3D Printed Swirl Rocket Injector Turns Up The Heat

March 11, 2020 by Tom Nardi 14 Comments

Conceptually speaking, a liquid propellant rocket engine is actually a very simple piece of hardware. All you need to do is spray your fuel and oxidizer into the combustion chamber at the proper ratio, add a spark, and with a carefully designed nozzle you’re off to the races. Or the Moon, as the case may be. It’s just that doing it in the real-world and keeping the whole thing from exploding for long enough to do some useful work is another story entirely.

Taking the process one step at a time, [Luke Walters] has been working on a 3D printed injector that tackles the first half of the problem. After nearly a dozen different prototypes, he’s come up with a printable injector design that atomizes the fuel and combines it with pressurized air at a suitable ratio for combustion. As you can see in the video at the break, it’s certainly capable of generating some impressive fireballs.

A cloud of highly atomized alcohol from the injector.

The internal passages of the injector have been designed in such a way that fuel (91% isopropyl alcohol) and air are spinning in opposite directions when they meet. This promotes more complete mixing, which in turn leads to a more efficient burn. Originally developed in the 1930s, so-called “swirl injectors” of this type were one of the key technological advancements made by Germany’s V-2 rocket program. Some ideas never go out of style.

Since the injector only touches the fuel and air prior to ignition, it doesn’t need to be particularly heat resistant. To be on the safe side [Luke] has printed the part in PETG at 100% infill, but in reality the flame front is far enough away that temperature isn’t much of a concern. That said, he does hope to eventually fit these injectors into some kind of combustion chamber, which is where things will start getting toasty.

To be clear this is not a rocket engine, and it produces no appreciable thrust. Turning a big flame into a useful means of propulsion is where things get tricky, almost as though it’s rocket science or something. But that doesn’t mean it can’t be done by suitably ambitious hackers.

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Astra Readies Secretive Silicon Valley Rocket; Firm Exits Stealth Mode, Plans Test Launch

February 28, 2020 by Tom Nardi 27 Comments

After the end of the Second World War the United States and the Soviet Union started working feverishly to perfect the rocket technology that the Germans developed for the V-2 program. This launched the Space Race, which thankfully for everyone involved, ended with boot prints on the Moon instead of craters in Moscow and DC. Since then, global tensions have eased considerably. Today people wait for rocket launches with excitement rather than fear.

That being said, it would be naive to think that the military isn’t still interested in pushing the state-of-the-art forward. Even in times of relative peace, there’s a need for defensive weapons and reconnaissance. Which is exactly why the Defense Advanced Research Projects Agency (DARPA) has been soliciting companies to develop a small and inexpensive launch vehicle that can put lightweight payloads into Earth orbit on very short notice. After all, you never know when a precisely placed spy satellite can make the difference between a simple misunderstanding and all-out nuclear war.

More than 50 companies originally took up DARPA’s “Launch Challenge”, but only a handful made it through to the final selection. Virgin Orbit entered their air-launched booster into the competition, but ended up dropping out of contention to focus on getting ready for commercial operations. Vector Launch entered their sleek 12 meter long rocket into the competition, but despite a successful sub-orbital test flight of the booster, the company ended up going bankrupt at the end of 2019. In the end, the field was whittled down to just a single competitor: a relatively unknown Silicon Valley company named Astra.

Should the company accomplish all of the goals outlined by DARPA, including launching two rockets in quick succession from different launch pads, Astra stands to win a total of $12 million; money which will no doubt help the company get their booster ready to enter commercial service. Rumored to be one of the cheapest orbital rockets ever built and small enough to fit inside of a shipping container, it should prove to be an interesting addition to the highly competitive “smallsat” launcher market.

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Mary Sherman Morgan, Rocket Fuel Mixologist

July 2, 2019 by Kristina Panos 52 Comments

In the fall of 1957, it seemed as though the United States’ space program would never get off the ground. The USSR had launched Sputnik in October, and this cemented their place in history as the first nation in space. If that weren’t bad enough, they put Sputnik 2 into orbit a month later.

By Christmas, things looked even worse. The US had twice tried to launch Navy-designed Vanguard rockets, and both were spectacular failures. It was time to use their ace in the hole: the Redstone rocket, a direct descendant of the V-2s designed during WWII. The only problem was the propellant. It would never get the payload into orbit as-is.

The US Army awarded a contract to North American Aviation (NAA) to find a propellant that would do the job. But there was a catch: it was too late to make any changes to the engine’s design, so they had to work with big limitations. Oh, and the Army needed it two days before yesterday.

The Army sent a Colonel to NAA to deliver the contract, and to personally insist that they put their very best man on the job. And they did. What the Army didn’t count on was that NAA’s best man was actually a woman with no college degree.

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Operation Backfire: Witness To The Rocket Age

February 5, 2019 by Tom Nardi 48 Comments

As the prospects for Germany during the Second World War began to look increasingly grim, the Nazi war machine largely pinned their hopes on a number of high-tech “superweapons” they had in development. Ranging from upgraded versions of their already devastatingly effective U-Boats to tanks large enough to rival small ships, the projects ran the gamut from practical to fanciful. After the fall of Berlin there was a mad scramble by the Allied forces to get into what was left of Germany’s secretive development facilities, with each country hoping to recover as much of this revolutionary technology for themselves as possible.

One of the most coveted prizes was the Aggregat 4 (A4) rocket. Better known to the Allies as the V-2, it was the world’s first liquid fueled guided ballistic missile and the first man-made object to reach space. Most of this technology, and a large number of the engineers who designed it, ended up in the hands of the United States as part of Operation Paperclip. This influx of practical rocketry experience helped kick start the US space program, and its influence could be seen all the way up to the Apollo program. The Soviet Union also captured V-2 hardware and production facilities, which subsequently influenced the design of their early rocket designs as well. In many ways, the V-2 rocket was the spark that started the Space Race between the two countries.

With the United States and Soviet Union taking the majority of V-2 hardware and personnel, little was left for the British. Accordingly their program, known as Operation Backfire, ended up being much smaller in scope. Rather than trying to bring V-2 hardware back to Britain, they decided to learn as much as they could about it in Germany from the men who used it in combat. This study of the rocket and the soldiers who operated it remains the most detailed account of how the weapon functioned, and provides a fascinating look at the incredible effort Germany was willing to expend for just one of their “superweapons”.

In addition to a five volume written report on the V-2 rocket, the British Army Kinematograph Service produced “The German A.4 Rocket”, a 40 minute film which shows how a V-2 was assembled, transported, and ultimately launched. Though they are operating under the direction of the British government, the German soldiers appear in the film wearing their own uniforms, which gives the documentary a surreal feeling. It could easily be mistaken for actual wartime footage, but these rockets weren’t aimed at London. They were being fired to serve as a historical record of the birth of modern rocketry.

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The German Space Program That Never Was

December 4, 2017 by Tom Nardi 89 Comments

A previous post discussed the creation of the V-2 rocket, the first man-made object to reach space. Designed and built at the Peenemünde Army Research Center during World War II, the V-2 was intended to be a weapon of mass destruction, but ended up being far more effective as a tool of discovery than it ever did on the battlefield. In fact, historians now estimate that more people died during the development and construction of the V-2 than did in the actual attacks carried out with it. But even though it failed to win the war for Germany, it still managed to change the world in another way: as it served as the basic blueprint for all subsequent rockets right up to modern-day vehicles.

But the V-2 wasn’t the only rocket-powered vehicle that the Germans were working on, a whole series of follow-up vehicles were in the design phase when the Allies took Berlin in 1945. Some were weapons, but not all. Pioneers like Walter Dornberger and Wernher von Braun saw that rocketry had more to offer mankind than a new way to deliver warheads to the enemy, and the team at Peenemünde had begun laying the groundwork for a series of rockets that could have put mankind into space years before the Soviets.

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Books You Should Read: V-2 By Walter Dornberger

November 3, 2017 by Tom Nardi 63 Comments

In an era where we can watch rockets land on their tails Buck Rogers-style live on YouTube, it’s difficult to imagine a time when even the most basic concepts of rocketry were hotly debated. At the time, many argued that the very concept of a liquid fueled rocket was impossible, and that any work towards designing practical rocket powered vehicles was a waste of time and money. Manned spacecraft, satellite communications, to say nothing of landing on other worlds; all considered nothing more than entertainment for children or particularly fanciful adults.

Walter Dornberger (Bundesarchiv, Bild 146-1980-009-33 / CC-BY-SA 3.0)

This is the world in which V-2, written by the head of the German rocket development program Walter Dornberger, takes place. The entire history of the A-4/V-2 rocket program is laid out in this book, from the very early days when Dornberger and his team were launching rockets with little more than matches, all the way up to Germany’s frantic attempts to mobilize the still incomplete V-2 rocket in face of increasingly certain defeat at the end of World War II.

For those fascinated with early space exploration and the development of the V-2 rocket like myself, this book is essentially unparalleled. It’s written completely in the first person, through Dornberger’s own eyes, and reads in most places like a personal tour of his rocket development site at the Peenemünde Army Research Center. Dornberger walks through the laboratories and factories of Peenemünde, describing the research being done and the engineers at work in a personal detail that you simply don’t get anywhere else.

But this book is not only a personal account of how the world’s first man-made object to reach space was created, it’s also a realistic case study of how engineers and the management that pays the bills often clash with disastrous results. Dornberger and his team wanted to create a vehicle to someday allow man to reach space, while the Nazi government had a much more nefarious and immediate goal. But this isn’t a book about the war — the only battles you’ll read about in V-2 take place in meeting rooms, where the engineers who understood the immense difficulty of their task tried in vain to explain why the timetables and production numbers the German military wanted simply couldn’t be met.

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