Mass Efficiency?

[rakutenshi]

I'm trying to work out a general formula for figuring out the optimal payload:liquid fuel ratio, so far I've got that for ideal TWR (~1.7 at launch), that's somewhere around 800-850. Not counting discarding stages or SRBs, I've got some other numbers floating around but the spreadsheet is an absolute wreck while I futz around with it, does anyone else have information that would pin down the ideal Payload:LF ratio for an SSTO rocket? (I realise it's less for a staged rocket, due to the shed weight of the previous stages.)

Crap, sorry .. half asleep been staring at numbers didn't realise what forum it was in...

Edited May 21, 2013 by rakutenshi
oops

[numerobis]

What are your units? Usually one calculates payload mass compared to total mass at launch; the best multi-stage rockets get just over 15% payload, whereas air breathers often expend 10% of their mass or less (which only counts fuel, not engines).

[Akalaël]

This was discuted a bit ago :

http://forum.kerbalspaceprogram.com/showthread.php/28248-Is-asparagus-the-best-staging-system-(might-contain-science)

[Specialist290]

Nyrath worked out the following equation over on his Atomic Rockets site:

P_e = 1 / e^{(ÃŽâ€v/V_e)}

Where

P_e = Ratio of dry mass to wet mass, expressed as a percentage

He goes into the math a bit more on the website, if you want to follow his logic.