Can you say conclusively that they would not suffer combustion instability?
I would have thought that there was always the possibility of instability
in any combustion system where the rate of energy release depends on local
pressure or flow conditions and occurs with some time lag, there are bound
to be conditions where energy release couples with fundamental acoustic
modes and given the solid fuel grain of a hybrid there would be the
additional complexity of mixed phase interactions, boundary layers and so
on.
Andrew
On Tue, Mar 21, 2017 at 4:53 AM, Anthony Cesaroni <acesaroni@xxxxxxxxxxx>
wrote:
I suspect that's because SNC/SpaceDev were trying to exploit and upscale
30+ year old classic hybrid technology.
State of the art, staged combustion, gas generator hybrids outperform
solid rocket motors and rival many bipropellant engines in terms of
specific impulse. They also excel in density impulse. They do not suffer
from combustion instability or shifting O/F ratio and realize excellent
combustion efficiency.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
On Behalf Of Ben Brockert
Sent: Sunday, March 19, 2017 7:27 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: List of universities with liquid rocket engine
development programs
Seems accurate to me. Hybrids manage to have most of the downsides of both
solids and liquids, while adding new ones like complexity in mixture ratio
control and propellant depletion, unusual instability modes, unfavorable CG
and/or diameter mismatch, and--while not required to be a hybrid, still
quite common in hybrids--the complexity of two phase flow. It's not a
coincidence that none or near none of the crop of new launch companies are
using hybrids. Sierra Nevada, which owns SpaceDev and a lot of hybrid
building experience, abandoned the idea of using hybrids on DreamChaser in
favor of liquids.
Unrelated to hybrids, but related to you, Troy, I visited TU Wien in
Austria over the summer and they showed me their hardware. They have a lot
of very pretty stuff, like 3d printed metal fin cans for minimum diameter
rockets, but also built one or more of your balanced piston pyroless
deployment devices. It was neat to see the hardware "in the wild" after
seeing you post it here; I mentioned to them that they should send you
pictures if they hadn't.
On Sun, Mar 19, 2017 at 2:15 PM, Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
As a generic blanket statement - that's absolute bullshit.
Troy
Hybrids combine the complication of solids with most of the
complication of
liquids: you have to rebuild the "hot section" of the motor to put in
more fuel for each firing, even though you have a feed system with
tanks and valves to deal with etc.
-dave w
