The more I think about it, actually, the more I become convinced that
hanging a medusa-nozzle-shaped slug of propellant out the backend could
make a lot of sense, assuming the propellant is structurally sound enough.
In the first instant of fire, quite a sizeable boost should be produced
across one true and six false throats with a crude and rapidly-eroding plug
cluster aerospike briefly forming.
The outside surface, being under roughly 1atm of pressure, should burn
somewhat slowly relative to that inside the cores. Probably would fling
off some interesting slivers and /or offcenter thrust.
On Thursday, November 2, 2017, Dave Barr <dhbarr@xxxxxxxxx> wrote:
Hence my musing on different propellant shapes with higher surface areathan a vanilla cone where a nozzle would usually be.
wrote:
On Thursday, November 2, 2017, Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
throat.Kn is unitless, simply a ratio of burn surface area to area of nozzle
progressive, but can make regressive if taken to extreme.X, H, *, etc shapes all help increase burn area and make motor less
cylinder.The hard part is making and removing the mandrel, not as easy as a
wrote:Rick
On Thursday, November 2, 2017 9:36 AM, Tr Mu <tl01001101@xxxxxxxxx>
and to even out the Kn over the course of the burn.
For calculating the Kn I assume you are using mm?
Also I've been toying with the idea of a x core to increase burn area
area for a cored nozzleless motor, and it occurred to me that a tetrahedralTrevor Mushung
On Nov 2, 2017 12:29 PM, "Dave Barr" <dhbarr@xxxxxxxxx> wrote:
I've been kicking around ideas for upping the initial burning surface
expansion tetrahedron should increase the initial thrust spike, as well.
Further in that vein, intentionally disinhibiting the exterior of this
outside
Can anyone point to research / reading in this area?
On Thursday, October 19, 2017, <spas@xxxxxxxxx> wrote:
Richard wrote:
Cool. Serge, you 'forced' me to do some quick calcs :-)
With core diameter 1/3 outside diameter and a grain length of 10x
(regardlessdiameter, you have a kn range starting at 121 decreasing to 40
perhapsof OD).
For nozzleless motor Kn can be calculated by simple formula:
Kn = 4 * L / D
where L and D are core dimentions.
Using my KNSB design chart:
http://www.nakka-rocketry.net/ design1.html#Charts
your initial chamber pressure is around 215 psi or 15 atmospheres,
consistent with what you reported. Clearly you have 'choked flow' with
your
core acting as a nozzle with sonic exhaust velocity.
That got me thinking. Perhaps a silly idea but what if you tapered your
core at the exit? To act as a divergent section, that should initially
give
you a boost in exhaust velocity (supersonic) and therefore thrust,
atas much as 30% or so. What do you think? See attached graphic.
Yes, most industrial nozzleless motors have such divergent section. But
core15 atm its effectiveness will be low and as pressure quikly drops,
effectiveness will quikly decrease even more. I plan to test motors with
much longer core and I hope KNSB can withstand much bigger pressure. If
these tests will be sucsessfull, than I will try to make divergent.
Serge Pipko
Kiev, Ukraine
http://serge77-rocketry.net
Richard
On Wed, Oct 18, 2017 at 11:29 AM, <spas@xxxxxxxxx> wrote:
Hi Trevor, the short ansver is - for a given propellant OD you need
informativediameter about 1/3 OD and core length 10 OD. This is for KNSB or other
candy propellant with similar burn rate.
But give me a day or two, I'll collect all my data for more
theyansver.
I'd love to read up about your nozzleless motors. They sound like
propellant.would be very cool. What size/shape core? How long of a casing? I'm
thinking of trying nozzleless in 1.5" pvc pipe with 6" of
Just
have to figure out the core to actually produce thrust.
Trevor Mushung
