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
Added detail drawings for the regen chamber.
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 :)
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.
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
Once I organize my design notes for the regen engine, I'll post
them here. The thermal analysis results are interesting to look
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
Got my LOX-compatible lube in the mail the other day. Tribolube-16 from
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.
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.
The loss of the Space Shuttle Columbia - a very depressing event
for those interested in space or rocketry.
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
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.