Sprite - 6" and a baby O

[G_T]

Well, I ordered an IRIS Ultra 96" to bump the size of the main a bit. I really like these chutes by the way! I'll be ordering a SkyAngle Classic II 60 for nosecone chute shortly. That's a bump up from the 52" I flew last time. I thought 52" would be sufficient but the nosecone still came down a bit like a bomb drop, probably a third faster at least than the rest of the rocket. Essentially everything came down too fast.

I have a Cert 3 SkyAngle drogue which is slightly larger than the Rocketman drogue I flew last time, so I'll give that one a shot. I don't like spinning drogues as my observation is the swivel doesn't swivel enough and the lines twist up, reefing the drogue increasing the descent rate. At least I've observed this every time on video. But I haven't flown this particular SkyAngle drogue before so perhaps it will be a bit different. Fingers crossed... I suppose I could fabricate a small shroud spreader that goes near the base of the lines. Forcing them to be spread even a little would make the required torque to wind up the lines so high that the swivel would certainly spin instead. I might have to look into that.

My 1" tubular nylon main harness is already shot. That will get replaced before the next flight. I should have put gaffer's tape over the part which can rub on the tube. My bad.

The motor tube needed some serious cleaning since the liner split and there were problems with burn thru. I found that Gojo hand cleaner - the version containing pumice - does a good job. I use a bristle brush a bit larger than the ID of the case. Slip a shop paper rag over the brush, put some Gojo on it. and slide it into the tube. Hook up to a hand drill, and go at it. Rinse well afterwards...

With the chute changes I'm likely going to have to make a dbag change.

Gerald

 

[G_T]

I have the chutes, and thankfully they do fit in the old deployment bag. I took pictures of the packing process for putting the two main chutes into the dbag.

I start with packing the nosecone chute. This is a SkyAngle 60" Classic II, and has three shrouds. If it had four shrouds I'd pack it a bit differently, but this method works well with three.

Flake the gores.


Gather the lines to what will be internal to the chute. I put in a half twist which I think helps reduce odds of lines trapping each other. I've done it this way many times and it has always opened quickly and reliably. I'm putting the lines internal because this chute is effectively going into the deployment bag backwards when we are done.


Fold the apex over the upper part of the lines.


Fold one side in to centerline.


Fold the other side in to centerline, which takes two folds due to the asymmetry of the three line chute packed this way. This is the first fold.


Gerald

 

[G_T]

And this is the second. What should be noted here is that the sides are essentially rolled in, not wrapped around each other. This speeds opening and helps make it occur in a controlled fashion.


Z-fold the chute, leaving nice smooth outer surfaces.


Attach the chute lines to a short piece of Kevlar that attaches to the apex of the deployment bag. Actually, a quick link is looped through the apex of the dbag so loads are not carried by the bag at all. Slide the chute into the deployment bag, line first. It goes in quite neatly.


When this chute is deployed, it is pulled out by friction against the main chute which is yet to go into the bag. If the friction fails to pull it out, which is very possible, the chute will fall out anyway because it is a very loose fit, has a little weight, and is at the bottom of the stack under the drogue and nosecone. That is, until it comes out! Then the nosecone and drogue fall past, the lines pull taught opening the Z, the now streamer-like chute unrolls it's edges, and inflates.

Gerald

 

[G_T]

Now onto the main. It is a 96" IRIS Ultra from Fruity Chutes. I like these because I think toroidal chutes are neat, and they are very efficient. It is physically small for the weight it will be handling, in comparison to conventional chutes.

Toroidal chutes are different from conventional chutes in that there is a set of apex lines which attach around the perimeter of the hole in the center of the chute. These lines pull the hole downwards, making the chute take the form of half a donut when opened. This greatly increases the drag.

I pack these chutes with a variation of how I'd pack a conventional round chute. Hopefully this is pretty close to how a rigger would do it. Much of my info on chute packing is second hand from a rigger.

Flake the gores, gathering half the shrouds on each side. What is different about toroidal chutes is the apex shrouds show up in the middle.


Fold one side in, gathering its lines to the center.


Now the other side.


Now gather the lines together. They should be all nice and parallel, no twists. If this is not the case, then the original flaking of the gores needed to be preceeded with untangling and straightening the lines. If it isn't neat it isn't reproducible and if it isn't reproducible, it isn't reliable.


Gerald

 

[G_T]

Similar to what was done with the previous SkyAngle chute, fold in each side to the center once more.


Note how the width of the chute now basically matches the space in the dbag? If it were still too wide, it would get folded in again, or rolled in, until it did fit. The two sides do not overlap each other, but come together in the centerline.


Z-fold the chute to fit the bag.


Slip it into the bag on top of the other chute, oriented so the shroud lines are towards the middle of the bag.


This is essentially the position the bag and chutes will take part-way through deployment, when the lines have straightened out but have not yet pulled the chute from the bag.

I think I need to get a couple large rubber bands before I can complete the dbag packing, so I'll just leave it like this for now.

Gerald

 

[eengelgau]

Hi - I really like this - I gotta go try it now!

 

[G_T]

Gene, you'll have to let me know what you think!

Back to packing...

Bundle the shrouds with some tape. I leave a couple feet not bundled at the base of the canopy so it can start opening without resistance. But the tape will slightly slow the full opening of the canopy. This is a good thing given I'm planning on dropping it in at 100fps under drogue.


Stuff the bundled shrouds neatly into the dbag.


Close up the flap.


Using two large rubber bands, capture the strap. These are not knots, and they release without much force. But this way the rubber bands hold the flap closed. During deployment, the tug on the tubular nylon line pops the loop free from each rubber band, freeing the rubber band. When the second rubber band pops off, the strap pulls the dbag flap open.


Bundle the tubular nylon line. I leave enough unbundled at the dbag end for the dbag to clear the rocket body tube before the tension from the drogue needs to start breaking off the masking tape. Note these are NOT taped securely at all, just well enough to hold the loops casually grouped.


I will have to re-do some of this, as I need to put some gaffers tape on the tubular nylon in the region where it will contact the body tube opening. Otherwise, the nylon will wear and not last.

There is more packing to do, but that's it for now.

Gerald

 

[StanO]

I will have to re-do some of this, as I need to put some gaffers tape on the tubular nylon in the region where it will contact the body tube opening. Otherwise, the nylon will wear and not last.

Thanks for the chute packing tutorial. Just what I needed. As there seems to be a wide range of Gaffer tape types, what do you use and what width? It's a great idea.

StanO

 

[G_T]

Right now I can't find it around here. I was looking too... I'll be stealing a strip from a friend's roll. He guards it jealously because he hasn't run across another roll in a while either. 2" width is what we're using IIRC. Other than knowing it as gaffer's tape I don't know the type. I didn't get around to doing it to the first tubular nylon harness and by the end of two successful flights there was enough wear that I'm changing to the new one.

For those who don't know, gaffer's tape is far stronger, far tougher, and stickier than duc tape (or duct tape).

Even masking tape (the version that sticks well and doesn't release easily) can be used for the purpose. But gaffer's tape is in a whole 'nother league! It does a nice job of attaching video cameras to the top of launch towers as well. That's more like its original function.

Gerald

 

[CarVac]

You can order gaffer's tape online. It's incredibly tough, strong, and sticky, and most importantly it doesn't leave residues when you pull it off. It's intended for sticking wires or just making markings on the stage temporarily in theaters, where people could trip on residue from duct tape.

It's rather expensive stuff.

 

[JordanT]

It's rather expensive stuff.

Indeed it is...3-4x as expensive as duct tape, but far more manageable. I got my last roll from a local theater/sound/lighting supply store, but my wife ordered a roll from Amazon when she needed one for a show and couldn't take the time to go to the next city to get (1.5hr round trip). 2"x60yds is $20 at amazon (Prime shipping, if you have it, at that price), vs $15-16 locally I think vs $5-6 for duct tape.

 

[eengelgau]

Hi Gerald, I like the organization of the rigging a lot. Neatness counts here and I think many guys don't give it a thought! I would be cautious about taping the shroud lines however. I like rubber banding them better, and only on the tip where they z-fold. Anyway with your tape if it's a single thin layer of masking tape it's very likely OK. YMMV as they say!

For very large chutes I recently made a couple of Youtube videos... This technique works well for fully contained bags with laced lines like we make:

[video=youtube_share;YvzI5QJftjI]https://youtu.be/YvzI5QJftjI[/video]

[video=youtube_share;_0YHlspcqeU]https://youtu.be/_0YHlspcqeU[/video]

These are for a UAV manufacturer in Japan.

 

[G_T]

I never did thank you for the videos Gene, so THANKS!

I figure better late than never, so here are some pictures from the 12/15/12 launch at MDRA. This is from the previous packing job using smaller chutes. Pictures are couresy of Jerry O'Sullivan.



Gerald

 

[G_T]

We had another beautiful flight of Sprite at Red Glare on 4/14. We burned an EX 88mm motor with 6 bates and one tablet propellant + smoke grain, with my Sunrise 14 propellant. Conditions from early on Sunday were windy in my estimation for the expected 12Kft altitude for this flight so I held off launching until the end of the day Sunday. The winds (particularly aloft) had calmed to perhaps half by then. As it was, recovery used all the available field. Any more wind and the rocket would have been out in the trees. I'd like to launch higher at MDRA but it will take exceptional conditions before I'd do it.

From the recovery packing details in the preceeding posts, I reduced the width of the masking tape on the shroud lines to perhaps 1/4" strips with almost no overlap. I wanted to make sure they would release pretty easily. I also put some Gaffer's tape on the Kevlar drogue line where it rubs against the top of the upper tube, and on the main tubular nylon webbing where it also rubs against the top of the tube.

From initial impressions the chute selection this time was basically perfect. The nosecone and the rest of the rocket came down at matching descent rates after main deployment. So next time I'll likely tether the nosecone with its chute to the main chute. The nosecone drifts compared to the rest of the rocket which is of course quite a bit heavier and more stable. This time they landed perhaps 200' apart, from a 700' deployment.

I took a broken teledongle to the launch. So I was unable to collect telemetry during the flight. I decided to fly anyway since we had plenty of eyes on the rocket, and the expected altitude was only on the order of 500' higher than the previous flight where we kept eyes on it throughout the flight.

Keeping visual was more challanging this time though. There was a thin haze layer right at burnout height. Smoke starts after a short delay, and the smoke trail was a thin barely visible line through the haze - slightly lighter grey on light grey. It was only visible if one knew where to look for the thin straight line. But that was enough to enable picking up the rocket as a little micro dark speck after apogee separation. So we kept eyes on the rocket. Whew! It was tough though.

I split and burned through another liner. The light liners don't like my aluminumized propellants. Unfortunately, the nozzle now shows a hairline crack. It is done. I only got two burns out of that one but that's the luck of the draw. I wasn't being extremely hard on it but these are not motors for the faint of heart. I'd guess this one died from thermal stress because there is no evidence of anything else.

My main chute also now needs one of the shroud lines replaced. It shows some abrasion, possibly from landing. It landed in grass, but there were planty of knee high bristly little bush-like plants around.

The video camera was off when we got to it (fairly quickly as we drove). I'm hoping we captured video. The last time this camera flew it failed to capture video but it was involved in an unexpected high-G maneuver. Wind shear had turned that rocket and so it was traveling at a high rate horizontally when it deployed. Zipper, plus lots of G's... The video worked fine testing at home so I flew it. It is the old GoPro Hero. My Hero2 from the previous flight shut out under liftoff G's so I wasn't going to fly it again.

Nothing else to report yet. I don't have the pictures in hand for the launch. Perhaps someone has video of the launch. I do know stills were taken. I've yet to grab anything off the onboard video or altimeters. So, more details later...

Special thanks to Jerry O, Mitch, Al, and of course the crew at MDRA for making this launch possible. There was at least one other person helping out some but I apologize - I'm bad with names.

The next flight of Sprite should be NY in a couple months, on a baby 114mm O. That flight should rock!

Gerald

 

[G_T]

I've grabbed the data from the altimeters and gotten the onboard video. It is a mix of good news and bad news.

Good news first:

The EX motor had a flatter burn reducing the grain count by one, as predicted. The curve pretty accurately matched expectations. But it was slightly faster than I'd expected so it was more like an N3700 than an N3000 which is what I put on the flight card.

The MARSA54 performed perfectly. Redundancy is a GOOD thing!

Descent under drogue was 128 ft/sec. The slightly draggier drogue apparently straightened the rocket out enough that the overall drag was reduced. The old descent rate was only a little over 100 ft/sec. For flights on the high side for the field the increase in descent rate is a good thing.

There was very little slag on the nozzle... more of interest for the EX part of this experiment so not a subject for this thread.

Everything visually observable went pretty much perfectly.

Tracking smoke is a good thing!

The bad news:

Took the wrong Teledongle so no telemetry. The one I took doesn't establish link. Operator error...

The Telemetrum stopped recording data at apogee. This is the second flight in a row where something strange has happened with that board. It seems either the board or the installation isn't happy with shock loads. This time it quit as soon as it detected apogee. The previous time GPS data was garbage after apogee. I'll see if I can figure out what is going on, but it is likely that I'll retire that board. The problem is possibly not the board, but the battery was swapped to a fresh one, and everything else involved with that board is super simple. I think the G loading at apogee separation is lower than during boost anyway so I don't get it. Perhaps there is a wire with an issue that doesn't like negative G's, or something like that. I'll see if I can find anything.

Video - I have video... up until ignition. Same deal, different camera. Acceleration killed the video. Unlike last time, it didn't recover. This time though there is solid evidence for the reason. When I removed the camera from its case, the memory card was not solidly inserted into its slot. When it went into the case before the flight, it was in place. The card is oriented towards the ground so acceleration would be tugging on the card. Throw in some vibe... Next time I'm going to put a dab of some sort of glue (perhaps hot melt) to prevent the card from coming out or even shifting unintentionally.

The motor liner isn't liking the pressure/temperature and the pressure rise at ignition. At least my 114mm O case uses a thicker liner so it should be ok for the next flight, at URRF in NY.

I likely need to get some repair work done on one of the shroud lines for the main. Perhaps the light lines don't handle brush as well as heavier lines.

I'll need a new nozzle before I can use the 88mm hardware again. It cracked.

--- So I think that does it for the quick flight summary. Those interested can read some of the specifics from the included screen captures of some of the flight data. When I've received the launch pictures I'll post them here.

Gerald

 

[bdale]

The Telemetrum stopped recording data at apogee. This is the second flight in a row where something strange has happened with that board.

Was the TeleMetrum board firing pyro charges? If so, the symptoms suggest you might have tripped over the LiPo protection board issue I wrote about last week.

And about your TeleDongle, I'll be happy to try and fix it for you. Email me directly, [email protected], if you want to pursue that.

 

[G_T]

Fascinating! My old Telemetrum has been rock stable, perfect every time. The new one is one out of three flights. On one flight it went haywire on GPS after apogee, indicating a multi-mile excursion which did not exist - we had eyes on the rocket the whole time. On the most recent flight it seems the board essentially shut down right after it detected apogee. I'm thinking these symptoms are very consistent with the battery issue you found with the new supplier. I did not see your note or I'd likely have swapped the battery for this flight. Swapping the board would be a bit more work as my other Telemetrum is set up with dual batteries. Actually, that doesn't sound like such a bad idea now. Can one still do the separate pyro battery setup mod with the current Telemetrums? In this rocket I have the Telemetrum firing in parallel with a MARSA54, dual ematch setup in a Rouse-Tech CD3 CO2 system for apogee and in a Defy Gravity tether system for main.

The Teledongle case has cracks so I presume I exposed it to some pressure during transport. I haven't opened it up yet to see if it might have a busted solder joint or something to that effect. It typically lives in my laptop bag so when I go to launch I always have it with me. I just have to grab the little beam and the coax and I'm set. Thank you for the offer of taking a look at it!

Gerald

 

[Rocketman248]

Nice flight, Gerald! Here's the video from the pad cam. Once I get all my pictures uploaded, I'll post those too.

[YOUTUBE]SvOoaGQqpkA[/YOUTUBE]

 

[G_T]

Thanks!

Interesting motor startup in the video. I can see why I'm cracking liners. Pressurization is very abrupt, pressure is not low (target is essentially 1000psi), and the liners are brittle. Actually that flight I split the nozzle as well, though it split after burnout somehow - I'm guessing thermal shock.

Gerald

 

[Ethan]

Nice flight(s) and an excellent thread to read as well.

I found that reducing my target chamber pressure from 1000 psi to ~800 psi made a lot of those kinds of problems go away. Seemed to get less heat transfer and the motors became a lot more tolerant to propellant defects like delamination and porosity, although a low exponent helps a lot in that regard. Might be worth doing a couple of Propep runs on your propellant to see what, if any gains there from running at the higher pressure.

Ethan

 

[G_T]

It gains a few percent ISP; that's about it. The propellants I make generally are rather dense and won't have visible porosity. In one case (Sunrise 13) the density can get close enough to theoretical that the difference is lost in the error of my measurements. Sunrise 13 was the culmination of a number of tests. Sunrise 14 is just a first test of something else so the density is a little off theoretical. Particle size distribution isn't quite right yet, and neither is the solids ratio.

Certainly the heat transfer would be lower at lower pressure, or at least the transfer rate. In the long run I plan to be working with larger motors... Heat transfer is always going to be a factor. I have no problem making something kinder to the hardware. It is easy to do. Our group has flown a number of times on this EX hardware now. The harder hitting motors always split the liners. The cooler lower pressure ones are always fine. Honestly I'd like to be able to hit it a lot harder but I know the liners we're using won't take it.

I don't have issues with porosity or delamination for that matter. And yes, I generally like to work with propellants of lower exponent at higher Kn, and with propellants which exhibit a bit of a plateau.

I'm glad you liked the flight. When flying it is funny, but I don't really get to observe the flight all that well. Usually I'm paying attention to the telemetry and everything else. When I get to see the video or pictures afterwards is when I get to see it!

I'm sort of considering sticking a pretty hefty booster under this thing for NY, a 6 motor cluster that would be around an upper M6000 in total. Then I'd light the O5000. I'm not sure I can afford the booster right now though.

Gerald

 

[G_T]

https://www.flickr.com/photos/78604807@N00/8659976102/in/datetaken/ - Some pictures from Nick DeBrita of the flight this past weekend. Thanks Nick!

Gerald

 

[G_T]

Some slight change of plans for the motor for URRF. It turns out that none of the new batch of liners I picked up will fit in my motor case. They are all slightly large. I have one old liner left and a collection of casting tubes cut for it, with an already cast smoke grain. It is the original geometry motor from when I started this project, designed for very high volume loading. I'll be using a larger nozzle though to accomodate Sunrise 13 propellant characteristics. It is not exactly what I had in mind but it should work. The average impulse decreases from O5000 to somewhere around O4700-4800 for the main part of the thrust with a bit of increase in total burn time and the addition of a tail. This is going to decrease the max speed but it should still be supersonic. I could tweak the propellant to compensate but at this point I probably won't.

I should have test fit those liners months ago, and not just assumed they would fit because the old one fit. It might be that the old one was undersized. I had the case made to fit. The new ones look almost like a change in manufacturer. Well, they weren't made to be liners anyway, so what should I have expected?

Gerald

 

[CarVac]

Some slight change of plans for the motor for URRF. It turns out that none of the new batch of liners I picked up will fit in my motor case. They are all slightly large. I have one old liner left and a collection of casting tubes cut for it, with an already cast smoke grain. It is the original geometry motor from when I started this project, designed for very high volume loading. I'll be using a larger nozzle though to accomodate Sunrise 13 propellant characteristics. It is not exactly what I had in mind but it should work. The average impulse decreases from O5000 to somewhere around O4700-4800 for the main part of the thrust with a bit of increase in total burn time and the addition of a tail. This is going to decrease the max speed but it should still be supersonic. I could tweak the propellant to compensate but at this point I probably won't.

I should have test fit those liners months ago, and not just assumed they would fit because the old one fit. It might be that the old one was undersized. I had the case made to fit. The new ones look almost like a change in manufacturer. Well, they weren't made to be liners anyway, so what should I have expected?

Gerald

They are PML phenolic tubing? There seem to be various suppliers they use. Sometimes the tubes are kinda glossy on the outside, and sometimes they are more matte. If I recall correctly, at least in smaller sizes the glossy ones are smaller.

 

[3stoogesrocketry]

Gerald , have you tried Blue Tube 2.0 as a liner ? It has a OD of 3.120 vs PML of 3.130 and it may also fix your split liner problems.

Eric

 

[G_T]

No I haven't tried Blue Tube. Not knowing what is in it, I'm not super inclined to try. I used PML or other tubes containing phenolic because of the phenolic. Phenolic forms a char layer which is insulating, which slows the consumption of the liner. However the PML tubes just don't seem to contain all that much phenolic any more. This generic sort of liner is not working well enough for me in any motors for aluminum based propellant and higher pressures, not even for small ones.

The batch of liners I picked up sometime last year for the 114 look like the phenolic content is quite a bit lower than previous ones and the diameter is a little larger. I don't think it would have done the job anyway - not enough phenolic.

I'll do something about the situation after URRF - possibly make my own liner.

Gerald

 

[G_T]

Another successful flight completed, this time at URRF on Friday. Motor was a 114mm EX baby O4800 Sunrise 15. More details later.

Gerald

 

[G_T]

https://www.youtube.com/watch?v=isYOrBXx-C8 - Looks like the third launch in this video, the left away cell, is mine from URRF.

The flight nearly didn't happen. A JAVA update after testing but before the flight rendered my telemetry receiver useless But conditions were pretty good, the rocket was on the pad otherwise ready to go, I had plenty of tracking smoke loaded in the motor, the waiver was there, and so were we. Plus, there were plenty of experienced eyes and a large LZ. So I decided we should go for it and the button was pushed!

The rocket weighed 82# on the pad. The motor grain geometry was designed for a fairly dense aluminumized propellant I developed (Sunrise 15 which is just the 15th test in this propellant series) which has higher than usual density. The grain geometry was designed for maximizing the volume loading using some tapered cores. The fuel grain weight essentially matched predictions. As a result I was able to get the total impulse up into the baby O range for a case that otherwise would be an upper N. The motor performed as expected, with the burn duration within a tenth of a second of the predicted 5.4 seconds with essentially the expected profile. The liner was shot, but that was expected.

The best-guess altitude prediction was 18400AGL under perfect conditions, and 18031 (Telemetrum) 18037 (MARSA54) were recorded. Predicted max speed was mach 1.2 to 1.4 depending on burn rate. Mach 1.4 would have required erosive boosting of burn pressure which wasn’t quite indicated in the analysis (motor was designed to be just short of erosive at startup but when pushing the boundaries it is hard to be certain ahead of time) and wasn’t quite erosive in practice. 1346fps Mach 1.20 (Telemetrum) 1411fps Mach 1.25 (MARSA54) was recorded.

There was some wind present. I’m quite pleased with the degree the rocket matched RasAero predictions. No real surprise though as the previous EX 88mm N burns at MDRA have also matched predictions quite closely. The goals this time were to get over 18000ft and over Mach without mishap and both goals were achieved. Tracking smoke from a full diameter smoke grain made the flight visible through apogee and the rocket was visually re-acquired under main in the distance. Winds aloft were higher than on the ground so there was a bit of drift on the way down. Descent rate under drogue was 104fps (100fps target) and under main was 27fps (25fps target). The nosecone descended at the 25fps target rate to land perhaps 20yds from the rest of the rocket. Overall the flight was excellent in all regards.

Special thanks to Alan Anderson, Jerry O'Sullivan, and Mitch Guess for their assistance with this flight!

I've attached a few pics. Rockets Magazine has some as well if someone wants to search.

I apologize for taking so long to post anything from the flight.

Gerald

 

[daveyfire]

I've attached a few pics. Rockets Magazine has some as well if someone wants to search.

Found 'em! Page 18 of Friday. Nice flight!