Japan Successfully Tests Possible Deep-Space Rocket Technology (futurism.com) 40
Futurism reports:
Japan's space agency JAXA has announced that is has successfully demonstrated the operation of a "rotary detonation engine" in space, a world's first.
Such an engine uses a series of controlled explosions that travel around a circular channel at its base. The result is a massive amount of thrust coming from a much smaller engine using significantly less fuel — a potential game changer for deep space exploration, according to JAXA. It's a lucrative endeavor and Japan isn't the only country pursuing the idea. Researchers across the U.S. are testing out the technology to make rockets both lighter and more environmentally friendly...
"We will aim to put the technology into practical use in about five years,"Jiro Kasahara, a Nagoya University professor who is working on the technology with JAXA, told the Japan Times last month.
Ars Technica reports that detonation engines should theoretically weigh less than traditional rocket engines &mdash and that JAXA "plans to use data from this test for potential development of detonation engines for kick stages as well as first- and second-stage rocket engines."
Futurism adds that in the same flight JAXA also successfully tested a second "pulse detonation engine."
Such an engine uses a series of controlled explosions that travel around a circular channel at its base. The result is a massive amount of thrust coming from a much smaller engine using significantly less fuel — a potential game changer for deep space exploration, according to JAXA. It's a lucrative endeavor and Japan isn't the only country pursuing the idea. Researchers across the U.S. are testing out the technology to make rockets both lighter and more environmentally friendly...
"We will aim to put the technology into practical use in about five years,"Jiro Kasahara, a Nagoya University professor who is working on the technology with JAXA, told the Japan Times last month.
Ars Technica reports that detonation engines should theoretically weigh less than traditional rocket engines &mdash and that JAXA "plans to use data from this test for potential development of detonation engines for kick stages as well as first- and second-stage rocket engines."
Futurism adds that in the same flight JAXA also successfully tested a second "pulse detonation engine."
Does this change the rocket equasion? (Score:1)
Game changer, for real, if so.
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They didn't say much about what they were planning to do for an encore. I'd like to know more about their plans for developing it. All they say is they expect to deploy it commercially in about five years.
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Re:Does this change the rocket equasion? (Score:5, Interesting)
It doesn't change the rocket equation.
In a regular combustion engine the explosion is subsonic. A detonation is supersonic. Since the specific impulse is proportional to the exhaust speed, detonation engines could be a pretty big improvement, up to 25%. Specific impulse is outside the log in the rocket equation, so improving it is a big deal.
Huh? (Score:2)
The exhaust velocity of a conventional rocket is already hypersonic.
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Competitive art used to be in the Olympics.
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It's not about the exhaust velocity, but how fast the leading edge of the flame front moves through the fuel mixture. Which I would think in a normal continuous-flow engine is essentially the speed at which the fuel is entering the combustion chamber. Which is far, far slower than the hot gasses leave.
When the flame front is moving at supersonic speeds you get detonation rather than combustion. I *think* (I'm really getting into the weeds here) it essentially comes down to the fact that when the flame fro
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the actual combustion takes place within a wavefront at much higher heat and pressure than in the surrounding combustion chamber...
... which results in a higher exhaust velocity for a given mass of propellant.
--
--- Most topics have many sides worth arguing, allow me to take one opposite you.
By all means, do. (Nice sig, by the way.)
An old technology. (Score:5, Informative)
What Is A Rotating Detonation Engine - And Why Are They Better Than Regular Engines [youtu.be]
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"Thanks for the link. Why so quick to dismiss the progress, though? The path from idea to working prototypes and adoption has many "firsts", and they're always news for people who care."
Wankel motors are only used by Mazda, I guess they made this Japanese rocket as well. :-)
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"Thanks for the link. Why so quick to dismiss the progress, though? The path from idea to working prototypes and adoption has many "firsts", and they're always news for people who care."
Wankel motors are only used by Mazda, I guess they made this Japanese rocket as well. :-)
The pressure changers from sea level to vacuum will be a challenge for this engine. Where the flame front is will be dependent on air pressure. It will probably be really complex to get that under control. The Delaval Nozzles used on rockets today are subject to the same effects. But over expanded exhaust plumes are just an efficiency hit. If a RDE engine get it's flame front out of sync doe to rapid external pressure changes, the outlook might be not so good.
They'll probably be okay if only used in a va
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The pressure changers from sea level to vacuum will be a challenge for this engine.
(* facepalm *) Which part of deep space did you miss in the summary?
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The pressure changers from sea level to vacuum will be a challenge for this engine. (* facepalm *) Which part of deep space did you miss in the summary?
Did you read the article? Here's what the article states:
Such an engine uses a series of controlled explosions that travel around a circular channel at its base. The result is a massive amount of thrust coming from a much smaller engine using significantly less fuel — a potential game changer for deep space exploration, according to JAXA.
They are touting fuel efficiency - not pressure expansion issues. Of course if you are planning on using a rocket in deep space, fuel efficiency is important. Bu
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Isn't that how most rockets work? Multi stage to orbit, each stage designed for different stages of the flight.
For deep space landing is probably going to be via parachute and small engines similar to how we land on Mars, simply due to the weight requirements of doing a vertical landing like boosters do on earth.
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Yep, Even with the same engine, like Falcon 9's Merlin, the vacuum version has a much larger nozzle, because you achieve the greatest efficiency by dropping the pressure of the exhaust gases as close to ambient pressure as possible. It's also the reason why the Space Shuttle engines were never really achieving their optimum efficiency, having to work as a compromise between low altitude and high altitude thrust. I wonder if it would be possible to devise a variable geometry chamber for a rotary detonation e
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I think they are already using an aerospike design, which is actually ideal for use at a range of altitudes.
The important number. (Score:2)
This type of rocket engine is up to 25% more efficient. They don't say how much of that 25% they were able to achieve but it's far more than 0% if they are calling it a success.
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The engine ran for just 6 seconds and produced only 500 Newtons of thrust. This was basically a small proof of concept test engine. It is too early in development to talk about what real-world efficiency they can expect out of a full-sized prototype.
There are some issues with the rotating detonation engine - but let's pause a second to admit it is one awesome name.
It's a little bit like the old school pulsejet, only continuous. The flame front has to be in a very specific place at a very specific time, lest it interfere with another flame front. Get those in conflict with each other, and it can become a single dramatic detonation engine.
What happens with Rocket engines is that their exhaust is highly affected by altitude - watch a launch, and you'l
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"rotating detonation engine" would also be a perfectly fitting name for a regular internal combustion engine though. :)
Re: The important number. (Score:2)
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Since this rotating detonation engine is probably only used in deep space / vacuum, I wonder what is its efficiency compared to ion engines.
I was curious as well. https://www.nasa.gov/centers/g... [nasa.gov] That page is old, but has some pretty high numbers. lie 85 percent efficiency. Newer engines are looking at higher thrust https://www.nasa.gov/centers/g... [nasa.gov] .
I think that Ion engines look like a good bet after the regular rockets get the rocket near the speed direction they want. Now, say we want to go to Mars. We'll probably need to go back to a regular rocket engine for landing. The Ion Engines can probably work to slow she ship if used cleverly,
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This type of rocket engine is up to 25% more efficient. They don't say how much of that 25% they were able to achieve but it's far more than 0% if they are calling it a success.
There is a lot more than just efficiency though. That engine has to deal with pressures from sea level to space vacuum. The flame front will need extremely tightly controlled. That will be the trick.
Typical rocket engines are pretty forgiving of that. It is actually pretty ancient by technology standards. The basics of modern rocket engines were worked out in the early 1940's by the you know who's.
One of those guys could be transported to today, and would recognized the components immediately. This en
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> That engine has to deal with pressures from sea level to space vacuum
Why? Between Earth's gravity well and atmosphere, single-stage-to-orbit chemical rockets are unlikely to ever make sense. And I don't think I've ever even heard of a deep space probe whose engine ever fired within Earth's atmosphere. They're usually "stage 3+", already in hard vacuum and deployed onto a transfer orbit to their final destination by a full-stack ground-to-orbit rocket before they activate.
Even as a second-stage engin
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> That engine has to deal with pressures from sea level to space vacuum
Why? Between Earth's gravity well and atmosphere, single-stage-to-orbit chemical rockets are unlikely to ever make sense.
Because the rocket has to go from sea level to areas of a lot lower atmospheric pressure. Each stage. Quickly, with the pressure dropping by the second. If you look at the standard DeLaval Bell Rockets, they start out just about the right amount of expansion of the exit flame. Even with the first stage, by the time it gets anywhere near the end of it's job, the exhaust is way over-expanded.
You can see this in how big an area the exhaust plume of a standard first stage gets at the higher altitudes. This
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"Deep space" is basically everything beyond Earth orbit. Arguably including pretty much everything beyond low orbit, or at least beyond the Van Allen radiation belts and the protection of the Earth's magnetosphere.
>Because the rocket has to go from sea level to areas of a lot lower atmospheric pressure. Each stage.
Only one stage is actually firing its engines at a time though, so only its engines have to be able to *function* under those rapidly changing pressures. The rest are just so much inert cargo
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Meaning 25% more payload? I'll take it.
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>They don't say how much of that 25% they were able to achieve but it's far more than 0% if they are calling it a success.
I disagree - creating a stable rotating detonation engine *at all* is a huge challenge, I'm not even 100% sure anyone has done it before. It could be far less efficient than traditional rockets and still be a wild success, just because they managed to do it *at all*. Plenty of time to optimize towards theoretical performance limits once it's working at all.
Now do it with nukes. (Score:2)
Anyone else thinking of Project Orion?
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Slashdot kids-- from the beginning of slashdot-- have shown no signs of knowing who Freeman Dyson is. I kept submitting links to Dyson's New York Review articles, they didn't run a single one of them. Internet nerds know surprisingly little of anything that happened pre-internet.
(Though near the end of his life, there was an Ask Slashdot interview with him.)
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Slashdot kids-- from the beginning of slashdot-- have shown no signs of knowing who Freeman Dyson is.
Of course we know who he is. He's the vacuum cleaner guy, right?
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The original one right? Not the Johnny-come-lately project that stole it's name?
Yeah, did for a moment or two.
&mdash?! IN A STORY? REALLY?! (Score:1)
Fix your shit, Slashdot "editors", fix your shit.
RX-7 (Score:4, Funny)
So could this be like the RX-7 of rockets? :D
Great to hear news of rocketry... (Score:1)
So what's next? (Score:2)
Micro-nukes? A rotary Orion?