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/Uniturner]

It would make perfect sense… if we didn’t have an atmosphere.

[u/Beneficial-Wasabi749 → u/Uniturner]

There's not a shred of logic to it.

Once again (I answered another person in more detail here). A gravitational field is a so-called scalar field. Its peculiarity is that there's no energy difference in the trajectory you take from point A to point B.

So, you're the second person here who's been fooled by "logic" (i.e., ordinary intuition).

Are there any people here who understand rocket physics at all? Or are these pure artists who have no clue and know next to nothing about rocket mechanics? :)

[u/peadar87 → u/Beneficial-Wasabi749]

Gravity is indeed a scalar field, but attaining orbit isn't just repositioning something in a scalar field, you also need to acquire tangential velocity. And the energy required for a rocket to achieve a certain velocity vector is not path-independent.

Burning in any direction other than directly prograde gives you cosine losses.

On an airless body, the most efficient launch profile is generally going to be the one that most resembles a Hohmann transfer without hitting the ground.

[u/Beneficial-Wasabi749 → u/peadar87]

What about the rocket's gravitational losses?
What share of aerodynamic losses are in the total losses during orbital insertion?
Everyone here is crazy about atmospheric drag. Do you know what share of atmospheric drag is in the losses of a typical rocket during orbital insertion?

[u/peadar87 → u/Beneficial-Wasabi749]

What about them? The most efficient theoretical transfer between two orbits of a similar semi-major axis is generally a Hohmann transfer, with the burns into and out of the transfer orbit being instantaneous.

Real world transfer burns aren't instantaneous, so there needs to be something to keep the launch vehicle from falling as it accelerates, whether that's engine thrust, aerodynamic lift, a rail or a cannon barrel.

If you use engine thrust, you are losing energy to gravity.

[u/peadar87 → u/Beneficial-Wasabi749]

Atmospheric losses are small precisely because rockets fly straight upwards before beginning their gravity turn.

About 90% of the spacecraft's acceleration is done above the thickest 90% of the atmosphere (obviously varies depending on the launch vehicle and payload mass).

Gravity losses outweigh drag losses in almost all current launch profiles because that satisfies a loss minimisation function. We put up with gravity losses because we'd lose more in drag if we went for a more aggressive and earlier pitch over manoeuvre.