Doing the science, nickel makes far more sense over SS because of
superior heat transfer properties and, as aforementioned, Rocketdyne used
nickel in many of their
TCA's and injectors. Copper was used for some injectors like the F-1
because the thicker web of such a large engine required the absolute best
heat transfer properties. Now the chamber wall can tolerate inferior heat
flux materials like SS because of the much thinner walls,i.e. 0.020" is far
more forgiving than a 1/2" to 1" thick injector faceplate.
A footnote about tubular TCA's. On one design, the 20KLbF Corporal engine,
the cooling channels were hydro formed by resistance welding continuous
longitudinal welds
in the double thrust chamber walls then hydraulically expanding the double
walls to form the coolant/fuel channels. I believe they used low carbon
steel.
K
On Wed, Oct 28, 2020 at 11:08 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Tue, 27 Oct 2020, Troy Prideaux wrote:
The only thing I could find is this: http://www.spaceuk.org/htp/htp.htm
which says the gamma 301 chambers were formed and brazed nickel tubes
(whether correct or not… dunno), but as for the gamma 8 and 2… we’ll
have to go with Henry’s references.
"The Gamma rocket engines for Black Knight", Andrews & Sunley, JBIS 43.7
(July 1990), part 2 (Gamma 301, Andrews), p. 307: "Instead of being
constructed from machined components, the combustion shell was now
constructed from 60 stainless steel tubes, each pressed into an
approximately trapezoidal shape, and bound by metal straps [which carried
the hoop loads]... US practice had been to furnace braze the tubes to
form the shell, but braze metal would not have been acceptable in contact
with HTP in the inlet manifold, and it was thought impracticable to mix
welding and furnace brazing on this part of the assembly. So, instead,
the tubes were welded along their lengths."
(The reference to "machined components" is to Gamma 201, the original
Black Knight engine, which used more or less saddle-jacket construction
rather than tube-wall. Its inner wall was nickel-plated low-carbon steel,
its outer wall aluminum alloy.)
The first- and second-stage engines for Black Arrow were as close to the
Black Knight ones as possible, and in particular used Gamma 301 chambers,
the differences coming mainly in the second stage (which needed nozzle
extensions and two-axis gimbaling). ("The genesis of Black Arrow",
Robinson, JBIS 45.4 (April 1992), p. 150.)
Note that Andrews was chief engineer for rocket engines at the engine
contractor (originally Armstrong Siddeley Motors, later under other
corporate names), while Robinson was head of launcher development at RAE
Farnborough. That is, these are "primary sources", people who were there
and in a position to know the details. That doesn't make them infallible,
but they're inherently more reliable sources -- especially on technical
details -- than second- or third-hand accounts from non-participants.
Henry