inefficient turbo-pumps and Isp

I am trying to understand some of the loss mechanisms in a modern
rocket engine.

In a staged combustion cycle rocket engine, there are losses in the
turbine that drives the turbo pump/s. The friction losses in a turbine
show up in the gas as 'reheat'. Since this heat is available at the
trust chamber, it should not effect the Isp of the engine?

I know that this is the case for regeneratively cooled engines, the heat
taken out is still in the loop. So its no loss.

Am i correct? Can you get away with a very inefficient turbo-pump?

Thanks
Greg

Can you get away with a very inefficient turbo-pump?

I think so, but it does need to be compact, so efficiency helps. These a
amazing machines, thousands of horsepower in a very small package.

The regeneratively cooled engine produces waste heat, effectively captured by
vaporization of fuel or oxidizer between turbopump inducer/impeller and
turbopump drive turbine. By running hot, Isp is increased.

Sorry I don't know the efficiency figures.



Yours,

Doug Goncz, Replikon Research, Seven Corners, VA
Unequal distribution of apoptotic factors regulates
embryonic neuronal stem cell proliferation

(Greg) :

I am trying to understand some of the loss mechanisms in a modern
rocket engine.

In a staged combustion cycle rocket engine, there are losses in the
turbine that drives the turbo pump/s. The friction losses in a turbine
show up in the gas as 'reheat'. Since this heat is available at the
trust chamber, it should not effect the Isp of the engine?

I know that this is the case for regeneratively cooled engines, the heat
taken out is still in the loop. So its no loss.

Am i correct? Can you get away with a very inefficient turbo-pump?

Thanks
Greg

That is the same idea that I came up with and I see no reason why it should
not work, designing even an inefficient turbo-pump is still hard because you
still have a high speed spinning piece of metal, but my conculsion is you
don't need the tight clearances an efficient design needs, and wide range of
material can be used.

Earl Colby Pottinger


--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp

In article ,
Greg wrote:
I know that this is the case for regeneratively cooled engines, the heat
taken out is still in the loop. So its no loss.
Am i correct? Can you get away with a very inefficient turbo-pump?

Yes and no. You're correct in thinking that the heat may not get lost,
although it may show up in unwanted places. More significantly, though,
an inefficient pump is likely to be a heavy pump, and pump mass can be
quite significant.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

(Henry Spencer) :

In article ,
Greg wrote:
I know that this is the case for regeneratively cooled engines, the heat
taken out is still in the loop. So its no loss.
Am i correct? Can you get away with a very inefficient turbo-pump?

Yes and no. You're correct in thinking that the heat may not get lost,
although it may show up in unwanted places. More significantly, though,
an inefficient pump is likely to be a heavy pump, and pump mass can be
quite significant.

The pump may have not be heavy, one design I thought of but never built so
you can take it with a block of salt is a H2O2/Coleman Fuel rocket. The H2O2
is fully decomposed then used to spin the turbine. The turbo-pump pumps both
the peroxide to the catalyst pack and the fuel to the combustion chamber.
Since I did not get access to the needed milling station I was unable to
build it to test the idea. The main advantages in the design are the large
clearances between the turbine blades and the housings. Comments - be
mercyless please, I may try to build it later and if you see a major flaw I
would like to know it now.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp