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More methane engine development, WSTF tests, high-pressure Mod work, and more...

May 5, 2009 notes by Phil Eaton:

List of Accomplishments since the last update:

  1. Methane engine Finalized and coated internally by Ncoat Inc.

  2. Methane engine Tested for NASA with the J2-X Pyro Ignition Module.

  3. Coaxial Swirl Injector development.

  4. V-Cut Ball valve results.

  5. Self Pressurization issues.

  6. New Coaxial Swirl Injector flies Mod with Self Pressurized Propellants.

  7. Rocket Tug Of War.

  8. Linear Actuator issues fixed.

  9. Methane Engine Run in WSTF Altitude Chamber

  10. Mod XL rebuilt and ready for another test.

  11. Class 3 Waiver progress.

  12. Preparation for Free Flights.

Since the last update, we have been pressing hard on many fronts. In addition, John has been so busy with his duties at id Software, that he has not had time to make the normal update himself. Thus you are stuck with the storyteller rather than the technical presentations you may be used to.

NASA Methane Engine Work:

After the Methane engine had the nozzle replaced, shown in the last update, we sent it to nCoat for a new R&D coating they had produced designated H1008. http://www.ncoat.com/ You will have to contact them directly to request the H1008 above as it is not yet on their product listing.

This coating was much better than a previous coating they had done for us, and the only place it appeared to wear was right at the throat. The coating is good for temperatures in excess of 4000 degrees F for an extended period of time under normal conditions. Under supersonic conditions as seen in the throat of an engine however, it stresses it to the limit if not slightly beyond. It still hung in there for the 3 tests we did here, and the tests we ran in the altitude chamber at White Sands Test Facility in Las Cruces.

Minor discoloration, a slightly “melted” look and one spot that flaked off the surface was all that happened to it over 3 to 4 minutes of firing. The remainder of the areas that were coated look as new as the day we received it. It was especially helpful on the large bell nozzle in the altitude chamber. It really helped cut down on the heat the nozzle would see as the film cooling is getting really thin by the time the bell has expanded it out.

That said, we managed to do a static test of the coated methane engine in the morning with one baseline run using a normal torch ignition sequence.

Video (WMV, 1.4MB):

Methane engine sled test run 1

We did a second test using the J2X Pyro igniter made by Pacific Scientific, which was the first ever ignition of a LOX/Methane main engine with a pyro igniter.

Video (WMV, 1.5MB):

Methane engine sled test run 2

Photo courtesy JC Melcher (Click to enlarge):

Methane engine sled test pyro ignition

After a quick lunch break we had installed the engine on the mod and ran the first ever flight of a LOX/Methane powered vehicle with a Pyro igniter.

Photos courtesy JC Melcher (Click to enlarge)

Methane engine hover test pyro ignition Methane engine hover test pyro liftoff Methane engine hover test pyro hover

Video (WMV, 4MB):

Methane engine hover test pyro hover

Overall it was one of those really good days for Armadillo until later on in the afternoon; we accidentally left a Li Ion battery pack on charge with the protection circuits disabled. Yes, they really do explode and burst into flames. The smoke is rather unpleasant as well, and filled the hanger rather quickly! It was easily extinguished and did not cause any damage, but it left us with a better sense of respect for the energy in those batteries.

Coaxial Swirl Injector and Self Pressurized work:

As soon as the work on the full density engine for NASA was complete, we started working on a self pressurized system in order to do away with helium pressurization, and fill the tanks to their full capacity. This configuration doesn’t have any performance gains for hovering or flights within the atmosphere, but it certainly has some benefit if we can create a very light weight, low pressure system as an upper stage and operate all the way down to vacuum. It also may be an interesting direction to pursue for longer and lower thrust runs on similar sized systems we would normally use for pressure fed LOX/Alcohol.

We made an injector very similar to the Like impinging full density injector with larger orifices, but there was only just enough thrust to get the unit off the ground with the propellants pressurized to 200PSI. This particular test was very valuable however because we ended up short loading the LOX and ran out of LOX before we ran out of LCH4. The transition was perfectly smooth between liquid and gas phases. After reaching full throttle, the vehicle gently descended with no ill effects. The same could not be said when the LCH4 made its transition from liquid to gas. The same effect of throttling up was occurring to a smaller degree, but the fuel turning to gas was insufficient in the film cooling thus a bright flash indicating burning stainless shortly followed. After inspecting the engine, it had eroded at the throat only. Everything else was intact.

We discovered that our results were varying greatly depending on our hold time and discovered that the tanks getting to pressure did not guarantee that the density had gotten to the appropriate point. We moved back to testing on the sled and installed thermocouples at the bottom of the tanks to monitor the temperature. This was an excellent data point because the hold time required to get the temperatures to the appropriate level were more than double what we had been waiting previously. The initial runs were autogenous blow down runs rather than a self pressurized run, which was also confirmed in the pressure trace data. The tank pressures clearly would fall off as soon as the run started.

At 200 PSI, the temperatures would stabilize after about 45 minutes without touching the tanks. If we took a broom to the tank and kept the Texas-humidity frost off of them, the time would cut down to 20 minutes easily. It is amazing how effective frost can be as an insulator. Finally we achieved a good solid series of runs that had the capability of running at full throttle and low throttle positions without burning the engine. We had to increase the orifice sizes of the injector and the film cooling to be much larger than calculations would indicate because the lower density propellants would go to 2 phase flow in the injector and restrict the flow capability coming through the injector.

(Click to enlarge)

Methane engine sled test 2009-02-14 Methane engine sled test 2009-04-18

Matt purchased one of the new Casio cameras that can do the high speed video in the last 2 months and has had lots of opportunities to test it out. The video below is a really good shot of start up and shut down of a self pressurized swirl injector run at 600fps.

Video (WMV, 2MB):

2009_04_18 Methane sled test high-speed startup and shutdown

After the engine was verified on the sled, we began testing on the vehicle again. It appears that we have a good engine to proceed with now. It took us 4 tries to get the swirler right for self pressurized hovering, but it appears to be working now. It takes much longer to run on the mill than the old designs, but we can get significantly better performance from it with less L* than the Like Impinging injector.

The biggest problem with running self pressurized as opposed to blow down is that the pressure in the tanks remains constant within 5 to 10 PSI over the whole flight. This means the engine has to throttle much deeper to offset for the difference in weight from start to finish.

Our early attempts at V-Cut ball valves indicated that there was a much higher restriction than anticipated with self pressurized propellants, so we went back to 1” full port ball valves. Unfortunately, the partial throttle positions seem to be a little less precise than we would like, but it is still working. We just have to change the minimum throttle position so that we can land effectively without adding extra ballast weight.

Below is some 600fps video of the Mod starting and shutting down on a hover using self Pressurized propellants.

Video (WMV, 8.6MB):

2009_03_23_Methane hover test high-speed select

Now that the Engine is working properly, we have begun doing some of the preliminary testing for boost and return flights here at our home base under the new amateur rules. We wanted to get a feel for how the vehicle would react to sudden changes in wind speeds as it moved upward. The only thing we could think of to induce a similar force was to attach a really long cable to one of the legs and have someone pull on it during a hover.

Russ discovered that the rocket has a significant amount of force to apply with gimbaling the engine, and it amounted to him playing Tug Of War with the rocket in flight. The gains were doubled from the first flight to the second flight so we could see how the vehicle responded in attitude and position. This is also the set of flights that we had problems with the linear actuators. On both flights, one or both of the gimbals would go “off scale” and freeze up.

Video (WMV, 9MB):

2009_04_21 Methane hover tug-o-war test

John made the call that we would not do any further flights until we solved this problem, because we now have not only the gimbals operated by these actuators, but the linked throttle set up as well.

We spent a good deal of time dissecting several actuators that had the problem on the vehicle. Oddly the problem would not show up on the bench at first. I decided to assemble a test unit that used a needle sweep to show the voltage feedback rather than just read the voltage so we could test them under the same conditions as the vehicle. That was still showing that one of the actuators was good that was failing on the vehicle. We then rigged up a ground strap that we could connect to the body of the actuator, and Bingo, the failure showed up on the bench.

(Click to enlarge)

Linear actuator test unit Linear actuator test unit

After pulling the bad units apart, it was discovered that after using the units for a while, the ball screw nut housing was rubbing on the wiring at the top of the resistor area and when it got through the insulation on the wire, it would short to the housing and cause the failure. The problem did not show up if the housing was not grounded.

Russ and I looked at the units and decided that if we turned the resistors around and made the wiring for the feedback come out at the bottom there would not be anything to hit it, and it should fix the problem. We built up one unit first and verified that this worked extremely well. It also changed the dynamic of the voltage so that if it did go off scale at the full retract position, it was on the zero volt side, and the unit would just stop driving. It would not present itself as a lock up failure as it could still drive the other way when commanded. The other units were modified to match and reinstalled on the vehicle.

We then did another Tug of War test the same day, and this time we were able to vary the gains between the Position hold and Attitude control. We ended up with a position hold of 1 and an attitude control at 1.5 that seemed to work the best.

During the first flight you can see as the gains are varied from one pull to the next. On the last pull, Russ decided not to pull as hard, but kept steady pressure on it and followed along with the rocket until it went farther than we wanted so we shut it down.

On the second flight, we had the gains dialed in to balance the attitude hold plus position hold parameters without as many oscillations. Right at the end of the test, is where the vehicle ran from self pressurized methane to gaseous methane followed by a nice bright flash.

Video (WMV, 11MB):

2009_04_25 Methane hover tug-o-war test

Linked Valves: (Click to enlarge)

Linked Valves

NASA White Sands Test Facility (WSTF) testing

While we were running all of the Self Pressurized testing, the NASA folks were installing the Full Density Methane engine in their Altitude Chamber and preparing for the runs. There were a few problems however.

Photos of engine alone mounted courtesy Jacob Collins (Click to enlarge)

Nozzle extensions WSTF SASS Mounted engine with expansion bell Engine mounted in SASS WSTF SASS

Normally for an engine this large they would run the Large Altitude Simulator System (LASS). This system is basically 3 LOX Isopropyl Alcohol Rocket engines with a very large steam injector system that creates enough volume and pressure steam to pull the chamber down to 160,000 feet and hold it there when the engine inside the chamber is running. The water is pumped by 4 very large Diesel engines, and the alcohol is pumped by 3 smaller diesel engines. Following is a nice photo sequence of the LASS Set up.

(Click to enlarge)


Unfortunately, they have had some personnel turnover lately and the only person certified to run the system had suffered a stroke the week before the test. We all hope the best for him and a quick recovery!

This left the option of running the system with the Small Altitude Simulator System (SASS). This unit could only pull down to about 120,000 feet, but it could not hold it there during the run. This was a desirable situation for us to have though since we were running a dual bell nozzle. One of the things we wanted to see was a sweep in the altitude to see if the nozzle would jump from one bell to the other without a bad thrust vector from gasses delaminating in a non symmetrical fashion. Normally, they would hold this as a very undesirable condition but under the circumstances, the whole NASA team was pulling out all the stops to make this the best test they could provide. We were GO for SASS!

Following is some photos of the Control room where all the magic happens. After seeing this, I was motivated to upgrade John’s station from a card table to something a bit nicer, but that will have to wait!

Photos courtesy Jacob Collins (Click to enlarge)

WSTF SASS Control Room WSTF SASS Control Room WSTF SASS Control Room WSTF SASS Control Room WSTF SASS Control Room

Everything was in place and they ran the baseline 5 second runs at ambient pressures. We are ready for the Dual Bell installation and Altitude runs. The first run is going to use the pyro igniter, and the chamber will be set initially at 117,000 feet with a planned run time of 5 seconds.

The Fire sequence is initiated with a “Fire Red”, and after the initial LOX dump, the engine throttles up simultaneously with the torch ignition. There was a bright flash that obscured mostly every camera in the chamber, and a half second later, the video screens show a beautiful blue flame fully expanded in the 26” nozzle!

(Click to enlarge)


Unfortunately, the temperatures elevated to a level higher than expected so the test was terminated right at the 5 second mark with a “Fire White” call.

We shut down for the rest of the day to evaluate the data. As it turns out, the 200 milliseconds between main valve open and ignition provides a rather large supply of Methane and LOX to dissipate. At ambient pressure it just burns away quickly below the engine. At 110,000 feet however, the ambient pressure being less than 1PSI causes the cryogenic material to expand much more quickly. When it ignited in the altitude chamber, it caused a rather large fireball that extended above the engine area up into the 2nd story of the altitude chamber.

We reviewed the high speed data and reworked the ignition sequence to do away with the LOX Pre-chill, and just start with a 200Msec LOX lead. We would also be using the Armadillo torch igniter rather than the pyro igniter this time. We also compared the ignition sequence to the LOX/Methane run they did last year with the old Lunar Lander RS-18 engine. It had slightly more thrust, but was close enough to be comparable. That engine was run using the LASS. The engine ran between 1 and 2 seconds long, and showed a visible flash right at the start just as ours did, but running the LASS as opposed to the SASS, the eductor was able to pull all the remnants of propellant out the eductor rather than it all dissipating into the chamber.

The sensors in the chamber recorded temperatures in excess of 250 degrees F within the 5 seconds of the run. It was not clear if this was from the extraneous burning, or if it was the accumulation of heat in the altitude chamber due to the SASS not being able to pull all of the gasses out of the chamber. The Thermal sensors were shielded to make sure that they were not picking up radiated energy, and everything was reset for another try.

The plan was to run the engine for a full 20 seconds this time and start at the highest altitude they could, 120,000 feet, with the SASS.

The engine is fired, and the flash was still present although much more subdued. Jen Allred, the person taking the lead on our project for the WSTF facility, is staring at the temperature graphs of the chamber hoping that the temps stay below any level that they think might cause damage to the test cell. The High Def Video returns a beautiful flame coming from the monster bell once again, but this time, you can visibly see the altitude change affecting the shape of the plume. Jen held on for nearly the full 20 seconds, calling “Fire White” only when the temperatures spiked above 600 degrees F!

Following is a gorgeous video of the run from the main High Def Camera. You might have to turn your volume up a bit to get the full effect…

Video (WMV, 3.4MB):

2009-04-17 WSTF SASS Hotfire 10

If turning the volume up doesn’t work, play some other rocket video at the same time. It just doesn’t sound right like that!

Mod XL Work

Between Swirl Injector iterations, we managed to put in some time on the Mod XL, AKA the Pressurized Module. Well, at least James got a chance to put in a bunch of work. It is completely recovered from its cartwheel event, and nearly ready to fly. We need to do a few water tests before we load it back up and take it to the pad for another go, and we still have to fabricate 2 additional attach points for tethers so we have it hanging on 4 points around the tank instead of 2. And yes, we will be using Grade 8, 7/16” bolts all the way around.

(Click to enlarge)

Mod XL Mod XL

Very soon we hope to be able to fly our final milestone flight from NASA with the Methane mod using the Self Pressurized system in a full free flight. Right after that, we will be ready to start doing boosted hop style testing. The Mod XL is right behind the Methane Mod on the priority list. As soon as we get a few boosted hop flights out of the way, we will start getting LLC level 2 parameters nailed down on the Mod XL. We will not do any boosted hop flights with the Mod XL until we can successfully close the chapter on the Level 2 LLC prize.

FAA Waiver Update

One of the reasons the update is so late in coming is because we have been waiting for a recommendation from AST to the local FAA office on the Class 3 Authorization for flight at the Caddo Mills Airport. We thought that the process would be a mere formality, and hoped that the full 45 days would not be required. Since this was one of the first class 3 waivers they had to process however, we had to do a bit more work than expected, and they had to figure out exactly how to make the process work on their end. As it turns out, we are getting mighty close to the 45 days from the time we first turned in the application, but I have already received confirmation that they will have their recommendation ready by the end of next week at the latest.

The process of getting the waiver approved has actually been a rather lengthy task. It started in mid to late January, and proceeded through February by having conference calls with the airspace managers and the local specialists that write the waivers. We finally set up a time for all of the FAA Managers and Airspace Managers to come to the shop for a presentation and demo flight operation. There was clearly a misconception of exactly what Armadillo Aerospace does in comparison to other high power rockets.

While Craig McFadden and company looked over John’s shoulder, the procedure and flight went extremely well. Of course our Control console is nowhere near as impressive as the one at WSTF!

(Click to enlarge)

FAA visit

We followed that up with a basic presentation of our history, how we compare to other rockets, and what we wanted to do in the future. They also brought some extremely valuable data that showed the flight rates through our area and at what approximate times. It just so happens that there are 2 major departure corridors just to the North and South of our location. In spite of this, the general feeling of everyone present was that we had enough control over our vehicles that we would be able to fly on cue within windows they could give us, and certainly prevent any breech into airspace that they needed us to stay clear of.

For all of you following and contributing to the recent threads on ARocket; all of this means that the next update should hold some really cool video of an Armadillo Rocket flying free on the Texas horizon, “like God and Robert Heinlein meant them to!”

By the way, Russ Blink might have something to say about the first man to ever fly on a purely rocket powered VTVL vehicle on the Earth…


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