Space Launch System

Estimates of the per launch costs for the SLS have varied widely, partly due to uncertainty over how much the program will expend during development and testing before the operational launches begin, and partly due to various agencies using differing cost measures; but also based on differing purposes for which the cost estimates were developed. For example, a marginal cost per one additional launch ignores the development and annual recurring fixed costs, whereas a total cost per launch includes recurring costs but excludes development.

There are no official NASA estimates for how much the SLS will cost per launch, nor for the SLS program annual recurring costs once operational. Cost per launch is not a straightforward figure to estimate as it depends heavily on how many launches occur per year. For example, similarly, the Space Shuttle was estimated, in 2012 dollars, to cost $576 million per launch had it been able to achieve 7 launches per year, while the marginal cost of adding a single additional launch in a given year was estimated to be less than half of that, at just $252 million of marginal cost. However, at the rate that it flew, the final cost was $1.64 billion per Space Shuttle launch, including development.^{: III−490}

NASA associate administrator William H. Gerstenmaier said in 2017 that there would be no official per flight cost estimates of any variety provided by NASA for the SLS. Other bodies, such as the Government Accountability Office (GAO), the NASA Office of Inspector General, the Senate Appropriations Committee, and the White House Office of Management and Budget have put out cost per launch figures, however. Several internal NASA programs and project concept study reports have released proposed budgets that include future SLS launches. For example, a concept study report for a space telescope stated it was advised by NASA HQ in 2019 to budget $500 million for an SLS launch in 2035. Another study in 2019 also proposing a space telescope assumed a budget for their launch of $650 million in current-day dollars, or $925 million for when the launch would occur, also in the "mid-2030s".

Europa Clipper launch cost

Europa Clipper is a NASA scientific mission that was initially required by Congress to launch on SLS. Oversight bodies both internal and external to NASA disagreed with this requirement. First, NASA's Inspector General office published a report in May 2019 that stated Europa Clipper would need to give up $876 million for the "marginal cost" of its SLS launch. An addendum to the letter published in August 2019 increased the estimate and stated that switching to a commercial rocket would save over $1 billion.

A JCL (Joint Cost and Schedule Confidence Level) analysis cited in that letter put the cost savings at $700 million, with the SLS at $1.05 billion per launch and the commercial alternative at $350 million. Finally, a letter from the White House Office of Management and Budget (OMB) to the Senate Appropriations Committee in October 2019 revealed that SLS's total cost to the taxpayer was estimated at "over $2 billion" per launch after development is complete; said development has cost $23 billion in 2021 dollars. The letter suggested Congress remove this requirement, agreeing with the NASA Inspector General, and added that using a commercial launch vehicle for Europa Clipper instead of the SLS would save $1.5 billion overall. NASA did not deny this $2 billion cost of launch and an agency spokesperson stated it "is working to bring down the cost of a single SLS launch in a given year as the agency continues negotiations with Boeing on the long-term production contract and efforts to finalize contracts and costs for other elements of the rocket".

Ultimately, Europa Clipper was rebooked in 2021 to launch on a Falcon Heavy for a contract price of $178 million — saving $2 billion in launch costs compared to SLS. The move was done not only for cost reasons but also due to unacceptably high vibration loads on SLS, and concerns over the availability of spare SLS vehicles from the Artemis program.

Launch Cost, Generally

The 2019 OMB figure above is dependent on the rate of construction, so building more SLS rockets faster could decrease the per-unit cost. For example, Exploration Ground Systems – whose only role is to support, assemble, integrate, and launch SLS – has separately budgeted fixed costs of $600 million per year on facilities, spread across however many rockets launch that year. Then, in December 2019, NASA Administrator Jim Bridenstine shared informally that he disagrees with the $2 billion figure since the marginal cost of an SLS launch should decrease after the first few, and is expected to end up around $800 million to $900 million, although contract negotiations were only just beginning for those later cores.

In November 2021 a new NASA Office of Inspector General audit was released, which estimated that, at least for the first four launches of SLS, the per-launch production and operating costs would be $2.2 billion for SLS, plus $568 million for Exploration Ground Systems. Additionally, since the first four missions are under the Artemis program, the payload would cost $1 billion for Orion and $300 million for the ESA service module.^: 23

Construction

 

 

 

As of 2020^[update], three SLS versions are planned: Block 1, Block 1B, and Block 2. Each will use the same Core stage with its four main engines, but Block 1B will feature the Exploration Upper Stage (EUS), and Block 2 will combine the EUS with upgraded boosters.

The ICPS for Artemis 1 was delivered by ULA to NASA about July 2017 and was housed at Kennedy Space Center as of November 2018.

Construction of core stage

In mid-November 2014, construction of the first core stage hardware began using a new friction stir 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.

The core stage for the first SLS, built at Michoud Assembly Facility by Boeing, had all four engines attached in November 2019, and it was declared finished by NASA in December 2019.

The first core stage left Michoud Assembly Facility for comprehensive testing at Stennis Space Center in January 2020. The static firing test program at Stennis Space Center, known as the Green Run, operated all the core stage systems simultaneously for the first time. Test 7 (of 8), the wet dress rehearsal, was carried out in December 2020 and the fire (test 8) took place on 16 January 2021, but shut down earlier than expected, about 67 seconds in total rather than the desired eight minutes. The reason for the early shutdown was later reported to be because of conservative test commit criteria on the thrust vector control system, specific only for ground testing and not for flight. If this scenario occurred during a flight, the rocket would have continued to fly normally. There was no sign of damage to the core stage or the engines, contrary to initial concerns. The second fire test was completed on 18 March 2021, with all four engines igniting, throttling down as expected to simulate in-flight conditions, and gimballing profiles. The core stage was shipped to Kennedy Space Center to be mated with the rest of the rocket for Artemis 1. It left Stennis on April 24 and arrived at Kennedy on April 27. It was refurbished there in preparation for stacking. On 12 June 2021, NASA announced the assembly of the first SLS rocket was completed at the Kennedy Space Center. The assembled SLS was used for the uncrewed Artemis 1 mission in 2022.

The first SLS, for Artemis 1, launched an Orion spacecraft into a lunar orbit on a test flight in fall 2022, and NASA and Boeing are constructing the next three rockets for Artemis 2, Artemis 3, and Artemis 4. Boeing stated in July 2021 that while the COVID-19 pandemic had affected their suppliers and schedules, such as delaying parts needed for hydraulics, they would still be able to provide the Artemis 2 SLS core stage per NASA's schedule, with months to spare. The spray-on foam insulation process for Artemis 2 was automated for most sections of the core stage, saving 12 days in the schedule. The Artemis 2 forward skirt, the foremost component of the core stage, was affixed on the liquid oxygen tank in late May 2021. By 25 September 2023 the core stage was functionally complete, as all sections were assembled and the four RS-25 engines had been installed. As of May 2023^[update], the complete core stage was set to ship to NASA in late fall 2023, eight months later than was predicted originally. As of February 2024, this has still not happened. For Artemis 3, assembly of elements of the thrust structure began at Michoud Assembly Facility in early 2021. The liquid hydrogen tank for Artemis 3 was originally planned to be the Artemis 1 tank, but it was set aside as the welds were found to be faulty.^: 2 Repair techniques were developed, and the tank re-entered production and will be proof tested for strength, for use on Artemis 3.^: 2

Construction of EUS for Block 1B

As of July 2021, Boeing is also preparing to begin construction of the Exploration Upper Stage (EUS), which is planned to debut on Artemis 4.

Launches

Originally planned for late 2016, the uncrewed first flight of SLS slipped more than twenty-six times and almost six years. As of earlier that month, the first launch was originally scheduled for 8:30 am EDT, 29 August 2022. It was postponed to 2:17 pm EDT (18:17 UTC), 3 September 2022, after the launch director called a scrub due to a temperature sensor falsely indicating that an RS-25 engine's hydrogen bleed intake was too warm. The 3 September attempt was then scrubbed due to a hydrogen leak in the tail service mast quick disconnect arm, which was fixed; the next launch option was at first a period in late October and then a launch in mid-November, due to unfavorable weather during Hurricane Ian. It launched on November 16.

NASA originally limited the amount of time the solid rocket boosters can remain stacked to "about a year" from the time two segments are joined. The first and second segments of the Artemis 1 boosters were joined on 7 January 2021. NASA could choose to extend the time limit based on an engineering review. On 29 September 2021, Northrop Grumman indicated that the limit could be extended to eighteen months for Artemis 1, based on an analysis of the data collected when the boosters were being stacked; an analysis weeks before the actual launch date later extended that to December 2022 for the boosters of Artemis 1, almost two years after stacking.

In late 2015, the SLS program was stated to have a 70% confidence level for the first Orion flight that carries crew, the second SLS flight overall, to happen by 2023; as of November 2021^[update], NASA delayed Artemis 2 from 2023 to May 2024. In March 2023, NASA announced they had delayed Artemis 2 to November 2024 and in January 2024 the mission was further delayed to September 2025.

Usage beyond Artemis

Although the SLS is only confirmed for use on the first few Artemis missions, several NASA mission concept studies for robotic missions considered launching on the SLS. These include: Neptune Odyssey, Europa Lander, Enceladus Orbilander, Persephone, HabEx, Origins Space Telescope, LUVOIR, Lynx, and Interstellar probe. These concept studies were prepared for possible recommendation by the National Academy's Decadal surveys. The Astronomy and Astrophysics Decadal Survey in 2021 recommended a smaller, merged version of HabEx and LUVOIR preceded by a technology maturation program to reduce cost and schedule risk, although the eventual mission may or may not use SLS. In 2022 the Planetary Science Decadal Survey recommended Enceladus Orbilander as the third highest priority for flagship planetary missions in the 2020s. The Heliophysics Decadal Survey, due to be completed in 2024, is considering the Interstellar Probe mission concept.

NASA is planning to turn over the SLS to contractors such as Boeing and Northtrop Grumman to find more buyers and bring down costs, hoping to reduce the rocket's price tag to $1 billion. Finding a market for a large and costly rocket is difficult however, Reuters reported. The DoD, seen as a potential customer, stated in 2023 that it is not interested in a partnership with NASA or the SLS as other rockets already offer them the capability that they need at an affordable price.

The SLS has been criticized based on program cost, lack of commercial involvement, and non-competitiveness of legislation requiring the use of Space Shuttle components.

Funding

In 2011, Rep. Tom McClintock and other groups^[who?] called on the Government Accountability Office to investigate possible violations of the Competition in Contracting Act, arguing that the requirement that Space Shuttle components be used on SLS were non-competitive and assured contracts to existing Space Shuttle suppliers. In 2014, Lori Garver, a former NASA Deputy Administrator, called for cancelling the launch vehicle alongside the Mars 2020 rover. In 2023, Cristina Chaplain, former assistant director of the GAO, has expressed doubts about the reduction of the rocket's cost to a competitive threshold, "just given the history and how challenging it is to build".

 

Management

In 2019, the Government Accountability Office noted that NASA had assessed the performance of contractor Boeing positively, though the project had experienced cost growth and delay. A March 2020 report by Office of Inspector General found NASA moved out $889 million of costs relating to SLS boosters, but did not update the SLS budget to match. This kept the budget overrun to 15% in FY 2019;^: 22 an overrun of 30% would have required NASA to request additional funding from Congress^: 21–23 The Inspector General report found that were it not for this "masking" of cost, the overrun would have been 33% by FY 2019.^: iv, 23 The GAO stated "NASA's current approach for reporting cost growth misrepresents the cost performance of the program".^: 19–20

Proposed alternatives

In 2009, the Augustine commission proposed a commercial 165,000 lb (75 t) launcher for lunar exploration. In 2011–2012, the Space Access Society, Space Frontier Foundation, and The Planetary Society called for the cancellation of the project, arguing that the SLS would consume the funds for other projects from the NASA budget. U.S. Representative Dana Rohrabacher and others^[who?] proposed the development of an orbital propellant depot and the acceleration of the Commercial Crew Development program as an alternative to the SLS program.

An unpublished NASA study and another from the Georgia Institute of Technology found these approaches could have lower costs. In 2012, United Launch Alliance also suggested using existing rockets with on-orbit assembly and propellant depots as needed. In 2019, a former ULA employee alleged that Boeing viewed orbital refueling technology as a threat to the SLS and blocked investment in the technology. In 2010, SpaceX's CEO Elon Musk claimed that his company could build a launch vehicle in the 310,000–330,000 lb (140–150 t) payload range for $2.5 billion, or $300 million (in 2010 dollars) per launch, not including a potential upper-stage upgrade.

Former NASA Administrator Charlie Bolden, expressed that the SLS could be replaced in the future in an interview with Politico in September 2020. Bolden said that the "SLS will go away ... because at some point commercial entities are going to catch up." Bolden further stated, "They are really going to build a heavy-lift launch vehicle sort of like SLS that they will be able to fly for a much cheaper price than NASA can do SLS. That's just the way it works."

• Austere Human Missions to Mars
• Comparison of orbital launch systems
• DIRECT, proposals prior to SLS
• Shuttle-Derived Heavy Lift Launch Vehicle, a 2009 concept launch vehicle
• Ares V, a 2000s cargo vehicle design for the Constellation Program
• National Launch System, 1990s
• Saturn rocket family, 1960s
• Starship HLS, lunar variant of super heavy-lift vehicle Starship
• Studied Space Shuttle Variations and Derivatives