[Spaceships] getting into orbit without superscience?

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Originally Posted by Stomoxys

The ramjet mode of the SABRE engine is air breathing, burning fuel using oxygen from the surrounding air, so it is useless in an atmosphere with no oxygen.

Titan would be great for an electric propeller plane and it could work in the upper atmosphere of Venus too. XKCD Interplanetary Cessna

Titan's atmosphere is over 5% methane, so you might be able to build a methane-breathing engine with tanks of oxygen as fuel. Or could you? (Earth's atmosphere is about 20% oxygen.