August 14, 2001 Meeting Notes

 

In attendance:

 

John Carmack

Phil Eaton

Russ Blink

 

Phil and I picked up another four gallons of peroxide from Rinchem today. We are going to have to start filling two jugs at a time, now that we are firing the bigger motors more often, because we used half of it just tonight. We will probably wind up taking an entire drum out to the test range and storing it in a shed when we move big firing operations out there.

 

Russ finished all the lathe work on the main engine, so it just needs a bunch of drilling and tapping on the flanges. With full flow, this should produce well in excess of 600 pounds thrust. We will probably fire it at Long Range briefly with a small solenoid and plumbing that will prevent it from making more than 150 pounds or so, and do some full flow water tests to check the spreading sheet and retaining plate retention before firing it full on out at the range.

 

media.armadilloaerospace.com/2001_08_14/BigEngineOnLander.jpg

media.armadilloaerospace.com/2001_08_14/BigEngineAtCorner.jpg

media.armadilloaerospace.com/2001_08_14/EngineLineup.jpg

 

I have changed our test stand electronics over to new equipment that we will be able to run strictly from DC power, but the dataq DI-195B that I am using is responding slightly differently than the DI-151RS that I had been using before, giving me jumpy data. I know it is a software issue, because when I use their bundled software, it is steady. We can still use it for basic measurements, but not smoothness tests until I fix this. Worst case, I can use their active-X control, but I hope to figure out the raw serial line protocol properly.

 

The electronics box is now converted over to a single large connector for all the attitude engines, so we can never again plug two of them in backwards. We converted both the small and large landers to the new plug type, and mounted a new four engine manual control box on the fill cart that can directly replace the electronics box. This is a big improvement in several convenient ways.

 

We made several improvements to the fill cart today. We increased the tank hose from –4 to –6, which reduced the vacuum loading time for a liter of peroxide from 60 seconds to 37 seconds. We put on a bigger vacuum pump that Phil rigged up a set of check valves for, and it works significantly faster. We added a check valve in front of the nitrogen solenoid so we can change nitrogen tanks in the middle of a pressurization if necessary, and we increase the size of the nitrogen line and solenoid to make pressurization faster.

 

We are going to put in an application for an FAA waiver at our test range soon. We will just go out and fly some HPR vehicles the first time, getting us used to the launch and recovery process there before putting up one of our peroxide vehicles.

 

We weighed several components today:

 

The electronics box, which is exactly the same on both vehicles, weighs 13.2 pounds.

 

The big vehicle in short form weighs 120 pounds without the electronics box or propellant.

 

The small vehicle weighs 29 pounds without the electronics box.

 

So, in minimal fueled (one liter / four liters) hop form, the small vehicle weighs 45 pounds and the big one weighs 148 pounds. The engines are almost exactly the same in relative thrust – we didn’t test the small ones after drilling out the nozzles, but they should be around 20 pounds, and the big engines should be slightly less than the 65 pounds we see on the test stand due to longer hoses.

 

The big lifting engine weighs 16 pounds, and there will probably be another 14 pounds of valves, joysticks, and manifolds before the manned vehicle is completed, giving a minimum weight of 165 pounds + pilot + propellant. We can reasonably load about fifty pounds of propellant, so we would be looking at a total liftoff weight of up to 400 pounds. The extra outrigging and braces for the long form of the vehicle adds another fifty pounds or so of metal. Depending on the propellant load and pilot weight, it should be able to fly for ten to fifteen seconds.

 

In HPR terms, our central engine and tank make an O-3000 motor (around 25,000 NS of thrust)

 

Big Frame Hops

 

We sort of broke best scientific protocol and added more catalyst to each engine today without retesting. We still suspect that our cloudy runs on Saturday were at least partially due to the 100+% humidity and cooler temperatures, but we just went ahead and filled the engines without retesting. We now have 21 discs in each engine, compressed very slightly, with no spacer at the bottom. All the exhausts were clear today.

 

We loaded up four liters of peroxide, which should give around five seconds of flight on the big vehicle. We pressurized to a little over 500 psi, which took over half of our new, larger nitrogen tank. We need to move up to the largest size nitrogen bottles we can get.

 

The first test was with a 20 hz pulse rate, instead of the 30 hz rate we usually use on the

 

We didn’t have a cameraman today, so the video isn’t all that good, with the lander getting almost out of the frame:

 

http://media.armadilloaerospace.com/misc/BigFrameLiftoff.mpg

 

It had an obvious tilt towards the offset CG due to the electronics box (which will be worse when the pilot is there), and it was very jerky. A first look at the telemetry graphs showed that it was rapidly making large overcorrecting rate oscillations.

 

We made another hop with the pulse rate set to 30 hz (we just barely were able to lift off with the 380 psi we could get in the tank), but it was significantly worse, and it tipped over almost immediately.

 

I still have a lot of analysis to do on the data, but there are clear differences in the behavior of the big and small vehicles. The big one probably has quite a bit more control authority, because the small one has mass (the landing pads) much farther away from the centerline. The valves and plumbing are also different enough that the relative pulse behavior may be different.

 

We will try again on Saturday with software changes.