My tiniest rocket plane

[Brandano]

Some time ago I managed to build a rocket plane powered by a single Rockomax 24-77 (you can see a video of it here:

). At the time I commented that I had to try and make one powered by an ANT engine.

This was a few releases ago, and we didn't yet have things like probe cores, external command seats and rover wheels. So, here is my most recent effort in creating the smallest possible rocket plane (mainly because we don't have micro air breathing engines):

The Micro Gnat:

And this is the craft file: https://drive.google.com/file/d/0B_Tszjgnsur4YU8xMlBRUFVKajA/edit?usp=sharing

The plane itself is made out of 12 parts, without turning off clipping even though the parts do indeed clip. The command seat is one major example: it's attached to the bottom of the modular girder segment that acts as fuselage and rotated so that the pilot sits inside it. It's a purely aesthetic choice, the plane flies just the same with the command seat above the girder. Another major clipping oddity is the tailwheel, that is attached to the side of the strut and flipped around, to bring its contact point in the centre of the plane. That too could be removed, with the caveat that then it will only be possible to take off from the runway, and using 100% thrust to "unstick" the plane. The Craft file holds more parts, since it includes a Lander Can cockpit to hold the pilot and enough accessories to get it out of the way before taking off. It has a probe core on it so that it can be controlled and roved somewhere where it won't cause trouble. To board the plane get the pilot close to it, then adjust your camera so that it clips through the fuselage enough to select the command seat and pull up the "board" menu. To take off detach the first stage, remove the parking brake (better to put the parking brake on before detaching the plane) and throttle up to about 1/3 thrust. Once you reach 10m/s either the plane takes off on its own or you can pull up slightly . It will potter along nicely at about 20 m/s, but even throttling back it will glide forever, powered by the flapping of the control surfaces. Landing it is possible, but hard, as it will just keep on flying, and the rover wheels don't take high speeds too well. The parachute in the nose will bring it down at 3 to 4 m/s, but it will oscillate a lot, and it's quite likely that it will land upside/down It has no reaction wheels or probe cores, so I am not sure it can be used as a re-entry vehicle, but I guess I'll have to try it. At least, since it does not have a root node, it can be saved as a sub-assembly. Another thing to test might be to replace the fuel tank with monopropellant and power it with a single linear RCS port, and see if that allows for greater fuel autonomy. And if it were to be fitted with two RCS thrusters it might even be controllable as a spaceplane and have retro-rockets for those pesky landings.

[EDIT]: here's the RCS version. It works and the RCS do indeed help in braking the plane, but they interfere a bit witht he controls, so flying it is a bit more complex: https://drive.google.com/file/d/0B_Tszjgnsur4MEJnN0FTaGdXNWM/edit?usp=sharing

The RCS tank is also MUCH heavier, so it tends to tip over more readily. that's why the landing gear arrangement was reworked.

Edited February 9, 2014 by Brandano

[Tex]

Wow, that looks pretty cool! It reminds me of Scott Manley's recent attempt at a tiny aircraft.

[Brandano]

It figures that Scott Manley would get there much earlier...

In my defence, mine takes off conventionally, with a smaller engine, and has a landing gear

[panzerknoef]

Now, make a space shuttle out of it... I've done something similar, only mine was a "lot" bigger! Congratz on this tiny plane mate!

[RocketBlam]

Awesome! I love tiny vehicles. They're a lot easier to get into orbit.

[Brandano]

Now make a shuttle out of it...

That sounded like a challenge, so I figured I'd give it a shot!

Here's my very lightweight vector just right after takeoff:

The first stage might be of interest for other designs. It really helps getting out of the thicker part of the atmosphere without adding excessive weight to the ship. Here's the three engines still going strong, even though intake air has gone down to 0 , since we are over 20000 meters:

They will flame out at about 25000 meters. They are angled toward the rocket's centre of mass, so the flameout is a non-event. But in case they are reused in another design the angle must again be finely adjusted. Just in case the radial separators will take care of cutting the engine fuel supply when they are triggered, so at the first sign of air starvation hitting the spacebar will bring things under control.

Let's skip a bit ahead. To board the (now) spaceplane all you have to do is extend the ladder, go on EVA and climb up. Once close enough rotate the camera so that it clips through the plane's frame to select the command seat and board it. Trigger the decoupler and you are free:

On a circular orbit at 100km altitude or thereabout. I had to modify the gnat, it needs a way to re-orient itself in space, and for that you need at least reaction wheels. There's no standalone reaction wheels in that sort of size, so I had to add a probe core behind the fuel tank. And a couple of solar panels. It is the bare minimum, and unless you plan ahead you can end up without electric charge and with both panels perpendicular to the sun. In that case your only hope is to get out and push, and when you do re-boarding the plane is a challenge. Burning retrograde for about a third of the tank will be enough to de-orbit to the thicker air. Probably it's possible to use even less fuel than that, this thing is very lightweight, even with the added probe core. But it's worth it to waste some more fuel and ensure that you land in the sunlit side of the planet. From there on, the re-entry is fairly simple. Just make sure you keep a positive AOA while still flying faster than 100 meters per second, or the plane will tuck under and start to tumble. Wait until the speed is slower than 60m/s (this will take a looooong time!) before opening the parachute, or the pilot will be tossed off the plane. Or just fly it for the next hour until it is low and slow enough for a landing. In my case it was a splashdown, at barely more than 10m/s. Jebediah seems rather pleased:

As usual here's the .craft file to play with:

https://drive.google.com/file/d/0B_Tszjgnsur4dlNFazI0RFFxbEk/edit?usp=sharing