Tracking Satellites With A Commodore PET

October 29, 2020 by Chris Lott 17 Comments

A recent writeup by Tom Nardi about using the 6502-based NES to track satellites brought back memories of my senior project at Georgia Tech back in the early 80s. At our club station W4AQL, I had become interested in Amateur Radio satellites. It was quite a thrill to hear your signal returning from space, adjusting for Doppler as it speeds overhead, keeping the antennas pointed, all while carrying on a brief conversation with other Earth stations or copying spacecraft telemetry, usually in Morse code.

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Engine Trouble Delays SpaceX’s Return To The ISS

October 27, 2020 by Tom Nardi 20 Comments

A crewed mission to the International Space Station that was set to depart from Kennedy Space Center on Halloween has been pushed back at least several weeks as NASA and SpaceX investigate an issue with the company’s Merlin rocket engine. But the problem in question wasn’t actually discovered on the booster that’s slated to carry the four new crew members up to the orbiting outpost. This story starts back on October 2nd, when the computer aboard a Falcon 9 set to carry a next-generation GPS III satellite into orbit for the US Space Force shut down the engines with just two seconds to go before liftoff.

The fact that SpaceX and NASA have decided to push back the launch of a different Falcon 9 is a clear indication that the issue isn’t limited to just one specific booster, and must be a problem with the design or construction of the Merlin engine itself. While both entities have been relatively tight lipped about the current situation, a Tweet from CEO Elon Musk made just hours after the GPS III abort hinted the problem was with the engine’s gas generator:

As we’ve discussed previously, the Merlin is what’s known as an “open cycle” rocket engine. In this classical design, which dates back to the German V-2 of WWII, the exhaust from what’s essentially a smaller and less efficient rocket engine is used to spin a turbine and generate the power required to pump the propellants into the main combustion chamber. Higher than expected pressure in the gas generator could lead to a catastrophic failure of the turbine it drives, so it’s no surprise that the Falcon 9’s onboard systems determined an abort was in order.

Grounding an entire fleet of rockets because a potentially serious fault has been discovered in one of them is a rational precaution, and has been done many times before. Engineers need time to investigate the issue and determine if changes must be made on the rest of the vehicles before they can safely return to flight. But that’s where things get interesting in this case.

SpaceX hasn’t grounded their entire fleet of Falcon 9 rockets. In fact, the company has flown several of them since the October 2nd launch abort. So why are only some of these boosters stuck in their hangers, while others are continuing to fly their scheduled missions?

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Short Video Recaps A Long Tradition Of Space Hacks

October 23, 2020 by Roger Cheng 9 Comments

Human spaceflight has always been, and still remains, a risky endeavor. We mitigate risk by being as prepared as we can. Every activity is planned, reviewed, and practiced long before any rocket engines are ignited. But space has a history of not cooperating with plans, and thus there is a corresponding history of hacks to get missions back on track. YouTube space fan [Scott Manley] recaps some of his favorites in How a $2 Toothbrush Saved the ISS and Other Unbelievable Space Hacks.

The introduction explained this compilation was motivated by the latest International Space Station drama, where an elusive air leak has finally been tracked down. Air leaks are obviously much more worrying in a space station than in, say, a bicycle tire. Thus there exists a wide array of tools to track down leaks but they couldn’t find this one. Reportedly the breakthrough came from an improvised airflow visualization tool: leaves from a cut-open tea bag. Normally small floating particles are forbidden in space because they might end up in troublesome places. (Eyes, noses, onboard equipment…) Apparently the necessity of the hack outweighed the rules here.

Tea leaves are but the latest in a long line of hacks devised in the course of space missions, because things don’t always go according to the original plan. Or even any of the large volume of contingency plans. Solutions have to be cobbled together from resources on hand, because when we’re in space, what we brought is all we have. From directly editing production code during Apollo 14, to a field-built replacement fender for the Apollo 17 Lunar Rover Vehicle (top picture), to the $2 toothbrush pressed into service as metal debris cleaner. The mission must go on!

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OSIRIS-REx Reaches Out And Touches Asteroid Bennu

October 20, 2020 by Tom Nardi 7 Comments

After a four year trek through deep space, OSIRIS-REx made history this evening as it became the first NASA spacecraft to try and collect a surface sample from an asteroid (Editor’s note: servers may be down due to the breaking news). Once sensors verify the collected material is safely onboard, the vehicle will begin drifting away from the 490 meter wide Bennu in preparation of its eventual departure and return to Earth. If all goes according to plan, the craft’s conical Sample Return Capsule carrying its precious cargo will renter the atmosphere and land at the Utah Test and Training Range in September of 2023.

OSIRIS-REx with solar panels in “Y-Wing” configuration.

Due to its extremely low gravity and rocky surface, a traditional landing on Bennu was deemed impractical. Instead, OSIRIS-REx performed a daring touch and go maneuver that brought the spacecraft into contact with the surface for just a few seconds.

A camera on the bottom of the vehicle took images every few minutes during the descent and ran them through an onboard system called Natural Feature Tracking (NFT) that autonomously steered it away from dangerous surface features. As a precaution, the solar panels on the OSIRIS-REx were angled backwards in a “Y-Wing” configuration shortly before the descent to help protect them from striking the surface or being damaged by ejected material.

Once the colander-like Touch-And-Go Sample Acquisition Mechanism (TAGSAM) mounted to the end of the spacecraft’s 3.35 meter (11 foot) articulated robotic arm arm made contact with the regolith, pressurized nitrogen was used to kick up material and push it towards storage caches built into the mechanism. With so much riding on the successful collection of surface material, this largely passive system was selected to minimize the possible failures in the critical few seconds that OSIRIS-REx would be in contact with Bennu. Mission planners say it might take until Saturday to determine if a sample was successfully collected, and that the spacecraft has the ability to perform two more attempts if needed.

After its discovery in September 1999, both the Arecibo Observatory and the Goldstone Deep Space Network were used to make radar observations of Bennu to study its shape and size. Calculations have shown it has a cumulative 1 in 2,700 chance of striking the Earth by the year 2199. By mapping the asteroid, studying it at close range, and bringing a geological sample back home, NASA hopes to gain valuable insight on how similar near-Earth objects can be detected and ultimately diverted if needed.

It Came From Outer Space: Listening To The Deep Space Network

October 17, 2020 by Adam Zeloof 26 Comments

Ham radio operators love to push the boundaries of their equipment. A new ham may start out by making a local contact three miles away on the 2m band, then talk to somebody a few hundred miles away on 20m. Before long, they may find themselves chatting to fellow operators 12,000 miles away on 160m. Some of the adventurous return to 2m and try to carry out long-distance conversations by bouncing signals off of the Moon, waiting for the signal to travel 480,000 miles before returning to Earth. And then some take it several steps further when they listen to signals from spacecraft 9.4 million miles away.

That’s exactly what [David Prutchi] set out to do when he started building a system to listen to the Deep Space Network (DSN) last year. The DSN is NASA’s worldwide antenna system, designed to relay signals to and from spacecraft that have strayed far from home. The system communicates with tons of inanimate explorers Earth has sent out over the years, including Voyager 1 & 2, Juno, and the Mars Reconnaissance Orbiter. Because the craft are transmitting weak signals over a great distance (Voyager 1 is 14 billion miles away!), the earth-based antennas need to be big. Real big. Each of the DSN’s three international facilities houses several massive dishes designed to capture these whispers from beyond the atmosphere — and yet, [David] was able to receive signals in his back yard.

Sporting a stunning X-band antenna array, a whole bunch of feedlines, and some tracking software, he’s managed to eavesdrop on a handful of spacecraft phoning home via the DSN. He heard the first, Bepi-Colombo, in May 2020, and has only improved his system since then. Next up, he hopes to find Juno, and decode the signals he receives to actually look at the data that’s being sent back from space.

We’ve seen a small group of enthusiasts listen in on the DSN before, but [David]’s excellent documentation should provide a fantastic starting point for anybody else interested in doing some interstellar snooping.

Getting Rid Of All The Space Junk In Earth’s Backyard

October 15, 2020 by Moritz v. Sivers 85 Comments

Space, as the name suggests, is mostly empty. However, since the first satellite launch in 1957, mankind began to populate the Earth orbit with all kinds of spacecraft. On the downside, space also became more and more cluttered with trash from defunct or broken up rocket stages and satellites. Moving at speeds of nearly 30,000 km/h, even the tiniest object can pierce a hole through your spacecraft. Therefore, space junk poses a real threat for both manned and unmanned spacecraft and that is why space agencies are increasing their efforts into tracking, avoiding, and getting rid of it.
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Orbital Tracking On The NES

September 26, 2020 by Tom Nardi 17 Comments

It’s easy to dismiss the original Nintendo Entertainment System as just, well, an entertainment system. But in reality the 6502 based console wasn’t so far removed from early home computers like the Apple II and Commodore 64, and Nintendo even briefly flirted with creating software and accessories geared towards general purpose computing. Though in the end, Mario and friends obviously won out.

Still, we’re willing to bet that nobody at Nintendo ever imagined their plucky little game system would one day be used to track the course of a space station in low Earth orbit. But that’s precisely what [Vi Grey] has done with his latest project, which is part of his overall effort to demonstrate the unexpected capabilities of the iconic NES. While you’ll need a bit of extra hardware to run the program on a real console, there’s no fundamental trickery that would have kept some developer from doing this in 1985 if they’d wanted to.

If you want to see your own 8-bit view of the International Space Station, the easiest way is with an emulator. In that case, [Vi] explains how you can load up his Lua script in Mesen or FCEUX to provide the ROM with the necessary tracking data from the Internet.

To run it on a real NES you’ll not only need some type of flash cart to get the ROM loaded, but also a TAStm32 board that’s used for tool-assisted speedruns. This allows the computer to essentially “type” the orbital data into the NES by emulating rapid controller button presses. That might seem like a tall order, but it’s important to note that neither device requires you to modify the original console; the code itself runs on a 100% stock NES.

If tracking spacecraft isn’t your thing, perhaps you’d be more interested in the some of the work [Vi] has previously done on the NES. We’re particularly fond of his polyglot ROM that is a ZIP file of its own source code.

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