Hermes Solid Rocket Motor

I bought number of Thiokol publicity/advertising brochures on ebay a while ago. There are a lot of interesting photos including the one above that shows Harold W. Richey posing with the "milestone" Hermes rocket motor which was fired in December of 1951. In that firing the motor fired for 41.2 seconds and produced 17,172 lbs of thrust. Fourteen months later it went on to successfully power the RV-A-10 rocket from Cape Canaveral. The Hermes is credited with validating the concept of large solid fuel motors. There is also a series of photos that show the process of prepping and loading the shuttle SRM's that I'll post later.

SStS Test Parts Finished

I finished the test parts that I was working on and Rick picked them up yesterday afternoon.  He and Paul were going attempt the first test this weekend.  I was scrambling to get the parts done in time for this weekend, the steel bulkhead took a bit more time than anticipated, but hopefully the parts serve their purpose well. 
Here I'm tapping the steel bulkhead:

I was starting the tap in the v-block on the drill press to get it started straight then laying it flat to get a good enough grip on it to turn the tap.  The whole process of tapping the bulkheads took longer than I was expecting, but when you're tapping or threading it's definitely best not to rush.

Here are the finished parts:

TR-1 Motor

I haven't had a chance to do much work on the TR-1 motor...I'm satisfied with the design and am ready to start machining.  I just need to finish machining the hardware that I mentioned in my previous post.

I modeled the nozzle in 3D.  I find that this helps with the machining if I can move the part around and think how best to machine it.

 The design is similar to the MiniSShot nozzles that I machined in that it consists of two main pieces.  There were a number of reasons that we chose to construct the MiniSShot nozzle in two sections, but for the TR-1 motor the decision was made simply to ease fabrication.  Constructing the nozzle from two pieces allows me to use some stock that I had on hand and more importantly significantly reduces the amount of material that I'll need to remove.  I have a piece of 1018 for the shoulder portion of the nozzle and some 12L14 for the convergent/divergent  piece.

SStS Machining

I'm currently trying to finish up a test set-up for the SStS project that will allow us to test a single grain segment with the star core that we've used for the last two motor firings.  It's simply a short section of the casing material with two end closures, one made of Aluminum and the other of steel.   Looks roughly like this:

I used the new center drill indexing the steel bulkhead and the difference was immediately noticeable.  Don't use dull tools kids!  Anyway, after realizing what a difference it made I decided that i needed to stock up on the # 1 size center drills. I managed to find a set of four # 1 center drills on Ebay.  I paid about what I did for the set from Harbor Freight, so a great deal!

Here is a shot that shows the bulkhead after I indexed it.  You can see the Dremel set-up in the tool holder and the indexing holes on the main gear of the lathe.  You can also see the indexing pin in the casting between the back of the chuck and the gear.

Here are a couple of shots showing the machining progression on this piece.  This is the first time in a while that I've done something this larger using 1018 steel and it's definitely slower that using 12L14 steel. 

Harbor Freight

I'm starting to be able to make more time for rocketry and inevitably that means more machining.  In the past year or so most of the machining that I've done has consisted of indexing and drilling holes...a lot of indexing.  I use a Dremel rotary tool  in the lathes tool holder to mark the hole locations in whatever stock that I'm indexing.  The Dremel takes a 1/8" bit which corresponds to a #1 center drill.  I have a bunch of center drills but only one of them was a #1 so it borne the brunt of the abuse over the course of this last year indexing well over 300 hole locations.  I've noticed the last couple of times that I used this set-up that the bit was getting dull and last weekend indexing with it I felt that the accuracy was be compromised.  I figured that I would order a bunch of #1 bits from McMaster-Carr, but they were $14 a piece, fortunately Harbor Freight carried a set for $7.  Don't get me wrong, McMaster-Carr is great, they have almost anything you could ever need, some things you don't know that you need yet, the site functions well and is full of useful info, customer service and shipping are great, but a similar set (theirs has 6 bits vs 5) cost over $200.  I opted for Harbor Freight, but it took a few visits before I found them in stock.  I've actually been spending a lot of time  restocking, cleaning, and organizing... tools, batteries, bits, etc.

Space X

Congratulations to Space X.  Everything seems set for them to complete this historic journey to becoming the first commercial company to dock to the International Space Station.  Best of luck in the coming days.

Metal Purchase

I picked up some metal from Industrial Metal Supply before work yesterday. I got some 7" diameter 6061 and 1018 for a test motor I'm building for SStS and some 5" diameter stock for the TR-1 motor.