Editing Space Shuttle external tank (section)

===Super Lightweight Tank===
The Super Lightweight Tank (SLWT) was first flown in 1998 on [[STS-91]] and was used for all subsequent missions with two exceptions ([[STS-99]] and [[STS-107]]).<ref name=LMFS07>*[http://www.lockheedmartin.com/data/assets/12742.pdf "FACT SHEET SPACE SHUTTLE EXTERNAL TANK"]{{Dead link|date=February 2023 |bot=InternetArchiveBot |fix-attempted=yes }} April 2007 [[Lockheed Martin]]{{dead link|date=November 2017 |bot=InternetArchiveBot |fix-attempted=yes }}
*http://www.nasa-klass.com/Curriculum/Get_Training%201/ET/RDG_ET-Additional/ETFactSheet.pdf
*https://www.nasa.gov/returntoflight/system/system_ET.html</ref> The SLWT had basically the same design as the LWT except that it used an [[aluminium-lithium alloy]] ([[2195 aluminium alloy|Al 2195]]) for a large part of the tank structure. This alloy provided a significant reduction in tank weight (about {{convert|3,175|kg|order=flip|disp=or|abbr=out}}) over the LWT. Manufacture also included [[Friction stir welding#Aerospace|friction stir welding]] technology. Although all ETs produced after the introduction of the SLWT were of this configuration, one LWT remained in inventory to be used if requested until the end of the shuttle era. The SLWT provided 50% of the performance increase required for the shuttle to reach the [[International Space Station]].<ref name="by the numbers">{{cite web|url=http://www.lockheedmartin.com/ssc/michoud/ExternalTank/ByNumbers.html|title=External Fuel Tank by the Numbers|publisher=Lockheed Martin|archive-url = https://web.archive.org/web/20080103111431/http://www.lockheedmartin.com/ssc/michoud/ExternalTank/ByNumbers.html|archive-date=January 3, 2008 }}</ref> The reduction in weight allowed the Orbiter to carry more payload to the [[International Space Station#Orbit|highly inclined orbit of the ISS]].

[[Image:Pegasus barge being moved by Freedom Star and towboat American 2.jpg|right|thumb|300px|The Pegasus barge<ref>{{Cite web |last=Harbaugh |first=Jennifer |date=February 4, 2020 |title=NASA's Barge Pegasus – Transportation for the Space Launch System Core Stage |url=http://www.nasa.gov/exploration/systems/sls/fs/pegasus-barge.html |access-date=October 25, 2022 |website=NASA}}</ref> carrying ET-119 (which will be used on [[STS-121]]) is towed to Port Canaveral.]]<!-- There is no other mention of "the Pegasus barge" in this article; yet a [[WP:REDIRECT]] points to it. Needs to be mentioned/cited in the article prose. -->