“Space Launch System”的意思、由来-开放百科全书

The Space Launch System (SLS) is an American Space Shuttle-derived super heavy-lift expendable launch vehicle. It is a primary part of NASA's deep space exploration plans,^[2]^[3] including the planned Orion Program crewed missions to the Moon and Mars.^[4]^[5]^[15] SLS 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 Constellation program's Ares I and Ares V vehicle designs into a single launch vehicle usable for both crew and cargo, similar to the Ares IV concept. The SLS is to be the most powerful rocket in existence^[6] with a total thrust greater than that of the Saturn V,^[7] although Saturn V could carry a greater payload mass.^[8]^[19]^[9]^[10]

The SLS launch vehicle is to be upgraded over time with more powerful versions. Its initial Block 1 version is to lift a payload of 95 metric tons to low Earth orbit (LEO), which will be increased with the debut of Block 1B and the Exploration Upper Stage.^[11] Block 2 will replace the initial Shuttle-derived boosters with advanced boosters and is planned to have a LEO capability of more than 130 metric tons to meet the congressional requirement.^[23] These upgrades will allow the SLS to lift astronauts and hardware to destinations beyond LEO: on a circumlunar trajectory as part of Exploration Mission 1 & 2 with Block 1; to deliver elements of the Lunar Orbital Platform-Gateway (LOP-G) with Block 1B; and to Mars with Block 2.^[15] The SLS will launch the Orion Crew and Service Module and may support trips to the International Space Station if necessary. 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, in combination with the Orion spacecraft,^[12] would take the agency's astronauts farther into space than ever before and provide the cornerstone for future US human space exploration efforts.^[13]^[14]^[15]

During the early development of the SLS a number of configurations were considered, including a Block 0 variant with three main engines,^[29] a Block 1A variant that would have upgraded the vehicle's boosters instead of its second stage,^[16] and a Block 2 with five main engines and a different second stage, the Earth Departure Stage, with up to three J-2X engines.^[31] In February 2015, it was reported that NASA evaluations showed "over performance" versus the baseline payload for Block 1 and Block 1B configurations.^[32]

Three versions of the SLS launch vehicle 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 a more powerful second stage called the Exploration Upper Stage (EUS), and Block 2 will combine the EUS with upgraded boosters. Block 1 has a baseline LEO payload capacity of {{convert|95|MT|ST}} and Block 1B has a baseline of {{convert|105|MT|ST}}.^[33] The proposed Block 2 will have lift capacity of {{convert|130|MT|ST}}, which is similar to that of the Saturn V.^[17]^[18] Some sources state this would make the SLS the most capable heavy lift vehicle built;^[36]^[19] although the Saturn V lifted approximately {{convert|140|MT|ST}} to LEO in the Apollo 17 mission.^[20]^[21]

On July 31, 2013, the SLS passed the Preliminary Design Review (PDR). The review encompassed all aspects of the SLS's design, not only the rocket and boosters but also ground support and logistical arrangements.^[22] 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.^[41]^[23] In April 2017, NASA announced that the schedule for the maiden flight would slip to 2019.^[24] In November 2017, the EM-1 maiden flight slipped further to June 2020.^[9]

Vehicle description

Core Stage

The Space Launch System's Core Stage will be {{convert|8.4|m|sp=us}} in diameter and use four RS-25 engines.^[25]^[16] Initial flights will use modified RS-25D engines left over from the Space Shuttle program;^[26] later flights are expected to switch to a cheaper version of the engine not intended for reuse.^[48] The stage's structure will consist 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.^[27]^[28] It will be fabricated at the Michoud Assembly Facility.^[29]

The core stage will be common across all currently planned evolutions of the SLS. Initial planning included studies of a smaller Block 0 configuration with three RS-25 engines,^[30]^[31] which was eliminated to avoid the need to substantially redesign the core stage for more powerful variants.^[16] Likewise, while early Block 2 plans included five RS-25 engines on the core,^[32] it was later baselined with four engines.^[32]

Boosters

Shuttle-derived boosters

Blocks 1 and 1B of the SLS will use two five-segment Solid Rocket Boosters (SRBs), which are based on the four-segment Space Shuttle Solid Rocket Boosters. Modifications for the SLS included the addition of a center booster segment, new avionics, and new insulation which eliminates the Shuttle SRB's asbestos and is {{convert|1900|lb|kg|order=flip|abbr=on}} lighter. The five-segment SRBs provide approximately 25% more total impulse than the Shuttle SRB and will not be recovered after use.^[33]^[34]

Orbital ATK (formerly Alliant Techsystems, part of Northrop Grumman since mid-2018) has completed full-duration static fire tests of five-segment SRBs. These include successful firings of three developmental motors (DM-1 to DM-3) from 2009 to 2011. The DM-2 motor was cooled to a core temperature of {{convert|40|F|abbr=on}}, and DM-3 was heated to above {{convert|90|F|abbr=on}} to validate performance at extreme temperatures.^[35]^[36]^[37] Qualification Motor 1 (QM-1) was tested on March 10, 2015.^[38] Qualification Motor 2 was successfully tested on June 28, 2016. It was the final ground test before Exploration Mission 1 (EM-1).{{citation needed|date=June 2016}}

Advanced boosters

For Block 2, NASA plans to switch from Shuttle-derived five-segment SRBs to advanced boosters.^[39] This will occur after development of the Exploration Upper Stage for Block 1B. Early plans would have developed advanced boosters before an updated second stage; this configuration was called Block 1A. By 2012 NASA planned to select these new boosters through an Advanced Booster Competition which was to be held in 2015.^[25]^[40] Several companies proposed boosters for this competition:

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."^[50]

Later analysis showed the Block 1A configuration would result in high acceleration which would be unsuitable for Orion and could require a costly redesign of the Block 1 core.^[51] In 2014, NASA confirmed the development of Block 1B instead of Block 1A and called off the 2015 booster competition.^[44]^[52] 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 evaluated based on SLS launching with solid-fuel boosters.^[44]

Upper Stage

Interim Cryogenic Propulsion Stage

Block 1, scheduled to fly Exploration Mission 1 (EM-1) in 2020,^[9] will use the Interim Cryogenic Propulsion Stage (ICPS). This stage will be a modified Delta IV 5–meter Delta Cryogenic Second Stage (DCSS),^[53] and will be powered by a single RL10B-2. Block 1 will be capable of lifting 95 t in this configuration, however the ICPS will be considered part of the payload and be placed into an initial 1,800 km by -93 km suborbital trajectory to ensure safe disposal of the core stage. ICPS will perform an orbital insertion burn at apogee, and then a translunar injection burn to send the uncrewed Orion on a circumlunar excursion.^[54] In May 2018, NASA updated the payload capability of the SLS Block 1 from 70 to 95 metric tons to low Earth orbit.^[4]

Exploration Upper Stage

The Exploration Upper Stage (EUS) was scheduled to fly on Exploration Mission 2 (EM-2). It was expected to be used by Block 1B and Block 2 and, like the core stage, have a diameter of 8.4 meters. The EUS is to be powered by four RL10 engines,^[55] complete the SLS ascent phase and then re-ignite to send its payload to destinations beyond low-Earth orbit, similar to the role performed by the Saturn V's 3rd stage, the J-2 powered S-IVB.^[56] Because of delays in building the mobile launch platform needed to hold the more powerful EUS, the EM-2 flight might launch earlier than planned but it will not use the EUS,^[57] it will not carry a module for the Lunar Gateway and it will not orbit the Moon.

Other upper stages

Payload carrying capacity

Fabrication and testing

In mid-November 2014, construction of the first SLS rocket began using the new welding system in the South Vertical Assembly Building at NASA's Michoud Assembly Facility, where the Core Stage will be assembled.^[77]

The SLS 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 without destacking.^[78]

In January 2015, NASA began test firing RS-25 engines in preparation for use on SLS. Tests continued throughout Spring of 2015. Further testing was conducted in 2016 and 2017.^[79]

Multiple facilities throughout the country have started full scale fabrication of different segments of the launch vehicle. Orbital ATK began casting propellant for the solid rocket boosters and manufacturing parts for the boosters in 2016. The company test fired a solid rocket booster in early 2015,^[80] and a second booster in June 2016.^[81]

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. The ICPS for EM-1 was slated for assembly in late January 2016, and a structural test article was delivered to NASA in 2015 for confidence testing.^[82]{{update after|2016|2}}

Program costs and funding

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.^[83]^[84] These costs and schedule were considered optimistic in an independent 2011 cost assessment report by Booz Allen Hamilton for NASA.^[85] 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),^[86]^[87] with the 130 t version ready no earlier than 2030.^[88]

The Human Exploration Framework Team (HEFT) estimated unit costs for Block 0 at $1.6bn and Block 1 at $1.86bn in 2010.^[89] However, since these estimates were made the Block 0 SLS vehicle was dropped in late 2011, and the design was not completed.^[90] The Space Review estimated the cost per launch at $5 billion, depending on the rate of launches.^[91]^[92] NASA announced in 2013 that the European Space Agency will build the Orion Service Module.^[93]

NASA SLS deputy project manager Jody Singer at Marshall Space Flight Center, Huntsville, Alabama 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.^[94] By comparison, a Saturn V launch cost US$185 to US$189 million in 1969-1971 dollars or roughly $1.23 billion in 2016 dollars adjusted for inflation.^[95]^[96]

On July 24, 2014, Government Accountability Office audit predicted that SLS would not launch by the end of 2017 as originally planned since NASA had not been receiving sufficient funding.^[97]

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.^[23] Ground systems modifications and construction would require an additional $1.8 billion over the same time period. {{asof|February 2015}} the Orion spacecraft was expected to enter its Key Decision Point C review in the first half of 2015.^[98]

For Fiscal Year 2015, NASA received an appropriation of {{USD|1.7 billion}} from Congress for SLS, an amount that was approximately {{USD|320 million}} greater than the amount requested by the Obama administration.^[99]

In October 2018, NASA's inspector general reported that the Boeing SLS stages contract portion (accounting "for over 40 percent of the $11.9 billion spent on the SLS Program" as of August 2018) is expected to cost a total of US$8.9 billion by 2021, which is twice the initial planned amount.^[100]

Funding history and planning

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.^[101]

For 2019 to 2023, NASA "notional"^[115] yearly budgets for SLS range from $2.1 to $2.3B a year. As of late 2015, the SLS program has a 70% confidence level for its "first Orion mission with astronauts by 2023" according to the Associate Administrator for NASA, Robert Lightfoot.^[116]^[117]^[118]

As of mid-2018, the SLS is scheduling its first test launch, with no crew, for mid-2020.^[119]

There are no NASA estimates for the SLS program recurring yearly costs once operational, for a certain flight rate per year, or for the resulting average costs per flight. Bill Hill, NASA manager of exploration systems development has indicated "My top number for Orion, SLS, and the ground systems that support it is $2 billion or less" (annually).^[120] NASA associate administrator William H. Gerstenmaier has indicated, "[per mission] costs must be derived from the data and are not directly available. This was done by design to lower NASA's expenditures."^[121]

Criticism

The Space Access Society, Space Frontier Foundation and The Planetary Society called for cancellation of the project in 2011–12, arguing that SLS will consume the funds for other projects from the NASA budget and will not reduce launch costs.^[122]^[123]^[124] U.S. Representative Dana Rohrabacher and others added that instead, an orbital propellant depot should be developed and the Commercial Crew Development program accelerated.^[122]^[125]^[126]^[127]^[128] Two studies, one not publicly released from NASA^[129]^[130] and another from the Georgia Institute of Technology, show this option to be possibly cheaper.^[131]^[132]

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.^[133]^[134]^[135]^[136]^[137] 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.^[138]

Mars Society founder Robert Zubrin, who co-authored the Mars Direct concept, 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.^[139] SpaceX's CEO Elon Musk stated in 2010 that he would "personally guarantee" that his company could build a launch 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.^[140]^[141] Musk went on to start development of the fully reusable BFR super-heavy launcher and upper stage Starship in the early 2010s. Because of this reusability, Musk claims that it will be the lowest cost super-heavy launcher ever made.^[142] 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.

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).^[123]^[143]^[144] Opponents of the heavy launch vehicle have critically used the name "Senate launch system".^[53] 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".^[122]

In 2013, Chris Kraft, the NASA mission control leader from the Apollo era, expressed his criticism of the system as well.^[145] Lori Garver, former NASA Deputy Administrator, has called for cancelling the program.^[146] 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.^[147]

Doubts have also been expressed about the utility and cost of depots.^[148] "Patrick R. Chai and Alan W. Wilhite of Georgia Tech presented a study early in 2011 estimating that depot tanks would lose about $12 million worth of propellant per month in low Earth orbit if protected only with passive insulation."^[149]{{context inline|this needs explication in context of other costs, dev cost of SLS, or monthly cost of SLS when it eventually reaches its NASA planned launch rate; a monthly propellant boiloff cost is not useful without context.|date=March 2018}}

Missions

The list below includes only NASA planned missions published in April 2017,^[151] and updated in September 2018.^[152]

Gallery

See also

Notes

1. ^{{cite news|title=NASA commits to $7 billion mega rocket, 2018 debut |url=http://www.cbsnews.com/news/nasa-commits-to-heavy-lift-mega-rocket/|accessdate=2015-03-13|publisher=CBS News|date=August 27, 2014}}
2. ^{{cite web |url=https://www.nasa.gov/exploration/systems/sls/SLSpresentation.html |title=SLS Carries Deep Space Potential |first=Steven |last=Siceloff |date=April 12, 2015|website=Nasa.gov|accessdate=2 January 2018}}
3. ^{{cite web |url=http://www.iflscience.com/space/worlds-most-powerful-deep-space-rocket-set-launch-2018/ |title=World's Most Powerful Deep Space Rocket Set To Launch In 2018 |website=Iflscience.com|accessdate=2 January 2018}}
4. ^{{cite web |url=http://www.airspacemag.com/space/bigger-saturn-bound-deep-space-180952802/ |title=Bigger Than Saturn, Bound for Deep Space |first=James R. |last=Chiles|website=Airspacemag.com|accessdate=2 January 2018}}
5. ^{{cite web |url=https://arstechnica.com/science/2017/03/for-the-first-time-nasa-has-begun-detailing-its-deep-space-exploration-plans/ |title=Finally, some details about how NASA actually plans to get to Mars |website=Arstechnica.com|accessdate=2 January 2018}}
6. ^{{cite web |url=https://www.nasa.gov/exploration/systems/sls/nasa-continues-testing-manufacturing-worlds-most-powerful-rocket |title=NASA Continues Testing, Manufacturing World’s Most Powerful Rocket |first=Jennifer |last=Harbaugh|website=Nasa.gov |date=May 12, 2017}}
7. ^{{cite web |url=http://www.space.com/33691-space-launch-system-most-powerful-rocket.html |title=Yes, NASA's New Megarocket Will Be More Powerful Than the Saturn V |website=Space.com |first=Mike |last=Wall |date=August 16, 2016 |access-date=September 13, 2018}}
8. ^SLS has greater thrust than Saturn V but a lower payload capability.
9. ^{{cite web |url=https://www.cnbc.com/2016/01/26/boeing-builds-the-most-powerful-rocket-ever-made.html |title=Boeing builds the most powerful rocket ever made |first=Jane |last=Wells |work=cnbc.com |date=January 26, 2016}}
10. ^{{cite web |url=https://newatlas.com/nasa-space-launch-system-sls-critical-design-review/38612/ |title=Most powerful rocket ever edges closer to lift-off |work=New Atlas |first=Anthony |last=Wood |date=July 25, 2015 |access-date=September 13, 2018}}
11. ^{{cite web |url=http://www.aerospaceguide.net/spacerocket/space-launch-system.html |title=Space Launch System |work= aerospaceguide.net}}
12. ^{{cite web |url=http://www.nasa.gov/home/hqnews/2011/may/HQ_11-164_MPCV_Decision.html |publisher=NASA |date=24 May 2011 |title=NASA Announces Key Decision For Next Deep Space Transportation System |accessdate=26 January 2012}}
13. ^{{cite web |url=http://www.nasa.gov/home/hqnews/2011/sep/HQ_11-301_SLS_Decision.html |title=NASA Announces Design For New Deep Space Exploration System |publisher=NASA |date=September 14, 2011 |accessdate=2011-09-14}}
14. ^{{cite web |url=http://www.c-span.org/Events/Press-Conference-on-the-Future-of-NASA-Space-Program/10737424158/ |title=Press Conference on the Future of NASA Space Program |publisher=C-Span |date=September 14, 2011 |accessdate=2011-09-14}}
15. ^{{cite news |url=https://www.nytimes.com/2011/09/15/science/space/15nasa.html?pagewanted=1&_r=1 |title=NASA Unveils New Rocket Design |work=New York Times |author=Kenneth Chang |date=September 14, 2011 |accessdate=2011-09-14}}
16. ^¹²³{{cite web |website=NASASpaceFlight.com |accessdate=2012-01-26 |url=http://www.nasaspaceflight.com/2011/10/sls-trades-opening-four-rs-25s-core-stage/ |date=October 4, 2011 |author=Chris Bergin |title=SLS trades lean towards opening with four RS-25s on the core stage}}
17. ^¹{{cite web |location=Washington DC, United States |url=http://commerce.senate.gov/public/index.cfm?p=Legislation&ContentRecord_id=8d7c1465-f852-4835-ba84-25faf56bbb36&ContentType_id=03ab50f5-55cd-4934-a074-d6928b9dd24c&Group_id=6eaa2a03-6e69-4e43-8597-bb12f4f5aede |work=Featured Legislation |title=The NASA Authorization Act of 2010 |date= July 15, 2010 |publisher=United States Senate |accessdate= May 26, 2011}}
18. ^{{cite web |url=http://www.space.com/12957-nasa-giant-rocket-space-launch-system-infographic.html |title=Space Launch System: NASA's Giant Rocket Explained |author=Karl Tate |date=16 September 2011 |website=Space.com |accessdate=26 January 2012}}
19. ^{{cite web |url=http://www.thespacereview.com/article/2410/1 |title=Burning thunder |author= Dwayne Day |date= November 25, 2013 |accessdate=}}
20. ^¹[https://www.cbo.gov/sites/default/files/109th-congress-2005-2006/reports/10-09-spacelaunch.pdf The Congress of the United States. Congressional Budget Office, October 2006, pp. X,1,4,9.] "The Apollo Saturn V launch vehicle had a lift capability of 140 metric tons to low Earth orbit."
21. ^{{cite web|url=https://books.google.com/books?id=Zn4gAQAAIAAJ&q=%22Apollo+Saturn+V+launch+vehicle+had%22&dq=%22Apollo+Saturn+V+launch+vehicle+had%22&hl=en&sa=X&ved=0CB8Q6AEwAGoVChMI44uQwcHyxgIVDxaSCh1rLQk_|title=America at the Threshold - Report of the Synthesis Group on America's Space Exploration Initiative|year=1991|page=31|author=Thomas P. Stafford}}
22. ^{{cite web |url=http://www.nasa.gov/exploration/systems/sls/sls-pdr.html |publisher=NASA |date=1 August 2013 |title=NASA's Space Launch System Program PDR: Answers to the Acronym |accessdate=3 August 2013}}
23. ^¹{{cite news|last1=Foust|first1=Jeff|title=SLS Debut Likely To Slip to 2018|url=http://spacenews.com/41690sls-debut-likely-to-slip-to-2018/|accessdate=2015-03-12|publisher=SpaceNews.com|date=August 27, 2014}}
24. ^{{cite news |url=https://spaceflightnow.com/2017/04/28/nasa-confirms-first-flight-of-space-launch-system-will-slip-to-2019/ |title=NASA confirms first flight of Space Launch System will slip to 2019 |work=Spaceflight Now |first=Stephen |last=Clark |date=28 April 2017 |access-date=29 April 2017}}
25. ^¹²{{cite web |url=http://www.nasa.gov/pdf/664158main_sls_fs_master.pdf |title=space launch system |date=2012 |archive-url=https://web.archive.org/web/20120813043824/http://www.nasa.gov/pdf/664158main_sls_fs_master.pdf |archive-date=2012-08-13 |website=NASAfacts |dead-url=yes}}
26. ^{{cite web|last1=Sloss|first1=Philip|title=NASA ready to power up the RS-25 engines for SLS |url=http://www.nasaspaceflight.com/2015/01/nasa-ready-power-up-rs-25-engine/ |website=NASASpaceFlight.com |accessdate=2015-03-10}}
27. ^¹{{cite news |title=NASA to set exploration architecture this summer |author=Stephen Clark |url=http://spaceflightnow.com/news/n1103/31slsmpcv/ |publisher=Spaceflight Now |date= March 31, 2011 |accessdate=26 May 2011}}
28. ^{{cite web |url=http://www.nasaspaceflight.com/2011/09/sls-finally-announced-nasa-forward-path/ |title=SLS finally announced by NASA – Forward path taking shape |date=14 September 2011 |website=NASASpaceFlight.com |accessdate=26 January 2012 |author=Chris Bergin}}
29. ^{{cite web |url=http://www.space-travel.com/reports/NASA_Space_Launch_System_Core_Stage_Passes_Major_Milestone_Ready_to_Start_Construction_999.html |publisher=Space Travel |date=27 December 2012 |title=NASA's Space Launch System Core Stage Passes Major Milestone, Ready to Start Construction}}
30. ^{{cite web |date= April 25, 2011 |url=http://www.nasaspaceflight.com/2011/04/sls-planning-dual-phase-approach-opening-sd-hlv/ |website=NASASpaceFlight.com |author=Chris Bergin|title=SLS planning focuses on dual phase approach opening with SD HLV |accessdate= January 26, 2012}}
31. ^{{cite web |url=http://www.nasaspaceflight.com/2011/06/managers-sls-announcement-after-sd-hlv-victory/ |website=NASASpaceFlight.com |date= June 16, 2011 |author= Bergin, Chris |title=Managers SLS announcement after SD HLV victory |accessdate= January 26, 2012}}
32. ^¹{{cite news |url=http://www.nasaspaceflight.com/2012/02/acronyms-ascent-sls-managers-create-developmental-milestone-roadmap/ |title=Acronyms to Ascent – SLS managers create development milestone roadmap |website=NASASpaceFlight.com |first= Chris |last=Bergin |date=23 February 2012 |access-date=9 April 2012}}
33. ^{{cite web|last1=Priskos|first1=Alex|title=Five-segment Solid Rocket Motor Development Status|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120014501.pdf|website=ntrs.nasa.gov|publisher=NASA|accessdate=2015-03-11}}
34. ^{{cite web |url=http://www.nasaspaceflight.com/2012/02/sls-how-to-launch-nasas-new-monster-rocket/ |title=Space Launch System: How to launch NASA's new monster rocket |website=NASASpaceflight.com |date=20 February 2012 |accessdate=9 April 2012}}
35. ^{{cite web |url=http://www.nasa.gov/mission_pages/constellation/ares/dm1_success.html |title=NASA and ATK Successfully Test Ares First Stage Motor|publisher=NASA |date=10 September 2009 |accessdate=30 January 2012}}
36. ^{{cite web |url=http://www.nasa.gov/mission_pages/constellation/ares/10-202.html |title=NASA and ATK Successfully Test Five-Segment Solid Rocket Motor |publisher=NASA |date=31 August 2010 |accessdate=30 January 2012}}
37. ^{{Cite web |url=http://www.nasa.gov/exploration/features/dm3.html |title=NASA Successfully Tests Five-Segment Solid Rocket Motor |publisher=NASA |date=31 August 2010 |accessdate=8 September 2011}}
38. ^{{cite news|last1=Bergin|first1=Chris|title=QM-1 shakes Utah with two minutes of thunder|url=http://www.nasaspaceflight.com/2015/03/qm-1-shake-utah-two-minutes-thunder/|accessdate=March 10, 2015|website=NASASpaceFlight.com |date=March 10, 2015}}
39. ^{{cite web|url=http://www.spaceref.com/news/viewnews.html?id=1567|title=NASA's New Space Launch System Announced – Destination TBD|date=September 14, 2011|publisher=SpaceRef|author=Keith Cowing|accessdate=January 26, 2012}}
40. ^{{cite web |url=http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/awx/2011/06/16/awx_06_16_2011_p0-337088.xml&headline=NASA%20Will%20Compete%20Space%20Launch%20System%20Boosters |title=NASA Will Compete Space Launch System Boosters |author=Frank Morring |publisher=Aviation Week |date=17 June 2011 |accessdate=20 June 2011}}
41. ^{{cite web|title=NASA's Space Launch System: Partnering For Tomorrow|url=http://www.asee.org/Crumbly_ASEE_Final.pdf|publisher=NASA|accessdate=2013-03-12}}
42. ^{{cite web |url=http://www.nasa.gov/home/hqnews/2013/feb/HQ_13-054_Aerojet_SLS_Boosters.html |title=NASA Awards Final Space Launch System Advanced Booster Contract |author=Rachel Kraft |publisher=NASA |date= February 14, 2013 |accessdate= February 19, 2013}}
43. ^{{cite news|url=http://www.nasaspaceflight.com/2013/01/the-dark-knights-atks-advanced-booster-revealed-for-sls/|title=The Dark Knights – ATK's Advanced Boosters for SLS revealed |website=NASASpaceFlight.com |date=2013-01-14}}
44. ^¹²³⁴{{cite web|last1=Bergin|first1=Chris|title=Advanced Boosters progress towards a solid future for SLS|url=http://www.nasaspaceflight.com/2015/02/advanced-boosters-towards-solid-future-sls/ |website=NasaSpaceFlight.com |accessdate=February 25, 2015}}
45. ^{{cite web |url=http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=30862.0;attach=515287;image |title=Table 2. ATK Advanced Booster Satisfies NASA Exploration Lift Requirements |website=NASASpaceFlight.com}}
46. ^{{cite news|url=https://arstechnica.com/science/2013/04/new-f-1b-rocket-engine-upgrades-apollo-era-deisgn-with-1-8m-lbs-of-thrust/ |title=New F-1B rocket engine upgrades Apollo-era design with 1.8M lbs of thrust|author=Lee Hutchinson |publisher=Ars Technica|date=2013-04-15|accessdate=2013-04-15}}
47. ^{{cite news |url=https://arstechnica.com/science/2013/08/dynetics-reporting-outstanding-progress-on-f-1b-rocket-engine/ |title=Dynetics reporting "outstanding" progress on F-1B rocket engine |publisher=Ars Technica |date=2013-08-13 |accessdate=2013-08-13}}
48. ^{{cite news |url=https://arstechnica.com/science/2013/04/new-f-1b-rocket-engine-upgrades-apollo-era-deisgn-with-1-8m-lbs-of-thrust/ |title=New F-1B rocket engine upgrades Apollo-era design with 1.8M lbs of thrust |author=Lee Hutchinson |publisher=Ars Technica |date=2013-04-15 |accessdate=2013-04-15}}
49. ^{{cite news |url=http://www.nasaspaceflight.com/2012/11/dynetics-pwr-liquidize-sls-booster-competition-f-1-power/ |title=Dynetics PWR liquidize SLS booster competition |website=NASASpaceFlight.com |date=November 2012}}
50. ^{{cite web |url=http://www.thespacereview.com/article/2217/1 |title=SLS Block II drives hydrocarbon engine research |work= thespacereview.com |date= January 14, 2013}}
51. ^{{cite web |url=http://www.nasaspaceflight.com/2012/07/wind-tunnel-testing-sls-configurations-block-1b/|title=Wind Tunnel testing conducted on SLS configurations, including Block 1B |website=NASASpaceFlight.com |author=|date= }}
52. ^{{cite web |url= http://www.spacenews.com/article/civil-space/40647news-from-the-30th-space-symposium-second-sls-mission-might-not-carry-crew |title= Second SLS Mission Might Not Carry Crew |date= May 21, 2014 |website= spacenews.com |publisher= |accessdate= July 25, 2014}}
53. ^¹Rosenberg, Zach. "Delta second stage chosen as SLS interim". Flight International, May 8, 2012.
54. ^{{cite web|title=Space Launch System Data Sheet|url=http://www.spacelaunchreport.com/sls0.html|website=SpaceLaunchReport.com|accessdate=July 25, 2014}}
55. ^{{cite web |title=NASA confirms EUS for SLS Block 1B design and EM-2 flight |url=http://www.nasaspaceflight.com/2014/06/nasa-confirms-eus-sls-block-ib-design-em-2-flight/ |website=NASASpaceFlight.com |accessdate=24 July 2014}}
56. ^¹{{cite web |url=http://www.nasaspaceflight.com/2013/06/sls-pdr-evolved-rocket-dual-upper-stage/ |title=SLS prepares for PDR – Evolution eyes Dual-Use Upper Stage |website=NASASpaceFlight.com |accessdate=2015-03-12}}
57. ^[https://arstechnica.com/science/2018/04/nasa-likely-to-fly-first-deep-space-mission-on-less-powerful-rocket/ NASA may fly crew into deep space sooner, but there’s a price]. Eric Berger. Ars Technica. 12 April 2018. Quote: "Without the Exploration Upper Stage, NASA will not be able to fly, in a single flight, crew members and pieces of a deep space gateway it hopes to build near the Moon in the 2020s."
58. ^{{cite web |url=http://www.nasaspaceflight.com/2011/11/sls-j-2x-upper-stage-engine-500-second-test-fire/ |title=SLS J-2X Upper Stage engine enjoys successful 500 second test fire |author=Chris Bergin |website=NASASpaceFlight.com |date=November 9, 2011}}
59. ^{{cite web |url=http://www.nasaspaceflight.com/2013/02/second-j-2x-engine-sls-testing/ |title=Second J-2X engine prepares for SLS testing |author= Chris Bergin |website=NASASpaceFlight.com |date= February 12, 2013}}
60. ^{{cite web |url=http://www.nasaspaceflight.com/2013/11/sls-us-proposals-increasing-payload-destination-options/ |title=SLS upper stage proposals reveal increasing payload-to-destination options |date= November 13, 2013 |website=NASASpaceFlight.com |author= Chris Gebhardt}}
61. ^{{cite web |url=http://seradata.com/SSI/2013/06/sls-may-change-upper-stage-eng/ |title=SLS design may ditch J-2X upper stage engine for four RL-10 engines |archive-url=https://web.archive.org/web/20160304043940/http://seradata.com/SSI/2013/06/sls-may-change-upper-stage-eng/ |archive-date=2016-03-04 |author=David Todd |date=June 3, 2013 |website=Seradata}}
62. ^{{cite web |url=http://seradata.com/SSI/2014/11/next-steps-for-sls-europes-vinci-is-a-contender-for-exploration-upper-stage-engine/ |title=Next Steps for SLS: Europe’s Vinci is a contender for Exploration Upper-Stage Engine |author=David Todd |date=November 7, 2014 |website=Seradata |archive-url=https://web.archive.org/web/20160304023658/http://seradata.com/SSI/2014/11/next-steps-for-sls-europes-vinci-is-a-contender-for-exploration-upper-stage-engine/ |archive-date=2016-03-04}}
63. ^{{cite web |url=http://www.thespacereview.com/article/2561/1 |title=A generational opportunity for Europa |author= Casey Dreier |date=July 21, 2014}}
64. ^{{cite web |url=http://www.space-travel.com/reports/NASA_Researchers_Studying_Advanced_Nuclear_Rocket_Technologies_999.html |title=NASA Researchers Studying Advanced Nuclear Rocket Technologies |author= |date= |work=space-travel.com}}
65. ^{{cite magazine |magazine=National Security Science |url=http://www.lanl.gov/science/NSS/issue1_2011/story4full.shtml |title=Nuclear Rockets: To Mars and Beyond |authors=Brian Fishbine, Robert Hanrahan, Steven Howe, Richard Malenfant, Carolynn Scherer, Haskell Sheinberg, and Octavio Ramos Jr. |publisher=Los Alamos National Laboratory |date=December 2016}}
66. ^{{cite web |url=http://image.gsfc.nasa.gov/poetry/venus/q2811.html |title=How long would a trip to Mars take? |publisher=NASA}}
67. ^{{cite web |url=http://www.adastrarocket.com/aarc/NEP-Mars |title=How Fast Could (Should) We Go to Mars? Comparing Nuclear Electric Propulsion (NEP) with the Nuclear Thermal Rocket (NTR) and Chemical Rocket for Sustainable 1-year human Mars round-trip mission}}
68. ^¹{{cite conference |authors=Laura M. Burke, Stanley K. Borowski, David R. McCurdy and Thomas Packard |conference=49th AIAA/ASME/SAE/ASEE Joint Propulsion Conference San Jose, CA |url=http://arc.aiaa.org/doi/pdf/10.2514/6.2013-4076 |title=A One-year Round Trip Crewed Mission to Mars using Bimodal Nuclear Thermal and Electric Propulsion (BNTEP) |doi=10.2514/6.2013-4076 |website=ARC}}
69. ^¹{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120003776.pdf |title=Nuclear Thermal Propulsion (NTP): A Proven Growth Technology for Human NEO / Mars Exploration Missions |publisher=NASA |date=April 9, 2012 |author1=Borowski, Stanley K. |author2=McCurdy, David R. |author3=Packard, Thomas W.}}
70. ^{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120012928.pdf |title=Nuclear Thermal Rocket/Vehicle Characteristics And Sensitivity Trades For NASA's Mars Design Reference Architecture (DRA) 5.0 Study |publisher=NASA |date=August 16, 2012 |author1=Borowski, Stanley K. |author2=McCurdy, David R. |author3=Packard, Thomas W.}}
71. ^{{cite web |url=http://www.nasaspaceflight.com/2012/01/sls-exploration-roadmap-pointing-dual-mars-approach/ |website=NASASpaceFlight.com |accessdate=26 January 2012 |author=Chris Bergin |date=24 January 2012 |title=SLS Exploration Roadmap evaluations provide clues for human Mars missions}}
72. ^{{cite web |url=http://www.space-travel.com/reports/NASA_Researchers_Studying_Advanced_Nuclear_Rocket_Technologies_999.html |title=NASA Researchers Studying Advanced Nuclear Rocket Technologies |author=Rick Smith for Marshall Space Flight Center, Huntsville AL (SPX) |date=Jan 10, 2013}}
73. ^{{cite web |url=https://www.nasa.gov/centers/marshall/news/news/releases/2017/nasa-contracts-with-bwxt-nuclear-energy-to-advance-nuclear-thermal-propulsion-technology.html |title=NASA Contracts with BWXT Nuclear Energy to Advance Nuclear Thermal Propulsion Technology. Aug 2017}}
74. ^¹²³⁴⁵⁶⁷⁸{{cite web |url=https://www.nasa.gov/exploration/systems/sls/to-the-moon.html |title=The Great Escape: SLS Provides Power for Missions to the Moon |publisher=NASA |first=Jennifer |last=Harbaugh |date=9 July 2018 |access-date=4 September 2018}}
75. ^¹{{cite web |url=https://www.nasa.gov/sites/default/files/atoms/files/sls_fact_sheet_final_10112017.pdf |title=Space Launch System |series=NASA Facts |publisher=NASA |date=11 October 2017 |accessdate=4 September 2018 |id=FS-2017-09-92-MSFC}}
76. ^¹{{cite web |first=Stephen |last=Creech |publisher=NASA |url=https://www.nasa.gov/sites/default/files/files/Creech_SLS_Deep_Space.pdf |title=NASA's Space Launch System: A Capability for Deep Space Exploration |page=2 |date=April 2014 |access-date=4 September 2018}}
77. ^{{cite web |url=http://www.nasa.gov/sls/14-171.html#.VGfrNb4_ypc |title=SLS Engine Section Barrel Hot off the Vertical Weld Center at Michoud |website=NASA}}
78. ^{{cite web|url=http://www.nasaspaceflight.com/2012/04/sls-robust-face-scrubs-launch-delays-pad-stays/ |title=SLS to be robust in the face of scrubs, launch delays and pad stays |website=NASASpaceFlight.com |date=4 April 2012 |accessdate=9 April 2012}}
79. ^¹{{cite web |last1=Campbell |first1=Lloyd |title=NASA conducts 13th test of Space Launch System RS-25 engine |url=http://www.spaceflightinsider.com/space-centers/stennis-space-center/nasa-conducts-13th-test-space-launch-system-rs-25-engine/ |publisher=SpaceflightInsider.com |date=25 March 2017 |accessdate=29 April 2017}}
80. ^{{cite news |last1=Bergin |first1=Chris |title=QM-1 examinations boost as QM-2 prepares for casting |url=https://www.nasaspaceflight.com/2015/05/qm-1-examinations-boost-qm-2-casting/ |accessdate=2016-06-28 |website=NASASpaceFlight.com |date=May 13, 2015}}
81. ^{{cite news |last1=Sloss |first1=Philip |title=QM-2: Orbital ATK fires up SLS booster for final qualification test |url=https://www.nasaspaceflight.com/2016/06/qm-2-orbital-atk-sls-booster-static-fire-test/ |accessdate=2016-06-28 |website=NASASpaceFlight.com |date=June 27, 2016}}
82. ^{{cite web |title=NASA facilities, teams ramp up SLS flight production for 2018 maiden flight |url=http://www.nasaspaceflight.com/2016/01/nasa-facilities-ramp-up-sls-2018-flight/ |website=NASASpaceFlight.com |accessdate=2016-01-26}}
83. ^{{cite web |url=http://www.spacepolicyonline.com/news/new-nasa-crew-transportation-system-to-cost-18-billion-through-2017 |title=New NASA Crew Transportation System to Cost $18 Billion Through 2017 |publisher=Space Policy Online |date=14 September 2011 |accessdate=15 September 2011 |author=Marcia Smith}}
84. ^{{cite AV media |url=http://www.c-span.org/video/?301537-1/future-nasa-space-program |title=Future of NASA Space Program |publisher=Cspan.org |date=September 14, 2011 |people=Bill Nelson, Kay Bailey Hutchison, Charles F. Bolden |location=Washington, D.C.}}
85. ^{{cite web |url=http://www.nasa.gov/pdf/581582main_BAH_Executive_Summary.pdf |title=Independent Cost Assessment of the Space Launch System, Multi-purpose Crew Vehicle and 21st Century Ground Systems Programs: Executive Summary of Final Report |website=NASA |author=Booz Allen Hamilton |date=August 19, 2011}}
86. ^¹{{cite web |url=https://www.wsj.com/articles/SB10001424053111903648204576555010831469864 |title=White House Experiences Sticker Shock Over NASA's Plans |publisher=The Wall Street Journal |date=September 7, 2011 |accessdate=2015-02-22 |author=Andy Paszior}}
87. ^¹{{cite web |url=http://spacepolicyonline.com/pages/images/stories/SLS_budget_Integration_2011-08.pdf |title=ESD Integration, Budget Availability Scenarios |publisher=Space Policy Online |date=19 August 2011 |format=PDF |accessdate=15 September 2011}}
88. ^{{cite web |url=http://www.spacepolicyonline.com/news/the-nasa-numbers-behind-that-wsj-article |title=The NASA Numbers Behind That WSJ Article |author=Marcia Smith |publisher=Space Policy Online |date= 9 September 2011 |accessdate=15 September 2011}}
89. ^{{cite web |url=http://www.nasawatch.com/images/heft.presentation.pdf |title=HEFT Phase I Closeout |page= 69 |publisher= nasawatch.com |date= September 2010 |accessdate=}}
90. ^{{cite web |url=http://www.nasaspaceflight.com/2011/10/sls-trades-opening-four-rs-25s-core-stage/ |title=SLS trades lean towards opening with four RS-25s on the core stage |author=Chris Bergin |date=4 October 2011 |website=NASASpaceFlight.com |accessdate=16 September 2013}}
91. ^{{cite web |website=AL.com |url=http://blog.al.com/breaking/2013/07/nasa_defends_space_launch_syst.html |title=NASA defends Space Launch System against charge it 'is draining the lifeblood' of space program |date=July 29, 2013 |author=Lee Roop |accessdate=18 February 2015}}
92. ^{{cite web |url=http://www.thespacereview.com/article/2330/1 |title=Revisiting SLS/Orion launch costs |publisher=The Space Review |date=July 15, 2013 |author=John Strickland |accessdate=18 February 2015}}
93. ^{{cite web |url=http://www.nasa.gov/exploration/systems/mpcv/orion_feature_011613.html |title=NASA Signs Agreement for a European-Provided Orion Service Module |orig-year=January 16, 2013 |editor=NASA Content Administrator |date=April 12, 2015 |website=NASA |accessdate= |deadurl=yes |archiveurl=https://web.archive.org/web/20130118034139/https://www.nasa.gov/exploration/systems/mpcv/orion_feature_011613.html |archivedate=January 18, 2013 |df=mdy-all}}
94. ^{{cite web |url=http://www.msnbc.msn.com/id/49019843/ns/technology_and_science-space/#.UFIyOxii5i4 |title=NASA's huge new rocket may cost $500 million per launch |publisher=MSNBC |date=September 12, 2012 |accessdate=}}
95. ^{{cite web |url=https://history.nasa.gov/SP-4221/ch6.htm |title=SP-4221 The Space Shuttle Decision- Chapter 6: ECONOMICS AND THE SHUTTLE |accessdate=2011-01-15 |publisher=NASA}}
96. ^{{cite web |url=https://history.nasa.gov/SP-4029/Apollo_18-16_Apollo_Program_Budget_Appropriations.htm |title=Apollo Program Budget Appropriations |author= |date= |work=NASA}}
97. ^{{cite web |url=http://www.waff.com/story/26100126/federal-audit-reveals-nasa-doesnt-have-enough-money-to-get-sls-off-the-ground?clienttype=generic&mobilecgbypass |title=Federal audit reveals not enough money for NASA to get SLS off the ground |date=July 24, 2014|author1=Morrison, Lauren |author2=Bale, Lauren |publisher=48 WAFF}}
98. ^{{cite web |last1=Davis |first1=Jason |title=NASA Budget Lists Timelines, Costs and Risks for First SLS Flight |url=http://www.planetary.org/blogs/jason-davis/2015/20150203-budget-maiden-sls-flight.html|publisher=The Planetary Society|accessdate=2015-03-11}}
99. ^{{cite news |last1=Clark |first1=Stephen |title=NASA gets budget hike in spending bill passed by Congress |url=http://spaceflightnow.com/2014/12/14/nasa-gets-budget-hike-in-spending-bill-passed-by-congress/ |accessdate=2014-12-15 |work=Spaceflight Now |date=2014-12-14}}
100. ^{{cite web |url=https://oig.nasa.gov/docs/IG-19-001.pdf |title=NASA’S MANAGEMENT OF THE SPACE LAUNCH SYSTEM STAGES CONTRACT |date=October 10, 2018 |website=NASA OIG |publisher=NASA Office of Inspector General Office of Audits |access-date=October 14, 2018}}
101. ^{{cite web |url=http://www.nasa.gov/sites/default/files/files/2013_NNSI_FY14(1).xlsx |title=NASA New Start Inflation Indices |last= |first= |date= |publisher=National Aeronautics and Space Administration |access-date=June 23, 2016}}
102. ^{{cite web |url=https://www.nasa.gov/sites/default/files/659660main_NASA_FY13_Budget_Estimates-508-rev.pdf |title=FY 2013 Presidents Budget Request Summary |last= |first= |date= |publisher=National Aeronautics and Space Administration |page=BUD-4 |access-date=June 23, 2016}}
103. ^{{cite web |url=http://www.gao.gov/assets/680/676179.pdf |title=NASA, Assessments of Major Projects |last= |first= |date=March 2016 |publisher=General Accounting Office |page=63 |access-date=June 23, 2016}}
104. ^{{cite web |url=http://www.nasa.gov/pdf/750614main_NASA_FY_2014_Budget_Estimates-508.pdf |title=FY 2014 Presidents Budget Request Summary |last= |first= |date= |publisher=National Aeronautics and Space Administration |page=BUD-8 |access-date=June 23, 2016}}
105. ^{{cite web |url=http://www.nasa.gov/sites/default/files/files/508_2015_Budget_Estimates.pdf |title=FY 2015 Presidents Budget Request Summary |last= |first= |date= |publisher=National Aeronautics and Space Administration |page=BUD-5 |access-date=June 23, 2016}}
106. ^¹{{cite web |url=http://www.nasa.gov/sites/default/files/atoms/files/fy2016_budget_book_508_tagged_0.pdf |title=FY 2016 Presidents Budget Request Summary |last= |first= |date= |publisher=National Aeronautics and Space Administration |page=BUD-5 |access-date=June 23, 2016}}
107. ^¹{{cite web |url=https://www.nasa.gov/sites/default/files/atoms/files/fy_2018_budget_estimates.pdf |title=FY 2018 Budget Estimates |last= |first= |date= |website=|publisher=National Aeronautics and Space Administration |page=BUD-3 |access-date=December 16, 2018 |archive-url= |archive-date= |dead-url=}}
108. ^¹{{cite web |url=https://www.congress.gov/bill/115th-congress/house-bill/244/text |title=H.R.244 - Consolidated Appropriations Act, 2017 |last= |first= |date=2017 |website=congress.gov |access-date=December 16, 2018 |archive-url= |archive-date=|dead-url=}}
109. ^¹{{cite web |url=https://www.govinfo.gov/content/pkg/BILLS-115hr1625enr/html/BILLS-115hr1625enr.htm |title=Consolidated Appropriations Act, 2018 |last= |first= |date= |website=govinfo.gov |access-date=December 16, 2018 |archive-url= |archive-date= |dead-url=}}
110. ^¹{{cite web |url=http://www.nasa.gov/pdf/345225main_FY_2010_UPDATED_final_5-11-09_with_cover.pdf |title=Fiscal Year 2010 Budget Estimates |last= |first= |date= |publisher=National Aeronautics and Space Administration |page=v |access-date=June 23, 2016}}
111. ^{{cite web |url=http://www.nasa.gov/pdf/168652main_NASA_FY08_Budget_Request.pdf |title=FY 2008 Budget Estimates |last= |first= |date= |website=|publisher=National Aeronautics and Space Administration |page=ESMD-14 |access-date=June 23, 2016}}
112. ^{{cite web |url=https://www.youtube.com/watch?v=yd_Bg7K6Jt0 |title=NASA's Ground Systems Development and Operations Program Completes Preliminary Design Review |last= |first= |date= |publisher=National Aeronautics and Space Administration |access-date=June 23, 2016}}
113. ^{{cite web |url=https://govtribe.com/award/federal-contract-award/definitive-contract-nnm12aa82c |title=Definitive Contract NNM12AA82C |last= |first= |date= |website=govtribe.com |access-date=December 16, 2018 |archive-url= |archive-date= |dead-url=}}
114. ^{{cite web |url=https://docs.house.gov/billsthisweek/20151214/CPRT-114-HPRT-RU00-SAHR2029-AMNT1final.pdf |title=Consolidated Appropriations Act 2016 |last= |first= |date= |website=house.gov |page=183 |access-date=December 16, 2018 |archive-url= |archive-date=| dead-url=}}
115. ^{{cite web |url=https://www.nasa.gov/sites/default/files/atoms/files/fy19_nasa_budget_estimates.pdf |title=NASA FY 2019 Budget Estimates |last= |first= |date= |website=nasa.gov |page=BUD-2 |archive-url= |archive-date=|dead-url= |access-date=December 16, 2018}}
116. ^{{cite web |url=http://spacenews.com/first-crewed-orion-mission-may-slip-to-2023/ |title=First Crewed Orion Mission May Slip to 2023 |last=Foust |first=Jeff |date=September 16, 2015 |website= SpaceNews.com |access-date=June 23, 2016}}
117. ^{{cite web |url=https://spaceflightnow.com/2015/09/16/orion-spacecraft-may-not-fly-with-astronauts-until-2023/ |title=Orion spacecraft may not fly with astronauts until 2023 |last=Clark |first=Stephen |date=September 16, 2015 |website= spaceflightnow.com |access-date=June 23, 2016}}
118. ^{{cite web |url=http://www.spacepolicyonline.com/news/mikulski-deeply-troubled-by-nasas-budget-request-sls-wont-use-70-percent-jcl |title=Mikulski "Deeply Troubled" by NASA's Budget Request; SLS Won't Use 70 Percent JCL |last=Clark |first=Smith |date=May 1, 2014 |website= spacepolicyonline.com |access-date=June 23, 2016}}
119. ^{{cite web |url=https://spacenews.com/nasa-adding-more-sls-block-1-launches-to-manifest/ |title=NASA adding more SLS Block 1 launches to manifest |last=Foust |first=Jeff |date= |website=spacenews.com |access-date=December 16, 2018 |archive-url= |archive-date=|dead-url=}}
120. ^{{cite web |url=https://arstechnica.com/science/2016/08/how-much-will-sls-and-orion-cost-to-fly-finally-some-answers/ |title=How much will SLS and Orion cost to fly? Finally some answers |last=Berger |first=Eric |date=August 19, 2016 |website=arstechnica.com |access-date=December 16, 2018 |archive-url= |archive-date= |dead-url=}}
121. ^{{cite web |url=https://arstechnica.com/science/2017/10/nasa-chooses-to-not-tell-congress-how-much-deep-space-missions-cost/ |title=NASA chooses not to tell Congress how much deep space missions cost |last=Berger |first=Eric |date=October 20, 2017 |website=arstechnica.com |access-date=December 16, 2018 |archive-url= |archive-date= |dead-url=}}
122. ^¹²{{cite web |url=http://moonandback.com/2011/09/15/impossibly-high-nasa-development-cost-are-heart-of-the-matter/ |title=Impossibly High NASA Development Costs Are Heart of the Matter |author=Henry Vanderbilt |publisher=moonandback.com |date=15 September 2011 |accessdate=26 January 2012}}
123. ^¹{{cite web|url=http://spacefrontier.org/2011/09/15/monster-rocket/|author=Ferris Valyn|title=Monster Rocket Will Eat America's Space Program|publisher=Space Frontier Foundation|date=15 September 2011|accessdate=16 September 2011|deadurl=yes|archiveurl=https://web.archive.org/web/20111006080619/http://spacefrontier.org/2011/09/15/monster-rocket/|archivedate=October 6, 2011|df=mdy-all}}
124. ^{{cite web |url=http://planetary.org/programs/projects/space_advocacy/Planetary_Society_Statement_20110712.pdf |title=Statement before the Committee on Science, Space, and Technology US House of Representatives Hearing: A Review of the NASA's Space Launch System |publisher=The Planetary Society |date=12 July 2011 |format=PDF |accessdate=26 January 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20120329041733/http://planetary.org/programs/projects/space_advocacy/Planetary_Society_Statement_20110712.pdf |archivedate=March 29, 2012 |df=mdy-all }}
125. ^{{cite web |title=Nothing New or Innovative, Including It's Astronomical Price Tag |first=Dana |last=Rohrabacher |url=http://rohrabacher.house.gov/News/DocumentSingle.aspx?DocumentID=260132 |date=14 September 2011 |accessdate=14 Sep 2011 |deadurl=yes |archiveurl=https://web.archive.org/web/20110924081721/http://rohrabacher.house.gov/News/DocumentSingle.aspx?DocumentID=260132 |archivedate=September 24, 2011 |df=mdy-all }}
126. ^{{cite web |url=http://www.parabolicarc.com/2011/08/24/rohrabacher-calls-for-emergency-ccdev-funding/ |title=Rohrabacher calls for "emergency" funding for CCDev |publisher=parabolicarc.com |date=24 August 2011 |accessdate=15 September 2011}}
127. ^{{cite web |url=http://www.thespacereview.com/article/1932/1 |title=A monster rocket, or just a monster? |publisher=The Space Review |date=15 September 2011 |author=Jeff Foust}}
128. ^{{cite web |url=http://www.thespacereview.com/article/1760/1 |title=Can NASA develop a heavy-lift rocket? |publisher=The Space Review |date=1 November 2011 |author=Jeff Foust}}
129. ^{{cite news |url=http://satellite.tmcnet.com/topics/satellite/articles/230642-did-nasa-hide-in-space-fuel-depots-get.htm |title=Did NASA Hide In-space Fuel Depots To Get a Heavy Lift Rocket? |work=Satellite Spotlight |first=Doug |last=Mohney |date=21 October 2011 |accessdate=10 November 2011}}
130. ^{{cite web |url=http://images.spaceref.com/news/2011/21.jul2011.vxs.pdf |title=Propellant Depot Requirements Study |work=HAT Technical Interchange Meeting |date=21 July 2011}}
131. ^{{cite news |url=http://www.spaceref.com/news/viewnews.html?id=1577 |title=Internal NASA Studies Show Cheaper and Faster Alternatives to the Space Launch System |work=SpaceRef.com |first=Keith |last=Cowing |date=12 October 2011 |accessdate=10 November 2011}}
132. ^{{cite web |url=http://images.spaceref.com/news/2011/F9Prop.Depot.pdf |title=Near Term Space Exploration with Commercial Launch Vehicles Plus Propellant Depot |publisher=Georgia Institute of Technology / National Institute of Aerospace |year=2011}}
133. ^{{cite web |url=http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf |title=Affordable Exploration Architecture |publisher=United Launch Alliance |year=2009 |format=PDF |deadurl=yes |archiveurl=https://web.archive.org/web/20121021121535/http://www.ulalaunch.com/site/docs/publications/AffordableExplorationArchitecture2009.pdf |archivedate=October 21, 2012 |df=mdy-all }}
134. ^{{cite web |url=http://www.thespacereview.com/article/1861/1 |title=Human spaceflight for less: the case for smaller launch vehicles, revisited |publisher=The Space Review |date=6 June 2011 |author=Grant Bonin}}
135. ^{{cite web|url=http://www.marssociety.org/home/press/tms-in-the-news/howwecanflytomarsinthisdecade%E2%80%93andonthecheap|title=How We Can Fly to Mars in This Decade—And on the Cheap|date=14 May 2011|publisher=Mars Society|author=Robert Zubrin|accessdate=|deadurl=yes|archiveurl=https://web.archive.org/web/20120319191604/http://www.marssociety.org/home/press/tms-in-the-news/howwecanflytomarsinthisdecade%E2%80%93andonthecheap|archivedate=March 19, 2012|df=mdy-all}}
136. ^{{cite web|url=http://www.huffingtonpost.com/rick-tumlinson/the-senate-launch-system-_b_963484.html|title=The Senate Launch System – Destiny, Decision, and Disaster|date=15 September 2011|work=Huffington Post|author=Rick Tumlinson}}
137. ^{{cite web |url=http://www.thespacereview.com/article/1955/1 |title=Propellant depots: the fiscally responsible and feasible alternative to SLS |publisher=The Space Review |date=24 October 2011 |author=Andrew Gasser}}
138. ^{{cite web |url=http://www.nasa.gov/pdf/396093main_HSF_Cmte_FinalReport.pdf |title=Seeking A Human Spaceflight Program Worthy of A Great Nation |last=Review of U.S. Human Space Flight Plans Committee |author2=Augustine, Austin |author3=Chyba, Kennel |author4=Bejmuk, Crawley |author5=Lyles, Chiao |author6=Greason, Ride |date= October 2009 |publisher=NASA |accessdate=15 April 2010}}
139. ^{{cite web|url=http://cosmiclog.msnbc.msn.com/_news/2011/12/07/9254628-is-the-case-for-mars-facing-a-crisis |title=Is the case for Mars facing a crisis? |publisher=MSNBC |date=7 December 2011 |author=Alan Boyle |deadurl=yes |archiveurl=https://web.archive.org/web/20120107155557/http://cosmiclog.msnbc.msn.com/_news/2011/12/07/9254628-is-the-case-for-mars-facing-a-crisis |archivedate=January 7, 2012}}
140. ^{{cite web |url=http://www.nss.org/articles/falconheavy.html |title=The SpaceX Falcon Heavy Booster: Why Is It Important? |publisher=National Space Society |accessdate=4 January 2012 |author=John K. Strickland, Jr.}}
141. ^{{cite web|url=http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/awst/2010/11/29/AW_11_29_2010_p28-271784.xml|archive-url=https://archive.is/20120727234353/http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/awst/2010/11/29/AW_11_29_2010_p28-271784.xml|dead-url=yes|archive-date=27 July 2012|title=NASA Studies Scaled-Up Falcon, Merlin|date=2 December 2010|publisher=Aviation Week}}
142. ^{{Cite web|url=https://www.nextbigfuture.com/2017/10/spacex-bfr-to-be-lower-cost-than-falcon-1-at-7-million-per-launch.html |title=Spacex BFR to be lower cost than Falcon 1 at $7 million per launch |website= nextbigfuture.com |language=en-US |access-date=2019-01-17}}
143. ^{{cite web |url=http://moonandback.com/2011/09/27/congressman-space-frontier-foundation-and-tea-party-in-space-call-for-nasa-sls-investigation/ |title=Congressman, Space Frontier Foundation, And Tea Party In Space Call For NASA SLS Investigation |publisher=moonandback.com |date=4 October 2011 |accessdate=20 October 2011}}
144. ^{{cite web |url=http://www.competitivespace.org/issues/the-senate-launch-system/ |title=The Senate Launch System |publisher=Competitive Space |date=4 October 2011 |accessdate=20 October 2011}}
145. ^{{cite web|url=http://www.houstonchronicle.com/news/nation-world/article/Sunday-conversation-NASA-veteran-Chris-Kraft-4778332.php?t=c0fa622d720edf9b03|title=NASA veteran Chris Kraft upfront with criticism |date=Aug 2013}}
146. ^{{cite web |url=http://spacenews.com/38912garver-nasa-should-cancel-sls-and-mars-2020-rover/ |title=Garver: NASA Should Cancel SLS and Mars 2020 Rover |work=Space News |date=Jan 2014}}
147. ^{{cite web |url=http://www.slate.com/blogs/bad_astronomy/2015/08/24/congress_and_nasa_commercial_crew_program_is_underfunded.html |title=Why NASA Still Can’t Put Humans in Space: Congress Is Starving It of Needed Funds|year=2015}}
148. ^{{cite web|url=http://www.thespacereview.com/article/1447/1|title=The Space Review: Doubts about depots|author=|date=Aug 2009|work=thespacereview.com}}
149. ^{{cite web|url=http://www.spacesafetymagazine.com/space-exploration/deep-space/nasa-strongly-in-orbit-fuel-depots/|title=NASA Considering In-Orbit Fuel Depots|author=|date=November 6, 2011|work=spacesafetymagazine.com}}
150. ^{{cite web|url=http://www.thespacereview.com/article/2726/1|title=The Space Review: Doing humans to Mars on—and within—a budget|date=April 2015|author=|work=thespacereview.com}}
151. ^¹²³⁴⁵⁶⁷⁸⁹¹⁰¹¹¹²¹³¹⁴¹⁵{{cite news |url=https://www.nasaspaceflight.com/2017/04/nasa-goals-missions-sls-eyes-multi-step-mars/ |title=NASA finally sets goals, missions for SLS – eyes multi-step plan to Mars |website=NASASpaceFlight.com |first=Chris |last=Gebhardt |date=April 6, 2017 |access-date=August 21, 2017}}
152. ^¹²³⁴⁵{{cite news |url=https://www.nasaspaceflight.com/2018/09/nasa-lunar-gateway-plans/ |title=NASA updates Lunar Gateway plans |first=Philip |last=Sloss |website=NASASpaceFlight.com |date=11 September 2018 |access-date=17 September 2018}}
153. ^¹²³⁴{{cite news |url=https://spaceflightnow.com/2017/11/20/nasa-expects-first-space-launch-system-flight-to-slip-into-2020/ |title=NASA expects first Space Launch System flight to slip into 2020 |last=Clark |first=Stephen |work=Spaceflight Now|date=20 November 2017 |access-date=24 May 2018}}
154. ^¹{{cite web |last1=Hambleton |first1=Kathryn |title=Exploration Mission-1 Map |url=https://www.nasa.gov/image-feature/exploration-mission-1-map |website=nasa.gov |publisher=NASA |accessdate=16 September 2018}}
155. ^¹{{cite web |url=http://www.nasa.gov/press/2014/august/nasa-completes-key-review-of-world-s-most-powerful-rocket-in-support-of-journey-to/#.U_5UAfl7Eeg |title=NASA Completes Key Review of World's Most Powerful Rocket in Support |website=NASA |accessdate=26 October 2015}}
156. ^{{cite web |url=http://www.nasaspaceflight.com/2012/02/acronyms-ascent-sls-managers-create-developmental-milestone-roadmap/ |title=Acronyms to Ascent – SLS managers create development milestone roadmap |publisher= |accessdate=26 October 2015}}
157. ^{{cite web |url=https://www.youtube.com/watch?v=oGKry-AmV-c |title=NASA’s Space Launch System to Boost Science with Secondary Payloads |date=April 2, 2015 |publisher=NASA's Marshall Center |via=YouTube}}
158. ^{{cite web |url=http://www.jpl.nasa.gov/cubesat/missions/neascout.php |title=Near Earth Asteroid Scout (NEAScout) |website=JPL {{!}} Cubesat}}
159. ^¹²³⁴⁵⁶{{cite web |url=https://www.nasaspaceflight.com/2017/09/sls-em-1-em-3-notional-mission-outline/ |title=SLS EM-1 & -2 launch dates realign; EM-3 gains notional mission outline |last=Gebhardt |first=Chris |work=NASASpaceFlight.com |date=22 September 2017 |access-date=23 September 2017}}
160. ^¹{{cite web |last1=Hambleton |first1=Kathryn |title=NASA’s First Flight With Crew Important Step on Long-term Return to the Moon, Missions to Mars |url=https://www.nasa.gov/feature/nasa-s-first-flight-with-crew-important-step-on-long-term-return-to-the-moon-missions-to |website=nasa.gov |publisher=NASA |accessdate=16 September 2018}}
161. ^{{cite web |url=https://www.nasa.gov/feature/nasa-s-first-flight-with-crew-will-mark-important-step-on-journey-to-mars |title=First Flight With Crew Will Mark Important Step on Journey to Mars |first=Gary |last=Daines |date=December 1, 2016 |website=Nasa.gov|accessdate=2 January 2018}}
162. ^{{cite news |url=http://www.spacepolicyonline.com/news/nasa-continues-journey-to-mars-planning |title=NASA Continues Journey to Mars Planning |work=Space Policy Online |first=Marcia |last=Smith |date=March 28, 2017 |access-date=June 7, 2018}}
163. ^¹{{cite web|url=http://spacenews.com/nasa-moving-ahead-with-plans-for-cislunar-human-outpost/|title=NASA moving ahead with plans for cislunar human outpost|last1=Foust|first1=Jeff|date=10 March 2017|website=SpaceNews|publisher=Pocket Ventures, LLC.|archiveurl=https://archive.is/20170311174916/http://spacenews.com/nasa-moving-ahead-with-plans-for-cislunar-human-outpost/|archivedate=11 March 2017|accessdate=11 March 2017}}
164. ^{{cite web |title=NASA evaluates EM-2 launch options for Lunar Orbital Platform - Gateway PPE |date=December 4, 2017 |first=Philip |last=Sloss |url=https://www.nasaspaceflight.com/2017/12/nasa-evaluates-em-2-launch-of-space-gateways-ppe/ |website=NASASpaceFlight.com |access-date=2017-12-08}}
165. ^{{cite web |url=https://thespacereporter.com/2016/01/additional-1-3-billion-nasa-fund-next-mars-rover-europa-mission/ |title=Additional $1.3 billion for NASA to fund next Mars rover, Europa mission - |author= |date= |work=thespacereporter.com |deadurl=yes |archiveurl=https://web.archive.org/web/20160118071957/https://thespacereporter.com/2016/01/additional-1-3-billion-nasa-fund-next-mars-rover-europa-mission/ |archivedate=January 18, 2016 |df=mdy-all}}
166. ^{{cite web |url=http://www.planetary.org/blogs/guest-blogs/van-kane/20160105-nasa-europa-lander.html |title=A Lander for NASA’s Europa Mission |author= |date= |work=planetary.org}}
167. ^{{cite news|url=http://spacenews.com/nasa-selects-boulder-option-for-asteroid-redirect-mission/|title=NASA Selects Boulder Option for Asteroid Redirect Mission|last=Foust|first=Jeff|date=March 25, 2015|work=Space News|accessdate=2015-03-27}}
168. ^{{cite news|url=http://www.space.com/20612-nasa-asteroid-capture-mission-explained.html|title=Inside NASA's Plan to Catch an Asteroid (Bruce Willis Not Required)|last=Wall|first=Mike|date=April 10, 2013|work=Space.com|accessdate=April 10, 2013|agency=TechMediaNetwork}}
169. ^{{cite web|url=https://www.nasa.gov/feature/nasa-seeks-information-for-gateway-cargo-delivery-services|title=NASA Seeks Information for Gateway Cargo Delivery Services|last1=Warner|first1=Cheryl|date=23 October 2018|website=nasa.gov|publisher=NASA|accessdate=27 October 2018}}