Otherworld Aircraft

[QuantumInc]

My situation: I've accepted contracts to perform experiments on the surface of Eve. As career players know these sort of contracts require you to visit several small areas in a cluster while carrying a specific piece of equipment. Thus you need to not only land on the planet but aim your landing, and then travel horizontally somehow. Of course the easy method is to install the right mod, or build a tiny rover, but here at KSP we don't do things because they're easy. So I've designed a high lift rocket powered aircraft. I've tested on Kerbin, but not Eve. To be honest although I've logged many hours in KSP I have yet to fly an aircraft to or on another planet.

The high gravity of Eve and Jool multiply your weight, and thus the needed lift and thus presumably the size of your wings. In addition you can't use jet engines. Though any rocket plane will still have less range than the equivalent jet plane, or a plane using a electric engine from a mod.

Eve has a notoriously thick atmosphere which I believe will increase the lift provided by the wings, but also increase drag, making high speed travel impractical. Though I do believe a slower craft with an excessive number of wing parts could maximize the advantage of lift and minimize the disadvantage of drag. A rocket powered craft should glide most of the time, and only use low throttle bursts to maintain speed without losing altitude, and also during take off and turns.

On Duna, I am guessing the reverse would be true. There will be low drag, but also low lift. You could compensate with extra wings, but I would imagine a better solution would be to throttle up your rocket engines and travel at high speed in a quasi-ballistic arc. The orbit line need not reach your destination, but you ought to travel fast enough to make it visible. High speed increases lift which will help you stay aloft, but you will still be burning plenty of rocket fuel. Stopping might be tricky, but will either require excessive parachutes or excessive turning ability.

Laythe, so I've read, makes flyign easy. With low gravity, and a similar atmosphere anything that can fly on Kerbin will fly better on Laythe.

Jool would be similar to Eve except that landing is obviously not an option, and returning from low altitude flights is barely an option.

On a related note, how does one deliver a flyer into space in the first place? The most obvious answer is to make a capable space plane, but I don't have to in game technology or the personal KSP experience for a space plane, and I don't want to borrow someone else's design. Straping two planes to a mother ship is easy enough, but launching it from the KSC launch pad seem to require that the drag producing wings are near the bottom, but also requires that it can jettison stages at various points in flight without anything impacting the wings, which ofcourse extend fairly far. With nuclear engines, a sufficiently large mothership can make the journey and drop off the flyers at low orbit, though I wonder if there are any tricks for staying intact on the way down.

Obviously I am most interested in the situation I've described but I also wanted to open up to discussion to flight that utilizes the atmosphere of other planets, and also getting an aircraft from the KSC to another planet.

[Nich]

 The atmosphere on eve is five times thicker but the gravity is not five times greater you really should be able to get away with Lesswing. However the more wing  you have the slower you can fly and thus the less drag you will see I suspect a craft that flies at 200 m/s on kerbin would probably fly very nicely at  70- 80 m/s on the eve 

Most flyers delivered to space I have seen have two lifting rockets on each side to keep the wings on the bottom

[Evanitis]

Never did an Eve plane, but your logic sounds all right. At worst you'll need a few iterations before one works, but that's part of the fun.

Never did a Duna plane either, but after taking a conventional one there, I could tell your impression are again right - it needs more wing area, and 'chutes (or retro-rockets) to stop as the place is really bumpy. (Where's the fun in knowing all that by only your smarts instead of trial-and-error? )

Laythe is a breeze.

And getting planes to space unconventional ways is a joy. On a big enough (SSTO) rocket, you can just radially mount plane(s) on the bottom. That's indeed only works if you don't plan to jettison the lower parts before getting to orbit, but if the plane is small enough, this method doesn't need too high tech. I had a working design where I jettison the upper parts of the rocket - that's a bit tricky: you need to pitch away from prograde for a short while, so the debris doesn't hit anything. The higher you are, the easier it gets. A separatron or two could also help.

But the easiest solution is to just radially attach boosters to a single plane. Than it's fins stay on the bottom, and it'll work as every staged rocket does.

8 tourists to orbit from 29 parts, combining all the above hints. Though I admit, a few 360° flips are calculated into the packed dV.

Here's a high-tech solution, but I believe a considerably smaller variation would work with considerably lower tech.

And while we're at it, let me include a few designs I tried but didn't work.

Edited February 21, 2016 by Evanitis

[AlphaMensae]

If you want to fly a proper plane (and not a rocket-powered one) on Eve, then you'll have to get some new parts from mods. You can either use electric propellers (forget where they're from) or nuclear turbojets (I use the one from Atomic Age, but Interstellar has some and there are other mods).  Yeah, the atmoshpere on Eve is very thick, you don't need much of a plane to fly very easily there.

I've got a nuke plane attached to my in-transit Eve ship, getting it into space was simple, just put it and its atmo-entry package in a 3.75m fairing and put it on top of a basic 3.75m rocket.  I then docked the whole package to a port on my mothership

 

Laythe has oxygen, so normal jet engines will do, just keep the plane small so it's easy to transport, like the nuke plane above.

[KerikBalm]

7 hours ago, QuantumInc said:

The high gravity of Eve and Jool multiply your weight, and thus the needed lift and thus presumably the size of your wings. In addition you can't use jet engines. Though any rocket plane will still have less range than the equivalent jet plane, or a plane using a electric engine from a mod.

Eve has a notoriously thick atmosphere which I believe will increase the lift provided by the wings, but also increase drag, making high speed travel impractical....A rocket powered craft should glide most of the time, and only use low throttle bursts to maintain speed without losing altitude, and also during take off and turns.

...

On Duna, I am guessing the reverse would be true. There will be low drag, but also low lift. You could compensate with extra wings, but I would imagine a better solution would be to throttle up your rocket engines and travel at high speed in a quasi-ballistic arc. The orbit line need not reach your destination, but you ought to travel fast enough to make it visible. High speed increases lift which will help you stay aloft, but you will still be burning plenty of rocket fuel. Stopping might be tricky, but will either require excessive parachutes or excessive turning ability.

Laythe, so I've read, makes flyign easy. With low gravity, and a similar atmosphere anything that can fly on Kerbin will fly better on Laythe.

Jool would be similar to Eve except that landing is obviously not an option, and returning from low altitude flights is barely an option.

On a related note, how does one deliver a flyer into space in the first place? The most obvious answer is to make a capable space plane, but I don't have to in game technology or the personal KSP experience for a space plane, and I don't want to borrow someone else's design. Straping two planes to a mother ship is easy enough, but launching it from the KSC launch pad seem to require that the drag producing wings are near the bottom, but also requires that it can jettison stages at various points in flight without anything impacting the wings, which ofcourse extend fairly far.

* Eve's atmosphere does indeed provide more lift. Note that it is more than 5x as dense, as the gas composition is different and KSP models that now

L/D does not change much (as KSP does change L/D at different mach numbers, it will be *slightly* betterby gliding slower, and you can glide slower on Eve), so a rocket glider will not have more gliding range than on Kerbin after you factor in the reduced engine Isp. So... if you aren't happy with the performance of a rocket glider on kerbin, don't expect to be happy with it on Eve. You won't even be able to climb nearly as high, and since you'll have basically the same glide ratio, you won't go nearly as far.

We really should have some electric fans, or air augmented rockets/ramrockets for this planet.

* Duna's atmosphere is so thin, that LV-Ns work at near optimum Isp. Its atmosphere is denser than you'd expect based on the pressure reading because (like eve) the MW of the gas is higher. You don't have to use such copious amounts of fuel to fly on Duna... due to its low orbital velocity, you won't need as much lift as you start travelling at speeds that are a significant fraction of orbital velocity. A LV-N at 800 Isp will use roughly 3x more liquid fuel than a rapier powered space plane on Kerbin (3200 Isp) for the same thrust, and its static TWR is actually comparable to a rapier's static TWR on kerbin (~6.5 static for the LV-N on Duna, 5.35 static for the rapier on Kerbin), but LV-N powered spaceplanes are fine.... as are Poodles if you want more TWR. I haven't used nukes much as I described since i use a modded electric propulsion, but I have made working designs that cruise on LV-Ns in 1.05, though I prefer to just get to orbit, or to have a design that I don't worry about fueling if I'm not aiming for orbit. In my stock duna spaceplane, I ascend in basically a ballistic arc, but then steer and can extend my trajectory with wings when I deorbit and try to land in a specific area, then I pop chutes for a tail sitting landing. The wings in this case are also critical for allowing the design to even slow down enough to deploy drogues and main chutes before it smacks into terrain.

Also, consider lift rockets and retrorockets which I've also tried and had success with (thought I prefer the simplicity of vtols). You shouldn't neccessarily try to pack on enough chutes or wings to allow you to make a completely unpowered landing... if you only need to reduce parachute descent velocity by 10 m/s... the mass in fuel needed for that is negligible, and for most longer ranged flights, you'll use more fuel just carrying the extra mass of chutes or airbrakes or wings or whatever.

 

Pre-1.0, if it flew on kerbin, it flew on laythe even better... because it was 80% the atmospheric density and 80% the gravity. So you'd have the same landing speeds (80% lift needed due to lower gavity, 80% lift given by wings due to lower atmospheric pressure). So it would be the same take off and landing speeds, but you'd have a 25% better TWR (and slightly better Isp for rockets).

Now its 60% atmospheric pressure at sea level, 80% gravity. As jet thrust declines with atmospheric pressure, this means your jet engine craft will generally have worse sea level TWRs (while rockets will do even better due to 80% gravity and higher thrust as they get more thrust as it gets closer to a vacuum)

Any engine with a value of less than 1.33 at 0.6 atms will have a worse TWR on laythe than on Kerbin. Note that the real thrust curves are cubic splines that fit those points, so I think the real Juno values are under 1.33 at 0.6 atm. So... just the afterburning panther will do a little better.

I've had seaplanes that took off of Kerbin's oceans easily enough, but wouldn't lift off from Laythe... although with minor tweaks I was able to get them to liftoff, it was still a much harder process with narrower margins.

A jool ascent is much harder than an eve ascent. Take an eve lander... then make an eve lander that can lift that first eve lander, then strap on wings and try to fly that.... not going to happen. Any flying on Jool is just a 1 way descent down into the depths of Jool where the Kraken waits (unless you use some OP mod).

As for launching planes:

If you can't lift it with a mothership, you can try having it be the mothership, and small planes lift it (this was 1.02, not sure how well that would work now)

(this one additionally used recoverable SRBs for a vertical takeoff, because its not going to do a horizontal takeoff with that massive X tail for tailsitting landigns)

Basically what I did there was design small SSTOs with not a lot of wing area, but that were otherwise aerodynamically balanced, and then radially attached them around the center of mass of my plane that I need to get to orbit. The planes that I need to get to orbit (like the duna glider, which use modded electric propulsion)generally have an excess of wing area, so my strap on SSTOs can have less wing area.. although in that second case with the VTOL duna lander, the wingloading was a bit excessive, but I got to use the poodle for another 45 Isp in closed cycle mode (relative to the rapier), so it made it.

The SSTOs when empty have enough wing area+ lifting body area to land safely on kerbin.

Edited February 21, 2016 by KerikBalm

[RocketBlam]

Since you want to minimize drag, and don't need much lift, you'll need much smaller wings on Eve than you do on Kerbin.

That's not your big problem, though. If you're trying to return a Kerbal from Eve, you're talking about a very big and/or very well designed craft. You need roughly 9,000 d/v to get back to orbit even from Eve's higher elevations. That's more than double what you need for the same vehicle to reach Kerbin orbit. Also, you need a TWR of about 2.0 (on Kerbin). So, built a rocket that has 9,000 D/V, and a TWR of greater than 2.0 on all the stages, and that gives you an idea of what you need to get off of Eve.

As far as getting it into orbit, I generally put the lander into Kerbin orbit on one rocket, then the transfer vehicle on another. Both are probably going to be very heavy.

This is a good resource to look at for Eve ascent. 

As far as Duna goes, I find the atmosphere to be so thin that wings aren't very useful. You're better off just landing on the tail and hopping to the next spot.

Edited February 22, 2016 by RocketBlam

[Nich]

That funny I found wings to be very useful on Duna.  The hardest part was finding a flat landing area and then stopping in time.  Landing chutes would have worked wonderfully

[ShadowZone]

I have had some very weird and frustrating aerodynamic effects on Eve. Tried to build a return vehicle around a top stage that has Mk2 parts and tiny wings (so it could double as an emergency abort plane). But after a few seconds the craft flips uncontrollably, apparently due to me using those Mk2 parts and their aerodynamic properties.

So yeah... just try things out, but be prepared to do it more than once

[RocketBlam]

1 hour ago, ShadowZone said:

I have had some very weird and frustrating aerodynamic effects on Eve. Tried to build a return vehicle around a top stage that has Mk2 parts and tiny wings (so it could double as an emergency abort plane). But after a few seconds the craft flips uncontrollably, apparently due to me using those Mk2 parts and their aerodynamic properties.

So yeah... just try things out, but be prepared to do it more than once

Putting wings on the top of a vehicle (I assume that's what you mean) always results in instability. It happens on Kerbin, and I assume it's worse on Eve.

[KerikBalm]

4 hours ago, RocketBlam said:

This is a good resource to look at for Eve ascent. 

As far as Duna goes, I find the atmosphere to be so thin that wings aren't very useful. You're better off just landing on the tail and hopping to the next spot.

I don't think he's asking about a plane to get back to orbit from eve, just for flying around once there, so the ascent thread isn't so relevant.

This thread's page 2 has some amazing rocket planes for eve, but sadly I think they don't work in 1.05 (nor were any of them actually robust enough to land on eve, to complete a single stage land and return to orbit)

I find wings to be incredibly useful on Duna. Its hard to get the atmosphere to slow one down enough to pop chutes on duna, but with some wings, you can slow your descent and make more drag, all while steering towards your target. Later today I'll find a sequence of screenshots from such a landing and upload+ post them.

For now, I have this uploaded:

I forget how much thrust those two electric motors were producing, but I think static thrust on Kerbin was 30 kN, and its lower on Duna, really low at 7km, and really really low at 7kn and 200 m/s. I was able to get that plane to briefly climb over 12km, but it was not sustainable, and it fell back down... 7 km is about the limit as to what it can sustain.

Anyway, the point is that I don't need sooo much angle of attack to keep that thing flying

[ShadowZone]

3 hours ago, RocketBlam said:

Putting wings on the top of a vehicle (I assume that's what you mean) always results in instability. It happens on Kerbin, and I assume it's worse on Eve.

True.

Problem is, the Mk2 parts essentially behave like wings since they are lifting bodies. So basically Mk2 Return vehicles for Eve don't seem to be viable. But I invite everyone to prove me wrong

[KerikBalm]

I assume that you mean ascent vehicles... my return vehicles never go very far into the atmosphere of Eve. I'm not going to haull another ~1,200 m/s of fuel up from the surface of eve, and even more heat protection for the kerbin reentry from interplanetary velocity.... nope, my reutrn vehicle stays in Eve orbit when me Kerbals go down.

Mk2 should work if the whole craft is made out of mk2 sections. If you have the flattened mk2 sections up top, and cylindrical sections on the bottom, it could cause problems.

[ShadowZone]

59 minutes ago, KerikBalm said:

I assume that you mean ascent vehicles... my return vehicles never go very far into the atmosphere of Eve. I'm not going to haull another ~1,200 m/s of fuel up from the surface of eve, and even more heat protection for the kerbin reentry from interplanetary velocity.... nope, my reutrn vehicle stays in Eve orbit when me Kerbals go down.

of course, ascent vehicle is exactly what I meant

59 minutes ago, KerikBalm said:

Mk2 should work if the whole craft is made out of mk2 sections. If you have the flattened mk2 sections up top, and cylindrical sections on the bottom, it could cause problems.

Guess how I built my rocket...

[WhiteKnuckle]

I enjoy flying on Duna, it's pretty easy. What isn't easy is landing.

This is an older version of my most successful Duna spaceplane, the Boone: 

In these pics you can see a lot of the tricks I've used to make landings easier: Retro-engines on the front of the nacelles, drogue chutes on the back. Up-angled wings with landing gear designed to prevent wingtip strikes.