Hello all,
Troy, I don't know if this is what you meant, but the pyrovalve used by
Aerotech's hybrid could be launched on the same pad as solids, with an ordinary
motor-starter and launch pad. A scale was needed because the tank was loaded
with N2O by weight. I've never used it or even seen it, so now you all probably
know more than I do.
Best -- Terry
________________________________
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> on behalf of
Stephen Daniel <swd@xxxxxxxxx>
Sent: Saturday, March 13, 2021 10:48 AM
To: arocket@xxxxxxxxxxxxx <arocket@xxxxxxxxxxxxx>
Subject: [AR] Re: Hybrid High Powered Rocket
I think you should break this project down into 3 projects.
1) Build your motor. Don't worry about making it flight weight. Bolt the
components to a large metal frame that bolts to your test stand. This project
will force you to acquire and become familiar with nitrous oxide and your
ground support equipment. You'll ensure you are getting reliable ignition,
that you like the recipe and shape of your fuel grain, etc.
2) Build and fly a rocket. Make it big enough that it is likely the size
you'll want for your nitrous, but plan to fly it with a commercial solid-fuel
motor. This will help you learn the procedures for flying HPR in your
jurisdiction. It will also connect you with local rocket enthusiasts who can
be a good source of design help. This is why you experiment with pyro-free
recovery.
3) Integrate and fly your nitrous rocket. This may well involve building a new
motor and a new airframe, but you'll be able to reuse many pieces, all your
ground support, etc.
On Sat, Mar 13, 2021 at 7:59 AM Troy Prideaux
<troy@xxxxxxxxxxxxxxxxxxxxx<mailto:troy@xxxxxxxxxxxxxxxxxxxxx>> wrote:
It’s unusual – especially with these size rockets – to actually carry a (heavy)
solenoid valve on the rocket/engine. You need heat/energy/reactive radicals to
initiate N2O decomposition and O+F reaction anyway, so typically, the
generation of such is also used to open the flow of N2O into the combustion
chamber.
Examples:
U/C valve: where the filling hose to the tank is fed through the nozzle and CC
into either an olive or press-in connector that also can act as an injector. A
small solid propellant preheater slug is typically placed next to or around the
hose at the injector end that (upon ignition) acts to both open the flow by
burning through the hose, preheats the surrounding fuel grain and heats the
incoming flow of N2O to begin the *exothermic* decomposition. 2 MPa rated
nylon hose is generally employed for this fill hose which will actually hold
the typical 5-7 MPa N2O feed pressured but will reliably burst at a touch under
8 MPa. So the hose (very elegantly) acts as (1) a fill hose (2) an “on” valve
and (3) a pressure reliving device.
Pyrovalve: a slug of solid propellant is used to block the injector flow (ie.
typically directly aft of the injector). Sometimes a thin layer of plastic or
polymerized resin or whatever seals the solid propellant from direct exposure
to the N2O. Similar concept to the above except the tank requires filling from
the top thereby requiring a check valve (typically) and some method of
disconnection (hose cutter/mechanical disconnect) of the fill hose.
To initiate the engine, the solid propellant is ignited from the CC end and
proceeds to regress to the point where it mechanically fails and allows N2O
flow though. Again (as with the UC valve), the solid propellant preheater grain
also needs to preheat/decompose some of the fuel and initiate N2O decomposition
as it flows though.
The advantage with this method over the UC is it allows for a broader range
of injector geometries and there’s less chance of over pressurising on
ignition. The downside (as mentioned) is it require separate valving and
disconnection of the fill hose.
Kline/Pooley? Valve: used for the Hypertek commercial range of hybrids of the
late 90s-2000s era. This system required more ground support equipment but
required no solid propellant it was a totally pyroless ignition system.
Basically, a coaxial stainless steel fill spike is inserted up the nozzle,
through the CC with the inner (longer) spike inserted all the way up into an
o-ring recess just aft of the (interchangeable) screw-in injector. The base of
this spike is also attached to a plate that is used to act as anchor points to
tie the motor down via plastic cable ties which is to stop the rocket from
popping off the fill spike upon filling. N2O is fed up in the centre spike into
the tank and when the rocket is ready to fire, gaseous O2 is fed up the
(shorter) outer jacket tubing into the CC to create a very reactive zone
between the solid (plastic) fuel and GOX within. Some 2 core speaker wire is
generally taped to the outer sleeve/tube and when ready, a high voltage arc is
passed between the ends of the wire thereby igniting the wire’s insulation and
subsequently the exposed fuel in the GOX filled CC. Upon enough thermal
reaction, the cable ties holding the nozzle (retainer) down to the plate will
melt through and let go, thereby allowing the rocket to rise and the N2O to
start flowing into the CC as the spike clears the o-ring sealed recess… and off
we go.
There’s probably a hundred more methods, but these 3 are the most elegant or
practical especially for the size hybrids being discussed here.
As for non pyrotechnic recovery. There are systems – I’ve been doing non pyro
recovery for over 10 years, but it’s a really challenging project to develop
your 1st hybrid engine AND do non pyro recovery.
A local club presentation I did back in 09. It’s a bit dated, but provides more
detail on the methods I just described. I’ve posted this link before here.
www.propulsionlabs.com.au/hybrid/TRAAU Hybrid Propulsion Systems
Presentation.ppt<http://www.propulsionlabs.com.au/hybrid/TRAAU%20Hybrid%20Propulsion%20Systems%20Presentation.ppt>
Cheers,
Troy
From: arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>
[mailto:arocket-bounce@xxxxxxxxxxxxx<mailto:arocket-bounce@xxxxxxxxxxxxx>] On
Behalf Of SAI WAI PHYO
Sent: Friday, 12 March 2021 6:37 PM
To: arocket@xxxxxxxxxxxxx<mailto:arocket@xxxxxxxxxxxxx>
Subject: [AR] Hybrid High Powered Rocket
Hi all!
I am want to design a hybrid high powered rocket which uses nitrous oxide as
the Oxidizer and 3d printed ABS as fuel. I need help on the design process of
the certain aspects of the rocket such as:
1. What should be appropriate amount of total impulse that I should set for
the motor? My target altitude is 1km.
1. What size should the airframe be? I am aware of the different sizes of
airframes but since I am making a hybrid, I need an airframe that can fit a
solenoid valve that has a pressure rating fit for nitrous operation and can
have a large range of fitting choices.
1. Are there any non-pyrotechnic recovery methods that I can look into?
I do not plan to make this yet, I just want to learn the design process of a
high powered rocket .
Regards,
Sai Wai Phyo
Student | Diploma in Aeronautical Engineering
Singapore Polytechnic
500 Dover Road, Singapore, 139651