SLS takes on new buckling standards, drops Super Light alloy

February 18, 2013 by Martin Payne

With a recent decision to switch the Space Launch System (SLS) core from aluminum-lithium to non-lithium alloys, NASA has come full circle on a journey that started nearly twenty years ago with the development of Shuttle’s Super Light Weight External Tank (SLWT). The switch is not just about reducing costs, but it will also prove to be more optimal for the stresses that SLS will endure.

SLS Core Material:

In 1988 – after a challenging four year development programme that kick-started NASA’s knowledge about Al-Li alloys – STS-91 flew the first SLWT.

This tank had been re-engineered to use Al-2195 and Al-2090 extensively, which were stronger and lighter than the Al alloys on LWT (Al-2219, etc).

Together with the first use of an orthogrid structure – on the LH2 tank’s barrel – this lightened the structure and improved payload, especially to the high-inclination orbit of the International Space Station (ISS).

However, those new alloys were also more brittle and difficult to weld, and experience showed a maintenance overhead. All of the dome and ogive sections were reverted back to aluminum over three subsequent revisions – first flown on STS -116, -119, and -130 respectively.

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