Space Launch System

• 1. Origins And Congressional Mandate

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  The Space Launch System emerged from a specific legal requirement in 2010. Congress passed the NASA Authorization Act of 2010, Public Law 111, 267, which directed NASA to create a new system for launching payloads and crew into space. This mandate arrived as the Space Shuttle program drew to a close in 2009. The act set out clear goals such as lifting 70 to 100 tons into low earth orbit with an ability to evolve to 130 tons. A target date of the 31st of December 2016 appeared for the system to be fully operational. The legislation also included a directive to use existing components, hardware, and workforce from the Space Shuttle where practicable. This requirement shaped every subsequent design decision for the rocket. Senators representing states with significant aerospace industries opposed the cancellation of the shuttle-derived approach. Utah Senator Orrin Hatch ensured the new rocket used the Shuttle's solid boosters manufactured in his state. Alabama Senator Richard Shelby insisted that the Marshall Space Flight Center design and test the rocket. Florida Senator Bill Nelson brought billions of dollars to Kennedy Space Center to modernize its launch facilities.

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• 2. Engineering Architecture And Components

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  The core stage measures 58 meters long by 8.4 meters in diameter and is visually similar to the Space Shuttle external tank. It contains liquid hydrogen and liquid oxygen tanks for the ascent phase along with avionics and the Main Propulsion System. Four RS-25 engines provide thrust alongside two outboard solid rocket boosters. The first four flights will each use and expend four of the remaining sixteen RS-25D engines previously flown on Space Shuttle missions. Aerojet Rocketdyne refits these engines with modernized engine controllers and higher throttle limits. Later flights switch to an RS-25E variant optimized for expended use which lowers per-engine costs by over 30 percent. The five-segment solid rocket boosters provide approximately 25 percent more total impulse than the Shuttle Solid Rocket Boosters. They possess an additional center segment, new avionics, and lighter insulation but lack a parachute recovery system. The propellants include aluminum powder and ammonium perchlorate held together by polybutadiene ac519acrylonitrile binder. The Interim Cryogenic Propulsion Stage uses a single RL10B-2 engine while later versions utilize the RL10C-2 variant.

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• 3. Development History And Delays

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  Development of SLS began in 2011 as a replacement for the retiring Space Shuttle and canceled Ares I and Ares V launch vehicles. The first launch required by Congress to take place by 2016 occurred nearly six years later on the 16th of November 2022. Originally planned for late 2016, the uncrewed first flight slipped more than twenty-six times. The launch was originally scheduled for the 29th of August 2022 at 8:30 am EDT before being postponed to the 3rd of September 2022 due to a temperature sensor issue. A hydrogen leak in the tail service mast quick disconnect arm caused further delays leading to a launch in mid-November due to Hurricane Ian weather. Construction of the first core stage hardware began using a new friction stir welding system in mid-November 2014. Test 7 of the static firing program took place in December 2020 and fire test 8 occurred on the 16th of January 2021 but shut down earlier than expected about 67 seconds into the burn. The second fire test completed on the 18th of March 2021 with all four engines igniting and gimballing profiles. The complete core stage was delivered in July 2024 eight months later than predicted originally.

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• 4. Financial Overruns And Budgeting

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  NASA has spent $29 billion on SLS development from 2011 through 2024 in nominal dollars. This figure equals $35.4 billion in 2025 dollars using NASA New Start Inflation Indices. An internal 2011 NASA document estimated the cost of the program through 2025 to total at least $41 billion for four launches. By 2021, development of the core stage was expected to have cost $8.9 billion, twice the initially planned amount. A November 2021 report estimated that recurring production costs for SLS excluding development and integration costs are at least $2.5 billion per launch. In 2025, acting NASA administrator Sean Duffy stated that Artemis I, Artemis II, and Artemis III are all $4 billion a launch. The White House Office of Management and Budget letter to the Senate Appropriations Committee in October 2019 estimated total cost to the taxpayer was over $2 billion per launch. Ground systems modifications and construction required an additional $1.8 billion between February 2014 and September 2018.

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• 5. Political Compromises And Criticism

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  The program was characterized by a complex web of political compromises ensuring various regions and interests benefited. Representative Tom McClintock called on the Government Accountability Office to investigate possible violations of the Competition in Contracting Act. He argued that the requirement that Shuttle components be used were non-competitive and assured contracts to existing suppliers. The Obama administration's 2014 budget called for canceling SLS and turning over space transportation to commercial companies. Senators Shelby and Nelson quickly moved to fight efforts to cut the program and were ultimately victorious. During the First Trump administration, NASA administrator Jim Bridenstine suggested using the Falcon Heavy or Delta IV Heavy rocket to launch Orion instead of SLS. Afterward, the administrator was reportedly called into a meeting with Senator Shelby who told him he should resign for making the suggestion in a public meeting. A March 2020 report 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 percent in FY 2019 while an overrun of 30 percent would have required additional funding from Congress.

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• 6. Future Block Evolutions And Alternatives

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  Block 1B configuration with the purpose-built Exploration Upper Stage is to be introduced on the fourth flight. A further improved Block 2 configuration with new solid rocket boosters is planned for the ninth flight. The stock of SLS Block 1 to 1B boosters is limited by the number of casings left over from the Shuttle program which allows for eight flights. On the 2nd of March 2019, the Booster Obsolescence and Life Extension program was announced with the goal of developing new solid rocket boosters for SLS Block 2. These boosters will be built by Northrop Grumman Space Systems derived from composite-casing solid rocket boosters then in development for the canceled OmegA launch vehicle. In November 2019, Blue Origin submitted a proposal to replace the EUS with a cheaper alternative designed and fabricated by the company but it was rejected by NASA. SpaceX ultimately won the contract for Europa Clipper saving the agency an estimated $2 billion in direct launch costs over SLS. In 2025, the Trump administration released its fiscal year 2026 budget proposal calling for terminating the SLS and Orion spacecraft programs after Artemis III.

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