Would it be possible to make an electric jet?

whizzbang

I was having a chat with a friend over the weekend and we were wondering if it is possible to make an electric jet? We were in a science museum at the time and the description of a jet engine seemed to suggest it would be possible.

If it is possible could electric powered jet replace oil based fuel powered jets in the future? Assuming batteries weren't a problem!

DublinWriter

Interesting post...I've always wondered the same myself.

However, if you are thinking that some fictional nuclear fusion device could power it, then consider that the primary energy produced by fusion theoretically would be heat, so you have to convert the heat energy to electrical energy first.

whizzbang

true, also, it probably wouldn't be great to have any sort of nuclear engine crash into a mountain at 600 mph

We were wondering could fuel cells be used for power? I'm not sure they have the energy density required though.

Boston

didn't the russians have a nuclear powered jet, or at least tried to make one.

whizzbang

"In soviet Russia, jet flies you!"

yep, looks like both US and Russia did!

http://www.nuclear.com/history/Nuclear_airplanes.html

mawk

actually hydrogen cells are in theory not a bad idea, in the not too distant future they should start pumping out a lot of power. where you hit a brick wall is pollution. hydrogen cells may only kick out water vapour instead of CO, CO2, etc but it turns out that all that water suspended would do more damage in the form of both global dimming AND global warming.

so unlikely as it seems.. oil is the lesser of two evils when it comes to air travel.

also try to imagine the cost of refitting all the jets currently in use... €10^13?

nope, in any practical terms jets most likely wont change a WHOLE lot in the forseeable future

breadmonkey

mawk wrote:

also try to imagine the cost of refitting all the jets currently in use... €10^13?

Where are you getting that figure?

mawk

total guess, but i was pretty much alluding to the fact that it would cost tooo much to be worth converting any significint portion of the current air fleet. even if new elec planes appeared tomorry, its not going to make airlines replace any great number of even the 1300 ish 747s in service. and then you factor in the very very large ammount of military planes in use. point being that yes, electric planes are available assuming your power system is efficient enough. and hopefully soon that will be so. but no its unlikely that electric plane are going to become the norm.

sorry for going off track op

mawk

and sorry, i probably should have proof read that..

sme

would it not be more sensical just to retire the older fleet of planes after lets say 15yrs of use, have a scrappage deal or something, and replace them with new planes with the electric engines, assuming that the electric planes are economical and efficient.

mawk

you might think it'd be more sensible option but again, many companys are not going to pay for a whole new fleet of jets every 15 years.

thing is planes are actually built to last quite well. hell the jumbo came into service 35 years ago and there are plenty of first generation models still in commercial service.

if weight to power ratios and money were not in consideration, sure everyone would buy new jets but its just not vaible to replace the entire fleet. No doubt many companys will invest in new electric jet once they are proven but i dont think hydrocarbons are going anywhere soon.

also the airbus a380 is just coming onto the market now and since they spent so much producing it i cant see them scrapping it soon. and since many airports, including heathrow, LAX and chicago o hare have all just had to rebuild terminals to accomodate a380's i dont see the plane not selling

Red Alert

most of a jet's energy is actually the thermal expansion process that takes place (which does of course drive the turbine which turns the compressor and fan). However planes like the Mig 21 have what's called a ramjet with no moving parts. Don't underestimate the amount of power you'd need to supply to match the air thrust output of a 737, not to mention the sort of motor you'd actually need within the 'jet engine' of it.

mawk

yeah ramjets are used in some places, first wide use was the v1 missle used by germany if anyone cares.

but i dont see any way to make an electric ramjet..

it'd probably be easier to run a turboprop off a motor.

The Doktor

A ramjet wasnt used on the V1, it used a pulsejet. Its why the got the name of Buzzbombs, cos of the noise the pulse jet made. The first ramjet was on a Leduc 010 that flew in 1947(pretty cool lookin yoke). Also the Mig 21 uses a turbofan with afterburner, though it has a shock cone (to slow the air entering the engine to subsonic speeds) which makes it look as though it has a ramjet.
Ramjets cannot give thrust with zero airspeed, but have to be accelerated to get the air movin through them (different figures, but about 400mph). Usually they are launched off the back of a plane (like an SR71), or are accelerated with rockets (mainly missiles). Though there have been a few planes with a turbofan engine to get them off the ground, where the ramjet then kicks in.
The SR71 had a hybrid ramjet/turbojet engine, where when it reach high speeds the air bypasses the turbojet and goes straight to the afterburner.
You can build yer own ramjet with an aerosol and a leaf blower... ... though it wouldnt give you a lot o thrust.

One thing about electric jets, is on model aircraft, the electric jets are often as fast or even faster than the jet turbine ones using kerosene... though thats a little different..:D