Snark

Fun with the JV-6 "Vito" VTOL Assist Jet

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Posted (edited)

So, I had an idea for a new part in KSP, which I thought could provide novel and interesting gameplay without needing any modeling or textures (it's doable completely with just config).  So I tried making it to see what it would be like, and I've found it to be surprisingly fun while not (IMO) unbalancing the game.

It's such a simple little thing that I hesitate to publish it as a "mod", but I figure folks might like to see what it does, so I thought I'd share some of my fun little creations (and the config for the part, if anyone else would like to take a crack at it).  :)

 

JV-6 "Vito" VTOL Assist Jet

iLpC27I.png
(If you'd like to play around with it yourself, here's the config; just drop it anywhere in GameData, doesn't need anything else at all, not even ModuleManager.)

It's a small, high-thrust, air-breathing RCS thruster.  Like jet engines, it requires intake air and burns liquid fuel only, with a much higher Isp than LFO engines.

As you can see, I've simply re-used the Juno model with a bit of rescaling. ;)  In terms of how the stats balance, it's useful to compare it to the Vernor and the Juno:

  • Compared to Vernor:  3/4 the weight, 1/2 the thrust
  • Compared to Juno:  1/4 the weight, 1/3 the thrust

Yes, it has a better TWR than the Juno, but I compensate for that by giving it a significantly crappier Isp, less than 1/3 of a Juno's.  Still way better than an LFO engine, though.

I deliberately made it a bit on the weak side, so that if you've got a substantial aircraft, going to actual vertical take-off is going to be hard, unless you spam a lot of these.  On the other hand, as a takeoff assist, it can make it easier to take off and land at slower speeds and with shorter runways.

So, with that out of the way, below are some of my adventures with this part, just to see what it can do.

 

Small airplane

So, let's start with a fairly typical small / low-tech KSP airplane.

02vOWDo.png

A simple tail-dragger, powered by two Junos.  Flies great without any VTOL assistance; lifts off at 50 m/s, can land at about 30 m/s.  Let's jazz it up with a few VTOL jets, shall we?

JE2ozWv.png

Four VTOL jets added:  one on the nose, one on the tail, one on each wing.  I've played with the RCS actuator toggles so that "dorsal/ventral" is the only active linear axis.  The wing jets have "roll" activated; the nose and tail jets have "pitch" activated.  Let's see how it flies!

hKwJPud.png

It can't even vaguely do a vertical takeoff-- the combined thrust of all four VTOL jets is only slightly more than one Juno, which just isn't enough to do a dead lift.

However, they do make the takeoff run a lot shorter.  It now takes off at 25 m/s, instead of needing 50.  Part of that is because the nose jet helps to rotate the nose up off the tarmac (since this is a tail-dragger, it can't dip the tail); the rest is just because the lift makes it easier to get into the air.

It only needs just a brief burst on the jets to take off-- seconds after that, the Junos have accelerated it to the point where it doesn't need the help.

So, taking off is fun!  But the real question is... how does it land?

rqBZ6ox.jpg

Well, that was neat.  :)  Here I am, parked on the high mountain spire just to the west of KSC.  Note the short distance traveled after landing (there's not much "flat" ground behind the plane).  With the engines cut to zero and the VTOL jets working full tilt, the plane can land at around 15 m/s (down from 30ish before)-- and that's descending at a steep angle, probably around 45 degrees.  Lands fine, quickly brakes to a halt.

Now that was fun.  :)

Things I found fun about flying this craft:

  • It's more versatile in terms of where it can land and takeoff, but without losing its basic "airplane-ness".
  • I enjoyed adding some complexity to the controls when landing and taking off:  the coordination of turning RCS on/off, deploying/retracting flaps, using the active RCS thrust, etc.  Made piloting more of an adventure for me.

 

"Buck Rogers" jet hopper

2PUmvpj.png

This one was super fun to play with.  :)

It has eight VTOL jets on it:  four on the underside, and one each on front / back / left / right.  Controls are arranged as follows:

  • In flight, "control from here" is set to the probe core (needed to play nice with SAS / RCS).
  • The four jets on the underside have the "fore/aft", pitch, and yaw actuators turned on; everything else is off.  Those jets also have the "fore with throttle" setting turned on.
  • The four jets around the rim have "left/right" and "dorsal/ventral" turned on; everything else is off.
  • When taking off, activate SAS and set it to surface :radial:.  This causes it to hold the craft perfectly upright at all times.

Handles like a dream.  Turn on RCS, hold :radial:, increase throttle until it just barely lifts off, then take the throttle down just a smidgeon, so that the craft has a very slight downward acceleration and acts like you're on Gilly.

Then have fun! :)

The K key thrusts you forward (in the direction the pilot is facing); you can use I to "brake", and J/L to strafe left/right if desired.  Use occasional taps on the H key to maintain altitude.

It's incredibly stable and controllable, super easy to fly, can set it down lightly as a dandelion seed at any pinpoint location you like.  (Above you can see me landing on the VAB helipad.)

Things I found fun about flying this craft:

  • It's just so ridiculously stable, slow, and easy to control.  Way better than I expected.  I'm impressed that this takes no code, it's just stock KSP with the addition of one fairly standard part.
  • Flying it around feels just magical; can land anywhere at all!

 

"Doodlebug"

Play around with a simple VTOL that can fly around at a reasonable speed.

f6UdO2Q.png

^ That's it, that's all it is.  Probe core, reaction wheel, intake, battery, Juno, command chair, coupla Basic Fins as wings, and two VTOL jets below.  The VTOL actuators are set with "dorsal/ventral" and pitch active, everything else turned off.

This one's also fun and easy to fly.  The VTOLs have enough oomph to do perfectly vertical takeoffs and landings.  The wings are tiny, but once the Juno gets it up to around 80 m/s, there's plenty of lift and the VTOLs aren't needed.

ezB4zMr.jpg

A jaunt to the island airfield.

Easy to fly, and quick to brake / settle on the VTOLs when doing a vertical landing.

Things I found fun about flying this craft:

  • It's a fun piloting challenge during VTOL takeoff / landing, since (unlike the hopper above) the design means I can't use throttling to control the VTOL lift, nor do I have perfect-uprightness.  This means I have to manually juggle the vertical thrust, and the pitch / roll, while landing the thing.
  • It's just a fun little day-tripper thing.  Can land and take off from anywhere, but is fast enough to be able to tour a reasonably broad area.

 

Anyway, that's the fun I've had thus far.  Will add more as inspiration strikes.

If anyone else wants to play with it, the config is linked above at the top of this post-- would love to see pictures of your Vito-equipped craft, please post them here!  :)

 

Edited by Snark
slightly tweaked the VTOL model

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Awesome idea. Can't wait to see how much I can abuse it. :D

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6 hours ago, Snark said:

"Doodlebug"

I wonder where you got that name from...... ( @Just Jim).    I want to see video of this little thing in action.    The potential for local biome hopping from a bigger rover is pretty neat....

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Posted (edited)

"Love your work!"

I'm doing Exercise 1, :), and have placed the .cfg file in "GameData/Snark/JV-6 Vito.cfg".  In order to show it in the SPH, I have to search for "jv-6", as it doesn't naturally appear in the "Engines" category.

TTB1JmW.png

I have RCS on but find no way to start/actuate the engines.  I've tried all of HNIJKL...  I admit I am Very New to config file magic...  able to diagnose my problem, @Snark?

(I've tried "Always Full Action", too.)

KSP 1.6.1.

Any help much appreciated.

Edited by Hotel26

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1 hour ago, Hotel26 said:

In order to show it in the SPH, I have to search for "jv-6", as it doesn't naturally appear in the "Engines" category.

Yes, that's because it's not an engine.  ;)  It's an RCS thruster, so it's under "Command & Control", same as all the other RCS thrusters.

1 hour ago, Hotel26 said:

I have RCS on but find no way to start/actuate the engines.  I've tried all of HNIJKL...  I admit I am Very New to config file magic...  able to diagnose my problem, @Snark?

(I've tried "Always Full Action", too.)

Hmm.  You've got fuel, you've got air intakes, you've got RCS turned on, and your "control from here" point is facing forwards, so it seems to me that K should work to activate the jump jets.

However, your "Resources" display at top right doesn't show "intake air" listed.  By any chance are the air intakes deactivated, or something? (Also, is there a reason you're carrying oxidizer?)

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Posted (edited)
4 hours ago, Snark said:

under "Command & Control"

...most helpful!

4 hours ago, Snark said:

Also, is there a reason you're carrying oxidizer?

Yup.  My build checklist has steps to "gizmo-align all gear; disable steering on mains; set control authority axes/limiters; empty and lock off unrequired resources; set action keys; provide craft description including action key usage, Vr and cruise altitude/speed", at the very end of the build.  Of course, I do some prototypical testing beforehand to e.g. check the CoM/CoL balance etc, and, in general, how the concept is working out.  :)

OK, so I moved Exercise 1 and its miniJumpJet part .cfg forward into KSP 1.7...  and it works fine.

(OK, the linearRCS component has moved in the Parts tree from 1.6 to 1.7...  but it looks like this whole enterprise, as executed, might work only in 1.7...(?))

Onward & upward!

 

 

Edited by Hotel26

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@Snark That little VTOL jet looks amazing! I know you’re hesitant to turn this into a mod in its own right, but since you seem to specialise in the ‘why isn’t this stock?’ mods, maybe this little thruster could be included alongside some other useful and entirely config-based parts.

Just a suggestion, and I’m not asking for this by any means, but there are certainly a lot of useful parts which could be relatively easily made by just rescaling stock parts via config.

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12 hours ago, Hotel26 said:

OK, so I moved Exercise 1 and its miniJumpJet part .cfg forward into KSP 1.7...  and it works fine.

(OK, the linearRCS component has moved in the Parts tree from 1.6 to 1.7...  but it looks like this whole enterprise, as executed, might work only in 1.7...(?))

Ah, okay.  I always play on the most recent version of KSP, and always have trouble comprehending why anyone wouldn't, so it's easy for me to forget that lots of people actually don't.  ;)   Didn't occur to me that that might be the case here.

Yeah, I expect the config as I've given it wouldn't work except in 1.7, because it has a (hidden but necessary) dependency on the linear RCS thruster, which got revamped in 1.7, so the path I've given will only work with 1.7, I expect.  For pre-1.7 versions of KSP, you'd need to do some surgery on the config to point it at the old version of the thruster instead.

10 hours ago, RealKerbal3x said:

I know you’re hesitant to turn this into a mod in its own right, but since you seem to specialise in the ‘why isn’t this stock?’ mods, maybe this little thruster could be included alongside some other useful and entirely config-based parts.

Except that I've never been a fan of "parts packs" unless they're closely focused around a specific theme and work together well.  I dislike large everything-and-the-kitchen-sink mods; I like the experience to be more "a la carte", because everyone can pick and choose exactly what they want.  Different people like different things.  Just because someone wants an air-breathing VTOL RCS thruster doesn't mean that they want, say, a rebalanced version of the Vector that isn't so overpowered and awful, or any one of a number of other unrelated things.  I also seriously loathe clutter, and to me "clutter" includes "parts I have no use for".

So if I ever did get around to making this a "mod", it would most likely be a mod in its own right, all by itself-- for me, it's basically that or nothing at all.  My thought process thus far has been, "well, just in the name of basic human decency, this needs to be either a standalone mod or not a mod at all.  And it's so simple and small and low-effort that packaging it up as a mod would be about four times as much work as just authoring the thing in the first place, and it feels uncomfortably grandiose to me to call 'one snippet of config' a 'mod' in its own right, so I'll just let this sit here."  ;)

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@Snark I understand your reasoning...not everyone wants everything bundled together. Now that I think of it, having a bunch of random parts together in a single mod always annoys me, so I have to prune parts out.

But, if you’re going to make more of these you could always do what other modders have done and release them as ‘modlets’ in a single thread, so people can pick and choose what they want.

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5 minutes ago, RealKerbal3x said:

But, if you’re going to make more of these you could always do what other modders have done and release them as ‘modlets’ in a single thread, so people can pick and choose what they want.

Well, that's pretty much what I've done just by making a repository where I lump together odds and ends like this.  I've never bothered to "publish" it in the sense of creating a KSP thread for it, mainly because if I did that, I'd feel obliged to make a reasonable amount of effort not to duplicate what other people are already doing, which is Too Much Work™.  But it's sitting there as a convenient, publicly-visible place where people can grab stuff if it's relevant, as in the current case.

Anyway, can we please shift the conversation back to the actual topic of the thread, which is "sharing interesting craft that use this part"? ;)

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Playing around some more with it.  Here's a slightly heavier craft that can do full VTOL.

n3BsUZ2.jpg

Deliberately went with very minimalistic wings, so that it's a fairly "obligate VTOL" (stall speed's too high to land safely without the jets).  It can take off vertically:

MhKpnNw.png

...and can do fairly nicely controlled vertical landings.  Here it is, parked on the VAB helipad:

VKWK0QC.png

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These will be perfect for my Laythe Sea based SP as the stickiness of the water uses considerable thrust and valuable fuel to take off from!!!

 

Thanks!!!

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13 minutes ago, Kilo60 said:

These will be perfect for my Laythe Sea based SP as the stickiness of the water uses considerable thrust and valuable fuel to take off from!!!

I've found that these VTOL jets are super useful for seaplanes.  The problem with taking off from water is that the large amount of drag from the water can make it hard to get up to takeoff speed.  Even just one or two VTOLs can nudge the plane up a bit, so that it doesn't sink so deep in the water-- and that can greatly reduce drag, giving the engines a chance to get the plane going faster and start generating some wing lift.

So, even if you only have a little bit of VTOL power-- not even vaguely enough to vertically take off, but just enough to "boost the buoyancy" a bit-- that can make the difference between a seaplane and a speedboat.  ;)

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Posted (edited)
10 hours ago, Snark said:

that can make the difference between a seaplane and a speedboat.

and the difference between a speedboat and a hydrofoil!

Not a lot of experience (yet) with hydrofoils, but a critical point in the design seems to be getting just enough "airfoil" to lift onto the foils but not so much wing that the machine takes flight.  Judicious usage of Vitos could be just what it takes to get it up on the "feet"...

Edited by Hotel26

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20 hours ago, Hotel26 said:

Not a lot of experience (yet) with hydrofoils, but a critical point in the design seems to be getting just enough "airfoil" to lift onto the foils but not so much wing that the machine takes flight.

Yeah, I had trouble with that myself.  I've tried to make hydrofoils, and had trouble coming up with something that does have enough oomph to rise up out of the water on the foils, but doesn't have enough oomph to actually take off and fly through the air.  It's walking a very narrow line.  I never managed to build a working hydrofoil that wasn't capable of sustained atmospheric flight.

Hadn't thought to try VTOLs as a way to get up out of the water, might be worth the experiment!  :)

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Great Work, Im going to love using this to get some hoppers around science biomes!

for those like me might be new at just getting into cfg edits of new parts

Took me a minute to get the cfg file working. im on a mac I originally copied it to a text edit and saved as .cfg but it didnt read it. So copied a working parts .cfg and just copied the new miniVtolJet cfg text over the other part config and placed it by its self in a Snark Folder in Game data. worked Perfectly! 

 

Thanks for the inspiration @Snark 

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(FYI, I've slightly tweaked the .cfg file to make the part prettier.  Anybody who grabbed the config before today, you may want to get a fresh copy of it.  No changes to behavior, should work retroactively with any craft you've already built.  It just makes the part a bit prettier, is all: adds a domed "top" to it, so the part doesn't look awkward if you've got the edges of it exposed.)

 

So, here's another foray into seeing what sort of fun I can have with this part.  The craft I've played around with up to this point have been little bitty ones.  So I wanted to see:  what kind of fun can I have with a bigger craft?

Answer turns out to be:  quite a bit.  :)

E4Kjd1F.jpg

^ This chubby fellow (whose resemblance to a Fisher-Price airplane, for those of you old enough to remember such things, is entirely coincidental) clocks in at 28 tons on the runway.  Most of the fuel supply is in the wings; those conical fuel tank adapters on the back end are mostly empty, and are there just for looks and/or aerodynamics.  The large adapter tank has around 1000 units of LF in it, and the wings are full.

It carries 24 of the VTOL jets:  eight on the nose, eight on the tail, and four under each wing.  That's not even close to being enough to lift the weight of the craft-- I would have needed nearly twice as many to be able to do that.  However, I deliberately didn't want to spam VTOLs to make something that can hover-- I wanted to keep the challenge of landing, so I just wanted the VTOL jets to be an assist rather than a substitute for airplane-style takeoff and landing.

The whole shebang is powered by a single Whiplash, which is enough to cruise at around 340 m/s or so, maximum.  Not super fast, but then that's not what I was aiming for.  :)  I just wanted something that was cute-looking, maneuverable, fun to fly, and presented some interesting piloting challenges.

Here it is, putting it through its paces around KSC:

2XLFTeC.png

3x8DI2n.png

S4bSRJj.png

eHBsAvc.png

As you can see, I mounted the wings way up high on the fuselage, but gave them a significant anhedral angle (the wings slope down, so that the wingtips are relatively close to the ground).  There's no particular reason why I had to do that, other than that I just think it looks neat.  Also, adding anhedral makes it less stable on the roll axis, which I wanted for maneuverability.

I was pleasantly surprised to find that it actually flies pretty well, even without the VTOL jets.  It's super maneuverable (can pitch really hard, and the anhedral makes it nimble at rolling, too).  Without VTOL jets, it takes off at 75 m/s, and has a stall speed of about 50 m/s when landing.

With the VTOLs, though, things get more fun.  :)

Here it is, landing with VTOL assistance:

hdEUowd.png

...The VTOLs are enough to lift about 45% of the weight of the craft.  So it still can't even vaguely do a vertical take-off or landing... but it's a lot more nimble than it would be without them.  Use of the VTOLs reduces the takeoff speed to about 38 m/s, and it can land at around 15 m/s.

I've set up action groups so I can toggle deployment on the canards and the wing ailerons when taking off and landing, for a bit of extra lift.  The VTOL jets have roll / pitch actuators turned on, so it's even quicker to maneuver when they're on.

Not gonna be landing this on the VAB helipad anytime soon ;) ... but it can land in some spots that would be pretty tricky to land in for a craft like this that's not VTOL-equipped.  Here it is, parked atop the mountain spire just to the west of KSC:

xHTlpBm.png

...Landing there was quite a challenge.  For one thing, the fact that it's up at around 6000 meters altitude means that lift is reduced and stall speed is accordingly higher.  For another... I discovered that given the amount of air intakes I have on the plane, up at that altitude I've got enough air to run either the engine or the VTOLs, but not both at the same time.  :/  Makes for a very tricky landing challenge (at least for me, I'm no ace pilot), so it was fun playing around with that until I could pull it off.

(Yes, of course I could have gone back to the SPH and added some more air intakes, but where's the fun in that?)

Anyway, had a ball with this fella.  It's just a lot of fun to fly, and is nimble enough to pull off some interesting stunts, while still being tricky enough to be a fun challenge.  Now I'm gonna go look for more piloting challenges to set myself with this guy.  :)

 

[EDIT]  Played around with it a bit more, and found that I can actually get it up to (barely) 1000 m/s steady cruise at around 16-17 km altitude.  Just requires a lot of patience to build up to that.

0hk1xRf.png

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On 4/26/2019 at 2:59 PM, Snark said:

Yeah, I had trouble with that myself.  I've tried to make hydrofoils, and had trouble coming up with something that does have enough oomph to rise up out of the water on the foils, but doesn't have enough oomph to actually take off and fly through the air.  It's walking a very narrow line.  I never managed to build a working hydrofoil that wasn't capable of sustained atmospheric flight.

Hadn't thought to try VTOLs as a way to get up out of the water, might be worth the experiment!  :)

I made an amphibious hydrofoil boat that can get up to 100+ m/s. The actual hydrofoil is made of canards and wing pieces, pitched a couple of degrees. The boat will also fly if you aren't careful, but landing safely is extremely difficult.

Spoiler

 

 

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The Sonic Weasel, one of my favourite aircraft. Great handling (at low speeds) and great speed (as long as you are literally one degree above the horizon). Now with great takeoff too, courtesy of the JV-6 Vito VTOL jet!

VOzC8QP.png

Not pictured:

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