2003-12-11

Finished the Failsafe Control Unit which will be used to control the various remote devices (relays, solenoids, ignitor, etc.) during the test. See the Test stand section for more details.

I'm back to my original plan for testing just the uncooled chamber first. I figure I can learn a whole bunch by doing a series of short runs with the uncooled version in heat sink mode. Then, once I get that figured out, I'll resume work on the regen version.

2003-09-13

Added detail drawings for the regen chamber.

2003-08-29

Finished the solid model for the injector. See the Regen Chamber section. Next is creating detail drawings. Things have finally wound down somewhat at work so hopefully I'll have more time for rocket fun :)

2003-08-02

The parameters are done for the regen engine - see the design equation link below. I'm almost done with the detail design of the combustion chamber. I haven't started on the injector yet but I have an idea of what I want to do. See more details in the Regen Chamber section.

2003-06-21

Update of the web site - you can find the same material in the links located at the top of the page.

I decided that it's going to be too much effort to put everything together just for a 5-second test with the uncooled engine. So, I've started on the regen version of the engine. I'll still test the uncooled engine first in case something goes wrong so I hopefully won't lose both engines. In any event, most of the work is in the design - I fabricated the uncooled engine in two consecutive weekends after months of planning and gathering tooling, etc. It also doesn't help that my design/build time is comparatively cheaper than purchasing more equipment for the test. This combined with the work schedule at my real job has pushed out the test until at least the fall of 2003. So, I figure it's worth the effort to get started on the regen engine. I'm always open to generous donors who want to see a cool project happen!!!

If you have OpenOffice or StarOffice, you can view the design spreadsheet I've been using. OpenOffice is an excellent, free substitute to Microsoft Office.

I've come across some great references in the past few months. One of them is NASA SP-125, Design of Liquid Propellant Rocket Engines. You can find a copy on Sourceforge here. I've refined many of my design equations based on the information in SP-125.

Once I organize my design notes for the regen engine, I'll post them here. The thermal analysis results are interesting to look at.

2003-03-08

Ran the first cold water tests today with the new test stand. Things basically worked but there are few operational issues that need attention. The power supply for the solenoids kicks in its overvoltage protection sometimes and turns itself off. Also, I need some more work on the test acquisition and control software. I'm using multiple LabVIEW loops and I think I may have some race conditions.

Got my LOX-compatible lube in the mail the other day. Tribolube-16 from Aerospace Lubricants Inc. is quite a bit cheaper than Krytox ($23 vs. ~$60 for a 2 oz. tube). According to NASA LAPG 1740.5 (Procedures for Cleaning of Systems and Equipment for Oxygen Service), the compatible lubricants for oxygen service are Krytox 143AC, Krytox 240AC, Tribolube F195, and Tribolube 16.

2003-02-15

I finished the load cell bracket so the engine is finally attached to the test stand. The only problem is that I'm using 3/8 inch copper tubing to connect the engine to the propellant valves and the tubing is sufficiently stiff that it may affect the load cell readings. Ideally, I'd use flexible metal hose to connect things up but a 3/8 inch hose rated for cryo service is about $100. So, I'll do some tests with the load cell to see if a significant portion of the load is carried by the tubing. The load cell is much stiffer than the tubing so maybe it won't be a problem.

I need some check valves to prevent cross-feed of propellant tank gases and then I'll be ready to do some water/LN2 tests.

2003-02-01

The loss of the Space Shuttle Columbia - a very depressing event for those interested in space or rocketry.

2003-01-06

I've had good luck with some homemade burst disks. I got the idea from this link I found on the Danish Amateur Rocketry Club web site.

I modified the propellant tank fittings to also serve as burst disk holders. I tried brass shim stock from the local hobby store as well as some 1145-0 aluminum sheet samples from Alufoil Products. Here are the test results.

For a 3/8 inch hole, the appropriate thickness for the 1145-0 aluminum seems to be about 0.005 inches and the thickness for the brass seems to be 0.002-0.003 inches. I'm not sure which I prefer - the aluminum sheets seem to be better controlled and have guaranteed materials properties. The thicker aluminum (0.005) sheet will tend to resist mishandling better than the much thinner brass (0.002) sheet. Both materials are probably fine for LOX service, although I don't know the exact material properties of the brass sheet.