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Big engine, chain hoist, attitude engine plate, cabin hatch

May 7 and 11, 2002 Meeting Notes


In attendance:


John Carmack

Phil Eaton

Russ Blink

Neil Milburn

Joseph LaGrave (Saturday)



We expected to do more high speed rotor testing, but the new tubing didn’t make it on time. We did get another large solenoid, and Russ has made a new sensor circuit, so we are basically ready to go as soon as we can re-plumb the rotor. We also changed the tank mounting on the trailer so we can use it for both the horizontal test stand and the vertical test stand without having to move it.


Big engine


The two 5.5” ID stainless engines from DynaTurn made it in, and they turned out great. I originally intended to make a copper sheet gasket for it, but we went ahead and tried it without a gasket, and it seemed to seal fine just on its 20 bolts.


It turns out that we got perfect engine performance with only 60 silver screens in this engine, while we needed 70 in the 1” ID engines, so there seems to be some beneficial scaling factors as work.


On Tuesday, we made several very smooth test firings, but the performance was off a bit from what we expected. The throat was fabricated fairly sharp coming from the 45 degree converging angle to the 15 degree diverging angle, so Russ took it home and rounded it off a bit. This did increase the throat area a bit, but our tests on Saturday showed both more thrust, and higher Isp. In fact, the 122 Isp we measured is the highest we have seen from any of our engines. We also had a kinked hose on Tuesday, so we can’t for certain attribute the large performance boost to the smoothed throat, but it is probably a good bet.







Chain Hoist Balance Test


We finally got around to hanging up Russ’s chain hoist, se we can lift the vehicles from a single point to properly balance them.



Attitude engine plate


The 2’ diameter vehicle will have offset side firing engines, unlike all of our vehicles so far, which have had canted down firing engines. We are using 1.25” tubing clamps to mount the engines, and we were just barely able to rigidly connect pairs of solenoids together with a T fitting, so we will only need to run two hard lines on the bulkhead. We had to remove the outer solenoid casings and grind a little off the retaining bolt, but it was worth it for the compact plumbing arrangement.


The mounting bulkhead is just 3/8” playwood, but we sealed it with epoxy to make it peroxide safe. The picture just shows them laid up on the press board that stiffened the filament wound tubing for shipping, not our real bulkhead.





Cabin Hatch


We fitted internal retaining slides to the 2’ tube for our lexan hatch. We had been planning on making the hatch slide into a pocket on the bottom, and have a dog on the top, but it turned out to be easy to just make sides on the top and bottom, and slide the lexan to the side for getting in and out. We are just going to put two bolts through the lexan on the side, with a strap between them on both the inside and outside. The bolts will also serve as slide stops. This is not intended to be a pressure tight cabin, just an aerodynamic fairing.


We should have left it alone after we had it all set up, but we tried to heat form the lexan sheet so it wasn’t sprung so tightly into the tube. A heat gun didn’t get it hot enough to soften sufficiently, so we went after it with a torch for a while. We got it curved a bit, but when we tried to straighten out the edges a bit, we wound up making bit of a mess of it. We are probably going to have the plastics company that made our test stand shield curve another piece for us.



Upcoming Work


Full speed rotor testing

Replace tubing

Water flow the large solenoid for comparison

Test new tach sensor

Attitude bulkhead testing

Finish mounting and tube bending

Mount in tube

Mount top bulkhead with eye bolt in place of rotor hub

Make an eight conductor CPC extension cable

Have Joseph bring his Bobcat to suspend it outside


Big lander flights

Replace Ethernet board in flight computer

Finish new software architecture

Make new mounting bracket for main engine


Precession attitude control tests

Add rotor RPM control to flight computer

Get more chain for tying down all four corners of the lander at the pad


Bore out one of the 1” engine nozzles from 0.33 to 0.45 to see if we can use a larger throat to pack ratio


2” ID engines will be in next week

Regeneratively cooled chamber with integral fuel injector

Tap ¼” NPT into the bottom of the spare NOS tank so we can run higher pressure kerosene

Radiatiively cooled chamber

Fuel injector ring

Clamp ring for non-bolted chamber

Fabricate brass mockup and test with flood cooling

Get TZM to DynaTurn

Platinum plate at Dallas Precious Metals


12” ID engine

Pay for silver screens

Find someone to roll the nozzle

Weld everything together and cleanup

Fabricate reinforced perforated metal retaining plate


High speed flight

Fabricate a sheet metal nose cone / rotor spinner

Test new parachute rocket system



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