The Elcano Challenge: Ground-Based Circumnavigation (Continued)

[The_Rocketeer]

1 hour ago, Chemp said:

I love the way this looks, especially the cockpit placement.

How do you deal with the asymmetric thrust? Did you angle the engines, or do you let the control surfaces handle the offset?

Thanks!

I'll try to answer as fully as I can and cover everything. Sorry for explaining in a roundabout way...

I built the craft with 1 pair of Goliaths on top of the floats, plus 3 Wheesleys on the trailing nodes of the 3 'hulls'. There's no angle on the engines, they're just attached straight on the nodes/edge surfaces without rotation adjustment. During my first distance run, I made a pilot error that damaged the craft and bust the intake and Wheelsey off the port float. To keep thrust balanced, I shut down the opposite Wheelsey and ran on just the Goliaths and the centre Wheelsey. For unknown reasons, the starboard float intake has also since detached - it was there one moment and the next time I looked it was gone the latest design revision has replaced the intakes and engines on the floats with nose-cones for better durability.

Running on 2 Goliaths and the centre Wheesley, initially I found the craft, while still planing, was about 30% slower. I perceive that the centre-of-thrust moved upwards when the lower engines shut down, so the boat was tending to pitch-down and drive into the water instead of skimming over it. However, after re-trimming the planes to give a little more lift forward and a little less aft, I found that it was still possible to reach the same 100m/s target speed. I could be wrong about this part, but my impression is that the 3 engine configuration is more efficient than the 5 engine configuration (but I have to allow that as the comparison was made on the same run and the craft mass was decreasing the whole time that could be a false impression). Nonetheless, assuming the change in mass is insignificant, and speed and throttle setting being the same (100m/s, 100% throttle), I think I must be using less fuel per distance with 2 fewer engines. The Goliaths also have higher ISP than the Wheesleys, so if a higher proportion of available fuel is ultimately consumed by Goliaths it should go further - i.e. more efficient.

Also relevant is the fact that in both configurations, as the fuel mass decreases it's necessary to continally re-trim the planes inline with mass reduction to reduce lift. While in theory more engines means higher cruising speed, maximum speed is limited by the point at which aerodynamic lift force exceeds mass, because at that point the craft stops hydroplaning and starts aeroplaning. It's possible that as the tanks get dry, it might become impossible to stop the craft flying without reducing speed, either by cutting throttle or by setting the planes to negative pitch. Mastering the hydrofoil is an ongoing education!

TL:DR, I think correcting the offset-thrust with more control surface pitch is more efficient than reducing it by adding engines lower down.

=======

In other news, after one or two further mishaps, and having learned a lot from this attempt, I've decided to demote this adventure to a shake-down cruise.

Hoping to return with a new and improved hydrofoil Elcano attempt in the coming days.

[Claw]

5 hours ago, The_Rocketeer said:

Hoping to return with a new and improved hydrofoil Elcano attempt in the coming days.

\o/  I definitely learned a bit about building boats for the Laythe trip (post buoyancy updates). My original Kerbin boat doesn't hardly float anymore.

[SpaceK531]

Before the original Elcano challenge was posted in 2015, there was the no-rules circumnavigation challenge. Unlike Elcano, where the spirit is the most important part, the no-rules circumnavigation challenge was all about results.

I decided that instead of circumnavigation using depressed trajectories and rockets, I decided I was going to do a water circumnavigation. I got about halfway around Kerbin before deciding to do other things, then KSP changed parts and all hope of completing that circumnavigation was lost. This circumnavigation attempt can be read about at its original post.

Even though I stopped, and I can no longer complete the original circumnavigation that I set out to do, I still want to complete a water circumnavigation.

Through last night and this morning, I worked hard on designing a ship that could work as well as my original ship even with the new water physics. Here are snapshots of that journey:

For some reason the description of the first image isn't appearing. For the first design, I decided I wanted all the bells and whistles: mining, lights, convertotrons, generators.

Edited July 11, 2016 by SpaceK531
included first image text.

[The_Rocketeer]

41 minutes ago, SpaceK531 said:

Through last night and this morning, I worked hard on designing a ship that could work as well as my original ship even with the new water physics.

[From caption] Still wildly guessing to find something that works.

I completely sympathise. Despite 4 design iterations, my best hydrofoil is still more of less the first (I really need a name for it... working title was 'Soviet 2', but that seems a bit political - suggestions?). I also tried lots of other hydrofoils before this one with varying degrees of failure. Seems this time I just struck lucky with a platform that worked.

While cutting down from 3 to 1 Wheesley on my ship hasn't affected performance much, dropping the 3rd Wheesley crosses some sort of threshold - the boat will drive around fine, but it just can't get up on the foils without the extra 110kN thrust coming from it. The science of boating in KSP is apparently very nuanced!
 

Edited July 11, 2016 by The_Rocketeer

[The_Rocketeer]

Update: tweaking today yielded a lot of lessons, but I'm facing diminishing returns - I can double the fuel, but I don't get double the range from it because fully loaded the craft now cruises at only about 1/3 speed, and even when it does get up on the planes properly it's still about 25% slower due to extra drag. Making the craft longer instead of broader fixes the leading-edge drag, but makes it harder to keep the pitch level, plus you get flex problems between the joints, and more bits in contact with the water surface still means more drag.

I'm staggered that my boat seems to have been so good first time out. I was really hoping for a non-stop run around the planet, but I have a feeling the rocket equation is kicking my butt here.

[Chemp]

15 hours ago, The_Rocketeer said:

I'll try to answer as fully as I can and cover everything.

That was a great insight in the design process. I've had similar observations when I built my hydrofoil (link in signature) and had the same problem that when I got too low on fuel, the craft had a tendency to become airborne, flip and become reacquainted with the water in a most unfriendly fashion. Right now, I'm working on a boat for the Laythe circumnavigation, so my new approach is to limit lifting surfaces to the minimum. That has severely impacted speed and 100m/s is currently my limit as well but I'm still trying new approaches.

[rocketengineer1982]

On 7/2/2016 at 3:06 PM, The Optimist said:

You know what's really boring? A Kerbin equatorial circumnavigation

Not really.  Especially if you have an anti-lock braking failure (in other words, panicking and jamming "B") while going down the side of a mountain and you lose 1/4 of your wheels and half of a pontoon.  Gonna need a replacement vehicle before the next water crossing.

There are a couple nasty mountain ranges on the path that have to be dealt with or detoured around.  So far, I've kept within a few minutes of the equator.

If you use a 32-bit version of KSP on low terrain resolusion, the terrain joints can be a bit of a problem, too.

 

[SpaceK531]

What a wild first leg I had! The journey can be divided into three parts: High-Speed Watercraft long pontoon, Inasta and Inasta II, and Inasta III.

 

The first leg was High-Speed watercraft long pontoon, the test boat.

 

High-Speed Watercraft long pontoon made a good first leg but was not fit for a full circumnavigation because kerbals cannot re-enter the craft if they leave, which makes flag-planting impossible. Also, the proper opening ceremony had not been made. I officially start the circumnavigation with Inasta.

Alright, so, actually Inasta II was the real start of the journey because it's the only one I haven't lost progress on.

Finally made it to the end of leg one.

[damerell]

I don't want to be Captain Obvious about the re-entering the cockpit thing, but extensible ladder?

[SpaceK531]

7 hours ago, damerell said:

I don't want to be Captain Obvious about the re-entering the cockpit thing, but extensible ladder?

I didn't see an extendable ladder on High-Speed Watercraft long pontoon. The purpose of Inasta and the following ships was to have ladders, as well as be able to pick up the crew of High-Speed Watercraft long pontoon. I talk about this in some of the captions.

Edited July 12, 2016 by SpaceK531

[spongey45]

Could I use some kind of uh, a plane-shaped boat?

[Claw]

25 minutes ago, spongey45 said:

Could I use some kind of uh, a plane-shaped boat?

Yes, so long as the plane-shaped boat doesn't turn into a boat-shaped plane.   (and by that I mean it has to drive/boat for the circumnavigation)

[spongey45]

4 minutes ago, Claw said:

Yes, so long as the plane-shaped boat doesn't turn into a boat-shaped plane.   (and by that I mean it has to drive/boat for the circumnavigation)

I posted the design here,

 

Edited July 13, 2016 by spongey45

[Claw]

@spongey45 Yes, I'm okay with that so long as it stays in contact with the water/ground. I've found that sometimes when it has that much wing area, and gets light, it will want to get airborne pretty easily (even on the water).

[Claw]

I've finished driving Eve!  

The mission report for "Eve: Day 1 Activities" is up. I will post the remainder tomorrow (I'm sleepy). Here's the album for Day 1:

 

[The_Rocketeer]

Bravo @Claw - you're a real globetrotter

[Claw]

Thanks @The_Rocketeer It was quite a journey.

[SpaceK531]

Maybe make that solar system trotter!

Edited July 13, 2016 by SpaceK531

[Thalamask]

Congratulations, @Claw on an amazing achievement!

[Maverick_aus]

Finally, after (arguably too much) preparation, the Elcano <Actual Expedition> has begun in earnest. It was a day of births and deaths. Seriously. Couldn't believe it. Check it out below.

@Claw Awesome job. EVE!

@SpaceK531 Nice adventuring. 

Edited July 13, 2016 by Maverick_aus

[damerell]

6 hours ago, Claw said:

The mission report for "Eve: Day 1 Activities" is up.

A suicide mission, you monster. :-)

[Claw]

Thanks everyone.  Part two to come later today. I wish I had been paying a little more attention to the date. It was just a bit over a year ago when I started my first trip. (Though I'm not sure I had the time to finish it any faster...)

[SpaceK531]

I will be posting updates on a separate thread to avoid cluttering this thread up too much.

.The thread can be found here

[Thalamask]

I have just completed my Eve circumnavigation with a stock craft. Linky, as always, in sig.

[Claw]

8 hours ago, Thalamask said:

I have just completed my Eve circumnavigation with a stock craft.

Nice job! I'll have to take a look later, but congrats on finishing another.  How many left, and are you planning on going all the way?

I need to get that front page up to date!