Could biofuel, hydrogen, electric or solar replace jet fuel?

[nec209]

With the technology we have today supersonic travel is way way way way too costly for the public. Could a supersonic plane running on biofuel, hydrogen, electric or say solar replace jet fuels to lower the cost of supersonic travel? Making supersonic travel possible?

I know they are doing research and experiments now on electric planes and solar planes now but it still not ready for a replacement of jet fuel.

May be in 10 years from now they will start phasing out jet fuel for biofuel, hydrogen, electric or solar? And we will have supersonic planes.

[Elite Engineer]

The only two potential candidates I see here ate biofuel and electric. I dont think were ever going to have enough research or support for hydrogen fuel. It requires a completely different set up for the engine design.. and other stuff.

 

Solar heavily lacks in efficieny, and just overall output. The way I see it, biofuel and electric are the best candidates..

 

Biofuel is renewable, consistent with the curret fuel and wouldn't alter the aircraft design. Electric has a stable research fund relative to hydrogen, and will probably be looked into more b/c of that.

 

~EE

[Endy0816]

At least a few years ago there was research into supersonic biplanes which might reduce the energy demands and the sonic boom issues.

 

One of the main issues was that people didn't seem willing to pay for the added energy costs to cover the same distance in a shorter time span. I'm not sure that part of the equation will change any regardless of the fuel source.

 

Should note that jet fuel is not restricted to use in supersonic planes.

http://www.wired.com/2012/04/when-diesel-wont-do-toyota-uses-jet-fuel/

 

There's already biomass based synthetic jet fuel out.

https://www.asme.org/engineering-topics/articles/aerospace-defense/new-options-emerge-for-aviation-fuel

 

Navy also managed to produce jet fuel via sea water.

http://www.zmescience.com/research/us-navy-synthetic-jet-fuel-seawater-0423432/

 

Keep in mind that the energy stored in the fuel always needs to come from somewhere. Main issue people run into.

[Sensei]

It's not a matter of research or support.

Hydrogen fuel requires Oxygen.

Do you want to take it also on board of airplane, or like in currently existing jet engines, take from air.. ?

Then compare energy density per liter of different fuels, paying special attention to liquid Hydrogen:

https://en.wikipedia.org/wiki/Energy_density

Not without a reason rockets look like flying cisterns.

Edited July 10, 2015 by Sensei

[aabradley01]

remember also that they use hydrogen in space shuttle launches. sometimes they use solid fuels as well. We could use the same thruster setup for aircraft but it would require special device to slow burn time and another set of thrusters on the front . Idk I'm just wondering if it's a possibity.

[Enthalpy]

Hydrogen can fly aeroplanes at subsonic speed, using fuel cells meant for cars and electric motors. I describe there

http://www.scienceforums.net/topic/73798-quick-electric-machines/#entry738806

how to build the tank for liquid hydrogen, which takes little volume thanks to the fuel cells, and give some examples or aeroplanes.

 

Whether the fuel can be cheaper than kerosene... Presently not. Kerosene is dirt-cheap (untaxed, nearly a by-product of gasoline and Diesel oil, and airlines let countries and companies compete for the market), while hydrogen is produced from gas. The smaller hydrogen mass consumption may favour it a bit, but I guess it stays more expensive than kerosene. Through some progress, I don't know.

 

The immediate advantage I see to hydrogen is not cost but silence and range - check the figures I give in the other thread, even before any stretching.

 

Would it fit supersonic transport? I vaguely plan to check that, but I don't know when. Fuels cells powerful enough would be heavy.

Edited July 17, 2015 by Enthalpy

[nec209]

I would appreciate if anyone could elaborate on that and also what kind of technological breakthroughs are needed to make supersonic affordable? The Concorde was too costly for the average person.

Do they need better jet engine, fuel efficient engine, other fuel source that is cheaper than jet fuel like biofuels like burning grass, corn, tree branches, dead tree leaves, hay so on.

Or is the cost of jet fuel not the main reason supersonic travel is more costly than non supersonic travel?

Better jet engines or fuel efficient engine lower the cost?

I hear they are doing some research into biofuels and better jet engines.

 

 

 

People that travel don't want to spend over $1,000!! So there would need to be technological breakthroughs are needed to lower the cost of supersonic travel to price $300 to $500 , a better jet engine, fuel efficient engine, other fuel source or new materials or they way the plane is build.

[John Cuthber]

The simple problem is that going faster costs more.

You have to move the air out of the way of the plane. The faster you do that the faster you have to move the air. But accelerating that air takes energy so the faster you go the more energy you need.

Since you have to pay for fuel to provide that energy it's more expensive to fly fast.

There's an even bigger problem when it comes to supersonic flight- you have to effectively ram the air out of the way. this takes even more fuel.

New designs of engine or whatever are not going to help very much.

[MigL]

Like John says travelling faster will always require more work, and therefore more energy expenditure.

There is however a steep rise in drag in the region M=0.98 to 1,2 ( somewhat mitigated by Whitcombe area ruling ), so that most modern jets will need 'afterburning' to pass through this 'barrier', but will happily 'supercruise' on military power alone in the region M=1,4 to 1.8. This is the sweet spot, as drag climbs high again and requires afterburning or re-heat which will burn two if not three times more fuel for a typical supersonic turbofan engine. Incidentally the Concorde used RR Olympus turbojet engines designed in the late 50s asnd required afterburning for any supersonic flight, but was limited to subsonic over land because of sonic boom issues.

New research into adaptive cycle engines which can vary the bypass flow according to different flight regimes will increase efficiency/reduce costs still further while aerodynamic research by Boeing, LM and Nortrop-Grumman have reduced the boom problem enough to allow supersonic flight over land.

I predict a new supersonic airliner, if not business jet, within the next 20-30 yrs.

 

Incidentally in the 50s, the hayday of aerospace innovation, many alternate fuels were looked at including Hydrogen, by Lockheed's Skunk Works, The most interesting ( but dangerous ) was Borane for hypersonics.

[Enthalpy]

The Concorde flew at Mach 2 which needs much thrust. A better speed for economy is the soft spot around Mach 1.3, where the necessary thrust is but stronger than at Mach 1. Mach 1 needs much more thrust (which converts into energy for the same distance) than Mach 0.7, which is the present-day soft spot used by every long-haul airliner.

 

Biofuels cheaper than kerosene are presently wishful thinking, alas. When taxed as little as food, biofuels can compete with gasoline taxed at 400%, but kerosene isn't taxed or very little. If no-one has found a solution for cars, the sub-tiny prospective market of supersonic airliners has zero chance to do it better.

 

Better engines... Obviously this is a key, but how? Manufacturers invest huge money in better Mach 0.7 engines, hypothetic supersonic airliners can't invest that amount. It will remain an adaptation of engines for fighter jets - which did improve since the Concorde for sure. But not only does more speed need more thrust: supersonic flight demands other choices (delta wing instead of wide wingspan, low dilution engines, narrow body...) that are inherently worse. The L/D drops from 30 to 5 or less, ouch. I'll have a look at fuel cells (the weak point), hydrogen and electric motors - some day.

 

The other killer of supersonic airliners is the sonic boom. It prevents supersonic flight over most continents (except Siberia, Antarctica and few more places). If speeding only over the oceans, the plane would be slow on all routes via the Arab peninsula, Hong Kong - an awful many ones. (Much) research was made to reduce the boom but didn't bring (by far) the necessary amount of improvement.

 

One good point is that a plane made for Mach 1.3 can be designed to fly at Mach 0.7 more or less decently, while Mach 2 is less compatible with subsonic performance. If decent Mach 0.7 flight is necessary (I fear so) it may demand a variable geometry wing, nothing easy nor lightweight nor cheap.

[Enthalpy]

The F-111 has a variable-sweep wing that looks really efficient, achieving L/D=15,8 at best subsonic speed. Maybe the mass and complexity are acceptable for an airliner. Present M=0.85 airliner achieve ony L/D~22 at their optimum cruise, for comparison; Concorde offers just 11.5 @M0.95 and 7.1 @M2.0 and is bad at take-off (no abort possible) and landing. While a fixed swept-wing may suffice for M1.3, the variable sweep must bring a lot for M2.0.

 

I've put there some figures about a hydrogen-powered M1.3 airliner

http://www.scienceforums.net/topic/73798-quick-electric-machines/#entry878522

and it looks neither feasible now nor interesting - as opposed to slower planes.

Edited August 2, 2015 by Enthalpy

[Eclipse]

Given the climate emergency we're in, I'm just interested in whether we can use nuclear power to economically replace normal airline jet fuel with anything!

 

I know it is technically possible to crack water and mix it with CO2 derived from the atmosphere, but the links above were describing military applications. Any fuel cooked up in the field has economic and strategic advantages. Fuel convoys are a major point of military expense and are vulnerable to attack. DARPA studies all sorts of energy efficient strategies, like energy efficient solar tents with insulation which cost far more than the average tent, but far less in a military camp. It's the logistics of getting fuel into a hostile situation that costs so much! Running a convoy means crazy prices like $300 a litre and a certain number of lives if in a hostile arena.

 

So jet fuel from seawater + CO2 + aircraft carrier nuclear power = common sense, even if at $200 a litre or $100 a litre or $50 a litre.

But could we pay that for our airline ticket? I don't think so.

Edited August 3, 2015 by Eclipse

[nec209]

 

 

Biofuels cheaper than kerosene are presently wishful thinking, alas. When taxed as little as food, biofuels can compete with gasoline taxed at 400%, but kerosene isn't taxed or very little. If no-one has found a solution for cars, the sub-tiny prospective market of supersonic airliners has zero chance to do it better.

 

 

 

There is not alot of R&D going into Boifuels and kerosene so it more costly now. When more R&D goes into Boifuels and kerosene it will be cheaper than Jet fuel.

 

We have enough gas and oil to last 50 years from now and enough coal to last 100 years from now. So we need R&D into new fuel sources.

 

If we don't find cheaper fuel in 50 years from now even sub-sonic flights will be too costly for the middle class Americans!!!

 

We probably have enough Jet fuel to last 50 to 100 years.

Edited August 4, 2015 by nec209

[MigL]

The F-111 ( or MiG-23, Su-24, Tornado, etc ) were a product of their times.

Computing advances have enabled the design of wings which are more efficient at both subsonic and supersonic without the weight penalty and complexity of variable sweep. The F-15e, for example can do the job the F-111 used to do, much better and sans variable geometry.

The F-111 could however fly at 200 feet height and Mach 1.2. A squadron of F-111 could probably do more damage to a city, by flying at that speed and height just from the 'boom', than by actually dropping ordinance.

 

In the 1950s. there was a requirement for an atomic powered bomber which cold stay aloft for extended periods of time. This was similar to the need for vertical take-off, to minimise the need for airfields.

Convair won the contract for a bomber powered by engines using a reactor to heat/expand the air, and actually flew a reactor in a B-36 bomber test-bed. The design of the bomber and engines was finalised, but cancelled due to the impracticality of having a flight crew airborne for weeks at a time.