This is What an Air-Breathing Electric Thruster’s Intake Would Look Like

Like all other technologies, satellite technology has grown in leaps and bounds in the past couple decades. Satellites can monitor Earth in increasingly high resolutions, aiding everything from storm forecasting, to climate change monitoring, to predicting crop harvests. But there’s one thing still holding satellites back: altitude.

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X-37B Lands After 780 Days in Orbit Doing ???

The X-37B, the US Air Force’s experimental, Orbital Test Vehicle (OTV) has come back down to Earth after 780 days. It landed at the Kennedy Space Center Shuttle Landing Facility on Oct. 27, 2019, at 3:51 a.m. after breaking its own record for time in space. The X-37B has now spent 2,865 total days in orbit.

The question is, what’s it doing up there?

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NASA Has a New, All-Electric Airplane

Currently, commercial air travel accounts for 4 to 9% of the anthropogenic greenhouse gases that contribute to climate change. What’s worse, airplane emissions are on the rise thanks to rising populations and the increasingly globalized nature of our economy. Hence why NASA has been pursuing the development of electric aircraft these past few decades.

Much like reusable spacecraft and infrastructure, electric aircraft are part of NASA’s pursuit to make aerospace cheaper, more efficient and less harmful to the environment. Their efforts bore fruit in the form of the X-57 Maxwell – the first all-electric experimental aircraft – which was recently delivered to the NASA Armstrong Flight Research Center (AFRC) in Edwards, California.

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Airplane Contrails are Contributing to Global Warming Too

To the scientifically uninitiated, it might seem like a frivolous idea: That those slight, wispy clouds that trail behind jet aircraft at such high altitudes could contribute to climate change. But they do.

Scientists love to measure things, and when they measured these contrails, which is short for condensation trails, they found bad news. Though they look kind of beautiful and ephemeral on a summer day, they pack an oversize punch when it comes to their warming effect.

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Progress for the Skylon. Europe agrees to continue working on the air-breathing SABRE engine

When it comes to the future of space exploration, the name of the game is “save money”. To do this, space agencies and aerospace companies around the world are investing in things like reusable rockets, single-stage-to-orbit (SSTO) rockets, and reusable space planes. This last concept builds on the tradition established by the Space Shuttle and Buran spacecraft, two reusable vehicles designed to make space launches more affordable.

The one drawback of these spacecraft was the fact that it still took two rocket boosters and a huge external fuel tank to put them into orbit. This is where the Synergetic Air Breathing Rocket Engine (SABRE) comes into play. With the help of the European Space Agency (ESA) and the UK Space Agency (UKSA), this revolutionary hypersonic engine recently took a big step towards fruition.

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This is an Actual Photograph of the Shock Waves from Supersonic Jets Interacting with Each Other

Schlieren photography images of two supersonic jets and their soundwaves. Image Credit: NASA

After more than 10 years of hard work, NASA has reached another milestone. We’re accustomed to NASA reaching milestones, but this one’s a little different. This one’s all about a type of photography that captures images of the flow of fluids.

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Musk Says that SpaceX will use a Giant Party Balloon to Bring an Upper Stage Back. Wait, what?

When Elon Musk of SpaceX tweets something interesting, it generates a wave of excitement. So when he tweeted recently that SpaceX might be working on a way to retrieve upper stages of their rockets, it set off a chain of intrigued responses.

SpaceX has been retrieving and reusing their lower stages for some time now, and it’s lowered the cost of launching payloads into space. But this is the first hint that they may try to do the same with upper stages.

Twitter responders wanted to know exactly what SpaceX has in mind, and what a “giant party balloon” might be. Musk hasn’t elaborated yet, but one of his Twitter followers had something interesting to add.

Quinn Kupec, a student at the University of Maryland’s James Clark School of Engineering tweeted to Musk:

Universe Today contacted Mr. Kupec to see if he could help us understand what Musk may have been getting at. But first, a little background.

An “ultra low ballistic entry coefficient decelerator” is a bit of a mouthful. The ballistic coefficient measures how well a vehicle can overcome air resistance in flight. A high ballistic coefficient means a re-entry vehicle would not lose velocity quickly, and would reach Earth at high speeds. An ultra low ballistic entry coefficient decelerator would lose speed quickly, meaning that a vehicle would be travelling at low, subsonic speeds before reaching the ground.

To recover an upper stage booster, low speeds are desirable, since they generate less heat. But according to Kupec, there’s another problem that must be overcome.

“What happens when these things slow down to landing velocities? If your center of gravity is offset significantly behind your center of drag, as would be the case with a returning upper stage, it can get unstable. If the center of gravity of the re-entry vehicle is too high, it can become inverted, which is obviously not desirable.”

So the trick is to lower the speed of the re-entry vehicle to the point where the heat generated by reentry isn’t damaging the booster, and to do it without causing the vehicle to invert or otherwise become unstable. This isn’t a problem for the main stage boosters that SpaceX now routinely recovers; they have their own retro-rockets to guide their descent and landing. But for the upper stage boosters, which reach orbital velocities, it’s an obstacle that has to be overcome.

“My research is specifically focused on how high you can push the center of gravity and still maintain the proper flight configuration,” said Kupec.

But what about the “giant party balloon” that Musk tweeted about?

Musk could be referring, in colorful terms, to what’s called a ballute. The word is a combination of the words balloon and parachute. They were invented in the 1950’s by Goodyear Aerospace. They can arrest the descent of entry vehicles and provide stability during the descent.

“…the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric…” – Professor Dave Akin, University of Maryland

Universe Today contacted Professor Dave Akin of the University of Maryland for some insight into Musk’s tweet. Professor Akin has been working on reentry systems for over 2 decades.

In an e-mail exchange, Professor Akin told us, “There have been concepts proposed for deploying a large balloon on a cable that is towed behind you on entry. The balloon lowers your ballistic coefficient, which means you decelerate higher in the atmosphere and the heat load is less.” So the key is to scrub your speed before you get closer to Earth, where the atmosphere is thicker and generates more heat.

But according to Professor Akin, this won’t necessarily be easy to do. “To get the two orders of magnitude reduction in ballistic coefficient that Elon has been talking about the balloon would have to be 120 ft. in diameter, and made of a high-temperature fabric, so it’s not going to be all that easy.”

But Musk’s track record shows he doesn’t shy away from things that aren’t easy.

Retrieving upper rocket stages isn’t all about lowering launch costs, it’s also about space junk. The European Space Agency estimates that there are over 29,000 pieces of space junk orbiting Earth, and some of that junk is spent upper stage boosters. There have been some collisions and accidents already, with some satellites being pushed into different orbits. In 2009, the Iridium 33 communications satellite and the defunct Russian Cosmos 2251 communications satellite collided with each other, destroying both. If SpaceX can develop a way to retrieve its upper stage boosters, that means less space junk, and fewer potential collisions.

There’s a clear precedent for using balloons to manage reentry. With people like Professor Akin and Quinn Kupec working on it, SpaceX won’t have to reinvent the wheel. But they’ll still have a lot of work to do.

Musk tweeted one other thing shortly after his “giant party balloon” tweet:

No word yet on what that might mean.

Elon Musk’s “giant party balloon” tweet: https://twitter.com/elonmusk/status/985655249745592320
Quinn Kupec’s tweet: https://twitter.com/QuinnKupec/status/985736260827471872