Icarus I: a 38mm minimum diameter build

I have posted on here a few times before about an independent student project I am working on, a 38mm minimum diameter experimental rocket named Icarus I.

I have recruited a few local rocket enthusiasts, with a wide range of backgrounds, into a small team to help with this project. We are calling ourselves "Team Icarus", and I thought we'd document the build here on TRF. We are open to suggestions and criticism, so if you see anything we could be doing better or more efficiently let us know.

The design as it stands right now has the most aerodynamic fin configuration we can manage while maintaining healthy margins for stability. Several of the team members have experience with very tightly packed fuselages on R/C sailplanes, so we are hoping to keep things pretty compact. The current configuration sims to 13,686', with a top speed of Mach 1.58 in RASAero.

To find the minimum fin size, we used RASAero to find the configuration with the lowest drag that kept the CP in front of the CG at the maximum design parameters. The maximum design angle of attack, 15 degrees, would be experienced while leaving the rail on a day with ~25 mph winds. The barrowman stability method is known to be quite reliable at this speed, so the fins were sized to keep the CP about 1/4" behind the CG at this angle. To verify stability at speed, we ensured that the 0-4 degree CP remained at least one and a half calibers behind the CG up to mach 2.5. The final result left the CP 1.98 calibers behind the CG at zero degrees AoA, which was about what you would expect.

We ended up settling on a smaller tip chord than the clipped delta that I often see cited as being the lowest drag option. When I started running iterations on different fin designs, I originally kept the root-to-tip ratio around 2 to reduce induced drag losses. However, the increased sweep and aspect ratio from the reduced tip size more than makes up for any induced drag losses due to the extreme taper ratio. The trailing edge is swept back as much as we dared without fearing increased flutter or broken fins.

The body material of choice for this rocket is Blue Tube, as it offers a nice balance between performance and budget. We are looking to build some molds for custom carbon parts for future rockets, but want to keep construction more simple until we have more experience with rockets in this performance class. The fins will either be cut from carbon sheet or canvas phenolic (we are undecided), and glassed on. They will be coupled with a FWFG 4:1 ogive nosecone. A Von Karman or conical nosecone would be the more aerodynamic choice, but some of the team members had a strong aesthetic preference for the classic profile of the ogive. The simmed altitude difference was small, so we went with the ogive.

Given the launch altitude of this rocket, dual deploy and electronic tracking are pretty much mandatory. Both will be first-time experiences for us.

Greg from BigRedBee has generously agreed to donate a BeeLine GPS for use on this project, which will be a huge asset. We owe him a big thanks. I just passed my Ham Radio Technician test yesterday, so we can utilize the 70 cm unit. We plan to use a small handheld transceiver in conjunction with APRSDroid for the groundstation.

We are seeking an accelerometer-based altimeter unit, but will likely have to fall back on a simple stratologger for deployment. For main recovery, we have a 52" ripstop parachute, and a mylar streamer for the "drogue". What are everyone's thoughts on using the streamer vs simply going drogueless?

On the subject of the powerplant, this rocket will feature a research motor using commercially-produced 38/740 snap ring hardware with a graphite nozzle. The grain configuration of this motor was designed in tandem with the rocket itself to optimize the motor-rocket system. This process gives a little extra performance, but more importantly for me as a student it offers a valuable design exercise. The current configuration uses five BATES grains and is projected to produce an average thrust of 517 N.

Thanks for looking, we should be updating soon as we begin the actual build.

EDIT: This design is still somewhat fluid. At the time of this edit, the team has seen further growth in its member base, and the most updated fin and body design can be seen on post 16

I'd recommend going with a smaller chute. With a 52" chute you definitely will have to take a quad to chase it out there. I'd tune down to 24".

That said, it will allow you to cut down the upper airframe. You want to eliminate a longer airframe as this will create the chance of buckle failure at an angle of attack.

Hope this helps, I'll be subscribed.

Cool project!

A couple things I learned from doing a 38mm MD on a similar motor (search I540 to mach 2):

1. Do NOT trust RASaero at all for stability. Download Openrocket (free), and design your fins with that to have >1 cal stability throughout the flight. You can do this by plotting stability vs. time for the simulation flight.

2. On the subject of fins, sometimes it pays to design your rocket with bigger fins. On a recent 29mm MD build, I made the fins quite a bit taller than absolutely necessary. On its flight, the large fins payed off with a dead straight and vertical flight, which overall netted me similar altitude than what was lost by drag vs a design with smaller fins that could have weather cocked 5-10 degrees.

3. I would say to go drogueless. Unless your payload section is going to weigh a ton, there is really no need for a drogue. It will stay destabilized and fall at a rate that is plenty safe for the deployment of your main parachute. For really high flights you want to minimize drift as much as possible, and going drogueless will do just that.

4. You can definitely use a smaller main parachute. If your under 4 lbs at burn out, a 24" would be fine. A thin-mill chute from topflight works great and packs into ~1.5" of 38mm tubing. Your rocket is going to be quite tough, and doesn't need an ultra-gentle landing.

5. For wiring the electronics: a word of warning, high G flights (>30g) have an uncanny ability to cause electronics failures. Leave a few wires hanging loose, or a battery only tied down with a couple small zip ties, and the sustained g forces can just rip them out. Make sure everything is very securely tied down, things like JST connectors (I 5 min epoxy these closed before a >100g flight), wires running to terminals, ejection lighters, etc. The last thing you want is an electonics failure, it really stinks!

If you want to really go for altitude, get rid of the payload tube, and use your electonics bay as your nosecones coupler (the FWFG ones are removable), putting the drogue in its regular position and the main parachute inside the nosecone. Doing that will get rid of a ton of drag.

Have you decided upon your method for launching this rocket? Since your goal is altitude, you probably don't want to use rail buttons. A launch tower can work, as could 3-D printed fly-away rail guides (searching the forum you should be able to find the user who sells them)

All in all a very cool project, 38 MD's are awesome - tons of altitude and speed for their given impulse.

raptor22

A new version of RASAero will be released soon where the supersonic CP will move forward 1 caliber, especially for short fin span rockets. You can take the current RASAero supersonic CP predictions for both zero degrees angle of attack and 0-4 degrees angle of attack, and shift both curves forward 1 caliber, and they will be close to the new predictions.

That said, with any CP prediction I would have 2.0 calibers of stability margin at all Mach numbers. So with the current RASAero, once you shift the supersonic CP curve forward 1.0 caliber, I would have at least 2.0 calibers stability margin relative to that curve at all Mach numbers.

Once the supersonic stability margin falls below 1.0 caliber, even though the rocket is technically stable, coning, pitch-roll coupling, and other difficult to predict effects can become present. To avoid this, I'd keep the stability margin at least at 2.0 calibers for all Mach numbers.


Chuck Rogers
Rogers Aeroscience

Thank you to everyone for the warnings on stability and parachute sizing. I was aware that RASAero was going to be updated for to move the CP forward ~1 caliber at mach speeds, and we have been planning according. However, we will go ahead and build the rocket in OpenRocket to confirm, and consider upsizing on the fins. Its definitely something where we should err on the side of caution. Chuck, I am looking forward to the release of RASAero 2.0, and its good to hear your feedback on the performance of 1.0.

We chose this parachute because I have had this 52" chute lying in my gear box for over a decade and thought it would be nice to finally use it. Burnout weight should be way below four pounds, we expect it to be about 25-30 ounces without motor. I will talk to the team about downsizing. The reduced tube length sure would be nice. Our landing sites are extremely hard and dense around here (rock and sunbaked clay) so we will probably look at something a little larger, possibly 30".

Rockethunter, I looked through your flying case thread and that was really a nice looking build. Unfortunately, I misspoke when I said we had a FWFG nosecone. I purchased the nosecone below thinking it was filament-wound but on closer inspection it was clearly made with a two-part mold. I don't have the BeeLine unit in hand yet, but I don't think we can fit it within the nosecone base. My understanding is that the GPS unit needs to be kept away from the altimeter circuitry and allthread in the AV-bay to minimize interference. That is why the rocksim screenshot from the first post shows two distinct payload sections with mass objects. How have everyone's experiences been with a transmitter mounted in the AV-bay? I know that you can purchase integrated units, so I do not know how serious that issue actually is.




Thanks for the comments.

Alex

RocketHunter said:

Cool project!

A couple things I learned from doing a 38mm MD on a similar motor (search I540 to mach 2):

2. On the subject of fins, sometimes it pays to design your rocket with bigger fins. On a recent 29mm MD build, I made the fins quite a bit taller than absolutely necessary. On its flight, the large fins payed off with a dead straight and vertical flight, which overall netted me similar altitude than what was lost by drag vs a design with smaller fins that could have weather cocked 5-10 degrees.

3. I would say to go drogueless. Unless your payload section is going to weigh a ton, there is really no need for a drogue. It will stay destabilized and fall at a rate that is plenty safe for the deployment of your main parachute. For really high flights you want to minimize drift as much as possible, and going drogueless will do just that.

4. You can definitely use a smaller main parachute. If your under 4 lbs at burn out, a 24" would be fine. A thin-mill chute from topflight works great and packs into ~1.5" of 38mm tubing. Your rocket is going to be quite tough, and doesn't need an ultra-gentle landing.

5. For wiring the electronics: a word of warning, high G flights (>30g) have an uncanny ability to cause electronics failures. Leave a few wires hanging loose, or a battery only tied down with a couple small zip ties, and the sustained g forces can just rip them out. Make sure everything is very securely tied down, things like JST connectors (I 5 min epoxy these closed before a >100g flight), wires running to terminals, ejection lighters, etc. The last thing you want is an electonics failure, it really stinks!

If you want to really go for altitude, get rid of the payload tube, and use your electonics bay as your nosecones coupler (the FWFG ones are removable), putting the drogue in its regular position and the main parachute inside the nosecone. Doing that will get rid of a ton of drag.

Have you decided upon your method for launching this rocket? Since your goal is altitude, you probably don't want to use rail buttons. A launch tower can work, as could 3-D printed fly-away rail guides (searching the forum you should be able to find the user who sells them)

All in all a very cool project, 38 MD's are awesome - tons of altitude and speed for their given impulse.

Click to expand...

Great information Coleman and thanks for posting. Your comment in number 2. above if you didn't make a flight with the same design rocket with smaller fins I don't know how you can come up with your conclusion. It follows if one goes with a larger fin or
more fins (4 vs. 3) the rocket should be more stable. I can understand the desire not to go to the extreme for the sake of safety.

Thanks for the chute advice. I've been trying to cram a 30" chute into a Go Devil 38 and it is a hellaciously tight pack. Did a main chute ground test with .9gm power and that was way too much. Blew out everything and since I had the rocket assembled
with the sustainer attached to its shockcord, pulled the ebay out of the sustainer tube and extended the nearly 15' shockcord to its full length. Fried the shockcord protector but wow is kevlar tape strong.
The burnout weight is going to be less than 4lbs. I used an EggTimer remote switch for the test and am getting ready to do another ground test. Will switch to a 24" chute. Kurt

You going to use a Mobilinkd TNC for B/T connection to APRS Droid? If someone has a working Kenwood D7, D72A or VX-8GR you can interface any of these APRS devices into any of the serial round port Garmin mapping GPS devices like a Garmin 60Cs or 60Csx. An el cheapo Gamin Legend with a square connector on the device can do the same thing. You can have the 60Cs(X) lock the rocket "waypoint" (navigate "to" selection) while it is on the pad and it will navigate in realtime as long as it receives packets while in flight. If it loses lock, no problem, the last position is on the screen. Get to the last known packet position and if you don't see the rocket, you'll likely pick up a new packet to take you to the final position. (Free Open Source maps are available for Garmins so you could go used and still have a decent map. https://garmin.openstreetmap.nl/

There is absolutely no muss or fuss as it's all automatic. You can scroll between the screens on the Garmin too. It has an HSI (Heading Situation Indicator) that gives you a compass rose and arrow pointing the way. It will even tell you how long it is going to take for you to get to your recovery site at the current speed you are travelling. I've done some tests with APRSDroid and it's not designed for navigation. If you walk towards your downed rocket, in order to get your current position to change on the screen, you have to transmit a position packet to get your "position" to move. Your position only updates on the screen when you transmit a position packet only. I've been trying to find out if this has been remedied with the current iteration of APRSDroid but haven't been able to test it out.

Most tracking laptop programs will allow one to transmit, via Rf, their position at certain intervals but the screen position on their device will show their up to the second position changes. Set your Beeline GPS outside and then practice walking around with your APRSDroid device. You'll understand exactly what I mean. You won't see "your" position change on the device until you fire off an Rf packet. You can set a transmit rate but if your position, collides with a packet from the Beeline, you won't receive it so it's best to manually transmit a position packet so you can see your position move on the map.

I did a stationary test with APRSDroid/Nexus7/Mobilinkd H/T combination with the receive station stationary with the LSO while I went after a sight unseen rocket with my Garmin 60Cs/D72A combination. When I got back, it showed the complete rocket flight to 6k' .85 mile away and my track back to the stationary setup after pickup. It recorded everything fine. I unfortunately couldn't hold all that stuff at once to recover the rocket and test out the APRSDroid station simultaneously.

No matter what receive station you have, make danged sure you practice with it ad nauseum before you go fly. Set the BLGPS for no less than 5 second intervals. You can set the internal memory to store 1/sec and download the .kml file later for Google Earth display.

Another thing, if there's an extra Ham around with an APRS receiving station see if they can ride shotgun for backup. Where I fly, there's sometimes two of us and one locks their rig to display and call out altitude and the other watches the map to yell where to look for the expected main deployment. With a sight unseen rocket it helps and you'd be surprised even at a mile or two out you can't see a 24" to 36" main chute with a small rocket.

But..... you'll sure as heck know that the main is out by the slow(er) rate of descent. Best of luck Kurt

RocketHunter said:

4. You can definitely use a smaller main parachute. If your under 4 lbs at burn out, a 24" would be fine. A thin-mill chute from topflight works great and packs into ~1.5" of 38mm tubing. Your rocket is going to be quite tough, and doesn't need an ultra-gentle landing.

If you want to really go for altitude, get rid of the payload tube, and use your electonics bay as your nosecones coupler (the FWFG ones are removable), putting the drogue in its regular position and the main parachute inside the nosecone. Doing that will get rid of a ton of drag.

Have you decided upon your method for launching this rocket? Since your goal is altitude, you probably don't want to use rail buttons. A launch tower can work, as could 3-D printed fly-away rail guides (searching the forum you should be able to find the user who sells them)

All in all a very cool project, 38 MD's are awesome - tons of altitude and speed for their given impulse.

Click to expand...

Snipped out a few things....

For recovery.... have you considered a streamer? I use a streamer instead of a parachute on almost ALL of my lighter rockets. It's much easier to see than a parachute.


As for the launch guides... shoot wfcook a message. He has fly away rail guides.

A few comments.

1.) Your rocket design looks a lot like the Rocketry Warehouse GoDevil38 which costs $70. It would be simpler and cheaper to buy the kit and kit bash rather than purchasing individual parts. This kit has a 5:1 VK nosecone which will have lower drag and than any 4:1 nose cone, and is fiberglass kit which is lot stiffer and stronger than Bluetube which might experience column bucking in the Mach range at the aspect ratio of your rocket.

2.) Your research motor design is essentially a Loki Research 741H528-LW with this thrust curve. This reload costs $52 and is a legal certified L2 motor in all states except for the Republic of California as it is not CSFM approved and therefore not legal to import into the state.

3.) You stated your rocket design has a 0.16 caliber stability margin (0.25"/1.6") at 15 degrees AOA. This rocket will be extremely twitchy and if it hits wind-shear or turbulence you can exceed a 15 degree AOA causing the rocket to instantly pinwheel, which is a very high drag configuration.

Designing a big motor, small finned, long (L/D>10), minimum diameter rocket with insufficient stability margin is a common beginner mistake. As the motor burns, the CG can move rearward as propellant is consumed and the Cp moves forward as the velocity increases. Believe Chuck Roger's comment concerning the need to have a minimum stability margin of 2 calibers throughout the flight regime.

Bob

Thank you all for your comments.

Ksaves2, I was thinking we would run a cable directly from the mic/speaker ports on the transceiver to the phone. Thank you for sharing your experiences. We are still waiting on our equipment and my license to be updated with the FCC, but we will take it outside and do extensive testing when I can transmit. Its good to know that APRSdroid has that quirk. At the moment, my thought is to cache the maps in offline mode, disconnect the radio, and just use google maps to lead us to the last known good position. This assumes that the last reported position is close to the rocket, but we have miles of free air in every direction at this launch site, so I think that is a safe assumption. Any thoughts on that?

blackbrandt: We have considered pure streamer recovery. We originally wanted to use the chute we have on hand, but will be downsizing to something smaller. We still plan on sticking with a parachute, however, as it would need a lot less material for a given braking force compared to a streamer. We are operating under the assumption that it will be BVR for the majority of the flight so visibility is secondary to weight and bulk.

We plan on ditching the rail buttons for a fly-away guide as well.

Bob:
1. Thanks for the tip on the GoDevil38. We have most of our building materials like tubes and nosecones on-hand already. The 4:1 ogive was chosen for the preferences of a few of the team members. Under a pure performance metric we would have chosen the 5:1 VK, but we want to have fun with this project and so we went with what they preferred. This is one of the only places we have allowed aesthetic desires to rule over altitude numbers.

2. One difference between our motor and the posted thrust curve is that we have chosen a progressive thrust profile. That said, I have no doubt we could accomplish close to the same altitude, with less risk, work, and money, using a commercial load. Our best case scenario is probably to achieve something on-par with commercial loadings. The purpose of using a research motor is to build my practical experience with solid rocket design, rather than to optimize any given performance metric.

We actually are located in California, which makes things that much more complicated. The Friends of Amateur Rocketry have the proper pyro-handler permits to build EX motors at their test site. We plan to build and operate the motor under their supervision.

3. As I posted above, we will be reevaluating the stability of this rocket, and most likely making the fins larger. Excessively large fins are obviously a lot less costly than the alternative

Is 15 degrees really a realistic number to hit due to wind shear? The slowest speed the rocket experiences throughout the majority of the ascent is the moment it leaves the rail. At that speed, it would require a windshear of over 25 MPH to achieve a 15 degree AoA. We were thinking not to launch in winds greater than 15 MPH, or in cases of excessive winds aloft, so a 15 degree AoA was seen as a fringe case.

How does the CG move rearward from propellant burn if the motor is located behind the CG at launch?

Thanks Again,
Alex

Bob and Alex

Bob I have a GoDevil 38 and I've built one stock. I built mine for a 720 case to get some decent altitude with a venerable J350 and some ex loads I've come up with for AT hardware.
Your advice mirrors an article by Robert Galejs, https://argoshpr.ch/joomla1/articles/pdf/sentinel39-galejs.pdf, "What Barrowman Left Out" which suggests one should allow for a farther
forward CG with a high L/D rocket.

I missed the part of using Blue tube. I'd guess one would need to be careful at the fin/tube interface with adhesion using SM fins.

CP/CG. I believe the CP moves forward at higher speed (Mach) and the relative rate of shift forward is faster than the rate of the CG shift forward as fuel is burned. The bottom line is the CG and CP is shifted closer together at higher speed. Hence the fuel transfer practices at high Mach in the B58, SR-71 and Concorde aircraft. Plus the inherent fact that the Barrowman equations weren't completely accurate in high L/D (length to diameter) rockets necessitates better CG planning in that case.

Alex, cache maps at your own risk. I've done it with other apps and sometimes it works, sometimes it all of a sudden doesn't. A better remedy is to use the APRSDroid version that allows for self-contained use of Open Source Maps: https://aprsdroid.org/osm/ I've not experimented with APRSDroid to see if it will still post icons to a bare screen and finding out at the launchsite
it doesn't, will ruin your day. Go with the self contained maps if you don't have onsite internet access and you won't have to worry about it.
If you have a line on building a cable to go from your Android device to your H/T thoroughly trouble-shoot it and test it out. Me? I was too lazy and spent the $70.00 for the Mobilinkd B/T TNC
that is guaranteed to work out of the box. You'd better be ready to experiment if you are going to do AFSK via Speaker/Mic. With the Mobilinkd, just make sure you have the volume control marked on your rig after you run the Android Mobilinkd setup utility (easy) and you're good to go. You gotta be careful with the flimsy OTG cable input/output on the Android. Way too easy to get accidentally ripped out. Have that happen onsite and that could ruin your day too.

Boy, if you find a flier with a Garmin GPS/APRS setup it would relieve a lot of headaches. One cable from the APRS H/T to the Garmin 60Cs(X) and that's it. Make sure the Garmin output is
selected for NMEA (as opposed to the GARMIN proprietary) No setup program, no volume gains to screwup. How do I know? I've made a lot of field screwups thats how.
Laptop power supply failures, connector failures you name it. Kurt

Kurt, thanks for the warning on the map caching. I can see how unexpected things can happen on-site am give you a very bad day.

We would still like to use the cable if possible, but will do extensive testing to make sure the solution we use is robust. We have a large "open space area" nearby that doesn't get cell coverage and will be testing there. Right now we are looking for a simple coordinate-based GPS app that uses an arrow and distance reading to avoid complications with the mapping software.

I ran our rocket through OpenRocket, which as suggested here was far less optimistic than RASAero. With the turbulence set to maximum, I managed to get the original design down to .5 calibers of stability in openrocket at mach 1.6+.

We also ordered a 30" parachute. We chose to go up one size because of the extremely unforgiving ground here in Southern California. We shortened the body tubes accordingly in the sim, and redesigned the fins to yield more than 2 calibers of stability at maximum velocity with the new body length.



Thanks again for the input, everyone.

You could very well just input your incoming lat/long into any mapping GPS or GPS phone app and be able to navigate to the last known packet position. As long as your tracking station is portable, drag it out to the last known packet position and if you don't see the rocket, you'll likely pick up a new final position fix. Kurt

Hokay,

You got me going on APRSDroid so I decided to do an updated test with the AP510 2meter tracker that can bind via B/T with an Android device so I can send packets out via APRSDroid. The Sainsonic AP510 can also function independently so I could hit the manual send button and get a packet digi'd as -9 and the -6 packet was from the Nexus 7. Can test the internal GPS of the Android device against the internal Sirf4 from the Sainsonic.

I re-confirmed that APRSDroid only shows your ground station movement when you send off an Rf packet. Easily enough to use the right pull down and hit "single shot".

I think you will have a very workable system but use the APRSDroid version that will work with the downloadable maps. There is a link to the maps on the APRRSDroid website but not the Google apps site. Get it from the APRS Droid site. Kurt

Kurt,

Thanks for doing some testing on your own equipment and offering your input. We will definitely download the offline maps, and will probably be looking at a couple of redundant mapping solutions just in case they are needed.

Can you offer any insight on the effects of mounting the tracker near the altimiter in the AV-Bay vs the nose? I have seen some warnings about mounting the devices in the same bay, but I have also seen a significant number of build threads where the two devices are mounted immediately adjacent to each other with no issues.

Of course, any mounting solution will see a lot of testing, but we would like to hear some firsthand experiences on the subject before we put our bay together.

Thanks,
Alex

Just to update, we have received our the tracker donated by BigRedBee. The BeeLine GPS is smaller than I expected, and is an absolutely effortless fit into the nosecone we have. Huge thanks to Greg at BigRedBee for the support.


We are currently considering different mounting methods but it will definitely be going into the nosecone instead of the AV-bay

raptor22 said:

Kurt,

Thanks for doing some testing on your own equipment and offering your input. We will definitely download the offline maps, and will probably be looking at a couple of redundant mapping solutions just in case they are needed.

Can you offer any insight on the effects of mounting the tracker near the altimiter in the AV-Bay vs the nose? I have seen some warnings about mounting the devices in the same bay, but I have also seen a significant number of build threads where the two devices are mounted immediately adjacent to each other with no issues.

Of course, any mounting solution will see a lot of testing, but we would like to hear some firsthand experiences on the subject before we put our bay together.

Thanks,
Alex

Click to expand...

Hmmmmm, Didn't get a notice of your post. Anyhow, the Beeline GPS with its lower power output plays well with most electronics. I see a problem with your photo. It's a no-no to curl up the antenna. It will decrease your range a lot.
That nosecone is too small. You need to have that antenna extended straight out. To prove it to yourself, go to an open area and do a range check with the antenna extended and with the antenna curled up. If you want max range you'll find out which is better.

You either need a longer nosecone or take a short piece of bodytube and make a small bay aft of the nosecone shoulder so you'll have enough room for the tracker with the antenna extended straight out. Put a solid bulkhead for an eyebolt at the aft end leaving room for a tube coupler or integrate the coupler into the bay. You'd be good to go with a nosecone payload bay. You could epoxy a forward ring in the cone to keep the board from sliding forward. A couple of small screw to hold the tube on the nosecone and it's an accessible bay.

Remember no metallic paint in that nosecone. It will quench the Rf trying to get out. When you get completely done, put bare ematches on the altimeter terminals, button it all up, turn everything on and let it sit for
30 to 60 minutes. This would be a good time to do a ground level range check with your receive station. If no ematch popping or resetting of the altimeter, you will likely have no trouble with the tracker interfering with the altimeter.

The Beeline GPS units play well with other devices but you can't be too careful. https://tripolipeoria95.com/uploads/OMG5.jpg

The above was the result of a 2 watt dog tracker dorking two adept 22's. No events.

I don't think you'll have that kind of trouble but if you can't receive any packets, unless you get a visual on the rocket coming in, you'll lose it. I've had a small rocket land .65mi away under a 36" parachute and
none of the events were seen. Never saw the rocket until I walked directly up to it and saw it was a normal recovery. BLGPS by the way and hit a mile high AGL by 20 feet.
Well, I could tell by the descent rate altitude readout that the drogue was out and there was a noticeable slowing after 1000 feet AGL was passed on the way down. I have a tendency to pop the main at 1000' so it
gives the tracker more time at altitude to get some packets out so a trend to landing can be seen. Of course that depends upon your venue.

One other tidbit. Avoid sealing up a tracker in a bay with metal all thread paralleling the antenna. Bad news for range. Not an issue with nosecone mounting. Kurt

A cable cutter or single deploy will shorten up your rocket by quite a bit.

flynfrog said:

A cable cutter or single deploy will shorten up your rocket by quite a bit.

Click to expand...

Hooboy,

True but there's an art form getting them to work reliably (Archtype cutters for small stuff). There's a whole thread about it here somewhere. Kurt

Not so sure what would be hard about getting them to work I didn't have any issue make sure you zip tie you ematches to the shock cord with plenty of slack. Now that I have cursed myself forever.... On a 38MD you could almost get away with just letting it tumble.

38mm
Bring it back on a Top Flight 100" heavy duty steamer.

flynfrog said:

Not so sure what would be hard about getting them to work I didn't have any issue make sure you zip tie you ematches to the shock cord with plenty of slack. Now that I have cursed myself forever.... On a 38MD you could almost get away with just letting it tumble.

Click to expand...

Folks have posted video of a main chute taking its ever-loving time getting out of the chute protector after the zip tie has been blown/broken and others have reported many a "Hail Mary" recovery process. Some suggest blowing the cutter at a higher
altitude to give it time to get the chute out. I'm talking about the Archtype cutter for the smaller rocket not the large Tender Descender types. I have video not of a cutter in operation but of a drogue that took its ever loving time to
"get out of" the parachute protector. Just flittered around the shockcord before is shook itself free. Nothing was restraining it. Kurt

ksaves2 said:

Hmmmmm, Didn't get a notice of your post. Anyhow, the Beeline GPS with its lower power output plays well with most electronics. I see a problem with your photo. It's a no-no to curl up the antenna. It will decrease your range a lot.
That nosecone is too small. You need to have that antenna extended straight out. To prove it to yourself, go to an open area and do a range check with the antenna extended and with the antenna curled up. If you want max range you'll find out which is better.

You either need a longer nosecone or take a short piece of bodytube and make a small bay aft of the nosecone shoulder so you'll have enough room for the tracker with the antenna extended straight out. Put a solid bulkhead for an eyebolt at the aft end leaving room for a tube coupler or integrate the coupler into the bay. You'd be good to go with a nosecone payload bay. You could epoxy a forward ring in the cone to keep the board from sliding forward. A couple of small screw to hold the tube on the nosecone and it's an accessible bay.

Remember no metallic paint in that nosecone. It will quench the Rf trying to get out. When you get completely done, put bare ematches on the altimeter terminals, button it all up, turn everything on and let it sit for
30 to 60 minutes. This would be a good time to do a ground level range check with your receive station. If no ematch popping or resetting of the altimeter, you will likely have no trouble with the tracker interfering with the altimeter.

The Beeline GPS units play well with other devices but you can't be too careful. https://tripolipeoria95.com/uploads/OMG5.jpg

The above was the result of a 2 watt dog tracker dorking two adept 22's. No events.

I don't think you'll have that kind of trouble but if you can't receive any packets, unless you get a visual on the rocket coming in, you'll lose it. I've had a small rocket land .65mi away under a 36" parachute and
none of the events were seen. Never saw the rocket until I walked directly up to it and saw it was a normal recovery. BLGPS by the way and hit a mile high AGL by 20 feet.
Well, I could tell by the descent rate altitude readout that the drogue was out and there was a noticeable slowing after 1000 feet AGL was passed on the way down. I have a tendency to pop the main at 1000' so it
gives the tracker more time at altitude to get some packets out so a trend to landing can be seen. Of course that depends upon your venue.

One other tidbit. Avoid sealing up a tracker in a bay with metal all thread paralleling the antenna. Bad news for range. Not an issue with nosecone mounting. Kurt

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Thanks for the input, as always. What do you think about running the antenna with just one short u-turn where it leaves the board, as so? If we have to seek a longer nosecone we will, but it would be nice to stuff it into the nosecone we have without adding any length to the body tubes.

flynfrog said:

A cable cutter or single deploy will shorten up your rocket by quite a bit.

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Flynfrong, we considered both single deploy and cable cutters. Single deploy was ruled out because our sims were predicting that it could drift nearly 5 miles under some circumstances and we wanted to avoid a long hot hike through the mohave. In addition, we wanted to get some experience under our belt implementing a dual deploy system.

We also took a look at cable cutters, and those were seriously considered but we decided to go with a standard configuration because of the fact that some people have had less than perfect success with them. Being new to dual deploy, we wanted to stick with something that was a bit more foolproof.

You could try it that way but I would do a range test out in the open if you could. Put it on top of a 6 foot step ladder and see what you get.
Try it with the antenna fully extended to see what your baseline is. Kurt

ksaves2 said:

You could try it that way but I would do a range test out in the open if you could. Put it on top of a 6 foot step ladder and see what you get.
Try it with the antenna fully extended to see what your baseline is. Kurt

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Awesome, we will hopefully be doing that this week and will report back on how it works out. I have a good feeling on it, but since this is already a shortened antenna for 70 CM applications I may be totally wrong on how it will impact the performance We have a lot of hilly terrain nearby so can probably test the full line-of-sight range.

We also got our motor hardware in this week, 38/740 EX gear manufactured by Loki with a custom nozzle. Big thanks to our latest sponsor, K2 Engineering & Project Management, for donating the resources for this hardware.



We'd also like to thank AeroRocket for providing us a copy of AeroFinSim for our fin flutter simulations.

Our team had a build meet yesterday. Unfortunately, some of the photos are a bit grainy due to the lighting situation in my house.

We debated about the GPS antenna and decided ultimately to run it into the parachute bay to keep it straight. One of our members carved a padded GPS holder from EPP foam that fits quite snugly into the nosecone.

I have a few pieces of scrap carbon lying around that were surplus from old projects, so we went ahead and used it on a few parts we started work on (just for kicks). This includes a set of unnecessarily photogenic bulkheads.

Bluetube you're OK. I run the antenna of my Beeline GPS into the forward main chute bay of my WildmanJR. I have a small hole in the bulkhead and seal the edges with clay/grout material. I put a single wrap of duct tape around the cardboard tube that AT "wired" igniters come in to stent the antenna so it doesn't get squished down by the parachute. You'll want to do something like that so the antenna stays as straight as possible. I place the stent over the antenna and against the
forward bulkhead securing it with clay/grout. Radio lucent and I've had perfect tracking with seven flights. Ya gotta support the antenna. I didn't in another project that fortunately came down within sight and the antenna was scrunched up at
the base of the main chute tube. Kurt

We will definitely be supporting the antenna. One of the team members has some purpose-built antenna sheathing that we will use. We are considering gluing the sheathing to the tube wall as well, but that would require some slight bends in the antenna.

With the start of the school semester, things are slowing down a good bit, but we are still managing regular progress. The electronics mounting is close to done, and we will be starting the fin mounting soon.

The Painting is coming along well, but our painters are having a tough time getting the paint 100% smooth. Any tips on getting a real polish on these parts? Just lots of wet sanding with fine paper, or do you guys have other suggestions?

We also are pleased to announce we will be teaming up with the SDSU Rocket Project for this academic year. This is a big step for the team. Expect to see some cool things from us following the completion of Icarus 1.


Thanks for looking, and I hope all of you guys out at BALLS are having successful flights.

Just to update, things are still moving steadily along.

We got a chance to cast the propellant recently with our propellant mentor, but there are some complications with the mandrels sticking. He has some tricks to get them un-stuck, so stay tuned for details on that process. We ended up going with a pretty aggressive catalyzed propellant that is simulating a delivered ISP of 247 in BurnSim for our motor geometry.

It will be very excited to see how this motor will perform under real-world conditions. We will have enough propellant for two reloads, so we should have an opportunity to post the actual delivered thrust curve after static testing.

Unfortunately, I didn't take any photos of the casting process, so I don't have any visuals to post.