Throttle Your Solid Rocket Motors With This One Simple Trick!

For decades, mankind was content to launch payloads into orbit and then watch hundreds of thousands of hours of blood sweat and tears just crash into the ocean. Then, partially because of huge advancements in being able to throttle rocket engines, we started landing our first stage boosters. [Joe] over at the BPS.space YouTube channel is tired of watching SpaceX have all the booster landing fun, but he’s not quite at the throttled liquid engine stage yet. So in the video below the break he asked the question: Can you throttle solid rocket motors? Yes. No. Sort of.

Throttling liquid rocket engines is actually not that different from throttling any other engine- by limiting the amount of fuel and oxidizer. This is challenging all on its own because well… it’s rocket science. With liquid rocket engines though, the concept is at least straightforward. But model rocketry hobbyists only use liquid fueled engines on the extreme high end. The vast majority instead use solid fueled rockets where the fuel is pre-mixed and isn’t variable at all.

These obvious hurdles didn’t stop [Joe] from trying. And trying again. Then, again. And once more for good measure. And then again for repeatability. There are definitely some failures along the way, and we applaud [Joe] for even admitting that he didn’t know how to use a drill properly. Hackers of any age can relate to the time when the didn’t know how to do something, although we also tend to not talk about that part too much.

We won’t spoil the ending except to say that the video is definitely worth a watch to see how [Joe] essentially solves the problem of limiting the effective thrust of a solid rocket engine without actually throttling the engine, and learns about a new issue he’d never seen before.

Of course you can also make rocket engines at home out of a plethora of ingredients, just be sure to do it in somebody else’s kitchen!

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Spacing Out: Telescopes, Politics, And Spacecraft Design

Let’s launch into a round-up of stories that are out of this world, as we take a look at what’s happening in the realm of space exploration.

Ten Billion Dollars For A Telescope? Don’t Drop It!

Perhaps the most highly anticipated space mission of the moment is the James Webb Space Telescope, an infra-red telescope that will be placed in an orbit around the Earth-Sun L2 Lagrange point from which it will serve as the successor to the now long-in-the-tooth Hubble telescope. After many years of development the craft has been assembled and shipped to French Guiana for a scheduled Ariane 5 launch on the 22nd of December. We can only imagine what must have gone through the minds of the engineers and technicians working on the telescope when an unplanned release of a clamp band securing it to the launch vehicle adapter sent a vibration throughout the craft. Given the fragility of some of its components this could have jeopardised the mission, however after inspection it was found that no damage had occurred and that space-watchers and astronomers alike can breathe easy.

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Image of detonation engine firing

Japanese Rocket Engine Explodes: Continuously And On Purpose

Liquid-fuelled rocket engine design has largely followed a simple template since the development of the German V-2 rocket in the middle of World War 2. Propellant and oxidizer are mixed in a combustion chamber, creating a mixture of hot gases at high pressure that very much wish to leave out the back of the rocket, generating thrust.

However, the Japan Aerospace Exploration Agency (JAXA) has recently completed a successful test of a different type of rocket, known as a rotating detonation engine. The engine relies on an entirely different method of combustion, with the aim to produce more thrust from less fuel. We’ll dive into how it works, and how the Japanese test bodes for the future of this technology.

Deflagration vs. Detonation

Humans love combusting fuels in order to do useful work. Thus far in our history, whether we look at steam engines, gasoline engines, or even rocket engines, all these technologies have had one thing in common: they all rely on fuel that burns in a deflagration. It’s the easily controlled manner of slow combustion that we’re all familiar with since we started sitting around campfires. Continue reading “Japanese Rocket Engine Explodes: Continuously And On Purpose”

So How Does A Rocket Fly Sideways, Anyway?

It’s often said that getting into orbit is less about going up, and more about going sideways very fast. So in that sense, the recent launch conducted by aerospace startup Astra could be seen as the vehicle simply getting the order of operations wrong. Instead of going up and then burning towards the horizon, it made an exceptionally unusual sideways flight before finally moving skyward.

As you might expect, the booster didn’t make it to orbit. But not for lack of trying. In fact, that the 11.6 meter (38 feet) vehicle was able to navigate through its unprecedented lateral maneuver and largely correct its flight-path is a testament to the engineering prowess of the team at the Alameda, California based company. It’s worth noting that it was the ground controller’s decision to cut the rocket’s engines once it had flown high and far enough away to not endanger anyone on the ground that ultimately ended the flight; the booster itself was still fighting to reach space until the very last moment.

Astra’s rocket on the launch pad.

There’s a certain irony to the fact that this flight, the third Astra has attempted since their founding in 2016, was the first to be live streamed to YouTube. Had the company not pulled back their usual veil of secrecy, we likely wouldn’t have such glorious high-resolution footage of what will forever be remembered as one of the most bizarre rocket mishaps in history. The surreal image of the rocket smoothly sliding out of frame as if it was trying to avoid the camera’s gaze has already become a meme online, arguably reaching a larger and more diverse audience than would have resulted from a successful launch. As they say, there’s no such thing as bad press.

Naturally, the viral clip has spurred some questions. You don’t have to be a space expert to know that the pointy end of the rocket is usually supposed to go up, but considering how smooth the maneuver looks, some have even wondered if it wasn’t somehow intentional. With so much attention on this unusual event, it seems like the perfect time to take a close look at how Astra’s latest rocket launch went, quite literally, sideways.

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Virgin Galactic’s Long Road To Commercial Spaceflight

To hear founder Richard Branson tell it, the first operational flight of Virgin Galactic’s SpaceShipTwo has been 18 months out since at least 2008. But a series of delays, technical glitches, and several tragic accidents have continually pushed the date back to the point that many have wondered if it will ever happen at all. The company’s glacial pace has only been made more obvious when compared with their rivals in the commercial spaceflight field such as SpaceX and Blue Origin, which have made incredible leaps in bounds in the last decade.

Richard Branson watching Unity’s test flight.

But now, at long last, it seems like Branson’s suborbital spaceplane might finally start generating some income for the fledgling company. Their recent successful test flight, while technically the company’s third to reach space, represents an important milestone on the road to commercial service. Not only did it prove that changes made to Virgin Space Ship (VSS) Unity in response to issues identified during last year’s aborted flight were successful, but it was the first full duration mission to fly from Spaceport America, the company’s new operational base in New Mexico.

The data collected from this flight, which took pilots Frederick “CJ” Sturckow and Dave Mackay to an altitude of 89.23 kilometers (55.45 miles), will be thoroughly reviewed by the Federal Aviation Administration as part of the process to get the vehicle licensed for commercial service. The next flight will have four Virgin Galactic employees join the pilots, to test the craft’s performance when loaded with passengers. Finally, Branson himself will ride to the edge of space on Unity’s final test flight as a public demonstration of his faith in the vehicle.

If all goes according to plan, the whole process should be wrapped up before the end of the year. At that point, between the government contracts Virgin Galactic has secured for testing equipment and training astronauts in a weightless environment, and the backlog of more than 600 paying passengers, the company should be bringing in millions of dollars in revenue with each flight.

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Space Propulsion: Separating Fact From Science Fiction

An unfortunate property of science-fiction is that it is, tragically, fiction. Instead of soaring between the stars and countless galaxies out there, we find ourselves hitherto confined to this planet we call Earth. Only a handful of human beings have ever made it as far as the Earth’s solitary moon, and just two of our unmanned probes have made it out of the Earth’s solar system after many decades of travel. It’s enough to make one despair that we’ll never get anywhere near the fantastic future that was seemingly promised to us by science-fiction.

Yet perhaps not all hope is lost. Over the past decades, we have improved our chemical rockets, are experimenting with various types of nuclear rockets, and ion thrusters are a common feature on modern satellites as well as for missions within the solar system. And even if the hype around the EMDrive vanished as quickly as it had appeared, the Alcubierre faster-than-light drive is still a tantalizing possibility after many years of refinements.

Even as physics conspires against our desire for a life among the stars, what do our current chances look like? Let’s have a look at the propulsion methods which we have today, and what we can look forward to with varying degrees of certainty.

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3D Printed Vortex Cooled Rocket Needs To Stop Leaking

Rocket engines are known for one thing above all else, and that’s getting hot. It’s this very property that makes them such a challenge to build and run from a materials engineering standpoint. It’s hard enough to build one with advanced metal alloys, but [Integza] presses on with trying to make one on a 3D printer. Progress is being made, but success remains elusive.  (Video, embedded below.)

To try and mitigate the thermal effects of burning propellants in his engine design, [Integza] looked to vortex cooling. This is where oxygen is swirled around the outer edge of the combustion chamber in a vortex, acting as a buffer layer between the burning fuel and the chamber walls. With 3D printed chamber components, keeping temperatures as low as possible is key, after all. Unfortunately, despite using a special ceramic-laden resin for printing and lathering the rocket components in various refractory materials, it wasn’t possible to stop the chambers leaking. Solid combustion was possible for a few seconds at a time, but eventually each motor tested turned into a ball of flames as the walls broke down.

Thankfully, nobody was hurt in testing, and [Integza] has a clear idea of the problems that need to be fixed in the next iteration. We’ve featured other vortex cooled rockets before – the theory is sound. As always, the devil is in the implementation.

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