Monday, September 29, 2008

LLC Schedule

The LLC teams had a conference call Sunday at 11am PST to discuss the 2008 schedule. I asked if I could blog about it and was told that I should wait until close of business Monday.

Its Monday and I have not heard otherwise so here is what I know:

The Xprize team is trying very hard to keep the original October 24/25 date. They are currently planning to hold the event at the Las Cruces airport, the same location as the 2006 event. This involves a change in the pad distances and a whole bunch of new coordination. It will be a real rush to get this done in the next 25 days.

When the event was originally delayed I’d been a tad relieved, now that it is back on for the same date I have a boat load of work to do. I could not sleep last night so I got up at 2:30 and started writing. I wrote up a bunch of items to e-mail my FAA contacts and had several follow up phone conversations with them today. They noted with some amusement and possibly concern that my E-mails to them were at 8:30 PM on the 28th and 4:04 am on the 29th.

I’ve just finished revising my experimental permit application to reflect:

  • The Change in Venue

  • The Change in pad distances (50 to 100M)

  • The changes in the vehicle (Switch from leg tanks to sphere tank etc..)

  • Changes in operational procedures that have matured with the recent testing.

  • Changes in the order of things accomplished in flight tests.

  • Documentation of verification items completed.

I will publish the revised document when the project is complete this year. (I will also publish all the software schematics, and what detailed design notes I have at the same time.)

Now that the vehicle is flying my son is in the process of taking all the spare parts and building a duplicate. As the Armadilo guys told me don’t get too attached to your vehicle you will eventually loose one. Its a hard thing to face and with the upcomming free to altitude (55m) untethered flight comming up its a bit scary.  However we did not build a mueum peice, we built a flight vehicle and when  it is eventually lost thats part of the game. See the last flying vehicle I designed from scratch:Solar Splinter I’d still be working on that project if the FloMetrics guys had not gotten me hooked on rockets. Thanks Steve and Carl! I still have my rare stash of 20% efficent bare back contact solar cells and will some day do that one again.

Sunday, September 28, 2008

Slow motion video

Ben Brockert one the the Masten guys came out to watch.The following is a comment Ben sent to Arocket:

With permission from the Pauls I also took it as an opportunity to

test some of the MSS ground support equipment that I'm responsible

for, in this case the high speed camera.

Flight 4, first from ground, 1/10th speed:

Flight 5, off-nominal engine burn (steam?), 1/10th speed:

The Right Stuff:

We have 3 HD cameras and high speed capabilities to 1200 frames per second. If anyone wants to test an engine or system in Mojave, we're happy to consult and document.


Congratulations SpaceX!

I watched the launch, and  it looked perfect.

Way to Go!




From the ground

Saturday, September 27, 2008

From the ground

We flew 7 times today, the primary changes were the addition of 25Kg of payload and some tuning of the vertical loop constants , both turned out perfect.

Flights 1,2,3  Perfect take off from the stands hover for 5 seconds at 1.5M then land.

Flight 4 Perfect Still attached to tether, but sitting on the ground Take off hover for 5 seconds land on the ground.

Flight 5 attempt on take off from the ground only got the ctalyst valve partially opened. We arn’t sure why,  we should  know more when we review the data. It took off, but could not maintain altitude and settled back on the ground in water rocket mode.  No damage. We reset the valve controller and …

Flight 6 the  third flight  from the ground to hover and back to ground was perfect.

The last flight was a very short flight to from the stands to burn off the remaining peroxide from the last flight. It lasted maybe 4 seconds. Again perfect no damage.

Some of the Masten folks came out to watch and Ben got some really cool slow motion footage of the flights. (Look for him to post it soon)  I’ll review data and post a video or two on Sunday. Right now its been a long hot day , I’m grumpy, sunburned and  don’t feel like editig video. ;-)

We have finally reached the point many rocketry people have dreamed about: Fuel is a significat cost. Our next flight series will include a 90 second hover with payload and the peroxide cost for that flight will be noticiable.

After that we need to do a free flight to 50 meters translate out, translate back and we will have completed the testing series required for our experimental permit.

Thursday, September 25, 2008

It gets easier

I’m preparing to go out and test again this weekend. Were planning to test Saturday Morning, were goin out Friday Afternoon. There is a FAR workparty trying to put up some shade and we vouelteered to pick up the steel roofing. We need to pick it up around 3:00 PM Friday in Ontario, CA. This means we leave around noon.

I’m spending this evening getting ready. Its the easiest prep I’ve ever done. The only hardware change is to add 25Kg of Payload to the vehicle in the form on srap on Ankle weights on the tops of the landing gear.  Earlier my Son and I  I flushed the Permangenate system and did a full operational check of the vehicle.

Other than that I’m charging all the batteries

  • 2 main flight batteries

  • 2 Main flight battery spares.

  • 2 IIP Abort batteries

  • 1 Emergency Vent Rx battery

  • 1 Emergency Vent TX battery

  • 1 Controller TX battery

  • Primary Lap top

  • Spare Laptop Battery

  • Spare Lap top

  • 2 Video Cameras

  • 2 Extra Vido Camera Batteries.

16 Total.

The only other physcial preperation is to copy some new anaylisys software to the Laptops and make sure the backup laptop gets updated with all the new software thats on the primary. It looks like the toal prep time will be less than 4 hours! WOOO HA!

If I’m going to fly under my flight waiver (longer than 15 seconds) I need to “clear” the uninvolved from the area. Since I’m going to be working on takeoff and landings this weekend the flights are all going to be under 15 seconds, under amateur rules. This is probably one of the better opertunities to come see the vehicle.

We test out near Cantil CA. If you want to send me an E-mail (you’ll have to answer my spam filter) with contact info I’ll give you a call Friday to discuss how to get there. I’ll be packing up by 11am so later than that and I won’t get back to you. My email is Paul at Romeo Alpha Sierra Delta Oscar Charlie dot Charlie Oscar Mike.

Monday, September 22, 2008


When I started this project I wanted to show that significant things could be accomplished by a very small team. With our recent successful flights we have in some ways reached that first goal. We are going to keep striving to compete at the NGLLC, but it also seems like a fitting time to acknowledge some success and explicitly  thank some people:

My son Paul. It has been a privilege to spend the last 18 months working so closely with my son. He has done most of the non-electronic physical fabrication. He has also been invaluable is a huge number of logistics issues like making sure we have a crane, propellant, catalyst etc…. The project would not be remotely possible without him. When I was his age I spent two years working on a race boat project with my Father, I know it is not always easy.

My Wife Mariellen.  My Wife has been 100% supportive of me and my insane project. She has helped me keep an even keel during the inevitable ups and downs. She has been completly selfless as my Son and I have been absorbed by the project. Without her assistance none of  our progress  to date would be possible.

Charles Pooley of Microlaunchers. Charles has spent many many long days and nights at the FAR site providing us a helping hand. He has offered countless small suggestions. he is an invaluable resource into the history and methods of rocketry at all levels. He has always been available to help and has been an invaluable member of the team.

Beyond these three there are dozens and dozens who have helped, in no particular order, Steve and Carl of Flometrics, Bob our welder, Tom and the rest of my coworkers at Netburner, Kevin, Mark and Ted of FAR, John Newman,  John Carmack and the whole Armadillo team, David Weinshenker ,Mike Carden of XL space systems, Mike Kelly, Wynn  and Nick on my FAA team, and many many more.

Bonus videos

Fairly good attempt at a 5 Second flight with a Landing….

Diizzy footage from on board during the “Plus” flight.  I cut the start a bit too tight and missed takeoff…


Sunday, September 21, 2008

Code Test....

Given the following snippit of C code we are attempting to add damping or differential correction to the pitch stability. The values gain and DiffPitchRoll are constant doubles used to adjust the various gains.  This chunk of code runs 75 times a second and er.Pitch is the IMU raw pitch output. Given we want rate damping what should the sign of the differential correction be ?

/*****************Code Snippit *******************/

 static double pitch_prev;  
 double cur_pitch=PitchConvert(er.Pitch);
 double pitch_err=Target_Pitch-cur_pitch; 
 double pitch_change=(cur_pitch-pitch_prev); 



/*****************End Snippit *******************/


What should the Red ? Be?

If you choose ‘-‘ goto this video: Minus Video

If you choose ‘+’ goto this video: Plus Video

(We have a tethered burn time waiver inplace.)

The vehicle was undamaged in both videos above,  We need to work on the altitude control a little bit more and we did eventually tangle the ropes around the the GPS antenna mast 3 flights after the “Plus” video and broke it off….all in all a good day.




Saturday, September 20, 2008

Testing again...

We plan on testing Sunday Morning. As A side note the contest has been delyayed at least a month. I have mixed feelings,  I really need the month, but I was also looking forward to being doen.From a fairness standpoint this is really unfair to armadillo.





Thursday, September 18, 2008


I got up at 6:30 am on Tueasday. I went to work and did a few hours of “Support”. I spent the balance of the day double checking everything on the rocket. We left the house at 8:30 PM headed for  FAR.  While filling the truck with gas  I noticed something on the vehicle was rubbing that should not be rubbing back to the house realign the main valve and leave at 9:15PM arrive on site a 1:00 am. Sun comes up at ~6:30 finish unpacking and setting up the vehicle. First thethered flight attempt at 9:00 am. The first attempt is a no launch as we had made some adjustments to the “Throttle controls “  and we had a sign wrong on the vertical acceleration. Played with software for an hour tried again. Between 10:am and 6:00 PM we did 8 or 9 short less than 10 second flights. We were trying to squeze in one more flight before dark, alas the data reduction from the previous flight pushed us past dark. We packed up in the dark and left the site at 8:30PM We drove to Mojave had dinner and then drove home. Arrived home at 1:15 AM. I slept the first half of the drive and drove the 2nd half. I’m now wide awake (and hence everyone gets an update) Many thanks to Charles Pooley and Kevin Baxter for their help today.

Good news and several problems:

Good news: We had almost no  hardware or electronic issues, we had 8 or 9 flights with ZERO damage. We got data from all but one flight and good video from two or three angles for each flight.


1)The motor is really inconsistant. I think there are issues with the catalyst. We had clogging issues with the aluminum plumbing, we now are all 100% stainless, but the catalyst still has issues, we are going to flush the system and see if anything is clogged. My guess is that one of the checkvalves or orfices is clogged.

2)The Helicopter manuvers differently than the rocket. When you tip the helicopter to the left, the helicopter moves immediatly to the left, when you tip the rocket to the left, the vectored thrust act of tipping actually moves you to the right. The helicopter also has a  LOT more damping than the rocket does. I think we need to add an explict pitch/roll rate loop to the code.

3)The Rocket is really sensitive to the horizontal CG we need to balance better.

4)Minor: A Black plastic pelican case (Holding the telmetry radio) gets WAAAY to hot in the Mojave sun. IT needs to be shaded or it  starts getting flakey. When we found this problem it was TOO hot to touch.


Tuesday, September 16, 2008

Testing again...

We are headed out to test on Wedensday.

I’ll update when we return.




The Video is up on you tube.

I’ve also posted a higher quality version myself.

Please download and view rather then veiw online as the keeps me under my bandwidth limits.



Monday, September 15, 2008

Test Results

We did one tethered test this weekend.We intended to do a 10 to 14 sec stable hover at 2 meters in altitude. It seems like the throttle gains were a little bit aggressive as the vehicle was very lightly loaded with fuel. It jumped up to 3m  and started to swerve  in pitch .as the throttle over compensated and interacted badly with the pitch loop. To protect the vehicle I had set aggressive abort limits (20deg in pitch and roll) It hit the abort limits and shut down. The vehicle coasted up to 4m then began to fall  while slowly continuing to roll in pitch. When the tethers came taught at the bottom the vehicle was almost inverted. I had used PVC tether covers like Armadillo does, but I had not secured them in position on the vehicle. they slid up the tether ropes and formed a loop that caught around the peroxide vent valve and the primary flight control battery. When the lines snapped taught it removed both the vent valve and battery.

The Tethers absorbed the shock and prevented the vehicle from contacting anything other than the tethers. Other than the vent valve and battery mount the vehicle is undamaged. In reviewing the video the I am very pleased with dynamics of the tether system.  I inspected the tether mounts on the vehicle and saw no signs of damage or distress from a fairly severe usage.

As soon as I saw the vehicle abort I reached for the command abort RC transmitter to depressurize the vehicle. The removal of the main peroxide vent started the de pressurization, but that vent is VERY small, so when I activated  the emergency vent one heard a distinct POP and  large woosh. Lasting less than a second.

The 900Mhz primary telemetry channel is used for both data status download and command upload. To insure reliable command upload I've reduced the data coming down from the vehicle. The largest part of this data is the IMU data and the control loop responses.  I record 100% of all vehicle parameters at full rate on board   on a 2Gbyte micro SD flash card on the vehicle.  this recording process has between an 1 and 2 second delay. As the tether loop removed the vehicle battery we lost the last 2 seconds of the 2.5 second flight.

Anomalies and corrective actions:

Emergency Vent:

The emergency vent uses off the shelf COTS RC equipment. the servo arm and linkage controlling the vent used to be plastic.  It looks like chemical and weather exposure made the linkage brittle and we broke it when preparing the vehicle for flight. We repaired it in the field with some safety wire. (Its in tension to operate the vent) and it operated  correctly as indicated above. We are going to replace this with a proper  all metal linkage before we fly again. The present wire linkage will actuate  100% reliably, but it might also allow it to activate without being commanded.

The Tether ropes:

The dynamic 9.5Kn climbing rope worked very well. The PVC pipe covers did not work correctly.We have already modified these to extend them and retain them on the vehicle end to prevent rope loops.

Pressurization Quick disconnect:

The dual pressurization quick disconnects were actuated twice, the first time only one of the two disconnected. After de-pressurizing the vehicle and trying again both actuated.  As the vehicle was up on blow out stands we could not pull on the end of the hose as we could if the vehicle was on the ground. So in a "real" flight its likely that  we could have recovered from this failure.  The disconnects were designed to be rugged as they will fall to the pavement after every actuation. The one that failed to deploy  had been "Adjusted" by prior test impacts.

Control laws:

We have already modified the throttle control loop to change the behavior and we intend to try again on Wednesday.


We repaired the valve and attempted to re-fly on Sunday, but  we had intermittent computer hardware issues and choose to return to San Diego to evaluate.  We evaluated this on Sunday night and it looks like an epoxy blob we used to pot the wires coming off the PCB lifted a an IC lead.  The cause and effect is unclear here as another lead of this IC (Not under the epoxy blob),could be displaced with a probe and appeared not to be  soldered. We are in the process of swapping out the primary carrier board that holds the peripherals for the flight control computer. We will get that assembled today and I will probe every single IC lead solder joint under the microscope before installing it in the vehicle.


I will try to post the vido in the next 24 hours.

Saturday, September 13, 2008

First Tether Flight

We had our first tether flight today. Not perfect, but ok. it was stable for the first two seconds or so, but then we had some throttle osscilation shutting off thrust completly and hitting the tilt abort limit. I'm still reviewing data to learn the order of events. The Tether system worked as designed with only a very minor damage to some vent plumbing on the top of the rocket. (Caught on tether rope, the PCV tether covers ALA armadillo were not long enough.) Plan to review data and video this evening and try again on Sunday. Posting from the Mojave Best Western so no video or pictures yet. It flew, and its still flyable.


Thursday, September 11, 2008


Just finished the Vane direction test. I have the vehicle hanging from a hook in the garage roof. It can be easily tipped or twisted. Its high enough that you can lie on the floor under it and observe the vane movement. For this we assume that the GPS has no fix and thus  the IMU is setup to try and hold a constant roll, pitch and yaw of 0. I exaggerate the gains and tip/twist the vehicle and observe that the vanes move the correct direction to counter act the roll pitch or yaw. It was working perfectly then it would suddenly pitch over and act strange.

After several trips through the code I realized that the GPS was getting a fix and it was trying to navigate to the next way point. Very surprising because the garage roof is where I store all my thing sheet metal so I would have bet there was zero chance of a GPS fix. In any case it looks like it is still a go for a Friday departure and a Saturday test.

Wednesday, September 10, 2008


If all goes well we will do a tethered hover this weekend. We have worked on this for close to two years. This weekends test comes with a good bit of fear, not physical fear, but emotional fear, its hard to work on a complicated project for this long and not have a million small doubts. 

One could always wish for another 6 months to test everything 9 ways from sunday, but eventually you have to give it a try. The helicopter is almost exactly  flying the hover test profile we want to fly. I’m a little concerned that we don’t know the exact gains for the throttle valve so I’m going to do a test of the helicopter where the software attempts to learn the helicopters collective gains in real time in flight. I’ll use this on the vehicle. (Update Thursday mornings helicopter gain test worked as planned)

Monday, September 08, 2008

North to the prize.....

The problem with the new software is a heading issue. The vehicle is supposed to stay pointing north, it wanders as much as 30 degrees. This causes a cross coupling between the E-W Roll and N/S pitch corrections. I still have not figured out why the new software won’t properly hold a precise heading, but I added the full heading coordinate transform to the main flight control loop and it works! On to the next problem….




Friday, September 05, 2008

Software Woes

A long time ago( a year ago) we had a software design.

We created a code structure for this software that matched this design, and then it branched.

One branch turned into vehicle control software optimized to run static rocket tests and gather data.

The other branch learned to fly the helicopter.

Over time the two branches grew and mutated until they were not really recognizable as twins.

The vehicle branch controls all the rocket actuators and  logs data while running static tests.

The helicopter branch hovers the helicopter in place and successfully moves it to a selected 3D waypoint.

The vehicle branch gains such things as differential GPS and a flash file system to record data.

The helicopter branch gains things like status LED’s and remotely programable modes selectable via the RC transmitter.

About a Month ago as the physical vehicle reaches completion we started working to merge what is common in the two branches in preperation for hovering the vehicle.

We split out the parts that are defferent between the two vehicles into vehicle specific modules and merged the parts that are common.

This merge took about two weeks and the merged software passes all the ground tests we can throw at it.

The merged software almost flies the helicopter, it is just a tiny bit unstable. The helicopter holds position sort of and if its not disturbed almost flies, disturb it and it goes into ever increasing wobbles….

So we added the ability to tweak the control system gains in flight and flew the helicopter, we reverted the GPS to WAAS mode and flew the helicopter, we played with gains and flew the helicopter, we stuck the tail roter in the dirt, we fixed the tail roter, we flew the helicopter, we stuck the tail roter in the dirt we replaced the tail roter gear box, we adjusted gains , we flew the helicopter, we adjusted gains, we stuck the tail roter in the dirt we replaced the tail roter belt, we flew the helicopter, we had a dumb thumbs moment while trying to check the blade tracking in manual mode, and we replaced the gear, the training poles, the main roter blades, the tail boom, the landing gear, and the tailroter ie rebuilt the helicopter, and we adjusted the gains, and our hair turned grayer, and we swore at the helicopter.

We went back to the source control, checked out the last version of the Helicopter before the attempted merge, we reverted the the GPS to WAAS mode, and we flew the helicopter. It flies perfect…..arghhhhhhhh!

So we know its not the GPS, not the IMU, not the servos, not the helicopter mechanics, or any thing else it’s the software and as far as I can tell the control laws and delays are identical, just rearranged into different files.