Dragonshy - VTOL SSTO to minimus

[drewscriver]

It's so good to have the forums back, I've wanted to share this since last week.

Anyhow, I was inspired by Cupcake into wanting to build some VTOLs, but I'm a bit of a sucker for wings, and Dragonshy was the result. She's a nimble, flexible and forgiving craft - a petite little monster (clocking in at almost 300 parts) of a SSTO.

In a nutshell: two pictures from one flight

And for more detail, the imgur album

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A better pilot than me could probably save more fuel, but even with that, I'm not sure if it can stick a Mun landing without adding drop tanks. As-is, stock Dragonshy has *barely* enough thrust for a VTOL takeoff - you'll want to use a brief burst of the rockets as soon as the jet spools up and it starts feeling light on the ground.

The fuel tanks burn evenly, for COG stability - in fact, the COG does not move at all, due to symmetrical fuel tanks and obsessive balancing. If anything, handling improves, as there is less mass further from the COG, so it can turn more quickly. Thanks to m4v for creating RCS Build Aid - it was invaluable. As part of that balancing, the Dragonshy sports three reaction wheels - so it's quite nimble.

As a relatively new builder, I had to get creative to get it all to work; in particular, getting the fuel logic to behave while using a ton of decorative intakes gave me fits. Still, I'm very happy with the end result, and I hope you all enjoy it as well.

So, if you'd like an all-stock VTOL-capable SSTO with a LVN that can take it to minimus, here's the Download Link (dropbox, right click to save)

Action groups as follows:

1: toggle horizontal turbojet engine

2: toggle horizontal (Nuke) engine

3: toggle vertical jet engine

4: toggle vertical rockets

6: lock gimbol on vertical jet/rocket engines (necessary if you want to VTOL stably - engines do not account for being above the COG in their vectoring, so they will actually work against you. You will have to hit the key twice the first time - not sure why)

7: toggle first 2 intakes

8: toggle next 8 intakes

9: toggle final 42 intakes

(yes, over 1/6 of the craft parts are intakes)

Abort sequence - detach cockpit & toggle parachute.

If you continue to stage, it will also detach the cockpit and deploy the emergency chute, but not in one step.

Standard SSTO flight profile.

Pre-flight:

Before throttling up, activate all engines by staging once on the runway, then shut down unnecessary engines (2-4)

Double tap 6 to lock gimbals on vertical thrusters (necessary for stability)

Hit 8 and 9 to close all but 2 intakes (this will save a lot of fuel on the ascent)

Note: if you're going to turn on RCS, 25,000 is a good altitude to do so, but I've actually never needed it for anything but docking - the Dragonshy is a very steady craft, and the reaction wheels provide more than enough control authority, even without atmosphere.

Flight:

You should be able take off once you get up to 50 m/s, work to gain altitude as quickly as possible, the usual SSTO 45 degree ascent profile is fine.

At around 16000 feet or so, your intake air should be down to about .04 or less, hit 8 to open up the second group of intakes, you should be climbing rapidly. At around 23000 feet, you should drop the nose a bit to 30-35 degrees.

At 25,000 feet or above, your intake air should again be at .04 or lower - hit 9 to open the last group of intakes.

When you reach 30,000 feet or above, begin dropping the nose to 20 degrees, or less - until your altitude is stable. The air is quite thin now, so you need to build speed for orbit, and to keep engines from starving of oxygen.

Once you have 2,000 m/s or more, pull the nose up to begin climbing again. At about 38,000 feet or above, your engine will start to cut out; you can throttle back a bit, hit 2 to engage the nuke, or both.

Soon, your TurboJet will cut out altogether - hit 7, 8, and 9 to close all intakes to reduce drag. Hit 2 for the nuke, if you haven't already, and boost into orbit.

Circularize, etc, as normal - the Dragonshy is quite friendly for docking, as the weight distribution means that the RCS is perfectly balanced, and does not introduce any unwanted torque or lateral movement.

Re-entry - it's pretty forgiving, I've never had a problem. You might be able to get it to spin if you go at too steep an angle, but it should be recoverable.

Have fun!

-Drewscriver

Edited September 27, 2013 by drewscriver
Added flight profile

[Rune]

Sir, you have just graduated in SSTO design! And you did this without enabling part clipping? Well, if I were you I'd drop the pretense, and just start turning it on always, you will save tons of time. You might also want to check out the "Editor tools" mod, it must have saved me days on the VAB by now. Just one tiny detail: don't you have way too many intakes? With 6-1 intake-jet ratio and decent T/W you can make 2,300m/s in atmosphere, and the rest is just part count and drag IMO... I never go beyond that, but even if I went... well, 42-1 is definitely a bit excessive. Though I guess that makes it more kerbal, right?

Rune. Looking slick, too.

[Bobhendly]

How does that thing not Get "Unplanned vessle disassembly"?

[Bobhendly]

I Want one!

[Poryy]

Download, please! I can never make a decent plane...

[inigma]

A little big, but SSI is interested in seeing this design submitted. See my sig for link. Else we'll just pilfer the idea anyways.

[drewscriver]

Thanks Rune, I'm glad you like it. You may have a point on the part clipping - magic struts are basically the same thing, I'll have to see if it enables enough other possibilities (or saves enough time) to want to cross that particular mental line.

I'd never heard of "Editor tools", but after a brief glance, it does indeed look pretty useful. As it was, there were a couple of parts I put together in the VAB and hauled over via subassembly, so that could be a time-saver at the least, even without the additional options.

I'm still fairly new to building, so I haven't settled on the 'right' ratio yet - this is definitely a huge leap on intake ratios, compared to any craft I've had before. You're right that 52 intakes is well into diminishing-returns-land, so I could probably peel a few off without harming the looks. They're so light and cheap, though, adding intakes is like eating popcorn and up at 39,000 the air is so thin that it's easy to start hitting orbital velocities without burning a lot of fuel.

Glad the looks work for you!

[drewscriver]

Bobhendly, A few well-placed struts seem to do the trick. In practice, it's actually been sturdy enough, but when it does crash (such as my ill-fated Mun attempts), the explosions go on for a while...

The download link is in the post, so feel free to grab a copy and try it out

inigma,

I'm pleased to hear that SSI likes the Dragonshy. So long as it's not too wingy, I guess this would be a type I. I'll have to give it another spin and actually take a few notes on the flight profile.

Edited September 24, 2013 by drewscriver

[Sirine]

Thanks for sharing. Downloaded your plane for testing purposes.

[Cupcake...]

A VTOL SSTO is a pretty rare thing, one that can make it to Minmus and back rarer still, so well done, that's a fantastic achievement and a great looking ship to boot. Nice to see the Scythe sitting on the pad too.

Cupcake...

Edited September 25, 2013 by Cupcake...

[drewscriver]

Poryy, you can download the Dragonshy here: download link (dropbox, right click to save) - I hope it helps in your aircraft quest.

Thanks for the interest, Sirine, I'd be interested in hearing how the testing goes.

Cupcake, the Scythe mk2 earned its spot - it was the first VTOL I actually had any success in flying. I still need to pick up a joystick. Unfortunately, I haven't seen that logitech one sold yet here.

Anyhow, I'm glad you like the Dragonshy. I've always enjoyed your craft and the videos you make - eventually, I'd like to put together something similar.

For the moment, I'm spending most of my effort on trying to make a larger, longer-range craft, hopefully with some carrying capacity, but it's proving extremely problematic. Being unable to use thrust vectoring if the engine is above the COM is a real annoyance.

[Rune]

Thanks Rune, I'm glad you like it. You may have a point on the part clipping - magic struts are basically the same thing, I'll have to see if it enables enough other possibilities (or saves enough time) to want to cross that particular mental line.

I'd never heard of "Editor tools", but after a brief glance, it does indeed look pretty useful. As it was, there were a couple of parts I put together in the VAB and hauled over via subassembly, so that could be a time-saver at the least, even without the additional options.

Mostly, I use it because it has this great feature, "enable/disable surface attachment" (ALT+R). That allows you a lot of things, but the main thing is that you no longer need small cubic struts to place engines and tanks and that kind of stuff where you want them (i.e: engine clusters without additional parts). A stiffer connection, and fewer parts, so win all around. As a secondary and awesome feature, turning it off allows you to place stuff inside cargo bays without it trying to attach to the walls, or in hard-to-reach places (the part you disable it for behaves like an engine or a decoupler, it will only stick to attachment points). It also helps that turning on/off part clipping becomes a easy as ALT+Z.

Rune. Mental lines are important stuff, BTW, feel free to keep yours intact.

[Exothermos]

This looks killer! I'll definitely be messing with this an tearing it apart. I'm trying to do something sorta similar right now.

[drewscriver]

Rune The jury is still out on clipping; it's a line, but not necessarily uncross-able. I've never experimented with the full no-clip mod, but if it works the way I'm imagining, between it and edit tools, I could revamp the Dragonshy to eliminate 30+ struts, so it might be worthwhile to make a second version - I'll have to do some testing. Edit tools seems like it would be worth it for the increased symmetry options alone - everything else would be a bonus

Exothermos - Good luck, and I hope it's useful. This was definitely my most challenging build to date, but I'm not going to speculate on whether or not that resulted in clever build techniques. Feel free to let me know if you have any questions, though.