Alternator-only range challenge

[Pds314]

CONCEPT:

Your goal is to power an electric vehicle vehicle using only the power of engine alternators and take it as far as possible.

 

RULES:

1. You may not use any drills, fuel cells, RTGs, or solar panels. Engine Alternators using resources you brought with you should be the only electricity source.

2. No non-electric sources of propulsion or infinite energy drives.

3. Any batteries must start fully discharged.

4. No net thrust should be generated by any method except the alternator from engines except for Ion engines and electric props. You only get the alternator output for all other engines.

5. Decouplers ARE allowed, however, they shouldn't consistute a significant source of propulsion.

6. You may travel by air, land, sea, or if you can get there, space but not by clipping through the ground. Vehicles may be Kerballed or unkerballed.

 

SCORING:

Your score is the distance from the launch site multiplied by the fraction of your starting mass remaining. You may place a starting marker or use latitude and longitude to compute distance. Altitude may be included as well if it is a significant factor. If you manage to somehow escape Kerbin's SOI, then the distance of your Kerbol Ap or Pe from Kerbin's orbit is counted.

Edited May 10, 2023 by Pds314

[Ultimate Steve]

This is the aptly named Alternator 1.

Powered by 2 electric motors with two bladed ducted fan propellers, and the electricity is supplied by two heavily throttled Junos operating at 180 degrees to each other. It would have been less draggy to orient them prograde-retrograde but this would have likely lead to asymmetric thrust due to how jet engines behave. In case there was any asymmetric thrust being generated during this flight, it was applied in the direction that least affects its flight. The wings have a 5 degree angle of incidence. The optimal would probably be lower but I was in a hurry.

Junos were chosen because jets have the best EC/s to LF/s ratios. I believe the Goliath has a waaaay better ratio. The Juno is one of the worst jets. However they are also the smallest, and I didn't want to build a gigantic craft.

Forgot to take a picture but the batteries did start empty.

After takeoff, I fiddled around with the settings on the blade pitch, motor torque, altitude, overall pitch, and juno throttle, so the trip became more and more efficient as it progressed, also likely helped by the (slowly) lightening aircraft.

I did not expect this to get very far, and due to land masses, it takes a lot of micromanaging. If I flew it all the way to empty, it would take around 11 hours. This is all at 1x warp because propellers don't do physics warp.

I do not believe any physics altering mods are installed.

While I still have it running in the background, I do not have the patience to see it through and will likely kill it soon, but Here is a picture more or less exactly 60 degrees east of the KSC, for a range of about 628.32 kilometers, having used 16.5% of its fuel. It currently masses 6993kg and massed roughly 7653kg at launch going by LF being 5kg/l as I can't check VAB mass right now. That is a current fraction of 0.91376, giving a realized score of 574.13.

If I had the time to continue the mission, even assuming the lightening of the aircraft will not increase fuel efficiency, at its current pace the Alternator 1 can do just over one complete circumnavigation of Kerbin assuming the jumps over the mountain ranges don't hurt its range too much. Assuming it uses all of its fuel and the efficiency doesn't increase, that would be a mass fraction of 0.47485 and a range of 3770km, for a theoretical score of 1790.13.

I find it amusing that the propellers are producing a few times more thrust than the jets are while just running off of the jets alternators. Ducted fan blades are OP.

[camacju]

This is an interesting challenge. 

I was going to try to cheese it - the DLC turboshaft engine has a built-in alternator that scales with RPM and not with torque, and is also frictionless. Kickstart it and it provides electricity forever, like a less mass efficient RTG. My plan was to run one unit of liquid fuel through the turboshaft to charge a small battery, and then spin it with some DLC electric motors to generate electricity more. Time warp wouldn't be an issue as I could just start it from the battery again, and then I would do something interesting like a Jool surface return using ions and magic wings.

However, what I discovered as I was testing crafts was that for some reason, the alternator would scale with 1/(rpm limit). I assume this was to simulate the effect of a gearbox, even though it would be perfectly backdrive-able. Apparently, when rpm limit is set to zero, alternator output hits a divide by zero and evaluates to infinity, which basically means that I've discovered an infinite electricity glitch.

A clip of it is attached below. Note the change in electricity generation when I change the motor's RPM limit, and how I generate 64k electric charge in a single frame when RPM limit hits zero. Also, I'm spinning the turboshaft at 920 RPM by rotating both the base and the rotor with DLC electric motors, because I planned to do this originally to generate twice as much electricity per motor.

 

[Pds314]

On 5/17/2023 at 4:45 PM, camacju said:

This is an interesting challenge. 

I was going to try to cheese it - the DLC turboshaft engine has a built-in alternator that scales with RPM and not with torque, and is also frictionless. Kickstart it and it provides electricity forever, like a less mass efficient RTG. My plan was to run one unit of liquid fuel through the turboshaft to charge a small battery, and then spin it with some DLC electric motors to generate electricity more. Time warp wouldn't be an issue as I could just start it from the battery again, and then I would do something interesting like a Jool surface return using ions and magic wings.

However, what I discovered as I was testing crafts was that for some reason, the alternator would scale with 1/(rpm limit). I assume this was to simulate the effect of a gearbox, even though it would be perfectly backdrive-able. Apparently, when rpm limit is set to zero, alternator output hits a divide by zero and evaluates to infinity, which basically means that I've discovered an infinite electricity glitch.

A clip of it is attached below. Note the change in electricity generation when I change the motor's RPM limit, and how I generate 64k electric charge in a single frame when RPM limit hits zero. Also, I'm spinning the turboshaft at 920 RPM by rotating both the base and the rotor with DLC electric motors, because I planned to do this originally to generate twice as much electricity per motor.

 

I was afraid this thing would be a bit busted. Although I'm happy to use its bustedness for other purposes in the future. I really didn't expect it to be THAT busted though. I had assumed that the electricity generation would be scaled with torque output and absolute RPM. This thing is truly bonkers.

Edited May 22, 2023 by Pds314

[Alex Verb]

Hello Everyone,

Here is my attempt.

Equatorial arc = 314.3 degrees
Equatorial distance = 3291 km

Thank you!