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Greetings Thread
- azhilyakov
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11 years 4 months ago #6372
by azhilyakov
Won't "flap guidance" system correct it?..
-Alex
Replied by azhilyakov on topic Re: Greetings Thread
... because if hot gas and/or propane finds its way into the N2O tank or the other way around, ...
Won't "flap guidance" system correct it?..
-Alex
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- bobkrech
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11 years 4 months ago - 11 years 4 months ago #6374
by bobkrech
Using propane requires a separate pressurization tank of nitrogen or inert gas. It is possible to utilize a floating bulkhead design where N2O provides the pressurization however piston sealing could be problematic because if a leak occurs, and explosion is likely to follow.
Of course this an amateur rocket project and liquid rocket motor flights are not allow at either NAR or TRA launches. Just about the only sites I am aware of is FAR or RRS in CA. A good topic of discussion at one of our monthly meetings.
Bob
Replied by bobkrech on topic Re: Greetings Thread
The correct hydrocarbon for a self-pressurized liquid fueled rocket using N2O as an oxidizer is ethane, C2H6, not propane. Ethane/nitrous oxide is a developed storable noncryogenic propellant system. The vapor pressure curves of ethane and nitrous oxide are well matched and both have nearly identical critical points.Hello,
I was going to pressurize the propane tank with N2. Now the decision I've been wrestling with is whether to complicate a system (that I really don't want to complicate any more than absolutely necessary) by adding a third tank designated for N2 that feeds into the fuel tank or pressurize the tank directly with N2, which has its own set of problems. Careful jet selection should be able to get the stoichiometric fuel/oxidizer ratio right.
This is an extreme longterm project that probably won't see a wet run let alone a working rocket for year(s).
Using propane requires a separate pressurization tank of nitrogen or inert gas. It is possible to utilize a floating bulkhead design where N2O provides the pressurization however piston sealing could be problematic because if a leak occurs, and explosion is likely to follow.
Of course this an amateur rocket project and liquid rocket motor flights are not allow at either NAR or TRA launches. Just about the only sites I am aware of is FAR or RRS in CA. A good topic of discussion at one of our monthly meetings.
Bob
Last edit: 11 years 4 months ago by bobkrech.
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- Thraxz
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11 years 4 months ago #6385
by Thraxz
It wouldn't effect it at all. I was referring to the rocket itself having flaps to keep it flying straight (extremely primitive avionics). They are exterior and unrelated to the motor.
@Bob: It is indeed a better match based on only that parameter (there is no 'correct' fuel perse). Although it is better established in use with ethane. Prop/N2O has also been researched as a pressure-fed system by DARPA, whose paper I've read.
So far every question asked has been striking to the heart of the preliminary decisions I was making in order to plan the motor. (Which is good, these are the most basic important ones). My 'trade off triangle' here is between complexity, accessibility of components and suitability/results. I went with propane for the easy of obtaining propane over ethane at the cost of complexity with the vapor pressure differences of the fuel/oxidizer. All that being said, I'm not above changing my mind for the sake of simplicity. Reducing my rocket's dry weight by an additional tank is still a pretty compelling argument but obtaining it in quantities I'll be using will be far more difficult.
A piston system will not be possible, although it would be an elegant solution; too hard to access.
I've also considered pressurizing the propane with CO2, but it's 'less inert' than N2 despite being a better pressure match with N2O.
Replied by Thraxz on topic Re: Greetings Thread
... because if hot gas and/or propane finds its way into the N2O tank or the other way around, ...
Won't "flap guidance" system correct it?..
-Alex
It wouldn't effect it at all. I was referring to the rocket itself having flaps to keep it flying straight (extremely primitive avionics). They are exterior and unrelated to the motor.
@Bob: It is indeed a better match based on only that parameter (there is no 'correct' fuel perse). Although it is better established in use with ethane. Prop/N2O has also been researched as a pressure-fed system by DARPA, whose paper I've read.
So far every question asked has been striking to the heart of the preliminary decisions I was making in order to plan the motor. (Which is good, these are the most basic important ones). My 'trade off triangle' here is between complexity, accessibility of components and suitability/results. I went with propane for the easy of obtaining propane over ethane at the cost of complexity with the vapor pressure differences of the fuel/oxidizer. All that being said, I'm not above changing my mind for the sake of simplicity. Reducing my rocket's dry weight by an additional tank is still a pretty compelling argument but obtaining it in quantities I'll be using will be far more difficult.
A piston system will not be possible, although it would be an elegant solution; too hard to access.
I've also considered pressurizing the propane with CO2, but it's 'less inert' than N2 despite being a better pressure match with N2O.
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- bobkrech
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11 years 4 months ago #6390
by bobkrech
Most rocket systems use helum to pressurize propellant tanks as helium is not very soluble in most propellants. Pressurizing propane with CO2 and even N2 will reduce performance somewhat as both are soluble in propane.
Here's a few references.
www.smdc.army.mil/FactSheets/MNMS.pdf
www.spacewar.com/reports/Dynetics_Comple...cket_Engine_999.html
hobbyspace.com/nucleus/index.php?itemid=22608
Bob
Replied by bobkrech on topic Re: Greetings Thread
Matchng self-pressurizing tank pressures by using enthane or ethylene reduces system complexity and increases system reliability since you don't need a third high pressure gas tank and pressure regulator.
... because if hot gas and/or propane finds its way into the N2O tank or the other way around, ...
Won't "flap guidance" system correct it?..
-Alex
It wouldn't effect it at all. I was referring to the rocket itself having flaps to keep it flying straight (extremely primitive avionics). They are exterior and unrelated to the motor.
@Bob: It is indeed a better match based on only that parameter (there is no 'correct' fuel perse). Although it is better established in use with ethane. Prop/N2O has also been researched as a pressure-fed system by DARPA, whose paper I've read.
So far every question asked has been striking to the heart of the preliminary decisions I was making in order to plan the motor. (Which is good, these are the most basic important ones). My 'trade off triangle' here is between complexity, accessibility of components and suitability/results. I went with propane for the easy of obtaining propane over ethane at the cost of complexity with the vapor pressure differences of the fuel/oxidizer. All that being said, I'm not above changing my mind for the sake of simplicity. Reducing my rocket's dry weight by an additional tank is still a pretty compelling argument but obtaining it in quantities I'll be using will be far more difficult.
A piston system will not be possible, although it would be an elegant solution; too hard to access.
I've also considered pressurizing the propane with CO2, but it's 'less inert' than N2 despite being a better pressure match with N2O.
Most rocket systems use helum to pressurize propellant tanks as helium is not very soluble in most propellants. Pressurizing propane with CO2 and even N2 will reduce performance somewhat as both are soluble in propane.
Here's a few references.
www.smdc.army.mil/FactSheets/MNMS.pdf
www.spacewar.com/reports/Dynetics_Comple...cket_Engine_999.html
hobbyspace.com/nucleus/index.php?itemid=22608
Bob
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11 years 4 months ago - 11 years 4 months ago #6391
by bobkrech
Replied by bobkrech on topic Re: Greetings Thread
To add to my previous posts checkout www.firestar-engineering.com/NOFBX-MP.html
The scientists and engineers at Firestar Engineering LCC have developed a monopropellant composed of nitrous oxide and ethane (and/or ethylene and/or acetylene and the rocket motor propulsion system for it under multiple NASA SBIR awards. It will be tested in space on ISS in 2013.
This propellant system solves a NASA/DoD need to develop a GREEN substitute for hydrazine/nitrogen tetroxide bipropellant propulsion systems which are toxic carcinogenic and explosive.
en.wikipedia.org/wiki/Nitrous_oxide_fuel_blend
Bob
The scientists and engineers at Firestar Engineering LCC have developed a monopropellant composed of nitrous oxide and ethane (and/or ethylene and/or acetylene and the rocket motor propulsion system for it under multiple NASA SBIR awards. It will be tested in space on ISS in 2013.
This propellant system solves a NASA/DoD need to develop a GREEN substitute for hydrazine/nitrogen tetroxide bipropellant propulsion systems which are toxic carcinogenic and explosive.
en.wikipedia.org/wiki/Nitrous_oxide_fuel_blend
Bob
Last edit: 11 years 4 months ago by bobkrech.
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- Thraxz
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11 years 3 months ago #6408
by Thraxz
Replied by Thraxz on topic Re: Greetings Thread
These are all interesting tidbits. Unfortunately, it's clearly proprietary and of not much detail on how to accomplish it. Though it would seem that you'd just add the two propellants to the same tank in proper proportions while they did the legwork of showing its stability. It all comes down to the fact that I still don't have access to ethane.
I've been working off of this paper:
tfaws.nasa.gov/TFAWS06/Proceedings/Aerot...1026_Paper_Herdy.pdf
Though, it seems that unless I do get access to ethane I'm stuck pressurizing something else because cryogenics is not an option and I'm not particularly fond of HPG solutions because density is extremely low.
Though, I'm still at a stage that I can easily switch from one fuel to another. Given this, I still actually have my choice of fuels. I've been considering switching to kerosene (not rp-1 kerosene) or something as mundane as ethanol or methanol. It would just require an adjustment of the fuel/nox ratios and making sure the chamber pressure and geometry remain in line with the new gamma.
Another issue I'm dealing with is cooling it. Regenerative probably won't be doable, at least at first. Since I'm using 347 steel it's good with heat, so I can keep firing times short and I'm considering designing a water based pressureless system that vents steam out the nozzle. Neither bode well for longevity. Test firing of the engine once built will tell the tale.
The second engine iteration that will likely be an order of magnitude more complex and not deal with such basic issues of cost cutting.
I've been working off of this paper:
tfaws.nasa.gov/TFAWS06/Proceedings/Aerot...1026_Paper_Herdy.pdf
Though, it seems that unless I do get access to ethane I'm stuck pressurizing something else because cryogenics is not an option and I'm not particularly fond of HPG solutions because density is extremely low.
Though, I'm still at a stage that I can easily switch from one fuel to another. Given this, I still actually have my choice of fuels. I've been considering switching to kerosene (not rp-1 kerosene) or something as mundane as ethanol or methanol. It would just require an adjustment of the fuel/nox ratios and making sure the chamber pressure and geometry remain in line with the new gamma.
Another issue I'm dealing with is cooling it. Regenerative probably won't be doable, at least at first. Since I'm using 347 steel it's good with heat, so I can keep firing times short and I'm considering designing a water based pressureless system that vents steam out the nozzle. Neither bode well for longevity. Test firing of the engine once built will tell the tale.
The second engine iteration that will likely be an order of magnitude more complex and not deal with such basic issues of cost cutting.
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