Hackaday Links: January 20, 2019

Let’s say you’re an infosec company, and you want some free press. How would you do that? The answer is Fortnite. Yes, this is how you hack Fortnite. This is how to hack Fortnite. The phrase ‘how to hack Fortnite’ is a very popular search term, and simply by including that phrase into the opening paragraph of this post guarantees more views. This is how you SEO.

Lasers kill cameras. Someone at CES visited the AEye booth, snapped a picture of an autonomous car at AEye’s booth, and the LIDAR killed the sensor. Every subsequent picture had a purple spot in the same place. While we know lasers can kill camera sensors, and this is a great example of that, this does open the door to a few questions: if autonomous cars have LIDAR and are covered in cameras, what’s going to happen to the cameras in an autonomous car driving beside another autonomous car? Has anyone ever seen more than one Cruise or Waymo car in the same place at the same time? As an aside, AEye’s company website’s URL is aeye.ai, nearly beating penisland.net (they sell pens on Pen Island) as the worst company URL ever.

This is something I’ve been saying for years, but now there’s finally a study backing me up. Lego is a viable investment strategy. An economist at Russia’s Higher School of Economics published a study, collecting the initial sale price of Lego sets from 1987 to 2015. These were then compared to sales of full sets on the secondary market. Returns were anywhere between 10 and 20% per year, which is crazy. Smaller sets (up to about 100 pieces) had higher returns than larger sets. This goes against my previous belief that a Hogwarts Castle, Saturn V, and UCS Falcon-heavy portfolio would outperform a portfolio made of cheap Lego sets. However, this observation could be tied to the fact that smaller sets included minifig-only packaging, and we all know the Lego minifig market is a completely different ball of wax. The Darth Revan minifig, sold as an exclusive for $3.99 just a few years ago, now fetches $35 on Bricklink. Further study is needed, specifically to separate the minifig market from the complete set market, but the evidence is coming in: Lego is a viable investment strategy, even when you include the 1-2% yearly cost of storing the sets.

Relativity Space got a launchpad. Relativity Space is an aerospace startup that’s building a rocket capable of lobbing my car into Low Earth Orbit with a methalox engine. They’re doing it with 3D printing. [Bryce Salmi], one of the hardware engineers at Relativity Space, recently gave a talk at the Hackaday Superconference about printing an entire rocket. The design is ambitious, but if there’s one device that’s perfectly suited for 3D printing, it’s a rocket engine. There are a lot of nonmachinable tubes going everywhere in those things.

3D Printing An Entire Rocket

If you’re ever flying into LAX and have the left side window seat, just a few minutes before landing, look out the window. You’ll see a small airport just below you and what appears at first glance to be a smokestack. That’s not a smokestack, though: that’s a rocket, and that’s where SpaceX is building all their rockets. Already SpaceX has revolutionized the aerospace industry, but just down the street there’s another company that’s pushing the manufacturing of rocket engines a bit further. Relativity Space is building rockets. They’re 3D printing rocket engines, and they’re designing what could be the first rocket engine made on Mars.

Bryce Salmi is an avionics hardware engineer at Relatively Space, and he made it out to the 2018 Hackaday Superconference to tell us all about manufacturing rockets. It’s an entirely new approach to manufacturing rockets and rocket engines with a clean-slate design that could eventually be manufactured on Mars.

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Retrotechtacular: Rocket Sleds

If you need to test rockets, missiles, or ejection-seat systems, your first instinct would be to shoot them up in the air and see what happens. But if you want data, film footage, or the ability to simply walk away from a test, you might consider running your experiment on a rocket sled.

The Holloman High Speed Test Track is a 15 km long stretch of meticulously straight railroad track located in the middle of the New Mexico desert, and bristling with measurement equipment. Today’s Retrotechtacular video (embedded below) gives you the guided tour. And by the way, the elderly colonel who narrates? He doesn’t just run the joint — he was one of the human test subjects put on a rocket sled to test the effects of high acceleration on humans. You can see him survive a run around 1:00 in. Continue reading “Retrotechtacular: Rocket Sleds”

Fail Of The Week (in 1996): The 7 Billion Dollar Overflow

The year was 1996, the European Space agency was poised for commercial supremacy in space. Their new Ariane 5 Rocket could launch two three-ton satellites into space. It had more power than anything that had come before.

The rocket rose up towards the heavens on a pillar of flame, carrying four very expensive and very uninsured satellites. Thirty-seven seconds later it self destructed. Seven billion dollars of RUD rained down on the local beaches near the Guiana Space Centre in Southern South America. A video of the failed launch is after the break.

The cause of all this was a single improper type cast in a bit of code that wasn’t even supposed to run during the actual launch. Talk about a fail.

There were two bits of code. One that measured the sideways velocity, and one that used it in the guidance system. The measurement side used a 64 bit variable, but the guidance side used a 16 bit variable. The code was borrowed from an earlier, slower rocket whose velocity would never grow large enough to exceed that 16 bits. The Ariane 5, however, could be described with a Daft Punk song, and quickly overflowed this value.

The code that caused the overflow was actually a bit of pre-launch software that aligned the rocket. It was supposed to be turned off before the rocket firing, but since the rocket launch got delayed so often, the engineers made it timeout 40 seconds into the launch so they didn’t have to keep restarting it.

The ESA never placed blame on a single contractor. The programmers had made assumptions. The engineers had made reasonable shortcuts to make their job easier. It had all made it through inspections, approvals, and finally the launch event.

They certainly learned from the event; the Ariane 5 rocket has flown 82 out of 86 missions successfully since then. It has at least five more launches contracted before it is retired in 2023 for the Ariane 6 rocket being developed now. This event also changed the way critical software and redundant systems were tested, bringing the dangers of code failure to the attention of the public for the first time.

If you want to read more, there is a great discussion on Reddit which tipped us off to this fail, a quite thorough Wikipedia article, and the original article that ran in the New York Times is mirrored here.

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Why No Plane Parachutes? And Other Questions.

This week I was approached with a question. Why don’t passenger aircraft have emergency parachutes? Whole plane emergency parachutes are available for light aircraft, and have been used to great effect in many light aircraft engine failures and accidents.

But the truth is that while parachutes may be effective for light aircraft, they don’t scale. There are a series of great answers on Quora which run the numbers of the size a parachute would need to be for a full size passenger jet. I recommend reading the full thread, but suffice it to say a ballpark estimate would require a million square feet (92903 square meters) of material. This clearly isn’t very feasible, and the added weight and complexity would no doubt bring its own risks.

Continue reading “Why No Plane Parachutes? And Other Questions.”

Air Rocket Launch Pad UI Entertains Eager Kids

Last spring [Mike] built a foam rocket launchpad which was a hit with the kids in his neighborhood. But the launch system was merely a couple of buttons so the early enthusiasm quickly wore off. He went back to the drawing board to make improvements and really hit the jackpot!

The original launch system had one button for building up air pressure with a second big red button of doom for launching the rocket. The problem was a complete lack of user feedback; all the kids could do is guess how long they needed to hold the button to achieve the highest launch. This revision adds flashing LEDs to hold the attention of the wee ones but to also function as a gauge for the new pressure control system. The visually fascinating control board also includes a removable key to prevent accidental launches.

The particulars of this are as you’d expect: it’s a bunch of plumbing to manage the air pressure, an Arduino to control it all, and additional electronics in between to make them work together.

We’re especially impressed by the leap in features and quality from the first version to this one. It’s a testament to the power of quick proofs-of-concept before committing to a more involved build. Great work [Mike]!

We’ve seen rocket launchers for adults and some neat mission control panels but [Mike’s] kid friendly launch controller really is out of this world (sorry, couldn’t resist). You’ll find a video demo of this launcher after the break.

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High powered rocket engines made from PVC pipe


For as much as we enjoy rockets, explosives, and other dangerous things, we haven’t said a word about the works of [Richard Nakka]. He’s the original hacker rocketeer with thousands of words dedicated to the craft of making things move straight up really fast. One of his more interesting builds is his series on building rocket engines out of PVC pipe written in conjunction with [Chuck Knight].

For the propellent grains, the PVC rocket didn’t use the usual potassium nitrate and sugar mixture of so many homebrew solid rockets. Instead, it uses Sorbitol, an artificial sweetener. While melting and casting the Sorbitol-based propellant grains is much easier than a sugar-based concoction,  the Sorbitol had much less thrust than a typical sugar rocket, making it the perfect candidate for a PVC engine.

For those of you wondering about the strength of a PVC engine casing, [Richard] does say making larger rocket engines out of 2 or 3-inch PVC may not make much sense due to the increased chamber pressures. There is a fairly clever reinforcement method for these PVC rockets (PDF warning) that involves using PVC couplers, but the experiments into the strength of these casings have yet to undertaken.

Thanks [Caley] for sending this one in.