Lagrange Points And Why You Want To Get Stuck At Them

October 9, 2024 by Maya Posch 35 Comments

Visualization of the Sun-Earth Lagrange points.

Orbital mechanics is a fun subject, as it involves a lot of seemingly empty space that’s nevertheless full of very real forces, all of which must be taken into account lest one’s spacecraft ends up performing a sudden lithobraking maneuver into a planet or other significant collection of matter in said mostly empty space. The primary concern here is that of gravitational pull, and the way it affects one’s trajectory and velocity. With a single planet providing said gravitational pull this is quite straightforward to determine, but add in another body (like the Moon) and things get trickier. Add another big planetary body (or a star like our Sun), and you suddenly got yourself the restricted three-body problem, which has vexed mathematicians and others for centuries.

The three-body problem concerns the initial positions and velocities of three point masses. As they orbit each other and one tries to calculate their trajectories using Newton’s laws of motion and law of universal gravitation (or their later equivalents), the finding is that of a chaotic system, without a closed-form solution. In the context of orbital mechanics involving the Earth, Moon and Sun this is rather annoying, but in 1772 Joseph-Louis Lagrange found a family of solutions in which the three masses form an equilateral triangle at each instant. Together with earlier work by Leonhard Euler led to the discovery of what today are known as Lagrangian (or Lagrange) points.

Having a few spots in an N-body configuration where you can be reasonably certain that your spacecraft won’t suddenly bugger off into weird directions that necessitate position corrections using wasteful thruster activations is definitely a plus. This is why especially space-based observatories such as the James Webb Space Telescope love to hang around in these spots.

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Polaris Dawn, And The Prudence Of A Short Spacewalk

October 3, 2024 by Tom Nardi 40 Comments

For months before liftoff, the popular press had been hyping up the fact that the Polaris Dawn mission would include the first-ever private spacewalk. Not only would this be the first time anyone who wasn’t a professional astronaut would be opening the hatch of their spacecraft and venturing outside, but it would also be the first real-world test of SpaceX’s own extravehicular activity (EVA) suits. Whether you considered it a billionaire’s publicity stunt or an important step forward for commercial spaceflight, one thing was undeniable: when that hatch opened, it was going to be a moment for the history books.

But if you happened to have been watching the live stream of the big event earlier this month, you’d be forgiven for finding the whole thing a bit…abrupt. After years of training and hundreds of millions of dollars spent, crew members Jared Isaacman and Sarah Gillis both spent less than eight minutes outside of the Dragon capsule. Even then, you could argue that calling it a spacewalk would be a bit of a stretch.

Neither crew member ever fully exited the spacecraft, they simply stuck their upper bodies out into space while keeping their legs within the hatch at all times. When it was all said and done, the Dragon’s hatch was locked up tight less than half an hour after it was opened.

Likely, many armchair astronauts watching at home found the whole thing rather anticlimactic. But those who know a bit about the history of human spaceflight probably found themselves unable to move off of the edge of their seat until that hatch locked into place and all crew members were back in their seats.

Flying into space is already one of the most mindbogglingly dangerous activities a human could engage in, but opening the hatch and floating out into the infinite black once you’re out there is even riskier still. Thankfully the Polaris Dawn EVA appeared to go off without a hitch, but not everyone has been so lucky on their first trip outside the capsule.

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The 1924 Martian Signal: A Cosmic Curiosity

October 3, 2024 by Heidi Ulrich 22 Comments

In an age where our gadgets allow us to explore the cosmos, we stumbled upon sounds from a future past: an article on historical signals from Mars. The piece, written by [Paul Gilster] of Centauri Dreams, cites a Times essay published by [Becky Ferreira] of August 20. [Ferreira]’s essay sheds light on a fascinating, if peculiar, chapter in the history of the search for extraterrestrial life.

She recounts an event from August 1924 when the U.S. Navy imposed a nationwide radio silence for five minutes each hour to allow observatories to listen for signals from Mars. This initiative aimed to capitalize on the planet’s close alignment with Earth, sparking intrigue and excitement among astronomers and enthusiasts alike.

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Voyager 2’s Plasma Spectrometer Turned Off In Power-Saving Measure

October 2, 2024 by Maya Posch 24 Comments

The Voyager 2 spacecraft’s energy budget keeps dropping by about 4 Watt/year, as the plutonium in its nuclear power source is steadily dropping as the isotope decays. With 4 Watt of power less to use by its systems per year, the decision was made to disable the plasma spectrometer (PLS) instrument. As also noted by the NASA Voyager 2 team on Twitter, this doesn’t leave the spacecraft completely blind to plasma in the interstellar medium as the plasma wave subsystem (PWS) is still active. The PLS was instrumental in determining in 2018 that Voyager 2 had in fact left the heliosphere and entered interstellar space. The PLS on Voyager 1 had already broken down in 1980 and was turned off in 2007.

After saving the Voyager 1 spacecraft the past months from a dud memory chip and switching between increasingly clogged up thrusters, it was now Voyager 2’s turn for a reminder of the relentless march of time and the encroaching end of the Voyager missions. Currently Voyager 2 still has four active instruments, but by the time the power runs out, they’ll both be limping along with a single instrument, probably somewhere in the 2030s if their incredible luck holds.

This incredible feat was enabled both by the hard work and brilliance of the generations of teams behind the two spacecraft, who keep coming up with new tricks to save power, and the simplicity of the radioisotope generators (RTGs) which keep both Voyagers powered and warm even in the depths of interstellar space.

A Space Walk Through ISS

September 24, 2024 by Heidi Ulrich 14 Comments

The International Space Station (ISS) might not be breaking news, but this February, National Geographic released a documentary that dives into the station’s intricate engineering. It’s a solid reminder of what human ingenuity can achieve when you put a team of engineers, scientists, and astronauts together. While the ISS is no longer a new toy in space, for hackers and tinkerers, it’s still one of the coolest and most ambitious projects ever. And if you’re like us—always looking for fresh inspiration—you’ll want to check this one out.

The ISS is a masterpiece, built piece by piece in space, because why make things easy? With 16 pressurized modules, it’s got everything needed to keep humans alive and working in one of the harshest environments imaginable. Add in the $150 billion price tag (yes, billion), and it’s officially the most expensive thing humans have ever built. What makes it especially interesting to us hackers is its life support systems—recycling water, generating oxygen, and running on solar power. That’s the kind of closed-loop system we love to experiment with down here on Earth. Imagine the implications for long-term sustainability!

But it’s not just a survival bunker in space. It’s also a global science lab. The ISS gives researchers the chance to run experiments that could never happen under Earth’s gravity—everything from technology advancements to health experiments. Plus, it’s our testing ground for future missions to Mars. If you’re fascinated by the idea of hacking complex systems, or just appreciate a good build, the ISS is a dream project.

Catch the documentary and dive into the world of space-grade hacking. The ISS may be orbiting out of sight, but for those of us looking to push the boundaries of what’s possible, it’s still full of inspiration.

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Amateur Astronomer Images Spy Satellite

September 20, 2024 by Bryan Cockfield 14 Comments

As anyone who’s looked at the sky just before dawn or right after dusk can confirm, for the last seventy years or so there have been all kinds of artificial satellites floating around in low-Earth orbit that are visible to the naked eye. Perhaps the most famous in the last few decades is the International Space Station, but there are all kinds of others up there from amateur radio satellites, the Starlink constellation, satellite TV, and, of course, various spy satellites from a few of the world’s governments. [Felix] seems to have found one and his images of it can be found here.

[Felix] has been taking pictures of the night sky for a while now, including many different satellites. While plenty of satellites publish their paths to enable use, spy satellites aren’t generally public record but are still able to be located nonetheless. He uses a large Dobsonian telescope to resolve the images of several different satellites speculated to be spy satellites, with at least one hosting a synthetic aperture radar (SAR) system. His images are good enough to deduce the size and shape of the antennas used, as well as the size of the solar panels on board.

As far as being concerned about the ramifications of imaging top-secret technology, [Felix] is not too concerned. He states that it’s likely that most rival governments would be able to observe these satellites with much more powerful telescopes that he has, so nothing he has published so far is likely to be a surprise to anyone. Besides, these aren’t exactly hidden away, either; they’re up in the sky for anyone to see. If you want to take a shot at that yourself you can get a Dobsonian-like telescope mostly from parts at Ikea, and use a bit of off-the-shelf electronics to point them at just the right position too.

Watch NASA’s Solar Sail Reflect Brightly In The Night Sky

September 15, 2024 by Donald Papp 14 Comments

NASA’s ACS3 (Advanced Composite Solar Sail System) is currently fully deployed in low Earth orbit, and stargazers can spot it if they know what to look for. It’s actually one of the brightest things in the night sky. When the conditions are right, anyway.

What conditions are those? Orientation, mostly. ACS3 is currently tumbling across the sky while NASA takes measurements about how it acts and moves. Once that’s done, the spacecraft will be stabilized. For now, it means that visibility depends on the ACS’s orientation relative to someone on the ground. At it’s brightest, it appears as bright as Sirius, the brightest star in the night sky.

ACS3 is part of NASA’s analysis and testing of solar sail technology for use in future missions. Solar sails represent a way of using reflected photons (from sunlight, but also possibly from a giant laser) for propulsion.

This perhaps doesn’t have much in the way of raw energy compared to traditional thrusters, but offers low cost and high efficiency (not to mention considerably lower complexity and weight) compared to propellant-based solutions. That makes it very worth investigating. Solar sail technology aims to send a probe to Alpha Centauri within the next twenty years.

Want to try to spot ACS3 with your own eyes? There’s a NASA app that can alert you to sighting opportunities in your local time and region, and even guide you toward the right region of the sky to look. Check it out!