I should had been more specific. I was refering to classical hybrids in general
which have a propensity for instability.
In staged combustion hybrids, efficient and stable combustion can be attributed
to several factors. For example, fuel is delivered to the through the injectors
as a dense gas at moderately high temperatures where impingement with the
oxidizer occurs and the preferred injector design is a pintle arrangement. The
combustion chamber is otherwise similar to most bi-propellant engines.
Having said that, you’ll be hard pressed to find any rocket example that has
suffered from combustion instability when fluorine is used as an oxidizer.
Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
<http://www.cesaronitech.com/> http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Andrew Burns
Sent: Monday, March 20, 2017 4:29 PM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: List of universities with liquid rocket engine development
programs
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
<mailto: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 <tel:%28941%29%20360-3100%20x101> Sarasota
(905) 887-2370 x222 <tel:%28905%29%20887-2370%20x222> Toronto
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx <mailto:arocket-bounce@xxxxxxxxxxxxx>
[mailto:arocket-bounce@xxxxxxxxxxxxx ;<mailto:arocket-bounce@xxxxxxxxxxxxx> ] On
Behalf Of Ben Brockert
Sent: Sunday, March 19, 2017 7:27 PM
To: arocket@xxxxxxxxxxxxx <mailto: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
<mailto: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
