Yes,thanks for the pic, you just made my points, I depicted it in the pic
of the Agena nozzle I attached just can't see thru the walls but you can
see both ends on the drilled passages in the 16KLbF Agena rocket engine.
Wicker chairs also depict this hypoid like pattern. A valid 'amature'
project and out of easy to machine lightweight cheap aluminum. If you use
1000 grade it's got excellent thermal conductivity and being a rigid solid
block the reduced strength of the 1000 series isn't an issue, welds great
too. Machining isn't as good but not as bad as pure OFHC copper.
K
On Thu, Aug 13, 2020 at 11:47 AM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Tue, 11 Aug 2020, ken mason wrote:
Jon, one other fabrication technique that is unique and worthy of
mentioning because it's viable even on a small scale and has flown 100's
of times to orbitthat being the RM-81 Agena rocket engine of 16KLbF,or
71KN. The nozzle shown in the pic is drilled from a solid billet at a
hypoid pattern... the cooling hole density is greatest at the throat
just where the heat flux is greatest. The Agena nozzle is made from
lightweight easy to machine/drill aluminum which conveniently has good
thermal conductivity.
Not a hypoid (that's something else), but a hyperboloid. See attached.
(Credit:
<
https://divisbyzero.com/2010/03/20/making-a-hyperboloid-out-of-skewers-and-rubber-bands/>)
A bunch of long straight drilled holes, at an angle and an offset from the
nozzle axis, outline a fairly nice nozzle shape and can serve as cooling
passages for it. The trick is accurately drilling long holes; "gun
drilling" is the generic term for this.
And of course, if you can do that for the nozzle throat, you could go
whole hog by drilling passages in a cylindrical chamber and a conical
nozzle extension, with the ends matching up to the throat passages.
I'd say aluminum is an under-appreciated material for engines. You really
have to cool it well, because it loses strength so rapidly as it heats up,
but its thermal conductivity is far better than steel's, which helps.
(Not as good as copper's, admittedly, but it's also rather lighter.)
Henry
Attachment:
agena_nozzle.jpg
Description: JPEG image
