Space Launch System
Artist's rendering of the SLS Block 1 crewed variant launching
|Country of origin||United States|
|Cost per launch ()||$500 million |
|Diameter||8.4 m (core stage)|
|70,000 to 130,000 kg (150,000 to 290,000 lb)|
|Family||Shuttle-Derived Launch Vehicles|
|Launch sites||LC-39, Kennedy Space Center|
|First flight||17 December 2017|
|Notable payloads||Orion MPCV|
|Boosters (Block I)|
|No boosters||2 Space Shuttle Solid Rocket Boosters
|Thrust||16,013.6 kN (3,600,000 lbf)|
|Total thrust||32,027.2 kN (7,200,000 lbf)|
|Specific impulse||269 seconds|
|Burn time||124 seconds|
|First Stage (Block I) - Core Stage|
|Diameter||8.4 m (330 in)|
|Empty mass||85.270 kg|
|Gross mass||979.452 kg|
|Thrust||7,440 kN (1,670,000 lbf)|
|Specific impulse||363 seconds (sea level), 452 seconds (vacuum)|
|First Stage (Block IA/II) - Core Stage|
|Diameter||8.4 m (330 in)|
|Thrust||7,440 kN (1,670,000 lbf)|
|Specific impulse||363 seconds (sea level)|
|Second Stage (Block I) - ICPS|
|Length||13.7 m (540 in)|
|Diameter||5 m (200 in)|
|Empty mass||3,490 kg (7,690 lb)|
|Gross mass||30,710 kg (67,700 lb)|
|Thrust||110.1 kN (24,800 lbf)|
|Specific impulse||462 seconds|
|Burn time||1125 seconds|
|Second Stage (Block II) - Earth Departure Stage|
|Thrust||3,930 kN (880,000 lbf)|
|Specific impulse||448 seconds (vacuum)|
The Space Launch System (SLS) is a United States Space Shuttle-derived heavy launch vehicle being designed by NASA. It follows the cancellation of the Constellation Program, and is to replace the retired Space Shuttle. The NASA Authorization Act of 2010 envisions the transformation of the Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo.
The SLS launch vehicle is to be upgraded over time with more powerful versions. Its initial Block I version, without an upper stage, is to lift a payload of 70 metric tons to orbit. The final Block II version with an integrated upper Earth Departure Stage is to have, depending on the configuration, a payload lift capability of at least 130 metric tons to low earth orbit, 12 metric tons above that of Saturn V, which would make the SLS the most capable heavy lift vehicle ever built.
SLS is to be capable of lifting astronauts and hardware to near-Earth destinations such as asteroids, the Moon, Mars, and most of the Earth's Lagrangian points. SLS may also support trips to the International Space Station, if necessary. The SLS program is integrated with NASA's Orion Crew and Service Module, with astronauts returning to earth in a capsule-shaped, four-person crew module. SLS will use the ground operations and launch facilities at NASA's Kennedy Space Center, Florida.
Design and development
On September 14, 2011, NASA announced its design selection for the new launch system, declaring that it would take the agency's astronauts farther into space than ever before and provide the cornerstone for future US human space exploration efforts. Since the announcement, four versions of the launch vehicle have been revealed – Blocks 0, I, IA and II. Each configuration utilizes different core stages, boosters and upper stages, with some components deriving directly from Space Shuttle hardware and others being developed specifically for the SLS. Later versions will use five RS-25E engines with upgraded boosters and an 8.4-meter diameter upper stage with three J-2X engines. A 5-meter class fairing with a length of 10 m or greater is being considered for allowing heavy payloads for deep space missions. The initial Block I two-stage variant will have a lift capability of between 70,000 and 77,000 kg, while the proposed Block II final variant will have similar lift capacity and height to the original Saturn V. By November 2011, NASA had selected five rocket configurations for wind tunnel testing, described in three Low Earth Orbit classes; 70 metric tons (t), 95 t, and 140 t.
On July 31, 2013 the SLS passed the Preliminary Design Review (PDR), the review encompassed all aspects of the SLS' design, not only the rocket and boosters but also ground support and logistical arrangements. Successful completion of the PDR paves the way for Gate-C approval by NASA senior administration, this would enable the project to move from design to implementation.
The core stage of the SLS is common to all vehicle configurations, essentially consisting of a modified Space Shuttle External Tank with the aft section adapted to accept the rocket's Main Propulsion System (MPS) and the top converted to host an interstage structure. It will be fabricated at the Michoud Assembly Facility. The stage will utilize varying numbers and versions of the RS-25 engine depending on the configuration to be used:
- Block 0: ET core stage (not stretched) with three RS-25D engines. Initial planning baseline, from Shuttle components. However, NASA managers showed a preference of using four RS-25 engines in the Block 0 configuration as it would remove the need to substantially redesign the core stage when moving to Block I.
- Block I: Stretched core stage with four RS-25D engines.
- Block IB: Stretched core stage with four RS-25D/E engines.
- Block 1A, II: Stretched core stage with four RS-25E engines and two advanced rocket boosters. Initially Block II was being designed to use five RS-25D/E engines, but NASA now lists four, like Block I.
In addition to the thrust produced by the engines on the core stage, the first two minutes of flight will be aided by two rocket boosters mounted either side of the core stage. Early configurations (Blocks 0 and I) of the SLS are set to use modified Space Shuttle Solid Rocket Boosters (SRBs), with either four or five segments depending on configuration. These boosters will not be recovered and will sink into the Atlantic Ocean downrange. The boosters for Block IA and Block II configurations will use upgraded boosters from the selection of improved booster bids. These may be of either the solid rocket or liquid rocket booster type.
Alliant Techsystems (ATK), the builder of the Space Shuttle SRBs, has completed three full-scale, full-duration static tests of the five-segment rocket booster that will be used in Blocks 0 and I. Development motor (DM-1) was successfully tested on September 10, 2009; DM-2 on August 31, 2010 and DM-3 on September 8, 2011. For DM-2 the motor was cooled to a core temperature of 40 degrees Fahrenheit (4 degrees Celsius), and for DM-3 it was heated to above 90 °F (32 °C). In addition to other objectives, these tests validated motor performance at extreme temperatures. Each five-segment SRB has a thrust of 3,600,000 lbf (16 MN) at sea level.
For SLS Block II, NASA has begun the Advanced Booster Competition that is expected to end in 2015. On June 17, 2011, Aerojet announced a strategic partnership with Teledyne Brown to develop and produce a domestic version of an uprated Soviet NK-33 LOX/RP-1 engine, an engine derived from the NK-15 initially designed to lift the unsuccessful N-1 Soviet moonshot vehicle, with each engine's thrust increased from 394,000 lbf (1.75 MN) to at least 500,000 lbf (2.2 MN) at sea level. This booster, with eight AJ-26-500, or four AJ-1E6 engines is to compete against the Shuttle-derived solid rocket booster for the later Blocks of the SLS launch vehicle. On February 14, 2013, NASA awarded a $23.3 million 30-month contract Aerojet to build a full-scale 550,000-pound thrust class main injector and thrust chamber to be used in the advanced booster. Two standard Aerojet AJ-26 engines, together producing a combined 735,000 lbf (3.27 MN) of sea level thrust, successfully lifted the Antares rocket in 2013.
Pratt & Whitney Rocketdyne, and Dynetics have entered the competition with a booster design known as "Pyrios", which would use two F-1B engines derived from the F-1 LOX/RP-1 engine that powered the first stage of the Saturn V vehicle in the Apollo program. In 2012 it was determined that if the dual-engined Pyrios booster was selected for the SLS Block II, the payload could be 150 metric tons (t) to Low Earth Orbit, 20 t more than the baseline 130 t to LEO for SLS Block II. In 2013, it was reported that in comparison to the F-1 engine that it is derived from, the F-1B engine is to have improved efficiency, be more cost effective and have fewer engine parts. Each F-1B is to produce 1,800,000 lbf (8.0 MN) of thrust at sea level, an increase over the 1,550,000 lbf (6.9 MN) of thrust of the initial F-1 engine.
ATK is proposing an advanced SRB named "Dark Knight" with more energetic propellant, a lighter composite case, and other design improvements to reduce costs and improve performance. ATK states it provides "capability for the SLS to achieve 130 t payload with significant margin" when combined with a Block II core stage containing five RS-25 engines. However, the advanced SRB is to achieve no more than 113 t to low earth orbit with the current core stage with four RS-25 engines for Block I and Block II vehicles.
Christopher Crumbly, manager of NASA’s SLS advanced development office in January 2013 commented on the booster competition, "The F-1 has great advantages because it is a gas generator and has a very simple cycle. The oxygen-rich staged combustion cycle [Aerojet’s engine] has great advantages because it has a higher specific impulse. The Russians have been flying ox[ygen]-rich for a long time. Either one can work. The solids [of ATK] can work."
- Block 0 – No upper stage.
- Block I – Either no upper stage or a modified Delta Cryogenic Second Stage (DCSS), referred to as the Interim Cryogenic Propulsion Stage (ICPS); the DCSS is used on the Delta IV vehicle and has one RL10 engine. This 70-metric ton to low earth orbit (some sources claim over 90 metric tons) configuration is to fly two missions: Exploration Mission 1 (EM-1) in 2017 and Exploration Mission 2 (EM-2) in 2021. The Centaur upper stage with two RL10 engines of the Atlas V vehicle was also a noted option, before the Delta IV DCSS was selected in May 2012. In 2013, a Boeing analysis of the performance of 3 Large Upper Stage (LUS) options, incorporated into a Block I SLS vehicle with standard five-segment solid rocket boosters, determined that in comparison to the baseline Block I SLS with a ICPS upper stage, which will be capable of delivering 70 t to low earth orbit (LEO), 20.2 t to Trans-Mars Injection(TMI) and 2.9 t to Europa:
- A 4 engined RL10 LUS option would be capable of delivering 93.1 t to LEO, 31.7 t to TMI and 8.1 t to Europa.
- A 2 engined MB60 (an engine comparable to the RL60) LUS could deliver 97 t to LEO, 32.6 t to TMI and 8.5 t to Europa.
- While a single J-2X engine, with its higher thrust than all previous LUS options, could deliver 105.2 t to LEO but the engine's slightly lower specific impulse in comparison to the RL10 and its RL60 derivative would ensure that its long range capability would be marginally lower than the previous two options, with this translating into 31.6 t to TMI and 7.1 to Europa.
- Block IA – No upper stage for LEO missions. For Beyond Earth Orbit or Lunar missions, either the Interim Cryogenic Propulsion Stage or the large Cryogenic Propulsion Stage, which would be powered by two to four RL-10 engines would be used. This stage would only function as an in-space stage and would help little during launch. This configuration would lift between 105 and 120 metric tons to LEO, depending on the boosters used.
- Block IB - Dual Use Upper Stage (DUUS) consisting of four RL10 engines, with a 8.4 m fairing and a launch aim of 105 metric tons to LEO. The DUUS is to complete the SLS ascent phase and operate as an "In-Space Stage".
- Block II – A fully-fledged Earth Departure Stage, initially this was to be powered by two or three J-2X engines operating in the vehicles second stage. However, as of 2013, NASA depicts the Block II second stage with two J-2X engines. The J-2X-equipped Block II second stage will be approximately 80 feet (24 m) in length. One other Block II configuration under study is similar to the Block IB configuration in that it includes the Dual-Use Upper Stage (DUUS – pronounced “Duce”) to push massive payloads beyond earth orbit. The DUUS has four RL10 engines (or two improved thrust derivatives of the RL10 engine, such as the RL60). The Block II DUUS would possibly replace the higher thrust J-2X engines as the second stage, or alternatively be used atop an entirely separate third stage. The DUUS option is being considered as it may further reduce costs.
Studies through 2012 indicated that a heavy-lift rocket capable of delivering approximately 140 t to LEO is needed for NASA's manned mission to Mars. The third stage, beyond LEO engine, for the interplanetary leg of this mission, tasked with transporting cargo and crew from earth orbit to Mars orbit, and back, is being studied at Marshall Space Flight Center with project simulations on nuclear thermal rocket (NTR) engines and the goal of developing a Nuclear Cryogenic Propulsion Stage. The project will see rocket engines at least twice as efficient as their most efficient chemical counterparts, a level of thrust and efficiency required for propelling the necessary mass of cargo to support exploration during crewed missions to Mars and beyond. NTR engines, such as the Pewee of Project Rover, were selected in the Mars Design Reference Architecture (DRA).
Prior to launch the SLS will have the ability to tolerate a minimum of 13 tanking cycles due to launch scrubs and other launch delays. The assembled rocket is to be able to remain at the launch pad for a minimum of 180 days and can remain in stacked configuration for at least 200 days without destacking.
During the joint Senate-NASA presentation in September 2011, it was stated that the SLS program has a projected development cost of $18 billion through 2017, with $10bn for the SLS rocket, $6bn for the Orion Multi-Purpose Crew Vehicle and $2bn for upgrades to the launch pad and other facilities at Kennedy Space Center. These costs and schedule are considered optimistic by Booz Allen Hamilton, which conducted an independent cost assessment for NASA. An unofficial NASA document estimated the cost of the program through 2025 to total at least $41bn for four 70 t launches (1 unmanned in 2017, 3 manned starting in 2021), with the 130 t version ready no earlier than 2030. HEFT estimate Block 0 unit cost at $1.6 billion and Block 1 at $1.86 billion.
NASA SLS deputy project manager Jody Singer of the Marshall Space Flight Center in Huntsville, AL stated in September 2012 that $500 million per launch is a reasonable target cost for SLS, with a relatively minor dependence of costs on launch capability.
Criticism of SLS falls in several areas. The Space Access Society, Space Frontier Foundation and the Planetary Society called for cancellation of the project, arguing that SLS will consume the funds for other projects from the NASA budget and will not reduce launch costs; some estimate this cost for the SLS to be about $8,500 per pound lifted to low earth orbit (LEO). U.S. Representative Dana Rohrabacher and others added that instead, a propellant depot should be developed and the Commercial Crew Development program accelerated. Two studies, one not publicly released from NASA and another from the Georgia Institute of Technology, show this option to be a possibly cheaper alternative.
Others suggest it will cost less to use an existing lower payload capacity rocket (Atlas V, Delta IV, Falcon 9, or the derivative Falcon Heavy), with on-orbit assembly and propellant depots as needed, rather than develop a new launch vehicle for space exploration without competition for the whole design. The Augustine commission proposed an option for a commercial 75 metric ton launcher with lower operating costs, and noted that a 40 to 60 t launcher can support lunar exploration.
Mars Society founder Robert Zubrin suggested that a heavy lift vehicle should be developed for $5 billion on fixed-price requests for proposal. Zubrin also disagrees with those that say the U.S. does not need a heavy-lift vehicle. Based upon extrapolations of increased payload lift capabilities from past experience with SpaceX's Falcon launch vehicles, SpaceX CEO Elon Musk guaranteed that his company could build the conceptual Falcon XX, a vehicle in the 140-150 t payload range, for $2.5 billion, or $300 million per launch, but cautioned that this price tag did not include a potential upper-stage upgrade.
Rep. Tom McClintock and other groups argue that the Congressional mandates forcing NASA to use Space Shuttle components for SLS amounts to a de-facto non-competitive, single source requirement assuring contracts to existing shuttle suppliers, and calling the Government Accountability Office (GAO) to investigate possible violations of the Competition in Contracting Act (CICA). Opponents of the heavy launch vehicle have critically used the name "Senate launch system". The Competitive Space Task Force, in September 2011, said that the new government launcher directly violates NASA’s charter, the Space Act, and the 1998 Commercial Space Act requirements for NASA to pursue the "fullest possible engagement of commercial providers" and to "seek and encourage, to the maximum extent possible, the fullest commercial use of space".
Proposed missions and schedule
- ISS Back-Up Crew Delivery – a single launch mission of up to four astronauts via a Block 1 SLS/Orion-MPCV without an Interim Cryogenic Propulsion Stage (ICPS) to the International Space Station (ISS) if the Commercial Crew Development program does not come to fruition. This potential mission mandated by the NASA Authorization Act of 2010 is deemed undesirable since the 70 t SLS and BEO Orion would be overpriced and overpowered for said mission requirements. Its current description is “delivers crew members and cargo to ISS if other vehicles are unable to perform that function. Mission length 216 mission days. 6 crewed days. Up to 210 days at the ISS.”
- Tactical Timeframe DRMs
- BEO Uncrewed Lunar Fly-by – Exploration Mission 1 (EM-1), a reclassification of SLS-1, is a single launch mission of a Block I SLS with ICPS and a Block 1 Orion MPCV (Multi-Purpose Crew Vehicle), with a destination of 70,000 km past the lunar surface, to be conducted by 2017. Its current description is “Uncrewed Lunar Flyby: Uncrewed mission Beyond Earth Orbit (BEO) to test critical mission events and demonstrate performance in relevant environments. Expected drivers include: SLS and ICPS performance, MPCV environments, MPCV re-entry speed, and BEO operations.”
- BEO Crewed Lunar Orbit – Exploration Mission 2 (EM-2), a reclassification of SLS-2, is a single launch mission of a Block I SLS with ICPS and lunar Block 1 Orion MPCV with a liftoff mass around 68.8 t with SLS’ Payload Insertion of 50.7 t, which would be a ten to fourteen day mission with a crew of four astronauts who would spend four days in lunar orbit. Its current description is “Crewed mission to enter lunar orbit, test critical mission events, and perform operations in relevant environments”. The destination for EM-2, as of 2013, is regarded to be a captured asteroid in lunar orbit, to be conducted by no later than 2021.
- Strategic Timeframe DRMs
- GEO mission – a dual launch mission separated by 180 days to Geostationary Orbit. The first launch would comprise an SLS with a CPS and cargo hauler, the second an SLS with a CPS and Orion MPCV. Both launches would have a mass of about 110 t.
- A set of lunar missions enabled in the early 2020s ranging from Earth Moon Lagrangian point-1 (EML-1) and low lunar orbit (LLO) to a lunar surface mission. These missions would lead to a lunar base combining commercial and international aspects.
- The first two missions would be single launches of SLS with a CPM and Orion MPCV to EML-1 or LLO and would have a mass of 90 t and 97.5 t respectively. The LLO mission is a crewed twelve day mission with three in Lunar orbit. Its current description is “Low Lunar Orbit (LLO): Crewed mission to LLO. Expected drivers include: SLS and CPS performance, MPCV re-entry speed, and LLO environment for MPCV”.
- The lunar surface mission set for the late 2020s would be a dual launch separated by 120 days. This would be a nineteen-day mission with seven days on the Moon's surface. The first launch would comprise an SLS with a CPS and lunar lander, the second an SLS with a CPS and Orion MPCV. Both would enter LLO for lunar orbit rendezvous prior to landing at equatorial or polar sites on the Moon. Launches would have masses of about 130 t and 108 t, respectively. Its current description is “Lunar Surface Sortie (LSS): Lands four crew members on the surface of the Moon in the equatorial or Polar Regions and returns them to Earth,” “Expected drivers include: MPCV operations in LLO environment, MPCV uncrewed ops phase, MPCV delta V requirements, RPOD (Rendezvous, Proximity Operations and Docking), MPCV number of habitable days.”
- Five Near Earth Asteroid (NEA) missions ranging from “Minimum” to “Full” capability are being studied. Among these are two NASA Near Earth Object (NEO) missions in 2026. A 155-day mission to NEO 1999 AO10, a 304-day mission to NEO 2001 GP2, a 490-day mission to a Potentially Hazardous Asteroid such as 2000 SG344, utilizing two Block IA/B SLS vehicles, and a Boeing proposed NEO mission to NEA 2008 EV5 in 2024. The latter would start from the proposed Earth-Moon L2 based Exploration Gateway Platform. Utilising a SLS third stage the trip would take about 100 days to arrive at the asteroid, 30 days for exploration, and a 235-day return trip to Earth.
- Forward Work Martian Moon Phobos/Deimos, a crewed Flexible Path mission to one of the Martian moons. It would include 40 days in the vicinity of Mars and a return Venus flyby.
- Forward Work Mars Landing, a crewed mission, with four to six astronauts, to a semi-permanent habitat for at least 540 days on the surface of the red planet in 2033 or 2045. The mission would include in-orbit assembly, with the launch of seven SLS block II heavy lift vehicles (HLVs) with a requirement of each being able to deliver 140 metric tons to low earth orbit (LEO). The seven HLV payloads, three of which would contain nuclear propulsion modules, would be assembled in LEO into three separate vehicles for the journey to Mars; one cargo In-Situ Resource Utilization Mars Lander Vehicle (MLV) created from two HLV payloads, one Habitat MLV created from two HLV payloads and a crewed Mars Transfer Vehicle (MTV), known as "Copernicus", assembled from three HLV payloads launched a number of months later. Nuclear Thermal Rocket engines such as the Pewee of Project Rover were selected in the Mars Design Reference Architecture (DRA) study as they met mission requirements being the preferred propulsion option because it is proven technology, has higher performance, lower launch mass, creates a versatile vehicle design, offers simple assembly, and has growth potential.
- Other proposed missions
- 2024+ Single Shot MSR on SLS, a crewed flight with a telerobotic Mars Sample Return (MSR) mission proposed by NASA's Mars Program Planning Group. The time frame suggests SLS-5, a 105 t Block 1A rocket to deliver an Orion capsule, SEP robotic vehicle, and Mars Ascent Vehicle (MAV). “Sample canister could be captured, inspected, encased and retrieved tele-robotically. Robot brings sample back and rendezvous with a crew vehicle." The mission may also include a “Possible Mars SEP (Solar Electric Power/Propulsion) Orbiter”.
- Potential sample return missions to Europa and Enceladus have also been noted.
- Deep Space Habitat (DSH), NASA's planned usage of spare ISS hardware, experience, and modules for future missions to asteroids, Earth-Moon Lagrangian point and Mars.
- Skylab II, proposal by Brand Griffin, an engineer with Gray Research Inc working with NASA Marshall, to use the upper stage hydrogen tank from SLS to build a 21st-century version of Skylab for future NASA missions to asteroids, Earth-Moon Lagrangian point-2 (EML2) and Mars.
- SLS DoD Missions, the HLV will be made available for Department of Defense and other US Government agencies to launch military or classified missions.
- Commercial payloads, such as the Bigelow Commercial Space Stations have also been referenced.
- Additionally “Secondary Payloads” mounted on SLS via an Encapsulated Secondary Payload Adapter (ESPA) ring could also be launched in conjunction with a "primary passenger" to maximize payloads.
- Monolithic telescope mission, SLS has been proposed by Boeing as a launch vehicle for the ATLAST Space Telescope. This could be an 8m monolithic telescope or a 16m deploy-able telescope at Earth-Sun L2.
- Solar probe mission, SLS has been proposed by Boeing as a launch vehicle for Solar Probe 2. This probe would be placed in a low perihelion orbit to investigate corona heating and solar wind acceleration to provide forecasting of solar radiation events.
- Uranus mission, SLS has been proposed by Boeing as a launch vehicle for a Uranian probe. The rocket would “Deliver a small payload into orbit around Uranus and a shallow probe into the planet’s atmosphere.” The mission would study the Uranian atmosphere, magnetic and thermal characteristics, gravitational harmonics as well as do flybys of Uranian moons.
A very preliminary and unofficial schedule based on a worst case budget has outlined some early SLS flights as:
|SLS-1/EM-1||December 2017||Block I||Send Orion/MPCV on unmanned trip around the Moon.|
|SLS-2/EM-2||2021||Block I||Send the Orion (spacecraft) with four members to an asteroid that had been robotically captured and placed in lunar orbit two years in advance.|
|SLS-3||August 2022||Block IA|
|SLS-4||August 2023||Block IA|
|SLS-5||August 2024||Block IA||Mars Sample Return Mission[specify]|
|SLS-6||August 2025||Block IA||Manned "Exploration" Mission: Orion BEO picks up Mars sample & returns to Earth|
|SLS-7||August 2026||Block IA||Cargo launch|
|SLS-8||August 2027||Block IA||Manned launch|
|SLS-9||August 2028||Block IA||Cargo launch|
|SLS-10||August 2029||Block IA||Manned launch|
|SLS-11||August 2030||Block IA||New configuration, Cargo launch|
|SLS-12||August 2031||Block IA||Manned mission|
|SLS-13||August 2032||Block II||New configuration, Cargo launch|
- Space Shuttle successors
- Comparison of orbital launchers families
- Comparison of orbital launch systems
- Exploration of Mars
- Manned mission to Mars
- Space policy of the Barack Obama administration
- Space Exploration Vehicle
- Saturn MLV, a modified super heavy lift Saturn V design of the late 1960s, designed for crewed Mars missions by the 1980s.
- Saturn V ELV, an enlarged Saturn V design concept of the late 1960s with strapon Titan IV solid rocket boosters.
- Saturn V-3, an upgraded Saturn V, another design concept of the late 1960s which would use F-1A 1st stage engines and HG-3 2nd stage engines.
- Ares V, the cargo vehicle design for the Constellation Program of the 2000s.
- DIRECT, a competitor to the Ares V, but with a lower and smaller payload capacity, it was to use the concept Jupiter (rocket family) of vehicles.
- Shuttle-Derived Heavy Lift Launch Vehicle, a concept vehicle that would have had a lower lift capability than the baseline Saturn V.
- Energia, a comparable vehicle to SLS Block I in terms of lift capability, but for Low Earth Orbit excursions.
- Nautilus-X, a proposed deep space habitat module.
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|Wikimedia Commons has media related to Space Launch System.|
- Space Launch System & Multi-Purpose Crew Vehicle page on NASA.gov
- "Preliminary Report on Multi-Purpose Crew Vehicle and Space Launch System" (PDF), NASA.
- SLS Future Frontiers video
- Video animations of mission to asteroid, moon and mars