Of missiles, and hydrogen...

[Yeoman_dai]

I've been mulling this over, and decided to post a question, or rather a statement on here to see if any more intelligent/learned ppruners can answer me...

We all know that soon, the worlds supply of oil will run out, or at least become so expensive to get out of the earth that drilling becomes pointless. At this point, we must stop using Aviation Fuel.

So, the fuel of the future as far as I can tell, will be Hydrogen. Clean, easy to find etc etc, all very good. However, although it can be used to fuel aircraft engines, it has a major problem, in that it takes up around 3 times as much space to store enough to go, say 100 miles, as it would to store enough petrolium based fuel to go the same distance.


In aircraft this means larger fuel tanks, whereas in rockets this means, surely having to make a missile larger to gain the same range.

For example, a hydrogen propelled short range missile akin to a AIM9 would have to be more the size of an AIM54 Pheonix... with all the disadvantages of weight.


My question to the engineers knocking around here is simply... to what extent am I correct, and if I AM correct (doubtfully) what other options are there?



Note: All information i've been working from is that which is available all over the internet. As you can probably tell this is not from experience, I am simply curious.

[Sun Who]

Hydrazine?
100-200 mL of gas per gram of precursor.
Already used to power space vehicles.
Not sure what the practicalities would be though.

Sun

[taxydual]

Hmm, just a thought then.

If aviation fuel runs out, it will run out for everyone.

So, if no-one is flying, why would you need missiles to shoot at things that aren't flying anyway?

It's not an answer, Yeoman, but the cricket's rained off, she who must be obeyed is out, my pals and I have started on the red wine early.......

And that was the only (admittedly non-sensible) response we could come up with.

All being well, a few grown-up's will come up with some better responses.

Best regards

[Sun Who]

Red wine?
Not sure of the practicalities though.

[Double Zero]

I'm sure you're right about Hydrogen being a future fuel, unless we get nuclear fusion first ( unlikely ) - the Holy Grail is of course to get water to separate into its' H2O components, some say they've managed this in a small way by electolysis...

The other point not mentioned is Hydrogen is rather bad news in gaseous state ( - i.e, as it goes into an engine under pressure ? ) if there's a cock-up of any kind, see ' Hindenberg ' for details !

[Yeoman_dai]

:\ Sterling effort chaps so far

Rather the point is that aircraft can still fly on hydrogen - they just need bigger fuel tanks for similar range so aircraft will be flying, hence a need to shoot some of the naughty ones down.

[Easy Street]

Virtually all missiles in the classes you're talking about use solid rocket motors, so lack of aviation fuel would not be a problem (ignoring the question of powering any launch platform!). Only the really long-range cruise missiles use turbine engines and therefore require kerosene; the quantity of kerosene in those missiles is relatively small and I'm sure they could keep finding enough of it in future.

[Yeoman_dai]

Thank you Easy street! :ok:

[ORAC]

At this point, we must stop using Aviation Fuel. False premise.

1. AAM and the like don't use AVGAS or AVTUR now, neither will they when cheap oil runs out. Solid rocket fuel will continue to be made from alternate organic sources.

2. The same holds true for aircraft. AVTUR does not have to be made from oil or coal, alternate sources such as tar sands, bio-fuel crops or other hydrocarbon sources can be used to manufacture an AVTUR equivalent. It's not a new technology, (http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/tech_rpt_145_45/rpt_145_45_sec2.htm) it just makes it a bit more expensive.

[drustsonoferp]

You've nailed the basic problem with hydrogen, which is why other sources are being actively looked at, like bio-diesels from algae which Boeing were looking at.

Using algae to produce fuel gives you a pretty limitless resource (given adequate area for farming vs food), but at present the fuels produced suffer from high viscosity at low temperatures, so may well need some further blending to produce something suitable for aircraft use.

Whatever comes in the near future is going to need to be pretty similar to avtur for ease of use in existing aircraft and supply infrastructure (which would be massive for hydrogen).

Presuming that no way of storing electric charge well suddenly emerges and solar and ground based laser power aren't sufficient, I'd place my money on something you can grow.

[Gainesy]

although it can be used to fuel aircraft engines, it has a major problem, in that it takes up around 3 times as much space to store enough to go, say 100 miles, as it would to store enough petrolium based fuel to go the same distance.


Getting back to aircraft, I've got this picture forming of a fleet of Zeppelins inflated by hydrogen, which is also the engine fuel so they, erm.. shrink as they proceed down route.:):uhoh:

[taxydual]

Ah, I knew the grown-up's would come along.

You've certainly given this bunch of geriatrics (starved of cricket) something to debate in this corner of North Yorkshire.

I'll pull a few more corks to 'fuel' the exchanges.

:ok:

[Yeoman_dai]

I thought Pprune was starved of debate recently taxydual ;)

It's good to know about this, it's always been a question of mine. Maybe I had in mind a return of prop planes and gun dogfights :D

Keep 'em coming chaps.

[Gainesy]

Who are you calling a grown up?:suspect::)

[8-15fromOdium]

A bit of back to the future here, but according to this article (http://www.technologyreview.com/energy/16650/)the US are looking at coal, something the Germans had a look (http://en.wikipedia.org/wiki/Lippisch_P.13a)at in the last days of WW2. Thanks to Mrs T we still have lots of the stuff!

[Chugalug2]

8-15 etc:

US are looking at coal

"Are you quite mad, Captain? I'm telling you the noo, you'll not get another pound of steam out of these boilers, d'you ken?".
Sorry, Hat, Coat, P45....

[Double Zero]

Gainesy,

I'm trying hard not be a smartarse but have succumbed - surely semi-rigid airships don't inflate or shrink via Hydrogen ?

I'm reliably informed by someone who would know ( senior Rolls Royce aero-engines man ) that for example the Speys on the UK Phantom were cleared to run on coal dust.

Not sure what form the coal dust was in, as we had to break off our conversation.

If wearing a ' green ' badge, one must comment that all fossil fuels will run out sometime, the only question is whether coal or similar gives enough breathing space before a more intelligent power source comes along - for the medium term, " fuel you can grow " sounds about right to me.

As for Hydrogen, must have potential but you go first, and keep the ' no smoking ' sign on, also steer clear of static / lightning !

[Top Bunk Tester]

As Hydrogen is many times lighter than Avtur, and even lighter than air, it won't matter if it takes up 3 times as much space, as being lighter than air it will assist in the lift of the aircraft and you will save on the weight of the Avtur. ;)


Hat & Coat on, heading for the door

[Double Zero]

Isn't that only if it's in gaseous, not liquid form ?

No idea how the two liguids compare weight wise, but I have a nasty feeling Hydrogen will end up heavier, allowing for containment conditions.

[Top Bunk Tester]

I really should take up fishing, 11 mins from flash to bang:p

[ORAC]

Maybe NERVA (http://www.astronautix.com/engines/nerva.htm) will make a come back? :8

http://www.epower-propulsion.com/epower/gallery/new%20gallery/Nuclear/nerva.jpg

[Yeoman_dai]

ORAC, in my honest opinion, I really don't think that would make an effective short ranged air to air missile...

[ImageGear]

Already Happening;

Been making the stuff in Sarf Ifrica for donkey's years - it's what happens when the plug gets pulled on your essentials.

C-17 flight uses synthetic fuel blend (http://www.af.mil/news/story.asp?id=123073293)

Imagegear

[Double Zero]

When I want my essentials pulled I have someone more suitable in mind, Ta !

As for fishing, Top Bunker, I was only hoping you were, rather than test flying such kit...

Back to serious, before I can contact my chum again, does anyone know what form jet engine coal dust comes in ?

I'm not likely to use it, just curious.

[brokenlink]

Having seen some of the cr@! come out of the back end of a Toon over the years I thought they were running on coal dust!

[HighTow]

A bit of back to the future here, but according to this article the US are looking at coal, something the Germans had a look at in the last days of WW2. Thanks to Mrs T we still have lots of the stuff! I recall reading somewhere that the National Coal Board labs at Stoke Orchard were doing something like this in the 60's/70's with a view to powering Concorde with it.

[green granite]

An article about a coal fired Cadillac built in 1978: http://www.nytimes.com/2009/01/04/automobiles/04COAL.html?pagewanted=all

[Airborne Aircrew]

We all know that soon, the worlds supply of oil will run out, or at least become so expensive to get out of the earth that drilling becomes pointless. At this point, we must stop using Aviation Fuel.

No we don't "all know". Please provide the source of that little tidbit...:rolleyes:

[Airborne Aircrew]

if all countries consumed oil on a per capita basis equal to that of the United StatesBut they don't do they? You probably haven't spent any time trying to determine the political leaning and/or funding of said esteemed institution either.

For a first post that could be best described as naive.

[Fareastdriver]

We all know that soon, the worlds supply of oil will run out,

I seem to remember the same statements coming out in the seventies. From what I know, after thirty years in the business, the problem will not effect us, our children or our grandchildren.

[Donkey497]

Alcohol is probably a more viable fuel currently. It's readily transported by existing infrastructure, can be brewed relatively easily by existing Infrastructue. Like current AVTUR, it clould even be designed to pretty much put out a naked flame, rather than be consumed, as happens currently for bulk liquid sprayed onto a flame.

Hydrogen - Leaks too easily, Aluminium & high strength Steel are embrittled by it, it needs low temps or high pressure to liquify it & it's not got an inherently high energy density when liquid in any case. Liquifying it is very energy intensive & would need a lot of infrastructure put in place to handle it. So not too great a solution at present.

Coal Dust. Any hydrocarbon or carbohydrate in powder form can be used to run a gas turbine, but it is normal to blow the dust into the turbine using the combustion air immediately after it is pulverised. Not something that is readily adapted to an airborne set up. Pre-pulverised fuel in dry form also has a significant danger of explosion in the presence of static electricity and a fairly big tendency to clog up when it gets damp - both hazards & facts of life at 35000 feet.

Unless of course we can get fusion power to work, at small scale and be safe, reliable and radiation free.

I think we already know the winner in the short term.....

[drustsonoferp]

I seem to remember the same statements coming out in the seventies. From what I know, after thirty years in the business, the problem will not effect us, our children or our grandchildren.

"Soon" as used here is potentially misleading, but as worldwide hydrocarbon use is still increasing and current estimates put peak production in c10 years or so, I'd say that is certainly soon enough to worry about.

We have an existing infrastructure eg for fuel for cars that cannot be changed overnight and we're reliant on our ability to use that infrastructure. If it must change to something entirely new it will have to begin changing in the rather near future.

Presuming that there will inevitably be things we cannot live without or easily change our sources for, the remaining hydrocarbons will need to be carefully assigned, and so movement away from non-renewable sources should be encouraged sooner rather than later.

I think the ultra high fuel prices of the other year probably did more for environmentalism than years of campaigning: people sharing cars more; buying smaller cars; driving more slowly to economise; tyres sold to promote efficiency; people (anecdotally at least) driving less often; sales of small but significant numbers of electric lorries for use in cities. And all this in the space of about a year to save the contents of their back pocket.

I'd love to see a big push on electric cars, but our current electricity supply will not cope with mass demand.

[Airborne Aircrew]

I'd love to see a big push on electric cars, but our current electricity supply will not cope with mass demand.

Unless you can move to a nuclear based infrastructure for the generation of electricity, (which has already been sufficiently demonized by the loony left), then, (as the loony left fail to comprehend), electric vehicles don't save carbon emissions they simply transfer the emissions, (and therefore everything the "Greens" whine about), to a big power station somewhere else. But far be it from me to point out that they can't understand that it takes the same amount of energy to move a given mass a given distance and that energy, (be it created in a distant power station or an internal combustion engine within the vehicle), required to do so is the same. But if the car seems cleaner then the idiots are happy I suppose... :ugh:

[Wander00]

Post 33.

Always been my argument: the only way of being more "green" is making the conversion from fuel to electricity more efficient-I am not sure that is the case with electricity generated centrally from carbon sources and then distributed - there must be inefficiencies at the power staion and across the transmission system, probably as great if not greater than those between the engine and transmission of a road vehicle. Mass (ie public) transport is obviously more efficient, but does not solve the bits of the journey beyond the terminus, which is why we all like the car so much.

[cockney steve]

As told to me by a Chartered Engineer,who used to run power-stations........ the way forward is Nuclear, coal-fired is around 45% efficiency,max. All other fuels have their drawbacks.......Nuclear has high efficiency and high power-density. whilst it is unarguable there is a "legacy waste" problem, the UK has underground storage in the Cheshire salt-mine workings that are safe, secure and could not concievably be filled during the existence of the human race.
fossil fuels are finite, including Gas, renewables would need ridiculously large tracts of cultivation and a huge transport infrastructure to feed the generator (notice how the much-vaunted coppice-Willow fired "future" has gone quiet?)-- likewise the wood-fired idea, to be fed with waste-wood carted from Canada :uhoh:

Coal is high-density wood-in the same way that a Transit-van of spuds will make an Artic. lorry-load of crisps, so a (possibly) 20-fold BULK VOLUME of wood is required in place of coal.

Windpower is the biggest con perpetrated the world's current installation will ALWAYS show a net energy-loss, even before scrappage and restitution of the environs ruined by the masts, foundations and infrastructure.

Photovoltaic depends on a more enviro-friendly Cell being invented and more efficient storage-media (Li Poly cells are a large leap forward, but there's a long way to go yet.

I do not disagree with the need to prioritise our uses of dwindling finite resources,but we're nowhere near crisis-point yet.

when "Big Oil" forms a research association to develop alternatives AND pours in serious money, THEN those alive at that time, need to start worrying.-meanwhile,carry on as normal.
Big Oil will manipulate demand via price,in order to maximise their "take"-a lesson the Arabs learned in the 60's