Scientists Create a Prototype 'Air Plasma' Engine That Works Without Fossil Fuels (sciencealert.com) 136
According to research published in the journal AIP Advances, scientists have created a prototype jet engine that compresses air and ionizes it with microwaves, generating plasma that thrusts it forward. ScienceAlert reports: There's a long way to go between a proof-of-concept prototype and installing an engine in a real plane. But the prototype was able to launch a one-kilogram (2.2-pound) steel ball 24 millimeters (almost one inch) into the air. That's the same thrust, proportional to scale, as a conventional jet engine. "Our results demonstrated that such a jet engine based on microwave air plasma can be a potentially viable alternative to the conventional fossil fuel jet engine," lead researcher and Wuhan University engineer Jau Tang said in a press release.
What (Score:3)
the prototype was able to launch a one-kilogram (2.2-pound) steel ball 24 millimeters (almost one inch) into the air.
I'll be honest that seems like a really weird test for a jet engine.
Re:What (Score:5, Informative)
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But the prototype was able to launch a one-kilogram (2.2-pound) steel ball 24 millimeters (almost one inch) into the air. That's the same thrust, proportional to scale, as a conventional jet engine.
Yeah, that totally makes sense. Launching 1 kg 24 mm into the air is equivalent to launching a 200 ton aircraft 4800 meters into the air. I (heart) math!
Re:What (Score:5, Insightful)
It did specifically say that it's measuring thrust proportional to scale. Now, the scale part can be a little tricky. Are they scaling by volume or by weight, for example. A jet engine that's the same size and provides the same thrust, but is five times heavier would be a problem. They may just be scaling to the actual area of the aperture. This is pretty neat though. While electric propulsion for large commercial planes still has a number of hurdles, it's a very interesting concept for the future. The power issue is still an issue, but there may be some hope on the horizon there. Aluminum-air batteries may be able to get into the range where they could make long-range electric flight practical. An aluminum air flow battery would be as easy to fill as a conventional aircraft. One of the interesting things to see with this electric jet technology is if it could actually be more efficient than a conventional jet. Also, can it work at higher altitudes (which would add an automatic efficiency bonus)? Could it enable supersonic flight? Could it require less maintenance? Could it be safer? As it is, a bird strike to the engine, or some ash in the air can bring down a commercial jet. Could this kind of jet be able to withstand those conditions? Could it be cheaper to build and/or cheaper to operate? We will obviously have to wait and see.
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I mean.... sure. But couldn't you already do that with a conventional jet engine? Hmm, guess you're right though, a conventional jet engine would make for pretty unhealthy popcorn with all the burned and unburned hydrocarbons. It is possible to run a jet engine on vegetable oil though. Maybe coconut oil?
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Harbour Air has already purchased some electric aircraft for their commuter flights.
https://spectrum.ieee.org/ener... [ieee.org]
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Metric, Imperial, and neither measurements all used in a couple of sentences.
Re:What (Score:4, Informative)
Here's a video of the setup [literatumonline.com].
403 - Forbidden
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too hot to measure with a conventional barometer
And therein lies a problem. The performance and efficiency of an air cycle turbine [wikipedia.org] depends (among other things) on raising the temperature of the air. Given typical turbine topology, a limiting factor is the temperature that the outlet turbine can withstand. Jet fuel (kerosene) combustion is already capable of exceeding the temperature limits of most exotic alloys, requiring some fancy turbine blade cooling schemes.
Not much to see here.. (Score:4, Insightful)
Zero information on input energy versus thrust/power, so in effect meaningless.
Efficiency is pretty much all that counts here, unless it is more efficient that a electrically driven ducted fan or propeller arrangement, then it is of little interest.
In fact, it is probably rather insightful that they do not appear to have mentioned that... if it looked good, they probably would have,
Even their 'steel ball lift' figure is somewhat meaningless, since the compressed air stream could happily do that with enough flow/pressure..
Re:Not much to see here.. (Score:5, Informative)
In the end, the team was able to show that they get thrust of about 28N/kW, which seems to be quite close to that produced by a modern turbofan (by my rough calculations, a modern turbofan produces about 15N/kW). The thrust efficiency is corrected for the thrust simply due to the blower’s airflow as well.
Re:Not much to see here.. (Score:5, Informative)
Re:Not much to see here.. (Score:5, Interesting)
Thanks for the link. I found the next two paragraphs to be interesting, too. Emphasis is mine.
The question is one of scaling. At the air flow rates (around 1m3/h) and microwave powers (less than 1kW) that the researchers tested, everything scaled very nicely. But the airflows are in the region of about 15,000 times lower than those for a full-sized engine. The thrust also has to scale by about four orders of magnitude (meaning the power does, too). Extrapolating linear trends over four orders of magnitude is a good way to be disappointed in life.
I also believe that the warning signs are already in the paper. If you look carefully, there are some missing data points. For instance, at the highest microwave power, only lower flow rates are tested, while for low microwave power, all flow rates are tested. That seems like an odd omission. I suspect the plasma is not stable at high flows and high powers.
Re:Not much to see here.. (Score:4, Informative)
According to TFA it's 28 N / kW. They claim that is similar to a fossil jet engine.
I don't know much about jet engines but some research suggests that a modern commercial one like a Trent can produce about 300,000 N, which would require about 10,700 kW of power. That's not beyond the realms of possibility for a battery - approximate 33 Tesla packs could do it.
So maybe it would be more practical for smaller regional aircraft, or used with hydrogen fuel cells or something.
Then again it's only a prototype, doubtless it will get more efficient as it is developed.
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Maybe, but since they need to deliver "full self driving" to current cars the very most they can do is retrofit it to them somehow.
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According to TFA it's 28 N / kW. They claim that is similar to a fossil jet engine.
Now show what the weight of the required energy storage for the same thrust as a fossile-fueled jet engine would be, compared against the weight of the fuel that the conventional jet would need to carry. And project the efficiency of such an aircraft across a normal flight regimen, accounting for the fact that a fossil-fueled aircraft burns off its fuel load and becomes lighter as the flight goes on, while other forms of energy storage like batteries retain their full weight over the whole flight. Yes, the
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"but it's the entire system that needs to be considered when determining whether it's practical, not just the engine."
Yes but it is the prototype of a new form of thrust engine. It would be rather silly to toss it out just because the initial prototype wasn't practical.
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See my other comment. A 20t battery should provide enough power and a useful flight time, which is possible in a something like a regional jet.
And of course this is a prototype, it will probably improve.
Re: Not much to see here.. (Score:2)
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Efficiency is pretty much all that counts here
Efficiency is completely irrelevant when first proving a concept. Now that the concept is proven maybe the next paper will address your impatience.
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Ahhh! A news release that doesn't cover all the Science and numbers. That is unheard of. I need all my news articles to be gigabytes big, and take me months to go threw them. Anything less is just some hoax.
Here is a hint. If you read a news article that spikes your interest, you can do research beyond that article to gain more information on the topic. This holds for more than just science news, but with any sorts of news. As one article will try to summarize the content to what the writer and editor
What does this solve - energy source? (Score:5, Insightful)
I understand plasma thrusters have a high specific impulse, which is nice in space applications.
But sorry, nice with a "fossil free" engine, but could you perhaps be a bit more clear what this is about? From what I read this is an engine that converts electricity to thrust - but en electric fan already does that. Would this be more efficient than an electric prop or fan, with more input power going to thrust, or with lower weight?
And a plane using it still would need batteries, which is the limiting factor for electric aircraft currently. ...
We probably have to stay on ground (electric trains or cars, possibly ships) for a while more if we like to go electric on long-distance trips
Re:What does this solve - energy source? (Score:5, Informative)
tl;dr: Propellers are good at slow speeds. Jet engines are good at high speeds.
Otherwise it's of course a good question. What matters is the thrust to weight ratio including the energy source that is required to power this engine.
Although I think that the "works without fossil fuels" is a bit misleading or at least hast been interpreted in the wrong way. If they wanted to get the science better across they should have been aware of the *political connotation that the word "fossil fuel" carries with it in these times. They should probably have said "works without combustible fuels" instead.
A traditional jet engine works among other things by combining the air it draws in with fuel and then igniting, which causes the gas or plasma if you will to expand and then being expelled through a nozzle to achieve something similar that a rocket engine does.
It's this ignition process that they have found an alternative for, where you do no longer need to inject a combustible fuel that has to be ignited but impart that additional energy through a magnetron (?) into the air.
The engine itself could still be powered by combustible fuels, like fossil fuels, though, it just doesn't require them to generate the name giving jet it produces.
*I could go on on a tirade about the requirements to politically correct speech, but I don't want to poke that bear right now.
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You should look up the differences between propeller and jet engines. tl;dr: Propellers are good at slow speeds. Jet engines are good at high speeds.
If your talking about a very old and very inefficient type of Jet engine called a Turbo Jet than you are correct however if your talking about a
modern Jet engine called a Turbo Fan than you are incorrect as a Turbo Fan gets most of its thrust , something like 90 %, through a Fan
which is powered by a Jet engine core connected to a Turbine.
In many ways a Turbo Jet is a hybrid of a propeller and a Jet engine.
https://en.wikipedia.org/wiki/... [wikipedia.org]
This invention is important because it has less moving p
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Sure, and with this "negligible" beam spread the passengers will arrive at their destination thoroughly cooked. What you described is a flying microwave oven.
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Now what matters would be the wavelenths that might be used there, because the metal hulls of aeroplanes only work effectively as a Faraday cage for relatively long wavelengths.
For example cellphones can and do work while you're in the air. Via satellite roaming you could make calls, send and receive SMS, and access the internet
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But sorry, nice with a "fossil free" engine, but could you perhaps be a bit more clear what this is about?
Such engines are going to be really useful for a nuclear-powered aircraft. It's a nice concept, let's see how it develops.
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Aah.. so that's how the IronMan suit does it!
Re:What does this solve - energy source? (Score:4, Informative)
Engines that run off nuclear power have already been developed. You either directly run the compressed air over the rods and leave a trail of fallout behind you or indirectly do it through a heat exchanger, with an efficiency loss. The major problem is shielding everyone from the reactor, which no one has figured out yet. Fusion is still off the table until we have a known working reactor, so yeah. Unless there's an efficiency gain to using the air plasma, we might as well just use a glorified hair dryer as an engine. Batteries are still limited in terms of power density, and don't have the benefit of decreasing in weight as energy is consumed. There's an electric DHC-2 Beaver in Vancouver [flightglobal.com] soon to run low passenger commercial flights - it has about 30 minutes of flight with 30 minutes of reserve charge. The article talks about the power density increasing, so that's encouraging, but we still have a ways to go.
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Engines that run off nuclear power have already been developed. You either directly run the compressed air over the rods and leave a trail of fallout behind you or indirectly do it through a heat exchanger, with an efficiency loss. The major problem is shielding everyone from the reactor, which no one has figured out yet.
I think you left off the other problem with this method, you essentially have a near critical nuclear explosion happening at all times the engine is active. That’s how Russia nuked itself [nytimes.com] last year.
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Engines that run off nuclear power have already been developed. You either directly run the compressed air over the rods and leave a trail of fallout behind you or indirectly do it through a heat exchanger, with an efficiency loss. The major problem is shielding everyone from the reactor, which no one has figured out yet. Fusion is still off the table until we have a known working reactor, so yeah. Unless there's an efficiency gain to using the air plasma, we might as well just use a glorified hair dryer as an engine. Batteries are still limited in terms of power density, and don't have the benefit of decreasing in weight as energy is consumed. There's an electric DHC-2 Beaver in Vancouver [flightglobal.com] soon to run low passenger commercial flights - it has about 30 minutes of flight with 30 minutes of reserve charge. The article talks about the power density increasing, so that's encouraging, but we still have a ways to go.
Thanks, it's really insightful! One minor correction is that while DHC-2 Beaver is indeed a workable concept, to fly for 30 minutes it still needs those improved 400Wh/kg batteries which are better than today best batteries... at least that's what I have figured out from the language of the article. So it just isn't there for a moment. Although it's a quite impressive achievement, indeed.
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One of the things this might be able to do is work at a much higher altitude than an electric prop. My understanding is that jet engines are basically less efficient than props, but they make up for it by going to higher altitudes where the air is thinner and so there's less resistance. Flight is tricky and a lot of puzzle pieces have to fit together into a complex equation to say if one technology is better than another. This may or may not turn out to be a better technology than what we've already got. It
Electric Jet Now Possible (Score:2)
Would this be more efficient than an electric prop or fan, with more input power going to thrust, or with lower weight?
Propeller based engines have a limited speed which, IIRC, comes from limiting the tips of the propeller from exceeding the speed of sound. This engine, like a jet, should not have such a limitation.
The problem is the power source now. I cannot see batteries providing the required power-to-weight ratio for a long time since this engine is likely to be far less efficient than a propeller and batteries are not even practical for those yet. I would expect fuel cell technology as the most likely candidate fo
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I find it interesting that we can find new power sources when we put our minds to it. The problem has been Fossil Fuels is our normal go-to fuel.
While having a good energy density ratio, for most conversions of it to energy there is a lot of waste lost to Heat and Sound as well. Other energies may be less dense but more efficient into producing the energy that they want to use. Often with some rethinking these differences balance out and you get a cleaner energy source with no major trade offs. After yo
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While that's true, the relevant comparison is really between a turboprop (basically a propeller driven by a jet) and a turbofan (a fancy propeller enclosed in a cowl, driven by a jet). The advantage of the turbofan seems to be the cowl, which allows the air to be compressed and the airflow to be better controlled, allowing it to fly higher and faster.
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Well, it runs on electricity, so any electricity source will do.
I'm picturing an Anton AN-225 with one of those old Soviet-designed naval reactors running on HEU... Sure, it ticks all the nightmare checkboxes, but it appeals to the mad scientist in me.
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"it ticks all the nightmare checkboxes": yeah, I like that. I see your "SuperAnton" crewed by little folks w/ big heads that can't walk well.
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Your picture is understandable, but there are more uses of gas turbines. There are stationary ones, and some are even used to power aircraft carriers, because they have a huge power output for a relatively small engine. If this engine turns out to be efficient, it would not be strange to build a power plant based on it.
In particular, it would be nice if it were a good alternative for the Stirling engine, which is used in some solar power plants. Stirling engines tend to be most efficient when they remain sm
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Transitioning intake air to subsonic velocity and then re-accelerating it by increasing pressure with appropriate ducting is a very well-understood technology.
-jcr
Yea, except if you don’t apply heat outside of that from compression it doesn’t make for a reasonably efficient engine. That’s why this design is at least interesting.
Hellalot of electricity for plasma (Score:3)
Interesting. It does seem to take a hellalot of electricity to create the plasma. A schematic showed what looked like a useful thrust, but took 1000W to do so. To get a 100KG plane to move an inch would take MW's of electricity.
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TFP says 28N per kW. 100,000 N is useful for small passenger jets so you would need about 3.5MW. But this is only a prototype so it will doubtless get more efficient in future, and 3.5MW is peak with a lower cruising load.
Anyway, say you wanted 4MWh of energy available for flights around the 1-1.5 hour mark plus some margin, i.e. regional jets. Say around 500kg/100kWh for the battery, so a 20 t battery. That's actually practical, the maximum take-off weight of a Mitsubishi SpaceJet is about 39 t.
Alternative
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Hydrogen is 33 KWh/kg. The FC is "around" 60% efficient (current car FCs), so around 20 KWh/kg effective. Not sure of the Magnetron efficiency, but they are generally quite good. You can also use their waste heat to pre-heat the plasma stream.
The real issue is the storage tank weight and volume for the H2. If you store H2 cryo, then this is probably at least at good as Jet-A in terms of weight and energy density. LH2 does not need to be pressurized, just stored in a "vacuum bottle" (like a good thermos
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The real issue is the storage tank weight and volume for the H2. If you store H2 cryo, then this is probably at least at good as Jet-A in terms of weight and energy density.
Liquid H2 has about triple the energy by mass over jet fuel, by volume it is about 1/3rd.
https://en.wikipedia.org/wiki/... [wikipedia.org]
There's several problems with using liquid H2 as aircraft fuel. One that comes to mind is that liquid H2 is not an energy source, but jet fuel is. One reason we love our petroleum fuels so much is that for all the effort we put into it we get a lot more back out. Enough of a multiple of energy gain to allow us such luxuries like sending people and cargo on aircraft. Liquid H2 does no
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That sounds reasonable. So, if the jets were removed, the weight of engines and fuel could be replaced by the new power source and thrusters. Using SpaceJet specs...
.820 kg/l = 9922kg.
Fuel Capacity 12,100 L / 3,200 US gal, with jet fuel being about 0.820 kg/l (6.84 lb/US gal). So 12,100L *
Pratt & Whitney PW1200G weighs 3,800 lb (1,724 kg), and 2 of them are 3448kg.
If this is correct, they'd have 13370kg (~15t) to play with for the replacement power source out of the 42800kg (~42t) MTOW.
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They give 28N/kW as the thrust efficiency. An extremely overpowered plane that can climb straight up (fighters and stunt planes, not passenger jets or Cessnas) would need to completely counteract gravity. So, your 100kg plane in that case would need 100kg * 10 m/s/s = 1000N of thrust. 1000N / 28N/kW = 35kW. Not bad at all. Where were you getting your MW number from?
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You're right, I used the wrong scale. I was thinking 100000kg, which would be a large airplane. A small jet, as mentioned by amimojo, would be about half that weight, and her estimate is 3.5MW
More to the point, I guess, for an experimental system, one would put it on an ultralight, which in the US "weighs less than 254 pounds (115 kg) empty weight". So your numbers are close to that. What would be the lightest method that would provide about 35KW?
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35kW is a lot less than a MW, but is still a substantial amount of power... the Chevy Volt battery sources >100kW during hard acceleration. Looks like the power density (or specific power) of batteries can regularly reach 1000W/kg, lithium titanate claims to be able to achieve 5000W/kg, but that's with energy density that's quite bad.
Overall though, at 1000W/kg you need to devote 35kg of your ultralight airplane to batteries - that's quite overpowered, though, I think a more typical number for an ultrali
It will work (Score:5, Interesting)
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I'm joking of course.
Partially.
What are the exhaust components? (Score:5, Interesting)
This plasma engine supposedly superheats atmospheric nitrogen and oxygen into a plasma. I have to think a significant fraction of that will end up as NOx. Maybe you know if you've researched it?
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Hey give us more details .. how similar was your concept? Air plasma, or a different pulsed plasma jet concept?
Now all we need is high energy density batteries.. (Score:1)
.... as high as ... *hydrocarbons*.
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I thought the thermocouples were pretty inefficient and the shielding made them too heavy to get a lot of portable use out of them, at least at any kind of power scale beyond what a deep space probe uses.
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We should perhaps look to high energ
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We can actually control the rate of nuclear decay. It just requires a "chain reaction". Then again, you create a whole new set of issues.
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For the case of fission the rate is possible to be controlled by having a moderator that reduces the kinetic energy of the subatomic particles that might hit the atomic nucleus of other atoms and causing them to split into two or more parts, like in thermal neutron reactors.
The fission phenomenon relies on the strong nuclear force. Fission as an exothermic (chain) reaction also only works in elements with a higher nuclei mass than iron, according to the mass defect. If
So (Score:1)
Maybe by the time we have a SARS-COV2 vaccine and people are thinking about flying again they will have some details that make more sense.
Interesting (Score:2)
The article is interesting, although super short: https://aip.scitation.org/doi/... [scitation.org]
The conclusion is around 11 to 28 N of thrust per kW, which is pretty good. That's comparable to what is found in the Airbus E-Fan [wikipedia.org]. However, given that LiIon batteries are at about 250Wh/kg, it means that such engine would sustain the thrust of its own weight for no more than 30 minutes in pure vertical lift. Again, batteries are the bottleneck here.
Go nuclear (Score:2)
Don't see why these aircraft couldn't have SMRs on them.
https://www.rolls-royce.com/pr... [rolls-royce.com]
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Ok, but aircraft don't have to sustain the thrust of their own weight. The Airbus A380, for example, has a thrust to weight ratio of .223. So that would be about 2 hours and 14 minutes. Obviously you need a payload as well, which would shorten it. But there are uses for aircraft that only make short hops like that. Also, higher specific energy batteries do exist, they're just not conventionally rechargeable.
Does it scale? (Score:2)
Does this technology scale?
But is it real? (Score:2)
Without fossil fuels? We did that already. (Score:2)
We know how to make aircraft fly without fossil fuels. It's been done. We synthesize hydrocarbons, and we use nuclear power for the energy source.
Electric batteries will not get a passenger carrying aircraft across oceans. For that we need fuels that are very high in density, and can be consumed at a rate sufficient to provide the power needed to maintain flight. This means hydrocarbons.
Why does it have to be nuclear power? It doesn't all have to be nuclear power but if we are to have enough energy lef
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Electric batteries will not get a passenger carrying aircraft across oceans.
Sure they will. If they're powering a zeppelin.
I like being technically correct. It's the best kind of correct.
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Sure they will. If they're powering a zeppelin.
I like being technically correct. It's the best kind of correct.
I'd like to see the numbers on that.
I've seen the numbers on battery electric powered ships and they don't look good. Like a zeppelin it's certainly possible to build a ship with electric motors to drive the propellers and batteries to provide the power. If put to sea and given enough time then it will reach it's destination. Then the question becomes, did the electric motors get the ship to port? Or, was it just the ocean current? Sure, the electric motors would certainly be helpful in navigating into
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I've seen the numbers on battery electric powered ships and they don't look good. Like a zeppelin it's certainly possible to build a ship with electric motors to drive the propellers and batteries to provide the power. If put to sea and given enough time then it will reach it's destination. Then the question becomes, did the electric motors get the ship to port? Or, was it just the ocean current? Sure, the electric motors would certainly be helpful in navigating into and out of port but that's far from powering the ship several thousand miles.
The bunker oil and kerosene powered vehicles of today already take advantage of the prevailing flow in the fluid they're navigating. Ocean-going ships follow ocean currents on purpose. Aircraft, both international and domestic, make a point of ascending to the proper altitude to catch a favorable wind. If you've flown any time in the past 20 years, odds are the captain will have explicitly told you what they're doing. When you arrive early at your gate, they will tell you about the tailwind that made it
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The "fuel" for solar might be free, but capturing the energy isn't. EROEI is important precisely because it can generalize across differences like that.
The mistake people make when using EROEI is using "at the wellhead" values. An EROEI of 50 for Saudi light sweet crude sounds pretty good compared to 8 for solar, until you realize you have to refine that oil, ship it halfway around the world, then usually burn it in a thermal engine with 30% efficiency. On the solar side, if you live somewhere there's a dec
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But who cares what the EROEI is for say wind? If it is economical and produces minimal pollution and makes enough energy for its own manufacturing and making more turbines... Well so what if some other source is a bit better on EROEI?
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Totally making up numbers.
Let's suppose you've got an EROEI for wind that's 20, and for solar that's 10. Your society has 10 units of surplus energy to invest. If you build wind with that, in the future you'll have 200 units. If you build solar, you'll have 100.
The EROEI places a limit on the growth rate of your energy production, which in practice places a limit on the growth rate of your economy. You might also choose a lower EROEI if your growth is limited by something other than energy, like space, labo
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Sure. Energy availability and economic growth have been closely linked since at least the beginning of the industrial revolution. We don't have any obvious energy limitations on building windmills at the moment because we're also still benefitting from lots of high EROEI energy sources. The energy to run the mines, smelt the aluminum and iron, transport everything, build the windmill, and maintain the windmill is primarily provided by conventional energy sources. Also, as I said, the EROEI of wind is probab
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Wind could actually massively boost growth rates. Right now we need to stimulate our economies and create new jobs. What better way than a massive infrastructure project like conversion to renewable energy?
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Building anything, including the famous digging holes and then filling them in, can give an apparent short term boost, sure. Wind and solar can give a real, short and long term boost, not because EROEI isn't important, but because it is.
US shale oil has an EROEI somewhere between less than one to about 10ish at the wellhead. By the time you turn it into gasoline and diesel and actually burn it in your car, it's pretty dismal. Conventional oil averages about 20, which is a long, long way from the triple digi
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It won't be economical with nuclear though.
The same was said about solar. We were able to lower costs only by ramping up production and allowing competition, development, and economy of scale to bring costs down. Nuclear power will never be economical if we don't try.
Also you still haven't explained why anyone should care about EROEI.
Because more is better. If someone puts in X amount of raw material, Y amount of labor, and gets Z amount of energy out then that's not as good as getting 4 times Z out. Nuclear power is like this compared to solar. Comparing some of the best solar to some of the worst nuclear is a
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Nuclear fuel is "free"? As in it costs nothing to mine, nothing to refine, nothing to transport and nothing to store when used?
Pull the other one, it's got bells on.
Hypersonic flight - IF you had a power source (Score:2)
It might be able to operate as the heat source for a scramjet, where its very difficult to sustain burning, and that could allow hyper-sonic vehicle - IF you had a power source.
Its possible that there is a very high altitude, high speed regime where a solar powered system works, but it seems like a stretch .
Nuclear power could work. Possibly laser power transmission as well, though that sounds really difficult to make work.
Probably not useful for subsonic flight.
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You could use a turbine as an energy source. Sure it still uses fossil fuels (or hydrogen or something) but it lets you separate the energy source from the propulsion, which could provide the flexibility needed for hypersonic engines. I don't think it's a new idea though.
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It isn't completely clear, but I think SABER is a "conventinal" ramjet - eg the inlet air is slowed to subsonic for combustion - which works up to around mach 5. Above that you lose too much energy slowing down the inlet air. Supersonic combustion ramjets (where the air is never slowed to subsonic) are in principal possible, but getting the fuel to mix in the airstream is difficult.
The microwave heating would solve the fuel mixing problem. OTOH, the lack of any suitable power source probably makes it com
Not a scientist (Score:2)
I'm not a scientist, but it seems to me if it takes a KW of electricity to generate enough thrust to raise a 1Kg ball 1", do we have a power source that can supply 1Kw of power that weighs substantially less tha 1Kg? For instance, If it takes 2Kg of batteries to generate enough thrust to lift 1Kg, how can this propulsion system ever "get off the ground".
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Wings can generate more lift than drag. So a relatively small amount of force forward can generate a lot of lift. Typical airliners have a lift/ drag ratio ranging 15:1 to 22:1. High performance gliders can get to something like 70:1.
This doesn't violate conservation of energy because the lift is in a different direction from the drag. (that isn't obvious but would take a while to explain).
Reminds me a little of. . . (Score:2)
https://en.wikipedia.org/wiki/... [wikipedia.org].
So you need electricity and air (Score:2)
Rare things to find in a rocket.
VASIMR for Earth use (Score:2)
VASIMR [wikipedia.org]
same concept, only difference seems to be the density of the propellant.
Re: Engineer. He calls himself an engineer. (Score:2)
Re: (Score:2)
This is cool. It's always bothered me when other things claim to be an electric "jet", and they're just some sort of arrangement of ducted fans. You can't have a jet without a jet engine, and you can't have a jet engine without expansion of gases.
It's always bothered you that other people don't conform to your definition of the word "jet"? If course you can have a jet without a jet engine, you can even have a jet of water. Here, maybe this will make you feel less bothered:
jet[ jet ]
noun
a stream of a liquid, gas, or small solid particles forcefully shooting forth from a nozzle, orifice, etc.
Re: (Score:2)
A "jet" aircraft engine, by definition, gets it's power from a turbine. You can just use that (a turbojet), hook it up to a propeller (turboprop), a ducted fan (turbofan) or an unducted fan (propfan).
The OP is correct: ducted fans do not make a jet aircraft engine. The turbine does.
Re: (Score:2, Interesting)
Why don't you drink some bleach like Trump told you to?