How The LIGO Observatory Detects Gravitational Waves

March 24, 2021 by Lewin Day 43 Comments

Gravity is one of the more obvious forces in the universe, generally regarded as easily noticeable by the way apples fall from trees. However, the underlying mechanisms behind gravity are inordinately complex, and the subject of much study to this day.

A major component of this study is around the concept of gravitational waves. First posited by Henri Poincaré in 1905, and later a major component of Einstein’s general theory of relativity, they’re a phenomena hunted for by generations of physicists ever since. For the team at the Laser Interferometer Gravitational-wave Observatory, or LIGO, finding direct evidence of gravitational waves is all in a day’s work.

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Open Source Motion Controller For DIY Drones

March 24, 2021 by Tom Nardi 7 Comments

DJI recently introduced a slick motion controller that eschews the traditional dual-stick transmitter and allows you to fly their new “FPV Drone” with just one hand. The fact that it looks like it could double as the control stick for an X-Wing is just an added bonus. Unfortunately, that single model is the only thing the $199 USD controller is currently compatible with. Unwilling to get locked into the DJI ecosystem, [Paweł Spychalski] has developed an open source work-alike motion controller that brings gesture flying to home-built quadcopters and airplanes.

Now to be clear, you’ll still need a traditional transmitter to use this device. Rather than trying to reinvent the wheel, [Paweł] decided to implement his motion controller as an add-on for OpenTX hardware like the RadioMaster TX16S. It simply plugs into the trainer port on the back of the transmitter and acts as a secondary input. This greatly simplifies the design, as it essentially just needs to read angle data from its MPU-6050 gyro/accelerometer and forward it along to OpenTX over the serial port. Plus the fact that it’s connected to the trainer port means you can disable it and return to traditional controls in an instant if anything goes wrong.

Outside of the motion sensing gear, the ESP32-powered peripheral also has a thumb stick and a pair of push buttons nestled into its 3D printed frame. An OLED display provides some user feedback, and a holder for a 18650 cell is mounted to the back side as the controller will need its own power source when [Paweł] gets around to making its connection to the transmitter wireless.

In the video below, [Paweł] takes the motion controller for a test flight and comes away largely satisfied with the results. Some tweaks are in the works as you might expect for a first attempt, but nothing that would prevent you from building your own version today and experiencing what might be the next evolution of RC flying.

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South Korean Mapping Satellite Reaches Orbit

March 24, 2021 by Chris Lott 4 Comments

South Korea’s space program achieved another milestone yesterday with the launch of the first Compact Advanced Satellite 500 (CAS500) in a planned series of five vehicles. A second-generation Russian Soyuz 2.1a lifted the Korean-made CAS500-1 from historic Baikonur Cosmodrome in southern Kazakhstan and successfully placed it into a 500 km sun-synchronous orbit, inclined by 97.7 degrees or 15 orbits/day. Living up to its reputation as a workhorse, the Soyuz then proceeded to deposit multiple other satellites into 600 km and 550 km orbits. The satellite is pretty substantial, being 2.9 m tall and 1.9 m diameter and topping the scales at 500 kg. (Don’t be confused, like we were, by this Wikipedia article that says it is a 1.3 kg CubeSat.)

South Korea already has over a dozen satellites in orbit, and the CAS500 adds a modular space platform to the mix. It was designed by the Korea Aerospace Research Institute (KARI) to provide a core backbone which can be easily adapted to other missions, not unlike a car manufacturer that sells several different models all based on the same underlying chassis. Another down-to-earth goal of the CAS500 program was to foster the transfer of core technologies from state-owned KARI to private industry. We wonder how such figures are calculated, but reportedly 91.3% of CAS500-1 was made in Korea. Subsequent flights will further involve local services and industry.

The purpose of the first two satellites is to provide images to the private sector, for example, online mapping and navigation platforms. How popular this will be is yet to be determined — as one local newspaper notes, the 2 meter image resolution (50 cm in monochrome) pales in comparison to Google’s advertised 15 cm resolution. The next three satellites will focus on space science imagery.

The Soyuz launch is shown below, and this short video clip from KARI shows a nice animation of the satellite. Try not to cringe at the simulated whooshing sound as two satellites pass each other in the vacuum of space — turn down the volume if you need to.

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