Space Launch System (SLS)

Space Launch System (SLS) #1



Type: Launch vehicle.
Goals: Next generation launch system to take astronauts to Low Earth Orbit (LEO) and beyond.
Variants: Block 0 / Block 1 / Block 1A / Block 11
Project Tenure: 2010 - Present
Maiden Flight: Projected for 17 December 2017
Project Status: Ongoing


Diameter: Core Stage: 27 ft, 7 in (8.4 m)


Crew: Up to four
Payload: LEO: 150,000 - 280,000 lbs (70,000 - 129,000 kg)

Boosters (Block I)

Diameter: Unknown
No Boosters: 2x Space Shuttle Solid Rocket Boosters (5-Segment)
Engines: One
Thrust: 3,600,000 lbf (16,013.6 kN) each
Specific Impulse: 269 seconds
Fuel: Ammonium Perchlorate Composite Propellant (ADCP)

First Stage (Block I) - Core Stage

Diameter: 28 ft, 0 in (8.4 m)
Engines: 4x RS-25D Space Shuttle Main Engine (SSME)
Thrust: 1,670,000 lbf (7,440 kN) each
Specific Impulse: 363 seconds at Sea Level
Fuel: Liquid Hydrogen (LH2) and Liquid Oxygen (LOX)

First Stage (Block IA / II) - Core Stage

Diameter: 28 ft, 0 in (8.4 m)
Engines: 5x RS-25E Space Shuttle Main Engine (SSME)
Thrust: 2,100,000 lbf (9,300 kN)
Specific Impulse: 363 seconds at Sea Level
Fuel: Liquid Hydrogen (LH2) and Liquid Oxygen (LOX)

Second Stage (Block I) - Delta Cryogenic Second Stage (iCPS)

Diameter: 16 ft, 0 in (5.0 m)
Engines: 1x RL10B-2
Thrust: 24,800 lbf (30.710 kN)
Specific Impulse: 462 seconds
Fuel: Liquid Hydrogen (LH2) and Liquid Oxygen (LOX)

Second Stage (Block II) - Earth Departure Stage

Diameter: Unknown
Engines: 3x J-2X
Thrust: 880,000 lbf (3,930 kN)
Specific Impulse: 448 seconds
Fuel: Liquid Hydrogen (LH2) and Liquid Oxygen (LOX)


Space Launch System (SLS) #2 The Space Launch System, or 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. It is to be upgraded over time with more powerful versions. Its initial capability of the core elements, without an upper stage, will be between 70 metric tons (for the Block 0 configuration with 3 engines and a partially fuelled core) and 100 metric tons (for the Block I configuration with 4 engines and a fully fuelled core) to low-Earth orbit (LEO) in preparation for missions beyond low-Earth orbit. With the addition of an integrated upper Earth Departure Stage and a fifth SSME-derived core engine, the total lift capability is to be 130 metric tons.

Design and Development

Core Stage

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. The stage will utilise varying numbers and versions of the RS-25 engine depending on the configuration to be used:

  • Block 0 Unstretched core stage with 3 RS-25D engines
  • Block I Stretched core stage with 4 RS-25D engines
  • Block IA & II Stretched core stage with 5 RS-25E engines


In addition to the thrust produced by the engines on the core stage, for the first two minutes first stage flight will be aided by two booster rockets 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 4 or 5 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, however, will be upgraded from the basic boosters, with the selection upgraded booster bids. These boosters may be of either the solid or liquid-fuel type.

ATK, the builder of the Space Shuttle SRBs, has completed three full-scale, full-duration static tests of the five-segment booster that will be used in Blocks 0 & I. Development motor (DM-1) was successfully tested on 10 September 2009; DM-2 on 31 August 2010 and DM-3 on 8 September 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 degrees Fahrenheit (32 degrees Celsius). In addition to other objectives, these tests validated motor performance at extreme temperatures.

On 17 June 2011, Aerojet announced a strategic partnership with Teledyne Brown to develop and produce a domestic version of the NK-33 engine, with its thrust increased to 2.2 MN (500,000 lbf) at sea level. This booster is to compete against Shuttle-derived solid rocket boosters for the SLS launch vehicle.

Upper Stage

The SLS will make use of several upper stages in its various configurations:

  • Block 0 No upper stage
  • Block I A Delta Cryogenic Second Stage (DCSS), referred to as the Interim Cryogenic Propulsion Stage (iCPS). This 70-metric ton configuration currently will only fly two missions, Exploration Mission 1 (EM-1) and Exploration Mission 2 (EM-2). Although the DCSS is currently the favored upper stage, NASA documentation still lists the kick stage as “TBD”, or to be decided. Atlas V or Delta IV upper stages are noted options
  • Block IA A large Cryogenic Propulsion Stage, specifically developed for SLS and powered by liquid hydrogen fuel and liquid oxygen oxidiser. This 105-metric ton rocket will first launch as SLS-3. Currently there are four configurations of this vehicle under analysis by NASA, of which only two will be produced.
  • Block II A fully-fledged Earth Departure Stage to be powered by three J-2X engines. This 130-metric ton rocket evolution will not debut until the 2030s. As with the Block IA there are also four corresponding configurations of this vehicle under analysis by NASA.

Assembled Rocket

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.

Program Costs

Space Launch System (SLS) #3 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 $10B for the SLS rocket, $6B for the Orion Multi-Purpose Crew Vehicle and $2B 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 $41B for four 70 metric ton launches (1 unmanned in 2017, 3 manned starting in 2021), with the 130 metric ton version ready no earlier than 2030. HEFT estimate Block 0 unit cost at $1.6 billion.

Proposed Missions and Schedule

Some of the 14 currently proposed Design Reference Missions include:

  • 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 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 70mt 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 lunar Block 1 Orion MPCV with a liftoff mass around 62.2 t with SLS Payload Insertion of 50.4 t, which would be a six to ten day test mission with about one day around the Moon. 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, EM-1 overview as follows; Notional Mission Event Sequence:1) SLS lofts Orion to high-apogee orbit, while meeting core disposal constraints) 2)Kick-stage (TBD) performs burn to raise perigee to safe height. 3) Kick-stage (TBD) performs TLI burn, 4) 5 day transit time. 5) Lunar flyby. 6) 5 day transit time.
    • 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, Expected drivers include: SLS and ICPS performance, crew support for BEO mission duration, MPCV delta V, MPCV re-entry speed.
  • Strategic Timeframe DRMs
    • GEO vicinity 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 EML-1 and low lunar orbit 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.
    • 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 to spend 500 or more days exploring the surface of the red planet. The ambitious proposal would include the launch of seven SLS HLVs with nuclear propulsion stages, or NTRs (Nuclear Thermal Rocket). The seven payloads would then be assembled in LEO into three separate vehicles for the journey to Mars, the MLV Cargo Vehicle, MLV Habitat Vehicle, and MTV Crew Transfer Vehicle.
  • 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.

  1. "Space Launch System".Wikipedia. Accessed June 16, 2012.