15G works!

15G worked successfully until the paraffin regressed to its maximum diameter and flamed out. While the grain's core was initially 3/8", its very likely that attempts A-F made it regress slightly. This resulted in 1.7seconds of sustained combustion for 15G.

Tests #13h-j unsuccessful

Refilled the nitrous tank, and used the new DAQ controller functionality.

• Test 'H' failed since the DAQ's flow and ignition lines were wired backwards
• Test 'I' used a 0.25s delay between burn and flow. Did not catch.
• Test 'J' used a 0.5s delay, the augmentation certainly lit but paraffin did not catch.

We think there may be some issues regarding driving the igniter, solenoid, and lamps all off of a single 12v 4.5Ah battery. Despite it being recharged immediately prior to this round of testing. As a preventative measure, it has been decided to split everything into at least two, possibly three batteries. We have four in total, complements of the old WARRIORS I 50v capacitor charging system known as 'Sparky'.

Its likely these igniters are not working well; time to order some 30AWG nichrome and build a new batch - with plenty of spares for just igniter testing so we can build up some confidence. We might need more pyrogen too.

Transistor board & DAQ controlling

The DAQ's digital outputs, being driven by Nick's LabView program, are now providing the timing for the motor. This means the Linux-based laptop and serial port arrangement is obsolete.

Since the outputs are very much current limited, a transistor board was assembled. A NPN, setup as a NOT gate is chained to a PNP setup as a switch. This provides a common ground, separated positive voltage needed to go into the launch controller. This setup also drives some LEDs on the board. Pictures and schematic to follow, but its based off of http://www.kpsec.freeuk.com/trancirc.htm

Test #13 - Computer Control

Computer Control Problem
The computer control malfunction is more unfortunate, and actually has nothing to do with the computer. Originally it was thought the code was somehow malfunctioning, and despite nothing being found it is currently in a state of rework to add additional functionality. This included burn durations that are not integer values (2.5seconds, for example).

I took the opportnity earlier in the week to completely rewire the controller. It was an awful mess of wiring which made it impossible to debug. It also used a lot of high gauge solid conductor wiring, which is rather fragile and easy to break. In fact, the manual ignition firing button was having an intermittent problem likely attributed to a break in the wiring.

So, it was time to gut the controller and rewire it with lower gauge stranded, and minimize all the back-and-forth between the terminal strip and the console buttons by wiring the console buttons up directly to each other. Electrically speaking it would be identical to the old configuration.

Or that was the plan. While everything is working on manual control, the computer control is experiencing some faults. One problem is that when the flow is armed, but ignition is not, the flow is engaged. The second problem is that when the computer is commanding both to engage, as it should be during the ignition/flow startup sequence, neither event is actually on. This results in a very short ignition event, a pause, and then a flow event. This clearly wouldn't result in a good start. The exact circuit error has not been uncovered yet, but will clearly have to be resolved before the next test attempts, currently slated for Wednesday of next week.

Manual control
So the first three attempts were done with a faulty automatic sequence, and the last four were done under manual control. This was rather reminiscent of the tests last summer, when there was no computer control. As such, attempt 'D' was ignition, and then flow as soon as combustion was seen. Failing that, attempt 'E' was simultaneous flow and ignition. Attempt 'F', done this morning, was preflow, and it literally blew the igniter out of the motor. Attempt 'G' was another preflow attempt, with the igniter held secure with some tape.

Test #13 - Nitrous issues

Nitrous Oxide Problem
We've been running low on our nitrous tank for some time, and while we're still getting a line pressure of ~760psi its likely whatever liquid that's left in the tank is bellow the tank's stem. So only gas ends up in the line, causing the motor to deflagrate instead of getting a good burn.

So we need to refill the tank. We just had a very large tank of nitrous delivered; however the tank is gaseous only (it doesn't have a stem). Even if you set that aside, the transfer of nitrous from one tank to another is rather complicated and requires equipment we don't have, nor have the budget (or time) to invest in.

So the large nitrous tank is useless. Our small tank will have to be brought to the auto-racing store to be refilled.

Unlucky Test #13!

Over the past two days there have been 7 unsuccessful attempts for Test #13. Is the number cursed? Our experience seems to indicate that it indeed may be! This is our first test of an entirely new 10lbf paraffin motor.


We've uncovered two major problems:

• Only getting gaseous nitrous oxide; no liquid
• Computer control malfunction

There's so much here that those two major problems are going to get their own entries. For now, here's some of our secondary issues:

Igniters:
We are out of igniters, and don't have all the supplies (namely nichrome) to make new ones. Our pyrogen is also running low. Thankfully the guy that made the igniters for WARRIORS II is still around, and is willing to make us a new batch when we have everything.

Paraffin:
This batch of paraffin didn't have any specifications associated with it as it is sold for arts&crafts purposes. We already have a large quantity of high-grade paraffin ordered and are just waiting for it to arrive.

Core diameter:
Our current grains have a 1/2 inch diameter bore. To speed up the nitrous velocity, we would need to reduce that to around 0.33 - 0.38 inches. To slow down the nitrous velocity, we would have to increase it, probably in the 0.6-0.7 range. Would changing it improve the motor's ability to ignite, and at what penalty to overall thrust?

Grain augmentation:

• Is it needed? (can the igniter do it on its own)
  
• Where should it be applied? (core, mixing chamber)
  
• What should it be? (kno3, standard AP solid composite, pyrogen, sorbitol/potassium nitrate, etc)

Additives:
Right now all our tests have been done with 2% (by mass) of lamp black / charcoal. This slightly suppresses the combustion. Should our tests next week still use this, straight paraffin, or have an accelerant added?

Timing:
Right now we have no idea what the best ignition sequence is for paraffin. The three options are:

1. ignition/delay/flow
2. simultaneous ignition & flow
3. preflow prior to ignition

Data Acquisition
On the plus side, the LabView interface is working great now. No buffer overruns, data can be displayed in realtime with high refresh rate, not all data has to be stored to the hard drive, etc. Its really slick now, and getting to the point where it may replace the linux laptop & perl script for the actual motor control. No, the outputs from the controller for event recording hasn't been completed yet -- I've been kinda busy with higher priorities.

We certainly have our work cut out for us!