yep. The Soyuz was supposed to run on Syntin but then they reverted back because the added energy density and payload capacity (something like 30%) was not wor

yep. The Soyuz was supposed to run on Syntin but then they reverted back because the added energy density and payload capacity (something like 30%) was not worth the manufacturing cost. https://en.wikipedia.org/wiki/Syntin https://en.wikipedia.org/wiki/Syntin Edit: Soyuz U2 (Syntin version) launched 72!! rockets. Then they reverted back.