As strange as it may be... I know nothing about rockets and I'm seeking advice.

[Rex R]

highly recommend getting ahold of the folks that K'Tesh mentioned in post#14 (you'll be needing their help launching it) they should be able to help build/get the motor/fly the rocket. current guess puts the rocket at 3 lb. ready to fly. now I know the density of angel food cake (0.3g/cm^3) (I looked it up).
Rex

 

[Rex R]

a G80 motor does not require high power certification to purchase/fly, though local restrictions may apply.

 

[LizBennett]

highly recommend getting ahold of the folks that K'Tesh mentioned in post#14 (you'll be needing their help launching it) they should be able to help build/get the motor/fly the rocket. current guess puts the rocket at 3 lb. ready to fly. now I know the density of angel food cake (0.3g/cm^3) (I looked it up).
Rex

Thank you all for your help. I did send Oregon Rocketry an email. If this does get completed I'll try to post a video here for those who are interested in how it all worked out.

 

[LizBennett]

Thank you all for your help. This answered a lot of my question as to what I should be looking into. I've already emailed Oregon Rocketry. If this actually completed I will post a video here so those who are interested can see how it turned out.

*Sorry for some reason that double posted.

 

[Rex R]

and here is the design file I whipped up:
edit
just about any builder should be able figure it out

 

[dhbarr]

I would fly the cake upside down such that initial acceleration presses it into a three-tiered "bowl" rather than trying to ensure it holds up under it's own weight against a flat tray.

 

[jlabrasca]

I'm desperately seeking advice... I'm hoping some of you are familiar with GISH or GISHWHES. I was tasked launching a wedding cake with a rocket 6 feet in the air. I have know idea if this is really even possible or safe. Was hoping for some input or help. Looking for someone to bounce ideas off. I've got the cake part down, it the rocket science part that is just out of my league.

What's your deadline. When does the rocket have to leave the ground?

How likely is it that the folks judging this challenge will distinguish a cake launched on a rocket from a cake projected into the air by an air cannon (for instance).

 

[K'Tesh]

Here's my redo of the design, using your figures... My idea is that it would be a rear eject 38mm powered rocket. The white areas are cake.

 

[boatgeek]

I think we're all overthinking this (on TRF?! Perish the thought!). As I understand it, they need to get a 10-ish pound cake 6' in the air. It can have a center tube of some kind. Since the desired altitude is barely off the rail, we can dispense with silly stuff like stability and recovery. It is heavy enough to be outside FAR 101, so you'd technically need an FAA waiver to fly it. Of course, if this went up in someone's backyard and didn't end up on broadcast TV or the internet, nobody would know.

So here's my design:
3-tier cake with a thin aluminum plate like a pizza pan underneath. Yes, metal parts, but necessary to hold it together and lighter than plywood. The cake diameter doesn't really matter, as long as the whole thing is less than 10 lbs. Cut a hole in the middle for a 3.5" tube. Attach a ring to the 3.5" tube to lift the aluminum plate. The center of the tube will be boxed in to fit a 1010 rail. Then put two motor tubes outboard and fly as a cluster. Let's say the whole shooting match is 15 lbs. Aiming for thrust to weight of 3:1 with as short a burn time as possible gives a minimum motor thrust of 100 Newtons each. The obvious solution is a pair of G106 Skidmarks. If you're in a fire-prone area, you might want something a little less exciting, perhaps a pair of G126 White Thunders. In theory, you could go with a pair of F120 VMaxes and have motor burnout before the cake cleared the rail.

Once the cake leaves the rail, it will tumble all over the place and probably come apart. Tumble recovery is a valid option, right?

 

[Zeus-cat]

Has anyone mentioned that this cake-rocket (crocket? ) will need to have a big hole in the middle to accommodate a rail or large rod?

 

[neil_w]

I see no reasons for fins; this thing is a saucer and should be well served by base drag. Just an airframe and motor up the middle should do it. I would expect it to be stable.

If parachute recovery is desired to avoid uncontrolled disassembly upon landing, a forward bullkhead could be flush with the top of the cake and hidden under a layer of frosting.

I would *not* expect the cake to take kindly to the launch G-forces.

I *would* expect this to be entertaining.

 

[mccordmw]

Stating this in as much non-rocket terminology...

Put the motor mount in the middle of the cake and treat it like a pyramid rocket (see embedded video).

• A safe launch should have enough thrust to be 6-8X the weight of the cake.
• If you're sitting around 2.5 lb for the cake, you'd want 15-20 lb of average thrust (2.5 * 6 and 2.5 * 8).
• Rocket motors are labeled using average Newtons of thrust.
• One pound of thrust is equivalent to 4.45 Newtons of thrust.
• By the math, 4.45 * 15 = 66.8 and 4.45 * 20 = 89
• For simplicity, that puts you in the neighborhood of a common G-class motor
• The number behind the letter "G" will give average thrust, so you need a motor like G67-G89.
• Talk to your local rocket clubs for help with building a motor tube, a thrust plate to sit the cake on, and help launching a G rocket.

 

[mccordmw]

Before launching, can you freeze the cake to help it hold together better?

For simplicity, I'd go with a single-use motor. Something like an Aerotech G80.

https://www.apogeerockets.com/Rocke...Motor_G80T-7?zenid=huhulom81ju399jjifpttf91j3

I doubt you're popping out a parachute, so the deployment charge would be removed. No need to worry about parachute timing.

 

[Dipstick]

Someone HAS to build this thing now

 

[neil_w]

Someone HAS to build bake this thing now

Fixed.

 

[heada]

Since you can't ensure uniform density in the cake, I'd suggest a spin stabilized launch to keep it from just tumbling at the top of the rod/rail. 2x G80 single use motors, canted slightly in the bottom layer of the cake with a central 1/2' launch rod should work and is accessible by anyone 18+. Remove the ejection charges from the motors and use "splat" recovery. Another option is to replace the cake with styrofoam covered in frosting which would be the safest and lightest option. It'll weight almost nothing and clean up would be easier.

Something to keep in mind for all these options is that there is a minimum safe distance everyone must be from the launch and obviously it has to be done outdoors. I think the minimum distance for a pair of G motors is 30 feet away.

 

[DavidMcCann]

Since you can't ensure uniform density in the cake, I'd suggest a spin stabilized launch to keep it from just tumbling at the top of the rod/rail. 2x G80 single use motors, canted slightly in the bottom layer of the cake with a central 1/2' launch rod should work and is accessible by anyone 18+. Remove the ejection charges from the motors and use "splat" recovery. Another option is to replace the cake with styrofoam covered in frosting which would be the safest and lightest option. It'll weight almost nothing and clean up would be easier.

Something to keep in mind for all these options is that there is a minimum safe distance everyone must be from the launch and obviously it has to be done outdoors. I think the minimum distance for a pair of G motors is 30 feet away.

Min safe for a pair of G80's is 200' https://www.tripoli.org/Portals/1/Documents/Safety Code/SLP 2017.pdf

264 Ns total installed impulse, complex, 200'

 

[DavidMcCann]

I've launched a cake box on D12's. Cake, G80....no problem.

 

[Peartree]

so I am picturing something like this

I was thinking that this might be the "other way 'round" like they did with the USS Enterprise rocket some years ago. Have a standard rocket and nose cone pushed "through" the center of the cake and then the cake itself becomes the "tail" sort of like a spool.

 

[blackjack2564]

Does this qualify as "having your cake & flying it too?"

 

[RocketDestroyer]

I'm stunned that no one has suggested staging or clusters. Yet.

 

[neil_w]

Does this qualify as "having your cake & flying it too?"

The whole idea is half-baked.

 

[boatgeek]

I'm stunned that no one has suggested staging or clusters. Yet.

Hey now, I gotta defend my honor. I suggested not just a cluster, but a cluster of sparky motors 13 posts ago! I'm a little more surprised that nobody has taken this in an HPR direction yet. I was hoping to see an Oddroc O version by now.

 

[Ted Cochran]

TARC 2010 Ace of Cakes launch.
Edit to add video link:

 

[DavidMcCann]

you could pretty easily stage this thing for each layer....how many D's to lift 15 pounds?

 

[RocketDestroyer]

Hey now, I gotta defend my honor. I suggested not just a cluster, but a cluster of sparky motors 13 posts ago! I'm a little more surprised that nobody has taken this in an HPR direction yet. I was hoping to see an Oddroc O version by now.

My bad. I skimmed through you post and missed the cluster part.

 

[Steve Shannon]

This really should be flown using a sugar motor.

I really like the subject: I know nothing about rockets, yet I’m asking advice. That should not be unusual, but from time to time people who know nothing come here to give advice.

 

[neil_w]

This really should be flown using a sugar motor.

Yes! That would really be the icing on the... uh... never mind.

 

[LizBennett]

I am amazed by the response this has gotten. I will post here the exact wording for this challenge. I have until friday/saturday to get my video entered. The other downside is I was hoping to find someone local who could help either donate their time and possibly a rocket. I realized this is an extreme and expensive hobby, and myself could not afford a couple hundred dollar rocket.

Submit
“Love lifts us up where we belong.” Now that you’re getting hitched, it’s time to make the cliche a reality. Create a fully decorated wedding cake that is also a fully functioning rocket. The cake must be at least 3 layers high, made of real cake, and traditionally decorated, and must be successfully launched at least 6 feet in the air—the higher it goes, the better.

 

[K'Tesh]

I don't know how much of a hurry you are in, but you could make the cake, put it on a piece of say 1/4" plate steel, and then use a 12 gauge to try and launch it...

You know... A Shotgun Wedding Cake.