Anykind of high altitude combustion is thought to have about 2-4 times the heating impact as emissions at the earths surface. This is for water vapour (alkthough thats quite a complex one) and for CO2 and nitrogen oxides.

Plus nice, refined aircraft fuel is getting pricey and will get much more so.

Hydrogen is silly, because the materials to carry it make it too heavy, and its not a good use of energy (yet). Cryo-cooled is not currently practical.

Biofuels not currently practical

Anyway, its also an expensive business however you cut it.

To bring biug improvements in environmental and economic impacts, several big-money consortia have looked at this. One currently in Europe intends to develop 'out of the box' solutions to these problems and has considered stuff 'to crazy' for others to look at - the good thing though, this is the industry and the governments working together to fund and develop these ideas. See current issue of Flight.

These include in-flight refueling from short distance shuttles.

I've got some ideas my own, and thought I'd outline it briefly:

Once an aircraft is airbourne, and fast/high enough, it could be powered by microwaves from the ground. This is not new idea nor is it yet to be demonstrated with models, having passed these hurdles, but the distances and the progress in microwave energy transmission look very favourable to commercial application. The puzzle is how to economically line a route with microwave power transmitters and supply those transmitters, as well as garanteeing power supply.

Here's how we'd solve some of these problems:

1 - the transmitters are spaced along the route, and each one is connected by a l;ong distance, high voiltage DC transmission cable, just as are already being constructed, and would be compatibvle with this architecture.

This means each end of the route can connect the grid and exchange power (aka the 'SuperGrid'). The SuperGrid is a serious proposition gaining interest, to link renewables and solar around Eurasia and North Africa. I proposed this idea independently myself some years ago, but with different cable technology (I didn't know enough about it to be honest with you, but I did by coincidence use the same name for the concept!)

Anyway,

2 - the problem of intermittence due to some disaster. Each transmitter would be connected to a Flow Battery (VRB power systems) or other future battery. Flow Batteries are already 'off the shelf' and will soon be economical just by selling off peak power back at on peak). They are highly reliable, especially if made out of several modules.

3 - the aircraft will be powered by a geared turbofan with a hybrid design using some leading edge motor design. The clutch is used to switch from the turbine to the motor in flight, and the turbo-fan becomes electric. A small battery can be used like a micro-hybnrid to power the jet turbine up, in the event of power loss from the microwave power receiver.

Several such turbofans would be placed above the wing. This, like the SAX40 concept would reduce noise. What we also want is boundary layer control. This allows a smaller wing asd at takeoff the smaller wing generates a lot more life if air is forced over its top at moderate pressure.
This also reduces speed needed to gain takeoff and reduces runway length. Crucially, it eliminates risk of stalling.

The technology has never been propperly developed, but it is proven. The British aircraft TR2 was only able to acheive at that time such ahead of its time performance, in range, speed, field operability, sprint and climb, because it could employ a high lift, low drag fixed wing of short span.

Short span also reduces weight appreciably. Much of the weight in an aircraft can be observed to be in the wing reinforcement and attachment. This added reinforcement is a function of force x distance acting like levers. Supporting long wingspans adds a lot of weight. The wing can be shortened by using two, or a blended wing / lifting body, and stability gained by use of gyroscopic forces generated by compact very fast flywheels.

Anyway I suppose I'd better draw this. But the potential for energy efficiency needs to be fully comprehended if the idea is to be propperly appraised. By removing most of the fuel payload, and by designing electric motors into the airfrane (which ought to make boundary layer control a lot easier to achieve) and by other methods, the mass per passenger shoulds come down a lot, and that ought to compensate for some electricity costs. The all-round benefits need to be considered, especially if the power is cheap, off peak sources, and the network can already pay for itself in terms of a distribution network for the grid. Access to cheaper electricity made in the third world and rapidly falling cost of renewable power should be considered amongst the potential economics.

One of the big influencers of the economics is cheap batteries, and batteries that can get above the maximum efficiency for flow batteries which is about 75%.

Anyway, it ought to work.

I foorgot to add -

to breifly recap, the idea is to develop hybrid electric-fuel planes that can use either energy source, and distribute electricity to the plane by microwave transmitter. This is distributed along a DC high voltage long distance transmission cable.

Power supply is guaranteed - this allows a minimisation of onboard fuel mass, and thereby increased payload.

Power supply is guaranteed by use of flow battery, or better, on each transmitter, storing surplus off peak power

Power supply is further backed up by reserve of fuel on aircraft so that one transmitter can go and the aiurcraft can find others at any point on the route to remain airbourne

Switch between energy sources is acheived by integration of motors and turbines into the turbofan

The vehicle would probably use chemical fuel to take-off as well.


The point I forgot to add, these high voltage transmission cables also could be used to supply surplus enmergy to make hydrogen. Rather than adding cost to cryo-cool the hydrogen, the system would probably use some other storage material or liquid methane. The ammount of fuel carried would be much less, so electrolysis sources of hydrogen would be more feasible.

A customer of mine was one of the leading engineers in the gov's laser development program, and currently does something with some agency he wont name, but, smart motherfucker none the less. Anywho, he was saying that a laser could possibly transmit high amounts of energy through its beam, and the energy can be stored in some type of capacitor, among the very few other things he would tell me when I picked his brain. He was telling me this was a way to transmit energy in space. (he originally told me he was just a computer dork, nothing more. But then he told me what he sorta did, but I had to fill in the blanks on a lot of this stuff)

Anywho, I know fuck-all about laser's. Does this sound possible and could this apply to this situation? Laser-beam some energy to capacitors on airplanes?

I have to go to his house next weekend to paint his porch, so ill ask his input on this topic.

You are at it again, ATB. Keep up the good work. Now for poking a few holes in the weak spots. First of all, why DC transmission lines? I see no reason for that plus it would cost more and be harder to transmit. That is why we use AC, you know. And how are you going to keep the microwaves in a tight beam precisely focused on the plane? And what about the passengers and crew being exposed to the radiation? It is harmful you know. What is this flow battery you speak of?

I was considering it as high voltage DC cables lose very little power over longer distances, its only a few percent per 1000 km, therefore I thought it better as these routes would be long. On the other hand, DC is expensive to convcert to AC and step up and down in voltage. If storage batteries and flow batteries are used, these could be used to act as convertor steps as well. But I'd have to get talking to a dedicated engineer on that one and I have to be honest that I dont know what the ideal type of current is for a microwave transmitter. The idea I just burrowed from the 'super grid' project to promote a Euro-Africa-Middle East solar power and transmission network.

Flow batteries use a pumpable liquid electrolyte. New Scientist did an article recently. Look up vanadium flow battery or vanadium redox battery.

Microwave tranbsmission of power looked quite promising for distances of a few kilometers. When I researched that I came across impressive reports of Japanese engineers showing a decent transmission over 85% efficiency.

http://en.wikipedia.org/wiki/Microwave_power_transmission

The underside of the aircraft would be shielded, similar to the way that your microwave oven is I would suggest, though there are differences.

The beam intensity would be higher than those used in other power transmission technology experiments- we need to transmit over a 100MW to the aircraft travelling as fast as a Jumbo at the same altitude

ATB, you are the ivory tower theorist and I seem to be in the role of the grease monkey explaining how you can't get to the moon by flapping your arms even if they have wings attached. DC does not experience lower losses than AC, to the best of my knowledge. There would be less induction loss but that can be minimized. AC is the way to go.

You can't reliably insulate the passenger and crew section of an aircraft while at the same time having high energy MW beams focused on it for motive power. You could surround the people with metal but it would tend to reradiate the MW energy unless it was grounded. Kind of hard to find a ground up there in the air.

Lasers would be easier in that respect but would have problems all their own.

I had not heard about the flow batteries. New technology is always interesting. Maybe they will use them in cars next?

They might be used on buses and the like but for transport there are better options.

Flow batteries would make good options to store power for electric vehicles that would then charge up lithium batteries, or maybe other promising storage.

DC high voltage cables does experience less loses, but the economics has to be countered by the cost pof conversion at each end for normal AC grid usage. This means that the efficiency gains appear when the transmission distance is over 400 or so km.

I'm not sure about the grounding issue, the microwave bean would be employed to agitate an electrical circuit, and the circuit would carry it to work motors?

These circuits would be shiekded, along with MW shielding on the aircraft.

The energy needed per m2 is still rather a lot, so the m2 energy being received would by large, leading to a largish heating effect as well.

DC has never been used for high voltage transmission even over long distances, that I know of. What looks like a theoretical advantage in the lab turns out not to work in the field very often. You have touched on some of the reasons.

Would you like to be a passenger on a plane receiving MW transmissions? I wouldn't. But it's good to theorize about new ways of doing things. That's how we get ahead. Unfortunately, most new ideas get shot down by practical considerations. I've had lots of mine shot down.

Yes. I'd be prepared to travel in a vehicle that was appropriately insulated - its already a pretty hairy thing to do, flying a plane so TBH I'd be pleased the beam was on rather than off!

But on the practical side, the power levels needed are rather beefy. Thats the only real issue that I can see thats a technical question. If it needs 100MW and it had say 5000m2 area underside. just for arguments sake, then it would be receiving 20KW/ m2

If it were 95% efficient thats 1kw/m2 heating, which is about the same as bright sunlight so thats OK. I believe it would be efficient enough at that end, at lower energy densities, but again its the high density which I think is unproven - though the military and high powered radars ought to have seen experience in that.

ATB, there is no way to totally shield the passengers in that scenario. Saying the power levels are only "about the same as bright sunlight so thats OK" is deluding yourself. Sunlight does not harm in the same way as microwaves and a high sunlight level at the earth's surface is less substantially less than 1 kw/m2. You still haven't told us how you will be able to track the airplane and keep the beam precisely on target. Wouldn't want to fry an ordinary airplane nearby or orbiting satellite. The concept is not totally unworkable but sounds dangerous as hell. I'll let you be the passenger on that plane.

Don't forget the inefficiencies of converting electricity to micro. Add in the losses in the atmosphere and attempting to receive and convert it, and you lose all the benefit of not having to carry the weight of the fuel. Plus the radiation danger, problems in tracking and so on. The light laser idea has the same drawbacks but is not as dangerous.

No I'm not talking about the safety, I'm talking anbout the haeting effects on the skin and structure of the aircraft. The listed efficiencies for some types of microwave-DC converters are 98% plus efficient.


Naturally, if you can get the efficiency up, the ammount of shielding is reduced. I'd anticipate that the aircraft is placed ontop of a skin that absorbs microwaves. Then there is an insulating layer similar to that on the transparent part of the microwave ovenm that physically blocks microwaves because they are two large to penetrate through. The energy intensity inside a microwave oven is similar to that which would be experienced on the outside of the aircraft. Yet on our side of a microwave oven, we are safe.

Similar principles I believe would apply to microwave powered arcraft.



The efficiencies look pretty good for other systems with massive distances, according to calculations. It readily penetrates the atmosphere, which is one reason that Microwave power transmission is even being considered. But, this is not with very high transmission densities between a transmitter and rectenna.

This as far as I am aware is only being demonstrated in the medium power range. For transmission to aicraft from ground stations, we would consider several options described in the internet literature available to me (it must be noted, that most research on MW beams is classified and a lot of progress has probably been made compared with minute civil reasearch programs), these include transmitters that can be electrically steered towards the target without moving parts, and mechanical 'optical' focusing devices that create a focused beam.

My preferred embodiment would be to have a line that transmitted directly up and conducted electricity along it. This coould transfer power either side so that mechanical movement is minimal or not needed, rather than large transmitters that are seperated by several hundred meters or more.

Lets get a few obstacles out of the way

Long distance HVDC systems are proven and already commercially exist, such as the links between Britain and France which give us their nuclear electricity

Just search High Voltage DC on wiki or something. There is a lot more planned and there will be a large long distance network in Europe

Very high efficiency MW to DC conversion has been demonstrated in reasonably compact converters at 25kw, but these in this form would not be adaptable to aircraft (heavy, wrong shape). Smaller systems with a means to focus MW's to a converter have been considered that maybe be encorporated into skin and internal underside of the aircraft, but there is a lot more to the art

High power MW transmission, with efficient beam control and constriction, and ideally, the development of MASAR's are being persued for space application - i.e. low-to-high orbit transport of spacecraft using transmission of MW to the target which would use electric propulsion or magnetic propolsion in the case of tethers. High power electric propulsion is underway also. These projects are also being considered for other missions such as planetary probes and airships for research. Similar technology would be needed for supporting terrestrial aircraft, but the distances much much less (3 orders of magnitude)

High power transmission which is not far from the densities we need (well within an order of magnitude), is being actively researched and demonstrated in a number of research programs, some of which are ancient (1960's) and which powered flying aircraft prototypes. I am aware of two aircraft prototypes that have been built, one which was operated by a moving vehicle generator and another that was tethered helicopter in the 60's, and research applications for others.

I am not aware of any reason that the MW cannot be effectively shielded to a passenger cabin. The essential engineering is apparently similar to, but no more spectacular than, the task of creating an artificial pressure in the aircraft cabin by means of a reliable envelope.

The 'inefficiency' or transmission loses do not make strong arguments against the use of hydrocarbons pere se, on grounds of weight savings. Hydrocarbons of suitable form for existing aircraft are going to get more expensive and have a heavy impact on the atmosphere. The electricity we transmit is transmitted to the MW transmitter very efficiently using HVDC. The issue is converting from HVDC to MW and beam control as far as I can see, which would need to be analysed by someone familiar to the art and with a suitable innovation budget. Thus stating that there are inherent difficulties here seems to me to be an incorrect assumption - there may be, but there doesn't seem to be fundamental reasons to expect that this is particularly problematic for longer term technology projections, as presented by current developments at lab stages which are enevitably immature, yet still reasonably promising based on progress in gerneral for any given advanced technology. I neeed to see fundamental physical reasons that put the kibosch on the transmitters and rectennas for practical reasons for applications like this, over ten to 20 years of technological progress.

The other thing is, taking electricity from countries in which it can be made very cheaply and transporting it to new markets is part of the economics equation. *If* it were straight forward to absorb MW and turn into electricity in a thin and light structure under the surface of the aircraft, and easy enough to transmit, the big issue ios then whether it is straightforward to get power from a high efficiency transmission cable, be it conventional or more exotic like mag boride superconductor, and then convert it to MW. The process of getting out the electricity from an HVDC cable and changing voltage or changing into AC is normally messy. Again, many researchers are already on the case for individual problems, in this case, especially as there is more planning towards HVDC cables.

That's a fine side-effect - sky monopoly!



-just as long as it doesn't warm my champagne.

Of course the irony is that I am opposed to EM pollution. But I dont care so much about frequent flyers - or should I say - 'frequent fryers'?

ATB, I'll grant you that long distance HVDC has been proposed and may be used in spots. The lack of inductive losses makes for a possibility of greater efficiencies but the losses in converting back to AC generally cancels out the benefit. That is kind of a side issue with what you are talking about.

A metal shield will block MW but the energy absorbed has to be dealt with. If you can't run it off to ground, what tends to happen is the metal used to block the radiation reradiates it. You should be able to shield passengers to a degree but not absolutely. The home micro is a different beast. The MW radiation is totally inside and the design is much easier. Up in the sky trying to keep it out is a different animal. Plus, you have to figure that the high intensity beam will at some point be aimed directly at the passengers due to error. Like I say, you can be the passenger, not me.

With spacecraft, it's different in the sense that cost is more or less no object. To have a series of transmitters like you envision would wipe out 100 times over any savings you might get. Yes, it can be done, no it does not make economic sense. Not at this point. That may change in the future.

Tell me again why you want to do this? What exactly is the benefit you are going after? It takes fuel to produce the MW same as airplane fuel.

It's not a side issue - it is being used profitably for many years already. In this model they are already goinbg to be laid across Europe and the ME and eventually on to Asia - if you can cheaply get the DC power to a Microwave generator then such networks would readily be able to derive power generated cheaply in third world countries.

The benefits of HVDC are economically desirable for transmission over certain distances, and no doubt, conversion from DC will improve greatly.



I have no idea why its such a different issue. If you are absorbing 99%+ of the MW you cannot be re-irradiating that - the remainder may radiate back out, but that will not harm anyone. Your shield will simply absorb all the MW and turn into energy. The part which is not will not penetrate an internal shield. There is no problem I am aware of with MW hitting air above the cabin - you would shield the top as well. The air would probably not radiate much. There are question marks about whether we can obtain the densities we desire, and if we did heat air particles a lot, they might radiate energy at a different and less desirable frequency but none that would likely penetrate the cabin.

Its more a question of beam intensity. At low beam intensity it seems to work promisingly, at higher intensity the cone generated by the transmitter may have undesirable properties reacting with the air, based on what I have read.



space is not different and is everybit the same commercial reality, only the size of aviation market and much shorter distances would make aviation much more desirable than space for this application.

The only reason for beamed propulsion in space is generally to raise propulsive mass efficiency.

But similar arguments can be espoused regarding reducing weight or using cheap powersources manufactured in the 3rd world i.e. from thin film solar in deserts.

The central distribution infrastructure (HVDC, battery storage) and the cheap solar electricity WILL be developed - they are certainties, baring a catastrophy for civilisation like an astereoid impact of global ebola pandemic, we will see these technologies rolled out into a large scale movement of energy between continents inside the medium term - they work, they will be economic, there are the vested interests and there is the political will, and industry is already investing in production of all elements. These panels will be made in developing countries, they will ship them to deserts with direct sunshine, they will use cheap land and solar gain there, and probably concentrator mechanisms will be commonplace.

Then prospectors will extend the growing HVDC network to more economic generating fields. These stretch also between major aviation markets.



It cant be done, at least not OFFICIALLY - yet.

There is actually an incredible military interest in microwave power transmission. There is a lot of recently generated research material - all of which is not available to the public and is highly classified.

Whether or not you can have MASARs, lasers operating using microwaves, is an issue. Efficient lasars that convert electricity to power and a target that efficiently converts it back would make transmission over a few miles maximum range very attractive.

Without a MASAR other tricks are needed which look more cumbersome and which may not allow high enough transmitter intensity and effect the air locally. The cost of transmitter depends on what can be done. If it is equivalent to a mobile phone mast, then it would incur no real penalty and open up a vast new market. What we propose is that if efficient and compact high intensity beams could be developed, the economics of transferring to aircraft would follow and a case could be made, especially if the route coincided with long distance transmission of cheap power.



For lower power levels, the technology is actually being developed. Military users would

a - love a weapon like this
b - love to power unmanned vehicles from the ground and are in the development of such concepts with MW.

What I envisage is that the cost of aircraft fuel rises ALOT. You will be forced to start making it.

Making hydrocarbons is pretty difficult, so your talking capture of CO2 with algae, then in the longer run, say solar-thermal hydrolysis. This is why we talk about battery electric vehicles and electrical distribution of energy, avoiding conversion to chemical storage in many ideal scenarios, and this is motivating the political trend towards PHEV's which will take up a larger and larger slice of the vehicle market. Just as direct transmission of electricity is attractive in the case of cars and trains, even with a storage device, the reason being total efficiency, so it is that we apply a similar argument to aircraft, though jet engines are relatively efficient since the exhaust energy also contributes propulsion.

Unless someone can come up with a safe and light hydrogen carrier (nitrogen tends to be toxic or explosive, but could be a good fuel) the hydrogen anyway is a powerful impact on the atmosphere as it generates H20 which is two orders of magnitude more heating that CO2, although obviously shorter lived, carbon is hard to fix. Or well have to get methane hydrates but thats decades away and still we anticipate at this time a pressure to avoid net CO2 emission.

Without these options, the cost will continue to rise, whilst demand increases, and supply will reduce.

This is not a recepi for growth in the aviation sector. I happen to think we will develop solar hydrocarbon sources on a huge scale and faster than others believe, but we actually want to avoid oxidising hydrogen anyway.

Anyway, given this backdrop increasing attention should be made to all possible alternatives and that is in the interest of aviation concerns.

I'd see it develop like this. The military developes ground to air transmission. This is for surveilance drones for troops operating near by.

But, then the military suddenly desires to beef the power transmission so that troops can launch from ground vehicles just behind the fighting, aerial combat platforms that can rain fire down on ground enemy near to ground troops, as back up.

Supporting such platforms with hundreds of KW means putting fast machine guns in the sky. A large but efficient ground diesel or turbine can supply power to support a small aerial fighting vehicle, which can remain airborn indefinitely.

Somebody then says, jeez, why dont we beef these up to MW class vehicles? Think what you could do then?

Lets say that they manage this, and I am an optimist that they will.

Then you would suddenly have a very large market for vehicles that could transfer about cities and they would be much smaller than jumbos, but police and ambulances and commuting aerial vehicles come to mind. The technology would unfold on grids like mobile telephony networks, and gradually expand.

Then people start talking about city-to-city routes.....

So this is of course, decades away. By then though, synthetic hydrogen would be easy but one still has to make assumptions about what carriers for energy would be available to aircraft in this time frame. Depending on that is the economics of any option and what other options develop. So these are based on negative assumptions about cheap liquid energy storage. Frankly the most ideal solution would be to oxidise solid carbon on the electric vehicle - but existing DCFC are only about 1kw-m2 of membrane. That is far too low for aircraft, but it might be immensely improved. This would lead to safe solid fuel, and no water vapour or nitrogen compounds, and the CO2 if obtained from capture programs would thus make it atmospherically benign. DCFC's are also of desired efficiency to make fuel cells attractive alternatives to jet engines from a thermodynamic perspective. At present they are very far from such application, and it is not straight forward to obtain the Carbon in a neutral fashion, in amounts required.

A major advantage of transmitting power to smaller shorter range aircraft would be incorporation as part of a low noise design and the provision of secure power and an onboard backup system, for safety, with large reductions of fuel. Electrical power would be stored by other means on the craft during take off, then supplemented to give a big boost in performance. The power/mass ration of motors can greatly exceed ICE engine designs for personal air transport vehicles as well as reduce noise and maintenance costs. So for small, low altitude transport, the economics would be much in favour of our hypothetical MW transmission - the fuel mass is reduced but so is the mass of the power system replacing ICE designs and also because the efficiency of those designs mooted is usually around 25-30% or lets say up to that of a good diesel - <50%. That creates a big improvement in the argument for electrical systems if the transmission architecture is efficient and affordable. If it saves a lot of energy and there is enough users, then it probable would be surprisingly 'affordable'.

What is the difference between a receiving antenna and a transmitting antenna? The same device can be used for both. The transmitting antenna has an alternating current applied to it and the current is changed into electromagnetic radiation (emr) at the same frequency as the applied voltage. A receiving antenna intercepts emr and produces a voltage at the same frequency. This is part of your scheme, to receive MW radiation and turn it into current. Let me ask you a little question, when the receiving antenna has current flowing in it, how does it know it's supposed to receive and not transmit? It doesn't know and therefore does transmit or reradiate some of the energy from the current back into emr.

This is one of the flaws in the system that makes it dangerous. This is also why it's so hard to shield the passengers. The shielding acts like a receiving antenna and turns the emr into current which can be used or dissipated. However, as long as current is flowing, it will tend to make the shielding radiate at the same frequency.

In an airplane, fuel produces motive power. Under your scheme, fuel produces electricity which makes microwaves which are transmitted and then make electricity which then is turned into motive power. Even if we assume only a 10% loss for each step of the way, which is very low, you still lose at least 40%. That is an optimistic figure and assumes lab type conditions at least. And where is all this low cost electricity in the third world you speak of? Hydroelectric is a potential low cost source but is found only in a few spots. Even then, demand for the electricity soon shoots up driving up the cost. Electricity made with oil, gas or coal costs just about as much in a third world country as anywhere else.

But, no hill for a climber.