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Dec 19, 2000 meeting notes

Dec 19 meeting notes:

Location: Norwood Autocraft

In attendance:

John Carmack
Phil Eaton
Russ Blink
Bob Norwood

Next meeting delayed until next Thursday due to the holidays.  If we have peroxide, it will be at Long Range, otherwise it will be at Norwood’s. We missed the last two weeks due to an ice storm and various holiday issues.

Our peroxide status is getting troublesome.  We ordered 10 liters of 90% from X-L Space Systems on November 6
th, and were eventually given a ship date of Dec 15.  Dec 15 came and went, so I left an inquiry with X-L.  I got an email today saying that they had decided to concentrate on 98% and would be refunding my money.  I have asked that we just be sent 98%, but I don’t have confirmation yet.

We can dilute 98% ourselves, but if X-L doesn’t work out as a supplier we are back to meeting all of FMC’s requirements or distilling and purifying ourselves.  I am still looking for a permanent building for us that could satisfy FMC, but I haven’t found anything of a reasonable size for us yet.

I am all incorporated now for our rocketry work  Armadillo Aerospace is a Texas LLC.

The remaining load cells came in, so we now have 100lb, 500lb, and 3000lb load cells.  We need to wire up some connectors for these, because they are designed to have the leads screw directly onto the meter.

The extra fittings came in.

I got enough hi-temp spray paint for the test stand.

I got a selection of vinyl and polyethylene tubing for us to use, because we always seem to need another piece or two.  Russ: I think we need some more dual line stoppers and bottles for vacuum catch / peroxide transfer.

Neil is building the dumb rocket.  We should be able to launch it on a HPR motor at Shoot For The Stars @ Windom in three weeks.

Phil / Neil: Pick out the launch equipment we want so I can get it ordered.  I want to err on the side of an extra long and stiff rail, since we may be a bit light on thrust to weight.

Phil: We need to get the MacGreggor information to the insurance agency for our private peroxide launches, and we need to finish the FAA waiver.
I have done a lot of telemetry tests recently.  The information is summarized at
media.armadilloaerospace.com/misc/telemetry.htm.  The final radio modem came in, so I can now set up a full duplex raw telemetry connection, although I need to buy another full duplex dual band radio.  Phil is going to build me a PC board to replace my hand wired DB9 to dual DB25 full duplex adapter.

I have built up a pretty nice software framework four journaling and sequencing multiple data sources that is good for both flight computers and ground stations, and I am integrating my GPS visualization app into a general ground station app.  I am probably going to buy a PC104 development system for the flight computer, but I am still a bit tempted to try using a WinCE palmtop with either a USB or PC Card four-port serial adapter.

Darin is getting data from the accelerometer through a basic stamp now.  We should pick up one of the 3-axis units soon.

Darin is getting a list of the dimensions that his friend at the laser drilling shop can produce.  I picked up some 1oz silver coins that we might turn down and use as injector plates.  If we can get a lot of truly fine perforations, there is a possibility of replacing the catalyst pack with several injector plates.

When we get the next batch of foam plated, we need to get the exact process specs that the plating shop uses.

The magnetometer is still supposed to be here Real Soon Now.

I recently did some thinking about other attitude options, and I actually think that we could get away with using an inclinometer for pitch and roll control.  Our platform can’t generate any side thrust, and won’t be doing any rapid angle changes, so I think an electrolyte-based inclinometer might be workable.  We might be able to just strap a sidewinder freestyle joystick on it…

Russ / Phil: lets lay out some flight battery options next time, and see how quickly running the solenoids draws them down.

We picked up a couple big fuel injectors from Bob today.  The largest injectors you can get are only 170 lb/hr, and only operate up to around 200psi, which is only about 5 lb of monopropellant thrust.  That isn’t going to be enough for even our small VTVL engines, but they could be useful for dedicated attitude control thrusters on other vehicles.  The integrated solenoid and good spray atomization would be nice benefits.

Interestingly, it turns out that we are going to be able to do yaw control as well as pitch and roll with only four engines.  Arrange the engines slightly canted so that the north engine points slightly west, the south engine points slightly east, the east engine points slightly south, and the west engine points slightly north.  If there is equal thrust on all engines, no yaw acceleration is produced.  If the north and south engines are throttled down, there will be a counter clockwise torque.  If the east and west engines are throttled down, there will be a clockwise torque.

There is a cross coupling between yaw and roll or pitch, where pitching or rolling will also induce a yaw, but it can, at least in theory, be canceled out automatically.  I will modify the simulator to experiment with this and determine what degree of cant is needed.

We finalized the VTVL platform structure tonight, and Bob is ordering the necessary tubing to build it.  It isn’t going to look all very elegant, but it should give the bottle and engines good protection and not weigh much.

We probably have another month of structure, electronics, and coding work to do, but we are already pinched a bit by the lack of peroxide, and we are going to be hard gated on it if we don’t get something worked out soon.


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