Flometrics has ambitious rocket plans

[baldusi]

I am at a loss as to why a propellant pressurization system so much less expensive than turbopumps and with equivalent performance and likely better reliability has not seen commercial development.

Any speculation?

Are you sure of those statements? have you given it thought to what happens to the "smoothness" of the pressure flow and how would that affect a controlled deflagration that is a liquid rocket main combustion chamber?

[HMXHMX]

I am at a loss as to why a propellant pressurization system so much less expensive than turbopumps and with equivalent performance and likely better reliability has not seen commercial development.

Any speculation?

Are you sure of those statements? have you given it thought to what happens to the "smoothness" of the pressure flow and how would that affect a controlled deflagration that is a liquid rocket main combustion chamber?

And in the last ten or so years TPAs have gotten ridiculously cheap.

[S.Paulissen]

This thing looks like POGO instability hell at scale.  But I'm no aerospace engineer.

[mmeijeri]

And in the last ten or so years TPAs have gotten ridiculously cheap.

In addition, if I understand it correctly, dealing with hot gas is what makes turbines difficult and dealing with very cold and low-density LH2 is what makes pumps difficult. A low temperature gas turbopump for LOX, kerosene or methane should be much cheaper than a turbopump for a LOX/LH2 gas generator / SC engine. That's why I was wondering about a compressed air (or helium) turbopump, as it seems like a far more straightforward, almost off-the-shelf solution compared to a pistonless pump.

[tdperk]

This thing looks like POGO instability hell at scale.

Actually the pump chamber inlet valve is just a check valve.  It can't seat until pressure equalization across the orifice it represents to the propellant flow sees no pressure drop--which can only be true when there is almost no flow.

So not only no POGO, it is an immense damper to POGO.