Do the math, your going to need a little bit more
than venting a tank unless you going pretty slow.
However, venting to an airbag type of system could work.
Robert
At 10:25 PM 1/10/2016, you wrote:
All of these seem to be a problem. Venting through the tanking system out the main nozzle is likely to have low flow, energy losses through all the valves, and the unfortunate consequence of dumping an enormous amount of fuel and oxidizer into a possibly still warm combustion chamber. In addition, there are stability issues in that all the gas will be coming out the bottom, making any tilt likely worse.
Venting out the top has the advantages that only the inert pressurization gas is vented, it can be vented at quite a high mass flow rate, the force is applied above the CG, and is relatively easy to steer. (Four vent ports around the upper airframe, 90 degrees apart from each other. Two fixed to the expected flow rate, and the other two across from them throttleable).
Further advantages are that no hot or chemically interesting propellants need to be handled.
The final advantage is that it doesnât even require a working liquid biprop for testing. Such a system could be tested by putting an N2 tank as payload on a large high power model rocket. Initial testing could be done simply by throwing it out of a Cessna at an appropriate altitude (requiring no FAA airspace waiver, rocket launches, etc)
On Jan 10, 2016, at 8:44 PM, Troy Prideaux <<mailto:GEORDI@xxxxxxxxxxxxxxxx>GEORDI@xxxxxxxxxxxxxxxx> wrote:
The flow rate is likely to be too low if youâre relying on your propellant feed injectors only for the transfer. Remember the Isp difference between the cold pressurant gas and hot combustion gasses is essentially the coefficient of âincrease in gas volumeâ you get from burning the propellant. Gasses do tend to travel better than liquids through plumbing and orifices, but Iâd be surprised if that differential can be made up.
Troy
From: <mailto:arocket-bounce@xxxxxxxxxxxxx>arocket-bounce@xxxxxxxxxxxxx [<mailto:arocket-bounce@xxxxxxxxxxxxx>mailto:arocket-bounce@xxxxxxxxxxxxx] On Behalf Of Edward Cree
Sent: Monday, 11 January 2016 1:44 PM
To: <mailto:arocket@xxxxxxxxxxxxx>arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Flight Controller Features
Why bother with extra downward-facing ports? Could you not just exhaust your pressurant through the main engine nozzle? Or would the flow rate be insufficient to choke, leading to poor thrust?
Also, could this be tried with self-pressurising propellants, or would the resulting cloud of mixed fuel and oxidiser gas be too likely to deflagrate?
-ed
