Helicopter Engine is Greedy on Fuel

[uglyduckling81]

I was playing around in my career game with helicopter builds for the first time.

Whilst I was finally getting a craft to not crash 1 second after take-off, both engines cut out and I crashed in a firey wreck.

One fuel tank survived and was completely empty. It was the larger fuel only tanks which has 400 fuel.

So I check the fuel usage rates of the engines (R7000) and it uses 1.6 per second. So I compare that to the Wheesley which is on 0.23. What the hell?

I check the R121 Turboshaft and it's 0.4?

Why are the propeller and rotary wing engines so fuel hungry?

They are all gas turbines. I'd argue the Wheesley is more powerful than either of these engines. 

It means that I need a large tank for each R7000 for every 5mins (roughly) of flying. The Wheesley is what 6 or 7x more efficient? That makes no sense at all. The Wheesley states it has 10x the air intake of the R7000 which suggests it's fuel burn should be much higher.

The R7000 certainly isn't overly powerful as I need to run 2 of them at full power and speed to have any chance of getting my basic craft off the ground without counter rotating, which is nothing more than the 2 engines, the 2 fuel tanks, a seat, and some girders connecting it all.

Just for context I used to be an Avionics Technician working on Gas Turbine Rotary Wing Aircraft. So I have experience and knowledge in the real world on this topic.

What gives here? Is it just bad balancing? Or am I missing something?

[uglyduckling81]

Also the control system for Helicopters is just horrible. I think I need to progress further to unlock more advanced control groups. Hopefully the do a lot better job in KSP2 with this stuff.

[king of nowhere]

no idea, but i always used electric rotors. which consume a pittance and are basically endless with just a few rtgs

[evileye.x]

Hint: you don't need all the torque those engine provide to spin the blades or propellers. And if you will limit max torque, you'll greatly reduce fuel consumption 

[Rpatto92]

On 3/24/2023 at 12:54 AM, uglyduckling81 said:

Also the control system for Helicopters is just horrible. I think I need to progress further to unlock more advanced control groups. Hopefully the do a lot better job in KSP2 with this stuff.

It does seem like the Squad never did get around to adding more advanced parts for helicopters and as a result they were only ever really set-up to build basic helicopter designs.

I've spent a good while now figuring out how to use the parts we do have, to build helicopters that have flight characteristics similar to real helicopters (without over-use of reaction wheels) So, I've wrote a guide which covers everything about single-rotors and how to use robotics to properly account for asymmetry and produce a controllable helicopter. 

here's a link: https://forum.kerbalspaceprogram.com/topic/218964-helicopter-build-guide/

hope this helps

[KerikBalm]

On 3/25/2023 at 5:42 PM, evileye.x said:

Hint: you don't need all the torque those engine provide to spin the blades or propellers. And if you will limit max torque, you'll greatly reduce fuel consumption 

^this^

As far as control, I haven't really made any helos that I would describe as "nimble"

Quad copters are technically helicopters, you can make an ok control system with the KAL controller modifying rpms of the 4 rotors. I've made workable quad tiltrotor cargo aircraft that are controllable enough to land on top of the VAB, hangar roofs of the island airfield, etc. They are ponderous and require patient and gentle maneuvering in hover mode

Other than quad copters, I do contrarotating rotors, Kamov helo style. With enough reaction wheels, they can be fairly nimble

Another thing is the speed we expect from the helos. IRL, most helos fly slower than 200mph/320 kph, or less than 90 m/s.

Really slow in ksp when you get used to jetting around at >mach 4

Helos don't do well at high speed, and retreating blade stall should also manifest in ksp