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Lunar Lander Challenge '08 -- We win one!

Lunar Lander Challenge ’08 – We win one

Lunar Lander Challenge ’08 – We win one!

 

We finally won the level one Northrop Grumman Lunar Lander Challenge.  We didn’t get the level two flights off, but we aren’t too upset about it.  It was a great week!  As with the last two years, Matt will be getting together a nice update with lots of media from the effort, but you get the narrative update early.

 

The official X-Prize site has a good highlights video:

http://space.xprize.org/lunar-lander-challenge

 

The webcast was apparently very well received, and I did a very long interview after the flights that I hope is archived somewhere.

 

Preparation

 

With all the work for the Rocket Racing League and the methane engine development work for NASA, we hadn’t flown a VTVL vehicle since January.  We figured that with the more reliable film cooled engines, there really wasn’t all that much that we needed to do, since the only thing that kept us from winning something in ’07 was engine start problems.  After the bulk of the Rocket Racing work died down, we expected to spend six or eight weeks before the contest doing various test flights, especially with Pixel for the level two prize.

 

On August 4th, we got a surprise notification from FAA/AST that tethered vehicle tests are now declared “not exempt from licensing / permitting requirements”.  We have been doing these tests for eight years, often with FAA/AST people on site as witnesses.  This ruling was a shock, and while we have several hearsay accounts of the events that led to this inside the agency, we still don’t know all the internal machinations that led to this result.

 

In early October, when we were still at a dead stop, I even went so far as to write someone in the government outside the FAA that thinks well of us, and ask for some advice.  This is a pretty good summary of the situation:

 

 

I would like to ask you for some advice.

A few months ago, some busybody lawyer at the FAA-AST office of legal council issued a ruling that tethered vehicle tests are "launches" and need a full experimental permit or launch license to conduct.  We have been conducting these tests for eight years, often with AST personnel in attendance.  We acknowledge the necessity of licensing for significant free flights that go through controlled airspace, but testing a control system on a vehicle by hovering it ten feet off the ground while it is attached to a 50,000 pound crane truck is just not a "launch".

This is a launch:
http://www.spacex.com/multimedia/videos.php?id=30&cat=recent

This is not a launch:
http://media.armadilloaerospace.com/2007_09_04/double180.mpg

The current interpretation is that they are the same.

The technical reviewers at FAA-AST claim that they have been fighting against this ruling for the last couple years, but they lost.  I'm not really sure how this works -- the office of legal council apparently trumps George Neild, the actual head of AST on these matters.  We have been working hard to move AST towards using real operational data as the basis for granting licenses over abstract evaluation, because that is a much more realistic way to ensure public safety.  This makes it a catch-22, since we can't collect real data without a license/waiver/permit, so the license/waiver/permit process must rely exclusively on theoretical analysis.  Don't get me started on the issues and limitations of that.

The AST evaluation teams realize that this is basically screwing us over, and they promised to fast track a waiver for the requirement of a launch license for our testing.  We did the whole waiver application dance for them, and they did wind up issuing us a waiver with only a handful of itemized restrictions after only a couple weeks, which does qualify as them doing their best to help us out.  However, there were unintended consequences.  Because our testing operations are now considered "launches", the permitting of which is considered a "major federal action", the parent/sister FAA organization has now decided that everything needs to be given the full treatment.  Since we are now "flying rockets" (even though they are tied to the ground) instead of just performing industrial testing, various FAA waivers are required, and none of these people feel any of the guilt that the AST division feels for inflicting this on us.  In fact, there seems to be something going on where the FAA people are irritated at the AST people about some internal notification issue, and some people in the FAA have decided to require us to do several things that have the local airport managers scratching their heads -- like requiring "obstruction evaluation reports" for us to operate our crane truck on airport grounds.

The NASA lunar lander challenge is in three weeks, and we haven't been able to test any of our vehicles.  Not at our home base at the Caddo Mills airport, nor at any of our other testing sites at Hensley Field, the Greyson County airport, or the Oklahoma Spaceport.  Our NASA development contract is also stalled waiting for a tethered test.  I still hope that our FAA waivers are going to come through any day now, but this has left me deeply frustrated.

This was a bad regulatory overreach, and many of us in the industry worry that they have their sights set on static engine testing next.  We have been protesting this through the Personal Spaceflight Federation, our industry trade group, but there doesn't seem to be any traction.  We had a great relationship with Patti Grace Smith, the former head of FAA, but the new director comes from different circles, and while he has heard our case, there hasn't been any movement.

As an engineer, I have tried to avoid politics my entire life, and I am ignorant of all the details.  I don't expect that there is any political route that can help in the current crisis, but I would like to do whatever is possible to try and get this bad ruling overturned for the future.  I'm sure we will eventually get all of the newly required permits and waivers, and some could look at that as an additional barrier to entry for competitors, but it just isn't right, and there are concerns about future steps that may follow.

If you can offer any advice, or possibly an introduction to the correct person to plead our case to, I would appreciate it.

John Carmack

 

 

As far as we can tell, lots of people inside AST, including the administrator, are really and truly on our side.  We don’t see eye to eye on a lot of issues, but I can usually muster some sympathy for their positions.  However, based on this action, there are people there that I would classify as enemies.  Not “out to get Armadillo”, but definitely taking active steps to make it harder for everyone in the industry to accomplish our goals.  This didn’t happen out of passivity, someone decided they were going to make an issue out of this and lobby for it.  The nearest I have heard anyone come to trying to defend the ruling goes something like “Any sensible tether design will be approved by AST and a waiver will be issued, this is just to prevent dangerously unsafe systems from being used”.  This is the common defense of many laws -- “A just man has nothing to fear from this law.  You are a just man, aren’t you?”

 

Whenever I bitch and moan about regulations, I do feel it is necessary to caveat the statements so people don’t get a mistaken impression of the relative costs.  Some people like to take a stand along the lines of “The government is keeping private companies from getting into space!  Those evil bastards!” or the more personal “My company would have been flying in space now if not for the government!”  The former is just not true.  The regulatory burden does exist, and it does cost us – Neil rarely turns a wrench nowadays, spending all of his Armadillo time doing paperwork, and Phil has been halfway there as well during this latest crisis. Still, it is only about 25% of the team effort, and it would be a smaller amount for a larger team.  If you aren’t capable of getting through the regulatory work, it is a damn good bet that you aren’t capable of building a functioning rocket either.  I do still hear some old timers hint about how AMROC was actively sabotaged, but usually when companies complain about the government it is just code for “They didn’t give me $100 million to build my rocket”.

 

We did finally get all the necessary waivers, and we started our tethered testing on Ocrober 17th.  Hearsay has it that there was an intervention on our behalf from very high up in AST to get the FAA side of things cleared up.  I made the following post to aRocket as the vehicle was being packed up for the trip out to Las Cruces:

 

 

We have burned well over 10,000 pounds of propellant in the week and a 
half since we finally got our tether testing waivers sorted out.  We 
were very fortunate to only have a couple days of rain, or things might 
not have been possible, and I would have been very, VERY bitter at AST 
over the tether ruling.  As it is, we crammed most of the testing we 
wanted to do into one quarter the time we wanted to do it in.  We did 
lots of full duration burns for both vehicles (Matt has a great video of 
another 180 second Pixel flight with the sun literally going down behind 
it), a ground liftoff and touchdown, and a bunch of trim adjustments on 
Pixel.  The only thing we haven't done this year is a full, untethered, 
pad-to-pad free flight, although both vehicles have done several of them 
in past years.
 
There are still a few things that aren't perfect:
 
Pixel has never started a significant translation with a full propellant 
load.  Several flights have been made at XPC '06 and in Oklahoma, but 
they were all with half propellant load for 90 second flights.  We could 
choose to burn off the first 90 seconds of propellant over the starting 
pad before doing the traverse, but that would have us in full slosh 
wiggle during the motions, and I want as much time as possible to dial 
in the landing on the lunar surface so we don't land on a rock or in a 
crater.
 
Positional control gets marginal on Pixel near the end of a three minute 
burn, which is another reason I would prefer to be sitting right over my 
landing spot, rather than moving towards it in the last part of the flight.
 
Balance and trim issues are still a concern with Pixel, we had one 180 
second flight that ended with the residual propellants unbalanced enough 
that the engine started sucking some helium.  We can control this with 
manual trim if we stay on top of it.
 
The flight computer box we have on Pixel isn't quite as good as the one 
on the module.  The main battery drains faster, and the gyros drift a 
bit more.  If we had more time, we would have tested swapping the boxes 
around to make sure they are as interchangeable as we think they are.  
As it is, we are going to stick with what we have tested unless forced 
to switch.
 
We had one communication upset post-flight with Pixel.  It seems very 
coincidental that the video receiving media stack was unplugged just 
about at the time of the upset, so we are not going to do that in the 
future.
 
We had some odd problems with initial fuel valve movement on both the 
Mod and Pixel that caused some no-lights.  We replaced an actuator and 
it seems to have gone away, but we don't understand the root cause.  I 
wouldn't be stunned if we experience a no-light on one of our attempts, 
but hopefully just recycling and trying again will fix it.
 
The lunar surface may yet trip us up for level 2.  In testing trim 
issues for pixel, relatively minor level changes can make drastic 
differences in propellant balance, and cause significant problems.
 
There are always worries about transporting everything long distances 
over the road.
 
I think we have a decent chance of taking both prizes on our first try, 
but we have a backup engine for each vehicle and lots of spare parts if 
we need to fix anything. 
 
We are a bit irritated that TrueZero is being allowed to fly their 
vehicle in event slots without ever having demonstrated a 90 second 
hover, let alone an untethered traverse like we were required to for 
each of our vehicles.  We don't think they have a chance of winning, but 
they certainly have a chance of making a big mess on the pads and 
possibly getting the rest of the event canceled.  I think it will be 
great fun to watch Unreasonable and TrueZero compete for the second 
prize on level one, and encouraging TrueZero to wreck their vehicle 
isn't going to help that.
 
John Carmack
 
 
 

 

The Flights

 

It was 38 degrees Fahrenheit when we got ready for the 7:30 AM flight window.  This was something to be a bit concerned with, because being uncomfortably cold can make normally practiced actions much less reliable.  It was probably also colder than any other time we have flown one of the vehicles.  Various event administrative issues delayed the start of our attempt.  It was 25 minutes into our window when we finally got to drive across the starting line.

 

We had an igniter abort on our first start attempt, but it started fine on the second try, and we had a nominal flight up and over.  We have done this quite a few times now, at XPC ’06, XPC ’07, and two separate trips to the Oklahoma Spaceport for private tests.  A stat I like to mention is that we have more flights under experimental permit than the rest of the industry combined.  The modules really do fly wonderfully; they look like they are just hanging from a string.  Several people have commented on the fact that they often slowly roll up to 45 degrees or so, but that is by design to avoid using much roll control gas.  We can fly with them rotating 360 degrees, but we do have to keep them from building up enough rotational velocity to exceed the gimbal speeds or pull propellant away from the inlets.  As it is, we often only have three or four roll thruster pulses in a 90 second flight.

 

The flight profile that I have been using involves descending from 50 meters and stopping initially at 10 meters to see where we are in relation to the pad center.  This time, when I stopped the descent at 10 meters, the rocket kept dropping, going all the way up to full throttle as it wound up touching the pad before coming back up to the height it wanted to be at.  The touchdown was only at a few meters a second, and the vehicle was hovering fine back in the air, but that disqualified the flight, so I set it back down on the pad for de-tanking after only seventy seconds or so.  The reason for this is that AST’s hazard range calculation had forced us to reduce the operating pressure from our desired 300 psi to 235 psi, based on how far the vehicle could go in theory if everything went wrong.  We decided that for future flights I would bring it down from 50 meters in “baby steps”, not letting it get up to the programmed 5 m/s descent rate that the normal profile would have.  That wouldn’t leave much of any time for manual adjustments towards pad center, but it should keep us from hitting the ground prematurely again.

 

After looking at the time, we decided to go ahead and try for two more good flights inside the current window, rather than waiting for the next window.  We hustled through our checklist, and were ready for the second flight in very good time.  We again had an initial igniter abort, but it lit fine on the second try, and the flight went fine.  I brought it down slowly, and we touched down with two feet of the pad center, well after the 90 second required time.

 

We started running through the checklist for the winning return flight, but just after we started loading lox we were told that the airport flight window was now closed.  We had almost an hour left in our contest window.  That sucked.  Bad.  We were less than ten minutes away from flight.  If the organizers had had their act together and we had gotten across the starting line at the scheduled time, we would have been fine.  If the airport had been closed for even the duration of the originally scheduled window (the airport was only closed for 90 minutes of the 150 minute window, assuming that the first and last half hour would be used for setup / teardown, not actual flights), we would have been fine.  Part of my mind was also thinking that if AST had let us run the pressure we wanted, we would have already won.

 

True Zer0 got to take the next flight window.  It was actually the first time I had seen anyone else’s vehicle take off live, which was fun.  After a nerve wracking wobble shortly after liftoff, they got it together and went up to 50 meters before tilting over and plummeting to the ground to make a big cloud of peroxide spray.  This was one of my significant fears – the peroxide could easily start a lot of brush fires, possibly even spontaneously an hour or two after the crash, and either fires or very muddy pads could keep us from getting our next shot in.  It turned out to not be a problem, the vehicle went down in the opposite direction from the destination pad, so all the fire fighting / diluting water didn’t really cause us any difficulty.

 

We pleaded with AST to allow us to run a little bit higher pressure on the mod for the next flight to prevent another possible ground contact, and after having Neil and someone back in Washington run a bunch of simulations, they allowed us 30 psi more pressure.

 

With the only other team out of it, the judges decided to treat the airport closure interruption like a “weather event”, and they allowed us the option of restarting the clock right where we were.  This wasn’t a completely clear cut decision for us, since it would be the third flight inside the contest window, with less time to recover if something went wrong.  We tried to lobby for the full 2.5 hour window to make flights, so if we messed up the first “continuation flight”, we could still try to make two more good flights inside the window, but we weren’t too surprised to find that rejected.  We decided to take the offer of one more try inside the remaining time, since we would still have two or three windows on Saturday to fly if necessary.

 

There was a little bit of drama with the flight.  We had the now familiar initial igniter abort (it still isn’t exactly clear why that happened in New Mexico, but never in Texas – I still need to examine the detail log data), but on the recycle we had a main chamber combustion abort, and we knew exactly what that meant – the slow actuator movement that we had seen during testing was back.  We tried a third time, and it was again a slow start, but it just barely made it in under the cutoff, and we lifted off.  The flight was again perfect.  I still babied it down from altitude, and got within two feed of the center again.  We de-tanked and headed back to the starting line for the official time.  I was actually in a bit of a panic as we were heading back, because I didn’t see the flight telemetry log where it was supposed to be.  When the accuracy judge approached to see the data, I had to tell him to wait until we got back to the starting line, because I was pulling the high frequency data from the vehicle flight computer.  That came over fine, and we were will within all the parameters.  We had actually overshot the stop altitude by a fair amount with the increased pressure.  Usually I stop commanding up at 50 meters, it peaks at around 58, then settles around 55.  This time it peaked at 68 meters, so it looked like it dropped a lot more, but it was still 55 meters for the transit.

 

We had a half hour remaining when we crossed the line, we might even be able to manage four flights inside the window if we had been going at max speed for all of them.

 

While this was still “the little one”, everyone involved was thrilled with the victory.  This was the second X-Prize to be awarded, and the largest Centennial Challenge award (the other award being the Astronaut Glove Challenge).  NASA, Northrop Grumman, the X-Prize foundation, the state of New Mexico, and the FAA/AST people all seemed extremely pleased and excited. 

 

After all the photos and interviews, we were asked where we wanted to go for the victory celebration.  We still had to prep Pixel for flight the next day, and get to bed early to satisfy the official crew rest requirements in our permit (I scoffed at that originally, but it is darned useful to have around to prevent show organizers from trying to schedule 6:00 AM team meetings), so I said we were probably just going to go back to the Ramada where we were staying.  After we had an opportunity to shower off the gritty accumulation of sunscreen, champagne, and New Mexico dessert dust, everyone from the event showed up at the hotel, and they had a stack of pizzas delivered.  Perfect.

 

It was a little bit warmer the next morning for the Pixel flights, and we got across the starting line right on time.  Everything went fine, including the initial ignition attempt (Pixel operates at 425 psi tank pressure, and the igniter always works better at higher pressure), but when I throttled up for liftoff, I got an immediate tilt abort.  I couldn’t see the liftoff from my location, but I heard that the vehicle had flipped over on its side.  Everything had shut down, nothing was leaking, and I still had telemetry, so we went about figuring out how to de-tank it safely.  Our first thought was that we had a huge balance problem, that somehow the propellant was mostly in one set of tanks instead of evenly distributed, as could happen if one of the vents hadn’t been all the way open during loading.  It turned out that the nozzle had burned through during throttle up, forcing the gimbal to the side, which flipped the vehicle over.  Looking at the high frequency flight data made it obvious what had happened – the ignition sequence was fine, but when it was commanded to move from the 45% idling level to full throttle for liftoff, the fuel valve moved slowly, just like with the ignition problems, resulting in a very lean burn with less film cooling than expected, which gave a burn through in a half second or so.

 

There was a bent pipe on the vehicle, but we had a spare engine, and all the necessary parts to have the vehicle ready for another try in the afternoon, but when we looked at it rationally, we decided that it wasn’t a very high probability of success, and it would be better to live to fly another day.  We only discovered the actuator drive problem the week before the event, and we clearly don’t have a handle on it.  The Pixel flight was a good data point for us, showing that it can clearly happen at partial throttles, rather than just at initial throttle up, reducing the chance that it might be anything related to the valve actuator limit switches.  We saw it on the third module flight, and we saw it on the first Pixel flight attempt.  I considered making a software change to detect valve divergence and stop throttling the other one up to prevent another burn through, but that wouldn’t keep it from smacking into the ground if it can’t throttle up for landing, and AST would require us to run all of our vehicle safety regression tests if I touched the software, which would make the afternoon window a stretch.  It seems unlikely that we would make two more Pixel flights without (Although we did three in a row in Texas before we left.  Sigh.) it impacting us in some way.  Given that we aren’t exactly 100% confident in pulling it off due to balance / trim issues in any case, it seemed a long shot.

 

Saturday just turned out to be another day of testing for us, we collected some data that we need, and we should be able to get a real fix made soon.  From some discussions at the event, It sounds like it may be possible to make another try for the level 2 prize sometime earlier than next October this time.

 

In addition to all of the hard working team members and their supportive families, I would like to thank our suppliers.  Some of them don’t have any clue that they are in the rocket business, but most of them have been actively supportive.

 

Consumables:

http://www.tex-aircryogenics.com/

http://www.balloonbasics.com/ (Discount Helium of Dallas)

http://www.brenntag.com

 

Tools:

http://www.haascnc.com/

 

Parts:

http://www.mcmaster.com/

http://www.amsind.com/

http://www.ultramotion.com/

http://www.kzco.com/

 

Electronics:

http://www.diamondsystems.com/

http://www.ampro.com/

http://www.xbow.com/

 

 

The Other Teams

 

It was good to meet the True Zer0 guys at the show, and we really did wish them the best, but their flight went exactly as I considered the “most likely” outcome.  I still don’t really understand the motivation to go and fly at the event when they knew that they really couldn’t win.  Their longest hover to date was 70 seconds, and they only estimated another six or seven seconds of propellant remaining.  They changed up from 85% to 90% peroxide, but that wouldn’t have given enough to make it even in theory, and progressive stripping of their catalyst pack was probably going to make a second flight leg impossible even if they managed to drop to the ground at 90.1 seconds on the first leg.

 

The best case for them would have been to gently sputter to the ground on the second pad at 80 seconds or so of flight time.  That would have been a triumph, and probably would have justified the five figure sum of money spent on insurance to fly at the event.  However, that just wasn’t a terribly likely outcome.

 

There were several things about their vehicle that I find worth commenting on:

 

They got the tank hemispheres from AMS, the same place we and most of the other teams have been using.  Their anodizing shop didn’t feel comfortable trying to anodize the entire thing (Paul Breed did manage that with the Unreasonable Rocket vehicle), but they did dip them in their cleaning tank, which left a very nice finish on the tank.  We use an aluminum cleaning solution on the weld area, but dunking the entire thing is probably a good idea.

 

They have a clever arrangement of rod ends instead of a u-joint for a gimbal.  This allows them to run the peroxide plumbing straight down from the tank and into the valve and engine.  If we ever do another gimbaled module design, I will seriously consider building something like this for two propellant lines.

 

They used the 20 kg payload as a mass damper for their flight electronics.  I was rather surprised that MEMS gyros were good enough for even the 70 second hover they have demonstrated, and it turns out that they did have vibration problems earlier, but putting everything directly on top of the payload mass, then isolating that from the vehicle worked well.

 

Their tank didn’t break when dropped from 150’ in the air.  Everything attached to it did, but that is still a useful data point.

 

On the negative side, I was very surprised that they were loading tens of gallons of HTP through a funnel.  Vacuum loading or a peristaltic pump is really the way to go with peroxide.

 

I hope they decide to get on the aRocket mailing list with the rest of us – they epitomize the spirit, and they have things to contribute.

 

On the broader field of competition, it is very clear that peroxide vehicles are way, way easier than biprop vehicles.  TrueZer0, Unreasonable Rocket, and SpeedUp all got a vehicle up in the air and flying to a degree, while none of the biprop teams outside Armadillo had an LLC vehicle leave the ground.  Masten left the ground briefly with their XA0.1, but that was never going to be an LLC class vehicle.

 

Most teams aren’t giving themselves enough margin.  TrueZer0 and Unreasonable both designed vehicles that would just barely make it, and when reality set in, they were both a bit short.  It would have hardly cost them anything to use a tank 6” wider in diameter.  Speed-Up had an adequate tank size, but undersized the engine.  It is true that crossing the line from man-portable to crane-portable is significant, but any level one vehicle should have been aiming for 120 seconds, and settling for 95.

 

The Valve Problem

 

There has already been some armchair quarterbacking going on, so here are some more explicit details on the problem:

 

We noticed the problem the week before when analyzing some failures of the engine to start, even though the igniter was operating properly.  You couldn’t see much on the 10hz telemetry data, but with the 200hz on-board data it was clear that when the valves were commanded to move, they sometimes responded sluggishly for some period before returning to full speed.  It was almost always the fuel valve, but it did happen once on the lox valve.  It happened at least occasionally with both electronics boxes, and on both vehicles, and after replacing the fuel valve actuator.  It certainly appeared to be a problem with the design of our drive electronics.  Why it only started being a problem now is a mystery.  One possibility was that we had originally designed the boards for 12v lead-acid batteries, but had switched to 15v li-po batteries for the actuators, and some components may have been damaged over three years of use.

 

Russ had originally designed our electronics boards with current sensors on each drive channel, but when I first looked at the data years ago, they didn’t seem to be all that well calibrated in an absolute sense from channel to channel, and I didn’t add display graphs for them.  I did still store them out, though.  When we started working on this problem, I finally added some graphs of all the current traces, and we got a lot more insight into our system.  Even though the data wasn’t good enough for me to return a really valid amps value for each channel, it was great for looking at the behavior of a given channel over time, and for rough comparisons between channels with, say, different types of solenoids.

 

A normal valve opening current trace shoots up to a peak at the start as it starts the motor spinning and overcoming valve stiction, then tapers down to a low constant level if the valve is moving at full speed.  All of our pulse width modulation of the various motors when they are hunting for specific values instead of moving at maximum speed is also perfectly evident in the current traces.  What was happening in our problem cases was that the initial current spike would happen, but the current then drops to essentially zero for some time before coming back up.  The control bit is solidly on, but almost no current is coming out.  If the initial spike is long enough, the valve just coasts opens slowly for a little while, with a distinct inflection point in the opening rate.  If the initial spike is too short, the valve barely moves at all for a couple hundred milliseconds, before going up at normal speed.

 

It definitely isn’t a valve stiction problem, because a stuck valve will draw more current than a moving one, not less.

 

The valve channels are protected by our master cutoff watchdog controller, which causes them to be forced off by relays if the main computer stops signaling it with a twiddle bit, but all the valve relays are controlled by a single transistor, and during our fuel valve stalls the lox valve is still driving current properly.  Some kind of bad cutout relay is still a possibility.

 

The valve actuators have some active components inside them, including limit switches and some protection circuitry, so it might be something there.  If it only happened right around fully closed I would be very suspicious of the limit switches, but the effect does show up as the valve is opening, and in our level two flight, even in the mid range.  We may yet take the leads straight out from the motors, bypassing all the other electronics for some tests.  That would disable some of our safety systems, which require that driving the valve closed will shut things off, rather than allowing the valve to spin 360 degrees, but we could perform some tests that we.

 

We suspected that total system current draw in some way could be an issue.  The fact that it almost always happened on the fuel valve, which started moving 100 msec after the lox valve, seemed suspicious.  We tried all sorts of changes to the solenoids and gimbal movement during startup, and some seemed to fix things, but in hindsight it appears that it may be just random.

 

I went back and looked at a lot of old data, and we could see some signs of sluggish valve movement in older runs, but they hadn’t been slow enough to trigger aborts.  The fact that we tightened up the timing of the chamber pressure check to reduce the time that the igniter runs probably brought it to light more obviously.

 

The lousy part about this is that we have never seen the effect happen when we are just testing actuators.  Even when doing a “fake engine” test, where the computer just ignores all the pressure interlocks and runs the actuators as if it were flying.  We finally did get it to seem reproducible when we pressurized the vehicle to operating pressure with nitrogen, and then tried to operate it.  Russ sat up on top of Pixel with a scope, looking at different traces on the electronics board while I ran things, and couldn’t find anything wrong.  When we replaced the fuel valve actuator, the problem seemed to go away, and we left it at that.  The next three tests didn’t show the problem, but then it bit us on the flight at the event.

 

We are going to try and set up a high pressure bench test for this, since it does seem somehow influenced by the pressure behind the valve, but I will be surprised if it occurs outside the complete system.  We may be stuck repeatedly testing the complete vehicle in place at high pressures.  Once we have it reliably reproduced, we can check everything on the driver circuits, try running it from different channels not protected by the master cutoff, and try bypassing all the control circuits in the actuators.  When the gimbal motor drivers were PWM’ing like mad, Russ did see some voltage transients that he would like to fix on the board, but we still saw occurrences of the problem during startup with the gimbal actuators locked in brake mode, so that certainly isn’t the only issue.

 

This is the absolute top priority to fix, and everything else, including the RRL work and NASA work, is frozen until we have it resolved.  I would be surprised if we don’t have it nailed down by the end of the week.

 

 

Manned Suborbital Vehicle Development

 

http://www.spaceref.com/news/viewpr.html?pid=26813

 

I thought that making a public announcement with the governor of New Mexico at the Lunar Lander Challenge about a new venture between Rocket Racing Inc, Armadillo, and the state of New Mexico while we were flying an experimental flight was a bad idea – too many things could go embarrassingly wrong.  However, it turned out perfect, with the governor watching as we made the winning flight.

 

All the terms aren’t final, but this is a big deal.  We’re going to space, sooner rather than later.  Some of you can come, too.

 

 





 






 
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