> Its intended mission was to conduct lightning sea-borne attacks with the six anti-ship missiles it carried in launch tubes placed at the top of its hull.

Being a hazard to shipping appears to be the purpose of it.

I assume the parent means "to crash on it", not to sink it with a missile.

I will also say that at 5m from surface, good luck "seeing" it with on a radar. Also, at night and/or with mist.. you don't even see it coming.

Boats use radar to see other boats just fine. As the dramatically faster object it’s job is to avoid other ships not the other way around. As such it can just use forward looking radar and never hit anything unintentionally.

I will go ahead and assume that they see the Transponder signal and not the actual boats.

If by boats you mean warships, then yes, they may cause a blip in a proper radar.

No, the current generation of small boat radar are surprisingly capable in both harbors and the open ocean. Decent systems can reliably see a 20’ boat over a mile away in reasonably calm water. Transponders are frequently turned off in harbors for various reasons and are simply not that reliable even in the open ocean.

That said, at longer distances or rough seas things significantly degrade unless you’re talking about a big boat.

Every time these things are mentioned, I always wonder about that. Now that someone is building a modern equivalent (https://www.wigetworks.com), I wonder what they are doing about avoiding collisions.

Normal aircraft typically spend long periods in autopilot, whereas these things would presumably require a constantly vigilant pilot. And not just to avoid big ships, there are plenty of things floating in the ocean that could destroy one of these things: small boats, buoys, debris. The mast of a small sailing dinghy would be enough to cause a catastrophic crash.

I like the idea of this kind of craft, but I can't see it working at scale.

On the KM, the rear engines are the ones used in flight, and they're mounted well above the ground. The front engines are more of a booster to get it airborne, but they are indeed incredibly vulnerable.

You might be able to get it airborne without as much boost if you had the help of an intermediate phase of acceleration as a hydrofoil. The Orylonok uses a ski in this vein.

Smaller "Class B" Ekranoplans (like the Orlyonok [1]) could also fly like an airplane, I wonder if "hopping over" ships would be an option also for the bigger ones if avoiding traffic is a design goal (I guess since the Lun was a cold-war weapon system, avoiding civilian traffic wasn't all that important).

[1] https://en.wikipedia.org/wiki/A-90_Orlyonok

What was the deal with the Soviet obsession over contra-rotating coaxial propellers? Was there just one senior designer in the USSR with this obsession and a lot of influence?

I guess in this case the reason is that the Orlyonok simply used the engine of the Tu-95 bomber, this was the most powerful turboprop engine at the time (probably still is).

As for the Kamov helicopters, no idea, but apparently coaxial rotors are more efficient (e.g. better climb rate) than the traditional helicopter design. The "next generation" Sikorsky–Boeing SB-1 also uses coaxial rotors:

https://en.wikipedia.org/wiki/Sikorsky%E2%80%93Boeing_SB-1_D...

> I wonder if "hopping over" ships would be an option

Yes, at the cost of forward speed. It would be similar to a parabolic climb in an aircraft.

It wouldn't be that hard to put a scanning radar at the front of the thing and look 10 miles ahead so you have time to steer around others.

At about 10m height the horizon is only ~11km away - fine for a ship but if you are going 550km/h in something that doesn't look wildly manoeuvrable it might be quite exciting.

Still gives you a full minute to steer around something. But probably requires some automated system to decide on "collision or not" because that would be hard to do on time manually at such a distance.

If you start steering 30 seconds after detecting an object you would still be 5+ km away, so assuming a ship is at most 200m long you would only need a 3 degree course change to miss it by more than a ships length. Maybe make it 5 degrees to miss it by 400+ meters.