Liquid-Fuel Engine Design and Implementation

Hello all,

This is kind of heavy for a first post, but Ad astra. I am looking to design a liquid fueled engine, using kerosene and nitrous oxide. I know that there has been general interest in the idea of a liquid fuel engine for a while, and there still seems to be a desire for one to be developed:

https://www.rocketryforum.com/showt...rtifies-new-tribrid-technology-from-RATTworks

System Solaire also designed a system, but seems to not have caught on with many people.

https://pages.total.net/~launch/ss67b2.htm

I plan on using non-explosive ignition systems, such as spark-ignition and open-source hardware (OSHW) in order to control ignition and throttling. The first design is looking at 65 pounds of thrust for 2 seconds, putting it in the mid-I range, depending on how it tests out.

This pic gives the basic layout of the design, minus the plumbing and the electronics.


I am looking at getting a prototype on the test stand by the end of August.

https://www.indiegogo.com/projects/liquid-fuel-high-power-rocket-engine

Thanks for looking. Any feedback is appreciated.

Finally something interesting , but one word of caution about this link ;

https://pages.total.net/~launch/ss67b2.htm

The address is at 30 minute of my house, it's a small basement apartment and I never here about him at a launch here around, where did he test his stuff ? I'm gone write to him and ask to see him in person, to see the validity of the offer.

Please do! I saw that design when I first started looking for info to get this done. Search terms are here:
https://www.google.com/search?q=sys...i65.7824j0j7&sourceid=chrome&es_sm=0&ie=UTF-8

I was not a fan of trying to find 50% peroxide for every launch. I like the idea of using common ingredients to make life easy.

innkeeper said:

I was not a fan of trying to find 50% peroxide for every launch. I like the idea of using common ingredients to make life easy.

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that's the problem, 50% peroxyde is very hard to get, in Canada you need to have a laboratory as it's restricted. But I can get my hand on it legally.

I'm looking for liquid solution, not for actually launch rocket with it , more for ground test, no need for certification and it's more easy when you need to use pressurized oxidizer

Check into the Reaction Research Society, what they do is more up your alley than here.


https://www.rrs.org/

That's pretty neat. I wish I had my own test range. I will have to get in touch with them. Its a bit of a drive from Denver, but it could be better than the blast pit I have convinced my friend to let me dig on his property.

Area66 said:

Finally something interesting , but one word of caution about this link ;

https://pages.total.net/~launch/ss67b2.htm

The address is at 30 minute of my house, it's a small basement apartment and I never here about him at a launch here around, where did he test his stuff ? I'm gone write to him and ask to see him in person, to see the validity of the offer.

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It is a piece of junk. Don't waste your money.

Bob

bobkrech said:

It is a piece of junk. Don't waste your money.

Bob

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I'm pretty sure that Systeme Solaire advertised this very thing in High Power Rocketry Magazine and would have sworn that John Carmack had ordered these plans way, way, back in the day when Armadillo was cutting it's teeth. A quick search of his site didn't reveal anything so I can't be for certain if it was John. However, I do recall that after review of the plans that was pretty much the sentiment as well.

bobkrech said:

It is a piece of junk. Don't waste your money.

Bob

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I have no will to purchase it, I just want to see if the guy is a fraud.

https://www.ukrocketman.com/rocketry/liquids.shtml

A review of the system is here. He doesn't seem to offer an opinion on the system. Its more of a tear-down and inspect. I looked at it and thought about getting one, but it seemed very "magic box". It would be nice to look at it and have an idea of its operation.

At a glance, it looks like there would be more pressurant volume than fuel and oxidizer volume. Irrespective of anything else, Ugh!

Gerald

So far, with the Isp numbers I am getting from ProPEP, I am looking at about 3 fl oz of fuel and about 8 fl oz of oxidizer. Using the ox to pressurize the fuel saves me a lot of mass and volume. The combustion chamber is looking at a ~2" diam and a ~2" height. The nozzle is under-expanded, currently. There is a large difference in mass between the normal 30/15 nozzle and a truncated nozzle.

Noticed that you want to make all the prototypes yourself with your own machinery? Have you had much experience with using the equipment and getting constant accuracy? Which i assume this project needs to have to make sure everything is consistent for the micro-controller to do its job correctly.
Also are you making sure that tanks are DOT approved? There has been Chinese knock-offs floating around with fake dot stamps. Be on the lookout.

I am sure there are other things I can nitpick about this project, but please dont take it as I am trying to put down the project. Just trying to help with outside eyes.

EDIT: Also if you would like some help with tank info.. I am a paintballer and in my sport we kind of have to know tanks and where to get them. Catalina is a USA brand and they are pretty good with prices. Not sure how big of a tank you need but 13cu tanks are ~$30 with out a regulator or valve.

By all means, please nitpick. More eyes on now is fewer problems later.

I have been looking at nitrous tanks from the racing industry. They have dealing with nitrous for years, and have the pedigree. Any help/idea/info is always appreciated.

The precision and accuracy are within my range of experience, or that of the shop I have making it, depending which is a better use of my time.

From what I guess you probably never launch hybrid rockets ? Your system still need equipment to refill the Nitrous Oxide, I will suggest you work with someone with hybrid experience and equipment , you should talk with legranddudu about it. You will need also a legal way to test it. I see you ask for money and promises of a results, I don't think it's a good idea to ask for money if you don't have something more elaborate as project. Micro-mark is hobby level equipment, a good milling cost $ 7000 and more , cheap one have to much slack to make good work. Still your project is interesting, may be you can find partner with the good equipment to develop it.


https://www.rocketryforum.com/member.php?8752-legranddudu

I am trying to get away from hybrid-style fill and ignition systems. They are inelegant.

Fill the nitrous bottle away from the pad, load it up, open the tank and be ready to launch. Using an arduino to control the propellant throttle valves and the ignition keeps everything internal to the engine, other than the firing signal itself.

Half of the battle with getting this made is getting the testing system together so that I can ensure repeatability and reliability. This is paramount in the development.

My indigogo page is a cluster. Everything I have laid out here, plus a good chunk of the data and math I have should be there, in order to actually inspire some confidence. I am thinking of pulling it until I get everything more organized and get a website up where I am not space-limited on my explanations.

You have probably taken it into account, but the tank pressurization will fall faster with the N2O pressurizing both tanks.

There will also be some loss of sync in pressure between the oxidizer and fuel tanks due to pressurant flow differences through the plumbing plus the different back pressure seen at the combustion chamber and at the fuel tank. So the O:F ratio won't be as constant as you might like, and the required quantities of each may differ a little from what the ratio would indicate.

A classic solution is to put the fuel into the oxidizer tank, with a bladder forming the separator. Then both at least have the same pressurization curve vs time. Then the problem reduces to relative flow rates through the plumbing.

Note - I am not an expert on this. I've just been interested in similar projects for a while.

Gerald

I am in the middle of the flow-loss calcs, currently. Most systems I have seen take a "losses are assumed at..." when calculating flow rates into the combustion chamber. The more robust my modeling, the more I have a better look at what is going to happen during an actual firing.

Other systems that I have seen that are oxidizer-pressurized systems have adequate thrust curves for the applications they are designed for.

As I have been working on this, and reading the ideas and concerns voiced here and elsewhere, it has been constantly reinforced that everything comes with a trade-off, as the vast majority of engineering projects do. I am hoping my design will eliminate some of the more creative but less-than-ideal solutions in exchange for a more robust and user-friendly system.

Before you get too enthusiastic, you should be aware that liquid rocket motors are not currently certifiable for hobby rocket use by NAR or TRA so you are designing an amateur rocket for which there is no ready market.

The issues are primarily safety related ignition problems. If a solid or hybrid does not ignite promptly, it simply chuffs. If a conventional liquid fails to ignite, you have a pool or cloud of liquid fuel and oxidizer that when ignition does occur, it will occur explosively and usually results in a fireball and lots of pieces flying. If it fails to ignite, the area around the pad is contaminated with a hydrocarbon fuel.

TRA has certified RATTWorks Tribrids which are a hybrid with a secondary alcohol fuel. The motor first ignites as a hybrid and then a liquid alcohol fuel is injected into the thrust chamber where combustion is already underway, totally bypassing the liquid ignition problem.

Bob

I am aware of the difficulties involved. I knew this would not be an easy project. There are many hurdles, but you have to start somewhere.

The issues that you bring up can be mitigated to some extent through fail-safe systems incorporated into the microcontroller. Feedback systems are required, but this is not beyond the capabilities of the controllers on the market. The good thing about nitrous is that it is a gas at room temp and will evaporate. Contamination might be more of an issue, but we seem to be comfortable with contaminating the launch sites with perchlorate already.

Certification is a chicken and egg issue. Do we not certify the motors because there are none on the market or vice versa? NAR and Tripoli are safety conscious, and rightfully so. I would be very proud of the track record they have with regards to incidents and issues. The question then becomes: How can I do this in such a manner that gives the certification bodies warm fuzzies about the entire system? If there is no market because of a lack of certification, but the system is robust and overall safe to use within the bounds of current protocols, then there is an argument to be made about opening certification to these types of engines.

We were lucky to get out of the BATFE lawsuits with a win. The more options we have, the better. The first post after mine sums it up: "Finally something interesting". I want to make something happen, instead of sitting back and being told I cant. The worst they can tell me is "no". If that's the case, I still have made something interesting.

innkeeper said:

....... The first post after mine sums it up: "Finally something interesting". I want to make something happen, instead of sitting back and being told I cant. The worst they can tell me is "no". If that's the case, I still have made something interesting.

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And I stand on it, when I saw your project page I was not certain, but the way you reply to post, I know now it's something serious.

innkeeper said:

I am trying to get away from hybrid-style fill and ignition systems. They are inelegant.

Fill the nitrous bottle away from the pad, load it up, open the tank and be ready to launch. Using an arduino to control the propellant throttle valves and the ignition keeps everything internal to the engine, other than the firing signal itself.

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Filling the tank away from the launch or test area is certainly possible. Trade offs exist however. Any tank which can be safety filled and touched by human hands is going tool be h.e.a.v.y!!! You give up a lot of performance and freedom on the physical geometry.

If you're determined to prefill, consider taking to Edward from Alpha Hybrids. He has a huge amount of experience with prefilled tanks.


--MCS

.

Thinking on the certification issue more tonight, I realized that this might be an opportunity to come up with a set of regulations that can be brought to NAR/Tripoli in order to facilitate a certification process. As we are a self-regulating hobby, this would be a prime example of working from the bottom up in order to put guidelines and regulations in place before they are further imposed on us. Yay... another section in my binder.

Any tank that is going to be certified DOT is going to be hefty. Contrail Hybrids are DOT certified. "These motors are a case contained grain system but uses DOT certified Nitrous Aluminum Nitrous flight tanks" https://www.contrailrockets.com/

Thank you all for the info and challenges.

innkeeper said:

Any tank that is going to be certified DOT is going to be hefty. Contrail Hybrids are DOT certified. "These motors are a case contained grain system but uses DOT certified Nitrous Aluminum Nitrous flight tanks" https://www.contrailrockets.com/

Thank you all for the info and challenges.

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In a system like Contrail, you never get close to the rocket when it's fill with nitrous, you have to purge if you want to get near the pad. I'm interested in your system as I want to make ground static test, but I don't see why it will be better than an Hybrid System.

How you plan to purge the mixture of Fuel and Nitrous in case it fail to ignite ?

A very interesting thread, best of luck to you in your endeavor

innkeeper said:

Thinking on the certification issue more tonight, I realized that this might be an opportunity to come up with a set of regulations that can be brought to NAR/Tripoli in order to facilitate a certification process.

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I don't think this approach has even the slightest chance of working unless you can demonstrate a working engine. For the NAR or TRA to do this means bringing in front of the NFPA. This is a long and involved process. You'd have to convince the the NAR and/or TRA that enough of their membership want this for them to go through the effort.


I think as a personal project what you want to do is cool. As a commercial venture, I'm really skeptical.

innkeeper said:

Any tank that is going to be certified DOT is going to be hefty. Contrail Hybrids are DOT certified. "These motors are a case contained grain system but uses DOT certified Nitrous Aluminum Nitrous flight tanks" https://www.contrailrockets.com/

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Unless they've changed their design, their motors are monotube hybrids and aren't using DOT flight tanks.

The only motors of theirs I've ever seen which weren't monotube were their "Trojan Hybrids" which, as far as I know, never made it to sale.

-Kevin

Please be careful with pressure systems!


Sent from my iPad using Rocketry Forum

innkeeper said:

https://www.ukrocketman.com/rocketry/liquids.shtml

A review of the system is here. He doesn't seem to offer an opinion on the system. Its more of a tear-down and inspect. I looked at it and thought about getting one, but it seemed very "magic box". It would be nice to look at it and have an idea of its operation.

Click to expand...

A few things to point out in the review. The simple rocket for this motor weighs 7.1 kg. and the motor has an average thrust of 260 N. The initial thrust to weight ratio of the rocket supplied with the motor is 260 N / 7.1 kg *9.81 m/s2 = 3.73 providing an acceleration of only a = T/W - 1 = 3.73 -1 = 2.73 g. This is very marginal and only acceptable with a very long launch ramp in winds less than 3 mph or 5 kmh.

The review also claims the motor is base on the one used in the German Tailfun Missile that used a Nitric Acid / hypergolic hydrocarbon liquid propellant that produced 7.84 kN thrust. https://www.astronautix.com/lvs/taifun.htm It is not even a close comparison as the German motor used a hypergolic bipropellant system that produced 30 times higher thrust. The rocket weighed 20 kg and carried 10 kg of propellant burning at a specific impulse of 200 s for 2.5 seconds. The initial acceleration was a = 7840 / (20 x 9.81) = 39 g and a burnout acceleration of 7840 / 10 x 9.81 = 79 g! The comparison of the Tailfun missile to the System Solaire rocket is like comparing a race car to a rickshaw, or not even close.

Bob

innkeeper said:

By all means, please nitpick. More eyes on now is fewer problems later.

I have been looking at nitrous tanks from the racing industry. They have dealing with nitrous for years, and have the pedigree. Any help/idea/info is always appreciated.

The precision and accuracy are within my range of experience, or that of the shop I have making it, depending which is a better use of my time.

Click to expand...

Carbon dioxide and nitrous oxide both have a molecular weight of 44 g/mole. They have identical vapor curves so any DOT approved tank for CO2 is approved for N2O including paint ball tanks.

Paint ball tanks are DOT 3AL rated at 1800 psi minimum. https://www.law.cornell.edu/cfr/text/49/178.46 Tanks are factory stamped with the maximum pressure rating, the tare weight and the fill weight capacity as the capacity of a liquefied gas tank is a weight not a volume so when as it is filled, the tank is weighed, and the filling stopped when weight equals the sum of the tare weight and the capacity weight. As most tanks have valving on the tank, the tank is emptied and weighed prior to filling to obtain the actual tare weight.

https://www.catalinacylinders.com/paintball.html and https://www.catalinacylinders.com/CO2Spec.pdf are examples of CO2 or N2O DOT approved tanks.

If you were using Catalina tanks, you would use either 7 oz. in a 2" OD tank or 12 oz. of N2O in a 2.5" OD tank. 3.21 " tanks are available in 1, 1.25, 1.5 and 1.75 pound capacity.

Bob