Cool new Vehicle....

In the spirit of John Carmack and his recent post about his cool new ride, I thought I'd post a picture of my new vehicle.



I'm looking forward to many hours of fun.... ;-)

Good Results.

Today we tested a new catalyst pack for the blue ball. This is not the motor that we have been machining recently, its a new solid catalyst for the older stainless motor we flew last year. The test was almost perfect. We had no setup issues and everything just worked. The catalyst warmed up on the first burp and ran really well.

I have not yet reduced the data, but visually and audibly it was a better catalyst than anything we have run to date. There is a lot of literature and contradictory information on peroxide catalysts. I’ve personally watched others struggle to get a catalyst to work. A few posts ago I mentioned that I could not really talk about the catalyst design, I still can’t talk about the design, but I can offer some background. I’m always surprised by the number and scope of people that follow along on our journey.  One of the people that stops in from time to time is Anthony Cesaroni of Cesaroni Technologies.  He offered to help me with a known good catalyst recipe. Its a traditional peroxide catalyst, but Anthony provided me with an exact recipe and some tips on subtle mechanical issues I would have never figured out on my own. All I can say is it works exactly as advertised, I followed the recipe and it worked perfectly on the first firing.

I’ve posted two of the most Boeing you tube videos in history. You see absolutely nothing, which is as it should be for a properly working peroxide catalyst.

and

I’ll have some comments on the recorded data in the next few days.I know I got data and I have not had time to look at in in detail.

Motor welded up... Almost...

How it all goes together. The bare chamber

1/2 The split throat outer on the chamber

Both halves of the split throat outer on the chamber.

End of the motor assembled (Rear outer not installed, its really just a sleeve.)

Detail showing the fit between the chamber outer and inner.

Detail of the end where passages end and go into the chamber above the cat pack

All welded up

Lastly doing the water flow showing no leaks on the bottom and all cooling channels are open and free.

I still have to work on the top end closure and top side catalyst retainer, but its really close and I’m happy with the results.

The Action shot...

For weeks the suspense has been building…. I’m making the last cuts on the aluminum chamber.

The Second Passage (Too nervous watching to catch first pass)

A third of the way around….the black line is a Sharpie ink mark not a cut.

It should be done by morning.  I’m going to bed and my Son is Babysitting the mill.

I live about a mile inland from the beach in California, we get a lot of salt air, everything rusts. You can see rust on the mill even though that spray you see going everywhere has soluble oil in it. This setup was about two inches too long to put the normal spray guards on the mill so I’m trying to keep the lubricant in the mill with some Plexiglas pieces. I’m getting coolant on EVERY thing.

 

 

Update...

The Cat screens and Cat assembly is complete. The modified Motor for the Blue ball is 100% ready to test. We hope to test next weekend. Depending on how the 2009 LLC rules turn out we could be doing flight test in as little as two or as many as 10 weeks. If there is some rule advantage to flying the 90 second vehicle soon we are basically ready. If there is no advantage to flying that before the 180 second vehicle we are a 4 weeks away from doing a full up static test of the 180 second vehicle and probably 6 to 10 from flying it. After I finished the motor for the blue ball I spent an hour  aligning the Rotary table and rotary Table Tail stock. This was in preparation for cutting the slots in the aluminum regen motor for the 180 vehicle. After watching armadillos efforts on the 180 second vehicle with the various burn through issues or longevity with insufficient performance issues I’m somewhat convinced that one needs to run a regen motor to get to 180 seconds. John or someone else could easily prove me wrong, but thats my current opinion. Thanks again to armadillo for being so public about their process publishing both good results and bad.

 We have to run some materials out to the test site, so Monday (A holiday for Netburner.) will be lost to the  drive. We will be going out again at the end of the week to test.

  

Simple error hours of work....

I’m building a screen based catalyst for the blue ball. Unfortunately I can’t talk much about the catalyst construction, I have a NDA with a third party that covers parts of the design I have parts that are from public sources and parts are my own creation alas its hard to tell what part  I’m free to discuss here so I won’t really give any details. One of the steps in the process involves cutting about 100 disks from some screen material. I want these to be fairly tight in the bore of the cat holder, so I measured precisely , twice and got the disks all cut at thunderbird  water-jet. After all the subsequent processing the disks were all about 0.05” too big. They bowed big time when forced into the bore.  So I spent my evening building a fixture for the CNC mill that precisely places the slightly too big disk, clamps it around the edges and then mills off 0.05” from the diameter. In the final process I did the disks 6 at a time with a clamp, rotate 90 degrees and re-clamp step in the middle. It took me about 2.5 hours AFTER I built the fixture.  Arghhhhh. In any case I’m going to go to bed before 11:30!!! What a treat. Remember boys and girls sleep is a no credit elective!

Another 32 hr weekend.

I finished the shells for the regen motor. So I have the inner core and the outer shells almost all done. All I have left to do is cut the cooling channels in the inner core. I only made one minor error in the set of pieces and I fixed that with some valve lapping compound and 3 hours of elbow grease. Based on what I can see and measure the worst case gap between the shell and inner is 0.005” Most places its tighter than that.

If all goes well I’ll start cutting the cooling channels Monday night. And I’ll have it ready to test by Friday.

Whine the weekend was spent machining one can never seem to avoid writing software ;-)

I wrote a lot of software this weekend. I have several good programs to convert CAD drawings into instructions for the milling machine, I have not found a good one for the Lathe. I tried a demo of an expensive lathe cam package and it crashed on about 50% of my drawings. So if the demo crashes how good is the production S/W going to be? So I wrote some code that takes the line geometery for the part to be made and makes lathe G code. It works for both inside and outside roughing and finishing. Some day I’ll even put a UI on it so you can change things like tolerances and mode without recompiling. CAM software for the lathe is something I’ve been meaning to do or research and buy for a long time, I just got tired of measuring a bunch of points and shapes on the cad drawing, moving them to excel then doing a bunch of geometry calcs in excel, and finally hand translating them to g code in a text editor. My one macining error looks like it was a transposition of two digits on the coordinate for the center of an arc. I’ll take pictures of the parts and maybe even a short video showing how it all goes together.

Liner Lathe work is done.

One very long day and two evenings and I’ve turned a 65 lb chunk of aluminum into a 4.5 lb chunk of aluminum shaped like a rocket motor. My turnings recycling bin and spare trash can both are full the overflow is on the floor….

The result looks nice….

Now to make the outer shells and cut the cooling channels.

 

Planning the machining...

I spent a good part of the day double checking my motor design before I start machining the outside.I’m glad I did, because without some adjustments It would not have been possible to machine the cooling slots.I ended up making a 3D rendering of the motor, the slitting saw and the bottom eand of the mill spindle. Then I adjusted things until only the cutting surfaces contacted the motor.In the pictures below the tool and mill is represented via the Gold solid as it sweeps along its cutting path.

The last picture shows the general layout.

• Blue is the slitting saw center line path.


• Black is the chamber


• Red is the cooling channel depth.


• Purple is the outer jacket (made in three pieces then welded back together.


• Green is the size of the raw stock that will form the outer jacket

Inside Outside...

I know what the iinside of my chamber looks like, now to figure out the outside. I know what pressure drop I’m planning on at max flow in the jacket. So I need to figure out how many cooling channels and their width and depth. This is a bit of a black art so I drew up one pssible channel configuration and milled it as a slot in some aluminum. I then bolted a face plate against it. I put 18 PSI water pressure in one end and captured 10 seconds of flow that I weighed it was 390 gm. This was about 30 to 50% higher than I wanted. So I need to make them smaller, or reduce their number.  I also sent the cad model of my slot to my friends at flowmetrics and Carl was going to run a CFD check to see if experiment and simulation agree. The one big benifit to doing the simulation over the experiment is that it wont spray water on the front of your pants making the neighbors  think you had an accident. It will also allow one to do some proper heat flow analysis.

The test plate on the garage sink

The Lathe mount I worked on for several days. The boreing bar is 11” long to the face of the holder. This solid peice replaces the rotatable stock secondary slide. (Look up a birmingham or grizzly 13x40 lathe for a picture)

Lastly the motor insides I bored out of solid block of aluminum:

 

 

 

 

 

 

 

 

 

 

All Day...

My new Lathe parts work well, I finished them this morning and then  I spent remainder of the day machining the inside of a motor out of a solid chink of aluminum. I am basically taking a 8” x 16” Solid aluminum round and removing everything that does not look like a rocket motor. I started at 9 am, its 1am a 18 hour day in the shop  on hard concrete. My feet hurt.

Just checking in

Since the ring catalyst failed we are evaluating two other kinds. We are looking at traditional silver plated nickel and some metal monollytic catalysts. We have some samples of the metal monolyths we received from John Carmack and we hope to test them in a regen cooled engine capable of running in Monoprop or Biprop mode in a week or two.  I ordered the nickel screens and hope to fabricate a motor for that configuration in the next two weeks.

I’ve been working on machining the regen engine out of a large chuck of aluminum and the size is stressing the capabilities of my lathe. The Lathe is a manual lathe converted to CNC and the cross slide tool mount was not very rigid. I started more than a week ago to machine some new mounts and the speed control on the Mill motor started acting up. So I bought the Tormach speed control upgrade (stock on the new Tormachs) and Its a great upgrade. Now that is fixed, I’ve spend the last week machining new tool mounts out of large chunks of steel. they should be more rigid.  The mill is machining the last piece as I write this so I hope to get back to machining the actual motor on Saturday.  Machining Aluminum and the C145 copper is fun, Machining stainless is miserable, machining medium steel is some where in the middle, not as picky about feed rate as stainless, but still wears the tooling a lot faster than aluminum. 

On a side note I stick all the tools I use at the mill, draw bar wrench, vice wrench, chuck keys etc… to the back of the mill with some strong magnets.  With aluminum or Stainless this is not an issue, when machining  steel all the sharp chips stick to the tools making it a hazard to use them. No fun at all.

 

Test Results: Ring Catalyst Fails.

The Ring catalyst failed to get good decomposition. I have video of lots of billowing steam as the partially decomposed peroxide falls on the concrete in the flame trench. I probably won;t post these as they aren’t very interesting.

We were out at FAR at the same time as the FloMetrics guys and their LR-101 rocket static test went well. 10 Second burns on both RP-1 and Biodiesel. These videos I will probably post when I get time to do so. The sound of a kerosene rocket is just different that than lox-alcohol, hybrids, solids, sugars, and mono props. They all have a different sound and the kerosene sound is very cool.

Static Test

Our stuff is packed we hope to do a static test of the new solid cataylist on Saturday.

 

Designing a chamber....

So you want to design a chamber, there are many ways to do this. My method is not real rigorous, but here it is.

First know what you want. For this example:

• 90% peroxide /kerosene with a solid catalyst.


• 915 lbs max thrust. (This is 125% of max weight for my notional 180 sec vehicle.)


• 320 psi feed pressure (This is our hydro pressure /1.25)


• Optimize for best eff at 475lbs thrust. (This is the mid point on a 180 second burn this number probably needs adjusting upward as more fuel is burned at the beginning of the flight)


• Operate at FAR or Las Cruces, or the new Mexico space port about 4000 ft altitude. (12.4 psi)

Given a 320 PSI feed pressure we need to allocate some pressure drops, I’ll use 75 lbs in the cat pack and 20 percent in the injector /diffuser.  I got the 75 PSI from a  FMC peroxide catalyst pack design document.  I got the 20% from word of mouth and vague references in Sutton.

So the resultant max chamber pressure is (320–75)*0.8 = 260 PSI.

So at our desired optimum 475 lbs we have a chamber pressure of

Cpopt=(475*260)/915 = 134 PSI.

Next Ill run this through cpropep. I ran lots of cpropep runs to arrive at the 0.17g of fuel for 100gm of 90% peroxide. This is the final input file run:

Propellant X/Y
+466     0.90 g
+976     0.10 g
+797     0.17 g

FR
+chamber_pressure     134 psi
+exit_pressure         12.46 psi

The output is:

Thermo data file: thermo.dat
Propellant data file: propellant.dat
Computing case 1
Frozen equilibrium performance evaluation

Propellant composition
Code  Name                                mol    Mass (g)  Composition
466   HYDROGEN PEROXIDE (100 PC)          0.0265 0.9000   2H  2O
976   WATER                               0.0056 0.1000   2H  1O
797   RP-1                                0.0121 0.1700   2H  1C
Density :  1.228 g/cm^3
3 different elements
H  O  C
Total mass:  1.170000 g
Enthalpy  : -6420.12 kJ/kg

114 possible gazeous species
3 possible condensed species

                       CHAMBER      THROAT        EXIT
Pressure (atm)   :       9.663       5.463       0.848
Temperature (K)  :    2418.562    2205.550    1608.636
H (kJ/kg)        :   -6420.118   -6948.077   -8362.579
U (kJ/kg)        :   -7389.021   -7831.644   -9007.016
G (kJ/kg)        :  -36931.242  -34771.963  -28656.161
S (kJ/(kg)(K)    :      12.615      12.615      12.615
M (g/mol)        :      20.755      20.755      20.755
(dLnV/dLnP)t     :    -1.00000    -1.00000    -1.00000
(dLnV/dLnT)p     :     1.00000     1.00000     1.00000
Cp (kJ/(kg)(K))  :     2.50147     2.45427     2.27083
Cv (kJ/(kg)(K))  :     2.10086     2.05366     1.87022
Cp/Cv            :     1.19069     1.19507     1.21421
Gamma            :     1.19069     1.19507     1.21421
Vson (m/s)       :  1066.56503  1027.58281   875.97064

Ae/At            :                 1.00000     2.44989
A/dotm (m/s/atm) :               157.40662   385.62851
C* (m/s)         :              1520.94574  1520.94574
Cf               :                 0.67562     1.29592
Ivac (m/s)       :              1887.43319  2297.97666
Isp (m/s)        :              1027.58281  1971.02048
Isp/g (s)        :               104.78429   200.98815

Molar fractions

CO                   9.0878e-002 9.0878e-002 9.0878e-002
CO2                  1.2411e-001 1.2411e-001 1.2411e-001
COOH                 3.2035e-007 3.2035e-007 3.2035e-007
H                    1.6249e-003 1.6249e-003 1.6249e-003
HCO                  2.3091e-007 2.3091e-007 2.3091e-007
HO2                  1.8081e-007 1.8081e-007 1.8081e-007
H2                   8.5414e-002 8.5414e-002 8.5414e-002
HCHO,formaldehy      3.0941e-008 3.0941e-008 3.0941e-008
HCOOH                2.3185e-007 2.3185e-007 2.3185e-007
H2O                  6.9535e-001 6.9535e-001 6.9535e-001
H2O2                 1.3262e-007 1.3262e-007 1.3262e-007
O                    3.1412e-005 3.1412e-005 3.1412e-005
OH                   2.4808e-003 2.4808e-003 2.4808e-003
O2                   1.0559e-004 1.0559e-004 1.0559e-004

Lots of data here but I really only want the four items I set in bold.

First dimension question how big is the throat?

For 915 lbs thrust at 260 PSI we need the Cf number.

So Throat Area = 915/(260*cf) =2.71 sq inches in area.

The Throat diameter is thus 1.859473 inches.

For thoose who want consistent SI units:

915 lbs is 4080 N  260psi is 179 N per cm^2

So At = 4080/(179*cf) = 17.58 cm^2

converting back to inches for a consistantcy check we have 2.72 sq in.

Now that we have the Area Throat we need Area Exit

Ae=(At*Ae/At) =2.71*2.44989 =6.65 sq in and a diameter of 2.9147 inches.

So now we have the Throat diameter and Exit diameter.

We need the chamber length. This chamber will have Gas/Liquid mixing so we can probably use a shorter chamber than usually, but I’m going to be somewhat pessimistic and use a L* of 50in. I’m also using some fixed catalysts at 7” so my chamber inner diameter is going to be 6.5”.

6.5” diameter is 33 sq in. The At =2.71 so 2.71*50/33 = 4.1 inches.

We now have the major dimensions of the chamber done.

• Throat 1.859 in diameter


• Exit 2.915 in diameter


• Chamber 6.5 in diameter


• Area before the throat 4.1 in long.

The Now to draw some shapes. One could use the classic 15 degree exit cone that would be easy to machine, but gives up a few percent performance. Or one could try and do a parabolic expansion cone. I used the RAO optimum nozzle approximation. This is covered in Rao’s classic paper or texts like Modern Engineering for design of Liquid propellant Rocket Engines (Huzel/Hwang) . This requires that you pick a couple angles off a graph and fit a parabola to the resultant points. The problem is actually over specified so you have to decide which end of the parabola you want to be exact. The cook book formula gives you 4 equations and 3 unknowns. For the more math inclined you have two specified points and the slope at both points and you want to fit a 2^nd order parabola through these. Like I said over specified. (You can see the document in question by doing a google book search look at page 76. Search for Huzel Hwang) So after getting some advice and a code snip-it from arocket I wrote a short program that fits a parabola to the defined points . I assumed a 100% of conical length.

So I drew the chamber in the following steps….

• Placed a reference  point at 0,0 and one at 0,(1.859/2) (black)


• Drew an Arc of 1.5 rT to 60 degrees (red)


• From the chart Fig 4–16 initial angle is ~20 degrees. So I drew an arc blue of 0.382 Rt to 20 degrees.


• Then I placed a point at the exit position. A 15 degree half angle cone would be 1.97 inches long going from 1.859 to 2.915 inches. So I plot this point referenced from the throat. (Green line)

The result at this point:

Now using my CAD program I read the x,y locations for the end of the blue arc:

Point at (0.239756,0.971775,0). And the end of the green line. Point at (1.97,1.4575,0).

I plug all this into my little program and calculate a script to draw the nozzle. The Program :File Attachment: calcv2.cpp (1 KB). Now I have the basic chamber contour. All I need to do is Add the upper chamber and mirror

Next steps involve giving the chamber some thickness and the design of the catalyst holders and injector/diffuser seals connections etc…. to be continued….

 

 

 

 

 

 

 

 

 

 

Merry Christmas

I won’t be blogging much until early next year. There is a possibility we may static test our new motor sometime between 31^st and 4^th. I’m looking forward to more progress in 2009.  The gear box is 90% done I need to make one more bearing plate, but all the major structure is done. All the rotating parts are done. It’s heavier that I would have liked. When I’m done I will fully disassemble and weigh the individual parts.

 

 

Why I like this project....

There is very little I enjoy more than learning something new. A traditional aerospace project is an effort involving thousands of specialties. This offers the opportunity to learn thousands of specialties. I have received my Peroxide compatible pump, fuel pump, and motor. I’m in the process of assembling a gear box. I’ve never built a gear box before so one gets to learn new terms like pressure angle and involute. As well as use new tools.. I’m continuously impressed with the variety of free tools available on the web. I’d gathered all the shafts, bearings, gears, parts and etc in to a big pile on my desk. I spent the better part of yesterday laying out the gear box.

I have a fully 3d capable cad system, but I usually do my layouts as 2D line drawings. I find this easier than making a 3D model. My gear box sketch is below as I have been using it (Labels added for your viewing pleasure)

File Attachment: GearsV2.pdf (24 KB)

I’ve machined the top base plate, the adaptor that joins the peroxide pump to the base plate and the curved offset spacers. (Only shown in top view the semi circular arcs with screw holes ).  Today I’m going to try and build the complicated shaft that connects the two pumps to each other and to the gear drive. I’m also going to finish bore the gears and lighten them. If all goes really well I may even get to a full trial assembly.

This shows the peroxide pump and the aluminum adaptor connecting it to the main plate. It also shows the curved spacers.

Monday Morning update. I machined the shaft and couplers for the pump side , I also lightened he commercial gears and bored the one that needed bored.

 

 

Back to Hardware....

We are   were going to go out to the test site and static test the blue ball with a “solid” catalyst. (The FAR event was canceled due to 75mph winds forecast on Saturday as I was typing this.)

John Carmack sent me several catalyst styles, one kind was a pourable ring catalyst from cpilink.com It looks like the picture on the right here. So we had some stainless plates  water jet cut by Thunderbird Water Jet to hold the catalyst rings, and we added a sintered stainless diffuser plate. and reassembled the motor.

When we first cut the motor apart the inside was kind of nasty with permangenate residue.

 

 

A picture of the sintered diffuser plate welded to the support ring.

A view from the other side as it is welded into the top of the motor.

 

A view of the waterjet cut bottom support plate. The area between the two plates is filled with the ring catalyst. The fittings on the side as shown on the view of the motor top allow us to shake the catalyst out and replace it.

The reassembled motor ready for testing…. soon.

New FAA rules.

The new FAA amateur rules were released today. It looks like they will be officially published on the 4^th and become effective on Feb 2^nd.  Since this removes the burn time limit and requires nothing more than ATC notification for flights in  uncontrolled airspace more than 5 miles from an airport, it basically means ZERO paperwork for the testing and development of a hovering LLC class vehicle that stays under 200K lb/secs of total impulse.  I’m practically giddy!

Thanksgiving week...

While we all enjoy the company of friends and family during this thanksgiving holiday, don’t forget the men and women of our armed forces that may not get the chance to be home this holiday season. I’ve given something to LBEH for the last 7 years to try and help. Some bloggers have a tip jar, I ask that you send any tips there instead.