The “Impossible” Tech Behind SpaceX’s New Engine

February 13, 2019 by Tom Nardi 92 Comments

Followers of the Church of Elon will no doubt already be aware of SpaceX’s latest technical triumph: the test firing of the first full-scale Raptor engine. Of course, it was hardly a secret. As he often does, Elon has been “leaking” behind the scenes information, pictures, and even video of the event on his Twitter account. Combined with the relative transparency of SpaceX to begin with, this gives us an exceptionally clear look at how literal rocket science is performed at the Hawthorne, California based company.

This openness has been a key part of SpaceX’s popularity on the Internet (that, and the big rockets), but its been especially illuminating in regards to the Raptor. The technology behind this next generation engine, known as “full-flow staged combustion” has for decades been considered all but impossible by the traditional aerospace players. Despite extensive research into the technology by the Soviet Union and the United States, no engine utilizing this complex combustion system has even been flown. Yet, just six years after Elon announced SpaceX was designing the Raptor, they’ve completed their first flight-ready engine.

The full-flow staged combustion engine is often considered the “Holy Grail” of rocketry, as it promises to extract the most possible energy from its liquid propellants. In a field where every ounce is important, being able to squeeze even a few percent more thrust out of the vehicle is worth fighting for. Especially if, like SpaceX, you’re planning on putting these new full-flow engines into the world’s largest operational booster rocket and spacecraft.

But what makes full-flow staged combustion more efficient, and why has it been so difficult to build an engine that utilizes it? To understand that, we’ll need to first take a closer look at more traditional rocket engines, and the design paradigms which have defined them since the very beginning.

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Love Songs To The Microphone

February 12, 2019 by Al Williams 3 Comments

A biographer of Frank Sinatra once commented that for singers like Sinatra, their instrument is the microphone. We tend to think of microphones as ideal transducers, picking up sound faithfully. But like most electronic components, microphones are imperfect. They have a varying frequency response. They pick up popping noises when we say words like “popcorn” that are normally lost to someone listening live.

[Cheddar] has an interesting video (see below) that covers how performers like Sinatra, Bing Crosby, and Billie Holiday learned to use the microphone to their advantage. They suggest that the microphone changed the way humans sing, and they are right.

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EF50: The Tube That Changed Everything

February 12, 2019 by Al Williams 32 Comments

From today’s perspective, vacuum tubes are pretty low tech. But for a while they were the pinnacle of high tech, and heavy research followed the promise shown by early vacuum tubes in transmission and computing. Indeed, as time progressed, tubes became very sophisticated and difficult to manufacture. After all, they were as ubiquitous as ICs are today, so it is hardly surprising that they got a lot of R&D.

Prior to 1938, for example, tubes were built as if they were light bulbs. As the demands on them grew more sophisticated, the traditional light bulb design wasn’t sufficient. For one, the wire leads’ parasitic inductance and capacitance would limit the use of the tube in high-frequency applications. Even the time it took electrons to get from one part of the tube to another was a bottleneck.

There were several attempts to speed tubes up, including RCA’s acorn tubes, lighthouse tubes, and Telefunken’s Stahlröhre designs. These generally tried to keep leads short and tubes small. The Philips company started attacking the problem in 1934 because they were anticipating demand for television receivers that would operate at higher frequencies.

Dr. Hans Jonker was the primary developer of the proposed solution and published his design in an internal technical note describing an all-glass tube that was easier to manufacture than other solutions. Now all they needed was an actual application. While they initially thought the killer app would be television, the E50 would end up helping the Allies win the war.

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Security Engineering: Inside The Scooter Startups

February 12, 2019 by Brian Benchoff 62 Comments

A year ago, ridesharing scooter startups were gearing up for launch. Workers at Bird, Lime, Skip, and Spin were busy improving their app, retrofitting scooters, and most importantly, figuring out the logistics of distributing thousands of electronic scooters along the sidewalks of the Bay Area. These companies were gearing up for a launch in early summer, but one company — nobody can remember exactly who — decided to launch early. First mover advantage, and all. Overnight, these scooter companies burst into overdrive, chucking scooters out of panel vans onto the sidewalk simply to keep up with the competition.

The thing about San Francisco, and California in general, is that it’s a very direct democracy masquerading as a representative government. Yes, there are city council members and a state legislature, but the will of the people will rule. No one liked tripping over the scooters littering the sidewalks, so the scooters ended up at the bottom of a lake. Or in trees. Or in the trash. In time, city permits were issued, just like a hot dog cart or any other business operating on a public sidewalk, and the piles of electric scooters disappeared. Not before hundreds of scooters were vandalized, that is.

It’s still early in the electric scooter rental startup space, but if there’s one company leading the pack, It’s Bird. they’re getting the most press, the CEO was formerly at Lyft and Uber (which explains the press), and they’ve raised nearly a half Billion dollars in funding (which explains the press). Bird is valued at two Billion dollars, and it’s one of four major ridesharing scooter startups. Pets.com had nothing on this.

Despite how overvalued you think a scooter startup might be, they’re still a business, and they’re ruled by the bottom line. Bird has grown a lot in the past year, and with that comes engineering challenges. The Bird scooters must be more resistant to vandalism. The Bird scooters must be harder to steal. Above all else, they must remain in service longer. This is the teardown of how Bird managed to improve their bottom line and engineer a better scooter.

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Automate The Freight: Amazon Tackles The Last Mile Problem On Wheels

February 11, 2019 by Dan Maloney 85 Comments

We’ve been occasionally exploring examples of what could be the killer application for self-driving vehicles: autonomous freight deliveries, both long-haul and local, as well as some special use cases. Some, like UAV delivery of blood and medical supplies in Kenya, have taken off and are becoming both profitable and potentially life-saving. Others, like driverless long-haul trucking, made an initial splash but appear to have gone quiet since then. This is to be expected, as the marketplace picks winners and losers in a neverending quest to maximize return on investment. But the whole field seems to have gotten a bit sleepy lately, with no big news of note for quite a while.

That changed last week with Amazon’s announcement of Scout, their autonomous delivery vehicle. Announced first on Amazon’s blog and later picked up by the popular and tech press who repeated the Amazon material almost verbatim, Scout appears at first glance to be a serious attempt by Amazon to own the “last mile” of delivery – the local routes that are currently plied by the likes of UPS, FedEx, and various postal services. Or is it?

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The Deep Space Energy Crisis Could Soon Be Over

February 8, 2019 by Dan Maloney 41 Comments

On the face of it, powering most spacecraft would appear to be a straightforward engineering problem. After all, with no clouds to obscure the sun, adorning a satellite with enough solar panels to supply its electrical needs seems like a no-brainer. Finding a way to support photovoltaic (PV) arrays of the proper size and making sure they’re properly oriented to maximize the amount of power harvested can be tricky, but having essentially unlimited energy streaming out from the sun greatly simplifies the overall problem.

Unfortunately, this really only holds for spacecraft operating relatively close to the sun. The tyranny of the inverse square law can’t be escaped, and out much beyond the orbit of Mars, the size that a PV array needs to be to capture useful amounts of the sun’s energy starts to make them prohibitive. That’s where radioisotope thermoelectric generators (RTGs) begin to make sense.

RTGs use the heat of decaying radioisotopes to generate electricity with thermocouples, and have powered spacecraft on missions to deep space for decades. Plutonium-238 has long been the fuel of choice for RTGs, but in the early 1990s, the Cold War-era stockpile of fuel was being depleted faster than it could be replenished. The lack of Pu-238 severely limited the number of deep space and planetary missions that NASA was able to support. Thankfully, recent developments at the Oak Ridge National Laboratory (ORNL) appear to have broken the bottleneck that had limited Pu-238 production. If it pays off, the deep space energy crisis may finally be over, and science far in the dark recesses of the solar system and beyond may be back on the table.

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Eight Years Of Partmaking: A Love Story For Parts

February 8, 2019 by Sonya Vasquez 8 Comments

Over my many years of many side-projects, getting mechanical parts has always been a creative misadventure. Sure, I’d shop for them. But I’d also turn them up from dumpsters, turn them down from aluminum, cut them with lasers, or ooze them out of plastic. My adventures making parts first took root when I jumped into college. Back-in-the-day, I wanted to learn how to build robots. I quickly learned that “robot building” meant learning how to make their constituent parts.

Today I want to take you on a personal journey in my own mechanical “partmaking.” It’s a story told in schools, machine shops, and garages of a young adulthood spent making parts. It’s a story of learning how to run by crawling through e-waste dumps. Throughout my journey, my venues would change, and so would the tools at-hand. But that hunger to make projects and, by extension, parts, was always there.

Dear partmakers, this is my love letter to you.

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