How To Land A Model Rocket Vertically

Perhaps most readers will remember when they saw the first SpaceX demonstration of a rocket stage landing vertically on the pad under control. It’s something of a shock to be reminded that their first suborbital demonstration “hops” were around a decade ago, and how quickly what was once so special has become commonplace. We’re now in the era of the more complex model rockets having the same capability, with [BPS.space] managing it last year, and now [TTS Aerospace] sharing a video showing how they achieved the same feat.

The basics of the system revolve around a directed rocket nozzle, but to make it work is a lot more complex than simply hooking up a flight controller and calling it good. The steps in arriving at a landable rocket are examined, with plenty of failures shown along the way. Even the legs are more complex than they might appear, having to combine lightness, ease of unfurling under the power of elastic, and enough strength and give to survive a rough landing.

Those of us from countries where model rocketry is a highly licensed activity can only look on in envy at these projects, and we look forward to seeing where this avenue leads next. We covered the [BPS.space] rocket last year, should you be interested.

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A Ride-On Picnic Table For Those Idylic Summer Evenings

For most outsiders the Netherlands is a country of picturesque cities, windmills, tulips, and maybe those famous coffee shops. Head away from the coast though and you enter the country’s rural hinterland, farming country with lush green fields, dairy cattle, and farm lads doing what they do best, which is hacking old machinery to do crazy things under those wide skies. [Plodno] are based on a farm somewhere in the eastern Netherlands, and the latest of these lads’ creations is a motorised picnic table (Dutch language, you’ll need YouTube translated subtitles).

This is farm hacking at its best, with a scrap FIAT hatchback donating its running gear to a welded tubular frame, with a chain drive to a small single-cylinder engine. There’s no suspension save for the air in the tyres, the steering column is vertical, and the brake is a single inboard disk on the rear axle. Perhaps it’s fortunate that the intended beating heart, a Kawasaki motorycle engine, was misfiring, as it would have been truly lethal with that much power. We’re not too convinced at the legality of taking such a contraption on the public road in the Netherlands, but they seem to get away with it. Take a look at the build in the video below the break.

Here at Hackaday we like a good hacky farm build, even though sometimes they’re not so well-assembled.

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High Voltage Ion Engines Take Trip On The High Seas

Over the last several months, we’ve been enjoying a front-row seat as [Jay Bowles] of Plasma Channel has been developing and perfecting his design for a high voltage multi-stage ionic thruster. With each installment, the unit has become smaller, lighter, and more powerful. Which is important, as the ultimate goal is to power an RC aircraft with them.

There’s still plenty of work to be done before [Jay] will be able to take his creation skyward, but he’s making all the right moves. As a step towards his goal, he recently teamed up with [RcTestFlight] to attach a pair of his thrusters — which have again been further tweaked and refined since we last saw them — to a custom catamaran hull. The result is a futuristic craft that skims across the water with no moving parts and no noise…if you don’t count the occasional stray arc from the 40,000 volts screaming through its experimental thrusters, anyway. Continue reading “High Voltage Ion Engines Take Trip On The High Seas”

A Peek Inside A 747 Fuel Gauge

It isn’t that often that we civilians get the chance to closely examine the fantastic internals that make up the modern marvels of avionic engineering. Luckily for us, [Glen] got his hands on a 747 fuel gauge and tore it down for our benefit. Not only does he tear it down, but he also builds a controller to display values.

Unlike your typical automotive fuel gauge that reports the distance from the top of the tank to the fuel level, this gauge reports the number of pounds of fuel. The fact that the indicator pictured above can go all the way to 95,000 pounds of fuel hits home the sheer scale of the fuel tanks on a 747 compared to your Volvo. Of course, where this gets interesting is the teardown with the metal sleeve removed. A 400 HZ AC servo motor moves the pointer and counter through the gearing with the help of a feedback potentiometer. The resistance tolerance is only 3%, as there are adjustment knobs on the back. But the linearity spec is only 0.06%, putting this part in a different grade from most pots.

One of the indicators was in worse shape than the others, so [Glen] got to work tapping into the internals of the gauge to drive the motor directly. A custom AC power supply repurposed from another project provided power, and a Raspberry Pi Pico was the PID controller. For [Glen], it isn’t all roses. Unfortunately, a noisy spot around 22,500 prevents accurate placement around there.

The code is up on GitHub, and we love having a gauge on the desk to show whatever value we like. If you are curious about more 747 instruments, this retro control unit might interest you.

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The Yamato 1, a sleek grey ship that looks vaguely like a computer mouse or Star Trek shuttlecraft. It has an enclosed cockpit up front with black windows and blue trim. It is sitting on land in front of a red tower at a museum in Tokyo.

Navy Program PUMPs Up Hopes For Magnetic Propulsion

The “caterpillar drive” in The Hunt for Red October allowed the sub to travel virtually undetected through the ocean, but real examples of magnetohydrodynamic drives (MHDs) are rare. The US Navy’s recently announced Principles of Undersea Magnetohydrodynamic Pumps (PUMP) intends to jump-start the technology for a new era.

Dating back to the 1960s, research on MHDs has been stymied by lower efficiencies when compared with driving a propeller from the same power source. In 1992 the Japanese Yamato-1 prototype, pictured at the top of the page, was able to hit a blistering 6.6 knots (that’s 12 kph or 7.4 mph for you landlubbers) with a 4 Tesla liquid helium-cooled MHD. Recent advances courtesy of fusion research have resulted in magnets capable of generating fields up to 20 Telsa, which should provide a considerable performance boost.

The new PUMP program will endeavor to find solutions for more robust electrode materials that can survive the high currents, magnetic fields, and seawater in a marine environment. If successful, ships using the technology would be both sneakier and more environmentally friendly. While you just missed the Proposers Day, there is more information about getting involved in the project here.

Victorian Train Tunnel Turned Test Track

Characterizing the aerodynamic performance of a vehicle usually requires a wind tunnel since it’s difficult to control all variables when actually driving. Unless you had some kind of perfectly straight, environmentally controlled, and precision-graded section of road, anyway. Turns out the Catesby Tunnel in the UK meets those requirements exactly, and [Tom Scott] recently got to take a tour of it.

The 2.7 kilometer (1.7 mile) long tunnel was constructed as a railway tunnel between 1895 and 1897, thanks to the estate owner objecting to the idea of “unsightly trains” crossing his property. The tunnel’s construction was precise even by modern standards, deviating only 3 mm from being perfectly straight along its entire length. It lay abandoned for many years until it was paved and converted into a test facility, opening in 2021.

To measure the speed without the luxury of GPS reception, a high-speed camera mounted inside a vehicle detects reflective tags mounted every 5 m along the tunnel’s wall. This provides accurate speed measurement down to 0.001 km/h. A pair of turntables are installed at the ends of the tunnel to avoid an Austin Powers multi-point turn (apparently that’s the technical term) when turning around inside the confined space.

Due to the overhead soil and sealed ends, the temperature in the tunnel only varies by 1 – 2 °C year round. This controlled environment makes the tunnel perfect for coastdown tests, where a vehicle accelerates to a designated speed and then is put into neutral and allowed to coast. By measuring the loss of speed across multiple runs, it’s possible to calculate the aerodynamic drag and friction on the wheels. Thanks to the repeatable nature of the tests, it was even possible to calculate the aerodynamic losses caused by [Tom]’s cameras mounted to the outside of the vehicle.

The Catesby Tunnel is an excellent example of repurposing old infrastructure for modern use. Some other examples we’ve seen include using coal mines and gold mines for geothermal energy.

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Bike Rides Played Back Via Aircraft Altitude Indicator

Any good bike ride should have a big climb to push your fitness, and a nice descent for the joy of careening down at high speed. [Glen Akins] has been recording his altitude during his mountain biking expeditions, and has now built a way to play them back on an aircraft altitude indicator.

A Python script is used to parse a recorded GPX file, which stores position and elevation data captured from a GPS device during [Glen]’s rides. The elevation data is then output to a Raspberry Pi Pico, which drives a set of three Microchip MCP4802 DACs and three TI OPA584 op-amps in order to create the necessary 400 Hz AC waveforms to drive the aircraft altitude indicator. One DAC and op-amp are used to generate 400 Hz AC to simply power the device, while the other two are used to generate synchro signals to actually drive the dial as needed. The maths involved is worth checking out, particularly if you’re into old-school instrumentation from the 20th century.

We’ve seen similar tinkering efforts from [Glen] before, too.

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