Penguin 1: Supersonic Ice Cream Sandwich (Build Thread)

[Nodroc]

Motor: L1000W
Target speed: > Mach 1
Payload: Ice Cream Sandwich

I'm currently working on building Penguin 1 with the goal of launching and retrieving an ice cream sandwich that will reach supersonic speeds. I'm doing this with some financial support form the local ice cream sandwich company The Penguin Brothers in exchange for the penguin theme and advertising. I'll be including a GoPro Hero5 Session on board and hope to have redundant dual deployment systems along with GPS tracking (looking for all the advice I can get on that front). Body will be 4" dia. made from blue tube with a Public Missiles PNC-3.90" (98mm) nose cone.

Attached is my OpenRocket file as it currently stands.

Any advice is welcome!

 

[Nytrunner]

I sure hope the sandwich is in an insulated container, your deployment is on point, and your tracking skills are fresh. Otherwise it may stretching the definition of "sandwich" by the time you find it.

 

[blackjack2564]

Easily made container for ice creme : coupler lined with cork which can be purchased at HD office depot etc. comes in rolls [cheap] line coupler and bulk plates. fill with dry ice and sandwich. Penguin Bro. should have dry ice.
Put sandwich in baggie, just in case ya have a looooong recovery and it melts. No mess to clean up inside rocket!
If ya want to keep altitude down ditch the tailcone, that will lose around 700-1000ft and increase stability.
Don't paint it a dark color that would get hot!

If it fits in B tube get a fiberglass NC with coupler for shoulder. That will make a nice tracking bay for GPS away from all the other stuff ya have to stick in your rocket. A simple av-bay with 2 altimeters is standard stuff, you need advice on that also?
Go with simple cheap reliable,altimeters like Missleworks or Perfect flight unless you solder and can get an egg timer.

 

[David Schwantz]

I sure hope the sandwich is in an insulated container, your deployment is on point, and your tracking skills are fresh. Otherwise it may stretching the definition of "sandwich" by the time you find it.

Nah, just come up here and launch it. -30 below tonight.

 

[MClark]

Sweet.

M

 

[Nodroc]

I sure hope the sandwich is in an insulated container, your deployment is on point, and your tracking skills are fresh. Otherwise it may stretching the definition of "sandwich" by the time you find it.

Haha, you're not wrong! Hence the need for the GPS!

Easily made container for ice creme : coupler lined with cork which can be purchased at HD office depot etc. comes in rolls [cheap] line coupler and bulk plates. fill with dry ice and sandwich. Penguin Bro. should have dry ice.
Put sandwich in baggie, just in case ya have a looooong recovery and it melts. No mess to clean up inside rocket!

The current plan is to have the sandwich sitting in dry ice for about a day before the launch. It will be transported to the launch site in dry ice and placed in the rocket just before launch. I'm working on developing an ice cream sandwich bay that will feature a conical shaped capsule similar to a reentry vehicle. Testing out some deployable mechanisms to get the door to swing open correctly. If all works out, it will be lined with insulation and maybe have some dry ice in the bottom as a separate compartment. The bag is a good last resort though!

 

[Nodroc]

A simple av-bay with 2 altimeters is standard stuff, you need advice on that also?
Go with simple cheap reliable,altimeters like Missleworks or Perfect flight unless you solder and can get an egg timer.

I currently have a Perfectflite Strattologger which has worked great in the past. I'm curious though as to whether or not I should purchase another one or go for a different make and model of altimeter as the backup. My plan was to place the GPS in the av-bay but I've noticed most tend to place them in their NC. Is there any advantage one way or another?

 

[Nytrunner]

Probably a space efficiency issue. Some Bays have room, others don't.

Putting the antenna of the transmitter near threades rods in parallel can affect the radiation pattern. Some avoid it, some mitigate it, some strap it to the threaded rod and dont care.

If you have it in a rodless nose cone, theres nothing to interfere with the signal (unless your cone is carbon fiber lol)

 

[GlenP]

 

[Nodroc]

Haha, we're talking something more like this:

 

[Nodroc]

Alright, update. I've been doing a great deal of research into anything and everything. Let's go by systems.

Structures:
The blue tube I have has a slight divot at about half way up the tube. I'll be using this tube for the bottom portion of my rocket and will reinforce the body with a coupler placed at the exact same spot. I've ordered the fiberglass I will be using for the rocket fins, 1/8 in thick and solutions are being discussed about a fin jig to get those leading edges nice and chamfered. Still curious about filling the plastic nose cone with expanding foam. From what I've heard thats the ideal thing to do when flying these things at supersonic but haven't really seen it done (granted, haven't searched too hard either yet).

Avionics:
I've decided to go with the Eggtimer TRS GPS Tracker/Flight Computer along with the current PerfectFlite StratologgerCF I already own. Still looking into the best package to purchase for the TRS. Is it worth getting an FCC Technician's License to get the HAM version? Also looking into the option of just purchasing the TRS and utilizing the equipment of the school's Amateur Radio club to help out and offer their equipment and services as a ground station.

I've heard some serious debate on here about redundant systems, but "as for me and my house," we'll use a lot of redundancy. The current plan is to have each system independently powered. I'd love to use a "remove before flight" pin to arm the rocket on the pad but, again, I have no experience with that (my previous rockets used toggle switches--which worked, but is obviously not ideal for reasons I've learned and will not go into right now). If any of you have advice with where to buy a pin removal switch or the best way to make a reliant one, let me know!

I've been working to figure out how best to mount my GoPro Hero5 Session into the body of the rocket and I think I finally have a good working prototype in CAD.

It's still not right where I want it but its pretty close. I'll probably extend my switch band to be a bit thicker and then chamfer the leading and tailing edge of the outer cap to be a bit more aerodynamic. Here's my thought process behind this design. I really wanted to be able to place the camera into the rocket on the launch pad directly. Attached to the AV sled will be this box, built to the parameters of the GoPro. A cut in the coupler and switch band is made to be perfectly aligned with this box when all is put together. Then, the GoPro is inserted from the outside and the cap is placed over the top. Fasteners will be placed in each corner to hold it in place. Again, still working on it but excited for what's to come.

Payload:
Got some great results from the guys at the Compliant Mechanisms Lab here on campus and we've got a prototype of the payload bay running (also in CAD). I can't seem to get the video file up so I'll upload some pictures or figure it out later. But effectively we have a conical shaped bay designed to imitate a reentry capsule and we've installed a door on the side. I know, it sounds boring, but trust me, it looks awesome. We're flirting with the idea of attaching a cylindrical base to the bottom of the capsule that will hold dry ice for in flight cooling. The interior of the whole capsule will be coated with an insulator, currently I'm thinking thinsulate may be the best choice.

I've been giving some consideration into the possibility of testing the forces and impulse on the ice cream sandwich but have had some difficulty in finding an appropriate simulation short of literally launching the rocket. Ideas have ranged from dropping the sandwich off of a building or putting it into a centrifuge but both fall short of accurately measuring the impulse that will be imparted onto the sandwich. The freezing of the ice cream sandwich should make it much more resistant to compressive loading but as to how much, I can't say. Based on simulations, if it can survive the first three seconds, we'll be golden. Plus the dog barf inside the rocket tube should serve as a dampener of sorts.

Thats the majority of the update! Still got a lot more to plan and do. Let me know your thoughts and I'm always open to advice and questions!

 

[ebruce1361]

One method I have seen used for a "Remove Before Flight" pin is to use a lever microswitch aligned with two holes in the airframe. Wit the pin inserted, the lever is held down and the power connected to the switch is going through the normally closed pair (most of these switches have three terminals so it can be used in a NC or NO configuration). Pull the pin out, the lever pops up and the switch closes.



As for the rest of your project, I think this is awesome! I've actually had the thought in the past to build a rocket around a French press and brew a cup of coffee in flight, but never got around to designing any of it as yet. If your supersonic ice cream setup works, I might just have to try out the coffee.

 

[dr wogz]

Mount the switch sideways, so that any excessive G forces won't "close" the switch..

 

[ebruce1361]

Mount the switch sideways, so that any excessive G forces won't "close" the switch..

Excellent point! Even better, go upside down with it.

 

[blackjack2564]

No! do not use upside down...for reasons that are painfully obvious.

 

[mpitfield]

You don't need the arm on the switch to use it. You can get the same style switch minus the arm. If you hunt around the Forum, you will find some examples.

 

[ebruce1361]

No! do not use upside down...for reasons that are painfully obvious.

Maybe my coffee hasn't kicked in yet. Would you care to elaborate? If the switch were mounted with the lever on the bottom, I don't see how that would be an issue. As dr wogz said above, the force of acceleration could push the lever down if mounted upright, so wouldn't an upside down switch be even more ideal as the lever would be pulled even more away from the switch body?

 

[Donnager]

No! do not use upside down...for reasons that are painfully obvious.

That's not terribly helpful.

I don't use those type switches for a variety of reasons (mostly space, in a smaller rocket), but rather than just saying "that's stupid", perhaps you could offer an instructive rather than disparaging comment? I have a great deal of experience using these type switches to activate transbrakes, control wide-open throttle Nitrous, stutter transbrakes, and monitor brake and accelerator positions in drag race cars. I've also used proximity switches for some of these applications. They can endure tire shake, which can be very violent.

There are lots of snap action switches, with varying levels of "hardness" and resistance to high vibration, high G, etc.. If you have a description of the "painfully obviously flawed" installation, communicating that would help the community at large.

I have some ideas about why I wouldn't mount the switch inverted, but they don't fall into the "painfully obvious" category, and are mostly based on my opinions and expectations, rather than facts associated with the G-loads the switch can tolerate in multiple orientations.

Maybe my coffee hasn't kicked in yet. Would you care to elaborate? If the switch were mounted with the lever on the bottom, I don't see how that would be an issue. As dr wogz said above, the force of acceleration could push the lever down if mounted upright, so wouldn't an upside down switch be even more ideal as the lever would be pulled even more away from the switch body?

It probably depends on the switch. Some have an arm with a roller, some just an arm, some are just a 3/32" pintle that --barely-- requires any motion to move, the latter being restrained by the switch case. I suspect the concern is with a particular switch, but I don't drink coffee, and don't know the apparently serious issue being hinted at.

 

[ebruce1361]

@Donnager
Your insight is indeed more informative and appreciated. As to the application of arming/disarming electronics for a rocket of sufficient size to loft a mildly cryogenic dessert, I would suspect such a switch would have ample room inside an AV bay. The switch I had in mind was of the roller bar variety which would offer (in my thinking) the least difficulty with inserting and removing a long pin such as an ⅛ inch metal rod or even a bamboo kebab skewer. If upside down, the mass of the roller should further help keep the switch lever from going anywhere near far enough to break the circuit regardless of vibrations or g-forces. Still, should that be a concern, a redundant switch could be connected in parallel with a second pin to ensure no breakage of contact.

No worries on the coffee my friend, I'll have a cup in your stead. And maybe even an ice cream sandwich with lunch.

 

[David Schwantz]

https://www.labratrocketry.com/shop

these are great have many, never failed.

 

[ebruce1361]

https://www.labratrocketry.com/shop

these are great have many, never failed.

I knew I had seen those before! That's exactly what I was thinking except a home made version.

 

[Nodroc]

I greatly appreciate everyone's input on the switches! That will prove to be very useful. Meanwhile, I have some updates.

Structures:
Fiberglass has arrived and is ready to be CNCd. Hoping to get some last accurate measurements on weight of various pieces to verify CG and to modify the fin shape a bit before going forward. My big question now involves that of the nosecone. I'm worried about the plastic deforming in supersonic conditions. To repeat what I had said earlier, I've heard that a plastic nose cone going supersonic ought to be filled with some kind of expanding foam. Is there anyone who has had experience with such a situation and would like to share their sagely wisdom?
Color scheme has also come in from the Penguin Brothers. Light pink with baby blue fins. Any tips on painting?

Avionics:
Still trying to get a feel for whether or not its worth it to get my HAM Radio Technician's license and buy the fancier Eggtimer TRS. School's radio club hasn't responded to my emails so we may not have much support there for a receiver.

Payload:
Probably the most updates here! I've been doing a good deal of research into various possibilities for insulation. A lot of the feedback I've received has been to work with styrofoam. I was pretty skeptical at first but with some further consideration, I'm starting to think its not too bad of an idea. Additionally, I have a video showing the payload bay for you all to see. It doesn't seem to have a thumbnail but feel free to take a look. If this doesn't work you can also see the same video here.

Ice Cream Sandwich Bay

• Nodroc
• Feb 13, 2020

To be 3D printed and inserted into the upper body tube of the host rocket. White cylinder inside...

So thats the majority of the updates. Nothing too grand or fancy. Biggest questions I think are those of nose cone filling and if its worth it to get the Technician's license.

 

[blackjack2564]

That's not terribly helpful..

I am out of town, my friend had a freak accident, has been through 4 surgeries in the past week, removing his spleen and kidney along with 3 fractured ribs, so I haven't been on here, my apologies. I am taking care of his pet while he is hospitalized.

As to my reference. often forgot are the negative G's during apogee charge firing. They can easily exceed thrust G's. Common to see over 50 G's from ejection forces or more. So imagine switch being right side up and experiencing these severe negative forces only in reverse. happened to my buddy while practice flying a minimum before he set the O record on the O -3400. He went with placing them flat on BP sideways so it mattered not which way the forces happened.

Lining 2 up so rod goes through both and out the other side. Rod can go through airframe in either direction. Caps the end sticking out so during travel it cannot vibrate loose.... turning on.

Switch is between the 2 sleds right above the screw in aluminum BP with the tiny wood dowel inserted. This bay is entirely in the NC as the motor was airframe, so DD was handled in NC.

Second pic shows charge cannons sticking out back. The av-bay was in front section of cone with main and drogue in rear of nc.
Custom 7 to 1 NC almost 3 ft long with rear going over the motor. [rear cone had to be same as motor diam. and added another 10 in to length.]

These switches were exposed to very extreme G forces and came through fine.

 

[ebruce1361]

As to my reference. often forgot are the negative G's during apogee charge firing. They can easily exceed thrust G's. Common to see over 50 G's from ejection forces or more. So imagine switch being right side up and experiencing these severe negative forces only in reverse. happened to my buddy while practice flying a minimum before he set the O record on the O -3400. He went with placing them flat on BP sideways so it mattered not which way the forces happened.

Ah! G-forces from ejection. That is indeed a circumstance whereby the switches can be opened in reverse, and as you said, mounting them sideways would be more ideal. Additionally, I hadn't considered inserting the rod to close the switches. I've only ever seen these kinds of switches used with a rod/pin that was removed before flight. I can imagine that may be because it could be possible to forget to install the rod/pin to arm the avionics and fly the rocket whereas a RBF flag hanging out of the airframe is much harder to forget about. Still, I like the idea of the positive retention of an insertable rod.

 

[ebruce1361]

@Nodroc That is one fancy capsule! Is the hatch going to be hinged only or are you going to motorize it to open itself? Not that doing so would be incredibly useful, but it would be cool to recover the capsule after the flight, press a button, and have it open on its own with the dry ice fog pouring out like some cheesy 1950s alien visitation movie when a flying saucer hatch opens.

 

[blackjack2564]

Additionally, I hadn't considered inserting the rod to close the switches.

No, the rod is removed as is typical. Tiny dowel is only there to see where switch located for picture.

 

[Pariah Zero]

Any thought about stacking the freeze in your favor?

• Freeze the Ice Cream in a bucket of Dry Ice overnight (-78 °C) and until buttoning it up.
• Freeze the ice cream in Liquid Nitrogen (-195 °C)

Obviously, LN2 is a bit harder to acquire/use... but liquid nitrogen folded ice cream is so worth it. Best ice cream I’ve ever had.

Getting Dry Ice, however, is a lazy trip to the supermarket...

 

[Pariah Zero]

Light pink with baby blue fins. Any tips on painting?

Auto paints and clear coats generally top off at 300 °F. Hotter than that and you start to see damage. Just sitting in the sun on a hot day, I’ve measured the hood of my red car at 170 °F. I have no idea if that’s good enough.

You can probably do a better with Barbecue Paint, or brake caliper paint. But color selection is... well, not what you specified.

edit: I found a shop that will do custom mixed brake caliper paint.

Some powder coats are good to 1200 °F... but powder coating is probably best left to professionals - if only because you probably don’t have an oven big enough hold your rocket.

There’s also the issue of baking the powder (350-375 °F for 10-30 min) may expose the rocket to temperatures higher than the rocket itself can withstand... I’m not a composite expert, but I know paper tubes start to blister & warp around 150 °F. Curing Powder coat is definitely hotter than polypropylene can handle for 30 min (liquid at 340 °F... tops)[/url]

 

[Nytrunner]

Sport rockets fly "past M1" without special paint consideration all the time.

How fast are you predicting you'll go? And how long will you spend there?

Edit: I went back and saw your sim snip. If your peak velocity is only M1.3, paint it however you want, itll be fine

 

[Nodroc]

Sport rockets fly "past M1" without special paint consideration all the time.

How fast are you predicting you'll go? And how long will you spend there?

Let me clarify on that point. I'm not particularly worried about heat on the paint but rather how to get the paint to be applied as smooth and clean as possible. How would be the best way to get the paint looking nice and professional and really smooth to break that 1 M barrier?