Artist's rendering of SLS Block 1/Orion
|Function||Super heavy-lift launch vehicle|
|Country of origin||United States|
|Project cost||US$7 billion (2014–18, 2014 estimate), to |
$35 billion (until 2025, 2011 est.)[better source needed]
|Height||111.25 m (365 ft 0 in), Block 2 Cargo|
|Diameter||8.4 m (27 ft 7 in), Core Stage|
|Payload to LEO|
|Payload to Moon|
|Launch sites||LC-39B, Kennedy Space Center|
|First flight||Artemis 1|
|Notable payloads||Orion MPCV, Europa Clipper, LOP-G|
|Boosters (Block 1, 1B)|
|No. boosters||2 five-segment Solid Rocket Boosters|
|Thrust||16,000 kN (3,600,000 lbf)|
|Total thrust||32,000 kN (7,200,000 lbf)|
|Specific impulse||269 seconds (2.64 km/s)|
|Burn time||126 seconds|
|First stage (Block 1, 1B, 2) – Core Stage|
|Length||64.6 m (211 ft 11 in)|
|Diameter||8.4 m (27 ft 7 in)|
|Empty mass||85,270 kg (187,990 lb)|
|Gross mass||979,452 kg (2,159,322 lb)|
|Thrust||7,440 kN (1,670,000 lbf)|
|Specific impulse||363 seconds (3.56 km/s) (sea level), 452 seconds (4.43 km/s) (vacuum)|
|Fuel||LH2 / LOX|
|Second stage (Block 1) – ICPS|
|Length||13.7 m (44 ft 11 in)|
|Diameter||5 m (16 ft 5 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 (4.53 km/s)|
|Burn time||1125 seconds|
|Fuel||LH2 / LOX|
|Second stage (Block 1B, Block 2) – Exploration Upper Stage|
|Diameter||8.4 m (27 ft 7 in)|
|Thrust||440 kN (99,000 lbf)|
|Fuel||LH2 / LOX|
The Space Launch System (SLS) is a US super heavy-lift expendable launch vehicle, which is under development as of August 2019. It is the primary launch vehicle of NASA's deep space exploration plans, including the planned crewed lunar flights of the Artemis program and a possible follow-on human mission to Mars.
The initial SLS Block 1 is required by the US Congress to lift a payload of 95 metric tons (209,000 lb) to low Earth orbit (LEO), and will launch Artemis 1 and Artemis 2. The later Block 1B is intended to debut the Exploration Upper Stage and launch the Artemis 3 and the notional Artemis 4-8. Block 2 is planned to replace the initial Shuttle-derived boosters with advanced boosters and would have a LEO capability of more than 150 metric tons (330,000 lb), again as required by Congress. Block 2 is intended to enable crewed launches to Mars. The SLS will launch the Orion spacecraft and use the ground operations and launch facilities at NASA's Kennedy Space Center in Florida.
The SLS is a Shuttle-Derived Launch Vehicle and will have the ability to tolerate a minimum of 13 tanking cycles due to launch scrubs and other launch delays before launch. 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.
The Space Launch System's Core Stage will be 8.4 meters (28 ft) in diameter and mount a Main Propulsion System (MPS) incorporating four RS-25 engines. The core stage will be structurally similar to the Space Shuttle external tank, and initial flights will use modified RS-25D engines left over from the Space Shuttle program. Later flights will switch to a cheaper version of the engine not intended for reuse.
The core stage will be fabricated at the Michoud Assembly Facility and is common across all currently planned evolutions of the SLS to avoid the need for substantial redesigns to meet various payload mandates.
Blocks 1 and 1B of the SLS will use two five-segment Solid Rocket Boosters (SRBs) based on the four-segment Space Shuttle Solid Rocket Boosters. Modifications to the five-segment boosters included the addition of a center booster segment, new avionics, and lighter insulation. The five-segment SRBs provide approximately 25% more total impulse than the Shuttle SRB and will not be recovered after use.
Several companies proposed boosters for this competition:
In 2013, the manager of NASA's SLS advanced development office indicated that all three approaches were viable.
However, the 2015 competition was planned in support of Block 1A. A later study found that the advanced booster would have resulted in unsuitably high acceleration, and NASA canceled Block 1A and the planned competition in 2014. In February 2015, it was reported that SLS is expected to fly with the five-segment SRB until at least the late 2020s, and modifications to Launch Pad 39B, its flame trench, and SLS's Mobile Launcher Platform were being evaluated.
The Interim Cryogenic Propulsion Stage (ICPS) is planned to fly on Artemis 1. It is a modified Delta IV 5-meter (16 ft) Delta Cryogenic Second Stage (DCSS) powered by a single RL10B-2. Block 1 will be capable of lifting 95 t to LEO in this configuration if the ICPS is considered part of the payload. Artemis 1 will be launched into an initial 1,800 by −93 km (1,118 by −58 miles) suborbital trajectory to ensure safe disposal of the core stage. ICPS will then perform an orbital insertion burn at apogee and a subsequent translunar injection burn to send Orion towards the moon.
The Exploration Upper Stage (EUS) is planned to fly on Artemis 3. Similar to the S-IVB, the EUS would have completed the SLS ascent phase and then re-ignited to send its payload to destinations beyond low-Earth orbit. It was expected to be used by Block 1B and Block 2, share the core stage diameter of 8.4 meters, and be powered by four RL10 engines.
|SLS variant||Payload mass to ...|
|low Earth orbit (LEO)||trans-lunar injection (TLI)||heliocentric orbit (HCO)|
|Block 1||95 t (209,439 lb)||26 t (57,000 lb)|
|Block 1B||105 t (231,000 lb)||37 t (88,000 lb)|
|Block 2||130 t (290,000 lb)||45 t (99,000 lb)|
SLS is to replace the retired Space Shuttle as NASA's flagship vehicle. Following the cancellation of the Constellation program, the NASA Authorization Act of 2010 envisioned a single launch vehicle usable for both crew and cargo. SLS is to have the world's highest ever total thrust at launch, but not the world's highest ever payload mass. In 2013, SLS was projected to possibly be the most capable super-heavy lift vehicle ever built.
During the joint Senate-NASA presentation in September 2011, it was stated that the SLS program had a projected development cost of $18 billion through 2017, with $10 billion for the SLS rocket, $6 billion for the Orion Multi-Purpose Crew Vehicle and $2 billion for upgrades to the launch pad and other facilities at Kennedy Space Center. These costs and schedule were considered optimistic in an independent 2011 cost assessment report by Booz Allen Hamilton for NASA.
An unofficial 2011 NASA document estimated the cost of the program through 2025 to total at least $41bn for four 95 t launches (1 uncrewed, 3 crewed), with the 130 t version ready no earlier than 2030.
The Human Exploration Framework Team (HEFT) estimated unit costs for Block 0 at $1.6bn and Block 1 at $1.86bn in 2010. However, since these estimates were made the Block 0 SLS vehicle was dropped in late 2011, and the design was not completed. The Space Review estimated the cost per launch at $5 billion, depending on the rate of launches. NASA announced in 2013 that the European Space Agency will build the Orion Service Module.
In September 2012, an SLS deputy project manager stated that $500 million per launch is a reasonable target cost for SLS. By comparison, a Saturn V launch cost roughly $1.23 billion in 2016 dollars.
In August 2014, as the SLS program passed its Key Decision Point C review and entered full development, costs from February 2014 until its planned launch in September 2018 were estimated at $7.021 billion. Ground systems modifications and construction would require an additional $1.8 billion over the same time period.
In October 2018, NASA's inspector general reported that the Boeing core stage contract had made up 40 percent of the $11.9 billion spent on SLS as of August 2018. By 2021, core stages were expected to have cost a total of US$8.9 billion, which is twice the initial planned amount.
In December 2018, NASA estimated that yearly budgets for SLS will range from US$2.1 to US$2.3B between 2019 to 2023.
In March 2019, the Trump Administration released its Fiscal Year 2020 Budget Request for NASA. This budget did not include any money for the Block 1B and Block 2 variants of SLS. It is uncertain whether these future variants of SLS will be developed. Several launches previously planned for the SLS Block 1B are now expected to fly on commercial launcher vehicles such as Falcon Heavy, New Glenn, Omega, and Vulcan. However, the request for a budget increase of 1.6 billion dollars towards SLS, Orion, and crewed landers along with the launch manifest seem to indicate support of the development of Block 1B, debuting Artemis 3. The Block 1B will be used mainly for co manifested crew transfers and logistic rather than constructing the Gateway. An uncrewed Block 1B is planned to launch the Lunar Surface Asset in 2028, the first lunar outpost of the Artemis program. Block 2 development will most likely start in the late 2020s, after NASA is regularly visiting the lunar surface and shifts focus towards Mars.
For fiscal years 2011 through 2018, the SLS program had expended funding totaling $13,999 million in nominal dollars. This is equivalent to $15,109 million adjusting to 2018 dollars using the NASA New Start Inflation Indices.
|Fiscal Year||Funding ($millions)||Status|
(Formal SLS Program reporting excludes the Fiscal 2011 budget.)
Excluded from the prior SLS costs are:
Included in the prior SLS costs are:
There are no current NASA estimates for the average costs per flight of SLS, nor for the SLS program recurring yearly costs once operational. In 2016, the projected annual cost for Orion, SLS, and ground systems was $2 billion or less. NASA associate administrator William H. Gerstenmaier has said that per flight cost estimates will not be provided by NASA.
From 2009 to 2011, three full-duration static fire tests of five-segment SRBs were conducted under the Constellation Program, including tests at low and high core temperatures to validate performance at extreme temperatures. The 5-segement SRB would be carried over to SLS.
During the early development of the SLS a number of configurations were considered, including a Block 0 variant with three main engines, a Block 1A variant with upgraded boosters instead of the improved second stage, and a Block 2 with five main engines and the Earth Departure Stage, with up to three J-2X engines. In February 2015, it was determined that these concepts would exceed the congressionally mandated Block 1 and Block 1B baseline payloads.
On 14 September 2011, NASA announced the new launch system, which is intended to take the agency's astronauts farther into space than ever before and provide the cornerstone for future US human space exploration efforts in combination with the Orion spacecraft
On 31 July 2013, the SLS passed the Preliminary Design Review (PDR). The review included not only the rocket and boosters but also ground support and logistical arrangements. On August 7, 2014 the SLS Block 1 passed a milestone known as Key Decision Point C and entered full-scale development, with an estimated launch date of November 2018.
In 2013, NASA and Boeing analyzed the performance of several EUS engine options. The analysis was based on a second stage usable propellant load of 105 metric tons, and compared stages with four RL10 engines, two RL60 engines, or one J-2X engine.
In 2014, NASA also considered using the European Vinci instead of the RL10. The Vinci offers the same specific impulse but with 64% greater thrust, which would allow for the same performance at lower cost.
Northrop Grumman Innovation Systems has completed full-duration static fire tests of the five-segment SRBs. Qualification Motor 1 (QM-1) was tested on March 10, 2015. Qualification Motor 2 (QM-2) was successfully tested on June 28, 2016.
As of 2019[update], three SLS versions are planned: Block 1, Block 1B, and Block 2. Each will use the same core stage with four main engines, but Block 1B will feature the Exploration Upper Stage (EUS), and Block 2 will combine the EUS with upgraded boosters.
In mid-November 2014, construction of the first core stage hardware began using a new welding system in the South Vertical Assembly Building at NASA's Michoud Assembly Facility. Between 2015 and 2017 NASA test fired RS-25 engines in preparation for use on SLS.
Confidence article builds for the core stage began on January 5, 2016 and were expected to be completed in late January of that year. Once completed the test articles will be sent to ensure structural integrity at Marshall Spaceflight Center. A structural test article of the ICPS was delivered in 2015, with the core stage for Artemis 1 is in assembly as of August 2019.
The first static firing ground test is to take place by the second quarter of 2020. Given this the first launch can not occur before 2021.
The SLS has been criticized on the basis of: program cost; lack of commercial involvement; and the non-competitive nature of a vehicle legislated to use Space Shuttle components.
In 2009, the Augustine commission proposed a commercial 75-metric-ton (165,000 lb) launcher with lower operating costs, and noted that a 40–60 t (88,000–132,000 lb) launcher was the minimum required to support lunar exploration.
In 2011–2012, 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. U.S. Representative Dana Rohrabacher and others proposed that an orbital propellant depot should be developed and the Commercial Crew Development program accelerated instead. A NASA study that was not publicly released and another from the Georgia Institute of Technology showed this option to be possibly cheaper. In 2012, the United Launch Alliance also suggested using existing rockets with on-orbit assembly and propellant depots as needed. The lack of competition in the SLS design was highlighted. In the summer of 2019, a former ULA employee claimed that Boeing, NASA's prime contractor for SLS, viewed orbital refueling technology as a threat to SLS and blocked further investment in it.
In 2010, SpaceX's CEO Elon Musk claimed that his company could build a launch vehicle in the 140–150 t payload range for $2.5 billion, or $300 million (in 2010 dollars) per launch, not including a potential upper-stage upgrade. In the early 2010s, SpaceX went on to start development of BFR, a planned fully reusable super-heavy launch system. Reusability is claimed to allow the lowest cost super-heavy launcher ever made. If the price per launch and payload capabilities for the BFR are anywhere near Musk's claimed capabilities, the rocket will be substantially cheaper than the SLS.
In 2011, Rep. Tom McClintock and other groups called on the Government Accountability Office (GAO) to investigate possible violations of the Competition in Contracting Act (CICA), arguing that Congressional mandates forcing NASA to use Space Shuttle components for SLS are de facto non-competitive, single source requirements assuring contracts to existing shuttle suppliers. 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".
In 2013, Chris Kraft, the NASA mission control leader from the Apollo era, expressed his criticism of the system as well. Lori Garver, former NASA Deputy Administrator, has called for cancelling the program. Phil Plait has voiced his criticism of SLS in light of ongoing budget tradeoffs between Commercial Crew Development and SLS budget, also referring to earlier critique by Garver.
In 2019, the Government Accountability Office found that NASA had awarded Boeing over $200 million for service with ratings of good to excellent despite cost overruns and delays. The first SLS launch is now expected in 2020 or 2021.
|Flight No.||Date / time (UTC)||Configuration||Payload||Payload mass||Outcome|
|Maiden flight of the SLS, carrying the Artemis 1 mission hardware and cubesats for ten missions in the CubeSat Launch Initiative (CLSI), and three missions in the Cube Quest Challenge.[clarification needed] The payloads will be sent on a trans-lunar injection trajectory.|
|Carrying the Artemis 2 mission hardware, along with numerous cubesats to be selected through the CSLI.|
|Carrying the Europa Clipper spacecraft to Jupiter via a direct hohmann transfer orbit.|
|Maiden flight of the Block 1B with the EUS, carrying the Artemis 3 mission hardware.|
RS-25D engine testing at Stennis Space Center
BioSentinel is one of 13 cubesats flying aboard the Artemis 1 mission, which is currently targeted for mid-2020. [...] The other 12 cubesats flying aboard Artemis 1 are a diverse lot. For example, the Lunar Flashlight and Lunar IceCube missions will hunt for signs of water ice on the moon, and Near-Earth Asteroid Scout will use a solar sail to rendezvous with a space rock.Cite uses deprecated parameter
NASA's Space Technology Mission Directorate (STMD) has awarded rides for three small spacecraft on the agency's newest rocket, and $20,000 each in prize money, to the winning teams of citizen solvers competing in the semi-final round of the agency’s Cube Quest Challenge.Cite uses deprecated parameter
...after the Space Launch System performs the Trans-Lunar Injection burn that sends the spacecraft out of Earth orbit and toward the Moon.Cite uses deprecated parameter
The Artemis 1 mission profile. Cr: NASA [...] The Artemis 1 mission will send the Orion spacecraft into a distant retrograde lunar orbit and back...Cite uses deprecated parameter
NASA is seeking proposals from U.S. small satellite developers to fly their CubeSat missions as secondary payloads aboard the SLS on the Artemis 2 mission under the agency's CubeSat Launch Initiative (CSLI).Cite uses deprecated parameter
NASA on Aug. 5 released a solicitation for cubesats to ride along with the first crewed flight of the Space Launch System rocket and Orion capsule, with the caveat that selected projects fill strategic knowledge gaps for future lunar and Mars exploration.Cite uses deprecated parameter
But now NASA is going to fly all three missions — EM-1, EM-2, and Europa Clipper — on Block 1. [...] According to the memo, NASA will aim to have the second platform ready for a Block 1B launch in the beginning of 2024.Cite uses deprecated parameter
Data was collected during several hundred supersonic test runs in the Unitary Plan Wind Tunnel at Langley of a scale model of the Block 1 Cargo vehicle that is the currently mandated booster for the upcoming Europa Clipper mission.Cite uses deprecated parameter
Although U.S. federal appropriations bills enacted into law for the last three fiscal years mandate a Europa Clipper launch on SLS and "no later than 2022," the presentations to the HEO committee show that launch on a Block 1 Cargo vehicle in 2023.Cite uses deprecated parameter
In the wake of ML-2 funding and the change in direction, NASA began looking at "Jupiter Direct" trajectories with Block 1 again. NASA's early analyses of launch windows for Europa Clipper in 2022, 2023, 2024, or 2025 indicate that direct trajectories are feasible for SLS Block 1.Cite uses deprecated parameter
He added that both the original Block 1 version of SLS, as well as the Block 1B with the more powerful Exploration Upper Stage, are the only vehicles with C3 values high enough to allow for a direct trajectory for the six-ton Europa Clipper spacecraft. The less-powerful Block 1 is still sufficient, he said, mitigating concerns about any delays in the development of the Block 1B.
The mission will be the first cargo flight of the SLS and will likely – though not confirmed – be the first SLS Block 1B launch.Cite uses deprecated parameter
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