Liquid Fueled Rocket Engine.

[shade]

Hello all,

My name is Ron, I live about 90 miles south of Chicago (aka Shit-cago).  I have been

reading a bunch here.  This place so far has the best information about liquid fueled

rocket engines so far that I have found (outside of NASA papers, but you cannot have

a conversation with a paper from the sixties or seventies...)

Who am I?  I have a BS in Chemistry and work in the lubricants industry as a chemist. 

My family and I live in the country on a small farm, my wife is an organic farmer, I am

just the mechanic...  I was a welder (think ship fitter) when I was in the Navy back a

few decades ago.  I also had a side business doing welding repairs and fabrication for

about 10 years until it got to be too much.  So I have a fairly well equipped machine

and fab shop, lathe, Bridgeport, shaper, TIG (stick), MIG and Plasma welders and

plasma and oxy fuel cutting.  As well as the associated metal shop equipment, grinders,

drills, brakes, rolls, band saw, etc. So I can torture metal to my will, most of the time...

I also have some experience with GE LM2500 and Allison 501-K17 gas turbines as I was

on a Spruance Class Destroyer back in the day.

On the rocketry forums, when I have tried to engage in the discussion of liquid fueled

engines; I get my threads deleted and told we do not discuss that here and get scolded

like I am some pedophile.  So I like the fact y'all don't do that here.

I am still in the planning phases of my engine.

One question I have that I seem to be having issues getting an answer, is what materials

are you working with on the hot end?  I am thinking that the hot end of a turbine and a

liquid fueled rocket would be made of similar materials.  To the benefit of a liquid fueled

engine, my burn time will likely not exceed 10 seconds.  Also, at least in my first engine,

I do not plan on it being throttleable.  My thoughts so far is to have the engine fabricated

from 316(L) stainless steel, to keep the cost reasonable and use a reasonably accessible

material.

What are your thoughts on this material of choice?

Thanks,

Ron

(PS. Shade is short for "Shade Tree Welder", my biz was Shade Tree Welding Services,

I also run a welding and fabrication forum, do not know if I can post that URL, seems I get

scolded for that too, a lot...  Oh well, I'm used to that, being an old sailor and husband...)

[Richard OConnell]

Hi Ron and welcome aboard! Feel free to post any links here, we love links to places that make us smarter As for nozzle materials, unfortunately I don't have a clue. I would think milled stainless would be fine, but I'll wait for someone who knows rockets a bit better to second that statement.

[racket]

Hi Ron

Welcome :-)

Can I suggest these two excellent books if you don't already have them

www.amazon.com/Aircraft-Missile-Propulsion-Thermodynamics-Application/dp/B000YAM89W/ref=sr_1_6?s=books&ie=UTF8&qid=1408414916&sr=1-6&keywords=zucrow


www.amazon.com/Aircraft-Missile-Propulsion-Turboprop-Turbojet/dp/B000QAA64Y/ref=sr_1_2?s=books&ie=UTF8&qid=1408414916&sr=1-2&keywords=zucrow

Stainless should be OK for a while , our afterburner nozzles are generally only stainless sheet , something a bit thicker should give you enough run time, for more time at a lighter weight you'll need to think of getting some cooling of the nozzle , run some fuel/oxidiser around it .

One of the rocket guys should be able to point you in the right direction, not my field .

Cheers
John

[pitciblackscotland]

Hi Ron,
I have a Hydrogen peroxide rocket engine i got a message from the guy who built the engine and he made it out of 304 stainless. It was built as a test motor for an aerospace company that was going after the x-prize the engine ran for 5 minutes You can tell from the blueing on the stainless how hot it got.
Also here is a link for Hydrogen Peroxide fuel www.peroxidepropulsion.com

Cheers,
Mark..

[shade]

Thanks for all the feedback, I do not have those books... yet...
For my first engine short run times I am not worried about cooling
jackets yet, longer run times will be a consideration. My choice
of 316 is higher nickel content and cost vs. other high nickel
heat resistant super alloys (HRSA's).

If anyone is looking for information on welding, give me a shout
or you can go to my welding and fab forum, www.shopfloortalk.com.
We do not sell or distribute your contact information. I respect
others privacy.

Thanks for the warm welcome!

[britishrocket]

Hello Shade,

Welcome to the all encompassing madness that is Liquid Fuel Rocket building. I fully agree with your ideas to use high nickel content stainless steel (ie 316L) as the primary construction material.

Your background as a Chemist is very interesting and I feel sure it will add a new dimension to the knowledge base here. I'm particularly intrigued by your comments regarding hypergolic fuels. What sort of thing do you have in mind? As you are no doubt aware, most people are using some sort of alcohol as a fuel and either gaseous oxygen or nitrous oxide as the oxidiser. A few are using LOX and kerosine or diesel. I find alcohol attractive as it can be diluted with varying amounts of water, giving a greatly increased cooling capacity for only a very small performance drop. As a British rocketeer hydrogen peroxide should really be flowing in my veins of course. There was a company producing and selling it in Sweden. That was until the elder of the father/son partnership had his hand blown off, and the ensuing fire destroyed their plant...

I've looked at nitromethane as a monopropellant, but I rejected this - it is far too hit and miss I think. It is liable to detonate without warning in the kind of situations it would find itself in within a rocket engine feed system.

Look forward to seeing your progress. Again, a warm welcome to this forum.

Carl.

[shade]

Carl,

Thanks. My thoughts on a Hypergolic fuel was Hydrazine (Fuel) and Red Fuming Nitric Acid (oxidizer), but they have their own safety issues but they are storable. Being a chemist I do have some ability to get things the average Joe cannot. I was going to use either argon or helium as my pressure agents both are inert with respect to both propellants. However, I have been looking into Diesel and Nitrous as of late and since I am still just at the knowledge gather phase I have not committed to a fuel/oxidizer combination yet. None of the monopropellant excite me much either, peroxides are just not fun shit to play with, ask the Swedes. My first pass at a functioning engine will be a full throttle only version, making it throttle-able is another whole set of issues. My initial thoughts are to have the injector plate a bolt on design so I can run some experimentation with different injector nozzle geometries. I was hoping I would get multiple burns per engine before the throat erosion became excessive.

Are you anywhere near Manchester or Sheffield, or for that matter Burton-on-Trent; I am hoping to get over to the UK later this year or early next year. It is mainly for work related stuff but I usually stay for a weekend and be a tourist a bit. I will be making a stop at Bakewell too, there is a little whisky shop there called the "The Wee-Dram"; wonderful place and I am out of Ardbeg.

Thanks again,
Ron

[britishrocket]

Hello Ron,

Sounds interesting. I did briefly look at the feasibility of obtaining RFNA, but I decided it would be just too dangerous to store in my workshop. Likewise the same with Hydrogen Peroxide. Any small amount of contamination into the Peroxide and off it goes, as I'm sure you know. Having a farm with lots of land I would guess you could find somewhere safer to store the RFNA. I'm also using argon as a pressurant because I can easily obtain it for my welding.

Bolt on injector sounds good. Even with stainless steel you will still need some sort of cooling to get multiple runs, in my opinion. To begin with my idea was to use gaseous oxygen as the oxidiser, but I struggled to get decent flow rates. So I decided it might be worthwhile looking at nitromethane, so that a small flow of oxygen could be used to get the nitromethane going, then be shut off. The more I looked into nitromethane though, the scarier it got.

I'm not near Manchester, Sheffield or Burton. I'm way up North in the Highlands. As you are a whisky man you will know of Speyside, which is where I am. Distilleries are as numerous as leaves in Autumn here...Within half a mile of my house are Benromach and Dallas Dhu, and slightly further afield Aberlour, Craigellachie, Glen Elgin, Glenlivet, Glenfiddich...I could go on!

Good luck in your endeavours,

Carl.

[britishrocket]

Hi Ron,

Forgot to mention in my last post:- If you are interested in rocket propellants in any way you would do well to read John D. Clark's book "Ignition!". You can find it online here:- library.sciencemadness.org/library/books/ignition.pdf

Carl.

[shade]

Aug 27, 2014 5:17:38 GMT -5 britishrocket said:

Having a farm with lots of land I would guess you could find somewhere safer to store the RFNA. I'm also using argon as a pressurant because I can easily obtain it for my welding.

I'm way up North in the Highlands. As you are a whisky man you will know of Speyside, which is where I am. Distilleries are as numerous as leaves in Autumn here...Within half a mile of my house are Benromach and Dallas Dhu, and slightly further afield Aberlour, Craigellachie, Glen Elgin, Glenlivet, Glenfiddich...I could go on!

Yup having a bit of land does provide a safe margin, and that is in the plan for propellant storage. RFNA, does not scare me near as much as high purity H₂O₂.  I used a lot of RFNA in college and my career in synthesis and analytical work, outside of good PPE and ventilation it is fairly innocuous.  Hydrazine also is stable, with proper PPE and venting.  PPE out side of the lab hood, is rubber gloves, face shield and an organic vapor respirator.  Rubber apron and boots would be advisable with larger quantities.

Hmmm, maybe a drive north might be a good side trip...  I like a good Speyside!  If I lived by you, I would never get any work done.

Thanks for the link to the book.

[stevep]

Hi Ron,

Well, I guess you can forget the reply I gave you over on my thread--I responded before I read here that you're not planning (any?) cooling for your first motor, so, as you surmise, stainless is about your best bet. Being a welder (which I am not), you have the option of doing what some claim is a much faster test-modify-retest cycle: cut off the offending part, weld on a new one. Much faster than drilling/tapping, etc. Ugly as crap, but as the saying goes here in silicon valley "fail fast".

I'm curious if you have any desires to fly the motor--if so, that may affect some of your decisions re design and especially propellant. If your farm is big enough, it might be suitable for low-level flights. Not sure I'd use RFNA/Hydrazine in that case though.

If you are interested in hypergolics (and even if you're not) there are some good papers from the late 50s-60s from the JPL by Jack Rupe. He was interested in getting liquids to mix efficiently and happened to work on the Corporal rocket, which as you may know used nitric acid/amine (aniline). However, if you go with Nitrous, then you're no longer in the realm of liquid-on-liquid and a lot of his stuff isn't directly applicable. (It is very hard to characterize the flow of nitrous as it leaves the injector since you've got (at best) two-phase flow, so a lot of the injector studies aren't all that helpful. I've found some useful material from the guys who've done nitrous-solid hybrids.)

One of the problems you'll have with highly corrosive propellants is that they are....highly corrosive. That is going to affect your plumbing options (meaning $$$$) and post-test cleanup.

You may also want to spend some time thinking about instrumenting/controlling things, assuming that you want to do more than just shoot flames out of a piece of steel. The instrumentation/control is *not* a trivial exercise.

BTW, the problems you may have run into on other rocket forums likely stemmed from the fact that most of those are aimed at hobby/model rocketry and what we're doing here is known as "amateur" rocketry. Hobby/model rocketry is concerned with manufactured solid motors, although there is a subset of folks in the Tripoli organization that build their own solid motors. When it comes to liquids, it's pretty much an individual effort, although there is some help available over on the aRocket mailing list.

Finally, I assume you've found Nasa SP-125--it's pretty much the "go to" document for most of us, at least at the beginning stages. (I have to look at my notes to see whether I've read the item you referenced over on my thread).

--Steve

[shade]

Steve,

Yes saw your other post too, thanks for all the help and references. One thing I am looking into is spinning the convergent and divergent nozzles from a single piece of stainless or maybe two pieces. Yes having the ability to machine and weld is a great help. Thanks for the link to; watzlavick.com/robert/rocket/index.html, he has an amazing amount of data and very well presented. Yes I have the SP-125 document. I also have the texts, Rocket Propulsion Elements, Sutton; and Liquid Rocket Thrust Chamber, Zarchan; the latter has proven to be a great asset on injector designs.

Yes, I do want to work this up to a flying airframe. The more I am reading on various fuels etc. I am starting to shift away from hypergolics, but the chemist in me is resistant to that... LOL! I can get LOX from my welding supplier the question that remains is can I get it in small enough quantities that they are willing to supply it in. A 4500CF Dewar is likely a little excessive in cost and quantity, but the manager there and I are good friends so we will see what can be worked out. Nitrous is much easier for the logistics. Diesel is easy I have 1200 gallons sitting out back, and K-1 kerosene is easy also, as several gas stations in the area carry it.

My plan is to build a fail safe engine, with minimal electronics and controls. It will be a full throttle only 6-10 second burn. Then work up from there in complexity and size. I have many farmer friends, who have no problem with me using their sizeable fields for flying, as long as the crops are out of the field and before planting.

Right now my goal is to make the controls as simple as possible. Your electronics and control are amazing. But a little beyond me, I have the fab skills the electronic skills are my weak spot, too bad we do not live closer. One idea I have played with is a pintle type injector but where the pintle mechanism is also the valve control for both the fuel and oxidizer, or a internal mixing swirl type injector. Use a servo to actuate the valve to a open and lock position via a electrical ambilical connection that will be tied to the ignitor mechanism.

Recovery will be via independent dual altimeters and ejection charges, the first rocket will be low altitude <= 3000 agl and sub-sonic so likely only a main chute will be needed.

Later larger engines with longer burn times I will plan on regenerative cooling. But for a first engine I will stick with ambient cooling. I was l planning on stainless steel tanks for the propellants and piping and aluminum airframe and for the skin either aluminum or composite, not sure on that, I am not looking for altitude or speed records so weight is not as critical.

Thanks again for the information.

[stevep]

Ron,

I'm pretty envious of your location--I have to drive 3 hours (one way) to get to a semi-usable test site and 7 hours (one way) to fly. That, among other things, has dissuaded me from using LOX.

Given that you have an urge to fly something, then, working backwards and making some assumptions about airframe diameter, a 5-second burn can easily get you to 4-10,000' (or more if you don't mind some high-g forces). Depending on the combustion temperature of the propellant and O/F ratio you choose, I think 5 seconds might be about the longest you'd want to count on for an uncooled motor--throat melt-through will be the real problem; erosion is probably not enough of an issue to worry about. To keep drag forces (and mass) reasonable, I'd try to fit everything in a 4" or smaller air-frame. Valves/actuators are probably going to be the constraint here, although if you go with off-the-shelf tanks of some sort, their size may influence things too. One thing to note is that larger diameter tanks will be much heavier in order to withstand the pressure. Granted, you won't be needing more than 400-800 psi, but still, the walls have to be much thicker in a 6" tank than, say, a 3" tank. Back to valves, I'm doing 2" and it's a very tight squeeze; if I needed to use cryogenic valves, it wouldn't be doable at all. OTOH, 6" is, in my opinion, way too costly in terms of drag and mass (even if altitude records aren't the goal). For a decent launch in very calm weather, you're going to want at least a 5:1 thrust/takeoff weight ratio and preferably something up around 8:1 unless you're going to use a mighty long/sturdy launch rod/tower.

That will help you do a ballpark figure for a thrust goal; once you have that (and you assume a chamber pressure of, say, 250 psi), then you can roughly size the throat which in turn will let you size the chamber (based on L* and contraction ratio constraints).

As for the electronics end of things, with some ingenuity you can get thrust data, at least of the go/no go variety, with nothing fancier than some weights and a simple switch. You can work backwards from that to chamber pressure (while making some assumptions about nozzle efficiency) which will give you a hint as to how the combustion is working. It won't be as good as a real chamber pressure measurement, but people make do with it (for solids) all the time. However, that assumes you get enough--but not too much--thrust (for a long enough duration) to actually measure. With some propellants you want an "oxidizer lead" meaning you want the oxidizer entering the chamber a short time before the fuel to avoid hard starts--"short time" being a few milliseconds to a few hundred milliseconds. This can probably be arranged by varying the fuel line length assuming the valves are opened at the same time. Servos (of the RC variety) require some electronics, but that can all be purchased fairly cheaply (a simple servo tester will probably do and you can get those for $10). Ignition is a little harder (assuming non-hypergolic propellant), but something based on an ignition coil can probably be rigged up without too much electronics knowledge. That would make your test procedure something like: press ignition coil button, twist knob on servo tester, when engine comes to life let off on the ignition coil button, count to 5 and twist servo tester knob back to close the valves. It's doable, but you're going to have some adrenaline to deal with :-)

When it comes time to explore O/F ratios and combustion temperatures in some detail, you probably want to make use of either PROPEP or RPA--these are two programs that do the chemical equilibrium analysis and figure out things like ISP and combustion temperature. I use PROPEP and Carl, I believe, uses RPA. There are various flavors of PROPEP out there all of which are free; I can help you find one that's more or less user-friendly. I can't recall if there's a free version of RPA available.

I checked my notes for the Yang reference--turns out I've seen a book he edited on combustion instability, but my local college library doesn't have the one you mentioned. The Zarchan book isn't available either, though I could probably get it (and the Yang) via interlibrary loans.

I think your 1200 gallons of diesel will be more than adequate :-) Actually, what I found was that the best characterized hydrocarbon was JET-A; kerosine is all over the place, refiners (at least in this country) just tossing in whatever comes off the cracking tower; diesel is pretty closely monitored for pollution purposes but the info on it wasn't as plentiful as that for JET-A. In my case the missing info had to do with cooling rather than combustion. Frankly, for a first effort, I think any of them will do and you probably wouldn't be able to tell one from the other based on combustion (but then I haven't burned anything yet, either). I do sympathize with your itch for hypergolics--seems so simple and "clean", no ignition problem (ha!) to worry about, and, according to Rupe, it simplifies some of the combustion issues as well.


In case you're lacking for reading material, here are a few more links for you:
Unreasonable Rocket The saga of making a Lunar Lander - you may appreciate his thoughts on machining stainless steel. Lots of good "lessons learned".
Rocket Moonlighting RM started out doing a nitrous hybrid, but quickly moved into nitrous-propane; he's done some interesting stuff with valves/servos and also DMLS techniques for making combustion chambers.
Armadillo Aerospace Also started out as Lunar Lander participant--lots of good "lessons learned".
Graham Sortino's wikiHe's just starting out, but there may be some useful info there.

I look forward to watching your progress...shout if you have questions....
--Steve

[shade]

Thanks Steve.

[britishrocket]

Just a quick line to let you know that there is indeed a free version of RPA, here:- www.propulsion-analysis.com/downloads.htm

I'm not the best with computers and I find it has a pretty user friendly, intuitive GUI. I ended up springing for the full version, because you can do thermal analysis and various other interesting things with it. Well, if I ever get any time to spend on it I should be able to...

Carl.