https://kids.guinnessworldrecords.com en

Lightest stock Single Stage to Orbit (SSTO) spacecraft built in Kerbal Space Program

Lightest stock Single Stage to Orbit (SSTO) spacecraft built in Kerbal Space Program
Who
"Foxster"
What
0.674 tonne(s)/metric ton(s)
Where
Not Applicable
When
15 January 2015

An SSTO is a spacecraft that can enter into orbit without losing parts on the way – unlike a normal rocket, which ditches used parts in stages. The lightest SSTO vehicle built in the beta release of Kerbal Space Program using only stock parts weighed 0.674 tonnes and was built by forum.kerbalspaceprogram.com user "Foxster", as verified by fellow KSP player "CalMacDa" on 15 January 2015.

Lighter vehicles could potentially have been built in later versions of Kerbal Space Program, with tweaked mechanics and new features liable to affect the metric in such challenges.