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SLS (Space Launch System)

Development Status    References

The SLS is the new heavy launch system for NASA. The SLS configuration for EM-1 is considered Block 1, the first configuration of the SLS evolution plan. The Shuttle-derived design takes advantage of resources established for the Space Shuttle, including the workforce, tooling, manufacturing processes, supply chain, transportation logistics, launch infrastructure, and LOX/LH2 propellant infrastructure. An overview of the initial SLS Block 1 configuration that will first fly with the Orion in 2020 is shown in Figure 1. The SLS enables many aspects of the NASA core capabilities in addition to human exploration initiatives. These include the reduction in mission duration, increased mass margins, reductions in total spacecraft complexity, and significant increases in payload volume. 1) 2) 3) 4)

Created to provide sufficient launch capability to enable human exploration missions beyond Earth orbit and ultimately to Mars, NASA's Space Launch System (SLS) rocket represents a new asset, not only for human spaceflight, but also for a variety of other payloads and missions with launch requirements beyond what is currently available. The initial configuration of the vehicle, on track for launch readiness in 2020, is designed to offer substantial launch capability in an expeditious timeframe and to support evolution into configurations offering greater launch capability via an affordable and sustainable development path.

NASA is developing SLS in parallel with two other exploration systems development efforts – the Orion crew vehicle program and the Ground Systems Development and Operations (GSDO) program. Orion is a four-person spacecraft designed to carry astronauts on exploration missions into deep space. GSDO is converting the facilities at NASA's Kennedy Space Center (KSC) in Florida into a next-generation spaceport capable of supporting launches by multiple types of vehicles.

These capabilities are part of a larger NASA strategy of working with commercial partners that will support crew and cargo launches to the International Space Station, while the agency focuses its development efforts on an incremental approach to developing the systems necessary for human exploration beyond Earth orbit and eventually to Mars. SLS is being designed with performance margin and flexibility to support an evolvable human exploration approach. (Figure 2).

Currently under construction, the initial configuration of the vehicle will have the capability to deliver a minimum of 70 t into low Earth orbit (LEO) and will be able to launch a crew aboard the Orion spacecraft on into cislunar space on its first flight, Exploration Mission-1 (EM-1) in 2020. The vehicle will evolve to a full capability of greater than 130 t to LEO and will be able to support a stepping-stone approach to human exploration leading to the first footsteps on Mars.

The SLS initial Block 1 configuration stands 97 meters tall, including the Orion crew vehicle. The vehicle's architecture reflects NASA's desire to meet the mandates for heavy-lift capability in the U.S. congressional NASA Authorization Act of 2010 in a manner that is safe, affordable, and sustainable. After input was received from industry and numerous concepts were reviewed, a shuttle-derived design was found to enable the safest, most-capable transportation system in the shortest amount of time for the anticipated near-term and long-range budgets.

The SLS operational scheme takes advantage of resources established for the Space Shuttle Program, including workforce, tooling, manufacturing processes, supply chains, transportation logistics, launch infrastructure, and liquid oxygen and hydrogen (LOX/LH2) propellants and allows the initial configuration of the vehicle to be delivered with only one clean-sheet new development, the Core Stage. In October 2015, the SLS Program completed its Critical Design Review (CDR), the first time a NASA human-class launch vehicle has reached that milestone since the Shuttle Program almost 40 years ago.

The SLS Core Stage, which stores the liquid oxygen (LOX) and liquid hydrogen (LH2) propellant for four Core Stage engines, will stand 61 m tall and will have a diameter of 8.4 m, sharing commonality with the space shuttle's external tank in order to enhance compatibility with equipment and facilities at Kennedy Space Center and elsewhere. At Michoud Assembly Facility (MAF), outside New Orleans, Louisiana, the last of six major welding manufacturing tools for the Core Stage, the world's largest space vehicle welding tool, the 52m-tall Vertical Assembly Center (VAC), has been installed and is being used by The Boeing Company, Core Stage prime contractor, to weld barrel sections, rings and domes together to form the propellant tanks for the stage.


Figure 1: SLS Block 1 70t Initial Configuration (image credit: NASA)

The Core Stage will be powered by four RS-25 engines, which previously served as the Space Shuttle Main Engine (SSME), taking advantage of 30 years of U.S. experience with liquid oxygen and liquid hydrogen, as well as an existing U.S. national infrastructure that includes specialized manufacturing and launching facilities. These human-rated engines support the SLS goal of safety, with a record of 100 percent mission success for the engines over 135 flights. At the end of the Space Shuttle Program, 16 RS-25 flight engines and two development engines were transferred to the SLS Program and placed in inventory at NASA's Stennis Space Center, providing enough engines for the first four flights of SLS.

While the SLS Program is heavily focused on working toward first flight, efforts are already underway on the evolution of SLS beyond the 70 t Block 1. As early as the second launch of SLS, Exploration Mission-2, the vehicle will be augmented with a low-thrust dual-use Exploration Upper Stage (EUS), providing both ascent and in-space propulsion capabilities. This stage, which is working toward a preliminary design review in late 2016, will upgrade SLS to a performance of 105 t to LEO, and create a configuration that will serve as a workhorse for "Proving Ground" missions in cislunar space that will pave the way for further exploration. From there, additional upgrades, including enhancements to the RS-25 engines and upgraded boosters will ultimately evolve SLS to a configuration capable of delivering more than 130 metric tons to LEO, the capability identified as necessary for human missions to Mars.


Figure 2: Evolutionary development path of SLS (Space Launch System), image credit: NASA

Modifications to Stennis Test Stand A-1 to support RS-25 testing were completed in 2014, and two test series have already been completed in preparation for flight certification of the SLS configuration of the engine, including a new engine controller unit. The testing includes propellant pressure and temperature inlet conditions that will both be higher with SLS than with the shuttle, as well as other SLS-specific performance requirements such as 109 percent thrust versus the shuttle's 104.5 percent thrust. Stennis Test Stand B-2 is being refitted for the SLS "green run" – the test firing of the first Core Stage with four RS-25 engines beginning in 2017, which will be NASA's largest engine ground firing since stage tests of the Saturn V in the 1960s.

The majority of the thrust for the first two minutes of flight will come from a pair of Solid Rocket Boosters, also of Space Shuttle Program heritage. The SLS is upgrading the boosters from the four-segment version flown on the shuttle to a more-powerful five-segment version. Each booster measures 54 m long and 3.7 m in diameter and is capable of generating up to 3.6 million pounds of thrust, the most powerful flight boosters in the world. Although largely similar to the SRBs used on the space shuttle, this upgraded five-segment SRB includes improvements such as a larger nozzle throat and an environmentally-benign insulation and liner material. In March 2015, the SLS configuration of the booster successfully underwent the first of two Qualification Motor tests, and the second test is scheduled for summer 2016.

In-space propulsion for the 70 t Block 1 version of SLS will be provided by the Interim Cryogenic Propulsion Stage (ICPS), a modified version of United Launch Alliance's Delta Cryogenic Second Stage (DCSS) flown on more than 20 launches of the Delta IV Evolved Expendable Launch Vehicle (EELV). In order to support the currently planned initial test flight that would send Orion on a circumlunar trajectory, the LH2 tank of the SLS ICPS will be stretched 46 cm longer than the standard DCSS.

While the SLS Program is heavily focused on working toward first flight, efforts are already underway on the evolution of SLS beyond the 70 t Block 1. As early as the second launch of SLS, Exploration Mission-2, the vehicle will be augmented with a low-thrust dual-use Exploration Upper Stage (EUS), providing both ascent and in-space propulsion capabilities. This stage, which is working toward a preliminary design review in late 2016, will upgrade SLS to a performance of 105 t to LEO, and create a configuration that will serve as a workhorse for "Proving Ground" missions in cislunar space that will pave the way for further exploration. From there, additional upgrades, including enhancements to the RS-25 engines and upgraded boosters will ultimately evolve SLS to a configuration capable of delivering more than 130 metric tons to LEO, the capability identified as necessary for human missions to Mars.


Figure 3: Welding is complete on the largest piece of the core stage that will provide the fuel for the first flight of NASA's new rocket, the Space Launch System, with the Orion spacecraft in 2018. The core stage liquid hydrogen tank has completed welding on the Vertical Assembly Center at NASA's Michoud Assembly Facility in New Orleans. Standing more than 40 m tall and 8.4 m in diameter, the liquid hydrogen tank is the largest cryogenic fuel tank for a rocket in the world. The liquid hydrogen tank and liquid oxygen tank are part of the core stage — the "backbone" of the SLS rocket that will stand at more than 61 m tall. Together, the tanks will hold 733,000 gallons (2775 m3) of propellant and feed the vehicle's four RS-25 engines to produce a total of 2 million pounds of thrust (8896 kN) This is the second major piece of core stage flight hardware to finish full welding on the Vertical Assembly Center. The core stage flight engine section completed welding in April 2016. More than 1.7 miles of welds have been completed for core stage hardware at Michoud. Traveling to deep space requires a large rocket that can carry huge payloads, and SLS will have the payload capacity needed to carry crew and cargo for future exploration missions, including NASA's Journey to Mars. 5)

The secondary payload initiative for EM-1 takes advantage of several of these capabilities and enables new opportunities for small spacecraft developers. By utilizing planned unoccupied volume within the upper stage adapter ring, the OSA (Orion Stage Adapter), increased mission science and technology missions can be accommodated.


Figure 4: David Osborne, an Aerie Aerospace LLC machinist at NASA's Marshall Space Flight Center in Huntsville, Alabama, takes measurements prior to the start of precision machining of the Orion stage adapter for NASA's new rocket, the SLS (Space Launch System). The adapter will connect the Orion spacecraft to the ICPS (Interim Cryogenic Propulsion Stage) for the first flight of SLS with Orion in late 2018. The ICPS is the liquid oxygen/liquid hydrogen-based system that will give Orion the big, in-space push needed to fly beyond the moon before it returns to Earth. The adapter also will carry 13 CubeSats that will perform science and technology investigations that will help pave the way for future human exploration in deep space, including the Journey to Mars (image credit: NASA, Sept. 29, 2016)

SLS Block 1 is capable of deploying 70 metric tons of payload into LEO (Low Earth Orbit). The characteristic energy (C3) curve for SLS is provided in Figure 2, illustrating SLS's evolved thrust capabilities.


Figure 5: SLS Net-Payload System Mass-Earth Escape (image credit: NASA)



Status of SLS development:

• April 16, 2019: The boat-tail structure, a fairing-like cover designed to protect the bottom end of the core stage and the RS-25 engines, has been joined to one of the most complicated and intricate parts of NASA's Space Launch System, the engine section. The engine section comprises the lowest portion of the massive core stage of the deep space rocket. It houses four RS-25 engines that will produce 2 million pounds of thrust to send the rocket and NASA's Orion spacecraft on lunar missions. 6)

- NASA is charged to get American astronauts to the Moon by 2024. Our backbone for deep space exploration is SLS, the Orion spacecraft, which will launch from NASA's Kennedy Space Center in Florida on missions to the Gateway in lunar orbit for missions to the surface of the Moon. The agency will launch SLS and Orion on their first integrated test flight around the Moon in 2020.


Figure 6: Technicians moved the engine section and boat-tail for final assembly to a climate-controlled area of NASA's Michoud Assembly Facility in New Orleans. Engineers will use the new tool and an internal access kit to finish assembly. The tool, seen here in the blue frame around the bottom of the engine section, allows more people to work on engine section tasks at the same time — accelerating the pace of production and reducing engine section integration and assembly time. This tool, along with other production and processing improvements, will help enable the core stage to be completed this year. The liquid oxygen tank structural test article as well as the liquid hydrogen tank flight hardware for the first mission of SLS are located just behind the engine section (image credit: NASA)

• April 15, 2019: America's powerful new deep space rocket, NASA's SLS (Space Launch System), will face harsh conditions and extreme temperatures in flight when launching NASA's Orion spacecraft and potential cargo to lunar orbit, and for that, it'll need strong protection. 7)

- Technicians and engineers have qualified 3D printing to aid in the application of the thermal protection system to the smaller, more intricate parts of the rocket. Spray-on foam or traditional insulation is applied to both large and small components of SLS; it protects the rocket from heat during launch and keeps the propellant within the large tanks cold.

- However, small hardware or cramped areas like the internal ducts of the engine section require technicians to either manually spray the foam on or apply a foam casting using, in some cases, a 3D printed mold. During the process, the foam, which is mixed and poured into the mold, expands to perfectly fit the part. This decreases overall processing time by reducing the need for complex and tedious post-process trimming.

- NASA and Boeing engineers performed extensive development and qualification pour foam testing early in the program. Using this data, the team developed a refined process that reduced the amount of time required to certify individual 3D printed molds and allowed the team to spend more time focusing on the critical requirements that must be met for each flight foam application. This streamlined the process, from 3D printing to pour application, and allowed for quicker processing times.

- NASA is charged to get American astronauts to the Moon by 2024. Our backbone for deep space exploration is SLS and Orion, which will launch from NASA's Kennedy Space Center in Florida to the Gateway in lunar orbit. From there, astronauts will ultimately use a proposed human lunar landing system for missions to the surface of the Moon.


Figure 7: A Space Launch System (SLS) rocket model is prepped for wind tunnel testing by Courtney Winski, aerospace engineer, at the Unitary Plan Wind Tunnel at NASA's Langley Research Center in Hampton, Virginia. The pink pressure-sensitive paint on the 0.8 percent scale model emits a bright crimson glow when reacting with oxygen in the presence of high-pressure airflows. This test allows engineers to understand changing pressures exerted on the rocket during a launch (image credit: NASA)

• April 4, 2019: NASA is a step closer to returning astronauts to the Moon in the next five years following a successful engine test on Thursday at NASA's SSC (Stennis Space Center) near Bay St. Louis, Mississippi. The latest "hot fire" was the culmination of four-plus years of testing for the RS-25 engines that will send the first four Space Launch System (SLS) rockets into space. 8)

- "This completes four years of focused work by an exceptional Stennis test team," Stennis Director Rick Gilbrech said. "It represents yet another chapter in Stennis' long history of testing leadership and excellence in support of this nation's space exploration efforts. Everyone involved should feel proud of their work and contributions."

- Thursday's hot fire on Stennis' A-1 Test Stand completed:

a) Acceptance testing of all 16 former space shuttle main engines that will help launch the first four SLS missions. NASA has contracted with Aerojet Rocketdyne to build new RS-25 engines for additional SLS missions, and work already is underway to do so in the company's factory in Canoga Park, California.

b) Developmental and flightworthy testing for new controllers (plus one spare) to be used by the heritage RS-25 engines for the first four missions.

c) A 51-month test series that demonstrated RS-25 engines can perform at the higher power level needed to launch the super heavy-lift SLS rocket.

- "Engines are now a ‘go' for missions to send astronauts forward to the Moon to learn and prepare for missions to Mars," said Johnny Heflin, deputy manager of the SLS Liquid Engines Office at NASA's Marshall Space Flight Center in Huntsville, Alabama. "We're ready to provide the power to explore the Moon and beyond."

- The RS-25 rocket engine test era began Jan. 9, 2015, with a 500-second – more than 8 minute – hot fire of RS-25 developmental engine No. 0525 on the A-1 Test Stand at Stennis. NASA tested the first SLS flight engine on March 10, 2016. Altogether, the agency has conducted 32 developmental and flight engine tests for a total of 14,754 seconds – more than four hours – of cumulative hot fire – all on the A-1 stand at Stennis.

- Having launched 135 space shuttle missions, these main engines are considered the most tested engines in the world. When the Space Shuttle Program ended in 2011, NASA still had 16 engines that ultimately were modified for SLS.

- These engines were originally designed to perform at a certain power level, known as 100 percent. Over time, the engines were upgraded to operate at higher and higher power levels, up to 104.5 percent operating power level by the end of the shuttle program. For SLS, that operating level has to be pushed even higher.

- To help accomplish that, and to interface with new rocket avionics systems, NASA designed and tested a new engine controller, which serves as the "brain" of the engine to help monitor engine operation and facilitate communication between the engine and rocket. Early developmental testing at Stennis provided critical information for designing the new controller.


Figure 8: RS-25 flight engine No. 2062 is lifted onto the A-1 Test Stand at NASA's Stennis Space Center near Bay St. Louis, Miss. The Aerojet Rocketdyne-built engine was delivered to the stand March 20 and test fired April 4 (image credit: NASA/SSC)


Figure 9: NASA conducts a test of RS-25 flight engine No. 2062 on April 4 on the A-1 Test Stand at Stennis Space Center near Bay St. Louis, Miss. The test marked a major milestone in NASA's march forward to Moon missions. All 16 RS-25 engines that will help power the first four flights of NASA's new Space Launch System rocket now have been tested (image credit: NASA/SSC)

- The first new flight engine controller was tested at Stennis in March 2017, with a string of controller hot fires to follow. The April 4 test marked the testing of the 17th engine controller for use on SLS flights, providing enough for all 16 heritage RS-25 engines.

- With development of the new controllers, NASA had to test the new power level as well. First, it was demonstrated that the engine could perform at the needed 111 percent power level. Next, NASA needed to prove a margin of operating safety.

- In February 2018, operators pushed the engine to 113 percent power for a total of 50 seconds. It lengthened that firing time in two subsequent tests, until late this February, when the engine was fired at 113 percent power for 430 seconds of a 510-second test.

- That set the stage for Thursday's successful test of flight engine No. 2062. When this specific engine fires again, it will help send astronauts aboard Orion around the Moon on a test flight known as Exploration Mission-2.

Figure 10: NASA is going to the Moon and on to Mars, in a measured, sustainable way. Working with U.S. companies and international partners, NASA will push the boundaries of human exploration forward to the Moon. NASA is working to establish a permanent human presence on the Moon within the next decade to uncover new scientific discoveries and lay the foundation for private companies to build a lunar economy (video credit: NASA, Published on 11 March 2019)

• March 19, 2019: NASA and its industry partners continue their steady progress toward launching the nation's newest rocket, NASA's Space Launch System (SLS). Engineers and technicians at NASA's Marshall Space Flight Center in Huntsville, Alabama, are integrating components with the SLS launch vehicle stage adapter, which connects the core stage of the world's most powerful rocket with its interim cryogenic propulsion stage (ICPS) that provides the power to send Orion to the Moon. 9)

- One newly installed piece of hardware — the frangible joint assembly — is designed to break apart, allowing the hardware elements to separate during flight. When a remote command is given, pistons fitted inside the ring assembly push upward, instantaneously separating the upper part of the rocket from the adapter and core stage.

- Frangible joint assemblies are widely used in a variety of crewed and uncrewed spacecraft to efficiently separate fairings or stages during launch and orbital ascent and to execute payload deployment. Once the frangible joint assembly is mated with the launch vehicle stage adapter and its pneumatic actuation system is installed, Marshall SLS workers will ship the hardware to NASA's Kennedy Space Center in Florida, where technicians will "stack" the vehicle for final flight preparation. NASA's Space Launch System and Orion spacecraft will pave the way for human missions to the Moon and Mars and groundbreaking new discoveries.


Figure 11: NASA teams install key SLS Stage Separation Mechanism. NASA and its industry partners continue their steady progress toward launching the nation's newest rocket, NASA's Space Launch System (SLS). Engineers and technicians at NASA's Marshall Space Flight Center in Huntsville, Alabama, are integrating components with the SLS launch vehicle stage adapter (image credit: NASA)

• March 8, 2019: NASA will soon return humans to the Moon for decades to come, and the system that will transport astronauts from Earth to the Gateway near the Moon is literally coming together. Building on progress in 2018, most of the major manufacturing for the first mission is complete, and this year, teams will focus on final assembly, integration, and testing, as well as early work for future missions. NASA is focused on launching the first mission, Exploration Mission-1 (EM-1), in 2020 to send an Orion spacecraft on the SLS (Space Launch System) rocket from the modernized spaceport at Kennedy Space Center in Florida on an uncrewed test flight before sending crew around the Moon and back on the second mission, Exploration Mission-2 (EM-2) by 2023. 10)

- For the Orion spacecraft that will fly on EM-1, engineers will continue stacking the crew and service modules together at Kennedy and performing tests to ensure the modules operate properly together. In the summer, the stacked modules will fly aboard the agency's Guppy aircraft to NASA's Plum Brook Station in Sandusky, Ohio, where together they will undergo thermal vacuum testing as well as electromagnetic interference and compatibility evaluations during a four-month test campaign. When Orion returns from Ohio, it will undergo final checks and processing before final preparations for launch and integration with SLS.

- At the same time, Orion teams are also working on the spacecraft and other critical systems for the second mission that will carry a crew of astronauts around the Moon and back. Engineers will continue outfitting and testing the crew module, including pressuring the capsule to verify its structural integrity, powering it on for the first time to ensure it can route commands properly, and routing electrical and propulsion lines. Teams will also perform welding for the environmental control system and fit it for the outer back shells and heatshield.

- In preparation for the first mission with crew, the agency will also test the spacecraft's launch abort system this June to demonstrate that it can carry the crew to safety if an emergency were to happen on the way to space. During the three-minute test, called Ascent Abort-2, a booster will carry an Orion test vehicle to an altitude of 31,000 feet at more than 1,000 mph to test the launch abort system when the spacecraft is under the highest aerodynamic loads it will experience during a rapid climb into space.

The Rocket — Space Launch System (SLS)

- Technicians at NASA's Michoud Assembly Facility in New Orleans are nearly finished with production of the first flight's core stage, the largest element of the most powerful rocket in the world. Technicians have almost completed outfitting the engine section, the complex bottom section of the core stage. Its sophisticated systems feed propellant to the four RS-25 engines. The section will be joined to the 130-foot-long liquid hydrogen propellant tank to form the stage's aft section. The aft section will then be connected to the 66-foot forward section, which consists of the forward skirt, liquid oxygen tank, and intertank, in a horizontal configuration to form the full stage.

- The four core stage engines for EM-1 will be delivered to Michoud later this year and installed into the core stage engine section. NASA's Pegasus barge will move the completed stage to Stennis Space Center near Bay St. Louis, Mississippi, where all four engines will roar to life to test the completed stage.

- The team at Stennis has already completed two engine tests this year, concluding a series of nine tests that began last August. This spring, NASA will mark a major milestone to complete testing of all engines for the first four SLS missions. Aerojet Rocketdyne has already started making the engines for additional flights with the goal of reducing the costs of manufacturing by at least 30 percent using smart manufacturing techniques.

- The last structural test article for the core stage, a full-sized flight-like liquid oxygen tank, will arrive at Marshall Space Flight Center in Huntsville, Alabama, this summer on the Pegasus barge. Engineers will finish up structural testing on the intertank and liquid hydrogen tank and then begin with the liquid oxygen tank to push the hardware to the limits under forces that exceed what the hardware will experience in flight. Testing will also continue for multiple avionics and software systems this year as well.

- Building and moving the 212-foot-tall core stage, the largest rocket stage that NASA has ever built, has been one of the most challenging aspects of SLS construction. NASA is applying this experience to the core stage for the second mission, which is already in production.

- Engineers at Marshall, are putting the finishing touches on the 30-foot-tall launch vehicle stage adapter that will connect the top of the core stage to the interim cryogenic propulsion stage, which was previously delivered to Kennedy. This year, Pegasus will deliver the adapter to Kennedy. The SLS booster team in Utah finished the ten solid rocket motor segments needed for EM-1 earlier this year, and they will also be delivered to Kennedy when needed, where they will join other booster parts.

- For the second SLS flight, building is complete for most of the barrels, domes and other structures needed to build the core stage for EM-2. Nearly all the solid rocket motor sections for the boosters on the second mission are cast and being outfitted. Teams are beginning work on additional parts including the Orion Stage Adapter where other small payloads can be carried, the launch vehicle stage adapter and the interim cryogenic propulsion stage.

Kennedy Space Center — Ground Systems

- At Kennedy, the Exploration Ground Systems team also has a busy year ahead in 2019. The crawler team will finish engine maintenance and crawlerway conditioning, and engineers will complete testing of the mobile launcher in the Vehicle Assembly Building. In the spring, the mobile launcher will roll back out to Pad 39B for its final testing at the pad. NASA plans to award a contract for a second mobile launcher this year, allowing more flexibility for upcoming exploration missions.

- At the pad, engineers will start to install a new liquid hydrogen tank that will be used for EM-2. In firing rooms 1 and 2, final upgrades will be made while the launch team finalizes the new countdown procedures for SLS. Teams across the agency will participate in flight simulations with the launch control center at Kennedy, mission control center at Johnson and the SLS Engineering Support Center at Marshall. By the end of 2019, EGS will begin processing the Orion crew capsule and SLS hardware for launch of EM-1.

• January 31, 2019: NASA and its industry partners have completed manufacture and checkout of 10 motor segments that will power two of the largest solid propellant boosters ever built. The solid rocket fuel will help produce 8.8 million pounds of thrust (35.585 MN) to send NASA's Space Launch System rocket on its first integrated flight with the Orion spacecraft. Technicians at Northrop Grumman in Promontory, Utah, in coordination with SLS program leads at NASA's Marshall Space Flight Center in Huntsville, Alabama, finalized the fabrication of all 10 motor segments and fitted them with key flight instrumentation. 11)

- They'll be shipped to NASA's Kennedy Space Center in Florida, joined with booster forward and aft assemblies, and readied to power the SLS Exploration Mission-1 test flight when it launches from Kennedy. The uncrewed test launch will pave the way for a new era of groundbreaking science and exploration missions beyond low-Earth orbit, carrying crew and cargo to the Moon and on to Mars. Marshall manages the Space Launch System for NASA.


Figure 12: NASA completes booster motor segments for first Space Launch System flight (image credit: NASA)

• January 15, 2019: The largest piece of structural test hardware for America's new deep space rocket, the SLS (Space Launch System), was loaded into Test Stand 4693 at NASA's Marshall Space Flight Center in Huntsville, Alabama on 14 January 2019. The liquid hydrogen tank is part of the rocket's core stage that is more than 200 feet tall (61 m) with a diameter of 27.6 feet (8.4 m), and stores cryogenic liquid hydrogen and liquid oxygen that will feed the vehicle's RS-25 engines. The liquid hydrogen tank test article is structurally identical to the flight version of the tank that will comprise two-thirds of the core stage and hold 537,000 gallons of supercooled liquid hydrogen at minus 423 degrees Fahrenheit (20.4 K). Dozens of hydraulic cylinders in the 215-foot-tall test stand will push and pull the tank, subjecting it to the same stresses and loads it will endure during liftoff and flight. 12)


Figure 13: Photo of the SLS liquid hydrogen tank test in the test stand at NASA/MSFC in Huntsville, Alabama (image credit: NASA/Tyler Martin)

• December 14, 2018: Technicians at NASA's Michoud Assembly Facility in New Orleans, moved the largest piece of structural test hardware for America's new deep space rocket, the Space Launch System, from the factory to the dock where it was loaded onto NASA's barge Pegasus on 14 December 2018. 13)

- The liquid hydrogen tank test article will make its way up the river to NASA's Marshall Space Flight Center in Huntsville, Alabama, where dozens of hydraulic cylinders in Test Stand 4693 will push and pull on the giant tank, subjecting it to the same stresses and loads it will endure during liftoff and flight. The test hardware is structurally identical to the flight version of the liquid hydrogen tank that will comprise two-thirds of the core stage and hold 537,000 gallons of liquid hydrogen cooled to minus 423 degrees Fahrenheit (20.4 K).


Figure 14: Photo of the SLS liquid hydrogen tank test article transport at the Michoud Assembly Facility (image credit: NASA/Steven Seipel)

• December 13, 2018: Northrop Grumman Corporation along with NASA and Lockheed Martin successfully performed a ground firing test of the abort motor for NASA's Orion spacecraft LAS (Launch Abort System) at Northrop Grumman's facility in Promontory, Utah (Figure 15). The abort motor is a major part of the LAS, which provides an enhancement in spaceflight safety for astronauts. The completion of this milestone brings Orion one step closer to its first flight atop NASA's Space Launch System and to enabling humans to explore the moon, Mars and other deep space destinations beyond low-Earth orbit. 14)

- "Our astronauts' safety is our top priority," said Steve Sara, director, launch abort motor program, Northrop Grumman. "We never expect the launch abort motor to be used, but just like an ejection seat in a fighter pilot's aircraft, if they need it, it needs to work every time."

- The mission for Orion's LAS is to safely jettison the spacecraft and crew out of harm's way in the event of an emergency on the launch pad or during initial launch ascent. Today's abort motor test, Qualification Motor-2, was the culmination of a series of component tests conducted over the past few years in preparation for qualification. Data from the test will confirm the motor can activate within milliseconds and will perform as designed under cold temperatures.

- The abort motor, which stands over 17 feet tall and spans three feet in diameter, has a manifold with four exhaust nozzles. With its nozzles pointing skyward, it fired for five seconds; the exhaust plume flames reached approximately 100 feet in height. The high-impulse motor burns three times faster than a typical motor of this size, delivering the thrust needed to pull the crew module to safety. The motor achieved approximately 350,000 pounds of thrust (1556 kN) in one eighth of a second, as expected. More analysis will be performed in the coming weeks, but all initial results indicate a successful test.

- Northrop Grumman's next major abort motor milestones include the Ascent Abort-2 Flight Test (AA-2) set to take place at Cape Canaveral Air Force Station, Florida, in 2019. Previous large-scale tests of the launch abort motor included a development motor test in 2008, a pad abort test of the complete launch abort system in 2010 and the Qualification Motor-1 static test in 2017.

- For the AA-2 flight test, in addition to the launch abort motor Northrop Grumman will also provide the ATB (Abort Test Booster ), which will launch NASA's Orion spacecraft and LAS to on a preplanned trajectory to obtain data to be used for LAS performance assessment. The ATB uses the same rocket motor as the first stage of a Minotaur IV rocket.

- Northrop Grumman is responsible for the launch abort motor through a contract to Lockheed Martin, Orion's prime contractor. The Orion LAS program is managed out of NASA's Langley Research Center in Virginia. Northrop Grumman produces the abort motor at its Magna, Utah facility and the attitude control motor at its Elkton, Maryland facility. The company also manufactures the composite case for the abort motor at its facility in Clearfield, Utah.


Figure 15: Today's test firing of the Northrop Grumman-manufactured launch abort motor in Promontory, Utah, confirmed the motor can activate within milliseconds and will perform as designed under cold temperatures (image credit: Northrop Grumman, NASA)

• August 2018: Upper Stage and Adapters: At the forward section of the rocket, just below the Orion crew vehicle, is the OSA (Orion Stage Adapter), which holds the secondary payload accommodations. For EM-1, the OSA is complete and was delivered to EGS in February 2018. Made of a lightweight aluminum alloy, the OSA measures 5.4 m in diameter by 1.5 m high. A diaphragm just below the mounting brackets prevents launch gases from entering the Orion spacecraft. 15)

- Sitting just below the OSA, the ICPS (Interim Cryogenic Propulsion Stage), a modified Delta Cryogenic Second Stage manufactured by ULA in Decatur, Ala. through a contract with Boeing, supplies in-space propulsion for the Block 1 vehicle. The ICPS will provide the TLI burn to send Orion toward the moon during the EM-1 mission. After entering its disposal trajectory with the OSA attached, the ICPS will release the first seven CubeSats (Figure NO TAG#).


Figure 16: Photo of the ICPS, which will provide in-space propulsion for the first integrated flight of SLS and Orion, is complete (image credit: NASA)

• August 14, 2018: NASA Administrator Jim Bridenstine made his first official visit to NASA's rocket factory, the Michoud Assembly Facility in New Orleans, Louisiana, on Aug. 13, for tours and briefings on progress building the Space Launch System rocket and Orion spacecraft. 16)


Figure 17: NASA Administrator Jim Bridenstine speaks with members of the media in front of the massive liquid hydrogen tank, which comprises almost two-thirds of the core stage and holds 537,000 gallons (2032 cm3) of liquid hydrogen cooled to minus 423º Fahrenheit (-252ºC). Innovative processes are part of core stage manufacturing including joining the thickest pieces of aluminum ever with self-reacting friction stir welding. The liquid oxygen tank and liquid hydrogen tanks have the thickest joints ever made with self-reacting friction stir welding (image credit: NASA, Jude Guidry)

- Bridenstine, joined by Jody Singer, acting director of NASA's Marshall Space Flight Center and Keith Hefner, director of Michoud, toured the massive facility where manufacturing and assembly of the largest and most complex parts of SLS and Orion are underway. SLS will send the Orion spacecraft, astronauts and critical hardware on bold exploration missions to the Moon and beyond.

- The tour highlighted the SLS core stage which, flanked by two solid rocket boosters, will provide the thrust to propel the vehicle to deep space. The administrator had the opportunity to view SLS hardware just as engineers are putting the finishing touches on the core stage parts by testing avionics, installing special equipment inside the structures and applying thermal protection systems.

- Bridenstine also viewed Orion's latest milestone, the welding completion of the primary structure of the crew module, or pressure vessel, by engineers at Michoud. The pressure vessel is the primary structure that holds the pressurized atmosphere astronauts will breathe to allow them to work in the harsh environment of deep space. This pressure vessel will carry the first astronauts to missions beyond the Moon on Exploration Mission-2.

- "This is a critical piece of America's architecture for our return to the Moon and ultimately, it's a strategic capability for the United States of America," said Bridenstine. "I cannot overstate how important this capability is to America and how all of the team members who work here are contributing to a capability where countries around the world are seeking to partner with the United States as we return to the surface of the Moon and into orbit around the Moon."

• July 31, 2018: The first major piece of core stage hardware for NASA's SLS (Space Launch System) rocket has been assembled and is ready to be joined with other hardware for Exploration Mission-1. The forward skirt will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics. 17)


Figure 18: The first major piece of core stage hardware for NASA's Space Launch System rocket has been assembled and is ready to be joined with other hardware for Exploration Mission-1. The forward skirt will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics (image credit: NASA, Eric Bordelon)

- The backbone of the world's most powerful rocket, the 212-foot-tall (64.6 m) core stage, will contain the SLS rocket's four RS-25 rocket engines, propellant tanks, flight computers and much more. Though the smallest part of the core stage, the forward skirt will serve two critical roles. It will connect the upper part of the rocket to the core stage and house many of the flight computers, or avionics.

- "Completion of the core stage forward skirt is a major step in NASA's progress to the launch pad," said Deborah Bagdigian, lead manager for the forward skirt at the agency's Marshall Space Flight Center in Huntsville, Alabama. "We're putting into practice the steps and processes needed to assemble the largest rocket stage ever built. With the forward skirt, we are improving and refining how we'll conduct final assembly of the rest of the rocket."

- On July 24, the forward skirt assembly was wrapped up with the installation of all its parts. As part of forward skirt testing, the flight computers came to life for the first time as NASA engineers tested critical avionic systems that will control the rocket's flight. The construction, assembly and avionics testing occurred at NASA's Michoud Assembly Facility in New Orleans.

- Located throughout the core stage, the avionics are the rocket's "brains," controlling navigation and communication during launch and flight. It is critical that each of the avionics units is installed correctly, work as expected and communicate with each other and other components, including the Orion spacecraft and ground support systems.

- "It was amazing to see the computers come to life for the first time" said Lisa Espy, lead test engineer for SLS core stage avionics. "These are the computers that will control the rocket as it soars off the pad for Exploration Mission-1."

- The forward skirt test series was the first of many that will verify the rocket's avionics will work as expected during launch. The tests show the forward skirt was built correctly, and that all components and wiring on the inside have been put together and connected properly and are sending data over the lines as expected.

- The avionic computers ran "built-in tests" that Espy compares to the internal diagnostic tests performed by an automobile when first started. All of the health and data status reports came back as expected. The tests were a success and did not return any error codes. Such error codes would be similar to a check engine light on a car.

- The successful tests give the team the confidence needed to move forward with avionics installations in the core stage intertank and engine section. With more hardware and more interfaces, the installation in the intertank will be more complex, and the complexity will ramp up even more as the team moves to the engine section, introducing hydraulics and other hardware needed for the rocket's engines.

- Engineers will perform standalone tests on each component as they are completed. Once the forward and aft joins are integrated, they will perform a final integrated function test, testing all the core stage's avionics together.

- The fully integrated core stage and its four RS-25 engines will then be fired up during a final test before launch. At NASA's Kennedy Space Center in Florida, the core stage will be stacked with the upper part of the rocket, including Orion, and joined to the rocket's twin solid rocket boosters, in preparation for EM-1.

• July 10, 2018: Aerojet Rocketdyne recently passed a key milestone in preparation for the Ascent Abort Test (AA-2) next year with the successful casting of the Jettison Motor for the Lockheed Martin-built Orion spacecraft's LAS (Launch Abort System). AA-2 is a full-stress test of NASA's Orion LAS, which includes the Jettison Motor built by Aerojet Rocketdyne. The Orion Jettison Motor is used to separate the LAS from Orion as it makes its way to space and is the only motor on the escape system to activate in all mission scenarios. 18)


Figure 19: The Jettison Motor built by Aerojet Rocketdyne for the Lockheed Martin-built Orion spacecraft's LAS (Launch Abort System) that will be tested during the Ascent Abort Test (AA-2) next year (image credit: Aerojet Rocketdyne)

- In the unlikely event of an emergency on the launch pad or during ascent, the LAS would activate within milliseconds to whisk Orion and its astronaut crew to safety. Once Orion reaches a safe distance from the rocket, the Orion Jettison Motor would ignite to separate the LAS structure from the spacecraft, which could then deploy its parachutes for a safe landing.

- During the AA-2 test, a solid rocket booster will launch a fully functional LAS and an Orion test vehicle to an altitude of 31,000 feet (~9.5 km) at Mach 1.3 (over 1,000 mph) to test out the functionality of the LAS system prior to flying humans. The Jettison Motor will fire last in the test sequence.

- "Every time our engineers work on products supporting the Orion spacecraft or the Space Launch System rocket, they have astronaut safety front and center of mind," said Aerojet Rocketdyne CEO and President Eileen Drake. "The AA-2 test is a critical step to testing the Launch Abort System and our Jettison Motor and ensuring our astronauts always return home safely to their families."

- The Orion Jettison Motor, which generates 40,000 pounds of thrust (177.928 kN), uses a propellant that is poured into a motor casing, where it cures over a period of several days to form a solid, stable cast that burns in a precisely controlled fashion.

- The AA-2 Jettison Motor casting took place at Aerojet Rocketdyne's motor production facility in Sacramento, California. The completed motor will now be shipped to NASA's Kennedy Space Center for integration with the LAS by Lockheed Martin.

• April 3, 2018: NASA's Super Guppy aircraft prepares to depart the U.S. Army's Redstone Airfield in Huntsville, Alabama, April 3, with flight hardware for NASA's Space Launch System – the agency's new, deep-space rocket that will enable astronauts to begin their journey to explore destinations far into the solar system. The Orion stage adapter, the top of the rocket that connects SLS to Orion is loaded into the Guppy, which will deliver it to NASA's Kennedy Space Center in Florida for flight preparations. On Exploration Mission-1, the first integrated flight of SLS and the Orion spacecraft, the adapter will carry 13 CubeSats as secondary payloads. SLS will send Orion beyond the Moon, about 280,000 miles from Earth. This is farther from Earth than any spacecraft built for humans has ever traveled. 19)


Figure 20: SLS flight hardware is being transported in a Super Guppy from Huntsville AL to KSC (Kennedy Space Center) in Florida (image credit: NASA/MSFC, Fred Deaton)

• December 22, 2017: The booster avionics system for the SLS (Space Launch System) rocket completed system-level qualification testing in October 2017. Engineers simulated the booster avionics operations in a systems integration lab at NASA's Marshall Space Flight Center in Huntsville, Alabama, where all the avionics boxes and electronics were tested. The tests verified the fidelity of the system. Two five-segment rocket boosters, developed by Orbital ATK, will provide 80 percent of the thrust for the first two minutes of flight. The booster avionics, receiving commands from the SLS flight computers in the core stage, provide 80 percent of the control authority for the rocket during the first two minutes of flight. Key interactions confirmed during qualification testing included the ability to initiate booster ignition, control the booster during flight, terminate flight, and triggering core stage separation. 20)

• December 15, 2017: When NASA's Orion spacecraft hurtles toward Earth's surface during its return from deep-space missions, the capsule's system of 11 parachutes will assemble itself in the air and slow the spacecraft from 300 mph to a relatively gentle 20 mph for splashdown in the Pacific Ocean in the span of about 10 minutes. As the astronauts inside descend toward the water on future missions, their lives will be hanging by a series of threads that have been thoroughly ruggedized, tested and validated to ensure the parachute-assisted end of Orion missions are a success. 21)

- Through a series of tests in the Arizona desert, the engineers refining Orion's parachutes have made the road to certifying them for flights with astronauts look easy, including a successful qualification test Dec. 13 that evaluated a failure case in which only two of the systems three orange and white main parachutes deploy after several other parachutes in the system used to slow and stabilize Orion endure high aerodynamic stresses. But behind the scenes, engineers are working hard to understand and perfect the system that must be able to work across a broad range of potential environmental conditions and bring the crew home.

- While Orion's parachutes may look similar to those used during the Apollo-era to the untrained eye, engineers can't simply take that parachute system and scale it up to accommodate Orion's much larger size. Through testing and analysis, technicians have developed Orion's parachutes to be lighter, better understood and more capable than Apollo's. NASA has also been able to adjust the system as elements of the spacecraft, such as attachment points, have matured.

- "Through our testing, we've addressed some known failures that can happen in complex parachute systems to make the system more reliable," said Koki Machin, chief engineer for the system. "We built upon the strong foundation laid by Apollo engineers and figured out how to manage the stresses on the system during deployment more efficiently, decrease the mass of the parachutes by using high tech fabric materials rather than metal cables for the risers that attach the parachute to the spacecraft, and improve how we pack the parachute into Orion so they deploy more reliably."

- Orion's parachute system is also incredibly complex. About 10 miles of Kevlar lines attach the spacecraft to the outer rim of nearly 12,000 square feet (~1110 m2) of parachute canopy material – over four times the average square footage of a house – and must not get tangled during deployment. In addition to the fabric parachutes themselves, there are cannon-like mortars that fire to release different parachutes. Embedded in several parachutes are fuses set to burn at specific times that ignite charges to push blades through bullet proof materials at precise moments, slowly unfurling the parachutes to continue the sequential phases of the deployment sequence. All of these elements must be developed to be reliable for the various angles, wind conditions and speeds in which Orion could land.

- With the analysis capabilities that exist today and the historical data available, engineers have determined that approximately 20-25 tests, rather than the more than 100 performed during the Apollo era, will give them enough opportunities to find areas of weakness in Orion's parachute system and fix them. After the three remaining final tests next year, the system will be qualified for missions with astronauts.

- "There are things we can model with computers and those we can't. We have to verify the latter through repeated system tests by dropping a test article out of a military aircraft from miles in altitude and pushing the parachutes to their various limits," said CJ Johnson, project manager for the parachute system. "Lots of subtle changes can affect parachute performance and the testing we do helps us account for the broad range of possible environments the parachutes will have to operate in."

- Orion parachute engineers have also provided data and insight from the tests to NASA's Commercial Crew Program partners. NASA has matured computer modeling of how the system works in various scenarios and helped partner companies understand certain elements of parachute systems, such as seams and joints, for example. In some cases, NASA's work has provided enough information for the partners to reduce the need for some developmental parachute tests.

- "Orion's parachute system is an extremely lightweight, delicate collection of pieces that absolutely must act together simultaneously or it will fail," said Machin. "It alone, among all the equipment on the crew module, must assemble itself in mid-air at a variety of possible velocities and orientations."


Figure 21: NASA is testing Orion's parachutes to qualify the system for missions with astronauts (image credits: U.S. Army)

• November 8, 2017: NASA is providing an update on the first integrated launch of the Space Launch System (SLS) rocket and Orion spacecraft after completing a comprehensive review of the launch schedule. This uncrewed mission, known as Exploration Mission-1 (EM-1) is a critical flight test for the agency's human deep space exploration goals. EM-1 lays the foundation for the first crewed flight of SLS and Orion, as well as a regular cadence of missions thereafter near the Moon and beyond. 22)

- The review follows an earlier assessment where NASA evaluated the cost, risk and technical factors of adding crew to the mission, but ultimately affirmed the original plan to fly EM-1 uncrewed. NASA initiated this review as a result of the crew study and challenges related to building the core stage of the world's most powerful rocket for the first time, issues with manufacturing and supplying Orion's first European service module, and tornado damage at the agency's Michoud Assembly Facility in New Orleans.

- "While the review of the possible manufacturing and production schedule risks indicate a launch date of June 2020, the agency is managing to December 2019," said acting NASA Administrator Robert Lightfoot. "Since several of the key risks identified have not been actually realized, we are able to put in place mitigation strategies for those risks to protect the December 2019 date."

- The majority of work on NASA's new deep space exploration systems is on track. The agency is using lessons learned from first time builds to drive efficiencies into overall production and operations planning. To address schedule risks identified in the review, NASA established new production performance milestones for the SLS core stage to increase confidence for future hardware builds. NASA and its contractors are supporting ESA's (European Space Agency) efforts to optimize build plans for schedule flexibility if sub-contractor deliveries for the service module are late.

- NASA's ability to meet its agency baseline commitments to EM-1 cost, which includes SLS and ground systems, currently remains within original targets. The costs for EM-1 up to a possible June 2020 launch date remain within the 15 percent limit for SLS and are slightly above for ground systems. NASA's cost commitment for Orion is through Exploration Mission-2. With NASA's multi-mission approach to deep space exploration, the agency has hardware in production for the first and second missions, and is gearing up for the third flight. When teams complete hardware for one flight, they're moving on to the next.

- As part of the review, NASA now plans to accelerate a test of Orion's launch abort system ahead of EM-1, and is targeting April 2019. Known as Ascent-Abort 2, the test will validate the launch abort system's ability to get crew to safety if needed during ascent. Moving up the test date ahead of EM-1 will reduce risk for the first flight with crew, which remains on track for 2023.

• November 8, 2017: Lift off at the end of the countdown is just the first phase in a launch. Two minutes in, booster separation occurs ­– a critical stage in flight, with little room for error. Engineers at NASA's Langley Research Center in Hampton, Virginia, are doing their part to support NASA's new deep space rocket, the SLS (Space Launch System). The rocket will be capable of sending the Orion crew vehicle and other large cargos on bold new missions beyond Earth orbit. To understand the aerodynamic forces as booster separation motors fire and push the solid rocket boosters away from the rocket's core, Langley engineers are testing a 35-inch SLS model in Block 1B 105-metric ton evolved configuration in the Unitary Plan Wind Tunnel using a distinct pink paint. The pressure-sensitive paint works by reacting with oxygen to fluoresce at differing intensities, which is captured by cameras in the wind tunnel. Researchers use that data to determine the airflow over the model and which areas are seeing the highest pressure. 23)


Figure 22: Wind tunnel test of the SLS booster separation model in Block 1B (image credit: NASA/LaRC)

• October 19, 2017: NASA engineers conducted a full-duration, 500-second test of RS-25 flight engine E2063 on the A-1 Test Stand at SSC (Stennis Space Center) on Oct. 19, 2017. Once certified, the engine is scheduled to help power NASA's new Space Launch System rocket on its EM-2 (Exploration Mission-2). The test was part of Founders Day Open House activities at Stennis. 24)

- Engine E2063 is scheduled for use on NASA's second mission of SLS and Orion, known as EM-2. The first integrated flight test of SLS and Orion, EM-1 (Exploration Mission-1), will be an uncrewed final test of the rocket and its systems. The EM-2 flight will be the first to carry astronauts aboard the Orion spacecraft, marking the return of humans to deep space for the first time in more than 40 years.

• September 22, 2017: Following a series of issues over the last year with the Core Stage for the first flight of the Space Launch System rocket, the launch dates for both the EM-1 and EM-2 flights are beginning to align, with EM-1 now targeting 'No Earlier Than' 15 December 2019 and EM-2 following on 1 June 2022. Additionally, the EM-3 flight has gained its first notional mission outline, detailing a flight to Near-Rectilinear Halo Orbit to deploy the Hab (Habitat) module for the new Deep Space Gateway. 25)

- The first flight of any new rocket is bound to encounter design and initial production delays. And NASA's SLS (Space Launch System ) rocket is been no stranger to those sort of anticipated effects. - Following a misalignment in the installation of the main welding machine at the Michoud Assembly Facility (MAF), welding for the certification elements for the new SLS core stage Liquid Hydrogen (LH2) and Liquid Oxygen (LOX) tanks picked up.

- After the initial LH2 qualification tanks were welded, a change to the welding machine's pin was made – a change that resulted in segment welds on the EM-1 LH2 flight tank being too brittle to meet flight specification requirements.

- This pin change and subsequent issue led to the understanding that the LH2 flight tank for EM-1 was no longer flight worthy and thus could not be used for EM-1.

- A plan was then put in place to restore the welding machine's previously used pin – the one that welded all the Core Stage test articles that have thus far passed all qualification and acceptance testing – and use the upcoming weld for the EM-2 flight LH2 tank as the new LH2 tank for the EM-1 flight.

- However, less than a week after the EM-1 LH2 flight tank issue became known, a worker at MAF damaged the aft dome section of the qualification article for the Core Stage LOX tank.

- In all, these production issues quickly made the Core Stage's timeline for EM-1's then-2018 launch date impossible.

- Earlier this year, NASA acknowledged this and announced that EM-1 was slipping to sometime in 2019 – though that was already understood to be "Q4 2019."


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The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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