[AR] Re: Zubrin,

  • From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
  • To: Arocket List <arocket@xxxxxxxxxxxxx>
  • Date: Wed, 28 Aug 2019 14:32:42 -0400 (EDT)

On Wed, 28 Aug 2019, Uwe Klein wrote:

So, all other electric-propulsion things being equal, in terms of
overall efficiency of converting electrical energy in to thrust energy
out, the ionization energy requirement favors  heavier atomic-weight
propellants and higher isp's.

What do I get from putting a charge on fine dust?

A much better mass/charge situation, and major headaches with propellant feed and injection.

The more tractable version of this is to use fine droplets of a low-vapor-pressure liquid. This is the colloid thruster, or electrospray thruster; it's been in the "promising but needs more development" category for half a century or so. There's been renewed interest of late, and maybe eventually somebody will actually fly one.

You obviously have to increase acceleration time/length
due to less applyable force per mass.

The simple solution is to crank up the accelerating voltage a lot.

Henry

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