Are wireless Launch controllers permitted?

I have some surplus Receivers (from garage door operators) and would use them if this kind of launcher is allowable. The launch process would go like this:

1. momentary switch energises a delayed time off relay (relay 1) providing power to the 1st Rx (Rx1).
2. after moving away from launch area, button 1 on the Tx trips Rx1 providing power to the 2nd Rx (Rx2).
3. button 2 on Tx trips Rx2 giving power to the igniter.
4. Whether launched or not, at the end of the timed period, relay 1 is de-energised, cutting power to Rx1.

Any comments/suggestions welcome. Thanks in advance.

As far as i know they arn't prohibited...BUT...

Its not a good idea, especially with things like the surplus garage door openers you mention.
There is a significant risk, especially if all you are sending is a single high data pulse, that the rocket could be launched by a burst of interference, which for those remotes (i'm assuming they are 433Mhz) is significant, for example I'm experimenting with 433MHz modules at the minute, if they were in my rocket a data burst from the rocket could cause an unintended launch.

If you were going to create a wireless controller, the following is the minimum i would consider to be safe:

1. Local isolate switch at the pad is switched to fire
2. After moving away launch prep button is pressed.
3. At this point a microprocessor in the launch controller would transmit a launch prep codeword to another micro at the pad
4. The pad micro would perform error checks on the codeword
4a. If the codeword checks out it is transmitted back to the launch controller
4b. Doesn't check out - error message transmitted
5. The launch controller error checks the received codeword
5a. Checks out - Link status displayed as confirmed and user asked for confirmation of launch
5b. Doesn't check out - Error message displayed

If at this point the controller is waiting for confirmation of launch
6. User presses launch enable button
7. Launch Codeword is transmitted to the Pad
8. Codeword is error checked
8a. If the codeword checks out it is transmitted back to the launch controller
8b. Doesn't check out - error message transmitted
9. The launch controller error checks the received codeword
9a. Checks out - Codeword retransmitted to the pad
9b. Doesn't check out - Error message displayed
10. Pad error checks codeword
10a. Checks out - Provides power to pad and launches rocket - Confirmation of launch enable transmitted to the launch controller
10b. Doesn't check out - Launch abort transmitted.

If you didn't guess from the sequence, if any part of the sequence is skipped, or a transmission causes an error, the sequence must be started from the beginning.

I would further expect the codewords to be a minimum of 8 bits long and have a hamming distance of 6 (ie: If you had code a = 11111111 then code b might = 00000011. The hamming distance is the minimum number of bits that must be changed for the codeword to appear as a different codeword, so in the previous example 6 bits would have to be flipped by interference before it could look like another codeword.)

Finally i would expect that the radio link would be a device such as an Xbee that has intelligence in it to cope with interference.

That as i said would be the minimum i would expect. There would be other ways that could enhance it, such using multiple 16 bit codewords, encoding the codeword for error checking, encoding twice and using an interleavered code (http://en.wikipedia.org/wiki/Interleaving)

I'm sorry if this sounds over the top, but the last thing i want is some interference causing a rocket to go off in someones face. PK's MADs have a 2 minute on - arming delay to prevent ejection charges firing in peoples faces, as we see happen all too frequently.

However all that being said, If you wanted to design a system that was safe, and replaced the wires, go for it, there are alot of people on here with experience programming or in communications that would be more than willing to help.

Regards
-Knight

Thanks Knight, but all that is over my head. I'll put the Rxs back in the junk box and invest in a launcher.

Knight, second thoughts -
Frequency is in the region of 300Mhz judging by aerial length (1/4 wavelength) - I will contact the manuf. to confirm frequency and code variations.
Yes, unintended reception is possible but I think improbable and given there will be two discreet Rx's, an unintended launch would be improbable times two.
If there were a short cable run (several metres) between controller and launch pad and an isolation switch for each of the igniter circuit and the power supply, would this be considered safe?

I only consider this because I have the Rx's (and can scrounge enough bits to make it all work) (and dislike rolling up wire!)

Re: igniters - Would 2amps @ 12v for 0.5 second give reliable ignition?

Thanks.

Look realistically the chances are low that in any configuration that you will have an uncommanded launch.
The procedure I wrote above is also not perfect, it just has a much lower risk than a simple wireless switch.
I am simply trying to give you something that you could do to produce a safer system.

I can not stop you using an system, all i can do is try and provide you with the guidance that will help you produce a good system.

To the other more established members, am i being too over the top with the sort of system i am proposing?

Hi Guys

Have you ever had look at some of the Pyro controllers available out of China. They are programmable, Encrypted and some have ranges up to 2 km. (we won't however even discuss the RF issues here though). They are very low cost (approx $AUD 100) and are the mainstays and "stock of trade" for many Australian Pyro firms.


One of Many Wireless Controller Options Available

Please feel free to exercise you own due diligence and perhaps investigating some of these options further.

Click here for link to Ebay Store for Wireless Pyro Controller Supplier - Hong Kong

Tarp

PLEASE NOTE:

I should mention though, that most of these devices are single gated and will some form of addition switching between the power supply and at activation button to conform with most LPR & HPR Safety Codes for the use of only Double Gated Controllers.

Tarp