Wireless Launch Control

The Rocketry Forum

Help Support The Rocketry Forum:

Al_M

Member
Joined
Dec 30, 2021
Messages
5
Reaction score
10
Location
Michigan, USA
I am returning to LPR after a 40-year absence, flying RC aircraft. As such, I have a lot of unused RC equipment gathering dust. One observation upon my return is the apparent lack of technical advance in the area of launch control equipment. Please correct me if I am wrong.
I propose building a witeless launch control system, consisting of an RC spread spectrum transmitter, and a small box placed in close proximity to the launch pad. The box would contain the receiver, which is bound to the transmitter, a servo that actuates a normally-open microswitch, a 4.8 to 6 volt airborne-type battery pack to power the receiver and servo, and a 3-cell (11.4 volt) lipo pack to do the ignition chores. Short leads would exit the box with small alligator clips to attach to the igniter.
This would eliminate the long ignition wires laying on the ground, which I consider a trip hazard.
In the absence of a keyed safety, two or more channels could be employed, and the respective servos and microswitches could be wired in series.
I don’t know if this idea has been tried before, or if it would meet current NRA/TRA safety standards. So I am floating this idea as a trial baloon.
Another motivating factor is the ridiculous price charged for launch control devices from certain suppliers.
Comments, no flames please, are welcome.
 

Scott_650

Well-Known Member
Joined
Sep 16, 2015
Messages
1,541
Reaction score
1,052
Location
Louisville OH

 

prfesser

Well-Known Member
Joined
May 7, 2017
Messages
2,728
Reaction score
3,506
Location
Murray, KY
Who is the customer? If it's being vended to individuals the price should be in keeping with the customer. Or might it be sold as a kit? After all, we're rocketeers! 😁

As someone who is almost-completely-unfamiliar with modern electronic design, I'd suggest making sure that it's a turnkey system for dumbos like me. If I have to program a device to use it...I won't buy it.

Best -- Terry
 

BEC

Well-Known Member
Joined
Feb 19, 2009
Messages
4,440
Reaction score
1,334
Location
Auburn, WA
Frank Burke (@burkefj) has some experience using a channel on his transmitter to launch his rocket gliders. He may have a thought or two on this rather than trying to redirect the OP to an entirely different approach.


That said, for LPR/MPR it is really hard to beat the Estes PSII controller with a small (1100+/-200 mAh 3s Lipoly inside). Yes, there are 30 feet of wire, but it's light, simple to set up and tear down, and if you already have the battery the only thing you need to do is adapt it to the little orange 2-pin JST connector. The controller itself can be had for $30-$45 depending on where you get it. https://www.acsupplyco.com/estes-mo...essories/estes-pro-series-2-launch-controller. It also is a lot more rugged for toting to the field and back than an RC transmitter.

Oh, and Al, watch out: coming back to the hobby after being away that long can be life-changing! I haven't built an airplane now in over a dozen years....but I have LOTS of rockets.
 
Last edited:

burkefj

Well-Known Member
Joined
Jan 27, 2009
Messages
3,877
Reaction score
1,792
There can be some glitching of servos when you power up the receiver so I would make sure that you have a local inline safing plug for when you actually arm the box at the pad, and after turning on your transmitter and make sure that the box is far enough away from the pad that if there was some accidental ignition you're not right next to the rocket. I've used electronic switches connected to a receiver to do this but unfortunately the electronic switch had a failure mechanism that resulted in a complete short of the outputs so when I armed the box it actually fired the motor and there was no indication that anything was amiss in the electronic switch indication lights. I think a servo and micro switch should be fine just make sure you're not passing high current through the micro switch, ie ise the switch to fire a relay.. Normally according to the nar rules you're supposed to have a momentary on switch for the firing circuit so even if you have a separate channel for arming if you're not using a momentary on switch that's not officially kosher to fire the circuit you want something that when you let go of the switch will return to off.

In my case I simply made an elastic band that went over the throttle stick so I'd arm the system using a separate switch and channel and then I'd move the throttle stick up for fire and the elastic would pull it back off after I let go.
 

Scott_650

Well-Known Member
Joined
Sep 16, 2015
Messages
1,541
Reaction score
1,052
Location
Louisville OH
Some great stuff here! I know it’s still a traditional wired controller but I have to second Bernard’s recommendation - the Estes #2240 PSII Controller is a great way to get back into the hobby without dealing with the rather marginal performance the Electron Beam controller. Might be a good way to get going while working out how you want your R/C-based setup to function. I can’t comment much on Frank’s post since I’m not an R/C guy but I love the super simple solution to needing a momentary launch switch!
 

burkefj

Well-Known Member
Joined
Jan 27, 2009
Messages
3,877
Reaction score
1,792
Since my scare with the e-switch failing, I've gone back to my wired solution with a heavy duty horn button with a series blade fuse that I velcro to the side of the xmitter and can hit with my thumb for self controlled launches now....


Some great stuff here! I know it’s still a traditional wired controller but I have to second Bernard’s recommendation - the Estes #2240 PSII Controller is a great way to get back into the hobby without dealing with the rather marginal performance the Electron Beam controller. Might be a good way to get going while working out how you want your R/C-based setup to function. I can’t comment much on Frank’s post since I’m not an R/C guy but I love the super simple solution to needing a momentary launch switch!
 

Titan II

Well-Known Member
Joined
Aug 23, 2013
Messages
1,259
Reaction score
397
I use a 10 channel transmitter. I have a removable key cut-off switch to power the transmitter. Two channels, each with a toggle switch, operates two servos that operate two microswitches in series. A momentary pushbutton operates a relay in series with the two microswitches. Thus, it takes three operations to launch once the transmitter is powered on. Two switches to supply power to the relay, and a momentary pushbutton to operate the relay. Very safe and very easy.
 

RocketRev

Well-Known Member
Joined
Jul 25, 2012
Messages
421
Reaction score
298
This is certainly not a flame front coming at you, but you said, "Please correct me if I am wrong." And you said you've been out of it for 40 years. So when it comes to what you see as an "apparent lack of technical advance in the area of launch control equipment," I don't think you've looked in the right places. Bdale Garbee with his Telelaunch system and Dan Fox and I with our Wilson F/X launch sysetms would certainly disagree with you on your assessment of the "lack of technical advancement." But I will also admit that Telelaunch and Wilson F/X were both designed with the idea of providing launch systems to clubs, not for individuals. Wilson F/X does produce launch systems for individuals, but they are turnkey hard-wired and wireless launch systems for those looking to use it right out of the box.

So, if you are looking for a way to adapt some components from your RC airplane equipment, go for it. But as Burkefj mentioned, the system on/off momentary glitching of servos in an RC system might not mean much of anything other than an insignificant flutter in an aileron. In a launch control ignition system with nichrome wire, pyrogens, ematches, etc., and solid feul propellant, it can be disasterous. I am not saying that your current equipment cannot be adapted into a safe launch system, but I am saying that it may be more difficult that it might appear, particularly the "safe" part. I've been at more than a few "missfire alley" launches were I did not feel safe watching some of the homemade launch systems that were in use.

Then there's the question of a removable key switch in order to safe the launch system. Both NAR and TRA require them at launches for all launch systems. I don't recall anybody mentioning them in this thread so far, so I thought I'd speak up now so that it's not forgotten. And I'm sorry, but your attempt to use two non-removable keyed switches to replace the one removable key device will not fulfill the requirement for a removable key switch. The removable key switch is required so that the user can remove the key and take it with them while at the pad in order to keep anybody else from arming and firing the system in the operator's absense.

Next come the questions about frequencies. Please tell me if I'm wrong, but are the frequencies of RC airplane equipment available to be used by rocket launch equipment? What happens if some guy with his rocket motor boosted RC glider comes to the same launch as you? It might be unlikely that he or she is using the same frequencies as your launch system, but unlikely with a launch sysetm is not safe enough. Wilson F/X wireless systems are all doubly encrypted to keep even the possibility of this from ever happening. Will your RC component based rocket launch system be encrypted to safe them from cross system interference? If you can't know that they are safe, then they are not. Then there are the RC folks that you have apparently left behind. Will they want you, a rocketeer coopting thier RC frequencies for your rocket flying? I doubt it very much.

As long as you get past the other problems and you are only flying low-power rockets/motors, things might again be just fine. But what if you decide to go for mid-power rocketry or eventually high power rockets and motors? A transmitter/receiver pair might do just fine up in the air at 1000 feet away. But up in the air is a world of difference from a launch system sitting on the ground having to transmit and recieve thru all sorts of ground clutter.

Then you mentioned, "Another motivating factor is the ridiculous price charged for launch control devices from certain suppliers." I'd love to see the actual finished price tag of your known to be safe and longitudinally tested system. And no, "but I already own it" does not count. The only fair way to assess the price for something is to get a current price for the components that you are modifying along with the costs for all the parts that you have to add to make it do what it needs to do in order to be a safe rocket launch system. And don't forget labor costs. Any other price comparrison is not worth looking at and incredibly questionable. I'm a tinkerer myself, so I understand the large group of DIY folks in this hobby. For instance, I doubt that I've built a stock rocket kit in 40 years. I don't even leave Estes rockets un-modified.

Lastly, I will just say this, "You get what you pay for" and a Wilson F/X launch system comes with a 10 year warrantee against manufacturing defects.

That's it for now.

Brad, the "Rocket Rev.," Wilson
CCBW of Wilson F/X Digital Launch Control Systems
that's "Chief Cook and Bottle Washer" in case you were wondering
 

BEC

Well-Known Member
Joined
Feb 19, 2009
Messages
4,440
Reaction score
1,334
Location
Auburn, WA
Next come the questions about frequencies. Please tell me if I'm wrong, but are the frequencies of RC airplane equipment available to be used by rocket launch equipment? What happens if some guy with his rocket motor boosted RC glider comes to the same launch as you? It might be unlikely that he or she is using the same frequencies as your launch system, but unlikely with a launch sysetm is not safe enough.

This was more of an issue before the virtually complete takeover of RC by spread spectrum 2.4 GHz radio systems, which the OP mentioned he wanted to use. No more frequency flags. Heck, since there are at least three or four "standards" for how the data are encoded on these things, interoperability is arguably much harder now than it was in the 72 MHz days where a carrier on a given frequency could cause an issue with a receiver on the same one, regardless of modulation type. With spread spectrum (which I suspect you understand better than I do) this is generally not an issue.

For the OP, I stand by my recommendation for a good, reliable, and not expensive wired system for LPR/MPR flying, and the Estes PSII controller is a value standout there.
 

BEC

Well-Known Member
Joined
Feb 19, 2009
Messages
4,440
Reaction score
1,334
Location
Auburn, WA
Next come the questions about frequencies. Please tell me if I'm wrong, but are the frequencies of RC airplane equipment available to be used by rocket launch equipment? What happens if some guy with his rocket motor boosted RC glider comes to the same launch as you? It might be unlikely that he or she is using the same frequencies as your launch system, but unlikely with a launch sysetm is not safe enough.

This was more of an issue before the virtually complete takeover of RC by spread spectrum 2.4 GHz radio systems, which the OP mentioned he wanted to use. No more frequency flags. Heck, since there are at least three or four "standards" for how the data are encoded on these things, interoperability is arguably much harder now than it was in the 72 MHz days where a carrier on a given frequency could cause an issue with a receiver on the same one, regardless of modulation type. With spread spectrum (which I suspect you understand better than I do) this is generally not an issue.

For the OP, I stand by my recommendation for a good, reliable, and not expensive wired system for LPR/MPR flying, and the Estes PSII controller is a value standout there.
 

Titan II

Well-Known Member
Joined
Aug 23, 2013
Messages
1,259
Reaction score
397
Then there's the question of a removable key switch in order to safe the launch system. Both NAR and TRA require them at launches for all launch systems. I don't recall anybody mentioning them in this thread so far

Than you obviously did not read my post directly above yours.

It is also obvious that you have little knowledge of RC systems, as it can be accomplished in a completely safe manner.

Finally, the overall tone of your post is hostile and not conducive to a best business practice.
 

RocketRev

Well-Known Member
Joined
Jul 25, 2012
Messages
421
Reaction score
298
Hello Titan II,

I'm sorry that I did not catch your reference to the removable key switch. As they say "My bad."

I know next to nothing about current RC flying systems and would be happy to be educated. My knowlege of RC stuff is 40 years old long before current spfread spectrum tech, and I would certainly hope that its outdated.

And if you read my post you will note that on several occassions I said that I'm sure using RC stuff to build a reliable safe launch system can be done safely. All I said was that it might not be as easy as one would think. And I've been to recent RC events and watched when controllers were powered up, and seen flutters on control surfaces on airplanes. That's a dead give away that there is power-up leakage going on and leaking voltage can fire igniters. So spread spectrum is great, but its what its hooked up to that worries me. Servos are not igniters and a momentary voltage leak can light one in a hurry.

As to the overall tone of my email? I'm sorry if you're hearing something that I am definitely not intending. I had and have no intention whatsoever of conveying any hostility. And I'm sorry if anything I typed made you think that was my intention. I think its the medium of a forum that can lead to someone reading emotional tone into a post that is not meant by the postee. In our current culture, it is so easy to go from dissagreement to hostility. I may dissagree with something, but I and definitely trying to avoid becoming disagreeable while I do it.

Let me know when and where I'm sounding hostile and I will try to do better.

humbly hoping to not convey any hostility,
Brad, the "Rocket Rev.," Wilson
 

Buckeye

Well-Known Member
Joined
Sep 5, 2009
Messages
2,991
Reaction score
755
The NAR HPR Safety Code doesn't mention a safety interlock that is "removable", but rather "not installed."

My launch system will have a safety interlock that is in series with the launch switch that is not installed until my rocket is ready for launch and will use a launch switch that returns to the “off” position when released.
 
Joined
Dec 19, 2011
Messages
231
Reaction score
132
Location
Lebanon,IN
You could put a removeable switch somewhere in the circuit in the pad box. Remove it as you approach the pad, then replace it as you walk back to the range head.
 
Joined
May 8, 2020
Messages
2,943
Reaction score
2,698
Location
Oahu, Hawaii
The NAR HPR Safety Code doesn't mention a safety interlock that is "removable", but rather "not installed."

My launch system will have a safety interlock that is in series with the launch switch that is not installed until my rocket is ready for launch and will use a launch switch that returns to the “off” position when released.
That’s what I read. However the Tripoli HPR code says “The ignition system shall contain a removable safety interlock device in series with the launch switch.” Can a servo mechanism count as a “removable” device? I would think it would need a clearly visible indicator when the interlock was active.
 

RocketRev

Well-Known Member
Joined
Jul 25, 2012
Messages
421
Reaction score
298
I believe Brad was referring to the OP’s suggestion to use series servos to perform the role of safety key switches. That would be a no-no!
This is correct. I don't see how in series servos can be a safety switch unless one of them is removable.
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
Joined
Feb 3, 2012
Messages
5,089
Reaction score
2,861
Using a servo to close the circuit is no different than using a relay to close the circuit, if it's done at the pad box, however it needs to return to the open position in the absence of the launch signal. In any case, there needs to be something removable that electrically prevents the launch switch from being actuated, at the control head.
 
Top