Randy's Rocketry

Goddard Prototype?

2011-11-15T11:45:00.001-08:00

I saw this on ebay this morning. The seller suggests that this is an early regen engine prototype that came out of Robert Goddard's workshop. That would be cool! The seller makes no claims of having any proof to go with it and with a price tag of $325,000 and a short 3 day inspection period before considering the sale final, it seems unlikely that a buyer will come forward. It does seem that with enough time, that some research and material testing it would be possible to determine if it were at least plausable...

SStS motor casing

2011-10-20T15:04:00.000-07:00

This new casing is a bit longer than the previous casing that I made and it really dwarfs my lathe. It's coming along nicely though. In the top photo you can just make out the Dremel attached to the tool post, it holds a #1 center drill that I use to mark the hole locations in the casing. The Dremel isn't the ideal tool for this; not enough power and the #1 bit is so small I'm always concerned that it'll break. It is enough to mark the locations though. The next step, seen in the 2nd photo, it to use my little drill press and a larger #3 center bit to drill through the casing. Then it's just a matter of enlarging the holes to the final diameter. I like to do this in two steps, drilling to nearly the final diameter, then finishing off to the required diameter as the final step. This results in clean, accurate holes.

SStS Motor Casing

2011-10-13T10:45:00.000-07:00

I have purchased a piece of tube to fabricate a new motor casing for the Sugar Shot to Space DSS effort. The DSS motor and test setup were among the finest I've ever seen, it's a shame that the motor failed but the team has a good idea of the failure mode and how to avoid it. Here is the tube before being cut to length and drilled for the nozzle and bulkhead.

Just when I thought I was working on a large motor, I saw this truck on the freeway hauling a large number of Titan strap-on booster motors. OK, fine! Maybe this is just a sprinkler system for a new industrial building. It's all in how you use them...

JATO

2011-04-06T12:19:00.000-07:00

I just recieved an old rocket motor off of eBay. Sometimes refered to as JATO motors (jet assisted takeoff motor) or by the more accuarate acronym RATO (rocket assisted takeoff motors) these small motors have always caught my interest. Mostly because they were among the first, if not the first, rocket motors that were mass produced. The urban ledgend about the guy that attached several of these to his car doesn't hurt the appeal either. I can't find much information about this particular motor, so if anyone knows anything about them I'd love to hear from you. The markings on the case read Rocket Motor M3, Lot PA-79-9.

eBay

2011-03-23T16:48:00.000-07:00

I saw this Estes Vashon V-1 cold power rocket engine for sale on eBay recently. I don't ever remember seeing these as a kid but I think I would have been drawn to it. A blackpowder motor is cool but this stuff looks like "real" rocket hardware. I found this 1969 Popular Mechanics article describing the system.

It's very similar to the Cricket sounding rocket that I found on eBay a while back.

Update (Sidewinder Nozzle Comparison)

2011-03-22T12:40:00.000-07:00

This past weekend was busy and didn't leave a lot of time for rocketry. I did manage to get the first half of the new nozzle off the lathe and start on the second half. The first half of the nozzle is pretty hefty; I have to remind myself that this motor will produce over 1,600 lbs of thrust with a total impulse of around 8,000 lbs, so a nozzle that weighs in at 4-5 pounds isn't really an issue. In the photo it's next to an early Sidewinder missile nozzle (on the left). Compared to that nozzle it doesn't seem too hefty at all...

Motor Update

2011-03-14T13:16:00.000-07:00

Not much progress this weekend. I've finalized the nozzle design and finished machining the first half of the nozzle. I orderd some stuff from McMaster-Carr including the screws that I'll need to retain the nozzle and bulkhead in the casing, those that will attatch the two nozzle pieces, and the O-rings. I still need to pick up some steel bar stock for the ring/shoulder half of the nozzle.
Here is a render of what the finsihed nozzle will look like:

More Nozzle Machining...

2011-03-09T13:03:00.000-08:00

I'm working on the convergent side of the nozzle now and I've updated the design a bit. Not much of a change; just using a couple of angles leading into the throat region vs one and thinning out the excess material while still leaving enough where the nozzle will take the most abuse.

More Nozzle Machining

2011-03-07T13:07:00.000-08:00

The nozzle is progressing well; I finished the divergent section and should be ready to finish off the other side in the next few days. I was only able to bore it out to a depth of about 5 inches, so I left the throat diameter rough. I'll take it to the final dimension once I'm working from the other side and don't have to have the boring bar extended nearly so far from the tool holder; I should be able to get a cleaner finish that way.

New Motor Nozzle

2011-03-02T18:39:00.000-08:00

I started on the nozzle last night and realized that this really is going to be a big motor. The piece of metal that I started with for this one piece of the nozzle started out at 16 lbs. the other piece starts out at around 4 lbs which means that I'll need to machine away some 17 lbs of metal to end up with a nozzle that comes in at around 3lbs. Lots of metal shavings...

New Rocket Motor

2011-03-01T14:29:00.000-08:00

I recently fabricated the motor casing for a boilerplate version of the next motor in the series for the SStS project. This next phase of the SStS project represents a significant step up in scale; here is the material needed for the casing of this new test motor:

The casing material is steel and pretty hefty, but should work well for this particular motor. I had to get a bit creative as each of the two sections was far longer than the bed of my lathe. It was fun and I ended up being pleased with the results. Here is a section of tube on the lathe and a nearly completed casing section for the SStS motor on my workbench:

I ended up with about four feet of tubing left over and figured that it should become a rocket motor :)My overall design was driven by the length of tubing that I had remaining. Here is the SRM output:

The casing has been completed and I've started cutting metal for the nozzle. I'm making the nozzle in two pieces, to ease the fabrication and to use metal stock that I had on hand. It's a pretty straight forward all steel design. The Divergent section is a little short with an expansion ratio of around 5.5:1, but again this was dictated by the metal stock that I had on hand. The downside is about a 02% reduction in the total impulse, but the upside is probably a six or seven hour reduction in fabrication time. I'll take it!

Everything else is being made with ease of fabrication in mind and I'm hoping to fly it this fall.

More to come...

JPL

2011-02-10T16:34:00.000-08:00

I ran a half marathon this past weekend which wouldn't normally have anything to do with rocketry. This race however was in Pasadena, CA and about halfway through the race I realized that I was running through the Arroy Seco wash right behind the Jet Propulsion Laboratory . Ok, maybe not exciting for you, but this is the exact spot were Jack Parsons, Theodore VonKarman, Frank Malina were testing their rocket motors in the late 30's. Those experiments eventually led to the founding of Aerojet corporation and JPL in the 40's.

SStS set to start work on next phase

2011-01-25T10:41:00.001-08:00

Sugar shot to Space is set to begin work on the next phase of motor/rocket development called DoubleShot. With a motor coming in at around 6 1/2 inches in diameter and utilizing approximately 200 pounds of propellant it should be a good show.

Additional launch Photos

2010-07-27T10:26:00.000-07:00

As usual, my good friend James took some nice photos on launch day. I really like this one looking down the launch tower. You can see a few more photos on his blog.

Launch Day

2010-07-18T12:37:00.000-07:00

I had a lot of fun at the launch. The new motor performed really well . The flight went well and the chute was deployed at apogee. Unfortunately the parachute separated from the rocket and it came in ballistic. The good news is that most of the motor survived and may give some clue as to what caused the recovery failure...more on that later. I don't think many of the AIAA members had ever seen a "sugar" motor before and I think a lot of them were surprised and impressed.

Many of the competing teams seemed to have a tough time of it with several launch pad mishaps and a few in flight failures. By the afternoon though there had been some nicely executed flights. Overall it was a good day and it was pretty cool to see so many people participating. There are a handful of other photos here.

Launch update

2010-07-13T18:16:00.000-07:00

Change of plans. Once I started looking into what actually had to be done to prep the camera rocket for this weekends launch, I realized that there was actually more to do than I had anticipated. Coupled with the fact that I'm not going to be able to go out early to cast the the propellant for that larger motor it became apparent that I needed a plan B. I quickly decided that I could modify an older/retired aeroshell to fit the 2.375" motor that I have been working on. The initial static test of that motor ended abruptly, but I modified the design and it's been ready to be re-tested for some time now. Finding the time has been the issue so plan B seems like the way to go; I get to fly something and test the motor. I still need to document the changes to the 2.375" motor, but basically three things changed: I went back to a propellant formulation that I know well (60/40 KNSB), I redesigned the core to be stepped to help address any erosive burning issues, and I'm using a smaller igniter. I chose the 60/40 ratio to help reduce the chamber pressure as KNSB has a higher burn rate then the KNERSB formulation that the original motor test used. At least in theory. While the ambient burn rate that I measured fell in between KNSB and KNER, I'm not convinced that the burn rate at operating pressure behaved the same way. The initial testing of the KNERSB propellant didn't seem to exhibit some of the same characteristics of KNER propellant, namely difficulty with ignition or slow start up. The failure mode was over pressurization which resulted in the forward bulkhead being blown out. I felt that the last test had too many new things going on: new propellant formula, High L/d. Having made changes to address both, I feel confident enough to try a flight test. Hey, that's why they call it experimental rocketry!

Anyway, I chopped the black and orange rocket into pieces. Once I get the pieces put back together it should look basically the same from the outside. It's kind of exciting refurbishing an old rocket that probably last flew in 2002-2003. The largest motor that boosted this aeroshell was a K-class motor and the 2.375" motor is an L-class motor, so it's a bit of a step up in thrust. Parachute deployment will be handled with a timer. I'm leaving out the more expensive altimeter because of the untested nature of the motor, but I am going to include a video camera because you want video even if things go wrong. Pictures of the new rocket to come soon.

Upcoming rocket launch

2010-07-06T13:14:00.000-07:00

The Reaction research Society's next launch is scheduled for the 17-18th of this month. This particular launch is specifically set up for the American Institute Aeronautics and Astronautics (AIAA) Young Engineers competition. I found this description of the competition online. In addition to the competition, members are encouraged to participate in the launch with their own projects. My latest motor project (the high L/d motor) is ready for another static test, but I really feel like flying something. Once I read a description of the vehicles they are planning to fly (four inch diameter with an expected altitude of 15,000 ft), I decided to fly the latest version of my camera rocket (four inch vehicle with an expected altitude of 18,000 ft). You can see the latest version here and the camera and overall configuration here. My intent was to fly this quite a while ago, but things got busy and I never launched it.

MISSILES: Up on Solid Fuel

2010-01-07T12:05:00.000-08:00

MISSILES: Up on Solid Fuel

I came across this short article from 1958 about Thiokols entry into the field of rocketry. I like this sentence "By 1953 Thiokol had produced solid-fuel engines, ie., basically cylinders packed with the fuel, for the first full-scale Army test missiles."

New Sugar

2010-01-06T08:27:00.000-08:00

I ordered a new batch of Erythritol. The previous brand that I used was Zsweet and the new stuff that I ordered is NowFoods. I have used Sorbitol from NowFoods before with very good results. It'll be interesting to see if there are any differences in the casting of the two different brands. I'll start by trying a straight KN/ER segment per the original design and see how that casts.

I've also made a new bulkhead and motor casing. The casing is identical, but the bulkhead is slightly different in that it has provisions for both the igniter and the pressure port. I had some concerns about the amount of wire that was in the motor at the last firing. Initially I thought that maybe the igniter had gotten bunched up and wasn't able to clear the nozzle thereby causing the over pressurization. We found the igniter shortly after the test though and it was clear that it hadn't plugged the nozzle and had been cleanly ejected from the motor. But why take any chances.

Amateur Experimental vs High Powered Rocketry

2010-01-04T08:31:00.000-08:00

The other day someone that knew I was "into" rocketry said, "I saw this show on TV where these guys put rocket motors onto a ten foot mock up of Dorothy's house from the Wizard of Oz and shot it into the air". OK...so I saw this show, it was entertaining, but that's not the type of rocketry that I'm "into". The above example falls into the High Powered Rocketry or HPR category for me. To be fair, it is at one extreme end of the HPR spectrum. I'm not at all against HPR, it's just doesn't really excite me. Assembling a kit, commercial motor, propellant, and flying it doesn't teach you the engineering of rocketry or at least it doesn't take you very far below the surface. I know that some HPR launches have "experimental" days that allow people to fly motors that they have made with propellant that they have cast themselves, but even at those launches most of the motors are of a very similar design and most of the propellant is just a slightly different variation of the same stuff.
The photo above is of a two stage vehicle built and flown by Bill Claybaugh at the RRS last October. The booster is a cluster of four RRS "class" motors and the sustainer is a single "class" motor. The class motor was developed by the RRS to use for their introductory solid propellant class that they've taught for a number of years. It's been a while since I took the class, but as I recall the motor produces around 300lbs. of thrust for three seconds, so the booster propelled this thing out of the tower with 1200lbs. of thrust. I don't think this is the most interesting amateur rocket that I've seen, but it would certainly look right at home in the pages of Richard Morrow's "Small Sounding Rockets". I can't help but think that the same five motors at a HPR event would be lazily propelling a scaled-up version of some Estes model rocket to three or four hundred feet.
It's not unusual to go to a launch at the RRS or FAR and see half a dozen rockets fly, far fewer than you would see at a typical HPR event. The difference is that those six rockets would likely be completely different from each other. Solids, liquids, Lox/Kerosene, Hydrogen Peroxide, Steam, Zinc/Sulfur, Sugar, HTPB, and on and on. Now that, I'm into!

Static Test Video

2009-12-21T13:36:00.000-08:00

Here is video of the test that my friend James took. Nice quality footage. Apparently I laugh like Santa Clause when rocket motors fail.

"Test Complete"

2009-12-20T14:12:00.000-08:00

One of the very first large solid rocket motor static tests that I witnessed was out at the RRS nearly ten years ago. That motor was huge, 12 inch diameter if I remember correctly. A couple of seconds into an 8 or so second planned burn the casing failed... spectacularly! The first thing I heard was Dave Crisalli on the PA system calmly declare "test complete!" I was hooked, this amateur rocket thing was for me.
Ok, so yesterdays failure was not nearly as spectacular, but a fraction of a second after ignition I heard Dave's voice in my head declare "Test Complete". I have a couple of theories on what went wrong and a ton of video that I will post. The likely cause of the failure was probably a combination of things, but I think the leading cause was not the motor design, but how we retained it to the "test stand" and the pressure port....more on that later.

In the first image you can see the motor is up to pressure. In the second image (separated from the first by 1/30th of a second) the bulkhead has been blown out of the casing. The third image shows one of the two camera's close to the motor and the pressure gauge in the lower right hand corner on their way out. The fourth image shows the casing and nozzle "landing" after a full ten seconds in the air.

I'll need to make a new casing and bulkhead, and with a few small adjustments to the design I should be ready to test again soon. There were a couple of interesting observations concerning the alloyed sugar propellant that I'll post once I get the videos in order. Overall, I think the KN/ER/SB has advantages over KNER or KNSB and I'm going to continue down this path for a while.

Test Date

2009-12-14T09:02:00.000-08:00

Looks like I'll finally get a chance to test this motor this Saturday the 19th at the FAR site. Thanks for the suggestion Ben.

Here's the starter grain. Easily ignitable, fast burning KN/SU/RIO. For this test a standard BP igniter strung through the nozzle will be used to initiate ignition since the port in the bulkhead will be used to measure chamber pressure. This is approximately 15 grams of propellant.

2.375" Motor

2009-11-29T20:25:00.001-08:00

Well November went by and I didn't get much done on the new motor. I did do a little testing with Erythritol based propellant. My first attempt was a little surprising given the fact that others have expressed that the combination is really easy to work with and cast. I found that the Erythritol based propellant "froze" quickly once removed from the heat source. Casting was challenging at best. I think there may be at least a couple of different factors at play. In my initial attempt I used a stainless steel pot which has thin walls and not much ability to retain heat. The other possible factor is the brand that I used. In contrast to the pure white Erythritol that other experimenters are using the brand that I have seems to have a hint of color which means that it may have some contaminant that is affecting it. I don't think that the quick freezing of the propellant is something that could not be overcome, but since I tend to cast out at the RRS facility where it's difficult to escape the wind and sometime surprisingly cold weather. Since I have around 50 lbs. of Sorbitol I decided to try an alloy of fuel consisting of 50/50 Sorbitol/Erythritol. This combination cast very well and was cured enough to remove from the mould after about 1.5 hours. A test strand had a burn rate that fell right in the middle of KNSB and KN/ER, so I'm expecting motor performance to be roughly the average of the the two fuels. Expected chamber pressure is expected to be around 1250psi.
The first image at the bottom is a sample segment of KN/ER, the middle image is a segment of KN/ER/SB, and the top image is a frame of the test strand burn test of the KN/ER/SB.
The RRS Christmas party/launch where I was expecting to test this motor was canceled this year so I'm hoping to find some time between Christmas and New Years to test.

Casting Tools

2009-11-04T09:13:00.000-08:00

I haven't had much time lately, but the 2.375" motor project is moving along. The 2.375" motor project...hmmm. I have never a given a motor or rocket project a name. I usually refer to them by color, some key feature, or size like the orange and black rocket, or the camera rocket, or the 2.375" motor. I think I'll try and come up with a name for this motor, maybe something from Norse mythology since the high L/D of the design makes me think of the motor of one of my favorite sounding rockets the Loki dart.
I should be ready for the first test firing which is tentatively scheduled for early December. I modified the one existing casting set-up that I had for the original 2.375" motor to accommodate the slightly smaller diameter casting tube size. That set-up worked well in the past. The t-handle is removed during casting so it doesn't get in the way. Once the propellant is cured the handle is used to unscrew the mandrel from the base which pushes it part way out out of the propellant segment making mandrel extraction pretty easy.
The other two are simple hardwood bases coated with epoxy to maintain dimensional stability and keep them from absorbing the grease which will be used to keep the propellant from sticking. The coring rods are Delrin, which I haven't used before. Apparently Delrins thermal expansion properties allows them to basically fall out of the propellant once fully cooled. Basically the coring rod takes longer to return to ambient temperature than the propellant allowing the rod to shrink a bit more than the propellant.

Ares x-1 Launch

2009-10-28T09:57:00.000-07:00

There is some good video of this morning Ares launch. The second video as some cool camera angles. Everything apparently went as planned, I guess the payload seperation wasn't as dicey as it looked.

2.375" Motor Updated

2009-10-25T15:25:00.000-07:00

I changed the design again. I decided to optimize the it for KNER propellant by adding two additional segments. The additional propellant brings the motor up to a solid L-class motor and the chamber pressure sims. at right about 1000psi. I'm hoping to have an opportunity to test fire it for the first time in early December

Update: I updated the SRM output to correct a mistake. I had been using the wrong grain OD.

2.375" Motor Update

2009-10-23T22:15:00.001-07:00

I've completed a couple of the wooden pyrogen canisters. I also ran a new SRM simulation with KNER propellant. The result of switching from KNSB to KNER is that the burn time basically doubles and the chamber pressure is cut to about half. The drop in chamber pressure results in a bit of a drop in Isp, but for my first KNER test I'm fine with that. A sugar motor this size with a four second burn time should be pretty cool and at this point the purpose of this test is to get some experience with KNER and test the pyrogen design.

2.375" Motor Update

2009-10-20T16:48:00.002-07:00

I've been talking with Magnus from AIR recently about this motor and he has convinced me to use erythitol based propellant. I first heard about erythitol on Scott Fintel's site and the biggest attraction seemed to be ease of casting as well as a decent Isp even at relatively low chamber pressures. One of the other attractive things that Magnus has pointed out to me recently is that it functions well in a motor with a high L/D. Click here to see Magnus' latest motor that utilizes nine segments and has an L/D of around 15. One slight drawback is that it's hard to ignite, but from a safety stand point this is actually a good thing.
I'll keep the length of the motor the same for now, but in the future I could conceivably lengthen the casing and add two propellant segments without any additional changes and increase the total impulse by about 36%. The resulting increase in Kn would increase the chamber pressure, but it should still be well within the design limitations of the casing and the closures.

Rather than using a hotter igniter, I have decided to add a simple pyrogen cannister to aid in ignition. The design is a small wooden cup that will have a KN/SU/RIO propellant cast into it which will be ignited by a "standard" BP igniter. For added safety, the igniter will be inserted through a NPT plug fitting that can be screwed into the bulkhead just prior to testing. The cup will have a burst diaphragm attached to help ensure a quick ignition of the pyrogen grain.

Wood may not seem like the best choice, but I used a wooden disk in the original design to insulate the bulkhead and it was reusable a surprising number of times with just a bit of refurbishing each time.

Reaction Research Society, 1958

2009-10-16T13:30:00.000-07:00

I just noticed that the RRS website has a pdf of a 1958 Popular Mechanics article reporting on the activities of the society. It's fun to think what it would be like to have been alive at some point in history, whether it be in the midst of the "space race" or some other time. It's nice to see that while much has changed since 1958, the essence of what the RRS and other similar organizations stood for then still exists today. Whether it's medium or small size companies competing with big ones, or organizations that not only encourage but facilitate education and experimentation, or small organized efforts like SStS, the spirit of competition, exploration, and experimentation is alive and well. No need to travel back in time.

2.375 inch Motor Update

2009-10-14T22:10:00.001-07:00

I finished drilling and tapping the nozzle and bulkhead. I also got the o-rings, so I'll test fit everything soon. I need to start thinking about casting bases and mandrels for the propellant; I may have some from the previous motor that I can just modify slightly. If not, I'll make some new ones.

Interesting Rocket Motor

2009-10-14T21:50:00.000-07:00

I saw this motor on EBay, the other day. I bid on it, but unfortunately didn't win. The description said that it was 13 inches long by 4 3/8 inches in diameter. There was another (really blurry) photo looking down the nozzle that showed a graphite insert.

New Motor, Finished Bulkhead

2009-10-11T15:58:00.000-07:00

I finished the bulkhead. I varied from the drawing a bit by adding a pressure port so that I can measure the chamber pressure during testing. I need to order some o-rings and then I'll be able to test fit everything.

New Motor, 3D Model

2009-10-09T17:58:00.000-07:00

I'm working on making some animation to show how this motor goes together. I did a couple of cross sectional views that pretty much show just that. In the close up view you can see the nozzle and the insulation (the reddish colored stuff). The original version of this motor didn't use any insulation. With the short burn time and steel casing , it's really not necessary. I added insulation to this motor as the plan is to eventually epoxy fins directly to the casing in order to construct the rocket

2.375" Motor, Nozzle Update

2009-10-04T20:24:00.000-07:00

I pretty much finished the nozzle. I used a parting tool to cut the o-ring groove and the groove where the insulation fits into. I then parted it off, flipped it, and cut the convergent side. I still need to drill and tap the retaining screw holes and I'm planning on adding some "gun blue" or similar rust resistant finish.

2.375" Nozzle Update

2009-09-27T22:15:00.001-07:00

I finished the back cut on the shoulder area. In an attempt to get really clean flow into the throat area, the convergent starts at a steep 45 degrees that leads into a shallower 22.5 degree section leading into the throat. This can be clearly seen on the back of the convergent side in the photo. I also chose a shallower divergence than the "standard" 12 degrees. A couple more hours and I should have a finished nozzle.

2.375" Motor, Nozzle Progress

2009-09-27T15:11:00.000-07:00

I'm making pretty good progress on the nozzle. The black line in the top few photos is about where it'll get parted off. I still need to cut the 0-ring and insulation grooves, do the back cut behind the shoulder, and index the retaining screw locations. Then I'll part it off, flip it over, and finish the convergent side.

2.375" Motor, Starting Nozzle

2009-09-25T08:26:00.000-07:00

I managed to start the nozzle. I'm starting with 2.75" diameter stock which is less than ideal; I would prefer to start with some thing closer to the OD of the finished part, but it's what I have on hand. It shouldn't be too bad though since I added a new, larger motor to the lathe a while back. I've only done some light turning with the new motor, so I can't wait to find out how aggressive a cut it'll handle. The starting piece is about an inch and a half longer than the finished part will be and weighs nearly nine pounds. I would guess that the finished nozzle will come in at around 1/2 lb. The general plan is to machine the divergent section, throat, shoulder, and index the retaining screw locations. Then part off the nozzle, flip it, and finish the convergent side

2.375" Motor Casing Completed

2009-09-20T22:14:00.000-07:00

I finished the casing for the motor. I realized that I made a mistake in the CAD drawing that I posted earlier today. There should be six retaining screws for both the nozzle and the bulkhead versus twelve. I also made a slight change to the length of the casing, opting to make it 3/4"shorter which allowed me to true the ends on the lathe. I hadn't planned on being able to do that but by turning the tool post backwards I was able to extend it's capacity by just enough. Since just a very light cut was needed this worked fine. The design is pretty generous in the propellant segment spacing, so I'll make up the deficit by reducing the spacing slightly.

The bottom photo shows the new extended casing next to the older motor design. The new casing still has it's rust preventive zinc coating. The coating doesn't add any structural strength and has a fairly low melting point so I'll remove it with a quick dip in some muriatic acid.

2.375" Motor, Completed CAD (nearly)

2009-09-20T13:03:00.000-07:00

I'll need a few more dimensions, but I'm pretty much ready to start. I'll start with the casing , then I'll be able to determine exactly what the OD of the nozzle and bulkhead needs to be.

2.375" Rocket Motor Design, Nozzle

2009-09-17T16:40:00.000-07:00

I haven't done a lot of additional work on the design. I'm not sure that I'll remove the material indicated in red in the first image, back cuts like that can prove to be pretty time consuming. I should be able to shorten the shoulder a bit once I add the bolts into the design; that would make it a bit easier. I'm not too concerned about making as lightweight a motor as possible, but the aft end of the motor is a good place to remove weight from since additional weight in this area pulls the center of gravity aft. This isn't necessarily what you want since the likely result is larger fins to compensate. I'll wait and see how it goes while I'm machining it; I can always revisit the nozzle at a later date.

Cadillac Launch

2009-09-16T22:05:00.000-07:00

I don't think of myself as someone who is easily influenced, particularly by advertising, but the other day I saw a car commercial that totally convinced me that I wanted to have this car. I've been considering getting a new car, but a Cadillac. Never! But it seems as if GM geared this commercial directly at me (or at least anyone interested in rockets, aviation, etc). After seeing it once, I decided I really wanted this car. That has to be good advertising!

Here is the commercial:

Rocket Motor Design, Initial CAD

2009-09-12T17:26:00.001-07:00

Here is the first pass in CAD. I like to get to this point and then live with the design for a while and see how I feel about it after a day or two. I like the overall look of this motor, so I'll probably try to finish the drawing tomorrow. After I finish it, I'll point out some of the features as well as some of the things to consider during the design phase. Then I'll create a 3D model, at least of some of the components.

NASA ARES-1 DM-1 Rocket Motor Static Test

2009-09-11T13:32:00.000-07:00

NASA ARES-1 DM-1 Rocket Motor Static Test at ATK, originally uploaded by S. Hurley.

I saw this image on Dick Stafford's rocket dungeon blog. Sorry for using the same image Dick, but you picked a pretty good one :)

Given my post on steel castings yesterday, I thought it might be worth noting that this motor uses a steel casing. Shuttle boosters use a four segment steel casing, and this motor was essentially an extended version of a shuttle booster utilizing five segments. I also read on the Arocket list this morning that the casing sections used for this test were actually flown on STS-1 and have 48 missions on them. I was a little sceptical but I found this article on the NASA site which states "... the cases used in this Ares I first stage ground test have collectively flown on 48 previous shuttle missions, including STS-1, the very first flight.

The video of this test is awesome and definitely worth watching!

Motor Design, Casing

2009-09-10T14:31:00.000-07:00

The material that I've chosen for this design is the same as the original; steel. Specifically, fence post material available at the local home improvement store. It has an OD of 2.375" and a wall thickness of 0.049". I've had guys from the high powered rocketry community tell me that steel is dangerous and that it's a poor choice for a rocket motor casing. I think this stems from the fact that the governing bodies for hobby rocketry forbid the use of steel. I'm not sure how this rule came to be, but in commercial/military applications steel is a perfectly acceptable casing material. I think that the argument against steel goes something like this: Steel is denser than aluminum so for a given fragment size the steel contains more energy and will travel farther. Another way to think about it is if an aluminum fragment from a motor over pressurization were to travel 10 feet, then a similarly sized fragment would travel, lets say 15 feet. Therefore steel is more dangerous. I think the argument for steel would be I'd rather not stand near any pressurized vessel no matter what material it's make of, I'll be 50 feet back in the bunker thank you very much. Since my intent is to only test and fly this motor at the RRS, which isn't run under the same rules as hobby rocketry, steel my choice.
The other thing to consider is that not all steel is the same. This material is highly ductile and in my experience doesn't fracture. It tends to split, but stay in one piece. Take a look at this steel casing failure of an early SStS motor test that I conducted.

Others have experienced the same results. Look at this image of a ruptured casing that Richard Nakka experienced during the development of his epoch motor. You can read his thoughts on steel casings here.
Steel casings have been a favorite of mine for a while. Here is an image of some of the motors that I've made that utilized steel casings.

Motors one and two are an A-100 and B-200 made to the specs found on Richard's site. Motors 3-5 are variations on the B-200. Number three was an attempt to make as light weight a B-200 motor as possible. I used the base of a touchier lamp that I found in the trash for the casing. It was an incredibly light weight steel tube with a wall thickness just under 0.020". That was a great motor back when I was flying it. Motors six and seven were good motors, I discussed them in an earlier post here. Number eight is the motor that I'm updating now and number nine was a workhorse of a motor that used 2.5" emt (electrical metallic tubing) with an actual OD of 2.875". You can see that motors performance in an earlier post here. To get back to this design, lets look at the numbers I came up with using Richards Motor Casing Design software.
This is a very handy tool. You enter in the dimensions and material properties of the proposed casing. It then tells you the the design pressure, burst pressure, elastic deformation under pressure, and design and burst safety factors. If I use 01 as the design safety factor, I find out that at around 1800psi the materials yield strength would be exceeded and I could expect permanent deformation to occur. Knowing this I will design my closures (a radial bolt pattern) to fail at around 1800 psi. That way if I want to add a burn rate enhancer to the propellant, as I did here, and run the motor at a higher chamber pressure, I'll have the flexibility to do so. Also there is no point in running the motor at a chamber pressure that would damage the case, at least not for this design.

Next I will draw out the desing in CAD so that I can start to visualize it better.

New Motor Design, SRM

2009-09-09T12:00:00.000-07:00

Using Mr Nakka's Solid Rocket Motor Design spreadsheet, I came up with the basic design of my new motor.

The dimensions of the motor casing are determined by the casing material. For this motor I have chosen to use the same material that I used in the original motor. The material is steel fence post material available at most home improvement stores. It has a 2.375" diameter x 0.049" wall thickness and I paid around $10 for 5 feet of it. (More on the use of steel in a later post) The next step is to determine the propellant grain geometry. The grain geometry offers a lot of room to play around with. For this motor I know that I will be using two inch mailing tubes to cast my propellant segments into, so that sets the outer diameter of my grain at two inches or 54mm. Then I played with the individual segment length and core diameter in an effort to produce a nice neutral burn profile as seen in Graph 1. The next decision I made was to increase the number of segments to six versus the four segments of the original motor. This essentially increases the total impulse by 50%. The resulting motor is on the long side with a L/D of around 10, but it shouldn't present any serious issues.

The next thing that I did was to lower the grain density ratio from the default of .95 to a more likely .093 given the fact that I don't want to spend a lot of extra time processing propellant for this motor and the performance lose is small and in this case perfectly acceptable.

The last thing that I did was to determine the Kn range that I wanted this motor to operate at. I chose 375 as the starting Kn which results in a max chamber pressure of around 1100psi.

The spreadsheet uses the grain geometry and Kn information to determine the nozzles throat diameter. It then takes all of that info, plus assumed combustion efficiency, nozzle efficiency, and other data and gives us our first glimpse of the designs performance.

It also gives you a nice summary of the key parameters of the designs performance.

Next step will be to take a closer look at the casing and come up a bolt ring design to retain the nozzle and bulkhead.

Designing a New Rocket Motor (step by step)

2009-09-08T15:18:00.000-07:00

I have decided to design, build, test, and fly a new rocket motor. Why not just fly one of my existing rockets with any one of the existing motors that I've already constructed? The reason is simple. I really enjoy going out to Mojave and flying rockets but the really fun part for me is the design and construction. The process is the cool thing, the fact that the culmination of that process is a rocket flight is just the icing on the cake. Plus it's been at least a couple of years since I've designed a new motor and I miss it. The one thing that I plan to do differently than in the past is to document the entire process right here.

The motor that I've been thinking of is an updated version of one of the earliest designs that I made. Large enought to loft a good sized rocket and but not too big to be a chore to prep for flight. Simplicity and ease of use are my goal. The orginal motor was my first step away from the venerable B-200 motor designed by Richard Nakka and was influenced by Richard's Kappa motor development. It was in the same class as the Kappa motor with a similar propellant configuration. I chose to use steel for my motors casing to simplify the design. I also utilized a retention groove in the nozzle and bulkhead which provided a recess for the retention screws which engaged into threaded holes in the casing. This was a holdover from the B-200 design and though simple to implement, in this larger diameter motor didn't prove as hardy as in the smaller diameter motors. While I never experienced a failure, the screw holes would get torqued pretty well and the casings would need to be replace frequently.

Anyway here is a picture of that original motor as well as the nozzle drawing that I did. I love that it has oil splatters on it from hanging behind that lathe while I made the part.

Next step will be to crunch some numbers in SRM and come up with a working design, and some basic dimensions.

SStS Success!

2009-07-26T15:03:00.000-07:00

The Sugar Shot project reached a significant milestone this weekend with the first successful firing of the flight configuration dualphase motor. This is a design concept that many "experts" have said would never work. Congratulations to the team and particularly to Richard Nakka for never losing faith in the concept and working tirelessly to get the project to this point. This is a truly unique project that involves folks from all over the globe; to learn more about it please visit the website by clicking Here. The goal is to put an amateur rocket into space and the only incentive is to simply prove that it can be done (with a propellant which is made up largely of sugar!!). If you've ever wanted to be a part of something like this please consider making a donation. Video provided by Rick Maschek.

AMATEURS AND ROCKETS-1

2009-06-27T10:32:00.000-07:00

I was asked recently if I had lost interest in rocketry. Nothing could be further from the truth; I love rocketry as much as ever and can't foresee ever losing my interest in it. Time constraints have kept me from actually doing much, but I'm always keeping my eyes open for anything rocket related. That leads me to this post. A couple of weeks ago someone on the Arocket email list mentioned a long out of print book called Amateurs and Rockets by Humphreys. I was surprised because with as few books that have been written on the subject, I thought I knew them all. I immediately went to Alibris and found that they had three copies, one seller was asking $280, one $180, and one seller was asking just $20. I ordered the twenty dollar book and forgot about it. When I got home yesterday I found that it had arrived and after a quick flip through I was a really happy. The book was written by two members of the Pacific Rocket Society and contains numerous photos and technical drawings from the 50's and 60's. Many of them from the Reaction Research Society of which I am a member. One of the coolest images that I found was of the RRS's newly constructed launch tower. The photo was taken before I was born! The other photo is of me at least 35 years later using the same launch tower. There are a ton of other interesting photos and stories that I hope to share here.

More Old Photos

2009-06-17T08:53:00.000-07:00

These are pictures of the very first rocket that I launched at the RRS back in 2002. I hadn't bought a lathe yet and the motors were constructed primarily out of PVC pipe and fittings. It was the largest PVC motor that I have ever constructed and the last before moving on to fully machined motors made of steel and aluminum.

Old Photos

2009-06-16T08:32:00.001-07:00

This is a rocket I flew back in March of 2004. My friend Peter and I got a lot of ribbing from the guys as the vehicle was constructed almost entirely from sewer pipe. The motor utilized an unrestricted burning grain, which basically means that it lept off the ground like a bat out of hell. That's me holding a propellant segment, Peter with the rocket, leaving the ground with a bit of an arc, straightening out, and the landing site. Fun Day!

Not Rockets

2009-05-01T14:14:00.000-07:00

Other than offering a tiny bit of support to the ongoing Sugar shot project, I've been way too busy to do any real rocketry work. On top of being busy at work, we've decided to replace the floors at home with tile, to the tune of around 900 sq. ft. downstairs and 200 sq. ft. upstairs. I've decided to do the work myself. I convinced myself that it was a good way to save money, but the reality is that I kinda really enjoy the work. One of the first jobs that my dad had was as a stone mason, so maybe it runs in the family? It's going pretty well (I think) and I've gotten into a routine of laying whole tiles at night after the kids are asleep. By morning the mortar is set enough that they can walk on the tiles without causing any problems. Then on the weekends I cut and lay the smaller perimeter pieces when I can use the saw without annoying or waking anyone. In the bottom photo is how the floors looked before, and the other photos show the progression of the dining room area. Grout, baseboards, new carpet (on the stairs and upstairs), and paint still to come. Anyway, if anyone does actually follows this blog, stay tuned as I hope to get back to some rocketry work later in the year and finally fly this rocket.

We once had a Rocket

2009-04-28T17:58:00.000-07:00

Mike Roberts posted a link to this interesting documentary film on arocket today. Mike reports that it was inspired by Francis Spufford's book "The Backroom Boys" and it's called "We Once had a Rocket". It documents how the engineers responsible for Black Arrow went ahead and launched the rocket with the satellite Prospero despite the government having just cancelled the whole programme. It includes a number of interesting interviews with some of the guys who worked on Black Arrow at the time. As others have pointed out on the arocket list, it seems unlikely that the government didn't authorize the launch, but the idea makes for a more dramatic story. Either way the video is interesting and worth a view.

Finocyl Propellant Segments Fired

2009-04-13T16:40:00.000-07:00

Rick Maschek successfully conducted a static test of the small test motor which used a finocyl core geometry for the SStS project. This is exciting because of the possibilities that complex core geometries open up. Many of the most impressive small sounding rockets utilize a monolithic grain segment with a complex core geometry. Arguably on of the earliest and most successful is the Loki dart which could deliver a small payload to 34 miles despite being only three inches in diameter. It used a simpler cruciform core design.

Photos and video courtesy of Rick Maschek.

Finocyl grain testing

2009-04-07T17:44:00.000-07:00

The Sugar shot project has begun testing finocyl grain geometries. Rick Maschek is doing a great job of actually casting the segments. Rick has managed to remove the mandrels with ease , something that is notoriously difficult with complex cores, by cooling it first by running nitrogen through the center of the mandrel. Ed at true-core fabricated the mandrel designed by Richard Nakka. I supplied a short 2 segment casing to work with the Blast Tube Motor that I designed to test ablative samples. Really interesting work that I wish I could be more involved with.

Pictures of last months launch

2009-02-14T09:19:00.000-08:00

My friend James took some great pictures of the zinc/sulphur rockets at last months RRS launch. Zn/S rockets typically leave the ground like they're being shot out of a cannon, so many photos I've seen only include a column of smoke but no the rocket.

You can see the rest of Jame's photos from the day on his Picasa site here. The day was pretty overcast and there were some really cool cloud formations late in the day. James captured a great panorama of the approaching storm clouds that he posted on his blog here.

Two Wheeled Rocket

2009-02-09T22:11:00.000-08:00

The other day a friend at work rode in his friends Ducati Desmosedici RR, and I got an opportunity to look over this awesome machine in person. Not a true rocket, but an incredible machine none the less.

Great Weekend!

2009-01-25T12:59:00.000-08:00

I attended the RRS launch this weekend. It was a great launch and I had tons of fun. Rick Maschek and I fired a motor that was part of ongoing testing for the Sugar Shot to Space project. There were at least 12-13 small Zn/S rockets flown, a 4000lb thrust LOX/kerosene static test, and a variety of other flights and tests.

PACS-1 Ejection Motor

2009-01-12T18:04:00.000-08:00

I recently got this small rocket motor. It's about the size of a large coffee can. The base says PACS-1 Ejection Motor with a logo underneath that I believe is the Atlantic Research Corporation logo. My guess is that it's from the 60-70's based on the hand engraved serial numbers, coffee stained base, and light patina that had accumulated on the nozzle half of the motor. It did clean up pretty well though as seen in the above photo. It looks like a large central nozzle surrounded by the four smaller nozzles (two of which are canted 45 degrees and all the smaller ones are plugged). I'm guessing the the nozzle consisted of at least a couple of parts and that the convergent section and throat were recessed. Those sections are not included so the visible divergent section is only part of the nozzle included. The two halves unscrew and the gold anodized half is lined with rubber and has a variety of inspection stamps. There is also a central threaded "neck" were the igniter is likely intended to go. I'll post some more pictures when I get a chance.

How Much Inhibitor?

2008-12-08T08:58:00.000-08:00

On the Sugar Shot project we've been talking about, among other things, how much inhibitor is actually necessary to inhibit the propellant surface. I suspect that it's less than what most of us would guess. A few years back I made several motors that were designed around a readily available source of casting tubes, ie paper towel and toilet paper rolls. The motors worked great and have been fired with Fructose, Sorbitol, and Xylitol based propellants. These "casting tubes" with a wall thickness of just 0.020" seemed to do the job quite well. It makes me wonder just how thin one could go. In the last photo, the kraft paper casting tube can be seen inside of the red rosin paper used as insulation. I was expecting to be able to use a bit more insulation, but in practice the fit was tighter than I was expecting. I considered making slightly smaller diameter casting tubes to allow more insulation, but that goes against the original design intent. I then considered switching to a different insulation, but with the relatively thick casing wall and short burn time the casings on this motor seem to come through a firing none the worse for wear. There are other thin insulation material that I may try in this motor in the future.

LR-101 Combustion Chamber

2008-11-24T16:20:00.000-08:00

A nice looking LR_101 combustion chamber/injector recently sold on EBay. These seem to be getting scarce as the prices are rising fairly quickly. I've seen several of these fired at the RRS. The most memorable one just managed to clear the tower before rust in the internal passages clogged the injector and caused the fully loaded rocket to come crashing down to the ground at the base of the tower and directly in front of the (substantial) spectator bunker. Cool!

More machining for Sugar Shot to Space project

2008-11-18T10:58:00.000-08:00

I recently finished some more light machining for an upcoming static test of SugarShot's ProtoSShot-M Mark II motor. The work included cutting the casting tubes to length and making a new set of support rings. A recent Short Stack motor test utilizing titanium casting tubes revealed that they did not hold up as well as was expected. (see image below) That lead to a decision to use thicker walled titanium casting tubes, as well as several other minor changes. The move to thicker tubes necessitated the need for a second set of segment rings to be made.

MiniSShot Motor Parts

2008-10-19T10:55:00.000-07:00

I just finished some grain support rings for an upcoming firing of the Sugar Shot to Space ProtoSShot-M Mark II motor. This will be the second firing of what is essentially the full, dual-phase, flight weight motor for the MiniSShot vehicle. While the motor was pretty sophisticated from the beginning, at this point I would say it's one of the of the most sophisticated amateur designed solid propellant rocket motors I've ever heard of. Some highlights of the design include a three piece nozzle, thin walled fiberglass casing, extensive use of a variety of ablative materials (commercially available asbestos based material, cork, and epoxy/glass), and major components made from steel, aluminum, and titanium. For more information and official updates on the Sugar Shot to Space project visit http://sugarshot.org/

Cutting Metal

2008-10-06T08:21:00.000-07:00

I cut some propellant segment spacer rings this weekend for the Sugar Shot to Space project. It's been a while and it felt good. We moved a while back and I just recently have had the time to build a workbench, shelves, and unpack some tools. My friend Peter and I wired some new outlets on the wall behind the bench. I'm pretty excited about the new shop. At the old place I had no space, poor lighting, and ran all the tools off of one outlet and an extension cord.

The Largest Solid Rocket Motors Ever Flown

2008-09-22T15:57:00.000-07:00

This is just one of the many cool images from a book titled Nasa: Visions Of Space. A book that combines two of my favorite things; Art and Rocketry. Painted by Maria Epes as part of the Nasa Arts Program, the scene depicts one of the SRB's undergoing recovery testing in July of 1980. I love the sense of scale that you get from this image, those things are huge!

United Technologies Center Rocket Motor

2008-08-12T22:04:00.000-07:00

This item is currently up for auction on eBay. Unlike the actual (Altair?) motor that I found for sale on eBay recently, this one appears to be strictly a model, perhaps of an actual production motor. It does seem to be proportionally similar to the Altair motor. The model is described as being 15 inches tall with the embedded nozzle measuring 2 7/8 inches. It's not clear if the nozzle measurement is length or diameter. The current asking price seems pretty high, but as far as models go this one seems pretty nice.

Successful Launch!

2008-08-05T22:21:00.000-07:00

While not the largest rocket I've ever launched at a meager 8lbs and 4 ounces and a mere 21 inches in length it was definitely in the top three; Big sisters Grace and Lily rounding out the top three. This one is known as Theodoor Stephen after two of his great uncles. Mom, Dad, and two previous launched projectiles all doing well.

Static Test Results

2008-07-02T22:32:00.000-07:00

I finally got around to looking at the data from the static test from back in April. The motor was mostly comprised of hardware from a previous motor that I lengthened to make room for another propellant segment. That results in the initial Kn rising from 340 to 425. The other big difference was that I added 1% RIO to the propellant. I also changed the closure method from snap-rings to a bolt-ring closure designed for the increased chamber pressure. The propellant grain consisted of 5 segments in a bates grain configuration weighing 9.247 lbs with a port/throat ratio of 1.5625. The propellant was mixed in a ratio of 65/35/01 (KNO3/Sorbitol/RIO) and cast into 3" mailing tubes that have an ID of 3" and an OD of 3.125". The casing insulation consisted of four layers of rosin paper. The casing and bulkhead are fabricated of 6061-t6 aluminum. The nozzle is fabricated from 12L14 "leaded steel" and had a throat diameter of 0.64" and an expansion ratio of 12.

The total impulse was 1213 LB-Sec (5395 N-Sec.) making it a small M-class motor. I was also pleased to find that the calculated ISP was 131. Slightly higher than I expected given the fact that I didn't spend a lot of time premixing the propellant ingredients and used the KNO3 as received.

There was no measurable throat erosion post firing and the nozzle appears to ready for another firing. When I took the motor apart post test I found that the insulation was severely breached at the bulkhead end. I think that the higher chamber pressure created a much harsher environment for the insulation than I was expecting. The insulation breach resulted in a small blister in the casing about .125" in diameter and about .005" high. I'm happy to replace the casing since it was one of the most out of round 6061 tubes that I have ever purchased. The casing thickness provided for a fairly significant safety margin, so I'm considering pushing the design a bit by using a .065" walled casing which will allow the insulation to be more than doubled and should make for a very lightweight and powerful motor. Overall, I'm pretty pleased with the results.

Interesting Rocket Motor

2008-06-20T17:18:00.000-07:00

I'm always scanning eBay for interesting or unusual rocketry related items and recently came across this motor on eBay. I've seen other interesting things before like this small sounding rocket that I saw last year. Occasionally something really interesting shows up like this composite motor I saw last week. Unfortunately I didn't win this auction, but at least the pictures are kind of cool. The description said that the motor had been acquired from Douglas Aircraft some years ago. the overall length is 60" and the diameter is approximately 18". The tag had the following info on it:

P/N AG659-61370 QTT3 #1, Owner-NASA, 6-25-69

Pressure Calibration System

T4 Change, Model DSV4B-1-1

USC Rocket Launch

2008-04-29T22:10:00.000-07:00

Here is the video that I took this past weekend of USC's rocket. I placed the camera about six feet away from the launcher pointing towards the sky. It was two stages and got a bit squirrely at booster burn out. The booster was a P-class motor expected to deliver an average thrust of 1300 lb and the sustainer was an L-class motor. I didn't hear about the recovery. You can find out more about the USC rocket propulsion lab by clicking here.

Weekend Rocket Activities

2008-04-28T15:55:00.000-07:00

This past weekend was full of rocketry. First off I was able to see the fifth Sugar Shot motor test over at the FAR site. Look for more details and photos on the Sugar Shot site as the post test information is reviewed and analyized. My photos of the firing can be seen here.

It was also one of the busiest Reaction Research Society launches over at the RRS site that I've been to in a while. In talking with some of the other members I found out that their online gallery area has had a number of additional photos added recently. I haven't checked it out yet, but I suspect there are some great photos there. You'll have to register to view the galleries, but that's simple enough to do. Some of the highlights of the day were seven successful Zn/S rockets flown by a group of middle school kids. A static test of a film cooled 4000lb thrust engine. USC flew a large two-stage rocket. A Zn/S rocket with two nozzles at the top. I also had a good test of a 600lb thrust motor that I will be posting details of in the weeks to come. All of my photos of the RRS activites can be seen here.

Blog maintenence/missing photos

2008-04-23T14:53:00.000-07:00

I recently activated my Picasa web album which is were the images uploaded to Blogger are stored. In an attempt to clean up some duplicate images in that album I inadvertently broke a bunch of photo links to some in my earlier posts. I think I've got them all fixed now.

Photos from November

2008-03-01T22:05:00.000-08:00

Last November my friend James and I participated in a propellant class at the FAR site. James took some great pictures of the days events. The pictures above are of my KNO3/sugar motor and of my AP/AL/HTPB motor. The photo of the composite test was taken during the day but was "stopped down" in an effort to reveal the shock diamonds. Video of both of these firings can be seen here. More of James' photos of the days events are online here.

Harvesting Aluminum Flake From Paint?

2008-02-25T21:23:00.000-08:00

Richard Nakka recently added a page to his site about harvesting aluminum flake from paint. Actually, there are several new additions to the igniter page that I found intersting. I'll defer to Richard's page about the usefulness of flake aluminum as a thermic agent for igniters and the harvesting details.

I haven't had much time to devote to rocketry lately, but this technique seemed so simple and the cost was so minimal that I decided to give it a try. One thing that I noticed was that the lip on the paint can made it difficult to get all of the slurry out of the can and it was difficult to determine how deeply to insert the siphon. Too deep and you just sipon out the actual aluminum. I ended up transferring the slurry to a baby food jar for the 2nd acetone wash. Not only was it easier to get the slurry out of that container, but being clear glass I was easily able to see when the aluminum had settled. It was also easier to see the placement of the turkey baster used to siphon out the acetone ensuring that a minimal amount of aluminum was siphoned out. I ended up with a yield of 34 grams from a half pint of Rustoleum 7715 aluminum paint which is easily enough for 50-75 igniters.

Amateur Icelandic Rocketry (AIR)

2008-02-19T22:06:00.000-08:00

Magnus Gudnason and Smari Freyr Smarason of AIR recently static tested the two motors intended for a two stage project to be launced later this year. Some preliminary test results can be seen on their forum. I think that this could be one of the best "sugar" powered launches to date, definitely one to keep an eye on.

Old Launch Photos and Stuff

2008-01-19T13:28:00.000-08:00

Going through some old photos and rocket related things recently, I came across some photos from 2002. At that time two of the largest motors that I had were designed around two inch diameter "washing machine standpipe" that I found at Home Depot. I decided to try these pipes at the time because they seemed to be very good quality, good/consistent weld, and dimensionally consistent. They also have a thin (0.035") wall thickness which makes for a very lightweight casing. I designed two motors that utilized this casing material. Both motors used identical casings, bulkheads, and closures, but one was designed to use a single unrestricted grain and the other a single restricted grain. The differences in the nozzles are shown in the drawing above. I was concerned about the low initial thrust of the motor that used the single restricted grain and tried to reduce the weight of the nozzle for that motor as much as possible. In the end both motors ended up weighing nearly the same (1.75 lbs). I static tested the unrestricted motor and the numbers correlated closely to the design. Ultimately both motors flew numerous times at the RRS. They were simple to prepare on site (due in part to the fact that each needed only a single grain and that the motor was used as the casting mould). The motors proved to be durable, consistent, and fun to fly.

In the first photo you can see the casing with its nice shiny zinc coating. It is not that shiny from Home Depot, but the finish didn't take much time. Unfortunately the zinc blistered after the initial firing, so the coating was removed with a quick dip in muriatic acid. The 5th photo shows Peter and I taking the rocket out to the launch tower. The 6th photo shows (from left to right) Greg Coleman, myself, Kevin Koch, and Alan Hoyt lifting the launch tower into position. The 7th photo is Kevin, myself, and Alan. The orange and black aeroshell flew a total of five times at the RRS on three different motors. I made it from three inch diameter heavy walled cardboard tube that Kevin found in a dumpster. The fins were cut from quarter inch plywood and were epoxied on to the tube and reinforced with a layer of heavy fiberglass. The nose cone was turned from a block of pine. Eventually, it became too small for the new motors that I was making and was retired. It was always difficult to adjust the tower for it correctly since it had three fins and the tower at the RRS is built for a four fin rocket.

Photos 6-10 were all taken by Tony Richards.

Camera Rocket Recovery Photos

2008-01-01T17:59:00.000-08:00

I recently ran across a couple of photos that I hadn't seen before (here and here) of the rocket I launched in April 2007. I found the photos on the Mojave Desert Advanced Rocket Society website located here. I recognize a couple of folks in the web site's photo section from motor classes that I recently participated in including the MDARS president Kevin Metzler. The photos of my rocket were taken by Dave Allday.

Side by Side Comparison

2007-11-19T21:30:00.000-08:00

I fired two motors this past Saturday. One was an AP based motor and the other was a KNO3 based motor. Both motors were of approximately the same total impulse, but it wasn't really a fair comparison. The KNO3 motor used Xylitol for the fuel. I first heard about this sugar on Scott Fintels web site, and it was available at the local Whole Foods store. It has a low melting point and casts very nicely, the problem was that the grains took a long time to cure, weeks in fact. Anyhow, the propellant in the AP motor is fully characterized and the propellant in the KNO3 motor not so much. The side by side comparison is still interesting to watch though.

Composite motor class

2007-11-18T21:02:00.000-08:00

I took part in a composite motor class this past weekend. The class was taught by Dave Reese and was conducted at the Friends of Amateur Rocketry site. The class was a lot of fun and full of lots of useful information. Dave is currently a student a USC and I'm sure that he is very busy but despite this he did a great job organizing and conducing the class. The motor that we prepped propellant for was based on standard high powered rocketry hardware of which I have none, so I made some hardware based on drawings that I found on the Loki Research website. The hardware worked really well; I like the simplicity of the Loki design. Here is a video of the class motor that I static tested, I didn't have any instrumentation partly because I didn't want to risk any equipment on untested hardware and a propellant that I don't have much experience with, but mostly because I've been so busy lately that I just didn't have time to get anything together in time. The design/propellant is pretty well characterized though. The thrust produced should have been in the neighborhood of 90lbs with and Isp of around 185-190.

The Paul Breeds of Unreasonable Rocket were also at the site. Paul senior was flying an RC helicopter loaded with telemetry to gain information for their Lunar Lander Challenge quest.

Composite Propellant Class

2007-11-03T11:20:00.000-07:00

Later this month I'll be participating in a composite propellant class at the FAR site. The class is being taught by Dave Reese. Dave's a student at USC and was involved with this awesome project flown at the RRS some time ago. Photo by James Davidson.

Here is a picture of some of the 38mm hardware that I made myself for the class. I only had to buy the tubing. I bought enough for three casings for under $30. I had enough "scrap" pieces laying around for the bulkheads and nozzles.

Nozzle From Recent Static Test

2007-10-25T21:28:00.001-07:00

After cleaning up the motor after last weekends static test I noticed distinctly copper coloration to the nozzle. I have noticed this to a lesser degree in the past few static tests that I've conducted. I attributed it to the copper tubing that I have been using for the pressure gauge. It didn't really make sense because that tubing is upstream of the exhaust flow so it seems like any copper from the plumbing would be pushed towards the gauge, not the nozzle. There are two significant differences between this test and the others. The first is that in this firing the nozzle appeared to get much hotter than the other nozzles that I have noticed this copper coloration in, the other is that in this nozzle there appears to be little globules of copper colored material that have been driven out of the surface of the of the nozzle. the thing that I can't figure out is that these nozzles are made of 12L14 steel, which is made up of Iron, Carbon, Manganese, Phosphorus, Sulfur, and Lead. So where does the copper coloration come from?

Static Test

2007-10-22T07:31:00.000-07:00

This past Saturday I participated in a sugar propellant class at the Friends of Amateur Rocketry (FAR) facility. Brent Dougherty did a nice job presenting a general overview of how to safely work with and cast sugar based propellants. Thanks to the FAR guys Kevin, Mark, Ted and the others for letting us use the site. They have done an amazing amount of work on the site, including a massive vertical test stand (I don't remember what it's rated for).

As part of the class I fired an L-class KNO3/Sorbitol demonstration motor. The firing went well and good data was collected. This is a simplified set-up from what I've used in the past and it worked well. I'm planning on making some adjustable steel brackets that mount with bolts rather than the cargo straps. Here is the set-up:

In the picture taken just after the firing you can see the nozzle glowing red hot, once I got the motor torn apart and cleaned, everything appeared to have survived the firing just fine. The gauge measuring thrust began to register data about a tenth of a second or so before chamber pressure began to be recorded. I suspect that the pressure port was briefly clogged by the igniter initially. After tearing the motor apart I found a glob of melted plastic that used to be the soda straw that held the BP.

Terrapin Nozzle

2007-10-13T13:55:00.000-07:00

One of my all time favorite small sounding rockets has to be the Terrapin. Click here to see my earlier Terrapin post including pics and launch footage. Developed at the University of Maryland in the Mid '50s, it is a study in simplicity. It was a two stage vehicle that used existing motors, fins welded directly to the motor case, a zero length launcher, and had tremendous performance. One of the cooler pieces of Terrapin hardware has to be the nozzle from the booster. The booster was a modified Deacon motor. Here is a photo of another one of my favorite small rockets that used two Deacon motors for the initial boost. I have been doing some 3D modeling recently so I did a model of the Terrapin nozzle. I found a drawing of the Terrapin in Small Sounding Rockets which is a great book with a lot of drawings and photos. I wish the illustration quality was a little better, but I highly recommend it to any one interested in rockets/rocketry. The Terrapin nozzle appears to have been of all steel construction. It also appears to have had an O-ring seal between the nozzle and the casing liner and another between the nozzle and the casing. Retention appears to have been through a number of small roll pins (not shown in renders) I would love to see what one of these nozzles looked like after firing. Any additional info., photos, or corrections are welcome.
Anyway, here are the renders:

Nozzle Cross Section

2007-10-11T21:00:00.001-07:00

Here is a render of the new nozzle for the camera rocket. This render shows the much shorter that usual convergence section, this was done in an effort to reduce overall weight while still keeping the rest of the nozzle fairly "beefy".

New Motor

2007-10-08T08:53:00.000-07:00

Here is a 3D model of the new motor. The insulation is not shown so that the grain assembly can be clearly seen. This motor uses a ring of screws to retain the nozzle and bulkhead that are not yet shown.

Here is a view inside the casing showing a propellant segment and the insulation.

Camera Rocket, v02

2007-10-04T20:44:00.000-07:00

I've been thinking about the next flight of the camera rocket. It didn't take me long to come to the conclusion that I wanted to do some thing different, either a larger motor or a different camera orientation. Initially I gave more thought to the camera, because there really wasn't much room left in the aeroshell for a larger motor. Then one weekend while I was out in the garage I came across the motor casing from the first firing of my N-class motor. That firing suffered a breech in the insulation and a burn thought near the bulkhead. I added more insulation and at the next test had a successful firing. While this motor is much too long for this aeroshell, it turns out that diameter would fit if I removed a tiny amount of material from the heads of the retaining screws. I played around with the numbers for a while and decided that I could use the bulkhead, nozzle, and a shorter section of the casing in a workable 3 grain configuration. I was planning on using the same nozzle as the larger 6 grain motor, which would have resulted in a very low Kn or grain surface area/throat area. My plan was to increase the burn rate by adding a catalyst (iron oxide). I wouldn't have gotten the chamber pressure up to the initial design of 1000 psi, but I figured that I would be able to get it up to around 600 psi. While performance would suffer some, the overall performance should have been fine. It didn't take me long to decide on fabricating a new nozzle though. The deciding factor was weight though, not performance. The new motor would already weigh more because of the increased propellant load, so using the existing nozzle which is fairly heavy wasn't seeming like such great idea any more. The rocket has flown very well in both of it's previous flights but adding a lot of additional weight to the tail end didn't seem like a good idea. I decided to fabricate a new nozzle, well essentially a new motor. I decided to stick with the 7:1 expansion ratio to reduce the weight of the nozzle and simplify the machining. You can see a comparison between the new motor design and the previous motor that powered this rocket.
While they appear to be very similar in size the new motor should provide a 33% increase in total impulse. Once the nozzle was fabricated, I was pleased to find out that it actually weighs less than the nozzle from the 3.5" motor. Unfortunately, the shorter nozzle also means that the boat tail is going to be shorter, but I am considering extending it beyond the nozzle exit a bit. The previous flight got to 14,400' and I'm hoping this flight can get close to 18,000'. I am planning on adding another on board camera, or adding a mirror to the existing camera bay to shoot straight down. Maybe I'll do both.

Here are the basic designs of the new motor and the previous motor.

The new nozzle design.

I did a 3D model of the nozzle. This is the first time that I've done this and it was very helpful to be able to rotate around the piece before starting to actually cut metal.

Here is the finished nozzle. It looks just like the 3D model.

This illustrates the basic layout of the motor in the camera rocket (well minus the camera). When I finish the boat tail and decide exactly how I'm going to lay out the cameras for the next flight, I'll do a new illustration.

Early Dual Burn Motor Test

2007-09-19T22:03:00.000-07:00

This is a video of a static test that I conducted back in 2005 when I first got involved with the Sugar Shot project. The dual burn concept is not new, but I haven't heard of any amateurs pursuing it. At this size, I don't think you'd realize much benefit. However, in a slightly larger motor, such as the one that we are currently constructing, you begin to see some real benefits. The concept is similar to staging, but in some ways simpler to execute. One of the major difficulties is that the first half of the casing and the nozzle are subjected to twice the heating that they would have to endure in a two stage design. The motor that we are currently working on has the potential to reach nearly 50,000 feet, which is considerably higher than you would expect to go with a "standard" motor that expends all of it propellant close to the ground in denser air. Despite some minor problems, I considered this early test to be successful. The o-ring on the upper bulkhead was damaged, and I didn't have a replacement. That resulted in a small leak during the 2nd burn. However, there were several key things that did seem to work. Most notably:
The first propellant grain burned properly and ignited the epoxy plug .

The epoxy plug burned through without igniting the second propellant grain.
The burnt remains of the epoxy plug did not obstruct the nozzle.
The mid-bulkhead did not seem to have a significant effect on the 2nd phase thrust.

Norton's Surplus

2007-09-15T20:02:00.000-07:00

It's been really busy at work lately; long hours, skipped lunches, etc. I skipped lunch again yesterday, but instead of working through lunch James and I drove over to Norton's Surplus in North Hollywood to look around. Nothing has changed much since the last time I was there. The outside area had been cleaned up quite a bit though, which allowed me to get a picture of a large cylindrical motor that was nearly buried under debris last time. Four or five years ago on my first visit there I noticed a 318mm rocket motor with its nozzle pointed up in the air. It had a bunch of hoses piled in front of it. I was able to climb on top of the pile and snap a few close-up pictures. I'm not sure what it's from, but a quick Google search turned up this photo of a Little John rocket on display at the Smithsonian Air and Space museum that looks very similar. I got the photo from this blog. I took a photo of the inside of the casing . In that photo you can see four "rods" that run the length of the casing. I'm not sure what they were for, maybe they supported the propellant grain or maybe they are resonance rods like those pictured in this diagram of what I believe is a Nike Ajax motor. The nozzle appears to be all steel construction with no throat insert. The entire nozzle is badly rusted, but the throat doesn't seem to have suffered any asymmetrical erosion.

Static Firing Video

2007-09-12T21:21:00.000-07:00

I plan to start posting some videos form the past. I'll post them as I find the time, many of them were shot on an analog camcorder and need to be converted to digital. This one is a close up view of the nozzle during the second firing of the ballistic evaluation motor for the Sugar Shot to Space effort. It really illustrate well the amount of heat generated. It was a disappointing test in that the casing failed and we had problems with the data acquisition. You can find the complete report here. It did provide some useful data though and I managed to get some good video.

Minisshot Motor Progress

2007-09-07T07:14:00.000-07:00

I started threading the motor components. I've only done the six holes that connect nozzle shell to the nozzle ring, so I have a long way to go. It's exciting that those 12 holes line up so well, though. The nozzle design consists of two main pieces. The purpose is to reduce the amount of heat transfer from the throat region to the composite motor casing. The two pieces are separated by a extremely high temp. gasket. In addition to that, the shell flange has a slightly smaller diameter than the ring so that there is no direct metal to metal contact between the two pieces.

MiniSShot Motor Update

2007-09-03T16:10:00.000-07:00

I just completed the mid-bulkhead, pictured in the middle above. That's the last of the major components for the Minisshot motor. There is still a lot to do, not the least of which is to tap the 102 screw holes. It feels good to have the major metal cutting completed though. The next major milestone in my mind is putting all the components together for the first time and seeing how it all fits together. I wonder what the motor assembly time is going to be with all those screws?

Updated Profile

2007-08-28T12:51:00.000-07:00

I added a great caricature to my profile. It was drawn by a friend at Nickelodeon, you can see more of his work on his blog or website. Thanks Mike.

Forgotten Launch Footage

2007-07-26T22:06:00.000-07:00

A few weekends ago I was going through some camera stuff and realized that I had some video from my last launch on April 28th that I had forgotten about. Actually, I hadn't forgotten about it but after viewing it immediately after the launch I realized that it was badly out of focus and decided that it wasn't all that interesting. The footage that I got from the on board camera was much more interesting. Seeing it again after three months though, it seems more interesting despite the poor video quality. The camera was placed at the base of the launch tower pointed along the tower axis. The resulting footage is fun to watch because it really gives a sense of how fast the rocket left the ground. I will probably try and capture this view again next time.

Nice Static Firing in Iceland

2007-07-01T17:38:00.000-07:00

Congratulations to Magnus and friends. I saw that Magnus Mar Gudnason recently had a successful static test of his new design. Magnus and his friends have done some really nice work and I'm happy to see that he got a good test with this new motor. He has posted a lot of info on the Amateur Icelandic Rocketry forum, including drawings, photos of the assembly process, video, and results. Definitely worth checking out. I especially like that he is using a steel nozzle for this motor, for no good reason other than it looks cool. It seems like a lot of people opt for graphite when they get to larger sugar motors, I guess for the ease of machining. It should be an awesome flight when he's ready to fly it.

Minisshot Nozzle Update

2007-06-30T15:19:00.000-07:00

The nozzle ring is nearly completed. The 24 ring to casing screw holes and the 6 shell to ring holes all still need to be tapped. I'll probably have that task completed before the weekend is over. Indexing and drilling the 24 retention screw holes was more time consuming than I was expecting. The Mid-bulkhead design has 48 screw hole locations, so that will be even more challenging in that regard. I was worried about the alignment between the shell and the ring. It looks good though, the holes line up very well. I'm also pleased that it came in right at the predicted weight of 365 grams. Just for fun I looked at McMaster-Carr to see what six titanium machine screws for the shell to ring connection would cost; over forty dollars after shipping. Too expensive! The shortest ones that they had were a bit too long anyway. I may try and stop by Luky's Surplus Aviation Hardware in Burbank next week and see if I can find some there. Their prices and selection are awesome, finding the exact one that I want will be the hard part. I don't think that it's absolutely necessary, but those six screws will be exposed to significantly more heat than the ring to casing screws.

Farside Launch

2007-06-27T18:49:00.000-07:00

Here is another Universal newsreel video. This one is of a rocket launched as part of Project Farside conducted by the US Air Force in the late 50s. The first stage consisted of four Thiokol Recruit rockets, the second stage used a single Recruit, the third stage used four Grand Central Arrow II motors, and the fourth stage was a single Arrow II. The rocket was carried aloft by a large balloon and fired from an altitude of 19 miles. The system had a potential altitude was 4000 miles (6400 km). I didn't find much info about the rocket online, and what I did (including the photo above) came from here. The video features the balloon launch from the ground and shows the rocket firing through the balloon. The audio quality is a little poor and the the background music seems like a very odd choice.

Terrapin Rocket Launch

2007-06-19T18:19:00.000-07:00

I recently came across a great Universal Newsreel from 1956, showing the launch of a Terrapin sounding rocket from Wallops Island, Virginia. The site where I found it on is http://www.archive.org/ . There are a number of other interesting Universal News Reels there featuring various rockets The newsreels often times seem to have a number of subjects on each reel, some of which are not all that interesting. The newsreels are appartently old enough to fall into public domain though so I edited out the uninteresting part of the Terrapin newsreel.

New Nozzle

2007-06-16T15:58:00.000-07:00

I recently began working on a new nozzle for the Sugar Shot project. You can read more about the project here. This nozzle is intended to be used for the MiniSShot motor. This Motor is a very ambitious design being a two phase motor like our earlier BEM design and because, for the first time, we will be using a composite motor casing. The nozzle for this motor is designed to isolate the composite casing from the hot nozzle as much as possible and as such the nozzle has been designed to consist of five separate components. The nozzle consists of a nozzle ring, nozzle shell, graphite insert, heat resistant gasket, and a cast in place ablative on the inlet side. I recently completed the nozzle shell which is one of the more complex pieces that I have fabricated. I am pretty pleased with the result and plan to move onto the nozzle ring next.

Interesting Rocket Photos

2007-06-02T11:09:00.000-07:00

I recently saw some cool old photos on Dick Staffords rocket Blog, but want to add one more. I came across this photo some time ago and always thought it was really cool. It looks very similar to some of the vehicles that Dick posted photos of, probably from the same place (Wallops or White Sands) and time. I'd also like to thank Dick for mentioning my site and mention that his site is great. Nothing even remotely related to rocketry seems to get by Dick.

Amateur Icelandic Rocketry

2007-05-31T21:18:00.000-07:00

There is some nice amateur rocketry going on in Iceland. Magnus and Smari have built and flown some very nice hardware. You can see their stuff here. They recently fired a very nice looking 100mm motor that looks very similar to my 4 inch design. It looks like the nozzle got some damage, but I think it looks like it might be salvageable. Looking forward to seeing that video. Magnus has also recently started a rocketry forum.