20x cost savings may be a little aggressive: there isn't any significant
mechanical or materials difference between valves using those two oxidizers.
Insulation is very cheap; at most you might want a slightly more powerful drive
for Lox, just in case.
Bill
Sent from my Commodore 64
On Sep 6, 2016, at 4:41 PM, ignacio belieres <ignacio_belieres@xxxxxxxxxxx>
wrote:
Henry,
Well if you accept the correlation that cost tends to go up with
dry mass, and that volume is in a direct relationship to dry mass, then using
a smaller vehicle for a same payload will reduce cost. The difference is even
more pronounced than that because with a room temperature liquid propellant
you dont have to deal with cryofluids, prechills, cryovalves, insulation,
reaally good thermal control, lox vents, and extra annoying stuff. A peroxide
compatible 1 inch ball valve will probably be 20 times less expensive than an
equivalent Lox valve.
IB
Date: Tue, 6 Sep 2016 14:31:25 -0400
From: hspencer@xxxxxxxxxxxxx
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Issues with operating at low chamber pressure
On Tue, 6 Sep 2016, Troy Prideaux wrote:
Anyway, it turned out the combination producing the lowest Isp actually
produced the highest delta V return primarily due to the respective
densities on offer which directly affected the respective mass ratios for
the volume fixed analysis...
There are occasional observations going back to the 1950s about how denser
fuels often seemed to produce higher performance in real rockets, even if
they incurred an Isp penalty.
That said, any constant-volume analysis is going to be somewhat biased in
favor of denser fuels, in the same way that any constant-gross-mass
analysis is going to favor the highest possible Isp: the conditions of
the analysis have stacked the deck somewhat. The yardstick that's really
of the most interest is not volume or mass, but cost -- defined broadly,
to include issues like operations difficulty as well as cash outlay -- but
that's harder to estimate well for a paper design.
Henry
