Monday, December 8, 2008

How Much Inhibitor?


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.

Monday, November 24, 2008

LR-101 Combustion Chamber

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!

Tuesday, November 18, 2008

More machining for Sugar Shot to Space project

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.

Sunday, October 19, 2008

MiniSShot Motor Parts

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

Monday, October 6, 2008

Cutting Metal

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.

Monday, September 22, 2008

The Largest Solid Rocket Motors Ever Flown

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!

Tuesday, August 12, 2008

United Technologies Center Rocket Motor

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.

Tuesday, August 5, 2008

Successful Launch!

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.

Wednesday, July 2, 2008

Static Test Results

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.

Friday, June 20, 2008

Interesting Rocket Motor

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

Tuesday, April 29, 2008

USC Rocket Launch

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.


Monday, April 28, 2008

Weekend Rocket Activities

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.

Wednesday, April 23, 2008

Blog maintenence/missing photos

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.

Saturday, March 1, 2008

Photos from November

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.

Monday, February 25, 2008

Harvesting Aluminum Flake From Paint?

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.

Tuesday, February 19, 2008

Amateur Icelandic Rocketry (AIR)

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.

Saturday, January 19, 2008

Old Launch Photos and Stuff

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.

Tuesday, January 1, 2008

Camera Rocket Recovery Photos

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.