Are practical aircrafts dependent on carbon-based fuels?

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In summary, aerospace engineers are currently working on finding alternative long-distance travel systems due to the limitations and environmental impact of carbon-based fuels. Hydrogen and oxygen fuel has the best energy-to-weight ratio, but the challenge lies in its low density and potential safety hazards. Other potential fuels being explored include diborane and Fischer-Tropsch synthesis. In the past, the Russians have flown a nuclear-powered bomber, but the environmental and safety concerns outweighed its potential benefits. Some private planes have been successfully flown using battery power and the next step is to incorporate fuel cells for improved efficiency.
  • #1
Gonzolo
Is it concievable to build passenger, cargo and military aircrafts that run on something other than petroleum? I suspect electricity is out of the question because of the weight of batteries, but what about hydrogen? How does the the weight/energy ratio of hydrogen systems compare to that of common gas-kerosene engines?

What will aerospace engineers be working on when the world oil supply runs low?
 
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  • #2
Hydrogen/oxygen fuel has the best energy/weight ratio of just about any fuel (with the possible exception of aluminum/magnesium, but I'm not sure...). The problem is the density. Liquid hydrogen and oxygen are not very dense and as a reasult, require large fuel tanks. As first proposed, the SR-71 was going to be hydrogen fueled...and 300 feet long.

But there may be ways around this.
 
  • #3
I just checked that a 747 is about 150 feet long. The challenge to find alternative long distance travel systems seems quite interesting.
 
  • #4
Fuels for aerospace; Fischer-Tropsch Synthesis

Are practical aircrafts dependent on carbon-based fuels?

Simple answer - yes. Primarily based on specific energy (i.e. heat of combustion per unit mass) and properties such as low vapor pressure, high flash point (safety issue), low viscosity (can be transferred easily), freezing/boiling point (won't freeze), etc at the ambient (operating environment) conditions.

Liquid hydrogen would require a cryogenic system and size could be large since the density is low (as already indicated). Then if there was a leak or accident (crash) - *BOOM* - remember the Hindenburg - and that was gas.

Diborane (B2H6) would be an interesting fuel, but it's flammability/explosivity is worse than LH2. Also CO2 is much better than borates in the environment.

What will aerospace engineers be working on when the world oil supply runs low?

Well before that starts to happen, the fuel suppliers will presumably have developed synthetic fuel processes - which may be expensive - but then fuel will become 'very' expensive when supplies become limited (Economic principle of 'supply and demand').

There are already chemical processes using Fischer-Tropsch sythesis (using FTS catalysts) which are used to produce aliphatic (light to moderate alkanes) using H2 and CO/CO2. FTS was first developed by two German chemists (Franz Fischer and Hans Tropsch) in the early 1920's.

see - http://www.encyclopedia.com/html/F/FischerT1.asp [Broken]

http://themerckindex.cambridgesoft.com/TheMerckIndex/NameReactions/ONR139.htm

http://encyclopedia.thefreedictionary.com/Fischer-Tropsch synthesis

http://www.ecn.nl/biomassa/research/poly/fischertropsch.en.html [Broken]
 
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  • #5
The Russians flew a nuclear fission powered bomber a few times. It had conventional jet engines as well for take off, but could cruise on nuclear power alone.

The problems were the pollution of the environment, and the difficulty of engineering sufficiently lightweight radiation shielding to protect the crew. The Russians 'solved' both problems by not caring too much about them.
 
  • #6
Another thing: How would they cool the thing? I don't know much about nuclear reactors, but according to what I do know is that they use the heat to evaporate a liquid (H2O) and pipe it through a turbine. But where would they get enough water from? A huge air cooling system for liquid recycling would've generated extreme amounts of drag! Am I missing a different way of turning power from a reactor into torque or thrust?

And an irrelevant aviator remark: I'd rather stick with my carbureted reciprocating Lycoming, even if you threw a gas turbine at me. AVGAS100LL is a safe, reliable fuel, and recip engines are very agile, yet economical for light aircraft.
 
  • #7
ceptimus said:
The Russians flew a nuclear fission powered bomber a few times. It had conventional jet engines as well for take off, but could cruise on nuclear power alone.

The problems were the pollution of the environment, and the difficulty of engineering sufficiently lightweight radiation shielding to protect the crew. The Russians 'solved' both problems by not caring too much about them.
Do you have a link to that? I knew the US flew a bomber with a nuclear power plant inside, but the plane was never powered by the reactor. It just flew around on its regular jet engines with a reactor in the back reactoring away. This was to prove that we could, in preperation for a nuke-powered aircraft.

I didn't know someone had actually flown on reactor power. However, I do know of a small private plane flown on battery power (the batteries from a Prius, I believe). The next step the inventors plan is a feul cell.
 
  • #8
LURCH said:
However, I do know of a small private plane flown on battery power (the batteries from a Prius, I believe). The next step the inventors plan is a feul cell.

Do you have a link to that?
 
  • #9
LURCH said:
Do you have a link to that? I knew the US flew a bomber with a nuclear power plant inside, but the plane was never powered by the reactor. It just flew around on its regular jet engines with a reactor in the back reactoring away. This was to prove that we could, in preperation for a nuke-powered aircraft.
I can't find much on line about this, but I saw a documentary on Discovery about it.

The documentary focused on the history of the B-36 (the American nuclear testbed that you described). At the end of the program was the 'shock news' bit - Russia had actually flown about 50 nuclear powered flights - not just tests with airborne reactors - back in the 70s. They saved weight from the planes by fitting only minimal radiation shielding. The crews had been selected from older air force members - they had all been badly irradiated, and only one member (I think) from all the crews was still surviving.

Maybe Discovery were hoaxing, or had been hoaxed themselves? Perhaps I have misremembered this - though it seems a pretty clear memory to me. Does anyone else remember seeing this program?
 
  • #10
Batteries would provide a horrible power to weight ratio and poor endurance. A fuel cell, on the other hand, would probably be far superior to a conventional engine on a small plane. But it isn't without its problems.
 

1. How are practical aircrafts dependent on carbon-based fuels?

Practical aircrafts are dependent on carbon-based fuels because they provide the necessary energy to power the engines and generate thrust, which allows the aircraft to achieve lift and fly.

2. Are there any alternatives to carbon-based fuels for aircrafts?

Currently, there are no viable alternatives to carbon-based fuels for powering practical aircrafts. However, research and development is being conducted on alternative fuels such as biofuels and electric propulsion systems.

3. How do carbon-based fuels impact the environment?

Carbon-based fuels emit carbon dioxide (CO2) and other greenhouse gases when burned, contributing to global climate change. They also release pollutants such as nitrogen oxides and particulate matter, which can have negative impacts on air quality.

4. Can we reduce the dependence of aircrafts on carbon-based fuels?

Efforts are being made to reduce the dependence of aircrafts on carbon-based fuels through the development of more fuel-efficient engines and the use of alternative fuels. However, completely eliminating the use of carbon-based fuels for aircrafts is not currently feasible.

5. What are the challenges in transitioning to alternative fuels for aircrafts?

One of the main challenges in transitioning to alternative fuels for aircrafts is the development of a reliable and cost-effective supply chain. Additionally, alternative fuels may not have the same energy density as traditional fuels, which can impact the performance and range of the aircraft.

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