On Thursday, June 4, 2015 at 12:17:49 PM UTC-7, J. Nieuwenhuize wrote:
Multiple engines (especially for self-launch) make a lot of sense since price scales neatly with thrust.

2X 230N thrust for a light single-seater, or 2X 800N for an open-class ship would allow a self-launcher with acceptable cruise fuel consumption and self-launch capability.

That's close to what I came up with when investigating for a single seater. You would probably want to carry at least 15 gallons of fuel for the single. Interestingly, when you throw in oil and anti-static, the runtime cost are quite high. You end up finding how economical the old fashioned internal combustion self launch really is. It accomplishes quite a lot with 4 or 5 gallons.