SLA 3D Printed Vortex Cooled Rocket Engine

December 8, 2020 by Danie Conradie 16 Comments

3D printing is an incredible tool for prototyping and development, but the properties of the materials can be a limiting factor for functional parts. [Sam Rogers] and colleagues at [AX Technologies] have been testing and developing a small liquid-fueled rocket engine and successfully used vortex cooling to protect a resin 3D printed combustion chamber. (Video, embedded below.)

Vortex cooling works by injecting oxygen into the combustion chamber tangentially, just inside the nozzle of the engine, which creates a cooling, swirling vortex boundary layer along the chamber wall. The oxygen moves to the front end of the combustion chamber where it mixes with the fuel and ignites in the center. This does not protect the nozzle itself, which only lasts a few seconds before becoming unusable. However, thanks to the modular design of the test engine, only the small nozzle section had to be reprinted for every test. While this part could be manufactured using a metal 3D printer, the costs are still very high, especially at this experimental stage. The clear resin parts also allow the combustion observed and more accurate conclusions to be drawn from every test.

This engine intended to be used as a torch igniter for a much larger rocket engine. Fuel is injected into the front of the combustion chamber, where a spark plug is located to ignite the oxygen-fuel mixture. The flow of the oxygen and fuel is controlled by two servo-operated valves connected to a microcontroller, which is mounted with the engine on linear rails. This allows the test engine to move freely, and push against a load cell to measure thrust. The spark is created before the valves are opened to prevent a delayed ignition, which can blow up the engine, and getting the valve sequence and timing correct is critical. Many iterations and destroyed parts later, the [AX Technologies] team achieved successful ignition, with a clear supersonic Mach diamond pattern in the exhaust.

This is just one more example of 3D printing and cheap electronics allowing impressive progress on a limited budget. Another example is [Joe Barnard]’s progress in getting a model rocket to land itself with a solid fuel engine. Companies and organisations have been using 3D printed components in rocket engines for a few years now, and we’ve even seen an open source version.

Crossed Wires Crash Rockets

December 3, 2020 by Tom Nardi 69 Comments

On November 17th, a Vega rocket lifted off from French Guiana with its payload of two Earth observation satellites. The booster, coincidentally the 17th Vega to fly, performed perfectly: the solid-propellant rocket engines that make up its first three stages burned in succession. But soon after the fourth stage of the Vega ignited its liquid-fueled RD-843 engine, it became clear that something was very wrong. While telemetry showed the engine was operating as expected, the vehicle’s trajectory and acceleration started to deviate from the expected values.

There was no dramatic moment that would have indicated to the casual observer that the booster had failed. But by the time the mission clock had hit twelve minutes, there was no denying that the vehicle wasn’t going to make its intended orbit. While the live stream hosts continued extolling the virtues of the Vega rocket and the scientific payloads it carried, the screens behind them showed that the mission was doomed.

Displays behind the hosts clearly showed Vega wasn’t following the planned trajectory.

Unfortunately, there’s little room for error when it comes to spaceflight. Despite reaching a peak altitude of roughly 250 kilometers (155 miles), the Vega’s Attitude Vernier Upper Module (AVUM) failed to maintain the velocity and heading necessary to achieve orbit. Eventually the AVUM and the two satellites it carried came crashing back down to Earth, reportedly impacting an uninhabited area not far from where the third stage was expected to fall.

Although we’ve gotten a lot better at it, getting to space remains exceptionally difficult. It’s an inescapable reality that rockets will occasionally fail and their payloads will be lost. Yet the fact that Vega has had two failures in as many years is somewhat troubling, especially since the booster has only flown 17 missions so far. A success rate of 88% isn’t terrible, but it’s certainly on the lower end of the spectrum. For comparison, boosters such as the Soyuz, Falcon 9, and Atlas have success rates of 95% or higher.

Further failures could erode customer trust in the relatively new rocket, which has only been flying since 2012 and is facing stiff competition from commercial launch providers. If Vega is to become the European workhorse that operator Arianespace hopes, figuring out what went wrong on this launch and making sure it never happens again is of the utmost importance.

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Spacing Out: Rocks From The Moon, Rocks From Mars, A Near Miss, And Some Interesting Launches

December 1, 2020 by Jenny List 4 Comments

Sure, the SpaceX crew made it safely to the ISS, but there’s plenty happening beyond just that particular horizon. The Chinese National Space Administration have launched their Chang’e 5 mission to collect and return lunar rock samples, a collaboration between NASA and ESA to do the same with samples from Mars has passed its review, and a pair of satellites came uncomfortably close to each other in a near-miss that could have had significant orbital debris consequences. It’s time for Spacing Out!

Bringing Alien Rocks to Earth

The Chang'e 5 mission on the launch pad. China News Service, CC BY 3.0. — The Chang’e 5 mission on the launch pad. China News Service, CC BY 3.0.

Ever since the NASA and Soviet lunar launches at the height of the Space Race, there have been no new missions to collect material from the Lunar surface and return it to Earth. That changed last week.

The Chang’e 5 mission launched in China on November 23rd will deliver moon rocks to earth, and as this is being written it has already entered Lunar orbit and separated into its constituent parts in preparation for landing. It’s a four-craft mission, with a lunar lander and ascent module going to the surface, and a service module and Earth return craft remaining in orbit to receive the samples and send them back to the planet for re-entry and retrieval. The hurdles facing the mission scientists and engineers are immense, and a safe sample return in mid-December will be an extremely impressive achievement.

Happily Chang’e 5 even has a hacker angle, as its telemetry has offered a bonanza to satellite-watchers who have turned their dishes skyward to capture the event. Daniel Estévez EA4GPZ has posted a collected analysis of data telemetry work by a variety of people worldwide, but the eye-candy prize goes to r00t.cz, who has successfully decoded image stream data to the extent that they have assembled a fragment of video captured from the craft during its journey.

Not to be outdone in the field of ambitious sample return missions, NASA and ESA’s joint plan to collect and return rock core samples from Mars has met with the approval of the independent review board set up to examine it. This will involve multiple craft from both agencies, with NASA’s already launched Perseverance rover collecting and containing the samples before leaving them on the surface for eventual collection by a future ESA rover. This will then pass them to a NASA ascent craft which will take them to Martian orbit and rendezvous with an ESA craft that will return them to Earth. We space-watchers are in for an exciting decade.

That Was a Close One!

Anyone who has seen the film Gravity will be familiar with the Kessler syndrome, in which collisions between spacecraft and or debris could create a chain reaction of further collisions and render entire orbital spheres unusable to future craft because of the collision hazard presented by the resulting cloud of space debris. Because of this, spacecraft operators devote considerable resources towards avoiding such collisions, and it is not uncommon for slight orbital adjustments to be made to avoid proximity with other orbiting man-made objects.

On the 27th of November it seems that these efforts failed, with a terse announcement from Roscosmos of a near-miss between their Kanopus-V craft and the Indian CARTOSAT 2F. The two remote-imaging satellites passed as close as 224 metres from each other, which in space terms given their likely closing speeds would have been significantly too close for comfort. The announcement appears worded to suggest that the Indian craft was at fault, however it’s probably a fairer conclusion that both space agencies should have seen the other’s satellite coming. Fortunately we escaped a catastrophe this time, but it is to be hoped that all operators of such satellites will take note.

RocketLab Joins the Reusable Booster Club

Other recent launches that might excite the interest of readers are the New Zealand-based RocketLab launching their Electron rocket with 30 small satellites on board before for the first time retrieving their booster stage, and the Japanese Mitsubish Electric sending their JDRS-1 satellite to geosynchronous orbit. This last craft is of interest because it carries an optical data link rather than the more usual RF, and could prove the technology for future launches.

The coming weeks should be full of news from China on Chang’e 5’s progress. Getting a craft to the moon and returning it will be a huge achievement, and we hope nothing fails and we’ll see pictures of the first new Moon rocks on Earth since the 1970s. We don’t know how to say “Good luck and a successful mission!” in Chinese, so we’ll say it in English.

So Close To Landing A Model Rocket On Its Tail

November 27, 2020 by Danie Conradie 44 Comments

We’ve become so used to seeing SpaceX boosters land themselves back on the pad with clockwork reliability, that it’s easy to forget it took them a good number of attempts to get right. Inspired by SpaceX’s work, [Joe Barnard] of [BPS.Space] started working to replicate it at the model scale five years ago, with no engineering education or experience. On the latest attempt with a brand-new thrust vectoring Scout E rocket, he has gotten tantalizingly close to doing a controlled propulsive landing with a solid-fuel rocket motor.

We’ve all been thrilled to see the SpaceX rockets return to earth, landing elegantly on a floating pad. But those are liquid-fueled. The trick with a solid-fuel rocket motor is it can’t be throttled directly, which is a challenge when you need precision control to land. Thanks to [Joe]’s custom AVA flight computer and the remarkably consistent thrust curve of the Estes F15 black powder motors he used, it becomes a matter of igniting the descent motor at the right moment to make the vertical velocity zero at touchdown. However, [Joe] found that the time between sending the ignition signal and when peak thrust is reached was inconsistent, so he had to work around that. He did this by controlling how much of the thrust is spent in the vertical direction, by vectoring the motor side to side to spend some trust horizontally.

View from rocket of the ascent motor falling away immediately after being ejected

In this attempt, the rocket tipped over on landing due to excessive horizontal movement at touchdown. Joe tracked the cause down to a weak GPS signal caused by antenna position and a possible bug in the Kalman filter that fuses all the sensor data for position and velocity estimation. Thanks to incredibly detailed telemetry and logging done by the flight computer, data from every launch are used for future improvements. We are looking forward to the next flight in a few weeks, during which [Joe] plans to tune and test the control software, among other minor improvements.

Almost every single part of this rocket is a display of engineering ingenuity. The landing struts are designed to absorb as much impact as possible without bouncing while being light and quick to deploy. The ascent motor is ejected simply by moving the thrust vectoring mount to one of its extremes, allowing the descent motor to drop into place. The rocket also features a complete emergency abort system with a parachute, which can be activated manually, or by the flight computer if it calculates that landing isn’t feasible. We already covered [Joe]’s latest launch pad, which is a very interesting project all by itself.

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The Wow! Signal And The Search For Extraterrestrial Intelligence

November 25, 2020 by Dan Maloney 54 Comments

On a balmy August evening in 1977, an enormous radio telescope in a field in the middle of Ohio sat silently listening to the radio universe. Shortly after 10:00 PM, the Earth’s rotation slewed the telescope through a powerful radio signal whose passage was noted only by the slight change in tone in the song sung every twelve seconds by the line printer recording that evening’s data.

When the data was analyzed later, an astronomer’s marginal exclamation of the extraordinarily powerful but vanishingly brief blip would give the signal its forever name: the Wow! Signal. How we came to hear this signal, what it could possibly mean, and where it might have come from are all interesting details of an event that left a mystery in its wake, one that citizen scientists are now looking into with a fresh perspective. If it was sent from a region of space with habitable planets, it’s at least worth a listen.

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The Cost Of Moving Atoms In Space; Unpacking The Dubious Claims Of A $10 Quintillion Space Asteroid

November 23, 2020 by Bob Baddeley 43 Comments

The rest of the media were reporting on an asteroid named 16 Psyche last month worth $10 quintillion. Oddly enough they reported in July 2019 and again in February 2018 that the same asteroid was worth $700 quintillion, so it seems the space rock market is similar to cryptocurrency in its wild speculation. Those numbers are ridiculous, but it had us thinking about the economies of space transportation, and what atoms are worth based on where they are. Let’s break down how gravity wells, distance, and arbitrage work to figure out how much of this $10-$700 quintillion we can leverage for ourselves.

The value assigned to everything has to do with where a thing is, AND how much someone needs that thing to be somewhere else. If they need it in a different place, someone must pay for the transportation of it.

In international (and interplanetary) trade, this is where Incoterms come in. These are the terms used to describe who pays for and has responsibility for the goods between where they are and where they need to be. In this case, all those materials are sitting on an asteroid, and someone has to pay for all the transport and insurance and duties. Note that on the asteroid these materials need to be mined and refined as well; they’re not just sitting in a box on some space dock. On the other end of the spectrum, order something from Amazon and it’s Amazon that takes care of everything until it’s dropped on your doorstep. The buyer is paying for shipping either way; it’s just a matter of whether that cost is built into the price or handled separately. Another important term is arbitrage, which is the practice of taking a thing from one market and selling it in a different market at a higher price. In this case the two markets are Earth and space.

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The Battle For Arecibo Has Been Lost

November 19, 2020 by Tom Nardi 98 Comments

It is with a heavy heart that we must report the National Science Foundation (NSF) has decided to dismantle the Arecibo Observatory. Following the failure of two support cables, engineers have determined the structure is on the verge of collapse and that the necessary repairs would be too expensive and dangerous to conduct. At the same time, allowing the structure to collapse on its own would endanger nearby facilities and surely destroy the valuable research equipment suspended high above the 300 meter dish. Through controlled demolition, the NSF hopes to preserve as much of the facility and its hardware as possible.

When the first support cable broke free back in August, we worried about what it meant for the future of this unique astronomical observatory. Brought online in 1963 as part of a Cold War project to study how ICBMs behaved in Earth’s upper atmosphere, the massive radio telescope is unique in that it has the ability to transmit as well as receive. This capability has been used to produce radar maps of distant celestial objects and detect potentially hazardous near-Earth asteroids.

In 1974, it was even used to broadcast the goodwill of humankind to any intelligent lifeforms that might be listening. Known as the “Arecibo Message”, the transmission can be decoded to reveal an assortment of pictograms that convey everything from the atomic numbers of common elements to the shape of the human body. The final icon in the series was a simple diagram of Arecibo itself, so that anyone who intercepted the message would have an idea of how such a relatively primitive species had managed to reach out and touch the stars.

There is no replacement for the Arecibo Observatory, nor is there likely to be one in the near future. The Five hundred meter Aperture Spherical Telescope (FAST) in China is larger than Arecibo, but doesn’t have the crucial transmission capability. The Goldstone Deep Space Communications Complex in California can transmit, but as it’s primarily concerned with communicating with distant spacecraft, there’s little free time to engage in scientific observations. Even when it’s available for research, the largest dish in the Goldstone array is only 1/4 the diameter of the reflector at Arecibo.

Just last week we wondered aloud whether a nearly 60 year old radio telescope was still worth saving given the incredible advancements in technology that have been made in the intervening years. Now, unfortunately, we have our answer.