Fun with VTOL's

[Kerba Fett]

I've been playing with VTOL's for a few days and since I'll soon start making mod requests, I figured I'd see what others thought of this stuff.

I first got interested in this by playing with the Wayland Eagle. While it's a cheat in that you can fly for hours without running out of fuel you get to learn a lot about flying them that a 30 second descent and landing just doesn't teach.

Inspired by that I set out to see what I could come up with.

My first effort was this. It's based on the Munox pod and I edited the config to add fuel to it. I'm using the HOME radial engine and I've edited the config to make the isp 10X normal. Not realistic I know, but a 20 minute flight is a lot more fun than a 2 minute flight. It also slows down the weight shift you get as fuel burns. To use as a lander rather than a transport you could probably manage with the standard settings, but it would be more difficult.

It uses 6 engines for lift. The front and rear lift engines are mounted high on the hull to keep the center of gravity below the center of lift. This makes it more stable. The center engines are mounted on Damned Robotics rotatrons that allow them to tilt forward or back to control your forward speed without having to pitch the nose up or down. These rotation servos are pretty cool in that they have a centering mode that can be toggled. When it's off you rotate your thrust nozzles and they stay, when it's on they return to center as soon as you let go of the rotation button.

The thing handles good and can carry 18 passengers, but it looks like a flying beer can and that landing gear really looks pretty bad when it's down.

I went with a bigger version and while the landing gear looks better, I had to move the engines from the hull to the landing pods. This puts the center of lift below the center of gravity and makes it a bit more tippy, but it's still not bad.

This one uses the new passenger compartment from the latest Munox release and I've edited the config of that to hold fuel as well. It also uses the landing pods from the Wayland Eagle and I've edited the config to remove the monopropellant from them. None of these ships have any RCS on them yet.The biggest problem of this design is that the front fuel tank has more engines feeding from it than the rear tank and eventually it gets tail heavy as the front tank drains faster.

The easy fix would be to put another pair of vectored engines to feed from the rear tank, but I'd have to rebalance the craft to get them closer to the joint between the front and rear. Just adding another pair to the rear hull would place the center of lift too far back. A slightly more complex fix would be to mount 2 of the rear lift engines on servos so I could rotate them outwards and cut their lift effectivness as the center of gravity changes.

A proper fix would be a plugin that would scale down the output of certain engines to compensate for changes to balance. This is one of the addon requests I'll be posting soon.

Next I decided to try a completly balanced craft with the center of gravity at the center of the fuel tank.

The Pod is the Bac9 overview pod with the unmanned version on the back as a counterweight. It uses the HOME 3m horizontal landing legs that I've resized to fit, but they make it sit a bit close to the ground and sometimes when you land they move between the segments on either side. Not sure if the spotty connect nodes are a result of rescaling it or if they were always like that. There's also a pair of large SAS modules. The theory is that they help MechJeb's KillRot hold things still even if engine thust isn't perfect.

I use Mechjeb 2 to fly using the KillRot in the SmartASS module and the Keep Vert function to hover or climb/descend. I didn't realize till I started playing with that function that you could set a descent rate and execute it, then enter a new value and change focus from the window. This lets you drop a 1 rate, (say -50 for example) and enter a new rate while you descend. (-2 for instance) You can fly the ship, put down the gear, turn on the lights, and whatever else and when you get close to the ground all you need to do is click the execute button and your descent slows to the new rate without having to stop and type anything.

Once you're on the ground and stop descending Mechjeb automaticly shuts down your engines.

In my opinion this works way better than the landing autopilot since it won't flip you over by going full throttle at the last instant if your lander is a bit off balance.

Keep in mind that you need to be off the ground for keep vert to work. If you try to use it off the runway it seems to go full throttle and flip you over before it figures out throttle control.

Something else I noticed is that if you angle your lift nozzles outward you lose some lift effectivness but gain stability. Imagine each nozzle is angled out 30 degrees. If the craft tilts over 30 degrees the nozzle on the low side is pointed straight down and gets maximum lift while the nozzle on the high side is pointed 60 degrees to the ground and is generating mostly sideways movement. (which is much easier to fix than being inverted) Placing your thrust nozzles above your center of gravity means that you're hanging from your lift rather than trying to balance on top of it and you get more stability.

If anyone else is working with VTOL's and have any tips for me I'd love to hear them. I'd like to try and find landing gear that looks and works better and maybe some engine nozzles that fit the rotatron better. If you know of plugins that can balance fuel burn or scale engine output would also be appreciated.

[Scotius]

Very nice crafts. Would work great as crew carriers on low-g worlds. Can you share .craft files? As for fuel problem, i recommend TAC Fuel Balancer mod. It lets you decide which tank(s) should be drained, or set them up to drain equally from all.

[CalculusWarrior]

They look very nice! I especially love what you did with the B9 cockpits, it looks great! Ingenious use of DM for the centre engines, too!

[Fleb]

I have spent quite some time making VTOL too. I think the angled engines help big time, as well as RCS and avionics. I think the hardest part is actually flying them.

http://www.youtube.com/watch?v=bhaLWh9qch0&

http://www.youtube.com/watch?v=hvq_W-Aec7A

Edited May 19, 2013 by Fleb

[Kerba Fett]

Wow Fleb, It's amazing how well you fly those things and how nimble they are. Are you flying with a joystick or controller, cause you're pretty smooth on the controls for KB. Mine can take off and fly around if you're careful but they all handle like bricks with rocket engines.

As for the craft files Scotius you'd still have to edit the part configs in specific ways to get them to fly. I wouldn't really want to be distributing modified versions of other peoples parts so it's probably easier for you to just copy the basic design. For the crew transport I've edited the munox to add fuel and oxy at 720 and 880. The batteries and SAS are just ballast to move the COG back near the center of the passenger pod. You place the front and rear sets on engines so the center of thrust is as close as possible to the center of mass then fine tune it to the exact center when you place the swivel engines.

I've done a couple of newer ones that don't need any config editing except the engines. As stated previously these are the HOME radial engines with their isp edited up to 3000 and 3300 to extend runtime. These are copies with new names and titles so I can still use the stock ones in the game. I've also made a larger version to cover the Rotatron better. For that I added the line 'Rescalefactor = 1.28' to the congfig. Once again it was another copy in it's own directory with a new name and title given in the config so I can use both versions.

This one looks pretty neat and I didn't need to use the rescaled legs, but the vectored engines are mounted too high and if they swivel too far back the nose pitches down.

To construct it's Pod, B9 adaptor, Home 3M legs, HOME SAS, HOME 3M fuel, then SAS, Legs, adaptor, and pod. Total symmetry. Put the Mechjeb anywhere and you're all set.

Then I tried a stretched version of the same thing. This one is Pod, 2.5m SAS, B9 adaptor, Bp HL fuel tank, adaptor, SAS, and pod. Once again total symmetry. The wings are mostly cosmetic but their lift is centered on the cog. I also went with dual rotating nozzles on each side. In a later revision of this I lowered the front swivel engines, and raised the rear ones for more clearance when tilted all the way to the rear for rocket flight. The Front and rear lift engines were also put on action groups to allow the use of just the vectored engines when you're trying to shed velocity and altitude fast. I haven't touched the lift engines on either cockpit since I built the first VTOL with them. I just retune the balance with the center engines. Your thrust vector in the spaceplane hanger should always go through your COG and point straight down for stability. (unless you can fly like Fleb in which case stability is more of a bonus than a requirement. LOL.)

Got all the way to the Mun and back only to run out of fuel 30m above the spaceport. Lucky I thought to include parachutes in the design. Too bad they got deployed at launch due to a staging error. Poor kerbals, they're famous now.

[Guest]

Guys this is my latest and it is a whole new set of skills to fly these kinds of things but I am enjoying it a lot. TAC fuel balancer is essential. I test them by taking off with the steering thrusters unarmed. If they stay level then they're balanced. That's the most important thing. I spend a lot of time moving the vertical engines fore and aft to fine tune the balance. I thought a low CG was important, but then learned that was a relatively small consideration.

http://youtu.be/yQPD_1YJgBU

[Kerba Fett]

That's very cool Space Cowboy. It looks like you used all stock parts except for the pod. I was surprised you got that many .625 fuel tanks stacked. Last time I tried to build a rocket with them They didn't seem to like if I stacked them more than 10 or 12 high. it would stop showing the bottom connect node. By the way, if you like that pod I find the interior for the Gemini capsule in the NovaPunch pack seems to fit better than the one it comes with. You can actually fly from the cockpit with a decent view. (not that I do that often)

[Fleb]

@ Space Cowboy, that thing looks like a handful .

@Kerba, I fly with keyboard too, making extensive use of fine control though. Also love that last one Kerba, it's like a baby space turtle . Will have to make my own for my future Mun colony.

Here are two more I have been working on.

This one is my new air sea rescue VTOL, Skyranger inspired I guess.

http://www.youtube.com/watch?v=NydXSt3jYtc

This one took quite a lot of balance tuning. Ended up adding ballast tanks at the front, and an upwards pointing top thruster to keep the nose down, as it wants to pitch back uncontrollably on vertical take off, if you don't keep enough forward airspeed. The thruster also helps when it's carrying a heavy payload.

http://www.youtube.com/watch?v=dCufyWwvJjA

[Guest]

@Kerba thanks for that - this is my 4th (I think) Eagle style vehicle and it is my best one but now I don't like the look of the tanks. But I have put a lot of hours into them. I don't know if this helps but I did use the ALT / LEFT CLICK combo when I was setting up those long tanks. Also at the end of each is a strut. I'll check into Novapunch because I want to incorporate some cockpit views into my videos.

@Fleb yeah it is very much a handful but I am getting better at flying it. A couple things I have learned is to try to make minutely small corrections or inputs. Having the verniers or whatever you want to call them located flat in a plane perpendicular to the axis you want them to maneuver the craft around is important. The other note I said before - getting the thing to the point where it can take off without tilting without any pilot input is essential to good VTOL design. or at least for me. I am not bog into cheat mods and I don't consider the TAC a cheat, since in reality this would have to be incorporated into any similar design.

[Guest]

This is what I am working on at the moment. I sometimes start out with a hand drawn idea that is visually interesting and this is one of those. Might be ugly to some but I like the wing shape, and the idea that the guy is way behind the CG swiveling around. I am gonna put the gatling gun on it I think. This is my first jet VTOL. I don't like the sluggish response of the jet either. I need a different vectored engine mod though. I need one where I can start and stop at different angles. Any suggestions?

[Fleb]

I think it looks pretty cool, it's giving me a hunter killer vibe. Yeah the jet engine can be slow to ramp up, and it can get out of hand when your constantly altering the thorttle. I end up chasing the vector indicator too much, so I like to compensate with 2 radial 24-77 placed along with each jet engine, setup on an action key.

[Guest]

I hear you. Maybe I will have to resort to high altitude switching to horizontal. The use of this mod is almost impossible. Maybe I am missing something,

I saw a video where someone swivelled the original jet engines in KSP though. He had control of start stop at intermediate angles.

Edited May 24, 2013 by Guest

[Guest]

..........

Edited May 22, 2013 by Guest

[paulram16]

I saw a video where someone swivelled the original jet engines in KSP though. He had control of start stop at intermediate angles.

http://youtu.be/inkkLAfFIbY?t=16s

Don't suppose you know what mod that was do you?

[Guest]

He lists the mods used in the description but I am coming up ziltch

Edited May 22, 2013 by Guest

[Guest]

Damned Robotics is the mod - the big hinge

I have been working on it most of the day. I may get a video done tonight or tomorrow. The big hinge work, but it won't go to 90, so I used the stock tiny box girder between it and the engine fuel cylinder, at an angle.

Edited May 23, 2013 by Guest

[Guest]

There is a nice looking hinge solution in this vide - but I cant identify the mod.

Edited May 24, 2013 by Guest

[Guest]

What I accomplished today

http://youtu.be/WuL1U-YIpm8

Very hard to fly at this point

Edited May 24, 2013 by Guest

[Guest]

ok 24 hours later this is what I have. I knew I had a fundamental problem so I stripped all the unnecessary hardware including the horizontal engines. They went completely against my basic concept. Also, I finally realized I had made the huge mistake of forgetting that the fuel is in that cylinder, and not on CG at all. I replaced that with the empty cylinder part, and used two shrunken jet fuel tanks (TV Aerospace 1.3.4) ON cg on the wing struts. Today I stripped of almost all the RCS motors, and then came to realize some were actually necessary, especially during the shift from vertical to horizontal, no matter how gradual it is done.

100% hand flown. I never shut off the RCS but it flies very well once you reach 70 or 80 UNLESS you stall the small wings. I need more pitch authority, and I doubled the elevator / rudders, and I will add some forward devices next.

http://youtu.be/kXAJa9OG9GQ

Edited May 24, 2013 by Guest