Wednesday, March 23, 2011


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.

Tuesday, March 22, 2011

Update (Sidewinder Nozzle Comparison)

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...

Monday, March 14, 2011

Motor Update

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:

Wednesday, March 9, 2011

More Nozzle Machining...

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.

Monday, March 7, 2011

More Nozzle Machining

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.

Wednesday, March 2, 2011

New Motor Nozzle

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...

Tuesday, March 1, 2011

New Rocket Motor

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...