Of missiles, and hydrogen...
 

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.

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

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

Red wine?
Not sure of the practicalities though.

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 !

:\ 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.

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.

Thank you Easy street! :ok:

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, it just makes it a bit more expensive.

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.

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:

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:

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.

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

Coal?
 

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!

8-15 etc:
"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....

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 !

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

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.

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