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Vehicle work, Regen lox engine

October 25, 2004 notes:

October 25, 2004 notes:

 

I was traveling on Sunday, and had trouble finding the time to do the update…

 

The X-Prize forum moved a little while ago, the new location is at:

 

http://www.xprizenews.org/forum

 

I still check the “Official Armadillo Q&A Thread” regularly, and this is the place to ask any questions that may have general interest, rather than sending me email.

 

Vehicle Work

 

All the fabrication for the base is done, but we ran out of argon before some of the final welds were completed.

 

The base with the engine and shocks is 293 pounds, and the manway with all the plumbing is 67 pounds, for a total of 360 pounds.  We probably threw away all our weight savings by making the landing gear framework out of stainless instead of aluminum, but it is much sturdier.

 

http://media.armadilloaerospace.com/2004_10_25/finalBase.jpg

http://media.armadilloaerospace.com/2004_10_25/finalBaseBottom.jpg

 

We are milling pocketed backing boards for the new electronics boards, so they will be supported extremely well.

 

http://media.armadilloaerospace.com/2004_10_25/backingBoard.jpg

 

Regen Lox Engine

 

The new cooled chamber is back from the hardcoating shop, and we did several runs with it, including our first fuel cooled run.

 

http://media.armadilloaerospace.com/2004_10_25/hardcoatedChamber.jpg

http://media.armadilloaerospace.com/2004_10_25/waterCooled.jpg

 

We did some long run tests on various lox vaporizer coils, and learned some interesting things.  All tests were with an NOS pro race solenoid with a 0.11” (about) orifice.  The little coil we had would flow gox for twenty seconds or so, but after that it would be all frosted over and lox would be coming out.  We went to a longer 10’ coil of 3/16” OD aluminum tubing wrapped around a 2” aluminum pipe.  This ran longer, but still eventually failed to vaporize.  We went to total overkill with 40’ of 3/16” tubing, and it ran for several minutes, but the frost slowly crept up the tube, and even this eventually started spitting lox.  The flow rate was also way down from frictional losses.

 

http://media.armadilloaerospace.com/2004_10_25/vaporizerTest.jpg

 

It is arguable that we may not care if lox reaches the preburner after it has been running a long time, because it should still burn fine, just at a leaner ratio.  However, we decided to try to keep it vaporized by wrapping 10’ of tubing around the chamber (outside the cooling jacket) and using a metal filled epoxy to give it good heat transfer to the chamber.  Even with just the vaporizer running, the chamber gets quite a bit of heat thrown into it, so it will never cool down to lox temperatures.  This seems to work fine.  We will probably make an external channel wall jacket for this at some point in the future.

 

http://media.armadilloaerospace.com/2004_10_25/epoxyCoil.jpg

 

We got a brand new methanol preburner fully operational, so we now don’t need any consumables other than the main propellants.  We used a normal spark plug instead of our concentric tube arrangement, and we used a tiny Bete spray nozzle directly on the bottom of a solenoid to minimize trapped volume.  We had to go all the way down to a 0.018 jet on the methanol to keep the preburner from getting too hot with methanol pressure at 400 psi and lox pressure at 300 psi.  One of these solenoids can flow enough methanol to vaporize lox for a 10,000 lbf engine.

 

http://media.armadilloaerospace.com/2004_10_25/preburner1.jpg

http://media.armadilloaerospace.com/2004_10_25/preburner2.jpg

http://media.armadilloaerospace.com/2004_10_25/preburner3.jpg

http://media.armadilloaerospace.com/2004_10_25/preburner4.jpg

 

We got the lox turbine flowmeter working by drawing a vacuum on the lox plumbing to pull out all the atmospheric moisture.  It has been working fine ever since.  At 300 psi, saturated lox is at 134k and 0.87 g/cc density, while methanol is 0.79 g/cc density.  We want to run somewhere between 1.25 : 1 and 1 : 1 O : F by mass, so we basically want to flow roughly equal volume of lox and methanol.

 

 

 





 






 
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