The Silent Observer wrote: > Randall Clague wrote: >>We're on the same page. What I'm asking you is, to which capability >>number shall we apply Moore's Law? Altitude? Delta-v? Mass >>fraction? Total impulse? Each will yield a different answer. > > To disagree with Ian a bit, ISTM that Delta V is the factor that can be > increased by actual engineering; Isp is a matter of propellant choice > and making the engine last long enough for your burn (or your reuse > cycle), and has pretty well known limits for any given propellant > chemistry.
Well known theoretical limits. In practice, it's not so easy to achieve 100% of the theoretical ISP limit; engineering is required to realize a good (and then better) percent. Higher delta V can be realized by simply taking along more fuel and accepting a poorer mass ratio (and higher costs): a 100 kg payload on a rocket with a 10,000 kg fuel tank vs. a 100,000 kg fuel tank is still the same payload. > Altitude increases wildly with relatively modest increases > in Delta V. Mass fraction is good, but translates very directly into > Delta V; in fact, it's Delta V that gets you anywhere. A huge mass > fraction with peroxide monopropellant still won't get you to orbit, and > an Isp equivalent to 10 km/s effective exhaust velocity won't help you > if the engine is so heavy you only have a 30% mass fraction. Doesn't the ISP - at least, as measured in practice - account for the weight of the engine? _______________________________________________ ERPS-list mailing list [EMAIL PROTECTED] http://lists.erps.org/mailman/listinfo/erps-list
