Model Rocket Nails Vertical Landing After Three-Year Effort

July 10, 2024 by Dan Maloney 30 Comments

Model rocketry has always taken cues from what’s happening in the world of full-scale rockets, with amateur rocketeers doing their best to incorporate the technologies and methods into their creations. That’s not always an easy proposition, though, as this three-year effort to nail a SpaceX-style vertical landing aptly shows.

First of all, hats off to high schooler [Aryan Kapoor] from JRD Propulsion for his tenacity with this project. He started in 2021 with none of the basic skills needed to pull off something like this, but it seems like he quickly learned the ropes. His development program was comprehensive, with static test vehicles, a low-altitude hopper, and extensive testing of the key technology: thrust-vector control. His rocket uses two solid-propellant motors stacked on top of each other, one for ascent and one for descent and landing. They both live in a 3D printed gimbal mount with two servos that give the stack plus and minus seven degrees of thrust vectoring in two dimensions, which is controlled by a custom flight computer with a barometric altimeter and an inertial measurement unit. The landing gear is also clever, using rubber bands to absorb landing forces and syringes as dampers.

The video below shows the first successful test flight and landing. Being a low-altitude flight, everything happens very quickly, which probably made programming a challenge. It looked like the landing engine wasn’t going to fire as the rocket came down significantly off-plumb, but when it finally did light up the rocket straightened and nailed the landing. [Aryan] explains the major bump after the first touchdown as caused by the ascent engine failing to eject; the landing gear and the flight controller handled the extra landing mass with aplomb.

All in all, very nice work from [Aryan], and we’re keen to see this one progress.

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Fly Like You Drive With This Flying RC Drift Car

May 26, 2023 by Dan Maloney 9 Comments

So it’s 2023, and you really feel like we should have flying cars by now, right? Well, as long as you ignore the problem of scale presented by [Nick Rehm]’s flying RC drift car, we pretty much do.

At first glance, [Nick]’s latest build looks pretty much like your typical quadcopter. But the design has subtle differences that make it more like a car without wheels. The main difference is the pusher prop at the aft, which provides forward thrust without having to pitch the entire craft. Other subtle clues include the belly-mounted lidar and nose-mounted FPV camera, although those aren’t exactly unknown on standard UAVs.

The big giveaway, though, is the RC car-style remote used to fly the drone. Rather than use the standard two-joystick remote, [Nick] rejiggered his dRehmFlight open-source flight control software to make operating the drone less like flying and more like driving. The lidar is used to relieve the operator of the burden of altitude keeping by holding the drone at about a meter or so off the deck. And the video below shows it doing a really good job of it, for the most part — with anything as complicated as the multiple control loops needed to keep this thing in the air, it’s easy for a sudden input to confuse things.

We have to admit that [Nick]’s creation looks like a lot of fun to fly, or drive — whichever way you want to look at it. Either way, we like the simplification of the flight control system and translating the driving metaphor into flying — it seems like that’ll be something we need if we’re ever to have full-size flying cars.

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Large Tip Driven Copter Turns Very Slowly

August 8, 2022 by Danie Conradie 21 Comments

Picking propeller size for any aircraft, but especially VTOLs, it’s a tradeoff between size and RPM. You can either move a large volume of air slowly or a small volume of air quickly. Small and fast tend to be the most practical for many applications, but if you’re thinking outside the box like [amazingdiyprojects], you can build a massive propeller and make it fly at just one revolution per second. (Video, embedded below the break.)

One of the challenges of large propellers is their high torque requirements. To get around this, [amazingdiyprojects] drives the 5m diameter propeller from the tips using electric motors with propellers. The blades are simple welded aluminum frames covered with heat-shrunk packing tape, braced with wires for stiffness.

The flight controller, with its own battery, is prevented from spinning with the blades by counteracting the spin of a small DC motor. Each blade is equipped with a servo-driven control surface, which can give roll and pitch control by adjusting deflection based on the blade’s radial position.

[amazingdiyprojects] control setup is very creative but somewhat imprecise. Instead of trying to write a custom control scheme, he configured the old KK2.15HC flight controller for a hexacopter. Each control servo’s PWM signal routes through a commutator disc with six sectors, one for each motor of the virtual hexacopter. This means each of the servos switches between six different PWM channels throughout its rotation. To compensate for lag when switching between channels, [amazingdiyprojects] had to tune the offset of the commutator disc otherwise it would veer off in the wrong direction. After a second test flight session to tune the flight controller settings, control authority improved, although it is still very docile in terms of response.

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Foam F-35 Learns To Hover

July 15, 2021 by Tom Nardi 2 Comments

With cheap RC hardware, powerful motors, and high-capacity battery packs, getting something to fly has never been easier. It also helps that, whether you’re into fixed-wing craft or multirotors, there’s plenty of information and prior art floating around online that you can use to jumpstart your own build. But when it comes to homebrew vertical take-off and landing (VTOL) planes, things are a bit trickier.

Luckily for us, [Nicholas Rehm] has made all the plans and information necessary to duplicate his incredible RC F-35 available for anyone who wants to experiment with these relatively niche fliers. Even if it was a standard park flier, the build would be worth a close look thanks to the vectored thrust motors that give it phenomenal maneuverability and a top speed in the neighboorhood of 120 KPH (80 MPH). But with the flick of a switch, the plane transitions into a tricopter-like flight mode that allows it to land and takeoff vertically.

How does it work? The downward facing motor just behind the “cockpit” lifts up the front of the foam flier and tilts left and right to provide yaw control, while the two motors on the back tilt down to lift up the rear of the aircraft. Aviation buffs in the audience may recognize this as being fairly close to how the actual F-35B hovers, although on the real jet fighter, downward thrust under the wings is generated by redirected turbine exhaust rather than dedicated motors, and yaw control is provided by swiveling the engine’s nozzle rather than the front lift fan.

Getting the plane to takeoff vertically was one thing, but being able to transition from a hover into forward flight was quite another. To make this aerial transformation possible [Nicholas] actually had to write his own flight controller software, which he calls dRehmFlight. The GPLv3 code runs on the Teensy 4.0 and uses the common GY-521 MPU6050 gyroscope/accelerometer, so you don’t need to get any custom boards spun up just to give it a test ~~drive~~ flight. In the video below he walks through configuring the software for VTOL operation by defining how each control surface and motor is to respond to control input given the currently selected flight mode.

It probably won’t surprise you to hear that this isn’t the first time [Nicholas] has experimented with unusual flying machines. Last year we covered his RC Starship, which managed to stick the “belly flop” landing even before SpaceX managed to get the real life version down in one piece.

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DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions

February 15, 2021 by Danie Conradie 10 Comments

The availability of cheap and powerful RC motors and electronics has made it possible for almost anyone to build an RC flying machine. Software is usually the bigger challenge, which has led to the development of open-source packages like BetaFlight and Ardupilot. These packages are very powerful, but not easy to modify if you have unconventional requirements. [Nicholas Rehm] faced this challenge while doing his master’s degree, so he created dRehmFlight, a customizable flight controller for VTOL aircraft. Overview video after the break.

dRehmFlight runs on Teensy 4.0 with a MPU6050 or MPU9250 IMU

[Nicholas] has been building unique VTOL aircraft for close to a decade, and he specifically wanted flight stabilization software that is easy to modify and experiment with. Looking at the dRehmFlight code, we think he was successful. The main flight controller package is a single file of fewer than 1600 lines. It’s well commented and easy to figure out, even for an inexperienced programmer. A detailed PDF manual is also available, with full descriptions for all the functions and important variables, and a couple of tutorials to get you started. Libraries for interfacing with accelerometers and RC gear is also included. It runs on a 600 Mhz Teensy 4.0, and all the programming can be done from the Arduino IDE.

[Nicholas] has repeatedly demonstrated the capabilities of dRehmFlight with several unique aircraft, like the belly flopping RC Starship we covered a while ago, a VTOL quad rotor biplane, VTOL F35, and the cyclocopter seen in the header image. dRehmFlight might not have the racing drone performance of BetaFlight, or advanced autopilot features of Ardupilot, but it’s perfect for getting unconventional aircraft off the ground. Continue reading “DRehmFlight: Customizable Flight Stabilisation For Your Weird Flying Contraptions” →

Controlling A Quadcopter With One Dead Motor

January 28, 2021 by Danie Conradie 17 Comments

Quadcopters have incredible flying abilities, but if one loses just a single motor, it drops like a rock. Researchers from the University of Zurich’s Robotics and Perception Group have proven that this does not need to be the case by keeping a quadcopter flying with only three motors.

A quadcopter usually has enough thrust to stay aloft with only three motors, but it will spin uncontrollably in the yaw axis. It is impossible to stop a quadcopter from spinning, so the focus for researchers was on keeping the drone controllable while it’s spinning. To achieve this, accurate position and motion estimation is required, so they attached a pair of cameras to the bottom of the craft for visual-inertial odometry (VIO). One is a normal optical camera, while the other is an event camera, which has pixels that can independently respond to changes in light as they occur. This means that it has better low light performance and does not suffer from motion blur.

The feeds from the cameras are analyzed in real-time by an onboard Nvidia Jetson TX2 for state estimation, which is then used with an optical range sensor and onboard IMU to maintain controlled flight, as demonstrated in the video after the break. The research paper is free to read, and all the code is available on GitHub.

New developments in drone control schemes are always fascinating, like this hexacopter with an innovative motor layout to achieve six degrees of freedom, or a conventional helicopter with a virtual swash plate.
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Flies Like A Quadcopter, But This Drone Design Has Only One Propeller

November 2, 2020 by Danie Conradie 35 Comments

When mentioning drones, most people automatically think of fixed-wing designs like the military Reaper UAV or of small quadcopters. However, thanks in large part to modern electronics, motors, and open-source control systems, it is possible to build them in a variety of shapes and sizes. [Benjamin Prescher] is working on the second version of his single rotor Ball-Drone, which uses four servo-actuated fins for control.

The first version of the ball drone flew but was barely controllable and had a tendency to tip over. After a bit of research, he found that he had fallen victim to the drone pendulum fallacy by mounting the heavy components below the propeller and control fins. Initially, he also used conventional fin control that caused the servos to jitter due to high torque loading. By changing to grid fins, the actuation torque was reduced, eliminating the servo jitter.

Mk2 corrected the pendulum problem by moving most of the components to the top of the drone. The 3D printed frame (available on Thingiverse) was also dramatically changed and simplified to reduce weight. Although [Benjamin] designed a custom flight controller with custom control software, the latest parts list contains an off-the-shelf flight controller. He mentions that he had started working with Betaflight. The most complex part of a drone is not the mechanics or even the electronics, but the control software. Thanks to open source projects like Betaflight and Ardupilot, you don’t need to write control software from scratch to get something in the air.

The ball drone seems well suited to an indoor environment, but we’re not sure if it has any real advantages over a quadcopter with ducted propellers. Servos are cheaper than motors and ESCs, so there might be a small cost saving. Drop your thoughts on the advantages/disadvantages in the comments below. Continue reading “Flies Like A Quadcopter, But This Drone Design Has Only One Propeller” →