the Delta IV was first launched, with the RS-68 becoming the first large liquid-propellant rocket engine designed in the U.S. since the Space Shuttle main engine (SSME) in the 1970s. The primary goal for the RS-68 was to reduce cost versus the SSME. Some sacrifice in chamber pressure and specific impulse was made, hurting efficiency; however, development time, part count, total cost, and assembly labor were reduced to a fraction of the SSME, despite the RS-68's significantly larger size.

The L3 Technologies Redundant Inertial Flight Control Assembly (RIFCA) guidance system originally used on the Delta IV was common to that carried on the Delta II, although the software was different because of the differences between the Delta II and Delta IV. The RIFCA featured six ring laser gyroscopes and accelerometers each, to provide a higher degree of reliability.

Boeing initially intended to market Delta IV commercial launch services. However, the Delta IV entered the space launch market when global capacity was already much higher than demand. Furthermore, as an unproven design it had difficulty finding a market in commercial launches, and Delta IV launch costs are higher than comparable vehicles of the same era. In 2003, Boeing pulled the Delta IV from the commercial market, citing low demand and high costs. In 2005, Boeing stated that it sought to return the Delta IV to commercial service.

As of 2009, the USAF funded Delta IV EELV engineering, integration, and infrastructure work through contracts with Boeing Launch Services (BLS). On August 8, 2008, the USAF Space and Missile Systems Center increased the "cost plus award fee" contract with BLS for $1.656 billion to extend the period of performance through the end of FY09. In addition a $557.1 million option was added to cover FY10. However, the Delta IV series was at that time launched by the United Launch Alliance (ULA), a joint venture between Boeing and Lockheed Martin.

In February 2010, naturalized citizen Dongfan Chung, an engineer working with Boeing, was the first person convicted under the Economic Espionage Act of 1996. Chung passed on classified information on designs including the Delta IV rocket and was sentenced to 15 years.

In March 2015, ULA announced plans to phase out the Delta IV Medium by 2018. The Delta IV will be replaced by the Atlas V in the near term and Vulcan in the far term. The Delta IV Medium was actually retired on 22 August 2019. 

With the exception of the first launch, which carried the Eutelsat W5 commercial communications satellite, all Delta IV launches have been paid for by the US government. In 2015, ULA stated that a Delta IV Heavy is sold for nearly $400 million.

RS-68A booster engine upgrade

The possibility of a higher performance Delta IV was first proposed in a 2006 RAND Corporation study of national security launch requirements out to 2020. A single National Reconnaissance Office (NRO) payload required an increase in the lift capability of the Delta IV Heavy. Lift capacity was increased by developing the higher-performance RS-68A engine, which first flew on June 29, 2012. ULA phased out the baseline RS-68 engine with the launch of Delta flight 371 on March 25, 2015. All following launches have used the RS-68A, and the engine's higher thrust allowed the use of a single standardized CBC design for all Delta IV Medium and M+ versions. This upgrade reduced cost and increased flexibility, since any standardized CBC could be configured for zero, two, or four solid boosters. However, the new CBC led to a slight performance loss for most medium configurations. The Delta IV Heavy still requires non-standard CBCs for the core and boosters.

Payload capacities after RS-68A upgrade

 

Version	Fairing	CBCs	SRBs	Payload to LEO 407 km x 51.6°	Payload to GTO 1800 m/s residual	Launches to date
Medium	4 m	1	0	8,510 kg	4,440 kg	0
M+(4,2)	4 m	1	2	12,000 kg	6,390 kg	2
M+(5,2)	5 m	1	2	10,220 kg	5,490 kg	2
M+(5,4)	5 m	1	4	12,820 kg	7,300 kg	4
Heavy	5 m	3	0	25,980 kg	14,220 kg	4

Payload capacities with original RS-68

 

Version	Fairing	CBCs	SRBs	Payload to LEO 407 km x 51.6°	Payload to GTO 1800 m/s residual	Launches to date
Medium	4 m	1	0	8,800 kg	4,540 kg	3
M+(4,2)	4 m	1	2	11,920 kg	6,270 kg	13
M+(5,2)	5 m	1	2	10,580 kg	5,430 kg	1
M+(5,4)	5 m	1	4	13,450 kg	7,430 kg	4
Heavy	5 m	3	0	22,980 kg	13,400 kg	7

Proposed upgrades that were not implemented

Possible future upgrades for the Delta IV included adding extra strap-on solid motors, higher-thrust main engines, lighter materials, higher-thrust second stages, more (up to six) strap-on CBCs, and a cryogenic propellant cross feed from strap on boosters to the common core.

At one point NASA planned to use Delta IV or Atlas V to launch the proposed Orbital Space Plane, which eventually became the Crew Exploration Vehicle and then the Orion. Orion was intended to fly on the Ares I launch vehicle, then the Space Launch System after Ares I was cancelled.

In 2009 The Aerospace Corporation reported on NASA results of a study to determine the feasibility of modifying Delta IV to be human-rated for use in NASA human spaceflight missions. According to Aviation Week the study, "found that a Delta IV heavy [...] could meet NASA's requirements for getting humans to low Earth orbit."

A proposed upgrade to the Delta IV family was the addition of extra solid motors. The Medium+(4,4) would have used existing mount points to pair the four GEM-60s of the M+(5,4) with the upper stage and fairing of the (4,2). An M+(4,4) would have had a GTO payload of 7,500 kg (16,600 lb), a LEO payload of 14,800 kg (32,700 lb), and could have been available within 36 months of the first order. It was also considered to add extra GEM-60s to the M+(5,4), which would have required adding extra attachment points, structural changes to cope with the different flight loads, and launch pad and infrastructure changes. The Medium+(5,6) and (5,8) would have flown with six and eight SRBs respectively, for a maximum of up to 9,200 kg/20,200 lb to GTO with the M+(5,8). The Medium+(5,6) and (5,8) could have been available within 48 months of the first order.

Planned successor

The Vulcan rocket is planned to replace the Atlas V and Delta IV rockets. Vulcan is projected to enter service by 2021, using the Blue Origin BE-4 methane-fueled rocket engine. The Delta IV Heavy and Atlas V are expected to stay in service for a few years after Vulcan's inaugural launch, and the Heavy is expected to be discontinued by 2024.

Vehicle description

Delta IV evolution

 

Delta IV Medium

The Delta IV Medium was available in four configurations: Medium, Medium+ (4,2), Medium+ (5,2), and Medium+ (5,4). 

The Delta IV Medium (Delta 9040) was the most basic Delta IV. It featured a single CBC and a modified Delta III second stage, with 4-meter liquid hydrogen and liquid oxygen tanks and a 4-meter payload fairing. The Delta IV Medium was capable of launching 4,200 kg to geosynchronous transfer orbit (GTO). From Cape Canaveral, GTO is 1804 m/s away from GEO. The mass of fairing and payload attach fittings have been subtracted from the gross performance. It flew last time on 22 August 2019.

The Delta IV Medium+ (4,2) (Delta 9240) had the same CBC and DCSS as the Medium, but with the addition of two Orbital ATK-built 1.5-m (60-in) diameter solid rocket booster Graphite-Epoxy Motors (GEM-60s) strap-on boosters to increase payload capacity to 6,150 kg to GTO.

The Delta IV Medium+ (5,2) (Delta 9250) was similar to the Medium+ (4,2), but had a 5-m–diameter DCSS and payload fairing for larger payloads. Because of the extra weight of the larger payload fairing and second stage, the Medium+ (5,2) could launch 5,072 kg to GTO.

The Delta IV Medium+ (5,4) (Delta 9450) was similar to the Medium+ (5,2), but used four GEM-60s instead of two, enabling it to lift 6,882 kg to GTO.

To encapsulate the satellite payload, a variety of different payload fairings were available. A stretched Delta III 4 meter diameter composite payload fairing was used on 4 meter Medium versions, while an enlarged, 5 meter diameter composite fairing was used on 5 meter Medium versions.

Delta IV Heavy

Delta IV Heavy launching

The Delta IV Heavy (Delta 9250H) combines a 5-meter (16 ft) diameter DCSS and payload fairing with two additional CBCs. These are strap-on boosters which are separated earlier in the flight than the center CBC. As of 2007, a longer 5 meter diameter composite fairing was standard on the Delta IV Heavy, with an aluminum isogrid fairing also available. The aluminum trisector (three-part) fairing was built by Boeing and derived from a Titan IV fairing. The trisector fairing was first used on the DSP-23 flight. The Delta IV with the extended fairing is over 62 m (205 ft) tall. 

Common Booster Core

Each Delta IV consists of at least one Common Booster Core (CBC). Each CBC is powered by one Aerojet Rocketdyne RS-68 engine, which burns liquid hydrogen and liquid oxygen.

On flights of the Medium, the RS-68 ran at 102% rated thrust for the first few minutes of flight, and then throttled down to 58% rated thrust before main engine cutoff. On the Heavy, the main CBC's engine throttles down to 58% rated thrust around 50 seconds after liftoff, while the strap-on CBCs remain at 102%. This conserves propellant and allows the main CBC to burn after booster separation. After the strap-on CBCs separate, the main CBC's engine throttles back up to 102% before throttling back down to 58% prior to main engine cutoff.

The RS-68 engine is mounted to the lower thrust structure of the CBC by a four-legged (quadrapod) thrust frame and enclosed in a protective composite conical thermal shield. Above the thrust structure is an aluminum isogrid (a grid pattern machined out of the inside of the tank to reduce weight) liquid hydrogen tank, followed by a composite cylinder called the centerbody, an aluminum isogrid liquid oxygen tank, and a forward skirt. Along the back of the CBC is a cable tunnel to hold electrical and signal lines, and a feedline to carry the liquid oxygen to the RS-68 from the tank. The CBC is of a constant, 5-meter (16.4 ft) diameter.

Delta Cryogenic Second Stage

Delta IV 4-Meter Second Stage

The upper stage of the Delta IV is the Delta Cryogenic Second Stage (DCSS). The DCSS is based on the Delta III upper stage but has increased propellant capacity. Two versions have been produced: a 4-meter (13.1 ft) diameter DCSS that was retired with the Delta IV Medium and a 5-meter diameter DCSS that remains in service with the Delta IV Heavy. The 4 m diameter version lengthened both Delta III propellant tanks, while the 5-meter version has an extended diameter liquid hydrogen tank and a further lengthened liquid oxygen tank. Regardless of the diameter, each DCSS is powered by one RL10B2 engine, with an extendable carbon-carbon nozzle to improve specific impulse. Two different interstages are used to mate the first stage and DCSS. A tapering interstage that narrowed down from 5 m to 4 m diameter was used to mate the 4 m DCSS to the CBC, while a cylindrical interstage is used to mate the 5 m DCSS. Both interstages were built from composites and enclosed the liquid oxygen tank, with the larger liquid hydrogen tank making up part of the vehicle's outer mold line.

Launch sites

First Delta IV Heavy with three CBCs prior to launch

 

Delta IV launches occur from either of two rocket launch complexes. Launches on the East coast of the United States use Space Launch Complex 37 (SLC-37) at the Cape Canaveral Air Force Station. On the West coast, polar-orbit and high-inclination launches use Vandenberg Air Force Base's Space Launch Complex 6 (SLC-6).

Launch facilities at both sites are similar. A Horizontal Integration Facility (HIF) is situated some distance from the pad. Delta IV CBCs and second stages to be mated and tested in the HIF before they are moved to the pad. The partial horizontal rocket assembly of the Delta IV is somewhat similar to the Soyuz launch vehicle, which is completely assembled horizontally. The Space Shuttles, the past Saturn launch vehicles, and the upcoming Space Launch System are assembled and rolled out to the launch pad entirely vertically.

Movement of the Delta IVs among the various facilities at the pad is facilitated by rubber-tired Elevating Platform Transporters (EPTs) and various transport jigs. Diesel engine EPTs are used for moving the vehicles from the HIF to the pad, while electric EPTs are used in the HIF, where precision of movement is important.

The basic launchpad structure includes a flame trench to direct the engine plume away from the rocket, lightning protection, and propellant storage. In the case of Delta IV, the vehicle is completed on the launch pad inside a building. This Mobile Service Tower (MST) provides service access to the rocket and protection from the weather and is rolled away from the rocket on launch day. A crane at the top of the MST lifts the encapsulated payload to the vehicle and also attached the GEM-60 solid motors for Delta IV Medium launches. The MST is rolled away from the rocket several hours before launch. At Vandenberg, the launch pad also has a Mobile Assembly Shelter (MAS), which completely encloses the vehicle; at CCAFS, the vehicle is partly exposed near its bottom.

Beside the vehicle is a Fixed Umbilical Tower (FUT), which has two (VAFB) or three (CCAFS) swing arms. These arms carry telemetry signals, electrical power, hydraulic fluid, environmental control air flow, and other support functions to the vehicle through umbilical lines. The swing arms retract at T-0 seconds once the vehicle is committed to launch.

Under the vehicle is a Launch Table, with six Tail Service Masts (TSMs), two for each CBC. The Launch Table supports the vehicle on the pad, and the TSMs provide further support and fueling functions for the CBCs. The vehicle is mounted to the Launch Table by a Launch Mate Unit (LMU), which is attached to the vehicle by bolts that sever at launch. Behind the Launch Table is a Fixed Pad Erector (FPE), which uses two long-stroke hydraulic pistons to raise the vehicle to the vertical position after being rolled to the pad from the Horizontal Integration Facility (HIF). Beneath the Launch Table is a flame duct, which deflects the rocket's exhaust away from the rocket or facilities.

Vehicle processing

Delta IV CBCs and DCSSs are assembled at ULA's factory in Decatur, Alabama. They are then loaded onto the M/V Delta Mariner, a roll-on/roll-off cargo vessel, and shipped to either launch pad. There, they are offloaded and rolled into a Horizontal Integration Facility (HIF). For Delta IV Medium launches, the CBC and DCSS were mated in the HIF. For Delta IV Heavy launches, the port and starboard strap-on CBCs are also mated in the HIF.

Various tests are performed, and then the vehicle is rolled horizontally to the pad, where the Fixed Pad Erector (FPE) is used to raise the vehicle to the vertical position. At this time, the GEM-60 solid motors, if any are required, are rolled to the pad and attached to the vehicle. After further testing, the payload (which has already been enclosed in its fairing) is transported to the pad, hoisted into the MST by a crane, and attached to the vehicle. Finally, on launch day, the MST is rolled away from the vehicle, and the vehicle is ready for launch.

Notable launches

GOES-N launch on a Medium+ (4,2)

 

A unique aerial view of NROL-22 launch from SLC-6

 

The first payload launched with a Delta IV was the Eutelsat W5 communications satellite. A Medium+ (4,2) from Cape Canaveral carried the communications satellite into geostationary transfer orbit (GTO) on 20 November 2002.

Heavy Demo was the first launch of the Delta IV Heavy in December 2004 after significant delays due to bad weather. Due to cavitation in the propellant lines, sensors on all three CBCs registered depletion of propellant. The strap-on CBCs and then core CBC engines shut down prematurely, even though sufficient propellant remained to continue the burn as scheduled. The second stage attempted to compensate for the shutdown and burned until it ran out of propellant. This flight was a test launch carrying a payload of:

• DemoSat – 6020 kg; an aluminum cylinder filled with 60 brass rods – planned to be carried to GEO; however due to the sensor faults, the satellite did not reach this orbit.
• NanoSat-2, carried to low Earth orbit (LEO) – a set of two very small satellites of 24 and 21 kg, nicknamed Sparky and Ralphie – planned to orbit for one day. Given the under-burn, the two most likely did not reach a stable orbit.

NROL-22 was the first Delta IV launched from SLC-6 at Vandenberg Air Force Base (VAFB). It was launched aboard a Medium+ (4,2) in June 2006 carrying a classified satellite for the U.S. National Reconnaissance Office (NRO).

DSP-23 was the first launch of a valuable payload aboard a Delta IV Heavy. This was also the first Delta IV launch contracted by the United Launch Alliance, a joint venture between Boeing and Lockheed Martin. The main payload was the 23rd and final Defense Support Program missile-warning satellite, DSP-23. Launch from Cape Canaveral occurred on November 10, 2007.

NROL-26 was the first Delta IV Heavy EELV launch for the NRO. USA 202, a classified reconnaissance satellite, lifted off 18 January 2009.

NROL-32 was a Delta IV Heavy launch, carrying a satellite for NRO. The payload is speculated to be the largest satellite sent into space. After a delay from 19 October 2010, the rocket lifted off on 21 November 2010.

NROL-49 lifted off from Vandenberg AFB on January 20, 2011. It was the first Delta IV Heavy mission to be launched out of Vandenberg. This mission was for the NRO and its details are classified.

On October 4, 2012, a Delta IV M+ (4,2) experienced an anomaly in the upper stage's RL10-B-2 engine which resulted in lower than expected thrust. While the vehicle had sufficient fuel margins to successfully place the payload, a GPS Block IIF satellite, into its targeted orbit, investigation into the glitch delayed subsequent Delta IV launches and the next Atlas V launch (AV-034) due to commonality between the engines used on both vehicles' upper stages. By December 2012, ULA had determined the cause of the anomaly to be a fuel leak, and Delta IV launches resumed in May 2013. After two more successful launches, further investigation led to the delay of Delta flight 365 with the GPS IIF-5 satellite. Originally scheduled to launch in October 2013, the vehicle lifted off on February 21, 2014.

A Delta IV Heavy launched the Orion spacecraft on an uncrewed test flight, EFT-1, on December 5, 2014. The launch was originally planned for December 4, but high winds and valve issues caused the launch to be rescheduled for December 5.

The second GPS Block III satellite was launched with the final Delta IV Medium in the +(4,2) configuration on 22 August 2019.

Raptor (rocket engine family)

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Raptor_(rocket_engine_family)

 

Raptor

First test firing of a Raptor development engine on 25 September 2016 in McGregor, Texas.
Country of origin	United States
Manufacturer	SpaceX
Application	Multistage propulsion
Status	Ready
Liquid-fuel engine
Propellant	Liquid oxygen / liquid methane
Mixture ratio	3.8
Cycle	Full-flow staged combustion
Pumps	2 × multi-stage
Configuration
Chamber	1
Nozzle ratio	40
Performance
Thrust	2,400 kN (550,000 lbf)
Thrust-to-weight ratio	>170 (goal)
Chamber pressure	300 bar (30 MPa; 4,400 psi),  anticipated value
Isp (vac.)	380 s (3,700 m/s) (goal)
Isp (SL)	330 s (3,200 m/s)
Dimensions
Length	3.1 m (10 ft)
Diameter	1.3 m (4 ft 3 in)
Dry weight	1,500 kg (3,300 lb) (goal)
Used in
Starship, Super Heavy

Raptor is a full-flow, staged combustion, methane-fueled rocket engine manufactured by SpaceX. The engine is powered by cryogenic liquid methane and liquid oxygen (LOX), rather than the RP-1 kerosene and LOX used in SpaceX's prior Merlin and Kestrel rocket engine families. The earliest concepts for Raptor considered liquid hydrogen (LH
2) as fuel rather than methane. The Raptor engine has about two times the thrust of the Merlin 1D engine that powers the current Falcon 9 launch vehicle.

Raptor will be used in both stages of the two-stage-to-orbit, super heavy-lift launch vehicle Starship.

The Raptor engine is a highly reusable methalox staged-combustion engine that will power the next generation of SpaceX launch vehicles designed to replace all existing SpaceX vehicles, including the Falcon 9 and Falcon Heavy launch vehicles and the Dragon spacecraft. Raptor engines are expected to be used in various applications including existing Earth-orbit satellite delivery market, the exploration and colonization of Mars.

Raptor engines began flight testing on the Starship prototype rockets in July 2019 and became the first full-flow staged combustion rocket engine ever flown.

Description

Raptor engine combustion scheme

 

Full-flow staged combustion rocket engine

 

The Raptor engine is powered by subcooled liquid methane and subcooled liquid oxygen using a more efficient staged combustion cycle, a departure from the simpler 'open cycle' gas generator system and lox/kerosene propellants that current Merlin engines use. The Space Shuttle Main Engines, with hydrolox propellant) also used a staged combustion process, as do several Russian rocket engines including the RD-180 and the 25.74 MPa (3,733 psi) chamber pressure RD-191. The stated design size for the Raptor engine varied widely during 2012–2017 as detailed design continued, from a high target of 8,200 kN (1,800,000 lbf) of vacuum thrust to a more recent, much lower target of 1,900 kN (430,000 lbf). In its 2017 iteration, the operational engine is expected to have a vacuum I_sp of 375 s (3,680 m/s) and a sea-level I_sp of 300 s (2,900 m/s).

The Raptor engine is designed for the use of deep cryogenic methalox propellants—fluids cooled to near their freezing points, rather than nearer their boiling points which is more typical for cryogenic rocket engines. The use of subcooled propellants increases propellant density to allow more propellant mass in tanks; the engine performance is also improved with sub cooled propellants. Specific impulse is increased, and the risk of cavitation at inputs to the turbopumps is reduced due to the higher mass flow rate per unit power generated. Engine ignition for all Raptor engines, both on the pad and in the air, will be by spark ignition, which will eliminate the pyrophoric mixture of triethylaluminum-triethylborane (TEA-TEB) used for engine ignition on the Falcon 9 and Falcon Heavy.

Raptor has been claimed to be able to deliver "long life ... and more benign turbine environments". Specifically, Raptor utilizes a full-flow staged combustion cycle, where 100 percent of the oxidizer—with a low-fuel ratio—will power the oxygen turbine pump, and 100 percent of the fuel—with a low-oxygen ratio—will power the methane turbine pump. Both streams—oxidizer and fuel—will be mixed completely in the gas phase before they enter the combustion chamber. Prior to 2014, only two full-flow staged combustion rocket engines had ever progressed sufficiently to be tested on test stands: the Soviet RD-270 project in the 1960s and the Aerojet Rocketdyne Integrated Powerhead Demonstrator in the mid-2000s.

Additional characteristics of the full-flow design, projected to further increase performance or reliability include:

• eliminating the fuel-oxidizer turbine interseal, which is a potential point of failure in more traditional engine designs
• lower pressures are required through the pumping system, increasing life span and further reducing risk of catastrophic failure
• ability to increase the combustion chamber pressure, thereby either increasing overall performance, or "by using cooler gases, providing the same performance as a standard staged combustion engine but with much less stress on materials, thus significantly reducing material fatigue or [engine] weight".

SpaceX aims at a lifetime of 1000 flights for Raptor.

The turbopump and many of the critical parts of the injectors for the initial engine development testing were, as of 2015, manufactured by using 3D printing, which increases the speed of development and iterative testing. Forty percent (by mass) of the 2016 1 MN (220,000 lb_f) test stand engine was manufactured by 3D printing.

The Raptor engine uses a large number of coaxial swirl injectors to admit propellants to the combustion chamber, rather than pintle injectors used on the previous Merlin rocket engines that SpaceX mass-produced for its Falcon family of launch vehicles. Raptor uses "dual redundant torch igniters."

History

The engine development from 2009 to 2015 was funded exclusively through private investment by SpaceX, and not as a result of any funding from the US government. In January 2016, SpaceX did agree with the US Air Force to take US$33.6 million in defense department funding in order to develop a particular Raptor model: a prototype of a new upper-stage variant of the Raptor engine designed for potential use as an upper stage on Falcon 9 and Falcon Heavy, with SpaceX agreeing to fund at least US$67.3 million on the same upper-stage development project, on a minimum 2:1 private-to-government funding basis.

Initial concept

An advanced rocket engine design project named Raptor—then a hydrolox engine—was first publicly discussed by SpaceX's Max Vozoff at the American Institute of Aeronautics and Astronautics Commercial Crew/Cargo symposium in 2009. As of April 2011, SpaceX had a small number of staff working on the Raptor upper-stage engine, then still a LH
2/LOX concept, at a low level of priority. Further mention of the development program occurred in 2011. In March 2012, news accounts asserted that the Raptor upper-stage engine development program was underway, but that details were not being publicly released.

In October 2012, SpaceX publicly announced concept work on a rocket engine that would be "several times as powerful as the Merlin 1 series of engines, and won't use Merlin's RP-1 fuel", but declined to specify which fuel would be used. They indicated that details on a new SpaceX rocket would be forthcoming in "one to three years" and that the large engine was intended for the next-generation launch vehicle using multiple of these large engines, that would be expected to launch payload masses of the order of 150 to 200 tonnes (150,000 to 200,000 kg; 330,000 to 440,000 lb) to low Earth orbit, exceeding the payload mass capability of the NASA Space Launch System.

Methane engine announcement and component development

In November 2012, Musk announced a new direction for the propulsion division of SpaceX: developing methane-fueled rocket engines. He further indicated that the engine concept, codenamed Raptor, would now become a methane-based design, and that methane would be the fuel of choice for SpaceX's plans for Mars colonization.

Potential sources and sinks of methane (CH₄) on Mars.

 

Because of the presence of water underground and carbon dioxide in the atmosphere of Mars, methane, a simple hydrocarbon, can easily be synthesized on Mars using the Sabatier reaction. In-situ resource production on Mars has been examined by NASA and found to be viable for oxygen, water, and methane production. According to a study published by researchers from the Colorado School of Mines, in-situ resource utilization such as methane from Mars makes space missions more feasible technically and economically and enables reusability.

When first mentioned by SpaceX in 2009, the term "Raptor" was applied exclusively to an upper-stage engine concept—and 2012 pronouncements indicated that it was then still a concept for an upper stage engine—but in early 2014 SpaceX confirmed that Raptor would be used both on a new second stage, as well as for the large (then, nominally a 10-meter-diameter) core of the then-named Mars Colonial Transporter (subsequently, in 2016, on both stages of the even larger ITS launch vehicle concept and then, in 2017 and 2018, on the currently-in-development 9-meter diameter BFR).

The earliest public hints that a staged-combustion methane engine was under consideration at SpaceX were given in May 2011 when SpaceX asked if the Air Force was interested in a methane-fueled engine as an option to compete with the mainline kerosene-fueled engine that had been requested in the USAF Reusable Booster System High Thrust Main Engine solicitation.

Public information released in November 2012 indicated that SpaceX might have a family of Raptor-designated rocket engines in mind; this was confirmed by SpaceX in October 2013. However, in March 2014 SpaceX COO Gwynne Shotwell clarified that the focus of the new engine development program is exclusively on the full-size Raptor engine; smaller subscale methalox engines were not planned on the development path to the very large Raptor engine.

In October 2013, SpaceX announced that they would be performing methane engine tests of Raptor engine components at the John C. Stennis Space Center in Hancock County, Mississippi, and that SpaceX would add equipment to the existing test stand infrastructure in order to support liquid methane and hot gaseous methane engine component testing. In April 2014, SpaceX completed the requisite upgrades and maintenance to the Stennis test stand to prepare for testing of Raptor components, and the engine component testing program began in earnest, focusing on the development of robust startup and shutdown procedures, something that is typically quite difficult to do for full-flow staged combustion cycle engines. Component testing at Stennis also allowed hardware characterization and verification of proprietary analytical software models that SpaceX developed to push the technology on this engine cycle that had little prior development work in the West.

October 2013 was the first time SpaceX disclosed a nominal design thrust of the Raptor engine—2,900 kN (661,000 lbf)—although early in 2014 they announced a Raptor engine with greater thrust, and in 2015, one with lower thrust that might better optimize thrust-to-weight.

In February 2014, Tom Mueller, the head of rocket engine development at SpaceX, revealed in a speech that Raptor was being designed for use on a vehicle where nine engines would "put over 100 tons of cargo up to Mars" and that the rocket would be more powerful than previously released publicly, producing greater than 4,400 kN (1,000,000 lbf). A June 2014 talk by Mueller provided more specific engine performance target specifications indicating 6,900 kN (1,600,000 lbf) of sea-level thrust, 8,200 kN (1,800,000 lbf) of vacuum thrust, and a specific impulse (I_sp) of 380 s (3,700 m/s) for a vacuum version. Earlier information had estimated the design I_sp under vacuum conditions as only 363 s (3,560 m/s). Jeff Thornburg, who led development of the Raptor engine at SpaceX 2011–2015, noted that methane rocket engines have higher performance than kerosene/RP-1 and lower than hydrogen, with significantly fewer problems for long-term, multi-start engine designs than kerosene—methane is cleaner burning—and significantly lower cost than hydrogen, coupled with the ability to "live off the land" and produce methane directly from extraterrestrial sources.

SpaceX successfully began development testing of injectors in 2014 and completed a full-power test of a full-scale oxygen preburner in 2015. 76 hot fire tests of the preburner, totaling some 400 seconds of test time, were executed from April–August 2015. SpaceX completed its planned testing at NASA Stennis in 2014 and 2015.

In January 2015, Elon Musk stated that the thrust they were currently targeting was around 230 tonnes-force (2,300 kN; 510,000 lb_f), much lower than older statements mentioned. This brought into question much of the speculation surrounding a 9-engine booster, as he stated "there will be a lot of [engines]". By August 2015, an Elon Musk statement surfaced that indicated the oxidizer to fuel ratio of the Mars-bound engine would be approximately 3.8 to 1.

In January 2016, the US Air Force awarded a US$33.6 million development contract to SpaceX to develop a prototype version of its methane-fueled reusable Raptor engine for use on the upper stage of the Falcon 9 and Falcon Heavy launch vehicles, which required double-matching funding by SpaceX of at least US$67.3 million. Work under the contract is expected to be completed in 2018, with engine performance testing to be done at NASA's John C. Stennis Space Center in Mississippi and Los Angeles Air Force Base, California.

Engine development and testing

Testing of the Raptor's oxygen preburner at Stennis Space Center in 2015.

 

Initial development testing of Raptor methane engine components was done at the Stennis Space Center in Hancock County, Mississippi, where SpaceX added equipment to the existing infrastructure in order to support liquid methane engine testing. Initial testing was limited to components of the Raptor engine, since the 440 kN (100,000 lbf) test stands at the E-2 complex at Stennis were not large enough to test the full Raptor engine. The development Raptor engine discussed in the October 2013 time frame relative to Stennis testing was designed to generate more than 2,900 kN (661,000 lbf) vacuum thrust. A revised, higher-thrust, specification was discussed by the company in February 2014, but it was unclear whether that higher thrust was something that would be achieved with the initial development engines. Raptor engine component testing began in May 2014 at the E-2 test complex which SpaceX modified to support methane engine tests. The first items tested were single Raptor injector elements, various designs of high-volume gas injectors. The modifications to the test stands made by SpaceX are now a part of the Stennis test infrastructure and are available to other users of the test facility after the SpaceX facility lease was completed. SpaceX successfully completed a "round of main injector testing in late 2014" and a "full-power test of the oxygen preburner component" for Raptor by June 2015. Tests continued at least into September 2015.

By 2016, SpaceX had constructed a new engine test stand at their site of McGregor in central Texas that can handle the larger thrust of the full Raptor engine.

By August 2016, SpaceX confirmed that a Raptor engine had been shipped to the testing site in McGregor for development tests, and the 1,000 kN (220,000 lbf) development Raptor did an initial 9-second firing test on 26 September 2016, the day before Musk's talk at the International Aeronautical Congress. The 2016 development engine had "an expansion ratio of just 150, the maximum possible within Earth’s atmosphere" to prevent flow separation problems.

By August 2016, the first integrated Raptor rocket engine, manufactured at the SpaceX Hawthorne facility in California, shipped to the McGregor rocket engine test facility in Texas for development testing. The engine had 1 MN (220,000 lb_f) thrust, which makes it approximately one-third the size of the full-scale Raptor engine planned for flight tests in 2019/2020 timeframe. It is the first full-flow staged-combustion methalox engine ever to reach a test stand.

On 26 September 2016, Elon Musk tweeted two images of the first test firing of an integrated Raptor in SpaceX's McGregor test complex. On the same day Musk revealed that their target performance for Raptor was a vacuum specific impulse of 382 s (3,750 m/s), with a thrust of 3 MN (670,000 lb_f), a chamber pressure of 300 bar (30 MPa; 4,400 psi), and an expansion ratio of 150 for an altitude optimized version. When asked if the nozzle diameter for such version was 14 ft (4.3 m), he stated that it was pretty close to that dimension. He also disclosed that it used multi-stage turbopumps. On the 27th he clarified that 150 expansion ratio was for the development version, that the production vacuum version would have an expansion ratio of 200. Substantial additional technical details of the ITS propulsion were summarized in a technical article on the Raptor engine published the next week.

By September 2017, the development Raptor engine—with 200 bars (20 MPa; 2,900 psi) chamber pressure—had undergone 1200 seconds of test fire testing in ground-test stands across 42 main engine tests, with the longest test being 100 seconds (which is limited by the capacity of the ground-test propellant tanks). As of September 2017, the first version of the flight engine is intended to operate at a chamber pressure of 250 bars (25 MPa; 3,600 psi), with the intent to raise it to 300 bars (30 MPa; 4,400 psi) at a later time.

By September 2017, the 200 bars (20 MPa; 2,900 psi) sub-scale test engine, with a thrust of 1 meganewton (220,000 lb_f) and "a new alloy to help its oxygen-rich turbopump resist oxidization, ... had completed 1200 seconds of firings across 42 tests."

While plans for Raptor flight testing have consistently been on the new-generation fiber-composite-material construction flight vehicles since 2016, the specific vehicle was not clarified until October 2017, when it was indicated that initial suborbital test flights would occur with a BFR spaceship. In November 2016, the first flight tests of the Raptor engine were projected to be on the very large 12-meter (39 ft)-diameter ITS launch vehicle, no earlier than the early 2020s. By July 2017, the plan had been modified to do flight testing on a much smaller launch vehicle and spacecraft, and the new system architecture had "evolved quite a bit" since the very large ITS launch vehicle design concept from 2016. A key driver of the 2017 architecture was to make the new system useful for substantial Earth-orbit and Cislunar launches so that the new system might pay for itself, in part, through economic spaceflight activities in the near-Earth space zone.

Elon Musk announced in September 2017 that the initial flight platform for any Raptor engine would be some part of the BFR launch vehicle. BFR is a 9 m (30 ft)-diameter launch vehicle. In October 2017, Musk clarified that "[initial flight testing will be with] a full-scale 9-meter-diameter ship doing short hops of a few hundred kilometers altitude and lateral distance ... [projected to be] fairly easy on the vehicle, as no heat shield is needed, we can have a large amount of reserve propellant and don’t need the high area ratio, deep-space Raptor engines."

Notably, Musk also announced that the new Raptor-powered BFR launch vehicle was planned to entirely replace both Falcon 9 and Falcon Heavy launch vehicles as well as the Dragon spacecraft in the existing operational SpaceX fleet in the early 2020s, initially aiming at the Earth-orbit market, but SpaceX is explicitly designing in substantial capability to the spacecraft vehicles to support long-duration spaceflight in the cislunar and Mars mission environment as well. SpaceX intends this approach to bring significant cost savings which will help the company justify the development expense of designing and building the new launch vehicle design. In addition to orbital spaceflight missions, BFR is being considered for the point-to-point Earth transportation market, with ~30–60-minute flights to nearly anywhere on the planet.

The first flight version of the Raptor engine planned for the Starship hopper arrived in McGregor, Texas in late January 2019.

On 3 February 2019, SpaceX performed the first test of a flight version engine. The test lasted two seconds with the engine operating at 60 percent of rated thrust at a chamber pressure of 170 bars (17,000 kPa). Just four days later, the test engine achieved the power levels needed for use in Super Heavy and Starship. The engine reached 172 tonnes-force (1,690 kN; 380,000 lb_f) thrust with a chamber pressure of 257 bars (25.7 MPa). The test was conducted using warm propellant, with expectations of a 10% to 20% increase in performance when switching to deep cryogenic temperatures for the propellant. On 10 February 2019, Musk announced on Twitter that the flight version engine had attained the chamber combustion pressure of 268.9 bars (26.89 MPa) on a test stand.

By March, serial number 2 (SN2) of the flight version Raptor engine had been delivered to the SpaceX South Texas launch site east of Brownsville, Texas for system integration testing on the Starship flight test rocket, the first test article of Starship, approximately one year ahead of schedule. SN2 was used for two tethered integration tests of the flight test "hopper" in early April. Serial numbers 3, 4, 5 and 6 had all made it to the test stand by early July, but the first three had issues of various sorts and SpaceX did not try any flight tests of the Starhopper test vehicle. SN6 was still under test on the ground test stand as of 8 July 2019.

The first flight test of a Raptor engine occurred on 25 July 2019 at the SpaceX South Texas Launch Site. Unusually, for initial flight tests of orbital-class rocket engines, this was not a full-duration burn but just a 22-second test. SpaceX is developing their next-generation rocket to be reusable from the beginning, just like an aircraft, and thus needs to start with narrow flight test objectives, while still aiming to land the rocket successfully to be used subsequently in further tests to expand the flight envelope.

Another flight test of a Raptor engine (probably SN6) occurred on 27 August 2019 from Boca Chica, Texas, test facility. The starhopper test vehicle reached an estimated altitude of 150m (FAA approved). A side step and a perfect landing on a nearby landing pad terminated the roughly 1 minute flight. 

Versions

IAC 2016 proposed designs

At the IAC meetings September 2016, Musk mentioned several Raptor engine designs that could be used on the ITS launch vehicle by late in the decade. In addition, a much smaller subscale engine had been built for test and validation of the new full-flow staged-combustion cycle engine. At that time, this first "subscale" Raptor development engine had been tested on a ground test stand for only one brief firing.

"Raptor subscale development engine"

In order to eliminate flow separation problems while being tested in Earth's atmosphere, the test nozzle expansion ratio was limited to only 150. The engine began testing in September 2016 on a ground test stand. Sources differ on the performance of this engine. In reporting during the two weeks following the Musk reveal on 27 September, NASASpaceFlight.com indicated that the development engine is only one-third the size of any of the three larger engine designs planned for the 2016-design flight vehicles, approximately 1,000 kN (220,000 lbf) thrust.

Raptor 2016 with expansion ratio 40

With an expansion ratio 40 nozzle, 42 of these engines were planned to power the 2016 high-level design of the ITS booster stage. 3,050 kN (690,000 lbf) of thrust at sea-level, and 3,285 kN (738,000 lbf) in vacuum. In addition, three gimbaled short-nozzle engines were to be used for maneuvering the 2016-design ITS launch vehicle second-stages; and these engines were to be used for retropropulsive landings on Mars (with mean atmospheric pressure on the Martian surface 600 Pa (0.0060 bar; 0.087 psi)), as well as, potentially, other Solar System objects.

Raptor 2016 with expansion ratio 200

Like the SpaceX Merlin engine, a vacuum version of the Raptor rocket engine design was shown which would target a specific impulse of 382s, using a larger nozzle giving an expansion ratio of 200. Six of these non-gimbaled engines were planned to provide primary propulsion for the 2016 designs of the Interplanetary Spaceship and the Earth-orbit ITS tanker. As designed, both of those vehicles were to play a short-term role as second stages on launches to Earth orbit, as well as provide high-I_sp efficiency on transfer from geocentric to heliocentric orbit for transport to beyond-Earth-orbit celestial bodies. 3,500 kN (790,000 lbf) thrust at vacuum, the only conditions under which the six ER200 engines were expected to be fired.

Raptor 2017

At the IAC meetings of September 2017, Elon Musk announced that a smaller Raptor engine—with slightly over half as much thrust as the 2016 proposed designs—would be used on the BFR rocket than had been used on the ITS launch vehicle design unveiled a year earlier. Additionally, fewer engines would be used on each stage. BFR would have 31 Raptors on the first stage and 6 on the second stage, whereas the ITS launch vehicle design had 42 larger Raptor engines on the first stage and 9 of that same large size on the second stage. The engine design remains full-flow staged combustion cycle design using subcooled liquid-methane/liquid-oxygen propellant, just like the larger 2016 engine design. Version 1 of the flight engine is designed to operate at 250 bars (25,000 kPa; 3,600 psi) chamber pressure; but SpaceX expects to increase this to 300 bar (30,000 kPa; 4,400 psi) in later iterations. The flight engine is designed for extreme reliability, aiming to support the airline-level of safety required by the point-to-point Earth transportation market.

• The sea-level model Raptor engine design, with a nozzle exit diameter of 1.3 m (4.3 ft), is expected to have 1,700 kN (380,000 lbf) thrust at sea-level with an I_sp of 330 s (3,200 m/s) increasing to an I_sp of 356 s (3,490 m/s) in vacuum.
• The vacuum model Raptor, with a nozzle exit diameter of 2.4 m (7.9 ft), is expected to exert 1,900 kN (430,000 lbf) force with an I_sp of 375 s (3,680 m/s).
  

Raptor 2018

In the BFR update given in September 2018, Musk showed video of a 71-second burn of a Raptor engine, and stated that "this is the Raptor engine that will power BFR, both the ship and the booster; it's the same engine. ... approximately a 200 short tons-force (1,800 kN; 400,000 lbf) engine aiming for roughly 300 bars (30,000 kPa; 4,400 psi) chamber pressure. ... If you had it at a high expansion ratio, has the potential to have a specific impulse of 380 s (3,700 m/s)." The update also included a redesigned Starship with seven sea-level Raptor engines instead of the three sea-level and four vacuum on the previous design.

Later versions will be split into a sea-level design and a vacuum-optimized design again.

Applications

As of September 2016, the Raptor engine was slated to be used in three spaceflight vehicles making up the two launch stages of an ITS launch vehicle stack. The first stage is always an Interplanetary booster while the second stage may be either an Interplanetary Spaceship (for beyond-Earth-orbit missions) or an ITS tanker (for on-orbit propellant transfer operations nearer to Earth).

The SpaceX 2016-design of the Interplanetary booster was announced with 42 sea-level optimized Raptors in the first stage of the ITS launch vehicle with a total of 128 MN (29,000,000 lbf) of thrust. The SpaceX Interplanetary Spaceship—which made up the second stage of the ITS launch vehicle on Earth launches was also an interplanetary spacecraft carrying cargo and passengers to beyond-Earth-orbit destinations after on-orbit refueling—was slated in the 2016 design to use six vacuum-optimized Raptors for primary propulsion plus three Raptors with sea-level nozzles for maneuvering.

The SpaceX 2017-design is a much smaller launch vehicle, 9 meters in diameter rather than 12 meters for the ITS launch vehicle, and is known as Starship. The Starship first stage was originally planned to have 31 sea-level optimized Raptors with a total of 48 MN (11,000,000 lbf) of thrust. The Starship will use three vacuum-optimized Raptors for primary propulsion plus three sea-level Raptors for maneuvering. SpaceX will build the flight-article Starship vehicles at the SpaceX South Texas build site.