Hans said :
> Savary had also two pumping systems working in parallel as can be seen on
> the pictures.
Missed that in my quick look. That would give Lockheed's patent a shakeup on
basic principles.
> His patent went even further as it covered the principle of rising water
with
> the force of fire.
Yes. Not quite relevant here :-)
> Personally I`m not so enthusiastic of the use of the principle for biprop
rocket
> engines. To bring the weight and volume down the cycling has to be fast.
Depends on many factors, and Steve Harrington has detailed calculations
available on his site that show it can provide performance as good as
turbopumps in some operating ranges. (eg if you want to run at 3000 psi + a
turbo pump will have the edge).
> That can give problems as there can be some mixing of propellant and
driving gas
> or some spilling of propellant with the exhausting gas.
> I would go for a free piston pump, where we have a strict separation
between
> the propellants and the driving gas.
I see those as more engineering issues. You can have floats or loose seals
or even flexible diaphragms between the fluid and the gas. None of this
violates the PPP basic principle as long as pressure is essentially
equalised across the interface. The common lowish pressure diaphragm pumps
which may seem at first glance to be equal to the PPP are not mainly because
the diaphragm is a true pressure seal and is really a flexible piston.
> To keep the O/F at a precise level one
> could link each oxidiser piston with a fuel piston. If we can not have a
exact
> O/F over the burning time one propellant will run out before the other and
> the effective mass fraction is reduced.
Linking chambers and adding pistons will tend to end up back with a true
piston pump.
While a true piston pump is positive displacement as you describe above, it
is not normally considered necessary to have positive displacement pumps in
this application. A turbopump isn't one. By regulating pressure you can
probably balance propellant flows as well as you need. With the PPP the flow
rate for each fluid can be adjusted independently - even allowing mixture
ratio variation if desired.
When are ERPS going to start using a pump like this :-) ?
Russell McMahon
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