School Project: (Very) long range communication, where to start?

So, I’m not entirely sure if I’m at the right place with the problem I’m trying to solve, but:
I’m relatively new to radio communication and couldn’t find the information I intended to find after long research- and my problem is not really about sound transmission, it’s about data transmission and the hardware required for a relatively special case.
So I’m searching for a way to transmit data over a range of approx. 150km (~93miles) - No obstacles - Ground to stratosphere (100% atmosphere down to 1%) - as light as possible, as energy efficient as possible, with as much data transmission as possible (would be happy with a couple dozen bits/s in this case) - But I honestly don’t have any idea what I’m looking for and how to be at least theoretically sure that the transmission works - if it’s possible at all - all I found we’re articles that met the requirements not explaining how it’s done or information explaining how it’s done not meeting the requirements.

So- does anyone have an idea in which direction I could go, or what I need to calculate the theoretical data transmission rate/ range (with transmitter-specific parameters) since I can’t even find any formulas for whatever reason and all values I found for certain frequencies are inconsistent.

I would be very happy about any hints regarding the situation and I wan’t to apologize for my maybe not perfect English - The purpose btw: A slightly advanced school project - need to communicate with a UAV in stratosphere - long story - a lot of problems since the UAV doesn’t exist - y e t. I’m on it.

I’m not sure about what exactly you are doing, but the key is path loss. 150Km isn’t an issue if it’s line of site. The Raspberry Pi folk are doing data . If the direction is more ground based, then there might simply be no path at all. Do you have more info we can have?

Maybe Laser comm units? I have used in the past to bridge 2 buildings for our computer network systems? just my 2 cents.

I would be looking at LoRa solutions. 800/900 MHz (depending on ITU region) may do it for you. The only thing I’ve reliably used at that distance though is VHF/UHF narrowband IP solutions which aren’t exactly light but allowed for fairly high speed data rates (64+ kbps).

Some of the school experiments from the space station have shown kids how far tiny amounts of power can actually go. They were always kits and pre-arranged things. I wonder if any of these experiments NASA did were with digital rather than voice?

Look up the following:

Bit Error Rate by modulation scheme, different modulation schemes, Shannon’s Theorem, turbo codes, trellis codes, TKD noise, link budget, antenna gain, BLOS (beyond line of sight), “skip”, tropospheric ducting, NVIS, long wave propagation, etc

Although you say that there is no information, there is plenty and most of it comes with a good EE degree, although Ham radio licensing provides some knowledge as a result of the testing process.