(Iain McClatchie) wrote in message om...
One nice thing about that pump design that I don't see mentioned on the
website is that, although you need as much pressurant as you would if the
main tanks were pressurized to the pump delivered pressure, you vent most
of that pressurant on the way up, and don't need to accelerate it.

Another advantage over pressure fed is that condensation is not much
of a problem. In a pressure fed it will lead to a pressure drop in the
tank but on this kind of pump the pressurant is only used for a short
time before venting. This makes it possible to use a gas generator
output with relatively large amounts of water vapor.

Is a dual pump really necessary? A big buffer tank to smooth the flow
may make it possible to use a single piston tank. The ullage in this
buffer tank will need to be several times larger than the piston
stroke to keep the pressure fluctuations under control but it can save
a lot of plumbing and valves. It may be an overall win in complexity
and perhaps even in weight.

Oren