Feb 27, March 5, and March 9, 2002 Meeting Notes

 

I had to be out of town last Saturday, so we missed a session…

 

Flight clearance

 

A big piece of news is that it looks like we have clearance to fly our unconventional vehicles in Oklahoma.  We have had two waiver requests denied here in Texas, but for the last several months I have been working with the Oklahoma Space Industry Development Authority (OSIDA) http://www.okspaceport.state.ok.us/ to try to secure facilities for our future testing. 

 

Our particular vehicles are especially problematic, because they don’t fit any of the common FAA categories.  Apparently, FAA Flight Standards in Oklahoma has decided not to regulate our vehicles, passing authority to air traffic control.  The tower at the Clinton-Sherman base where most of the OSIDA activity will be has complete control to 4500’, so we can arrange to fly our vehicles in any configuration we want, and just clear it with the local tower.

 

This is a Very Good Thing, as high altitude testing is obviously a critical path item.  4500’ isn’t much, but it will be all we need for the next six months or so, and with the precedent of clearing it with air traffic control set, we should be able to arrange higher altitude windows later on.  We will still have to go through AST in Washington when we want to go to space, but there is reasonable hope that altitudes as high as 100,000’ may be done with only regional oversight.  It won’t be important for quite a while, but Oklahoma does have large enough areas of low enough population densities for 100km flights, given AST clearance.

 

The OSIDA folks are making things happen Right Now.  They are actively working the FAA and EPA issues, and they have a number of incentives for companies that can relocate to Oklahoma.  Pioneer Rocketplane is their big shot, but they are also working with a number of other companies.  JP Aerospace is doing an educational high altitude balloon launch for OSIDA later this month.

 

I will be signing an official memorandum of understanding with OSIDA next week.

 

Mobile Test Trailer

 

When we first started, almost a year and a half ago, our little angle-iron test stand with a four liter tank strapped on was a good match for us.  In the ensuing time, we have had to add bigger tanks, bolt down holding points, a separate cart for all the filling equipment, a separate box for the electronics, and recently, externally regulated nitrogen, kerosene, and ethane tanks.  It has gotten to be a pain.

 

Since we also know that we will be doing some very large engine testing on the new vertical test stand out at the 100 acres, we have decided to get a good sized metal trailer that we can secure everything onto, including space for a drum of peroxide, drums of water, tools, etc.  We will leave the little horizontal test stand at the back of the trailer for engines under 1000 pounds of thrust or so, and we will be able to just pull it up beside the (soon to be sunk-in-concrete) vertical test stand for the larger motors and rotor tests.

 

This is going to make our setup time a lot quicker for our normal testing, and make it a lot easier for runs out at the 100 acres.  Joseph is going to make a cradle to hold the lander in his truck bed, and pull the trailer behind.

 

Other Stuff

 

We finally got a price quote from Ultramet http://www.ultramet.com/ for putting an iridium oxidation protection layer (with CVD) on top of a small (2.75” diameter by 6” long) chamber and nozzle that we would machine out of TZM.  They quoted $15,000 in tooling and $20,000 for the coating.  Err, no.

 

I have another vendor that is going to get me a price for some other coating options (silicides, etc), and worst case, we will try platinum electroplating.  In the end, it may be a moot point, because our cooled engines are coming along a lot better than I expected.

 

Haver Standard, the company that we ordered our pure silver screens from, is claiming that the domestic unrest in India is preventing them from shipping our order.  We can get screens from other places, but they are far and away the cheapest.

 

Rotor Blades

 

Our big rotor blades from http://www.vortechinternational.com/ arrived.  The full sized blades are 13’ long each, but we also got a scrap blade that we cut into two 6’ blades to do initial testing with.  We built all the parts and plumbing we needed for the hub, and got the short blades bonded on at 10 degrees pitch today.  We will be doing the final bolting and assembly on Tuesday.  After much arguing, we finally settled on a tip engine mounting scheme, which we will hopefully be able to test on Tuesday.  It will be a bit odd looking, but it should be quite secure.

 

The 12’ diameter rotor is pretty sizable.  The full sized rotor is going to be huge.  We will do some very low RPM tests to make sure the test stand and plumbing are functioning correctly, then move out to the 100 acres for spinning it up to higher RPM.  Sonic tip velocity would be around 1600 RPM, but we don’t plan on spinning it that fast.  If we can make over 500 pounds of lift at RPM we are comfortable with, we will probably mount the rotor on top of the current lander, so we can investigate how attitude engines behave with a coupled rotating mass, which I am rather unclear on at the moment.

 

We will make a new hub and engine mounts for the 27’ diameter rotor, which is intended for our next generation vehicle.

 

Because we are going to use hard line tubing for running the peroxide down the rotor blades, I have had to start buying some new classes of tools and fittings.  I bought a few Yor-Lok compression fittings, but Doug Jones of XCOR www.xcor.com (buy an EZ-Rocket poster!) gave me a bunch of pointers, and I am going to be moving to flare fittings, which interoperate with our other AN plumbing.  We will probably be using hard lines for other plumbing in the future, as it is a lot cheaper, lighter, and easier to make different sizes than braided stainless hose.

 

Feb 27 Engine Tests

 

We rebuilt a 1” diameter cat pack with some minor changes, and had four absolutely dead smooth runs.  We are still recycling the same screens, because we are still waiting for our new catalyst order.  These pure silver screens are closing in on 1000 seconds of firing time, with no sign of slowing down.

 

March 5 Engine Tests

 

We finally got around to measuring some chamber pressures today.  We replaced out fuel injector fitting with a 2’ long, 1/8” diameter stainless pipe leading to our transducer.  Many months ago, we had tried putting the transducer right on the engine, but it got too hot almost immediately, and started reading ridiculous chamber pressures.

 

run 1:

0.080 peroxide jet

250 psi ullage

We got a very strange pressure curve, starting out much higher than the ullage pressure, then decaying to around 80 psi.

 

run 2:

repeat

Same results.  After analyzing it a bit, we have decided that the initial compression of the air in the 2’ pipe is heating it enough to throw the transducer off for a while.  I had been hoping to avoid having to pack grease in the transducer, which will prevent us from using it on a tank again, but it looks like we are going to have to do that to get good data.  Still, we believe that the point that it leveled off at is probably reasonably correct.  That was only 80 psi, which is quite a bit lower than we were thinking.  This pack had a total of 106 screens, 20 of which were 80 mesh, and the remainder were 20 mesh (alternate silver and stainless).  It was running with the solenoid valve, and a restrictor jet.

 

run 3:

400 psi ullage

140 psi chamber

 

run 4:

350 psi (ran out of nitrogen on this tank)

We changed the solenoid out for one of our big ball valves

150 psi chamber

This showed that the solenoid was a significant pressure loss.

 

run 5:

350 psi

big valve

increase jet size from 0.080 to 0.120

got rough

This showed that even with our smooth running pack, we do still require a pressure drop at the jet.

 

run 6:

Repeat run 4 to make sure it returned to smoothness.  It did.

We could probably get a bit more chamber pressure by experimenting with in-between jet sizes.

 

run 7:

Increase pressure to 600 psi

270 psi? may not have leveled off completely

 

We will probably repeat some of these tests with a better insulated pressure gauge at some point.

 

We then did some kerosene biprop runs:

 

run 8:

250 psi regulated

0.080 peroxide, 0.018 kerosene

perfect light, dead smooth thrust on both monoprop and biprop runs

This was absolutely gorgeous – the exhaust was as steady as a welding torch, with lots of mach diamonds.

 

run 9:

we set up for a 60 second burn, but the engine began acting a little strange right off the bat, with the exhaust plume wavering a bit and changing character a little each time it was relit.

 

run 10:

We put the kerosene solenoid batter on the charger, thinking it might not be opening the solenoid fully.

Still acting a little strange, some leaks evident

 

March 9 Engine Tests

 

We found that the catalyst pack that had been acting strange was actually cracked at the flange, and severely warped.  The chamber with the water jacket isn’t distorting at all, but it looks like the biprop runs are cooking the cat pack flange quite a bit.  We should probably make a stainless cat pack holder before we try any more long duration biprop runs.

 

We got the first test sheet of our new plated foam catalyst for testing.  This is supposedly a better grade of foam than our previous material, and has been annealed after the plating, which is supposed to make is a lot more resistant to stripping the silver off.  We had the entire process done by Porous Metal Products, at about $200 / square foot, which was much more expensive than when we just had the foam plated at a local plating shop.  That is still a lot cheaper than buying screens from McMaster, but more expensive than buying screens from Haver.

 

We pulled one of the 1/2" throat attitude engines off the lander, and built a new pack for it.  We made two other changes from our previous packs:  we used one of our new water jet cut perforated stainless retaining plates to replace the previous mild steel perforated plates that were severely bending, and we used the spiral retaining rings for anti-channel rings.

 

The initial pack had 24 foam discs.  These runs were mostly at 600 psi, which is the pressure we need to run the lander at for liftoff with a person.

 

run 1:

0.120 peroxide jet

large ball valve

400 psi ullage

600 ml peroxide

60 pounds thrust

mildly rough, about what we saw when the old foam packs were running well.  The annealed foam doesn’t seem to light of quite as instantly as our older foam.

 

run 2:

600 psi

800 ml

85 pounds thrust

We had been so used to testing the tiny little motors recently that we had forgotten to bolt down the test stand, and this run shoved the test stand back a foot or two.  Oops.

 

run 3:

600 psi

0.100 jet

800 ml

78 pounds, slightly wet, slightly rougher

Pack seems to be degrading.

We opened up the engine, and found that there was still some stripping of the silver going on with the top two disks.

 

run 4:

Added six more foam disks.

600 psi

0.100 jet

800 ml

72 pounds thrust, very smooth, almost as good as the screen packs.

 

run 5:

600 psi

2000 ml

75 pounds

very smooth

 

run 6:

600 psi

0.100 jet

75 pounds

4000 ml

got rough at end after running smoothly for quite a while

 

run 7:

1000 ml

500 psi

still rough

 

We opened the engine up again, and found that there was some more stripping, and that the pack had compressed itself another 1/16”, which seems to be the cause of the roughness.  The anti-channel rings had done a great job, the sides of the pack were pristine.  The stainless retaining plate was also still in perfect shape.

 

The new packs are certainly lasting better than the old ones, but it is hard to tell how much of that is due to the annealed plating or the spiral anti-channel rings.  However, the incremental compression of the foam seems to be the cause of the roughness, and is fundamental to the nature of the foam.  We discussed two possible options for avoiding the compression:

 

Alternate foam disks with very coarse 8 mesh stainless screens, and compress the pack so that the foam is completely fitting between the screens, with the screens providing all the structural strength.

 

Alternate foam disks with washers, and compress the pack until the washers are taking all the load, and the foam is squashed flat on the outside.  This probably wouldn’t work at high pressure, because the foam would just tear through the center.  It might work at low pressure.

 

At this point, we are probably giving up on the foam packs, at least for our current set of applications.  There is still stripping evident, so they are unlikely to last as long as we would like, and the roughness from compression problem has not yet had a solution demonstrated.

 

The foam might be useful for a low pressure engine, which would have less of a problem with both stripping and compression, and would benefit the most from the reduced pressure drop versus screens.  One of our vehicle designs may have a large, low pressure engine (fired only after the rotor lifts the vehicle high in the atmosphere), so it is still worth thinking about.  It would be nice to do an identical, back-to-back test of a screen pack and a foam pack in the exact same engine (sized for the screen pack, with spacers added for the foam pack) to quantify the difference.  We aren’t sure if we are stuck with paying for the complete foam order, or if we can cancel right now after testing the first article.  If we are stuck with it, we will probably investigate some of the other options.  If not, we are going to concentrate on the pure silver / stainless screen packs.