[FoRK] LA Traffic - solution?

Eugen Leitl eugen at leitl.org
Sun Sep 2 08:31:36 PDT 2012


On Fri, Aug 31, 2012 at 07:14:10PM -0700, John Parsons wrote:

> >"Although only barely possible for even 2 seaters, the possibility of electric jets..."
> 
> Contradiction in terms. For an engine or other device to produce a true "jet" for propulsion, some chemical or combustive process is required. If you are alluding to ducted fans driven by electric motors, they cannot be construed as true "jets". While this tech is used in RC modelling, the tech is a long way from prime time.

I think they're thinking about making electric equivalent of the turboprop.
The main problem with that is you'll need high-performance fuel cells
capable of dealing with high-density hydrocarbon fuels or at least onboard
reformed hydrocarbon fuels.  Or you could just use Sabatier on ground,
using renewable electricity and carbon capture from air or biomass, and
hydrogen from water, and use cryogenic methane for fuel.

Notice that even nonpropulsion onboard fuel cell use can potentially
provide 15% of fuel savings

http://www.technologyreview.com/news/428693/fuel-cells-take-to-the-runway/
 
> For electrically powered ducted fans to be prime movers, we would need to replace the heavy iron and copper in traditional electric motors with lightweight and electro-magnetically conductive materials, to say nothing of the weight of the on-board storage (presently batteries, but possibly super-capacitors in the future). AFAIK the most efficient possibilites for electric airplanes continues to be propeller driven tech.

I think carbon nanotube cables could make a major difference for
lightweight cabling and motors (self-exciting motors can be pretty
light), and with use of cryogenic fuels like hydrogen and methane
you could use superconducting materials.
 
> Still, I've been out of that particular field for some time now, and while the physics hasn't changed, inventiveness continues. Am I seriously out-of-date or was this a typo?


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