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. 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.
Assuming KISS II had a Delta V of around 400 m/s (subsonic plus gravity
losses for that 6500' flight -- and it's a guesstimate), will KISS III
be capable of 800 m/s? I'm thinking not, since AIUI the only change is
constant pressure instead of blowdown -- but even if doubling takes two
years instead of one, Delta V is the parameter by which to measure,
since a Delta V of about 13 km/s will get you pretty much anywhere in
the Solar System (assuming you don't mind waiting for slingshot
maneuvers). The goal is clear; the question is, when can ERPS get
there?
--
Love wealth above life itself, and starve in splendor.
-- Elvish proverb
Donald Qualls, aka The Silent Observer NAR # 70141-SR Insured
Rocket Pages http://silent1.home.netcom.com/launches.htm
Telescope Pages http://silent1.home.netcom.com/astronomy.htm
Lathe Pages http://silent1.home.netcom.com/HomebuiltLathe.htm
Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.
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