Deployment Help

[mateozro]

Hello,
I have a few questions about rocket deployment. I am creating a single deployment rocket and was wondering if it would require a electronics bay with an altimeter and other components? Also, I'm a bit confused about how the parachute would deploy without any additional mechanisms. If anyone knows of any single deployment ground testing videos, I would appreciate it if you could share them.



Thank you!

 

[MarsLander]

I am creating a single deployment rocket and was wondering if it would require a electronics bay with an altimeter and other components?

Motors that are less than about 54mm in size typically include an ejection charge, so no electronics bay/altimeter are required. That ejection charge pressurizes the airframe, separates the nose cone and deploys the parachute.

What rocket experience do you have? What size rocket are you building? What size is your field and what size motors are you looking to use?

 

[mateozro]

Motors that are less than about 54mm in size typically include an ejection charge, so no electronics bay/altimeter are required. That ejection charge pressurizes the airframe, separates the nose cone and deploys the parachute.

What rocket experience do you have? What size rocket are you building? What size is your field and what size motors are you looking to use?

Thank you for your response, I am building my first HPR for a Level Certification. The motor size is 29 mm in size and its a H H182R-14A motor. Would I need to get a ejection charge baffle?

 

[Raythain]

Thank you for your response, I am building my first HPR for a Level Certification. The motor size is 29 mm in size and its a H H182R-14A motor. Would I need to get an ejection charge baffle?

Is this a kit, or a scratch build?

You will need some sort of barrier between the ejection charge and the parachute, so that any hot particles don’t burn your parachute. The simplest way to do this is to use disposable wadding. This is some form of flame-resistant bio-degradable substance that acts as a single use protective barrier. For low power rocketry, Estes and Quest sell a treated paper product that works well. For high poser, I believe the typical product is spray in cellulose insulation, affectionately referred to as “dog barf”.

If this isn’t a kit, I suggest you just use some wadding. If it is a kit, build the baffle if the manufacturer included one, otherwise use wadding.

 

[Voyager1]

It is clear from your questions that you have had little or no experience in building and launching low and mid power rockets, let alone building a rocket for an L1 certification.

However, to answer your questions, as mentioned above, motors typically have an ejection charge that separates the upper and lower sections of the body tube and deploys the parachute after a defined delay. With motor ejection, no electronics are required to deploy the chute. With the larger HPR motors that don't have an ejection charge, you will need to use electronic deployment.

As also mentioned, you can use wadding, dog barf, Nomex blankets or deployment bags to protect the chute from the ejection discharge.

You would do well to attend some club launches and find a mentor, if that is possible.

 

[Zeus-cat]

Electronic ejection eliminates the need to trim your ejection delay charge. The altimeter handles the timing of when to fire the charge. Without electronics you need to trim that 14 second delay down to what you actually need, or you can seriously damage your rocket with a too long of a delay on ejection.

 

[b.wieting]

Good advice above, especially talking to club members. I've found even the gruff, grumpy ones love to talk rockets. John Coker's site (https://jcrocket.com/) is an excellent reference.

I used motor eject for both L1 and L2 for simplicity. Trimming eject time is critical, running a simulation (e.g rocksim) will guide than. Aerotech sells a trim tool (https://aerotech-rocketry.com/products/product_d208be9f-32da-778d-77e9-093c84bb0508).

With a bit of planning, you can insert an electronics bay later. I did that with both cert rockets. I prefer electronic deployment for the improved control. And it's fun to get the flight data. See eggtimerrocketry.com for some great options.

 

[-Slick-Ice]

There is more than one AT delay drilling tool. Make sure you get the one the instructions call for.

 

[MrPoopyPants]

Hello,
I have a few questions about rocket deployment. I am creating a single deployment rocket and was wondering if it would require a electronics bay with an altimeter and other components? Also, I'm a bit confused about how the parachute would deploy without any additional mechanisms. If anyone knows of any single deployment ground testing videos, I would appreciate it if you could share them.



Thank you!

Hi Mateosro, the motor you are using is ready to go for motor deployment - as mentioned by Slick Ice - you'll need (most likely) to drill the delay grain. I think that motor comes with 1.5G for the ejection charge - depending on how large your airframe is you may want to use more or less black powder. Since it's a L1 Cert and based on your question - I have to assume you have not used a disposable motor before. Don't feel weird - I did my L1 without this experience too. You'll need the universal drilling tool (Double check me on this - I think it works with 29mm motors). The most important thing to do is make sure you get the delay correct - don't want it going off too late or too early. Open Rocket is a free simulation software and theres a TON of information on how to use it out on the internet. If money isn't an issue use - Rocksim - I think it's 50 bucks and well worth it in my opinion - however they basically operate the same and do the same thing.

Go to the launch and someone will be happy and enthusiastic about helping you - but they can't do it for you - they will guide you. Talking about building the motor.

there's a lot of ways to protect the chute - Nomex is my preferred method.

Cheers and Good Luck with your L1 - I am going for my L3 so I understand how overwhelming a lot of this can be.

Just remember - they're really just model rockets and it's supposed to be fun and exciting

 

[Art Upton]

Besides all the other items mentioned , you really need this item as a Must Have, and pass it around your university members you mentioned in a previous post about using Open Rocket.

https://www.amazon.com/Modern-High-Power-Rocketry-Mark-Canepa/dp/1412058104/

 

[Ronz Rocketz]

Hello,
I have a few questions about rocket deployment. I am creating a single deployment rocket and was wondering if it would require a electronics bay with an altimeter and other components? Also, I'm a bit confused about how the parachute would deploy without any additional mechanisms. If anyone knows of any single deployment ground testing videos, I would appreciate it if you could share them.



Thank you!

That's what Eggtimer made the EZ-DD for. I bought one but haven't put it together yet. Contains the rocket, payload, and electronics you build yourself. There's plenty of YT videos showing how to solder the flight computer.

https://eggtimerrocketry.com/eggtimer-ez-dd-faqs/

I used motor eject for both L1 and L2 for simplicity. Trimming eject time is critical, running a simulation (e.g rocksim) will guide than. Aerotech sells a trim tool (https://aerotech-rocketry.com/products/product_d208be9f-32da-778d-77e9-093c84bb0508).

There is more than one AT delay drilling tool. Make sure you get the one the instructions call for.

The problem I've run into is that 29 RMS forward closures can't fit the UDDT and RDDT drills. For example, the closure on the 29/180 has a 1/8in hole and the UDDT and RDDT has a 1/4in drill. AFAIK, there is no 1/8in drill kit. Perhaps the 38 RMS closures have 1/4in holes but doesn't indicate on the website. To drill the delay in the 29 RMS, I've had to use the 1/32in per second rule.

One possible solution is to drill a 1/4in hole in the 29 RMS forward closure then use a washer with a 1/8in diameter hole.

 

[terryg]

Do not drill any holes. The Universal Drilling Tool is for DMS engines only. The RMS Delay drilling tool is used to drill the delay grain before you assemble the reload. Have an experienced flyer walk you thru your first assembly.

 

[Voyager1]

The problem I've run into is that 29 RMS forward closures can't fit the UDDT and RDDT drills. For example, the closure on the 29/180 has a 1/8in hole and the UDDT and RDDT has a 1/4in drill. AFAIK, there is no 1/8in drill kit. Perhaps the 38 RMS closures have 1/4in holes but doesn't indicate on the website. To drill the delay in the 29 RMS, I've had to use the 1/32in per second rule.

You drill the delay grains BEFORE you install the forward closure.

One possible solution is to drill a 1/4in hole in the 29 RMS forward closure then use a washer with a 1/8in diameter hole.

NO!

 

[Ronz Rocketz]

You drill the delay grains BEFORE you install the forward closure.

That's what I did by hand. Can't be done with the UDDT or RDDT.

NO!

I agree. I know the I285R (38/482) has a washer in the reload kit that is centered in the forward closure but was designed to do so. When I set the delay, I had to drill the hole by hand because the forward closure was 1/8in.

Do not drill any holes. The Universal Drilling Tool is for DMS engines only. The RMS Delay drilling tool View attachment 649561is used to drill the delay grain before you assemble the reload. Have an experienced flyer walk you thru your first assembly.

The RMS drill (aka RDDT) on the AT website is 1/4in.

https://aerotech-rocketry.com/produ...7642-85cb913cc1d5?_pos=4&_sid=0dc59f613&_ss=r

 

[cls]

I got tired of drilling delay grains, (and getting burn throughs!) so i bought 3-packs of several different RDKs.

I keep them sorted in small Ziploc bags in a big plastic box with dividers.

Eventually I've bought all the RDKs. Really handy for timing short times for oddrocs, super long for tracking high altitude birds, etc.

 

[TheTank]

That's what I did by hand. Can't be done with the UDDT or RDDT.


I agree. I know the I285R (38/482) has a washer in the reload kit that is centered in the forward closure but was designed to do so. When I set the delay, I had to drill the hole by hand because the forward closure was 1/8in.


The RMS drill (aka RDDT) on the AT website is 1/4in.
View attachment 649562
https://aerotech-rocketry.com/produ...7642-85cb913cc1d5?_pos=4&_sid=0dc59f613&_ss=r

There are no aerotech reload kits that you install a washer in the charge well and none that tell you to drill the delay grain through the charge well after the motor is assembled (in fact, they all tell you to drill it outside the reload and face the drilled side towards the propellant). If you got a washer in the I285R reload kit, the wrong accessory pack was included with your reload but I guarantee the instructions didn’t mention it.

Ive assembled hundreds of aerotech reloads from 29mm to 98mm and still look at the diagrams and instructions if it is not a reload I fly often. The delay trimming process for RMS and DMS are not the same.

 

[Art Upton]

That's what Eggtimer made the EZ-DD for. I bought one but haven't put it together yet. Contains the rocket, payload, and electronics you build yourself. There's plenty of YT videos showing how to solder the flight computer.

https://eggtimerrocketry.com/eggtimer-ez-dd-faqs/




The problem I've run into is that 29 RMS forward closures can't fit the UDDT and RDDT drills. For example, the closure on the 29/180 has a 1/8in hole and the UDDT and RDDT has a 1/4in drill. AFAIK, there is no 1/8in drill kit. Perhaps the 38 RMS closures have 1/4in holes but doesn't indicate on the website. To drill the delay in the 29 RMS, I've had to use the 1/32in per second rule.

One possible solution is to drill a 1/4in hole in the 29 RMS forward closure then use a washer with a 1/8in diameter hole.

View attachment 649559

You are to drill an RMS delay from the internal side when building it, Never thru the hole and don't drill open the hole in a RMS forward closure by drilling it out, this is by design.

The only motors you drill thru the hole are DMS motors, again by design.

 

[Steve Shannon]

The problem I've run into is that 29 RMS forward closures can't fit the UDDT and RDDT drills. For example, the closure on the 29/180 has a 1/8in hole and the UDDT and RDDT has a 1/4in drill. AFAIK, there is no 1/8in drill kit. Perhaps the 38 RMS closures have 1/4in holes but doesn't indicate on the website. To drill the delay in the 29 RMS, I've had to use the 1/32in per second rule.

One possible solution is to drill a 1/4in hole in the 29 RMS forward closure then use a washer with a 1/8in diameter hole.

Please, never suggest drilling a reusable forward closure. These two paragraphs demonstrate a misunderstanding of the process of adjusting a delay grain for an RMS motor. Please have a more experienced rocketeer show you how to adjust the delay for RMS motors using the appropriate tool or watch this video by Tim Van Milligan:

 

[cls]

I was asked to explain my post above (#15) better.

the idea is, get some of each of the RDKs. Sort by length. Add or subtract 0.033" per second that you want from the M (medium, 10 second) delay. use the next closest RDK.

example: H97-10 uses RDK08. but I want an 8 second delay. RDK08 is 0.719", subtract 2 * 0.033" is 0.660". Look at this list (HDK and RDK list), RDK 07 is 0.656, close enough!!!

example 2: my LOC Caliber flies 9000 feet on K185. It has dual deploy so doesn't need motor ejection. but I can't see it up there. So I put the longest 54mm RDK in that will fit: EFC will take RDK36, 1.175". lotsa tracking smoke waaaay up there.

the other advantage of carrying a bunch of delay grains is you can replace spotty ones, like in old reload kits, red line reloads that didn't have the delay in foil, etc.

 

[Ronz Rocketz]

Please, never suggest drilling a reusable forward closure. These two paragraphs demonstrate a misunderstanding of the process of adjusting a delay grain for an RMS motor. Please have a more experienced rocketeer show you how to adjust the delay for RMS motors using the appropriate tool or watch this video by Tim Van Milligan:

Cool. Thanks for the video. I asked this before in a different thread and got a different explanation. In fact, I believe there are many rocketeers who misunderstand the difference between setting the delay on the RMS and DMS. I apologize for my limited understanding and lack of experience with reloads.

Now that I think of it, I believe the metal washer was included in the DMS kit before pouring the powder into the well.