Re: Rapid manufacturing

From: Kent Paul Dolan (xanthian_at_well.com)
Date: 02/23/05 

To: sci-space-tech@moderators.isc.org
Date: 23 Feb 2005 01:03:45 -0800

Earl Colby Pottinger wrote:

> PS. If I have a 3D printer that worked with metal
> I would be more interested in building a water
> cooled TPS.

> It would be ideal for the large number of
> branching feed channels needed.

I'm going to answer these in the other order.

1) You'd probably want the channels to be a lattice
rather than a tree, to provide redundant paths, and
just let the openings to the nozzle be much less
capacious than the feed channels, to meter the flow.

2) [I am not a rocket scientist, so this next may
   make no sense whatever, but then again...]

Why use water? With a complex enough channeling
available, in my ignorance I can envision a
throatless nozzle, where the fuel itself is all used
as coolant before it is used as fuel, and emerges
even perhaps from the entire interior surface of the
nozzle, or else flows in (essentially) non-cooling
channels down to the lip and then does a backflow
from lip to base before emerging, like a tuna's
retia mirabilia counter-current heat exchanger(*),
moving the heat cooled from the nozzle to where it
will most help ignition.

    This might, however, have the coolant enter the
    nozzle at really immense speed, eroding the
    pores through which it emerges, so the nozzle
    had better be cheap indeed to build, it might
    not be reusable.

Moreover, it wouldn't be any extra manufacturing
complexity once you have 3D "print to build"
technology as your base, to have the channels be two
separate but interwoven sets, unconnected
internally, and to have the oxidizer and fuel emerge
and mix at the nozzle interior surface.

I suppose one would need something the moral
equivalent of a glow plug at the top to set things
going and keep them going, which would make for an
attractive restartable engine, too.

FWIW

xanthian.

(*) http://www.the-aps.org/press/conference/tuna.htm