Complete Newbie - Clusters and Clamps and Control (Oh No!)

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Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby dmeeze » Tue Mar 20, 2018 8:46 pm

Hi there. This thread is where a complete newbie asks lots of super dumb questions and you all nod quietly, backing away, or facepalm.

So intros. I did electronic engineering back in the dark ages of the 20th Century at QUT, alongside a bunch of aerospace/avionics students, so i'm in no way naively asking these questions. My marks in control systems subjects were... umm... well, i graduated. :) So When i watch spacex launches, I can seriously appreciate how hard almost every detail of them is.

My first ever model rocket was helping my kids fly a pair of fly-it-launch-it A motors at one of QRS' open days. At that meet, they won the raffle of an SCR 56er kit and we flew "Christmas Rocket" (kids chose colours and names) at QRS a few times on the included B6's.

Unfortunately on the weekend Christmas Rocket made a particularly powerliney landing (below), so I am now in search of a project. Obviously i can build a kit, or work through the fun of simming and scratchbuilding something cool, but I started to wonder about making a SpaceX F9 or F9Heavy. (Obviously not as a first project, just as a maybe something interesting!). Which led to learning about clustering, and control, and so on.

So.
1) I understand there are some rules around control/guidance for model rocketry in general. I'm well aware of the reasons and would never ever want to build tech which could be misused, but i'm finding it hard to find any clear documentation on where the official lines of "don't" are. I understand this is a delicate question and I am 100% on the side of not ever building misusable tech.
2) Thinking through clustering I wondered about whether "clamping" the rocket until all engines have started has ever been looked into. I can't find much on this at all. Is it clearly ludicrous?
3) on recovery (especially for the QRS cedar grove site) - has anyone ever tried using one of the BTLE short range "Tile" devices as cheap recovery tracking? https://www.thetileapp.com/en-us/products/sport? clearly gps tracking is better in almost every way, but after spending half an hour or so looking for a friend's rocket in that cornfield, I wondered about something audible.

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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby CATO » Wed Mar 21, 2018 6:05 am

Welcome to the forum “dmeeze”.
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby OverTheTop » Wed Mar 21, 2018 8:03 am

Welcome to the forum dmeeze.

In relation to guidance you will need to check with the AMRS rules, or get direct clarification on their stance on this, since you are with QRS. In Tripoli Rocketry Association guidance is allowed, as long as it is not controlling the rocket towards a target. I choose to use the wording "vertical trajectory system" to make it a little less offensive to people who are not rocketry inclined. There are a few people experimenting with this sort of thing. There is even a small commercial system for thrust vectoring.

I have a VTS that is going to fly this year. Here is where I am at:
viewtopic.php?f=56&t=5324

Remember to always think safety with these things (and rocketry in general :D ). I will be flying with double the standard distance and not engaging the active guidance until after boost. That ensures two things: That the rocket is at altitude (think safe distance) from everyone, and that the control systems are working with accelerometers and gyros that are not pegged due to the boost acceleration. Remember, design for off-nominal situations :wink:
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby krusty » Wed Mar 21, 2018 9:10 am

HI dmeeze

The tile devices are neat - but won't work for what you're wanting - they're not GPS :shock:

They work by 'crowd sourcing' - everyone who has a Tile has the Tile app installed. As you move around, your phone picks up and transmits the location of every tile that the app detects - not just yours - to a central database.

They run on Bluetooth and are limited to 100m under ideal conditions. So great for an area with lots of people who all own a tile, but not so good for a rocket in the middle of a park!

Something like this may work - https://www.ebay.com.au/itm/302544717575 but you'll need to purchase a SIM and mobile plan to go with it. And depending on where you're flying, you may not have mobile reception!

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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby SpaceManMat » Wed Mar 21, 2018 9:28 am

As OTT says we would not use the word guidance this would indicate the rocket is designed to head to a particular location. If you do this then you’ve crossed a line and are building something that may be considered a weapon and that’s a criminal offence and you’ll get yourself into a world of trouble if you do that. Generally I like the word stabilised, what we want to do is to make sure our rocket is ascending vertically and usually without spin. The aim is of course to maximising height rather than go to a particular location.

I’ve not heard of anyone using clamping to make sure all engines light in a cluster. You would have to either have sensors on each motor or something like a strain wire that breaks above a set value.
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby crom » Wed Mar 21, 2018 10:46 am

More info can be found at the AMRS web site: https://rocketry.org.au/safety-information/

A lot of the items you riased are covered in the AMRS / TRA L2 study guide materials.

For me the statement on the Tile website summarises it's usefulness: "Sport was designed with our most powerful range, reaching up to 200 feet."
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby krusty » Wed Mar 21, 2018 11:01 am

crom wrote:For me the statement on the Tile website summarises it's usefulness: "Sport was designed with our most powerful range, reaching up to 200 feet."


60 meters ;) Outstanding range! LOL

I'd like to think that in most cases, if you're within 200 feet of your rocket, you'd be able to see it.. Yes, yes.. I know, not always - but usually ;)

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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby kopius » Wed Mar 21, 2018 12:11 pm

Hi Dmeeze,

Just a quick clarification on wording etc.
Guidance = DO NOT DO THIS!
Stability Control = Absolutely!

The trust vectoring device, fin control and other items are all for stability control.
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby drew » Wed Mar 21, 2018 1:00 pm

kopius wrote:Hi Dmeeze,

Just a quick clarification on wording etc.
Guidance = DO NOT DO THIS!
Stability Control = Absolutely!

The trust vectoring device, fin control and other items are all for stability control.


The way I like to look at it is that mature stability control system can provide a safer flight when compared to a rocket without it. :)

As for question 2, I think that's problematic. Most hobby motor burn times are quite short so a hold down will seriously impact the vehicle flight performance. I think the better avenue is a ClustoMatic style product to attempt to fire the ignitors in unison. Have a look at some of PK's old threads on that subject, there's some good info in them.

Circling back to question 1, you might want to check out BPS and his thrust vectoring control system. It's limited to small motors but his TVC system does look like a lot of fun.

https://bps.space/

Watching his Narcon 2018 presentation I was amused when he mentioned that they looked into incorporating a fin stability system with the first Signal flight computer but stopped when they realised how complex it was! It gives me some appreciation regarding the difficulty that task entails and respect for the folks that are developing those systems like OTT, Jim Jarvis, and others.
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby Digit » Wed Mar 21, 2018 8:21 pm

Again welcome to the forum mate. It’s been a real pleasure to witness firsthand someone go from our FITI program to a full fledged member.

As several people have already mentioned, terminology is your friend. Missiles are usually by design very unstable so that they can be rapidly steered or ‘guided’ via use of canard fins etc (small fins you see at nose of a missile controlled by powerful servos) and ultimately with intent to impact a target. Where as a rocket is unguided and inherently stable, but may benefit from a little extra ‘stabilisation’, be it thrust vectoring, spin stabilising etc to aid a perfectly vertical flight. 8)

When it comes to cluster motor ignition I have had textbook success with two very different methods as can be seen in my build threads here:

Igniting seven motors simultaneously with a black power flash pan:
viewtopic.php?f=10&t=5595

and

Igniting four motors simultaneously with SCR electronic igniters:
viewtopic.php?f=10&t=5929
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby OverTheTop » Wed Mar 21, 2018 8:59 pm

Check out this build for a great cluster ignition method. Sort of a refined version of "flash in the pan" ignition.
IMG_5256.jpg


www.rocketryforum.com/showthread.php?13 ... 1-50-build

Should work great for BP motors.
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby dmeeze » Thu Mar 22, 2018 7:46 am

Thanks all!

Yes, "stabilisation" not "guidance" is entirely what i meant although post apogee "please don't drift onto the powerlines" control does have some appeal :)

The Soyuz build looks fascinating. I have in my head to see what can be done with clustered low-power motors F9 style. time to do some math and work out how ridiculous and naive that idea really is.

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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby dmeeze » Thu Mar 22, 2018 7:52 am

Oh, and that cluster ignition looks awesome, time for me to start looking into an explosives license i guess :)

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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby drew » Thu Mar 22, 2018 9:40 am

dmeeze wrote:although post apogee "please don't drift onto the powerlines" control does have some appeal :)


Maybe you can design a guided parachute recovery system?
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Re: Complete Newbie - Clusters and Clamps and Control (Oh No!)

Postby dmeeze » Thu Mar 22, 2018 11:44 am

Seems very cool. I suspect making it remote controlled instead of autonomous would seem to be the safest bet in not going near any of the grey areas.


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