Going Up!

Bench and Flight Computers are Provisioned

John — Sun, 25 May 2008 03:50:39 +0000

Getting Linux From Scratch on the bench computer took a lot longer than I thought it would, but it’s done. I now have the bench computer running from a 80GB laptop hard drive and the flight computer runs off a 2GB compact flash with a minimal installation.

The next phase will be to write kernel drivers to support the IO cards in the stack, beginning with the digital and analog IO boards. We should be able to control actuators from the bench pretty soon.

Provisioning the Flight Computers, Chemistry Time

John — Sat, 26 Apr 2008 15:36:27 +0000

Although I began ordering equipment as early as January, and the vendors, Acces I/O and Connect Tech have been spectacularly fast and helpful, it is only now in late April that I have been able to sit down with equipment and begin serious work. The computer, an MSM800SEL from Digital Logic, is based on the AMD Geode processor and the PC-104 stack will run a stripped-down version of Linux based on the “Linux From Scratch” website. I am currently building an installation on a virtual machine running on my MacBook. The flight computers are over-engineered for the task at-hand, but they both double as bench and/or field computers in a pinch, plus they should have the computational power to capture streaming MPEG-4 video. Future dedicated flight computers will probably be embedded depending on their work load.

Looking at the I/O boards, we’ll have direct access to the analog inputs and outputs; however, it will be necessary to write a custom kernel driver to get the level of control that I need, which all-in-all, I prefer anyway. No transducers have been purchased yet, but I’ve got some basic items laying around the bench including an accelerometer, a thermistor, and some potentiometers for testing.

Additionally, we’ve secured a small quantity of peroxide for our next round of experiments. I will be looking at making a hot-gas generator this weekend, the purpose of which is to determine the optimal ratios of peroxide to catalyst to create oxygen gas. This gas will ultimately be fed into the combustion chamber, but may also drive a pneumatic system or turbo pump. Meanwhile, it will also be helpful for experiments with the reaction control thrusters on the lunar lander project.

Finally, we have several catalyst pack designs that need vetting. Our current darling involves Durham’s Rock-Hard Water Putty and Potassium Permanganate. It creates an ablative coating with a very high surface area that can also be machined into any shape necessary. I’ve been thinking of making a sponge-like structure out of it with extremely small, but open cells for a gas-generator or pre-burner stage. Could be fun.

Also, my machine shop practice is going along. I’ve been working with Lathework: A Complete Course, but I’m finding that it’s not very good for complete novices such as myself. I’ve ordered Lathe Operation and Maintenance which seems to have better reviews.

Rocket Equations, Throbbing Brain

John — Tue, 18 Dec 2007 20:17:13 +0000

I picked up two books from Amazon for rocket engine design work. Although the preliminary chapters were very simple, it took a lot longer to wrap my mind around the more elaborate equations. It’s been awhile since I did calculus on a daily basis and my brain’s just not in the habit of doing that type of abstraction. For what it’s worth though, the big take away point is that I will need to do considerably more work in the lab than pounding through equations. My short-term goal is to build a simple cold-gas engine and, using some custom made measuring equipment, calculate its performance. This will give me a better sense of what I will need as I scale up to monoprop and finally biprop.

Space Propulsion Analysis and Design

Rocket Propulsion Elements, 7th Edition

Making the Cut

John — Mon, 17 Dec 2007 20:37:25 +0000

I’ve started learning how to use the lathe. In addition to getting the faces of the metal absolutely perfectly square, I’ve managed to remove about 20mm from the radius of a 100mm stainless steel cylinder, 0.2mm at a time. Good practice, but somewhat time consuming. Ultimately, I want to cut out a rocket nozzle, but that’ll take some engineering, and I don’t know how to do it yet. At minimum, I’m going to need a boring bar.

Also, I’m learning how to make very accurate measurements, but I still need the proper tools. Hopefully, after Christmas, I can pick some up. I’ve been informed that Santa has some metalworking goodies for me, so I’m waiting patiently. In the meantime, I bought some calipers so I can transfer measurements. My goal is to cut two pieces of metal to the same diameter, at least to within .02mm.

Meanwhile, I put in an order to OnlineMetals.com and they are sending me metal to play with. Apparently, I can also get “cut-offs” from a place in Phoenix super-cheap, so I’ll definitely want to check that out next time I’m up.

First Chip

John — Sun, 16 Dec 2007 20:53:49 +0000

After getting the lathe/milling machine unpacked, we cut some chips. Here we’re milling aluminum with a Granite 1324.