[AR] Re: Thrust augmentation?
- From: Norman Yarvin <yarvin@xxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 11 Feb 2021 16:47:40 -0500
On Thu, Feb 11, 2021 at 11:37:21AM -0500, Henry Spencer wrote:
On Thu, 11 Feb 2021, Dr Edward Jones wrote:
https://archivesite.jetex.org/motors/motors-accessories.html
I remain skeptical of this thrust augmentation. What's your opinion?
It's for real. The same amount of energy gives you more thrust if it's
spread over more exhaust mass, energy flow being 0.5*massflow*v^2 while
thrust is massflow*v.
You can't get that, though, by arranging for a fast jet of exhaust to
inelastically collide with surrounding air and accelerate it.
Conservation of momentum says that the thrust remains the same in that
scenario; it's what happens after the exhaust emerges from the engine
anyway, whether one likes it or not. So for this to work there would
have to be something more complicated going on. One possibility would
be Nels's suggestion that
If ambient air is mixed into the exhaust as a working fluid, then it
will expand, conceivably generating additional thrust.
Still, to be realized, that thrust would have to actually exert
pressure somewhere, and the walls of that aluminum tube are parallel
to the flow, so that couldn't be where. (The bell-shaped portion is
the intake, not the exhaust.)
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