Aerial Earth circumnavigation

[Entropian]

Aerial Earth Circumnavigation Challenge

Objective: Circumnavigate Earth (not Kerbin!) by air.

DISCLAMER: I'm not completely sure this can be accomplished.

Rules:

1)  The only method of propulsion allowed is airbreathing engines.  No rockets, kraken drives, or other shenanigans.

2)  Only 2 points of ground contact are allowed: takeoff and landing.  This is to prevent ISRU.

3)  No drop tanks or other staging.  The craft must be single stage.

4)  Stock parts only is preferred, but you can use mod parts as long as they aren't OP.

Even if you can't make it all the way around, share how close you managed to get!

Happy flying!

[Clamp-o-Tron]

I might take a go at it, but setting up RSS takes a while. To clarify, are solar-powered props allowed?

[Pds314]

Hmm... so at mach 4 in a hypersonic plane, the biggest issue will be fuel burn, because it only takes a few hours if you have the fuel. At mach <1 in an efficient cruising aircraft, then I think the fact that it would take you like a day and a half to complete would be the bigger problem, seeing as you should be able to maintain an L/D of about 20 or something and therefore 12000 S ISP will last you a long time.

[Entropian]

14 hours ago, Clamp-o-Tron said:

To clarify, are solar-powered props allowed?

No.  Only airbreathers.

2 hours ago, Pds314 said:

Hmm... so at mach 4 in a hypersonic plane, the biggest issue will be fuel burn, because it only takes a few hours if you have the fuel. At mach <1 in an efficient cruising aircraft, then I think the fact that it would take you like a day and a half to complete would be the bigger problem, seeing as you should be able to maintain an L/D of about 20 or something and therefore 12000 S ISP will last you a long time.

Yeah, I've come to the same conclusion.  I still think it might be doable with a large RAPIER-powered craft.

14 hours ago, Clamp-o-Tron said:

I might take a go at it, but setting up RSS takes a while.

Not really, just install

and RSS: https://github.com/KSP-RO/RealSolarSystem/releases

All of these work on 1.9.1.

[TheFlyingKerman]

@zolotiyeruki did 14 circumnavigations on Kerbin. This challenge should be doable.

 

[zolotiyeruki]

For those who wish to participate, I highly recommend these two mods:  First, for those interminable flights, an autopilot:

And second, for fine-tuning the AoA on your wings to maximize L/D:

(I'm not trying to toot my own horn here--both of these mods were authored by others.  But they're so useful, I became the maintainer of one, and uploaded a 1.10-recompile for the other)

[Entropian]

Nice.  I was just trying to adjust the AoA manually with no success.

[dawg]

I have done this with a small solar electric plane that could effectively orbit Kerbin within the atmosphere. It took off from the runway, turned around, then reached precisely SRV speed at a given altitude before I set MJ to hold altitude, velocity, and heading. I landed it after two orbits (roughly 12 hours) on the KSC runway because I missed my first landing window.

[vyznev]

43 minutes ago, dawg said:

I have done this with a small solar electric plane that could effectively orbit Kerbin within the atmosphere. It took off from the runway, turned around, then reached precisely SRV speed at a given altitude before I set MJ to hold altitude, velocity, and heading. I landed it after two orbits (roughly 12 hours) on the KSC runway because I missed my first landing window.

That'll be a lot harder to pull off on Earth than on Kerbin, though. If I didn't mess up the math, on Kerbin you need to fly westward along the equator at 174.5 m/s to track the sun; on Earth, you'd need to fly at 463.8 m/s, or about Mach 1.35, to pull off the same trick.

[dawg]

26 minutes ago, vyznev said:

That'll be a lot harder to pull off on Earth than on Kerbin, though. If I didn't mess up the math, on Kerbin you need to fly westward along the equator at 174.5 m/s to track the sun; on Earth, you'd need to fly at 463.8 m/s, or about Mach 1.35, to pull off the same trick.

I'm not sure any of my electric planes have ever done anything near that speed; on Kerbin they peak out somewhere around 350m/s if I recall correctly. Assuming that velocity is possible and maintained, you could arrive 31.9 hours later, with about 4.1 hours left before sunset. In theory, mind you.

[Entropian]

The problem is that only airbreathing engines are allowed.  This is to prevent simple BG turboprop designs from easily completing the challenge.  I've gotten about 3/4 of the way around using a RAPIER-powered plane, but with some more patience, I'm sure this challenge can be completed.

[Kernel Kraken]

So, which earth? Are you talking mods? And mods required should be listed in the OP. 

EDIT: Nevermind, scrolled down.

Edited September 29, 2020 by Kernel Kraken

[moar ssto]

On 9/25/2020 at 6:13 AM, Entropian said:

The problem is that only airbreathing engines are allowed.  This is to prevent simple BG turboprop designs from easily completing the challenge.  I've gotten about 3/4 of the way around using a RAPIER-powered plane, but with some more patience, I'm sure this challenge can be completed.

I guess the solution will be supercruise with a rapier+ magic wing vehicle, the super high l/d ratio at rapier top speed means you will need only very small amount of fuel to maintain leveled flight. I speculate that most of the flight can even be done unpowered.

Edited October 4, 2020 by moar ssto

[Entropian]

3 hours ago, moar ssto said:

magic wing

Magic wing?  Sounds cool.  What is it?

[Lt_Duckweed]

34 minutes ago, Entropian said:

Magic wing?  Sounds cool.  What is it?

Essentially, there are a number of different parts in the game that can under the right circumstances produce lift to drag ratios MUCH higher than what is possible with standard wings.  The very simplest is the small retractable landing gear.  Simply roll it 90 degrees so it is sideways, then angle the front upwards about 30 degrees.  This particular one can give a lift to drag ratio about 3x higher than what can be done stock (stock max supersonic/hypersonic lift drag is in the range from 4.3 to 5, depending on mach number, with the landing gear trick it is nearly 15.

They range anywhere from the 15 lift drag of landing gear, all the way up into the multiple 100's depending on the part.

Edited October 4, 2020 by Lt_Duckweed

[Entropian]

15 minutes ago, Lt_Duckweed said:

They range anywhere from the 15 lift drag of landing gear, all the way up into the multiple 100's depending on the part.

I just tried it out.  This is some insane L/D.  What are the other parts?

[moar ssto]

For gear planes, I speculate and ideal vehicle will be a craft with gear wings and also conventional wings placed inside a utility bay. You takeoff with conventional wings mostly(bay open) then once reaching suffficent speed, you shut down the cargo bay, so only the magic wings are producing l and d. You also don't want too much magic wing per mass( but a lot of magic wing per body drag, so you 'll need a heavily clipped vehicle), so you can get very close to rapier top speed at sea level. The fuel consumption rate will be abou the same as fying high, but because you have a high speed of sound down here, your speed is higher at that limiting mach number, so your fuel milage will be higher than flying high. Since RSS rescaled the heating constants, flying at this speed, about 2000m/s at sea level, won't cause any overheating issues, so no exta dry mass is needed for heat protectio as on kerbin. 

[Doctor Professor]

accidentally did the challenge around kerbin like an idiot

Edited February 7, 2021 by Doctor Sex
realized it said earth not kerbin

[Dr Stowaters]

On 9/25/2020 at 12:13 AM, Entropian said:

The problem is that only airbreathing engines are allowed.  This is to prevent simple BG turboprop designs from easily completing the challenge.  I've gotten about 3/4 of the way around using a RAPIER-powered plane, but with some more patience, I'm sure this challenge can be completed.

3/4!? How long did this take, game and real time?

[camacju]

This was a fun challenge! It's my first time in RSS and I don't really know of the RSS-specific optimizations, but I think this did pretty well.

Piccard III on the runway (Piccard I had issues with asymmetric thrust under high time warp and Piccard II didn't have enough wing area)

Climbing to altitude

Settled down at Mach 0.6 and 2 degrees angle of attack. This is close to optimal for subsonic range with the Goliath engine, and this craft is designed to fly subsonic so I can get it off the runway more easily. Supercruising with the Goliath gives more range, but it would be much harder to take off and I would run into heating issues.

Gallery:

Spoiler

Flying over the Atlantic Ocean and toward the equator. I've gone about 45 degrees around Kerbin.

Somewhere over South Sudan

Over the coast of Somalia, heading over the Indian Ocean

Hit the Equator, continuing due east for a while

Sumatra

Over the Pacific Ocean, turning north toward Hawaii

Crossing the International Date Line. At this point I am 11000 km from KSC and I estimate my remaining range to be 11375 km.

Passing over the Big Island of Hawaii. This probably wasn't the shortest route but I wanted to do this because it was cool.

Approaching Mexico, fuel is more than sufficient to make it the rest of the way home.

Above Mexico

Approaching KSC

At this point I realized I have basically zero roll control (no ailerons!) and also I'm going to overshoot KSC. I actually do a couple of loops here to bleed velocity, but this plane has a ridiculous glide ratio so it didn't do much.

 

Final descent. I have no roll control here so I can't land on the runway, but I can still land on the grass.

Landed!

If I were to attempt this mission again, which I won't, I would probably remove some air intakes as they were a pretty big fraction of my total drag. I would also add ailerons.

A couple smaller optimizations would be to use the Mk0 fuel tank instead of Mk1 fuel tanks and the Big-S strake instead of the delta wing, which would reduce my dry mass. I didn't do this for part count reasons, but they would be reasonable upgrades with a more powerful computer than my laptop.

A large optimization would be to reduce wing area and switch to supersonic air intakes (maybe a single shock cone or ram air intake would work). Cruise would be at Mach 2 instead of Mach 0.6 - this would increase the value of speed * lift / drag, which dictates how far you can fly on a given engine and amount of fuel. You'd need a really long takeoff run to make full use of this, and I'm told there aren't a lot of large flat areas on Earth to act as a runway. But this flight is definitely beatable.

Edited May 29, 2023 by camacju
additional information