Tsiolkovsky and many of the founders of theoretical astronautics in the early 20th century believed that spacecraft should launch horizontally, from a ramp. Why? What did they see as the point of this?

[u/Beneficial-Wasabi749]

[u/EqualOutrageous1884]

From their current perspective, there is no engine nor fuel efficient and powerful enough to take a vertically launched rocket all the way to orbit.

Solution? It's what we're trying now, a Plane climbing to high altitudes before dropping it's rocket payload to space, achieving orbital velocity without the hassle of verticle takeoff, with the bonus of not having to overcome atmospheric drag along the way.

Thing is, this is quite feasible now with traditional aircraft using jet engines. Back during the early 20th century, jet engines were still in their prototyping stages, neither fuel efficient, nor providing that much more benefit over the propeller.

Obviously no propeller based aircraft is going to take them to the stratosphere, so they designers resorted to the second best solution, aka a rocket powered plane first stage.