Are VTOL's difficult to make for a semi-new player?

[Chano]

Hi, I've been on KSP since .90 was released but I haven't really got to know how things actually worked until 1.0. I'm pretty confident in making space planes, though I'm kinda still a newb at SSTO's. So what are the basics and fundamentals of making one and how would I make it function well and hover? If the are already answers to this type of question, it would really help if any of you have links to videos or threads that can help.

Thanks!

Edited August 31, 2015 by Chano

[SAI Peregrinus]

The hard part is balancing the thrust, especially during the transition from hover to horizontal flight and back (if desired). If you're playing pure stock it's very difficult, but RCS Build Aid can help with manually balancing engines. And Throttle Controlled Avionics - Continued makes it much easier by auto-adjusting the thrust limiters of individual engines to maintain steady flight. Davon Throttle Control Systems can make vertical/horizontal transitions easier by providing separate throttles for different engine groups, though Throttle Controlled Avionics can do effectively the same thing automatically.

[AxleMC131]

SSTO's and VTOL's. So much fun!

Ahem. VTOL's in my experience take a lot of trial and error. In the Spaceplane Hangar, the Centre of Mass, Lift and Thrust nodes are your best friend, so never underestimate them. This is especially important with a spacecraft that uses rocket fuel, as it drains from the front (or top) of the vehicle to the back (or bottom), and this throws off your centre of mass. Be ready to pump fuel around, or feel free to play around with fuel lines until you can keep the centre of mass in approximately the same place at all times.

Other than that, I do want to give this little anecdote out: A long time ago I played around with SSTO's that went to Minmus and back, just for fun. I had a very successful design I used almost religiously called the "Mirage", which had two turbojets for taking off and flying horizontally on Kerbin, a single LV-T45 for space travel, and three of the little Rockomax 48-7S (or whatever) engines for vertical landings on Minmus. The idea was to come down on the greater flats without killing my horizontal velocity, drop the wheels gently onto the surface with the vertical engines (plenty powerful for the extra-low gravity), and let the wheel brakes bring me to a stop. Of course, I had overlooked the fact that brakes only work because of friction between the wheels and the surface, and because of the aforementioned extra-low gravity, there was very little friction and thusly very little braking... I had to resort to using RCS to thrust backwards to slow me down, and used up almost all of my monopropellant...

Basically, if you're going to build an SSTO spaceplane with VTOL capabilities, and you're planning to land it like I did without killing horizontal velocity, make sure you add front-facing engines or lots of RCS for braking!

Anyway, good luck with building your vessel Chano!

[cantab]

It depends on the aircraft. Making a regular plane VTOL shouldn't be that hard. For SSTO spaceplanes it's another matter because such spaceplanes are often on the margins of what's possible, the extra weight of lift equipment could well stop you getting into orbit.

[Pecan]

SSTO = Single Stage To Orbit.

VTOL = Vertical Take-Off and Landing.

Spaceplane = Using wing/body lift during atmospheric flight.

Different but related things. Most spaceplanes, for instance, are HTOL, while rocket-only SSTOs are nearly always VTOL.

So which are you really interested in?

For now, your question, "Are VTOL's difficult ..." = Not if you use a rocket design. VTOL airbreathing designs that essentially follow a standard 'rocket' ascent-path are the same as rockets. HTOL spaceplanes are harder because you need to worry about all the time you'll spent in atmospheric flight plus all the excess mass you need for wings, etc. VTOL spaceplanes are especially hard because you not only need the HTOL capabilities but you need to add extra engines, mass, etc. etc. for VTOL and this is especially hard to balance too (without the mods mentioned).

[The_Rocketeer]

Yeh the biggest issue with VTOLs is the shifting fuel or payload mass.

Think of this like a can of worms that comes in different flavours depending on what you want your craft to look like or how you want it to behave. Spaceplane flavour is totally different to rocket flavour, and both come in jet-engine flavour and LF+O flavour. Also, unless you're on a world smaller than Minmus, ION-flavour has been withdrawn from the shelves.

[Yukon0009]

Depends, VTOLs are eay to build but hard to fly.

[The_Rocketeer]

Depends, VTOLs are eay to build but hard to fly.

Lol, not if you built them well! :-D

[Pecan]

Lol, not if you built them well! :-D

So, consensus would be, "VTOLs can be easy to build OR easy to fly"?

Hehe - sounds about right; you can build a VTOL easily, but it won't be easy to fly. If you want a VTOL that's easy to fly, it'll be hard to build.

Which answers the OP's question.

[The_Rocketeer]

Yeh, I agree with that as a general rule, tho of course the difficulty of the build gets easier with experience. As with most things in KSP, the learning curve is brutal but you rarely make the same mistake too many times before u've learned not to!

[SAI Peregrinus]

Naw, with Throttle Controlled Avionics VTOLs are easy to build and easy to fly. Just slap a bunch of engines facing roughly towards where "down" is going to be, and let the fly-by-wire take care of balancing the thrust.

[cantab]

VTOL = Vertical Take-Off and Landing.

The term "VTOL" generally implies that we're talking about aircraft though. Most will have the fuselage horizontal when taking off or landing which implies either separate lift and thrust engines or some means of rotating the engine's thrust, tailsitters are the exception. For rockets the abbreviation VTVL (Vertical Takeoff, Vertical Landing) is used instead.

[BlueCanary]

Since 1.0.3 they've become very difficult because the basic jet engines they tend to use have been heavily nerfed so it's hard to get craft light enough to vtol well. It looks like 1.1 will bring new, higher TWR jets and somewhat unnerf the basic jets to change this though. Also, the new launchpad smoke effect makes flying them near the ground very laggy and so extra difficult.

[Scarecrow88]

Agree with BlueCanary. VTOLs prior to 1.0.3 were pretty easy as the basic jet engine is relatively light and had plenty of thrust to lift a simple craft. Since they nerfed it, it no longer has enough thrust to lift any but the very lightest of craft which renders it, to all practical purposes, next to useless. Be interesting to see how the new engines in the next patch perform and whether it will ease the problems of building a decent VTOL.

[BlueCanary]

Agree with BlueCanary. VTOLs prior to 1.0.3 were pretty easy as the basic jet engine is relatively light and had plenty of thrust to lift a simple craft. Since they nerfed it, it no longer has enough thrust to lift any but the very lightest of craft which renders it, to all practical purposes, next to useless. Be interesting to see how the new engines in the next patch perform and whether it will ease the problems of building a decent VTOL.

In the 1.1 imgur album (which is all very much subject to balancing I guess) it looked like the basic jet thrust will be 135.9, bringing the TWR much nearer to useful VTOL levels, and the new 0.625m jet engine looks like it will have very good TWR (half the thrust of the current basic jet for a quarter of the mass). The new panther engine might be good too.

[GoSlash27]

Heck, I'm not a semi- new player and VTOL planes are hard for me.

Best,

-Slashy

[Jouni]

VTOL planes are supposed to be hard, especially if they're carrying any nontrivial payload. The Harrier was a good example of this: its payload/fuel capacity was around 3x higher with a horizontal takeoff.

[Stoney3K]

VTOL planes are supposed to be hard, especially if they're carrying any nontrivial payload. The Harrier was a good example of this: its payload/fuel capacity was around 3x higher with a horizontal takeoff.

The biggest problem with air-breathing VTOLs is keeping attitude because the spool-up/spool-down time of a jet is REALLY slow compared to a rocket.

Harriers have 'puffer ducts' that are essentially RCS ports fed off the turbojet's bleed air, and which can keep the plane level.

[The_Rocketeer]

The biggest problem with air-breathing VTOLs is keeping attitude because the spool-up/spool-down time of a jet is REALLY slow compared to a rocket.

Harriers have 'puffer ducts' that are essentially RCS ports fed off the turbojet's bleed air, and which can keep the plane level.

This might be true if reaction wheels weren't so easy and convenient to overcome the issue of low-speed attitude control. With even a moderately balanced craft a single fairly small wheel will make a huge difference. I recommend this solution first, but if you want to model puffer ducts use vernors over monoprop thrusters.

[GoSlash27]

VTOL planes are supposed to be hard, especially if they're carrying any nontrivial payload. The Harrier was a good example of this: its payload/fuel capacity was around 3x higher with a horizontal takeoff.

Jouni, True, but even a Harrier design would be more mass efficient than stock KSP design because it's not carrying the mass of redundant engines.

KSP VTOLs (at least the stock ones) are more like Yak-38 Forgers.

Stoney3k,

That's the part I struggle with; the engine spooling is so slow that they're difficult for me to manage in landing. That, coupled with the fact that I can't find a suitable role for them that I can't do more easily by other means keeps me from playing with them much.

Best,

-Slashy

[The_Rocketeer]

That's the part I struggle with; the engine spooling is so slow that they're difficult for me to manage in landing. That, coupled with the fact that I can't find a suitable role for them that I can't do more easily by other means keeps me from playing with them much.

I find jet VTOLs ideal for Kerbin science collection (probably Laythe too if I ever get one there...) - I usually build a small jet VTOL with a couple of drop tanks some wing-mounted science packages.

The spooling is a problem if you change your throttle settings too rapidly, but the key is to remember to watch your climbrate guage and make power adjustments based on how fast the NEEDLE is moving rather than how fast it says that YOU are moving. If the needle is slowly moving up towards zero, that means your current throttle is a touch more powerful than hover power, i.e. when you get to 0 climbrate make a minor reduction in throttle and you should just hover without climbing or falling.

Of course if u hit the go juice and expect to get an instant response you'll come down with a bump. Softly softly

[Pecan]

Hard work still. Pack and re-pack parachutes for the landing ^^.

[GoSlash27]

Hard work still. Pack and re-pack parachutes for the landing ^^.

Pecan,

I've found that I can land fine in all biomes without needing the parachutes.

The exception is KSC rooftops, which I work with a parasail.

These are much easier for me to land precisely and cheaper/ easier to design.

Best,

-Slashy

[The_Rocketeer]

Hard work still. Pack and re-pack parachutes for the landing ^^.

I'll admit, in the absence of an ejector seat (surely there's a mod for that??) I have used chutes for the occasional touchdown. On the other hand, I've used a jet VTOL to land on the peak of Mt Keverest for the science biome.

Piloting a VTOL is an art and it does take pinpoint control, but the reward is exactly that - perfection. And awesomeness.

Pecan,

I've found that I can land fine in all biomes without needing the parachutes.

The exception is KSC rooftops, which I work with a parasail.

http://i52.photobucket.com/albums/g13/GoSlash27/scihopper_zpsilgcocwt.jpg

These are much easier for me to land precisely and cheaper/ easier to design.

Best,

-Slashy

Slashy, you just blew my mind man... that's the coolest thing I've seen since the infiniglider blimp.

Edited August 30, 2015 by The_Rocketeer

[cantab]

I'll admit, in the absence of an ejector seat (surely there's a mod for that??)

Vanguard EVA Parachutes. You can bail out and grab one (or use an extra plugin to always have a chute when you EVA) or get a full-on ejection seat. Unfortunately they don't currently work with the latest FAR.