Stellar Jay

The Mascot Photo

The Goal

Simply stated, the plan is to make an attempt at an Open Class altitude record.  But not just any record, the highest record that can be set by a Level 1 Certified rocketeer.  That means “J” Motor Class, 1280NS maximum impulse, and a Two-Stage design.  In the end, experience is the ultimate goal.  But the experience will be that of attempting to achieve a lofty goal.

 

The Design Choice

This design started the way many of my projects do now days, playing the “What If…” game with Rocksim.  It wasn’t long before I loaded the file for my PML Cirrus Dart as a starting point.  And much to my amazement after initially copying the parts to make it into two stages, the results were very promising.  After a couple weeks of tweaking this & that, while researching the other thing, I settled on a basic plan that involved using the existing PML Cirrus Dart for the booster, and ordering another slightly customized kit and a few other odd parts from PML to provide the rest of the basic parts.

 

Many of the choices made for this design, like the booster, were made for reasons other than optimum performance.  I assumed going into this project that I would learn how to make a more perfect design than this one by the time I finished, so I decided that the original design would not be so limited that I wouldn’t want to fly it again if the primary goal was achieved, and that there would be some flexibility incorporated.  This affected two particular issues, both resulting in the sustainer having more length then absolutely required.  Other restrictions I placed on the design were that accelerometer based data recording electronics would do all deployment tasks.  This gave me the excuse I needed to justify buying a couple new flight computers.  On the other hand I already had a good staging timer, so I opted to use it.  Later research showed it to be a reasonable choice.

 

Altitude being the major goal of this bird, stage separation must occur well before sustainer ignition.  (In this rocket, simulations indicate the delay between staging and sustainer ignition can make as much a 3000 feet of difference in final altitude.)  Because of this, electronics responsible for upper stage ignition must reside in the sustainer.

 

The Flight Plan

o       A test flight will be first using an Aerotech I357 RMS in the booster to an Aerotech I154 RMS in the sustainer.

Flight Scheduled for 5-17-03 - Scrubbed by Weather

Rescheduled for 6-21-03             Flight Report

 

o       The primary target flight is to be an altitude record attempt with an Aerotech I435 RMS booster to an Aerotech I132 single use sustainer motor.

Flight Scheduled for 8-2-03  - Flight Report

 

 

o       The alternate primary target flight will be an altitude record attempt with an Aerotech I435 RMS booster to an Aerotech I284 RMS sustainer motor.  This flight will be made with the newly built replacement rocket incorporating lessons learned in the initial design & build process.  The new rocket designation is: Stellar Jay II.  Details of the design changes are found at this link.

Flight Scheduled for 9-26-03  - Flight Report

 

 

o       The secondary target flight is to be a speed run attempt at Mach 2 with an Aerotech I435 RMS booster to an Aerotech I435 RMS sustainer motor.  This flight will not be flown if the previous flight must be pushed back or if recycle is hindered by time, weather, or damage.

Flight Scheduled for 9-27-03 – Canceled!

 

 

Electronics list

Device

Usage

Comments

G-Wiz MC

1) Stage Separation

2) Booster Apogee Deployment

3) Backup Low Alt Deployment

4) Booster Flight Data Recording

The G-Wiz MC with its 3 pyro channels is uniquely qualified for this task. J

PML Accufire

Sustainer Motor Ignition and Delay Timing of Motor Ignition

A Solid Staging Timer.  J (A G-Wiz Partners product)

Rocket Hunter RHT-35

Sustainer Tracking Transmitter

A nice fit in this project. J

R-DAS Compact

1) Sustainer Apogee Deployment

2) Sustainer Flight Data Recording

3) Backup Low Alt Deployment

Very compact! J (I really wanted this) None of the add-ons fit 38mm airframes.  L

 

 From the Inter-Stage Coupler to the Nose Cone

With a minimum diameter two stage rocket the inter-stage coupler presents an interesting challenge.  I opted to use the sustainer motor case as the coupler between the sustainer and the booster.  While easily workable this added to the challenges in other areas.  One of these is that the aft closure of the RMS case has a larger outside diameter than the airframe inside diameter.  Obvious, but still an issue.  And the obvious answer was to turn down the closure to the same diameter as the case.

 

The turned down aft closure, still not anodized, is seen next to the staging piston, and the staging charge base, positioned relative to each other in the order they will reside in the rocket.

Right: One of the disposable staging pistons.  I made several of these as I anticipate loosing them during each flight.  This one is sized to fit the Aerotech RMS motor configuration.  A different size is used for the single-use motors such as the I132 (the best choice for the altitude record assault).

Left & Above Left: The staging charge base has a small hole for the staging charge wire.  The bigger hole is for an alignment pin.  In the center, is the threaded end of a screw that is used to remove this part from the airframe.  I made a tool to perform this removal.  It is just a nut attached with epoxy to the end of a dowel.

Above Left: In the staging charge base you can see there is enough depth to accept a small stage separating charge.  Above Right: You can see the head of the extraction bolt in the bottom of the charge base.

 

  Right: The charge base is installed in the inter-stage section of the airframe.  Here you can see the alignment pin protruding through the hole in the charge base.

Here are views inside the inter-stage section of the airframe, both showing the bulkhead that the staging charge base rests on.  Left: The forward side of the bulkhead, alignment pin, and wire trough for the e-match leads. 

Right: The aft side of the bulkhead.  This inter-stage section, white with the mascot picture on it, is shown below with the G-Wiz.

Right: The major parts of the electronics bay / Inter-Stage coupling section of the booster airframe, and the electronics module that rides inside it.  The electronics package is a G-Wiz MC that provides a staging pyro channel.  I use it to initiate stage separation instead of motor ignition.  It also fires the apogee recovery charge for the booster.  The low altitude charge is only used as backup for the apogee charge and is disabled if the deployment is successful.

 

Here, they are laid out in the assembly orientation.  The batteries reside in the same unit with the G-wiz, and a DPST switch on top is accessible through a vent hole for power on/off once fully assembled.  The switch is positioned such that the toggle is on the vertical spin axis, and the internal contacts will be forced together should rotational G-force develop.

 

Right: Two views of the motor spacer.  The sustainer was built to handle up to a 38/720 (J350) motor case.  But since the primary goal is to fly two-stages with a total impulse rating under 1280 Newton-seconds, as a Level 1 certified flyer, I must accommodate the 38/600 RMS case as well as the optimum motor selection, single-use I132.  I also made two additional spacers 1-7/8” long to accommodate shorter motors by stacking spacers.  Those are primarily for lower power tests.

 

This is the aft (left) and forward (right) ends of the motor case with the flat flex wire installed as will be done for flight.  Notice the orange regular wire (excess from a Daveyfire 28B), soldered to the forward end.  This wire extends forward in the rocket to attach to the staging timer.  The motor igniter, a Daveyfire 28F, will be cut to length and soldered as well at the aft end, at least, until the motor lights!  J

 

Here the forward end of the motor case has the spacer fitted on it, and the regular wire running through the middle.

 

The sustainer electronics consist of the R-DAS Compact shown in the mounts, and connected to the battery that resides in the semi-hollowed out urethane nosecone, retained with Velcro.

 

A close up of the power switch made from a stainless steel Philips head screw accessible from outside the airframe through the atmospheric vent hole.  The nuts on either side of the vertical bulkhead are soldered to the power circuit.  Turning the screw in to contact with the 2nd nut closes the circuit.  The 2nd nut has a nylon insert to keep the screw from backing off due to vibration.

 

Two of the sustainer recovery charge base units.  I built three, but only one is used at a time.  Extras are for pre-prep and easier faster problem solving if something doesn’t check out at the last minute.  These have an extraction stud built in for removal, and are aligned by the bolt that holds them in place, and anchors the recovery piston strap.

 

This is the whole pile of stuff that makes up the sustainer.

 

 

Flight Reports

Flight #1 Test Flight: This flight was first scheduled for May 17, 03 at Tripoli Central CA’s Dairy Aire launch, but high winds & low clouds both days kept the Stellar Jay sealed snugly in her traveling case (a cardboard box).  So the flight was scrubbed and rescheduled for June 21, 03 at Aero-Pac’s MudRock launch at Black Rock NV.  Mother nature was more understanding this time.  And the flight went on as planned. 

 

The launch tower had been previously erected at the M pads for some EX launches on Friday, so I left it there.  Tony Alcocer manned the Walston receiver, while Steve Alcocer assisted me at the pad.  Steve adjusted the tower, I inserted the sustainer motor igniter (a freshly dipped Davey Fire 28F) into the I154, installed the staging piston, we slid it into place in the tower, coupling the rocket stages, and checked for binding in the tower.  I then inserted the I357 booster motor igniter (Igniterman), leaving the leads shorted for now.

 

First I powered up the R-DAS sustainer flight controller, and waited for the audible indication that it and its two deployment e-matches (Davey Fire 28Bs) had good status (single, not double beeps).  Then I powered up the G-Wiz MC booster flight controller, and again waited for the audible indication that it and its three e-matches (Davey Fire 28Bs) had good status (single, not double beeps).  Finally it was the staging timer’s turn, so I powered on the PML Accufire (a G-Wiz product) and waited for it to finish beeping out the staging delay setting 3-times, so it could then tell me the status of the staging igniter.  Again I’m looking for single beeps, not double beeps.  But for this flight, the staging delay was set for two seconds, so I was a little nervous waiting for it to quit beeping out double beeps (meaning 2-seconds), and start beeping single beeps to say the igniter status was good.  Right then the other rocketeer setting up a rocket started hitting the continuity tester 10 feet away.  And yes, you guessed right, it beeps!  So now I have 4 things beeping at me, but I was strangely calm and able to decipher one beeping device from all the others.  I would not have guessed that this scenario would not leave me in a twitching pile of spent nerves.  I connected the boosted motor igniter to the launch controller, tested continuity, and all systems were go!

 

Back at the spectator area, Tony had a good Walston signal, and the countdown commenced.  She left the pad with authority on a straight boost.  Burnout occurred about 300 feet so I had a clear view of the staging process, which was the real point of this flight.  Right on time booster burnout and stage separation happened.  2.5 seconds later the sustainer motor came up to pressure and powered the sustainer over the 11,000-foot mark on a tower of billowing black smoke.  We could not see the rocket once it the sustainer motor burned out because the air was hazy, but 26 seconds later we knew that it reached apogee and the ejection charge was effective because the Rocket Hunter tracking transmitter blasted a sudden increase in signal strength just as advertised.  5 minutes later the sustainer was down, 1.5 miles away in the same direction as the booster. 

 

Flight Data:

Here is the preflight simulation data from Rocksim:

 

Here is the G-Wiz (Booster) Flight Summary

 

 

Here is the R-DAS (Sustainer) Acceleration, Velocity and Altitude Graphs

Check out the Mach transitions in the altitude (blue) data around the 5-second mark.

 

 

Flight #2 Altitude Attempt #1: This flight was first scheduled to fly on an I435 booster and an I132 sustainer.  Late in the process I found a weight savings that changed the dynamics of the rocket and subsequently the optimum motor selection based on available motors.  Simulations were showing that flying on the I132 in both stages was the only configuration that would produce the possibility to exceed 20,000 feet.  This attractive target altitude was not attainable in previous simulations, or in current simulations using other motor selections even with the weight savings discoveries.

 

Weight savings were found in 3 places.  First a weight savings gained from sacrificing data recording capabilities in the booster flight computer.  This came in the form of replacing the G-Wiz MC with the smaller and lighter G-Wiz LC.  Second a small weight savings came from removing the redundant deployment charge in the booster.  The G-Wiz LC does not have the low altitude pyro channel to activate the backup charge, so this was an easy choice.  Third and lastly the 9-volt alkaline batteries weigh 1.66 oz.  I found 9-volt lithium batteries that weigh only 1.33 oz.  This amounts to 1.0 oz for the 3 batteries, 2 of which are in the sustainer.

 

The flight prep revealed the first flaw in my flight plan, which was that I did not fully mach up the rocket with ALL changes.  I diligently worked to retrofit the G-Wiz LC to verify the mounting and functionality.  Omission of the redundant recovery charge only required plugging the e-match access hole in the booster deployment piston.  What I failed to do though, was the obvious, test fitting the lithium batteries.  Two of the three would not fit in the battery holders.  They visually appear to be the same dimension as the alkaline batteries, but they are not!  The lithium batteries are much more square in the corners, resulting in a diagonal increase that precluded the retrofit in two of my custom mounting locations (one in the booster and one in the sustainer).  No detail is too small to test!  In the end I deem this issue insignificant to the outcome of the flight.

 

The flight resulted in total loss of the sustainer, while the booster and interstage coupler were recovered normally.  The flight left the 120” tower with an odd sound and without being closely observed or recorded due to an inadvertent dual launch when another rocket was the only intended launch.  All attention was on the other rocket until the odd sound was heard coming from the other end of the launch rack.  The odd sound may be indicative of launch tower difficulties, but it may also simply be normal sound from this launch tower.  The rocket did not fly straight up.  It was headed across the sky over the crowd when I first spotted it.  It appeared to be trying to go up, and did in fact gain altitude as it passed over head.  The flight direction was far from vertical, and the down-range direction was up wind.  The overwhelming evidence is that the wind was too strong, causing severe weathercocking.    The booster motor burned out and the staging charge separated the booster from the sustainer on queue.  The interstage ignition delay was far too long for the low speed and low trajectory.  The sustainer arced over and was pointed down when the staging timer ignited the sustainer motor.  I can only assume that the accelerometer based speed detection of the R-DAS was not designed to recognize apogee in this flight profile since the recovery system was not observed to function.  The sustainer was traveling at a very high rate of speed and still under power when it impacted the playa at a trajectory that appeared to be nearly straight down.  A rather large mushroom dust cloud punctuated the impact, estimated to be somewhere near 1.5 miles away.  The crater was not found, no debris was located, and it started raining while I was looking.  The booster was recovered in excellent condition.

 

The decision to fly was most likely the cause of the crash, given the wind conditions and the low initial thrust to weight ratio (5:1).  The direction of flight was consistent with severe weathercocking.  But supporting evidence was not available.  The noted sound may or may not be indicative of some sort of tower snag, but having no previous experience with this tower, there is no basis of experience to make any educated guess.

 

Flight Data:  None available.

 

The Rebuild, and the birth of:

Stellar Jay II

Building a version two was not in the original plan for this project (that’s not a new story though).  But since I crashed version one, and do not feel that I have achieved anything just yet, I decided to go ahead and build a second rocket and try again.  After all, I did learn some things such as patience and planning.  I didn’t like the weather at the first test launch date so I scrubbed that launch.  I flew at the next opportunity, proving the design & concepts were good.  I selected a tender motor package for the next flight, deviating from my plan.  Then I failed to heed my own advice about the conditions under which this motor combination was viable.  Knowing that it would be slow off the pad, I still chose to attempt to fly in windy conditions.  Bad choice.  So having learned that planning in advance is more effective then deciding at the launch, I went forward with the rebuild.  On arrival home I ordered more parts and electronics. Following is a rundown of the changes I planned for the version two rebuild:

Component

Choice

Reason

Improvement

Staging Timer

PerfectFlite MT3G

PML Accufire Timer Destroyed

Weight Savings, and Space Savings

 

Sustainer Airframe

Built New from Scratch

Destroyed

*Reduced 7-1/8” and 7.1oz.

 

Sustainer Batteries

9-volt Lithium Ion

Alkaline Battery Weight

Save .3 oz. per battery, .6oz total

 

Booster Airframe

Built New from Scratch

Incorporate Design Improvement Learned

*Reduced 12-1/4” and 9.1 oz.

 

Booster Electronics

G-Wiz LC

G-Wiz MC is Overkill

Weight & Space Savings

 

Switches

Scratch Made Screw Switches

Incorporate Design Improvement Learned

Positive Gee-proof Simplicity

 

 

*A miserly paint job and reduced use of metal D-rings and eyebolts contributed part of these weight savings, while length reductions accounted for the majority.  The length reductions came from two primary sources: Abandoning accommodations for a potential J350 flight in the sustainer or room for an I132. ; And reducing space accommodations for larger internal components that were replaced with smaller ones.

Staging Timer:

The PML Accufire staging timer, having been destroyed in the crash was no longer “in my box” so I was faced with both the luxury and expense of having to select a timer to purchase.  Since I had decided to make space and weight higher priorities than features and rocket-to-rocket versatility, I selected the PerfectFlite Mini timer.  It’s very small and very light, and uses an audio status indicator.  I did not want to deal with staging from a break-wire so I got the G-switch activation version (MT3G).  This is not a staging timer that starts the timer at burn out.  It detects launch, so the time increment chosen must include booster burn time.  While this timer is small and light, it is not easy to set the time delay exactly because you have to hold a switch for the duration you want, then try again if you get it wrong.  When setting to one tenth of a second, it can take many tries.  An issue strictly of preference that I don’t particularly enjoy, is that once the power on check and timer setting verification is complete, it emits a continuous tone rather than a periodic beep for a continuity check.  It just feels like unnecessary power consumption.

 

Sustainer Airframe:

The replacement sustainer airframe was built using the same nose cone, electronics bay, and ejection design in the upper airframe, which was shortened by an inch from the aft end.  The lower airframe bore the brunt of the changes.  I decided to commit to the Aerotech 38/600 RMS motor.  This allowed for significant length reduction.  A thrust ring (a centering ring that allows the delay charge cavity to pass through the center), was positioned at the forward shoulder of the RMS case.  Rather than closing the forward end of the coupler, requiring aft insertion of the staging timer and tracking transmitter, I left the coupler open ended.  Inside the coupler I fashioned mountings for the timer and battery leaving room to pass the shock cord through, and stow several loops of shock cord for flight.  The shock cord, no longer having the coupler bulkhead plate for mounting, was attached to the forward closure of the RMS case.  The tracking timer attaches to the shock cord as recommended by Joe at Rocket Hunter, and can be powered up and attached much quicker than my previous method.  There is much less preflight prep hassle using this timer and transmitter configuration.  I am also much more comfortable with motor retention because the shock cord is attached to the motor.

 

Sustainer Batteries:

Once I found these lithium-ion 9-volt batteries, use of them was an easy decision.  They weigh one third of an ounce less per battery.  The sustainer uses two of them, for two thirds of an ounce of weight savings.  They are not however a direct replacement!  The batteries are slightly larger and mounting concerns must be addressed when space is at a premium as it is in this project.  These batteries are also significantly more expensive than alkaline batteries.

 

Booster Airframe:

The original booster was not harmed in the crash.  However it was an adaptation of an existing PML Cirrus Dart airframe.  I built a new custom design that splits in the middle with a forward mounted piston, ejecting aft-ward.  All excess length was removed.  At the forward end a coupler is mounted that fully contains the G-Wiz LC and it’s battery.  A lithium ion battery simply would not fit without adding length so the alkaline battery is used here.  The G-Wiz LC does not use a beeper, just LEDs so I installed clear windows through the airframe directly in front of the LEDs, which are located very close to the windows.

 

Booster Electronics:

As mentioned above, I used the G-Wiz LC in the booster instead of the G-Wiz MC.  The LC is lighter, shorter and has a smaller cross-sectional profile.  The weight savings is for obvious reasons.  The length savings contributes to weight savings by allowing the airframe to be shorter.  The cross-sectional profile allows for additional length reductions (and associated weight savings) in that it allows the battery and electronics to share space in the airframe.  The LC does provide the required functionality for booster electronics (motor burn-out and apogee deployment charge pyro channels).  What the LC does not have that the MC does have are: Data Recording, which is unnecessary, but interesting; Low altitude Pyro Channel and associated barometric sensor, which is also unnecessary but was previously used as a backup deployment charge for the single chute; Audible status indicator (beeper), a feature that I like but I was easily able to work around this with the LED windows.

 

Switches:

In the first build I made a screw switch for the R-DAS by soldering wires to nuts that were mounted on opposite sides of a glass reinforced balsa structural extension on the aft R-DAS mount.  A Philips head screw threaded into one nut aligned directly with the barometric pressure vent hole, was quite easy to operate.  Since this worked so well and was so easy to use, I opted to incorporate this concept for all three externally operated power switches in the new design.  As it happened they were all three located in places that coincidentally required vents.

 

Flight #3 Altitude Attempt #2: This flight was flown at XPRS, Aero-Pac’s biggest launch of the year.  And this year the ARLISS project was moved to XPRS as well, so there was a very large crowd in attendance for the absolutely perfect weather at Black Rock (the best place on Earth).  The flight was a raging success in that it flew very well, achieved an extreme altitude (18,408 feet), and accomplished my primary goal of flying a level one rocket higher than the (then applicable) current “J” class open altitude record of 16,716 feet.  So I am quite satisfied. 

 

After starting this project and before the flying season, Tripoli restructured the altitude records creating separate classes for multi-motor rockets from single motor rockets, leaving me to compete for an unoccupied record.  So technically I could simply have applied for the record with the test flight number of 11K’, but that would not accomplish any of what I was trying to do.  And flying for Aero-Pac, I would no doubt get sent to the far end of the flight line for posting a cheesy number on a record application form.  But the fact remains that I flew a good flight, posted a respectable number, and claimed the record as well. 

 

While inside I hoped for a higher altitude number, on the order of 20K’, it is probably just out of reach without at least one full 640ns slow burn motor.  The motor combination used was an I435 booster staging to an I284 providing 1110.6ns total impulse.  This represents a 74% J motor, and yielded a flight of 18,408 feet, max speed of 1,207mph (1,771 fps), and acceleration on the order of 47.5 and 50 Gees at peak booster & sustainer motor burns respectively.  Not bad for leaving nearly 170ns on the prep table.  (Hmmm, maybe I should add a full G 3rd stage!)

 

This excellent launch photo was taken by: Steve Pope

Here is the R-DAS (Sustainer) Acceleration, Velocity and Altitude Graphs

Check out the Mach transitions in the altitude (blue) data around the 9 & 13 second marks.

 

The Rocksim Flight Simulation Graph predicted a max altitude of 19,121 feet, 34 & 44 Gees, and 1253 mph.