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Comment by mike_d | Hacker News Reader

We already have the technology for cheap orbital launches. SpaceRyde was developing a balloon that would take payloads to the edge of space then use a small rocket to get it the last little bit and do orbit positioning.

Unfortunately they got shut down by NIMBYs. https://spacenews.com/noise-complaints-help-bring-down-launc...

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This makes no sense. Getting up in altitude is the cheapest part of getting in orbit: the goal of the rocket is to bring you to orbital speed, which is what's hard. So the small rocket would still need to be almost as big (a bit smaller due to lower air friction at high altitude and the higher potential energy at launch, but only marginally so)

> Getting up in altitude is the cheapest part of getting in orbit

Think about it this way: The 30th second of a rocket flight consumes less fuel than the first second because you are carrying 30 seconds less of fuel.

https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

Getting into orbit is more about horizontal speed than altitude.

Rocket engines are much more efficient at lower atmospheric pressure.

The bigger the nozzle the faster the exhaust gas. Efficiency is proportional to the square of the speed of the exhaust gas.

The bigger the nozzle the lower the pressure of the exhaust gas. If the nozzle is too big then the atmospheric gas goes into the nozzle. That’s the limit on nozzle size for sea level launches.

Starting high is better because you can have a MUCH more efficient engine.

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