When Do You Hook Up Clips?

[Ryan S.]

I have always attatched my clips outside the rocket as I have had live clips before that could have fired a rocket in my face. I am just wondering what the common practice is

 

[DaveCombs]

https://www.rocketryforum.com/showthread.php?t=37907

HUGE discussion about this.

 

[deandome]

https://www.rocketryforum.com/showthread.php?t=37907
HUGE discussion about this.

Actually, that's another question; do you install the ignitor in the motor before or after you mount the rocket on the launcher.

Ryan's on-board with installing the ignitor after the bird's on the pad. But he's asking about...and kinda advocating...connecting the controller wires/clips to the ignitor & THEN installing the ignitor in the motor!!!

I guess if you have a safe launch system, that won't be unsafe...but I think it'd make proper installation more difficult & could lead to bad starts.

I'm just freaked out that he thinks it's in the realm of normality for wires to be live without someone actively pushing 2 buttons/holding in a spring-loaded safety key (I forget the term for the type of switch where you can't just stick a key in a hole or sum'pin..you have to PUSH it in while then pushing a launch button).

 

[DaveCombs]

Actually, that's another question; do you install the ignitor in the motor before or after you mount the rocket on the launcher.

The discussion thread included plenty of posts that spoke to his question as well.

 

[DaveCombs]

I'll repeat here what I posted in the other thread...

1. I pre-load BP igniters away from the pad, and so by extension I attach the leads with the igniter loaded.

2. I install AP igniters at the pad, and so again, by extension, I attach the leads with the igniter loaded.

3. I ALWAYS touch the launch clips together before attaching them to the igniter leads. If there is an arc or spark, the line's hot and I won't attach them to the igniter until that situation gets resolved.

To summarize for the sake of the question, I vote for the second choice: my igniters are in the engine when I attach the launch clips.

 

[DaveCombs]

My BP sequence, for clarity:
Prep the airframe (pack/wadding or barf/nose cone check)
Install engine
Install igniter
GET INTERLOCK KEY FROM LAUNCHER
Walk to pad
Put rocket on launch rod
Attach clips
Walk away
etc...

High power is a different ballgame, and I treat it with all due respect including shunting the igniter until after I've verified that the leads are cold.

 

[DaveCombs]

Ryan: I think your practice of hooking the leads to the AP igniter when it's outside the motor is actually very sensible. I just don't do it that way. And your firearms analogy is spot on - the only real safety any gun has is the behavior of the person holding it.

 

[tquigg]

Several years ago I seem to recall a story detailing an incident in which a subject hooked up the leads to an igniter in a rocket motor on the pad. He heard a "pop" and then the distinct "whoosh" of the big HPR motor coming up to pressure. He had just enough time to fall backwards away from the rocket before it took off. He had a bird's eye view of the rocket taking off literally overhead.

The clips were hot. When he completed the circuit, the igniter lit.

Upon further investigation, they found a faulty relay in the system. The last rocket that had been launched from that pad had apparently had a particularly stubborn igniter, and the LCO had layed on the launch button for many seconds before the igniter lit. In doing so, he had melted the relay contacts into the closed position. I don't understand how this worked in relation to a removable arming key. I'm no electician.

Every since then, I too, tap the clips together and watch for a spark.

 

[KermieD]

The thread has been cleaned up from some posts insulting other members directly and indirectly. Anyone who's had a post pulled, please feel free to repost any content that's pertinent to the topic at hand.

 

[Nerull]

Actually, that's another question; do you install the ignitor in the motor before or after you mount the rocket on the launcher.

Ryan's on-board with installing the ignitor after the bird's on the pad. But he's asking about...and kinda advocating...connecting the controller wires/clips to the ignitor & THEN installing the ignitor in the motor!!!

I guess if you have a safe launch system, that won't be unsafe...but I think it'd make proper installation more difficult & could lead to bad starts.

I'm just freaked out that he thinks it's in the realm of normality for wires to be live without someone actively pushing 2 buttons/holding in a spring-loaded safety key (I forget the term for the type of switch where you can't just stick a key in a hole or sum'pin..you have to PUSH it in while then pushing a launch button).

He didn't say it was normal, he said it has happened.

You don't take precautions for things that are 'normal', you take precautions for the unexpected.

I know of several other times rockets have gone off while people were at the pad. It happens. You may prefer your theories instead of reality, but you can't deny that multiple people have been put in danger when an igniter fired while they were at the rocket.

 

[DaveHein]

At this time there are actually 3 people that said that they hook up the clips first. I think this is very dangerous. What happens if the clips become live while your putting the igniter in? BP motors light quickly, and this could happen while your pushing the little plastic plug in! AP motors take longer to come up to pressure, but I wouldn't want to be inserting the igniter while this is happening.

I think it is much safer to hook up the clips after the igniter has been inserted. As others have mentioned you should touch the clips together first to look for a spark. If your really concerned about it you could use your own set of clips connected to a short piece of wire, which are then attached to the real igniter clips when your ready.

 

[Nerull]

Fried relays are one of the big causes. I've also heard of at least one wonky wireless system that would occasionally do it, not sure on the details, though.

Relays are too often used with no safety systems in between the pad battery and the rocket. The key is in the controller back at the LCO table, and its assumed that if the relay isn't getting power it can't activate.

I'd hope more clubs are at least using a simple toggle switch at the relay box. (NSL had toggle switches for the high power pads, IIRC) Having the igniter fire while your a few feet away is bad, but a lot better than while your under it.

 

[ben]

Fried relays are one of the big causes. I've also heard of at least one wonky wireless system that would occasionally do it, not sure on the details, though.

Relays are too often used with no safety systems in between the pad battery and the rocket. The key is in the controller back at the LCO table, and its assumed that if the relay isn't getting power it can't activate.

I'd hope more clubs are at least using a simple toggle switch at the relay box. (NSL had toggle switches for the high power pads, IIRC) Having the igniter fire while your a few feet away is bad, but a lot better than while your under it.

One thing I think would be good is at the HPR pads alot fo clubs have pad boxes. After the realy trips (its launched) it flips a switch. The relay cannot get power or trip till that switch is flipped again. So you need to do that on your way away from the pad. EVEN incase something happened with that switch to were the relay was on when it was switched, most pad boxeas are 10-15 feet. Away even for an O or P motor safer then right at it.

Ben

 

[tquigg]

Fried relays are one of the big causes. I've also heard of at least one wonky wireless system that would occasionally do it, not sure on the details, though.

Relays are too often used with no safety systems in between the pad battery and the rocket. The key is in the controller back at the LCO table, and its assumed that if the relay isn't getting power it can't activate.

I'd hope more clubs are at least using a simple toggle switch at the relay box. (NSL had toggle switches for the high power pads, IIRC) Having the igniter fire while your a few feet away is bad, but a lot better than while your under it.

Our launch control system was designed and built by an aerospace engineer who works for Boeing. 24 pads, arming key that has a capture feature (when armed or "hot" the key cannot be pulled out of the panel.) Can only be pulled when the key is turned and the panel is turned off. Have relay boxes at each cell of pads to test continuity with. All low current igniter safe.

But I still tap the clips to check for a spark before hooking them up to the igniter. If it's one thing I've learned from 25 years in law enforcement....

"Feces Occurs" :surprised:

 

[jadebox]

I'm not certain, but I think the launch system at our launches has a beeper in the relay box that beeps while the relay is closed. If the relay were to weld shut, the beep would be a warning.

I am also in the habit of touching the clips together to look for a spark.

-- roger

 

[Tom Riddle]

One thing I think would be good is at the HPR pads alot fo clubs have pad boxes. After the realy trips (its launched) it flips a switch. The relay cannot get power or trip till that switch is flipped again. So you need to do that on your way away from the pad. EVEN incase something happened with that switch to were the relay was on when it was switched, most pad boxeas are 10-15 feet. Away even for an O or P motor safer then right at it.

Ben

Right line of thinking, but you are still 10' away when you 'arm' the pad. When launch controllers evolved to have the battery at the pad and the launch switch was replaced with a relay, shouldn't the safety interlock have been replace by one too?

 

[THarrison]

I have bad eyesight and don't trust myself to be able to see a spark on a sunny day, so I always hook up the clips before putting the ignitor into my motor. The launch control box could be designed and made by Lockheed Martin and I still wouldn't trust it.

-Todd Harrison

 

[DaveCombs]

One thing I think would be good is at the HPR pads alot fo clubs have pad boxes. After the realy trips (its launched) it flips a switch. The relay cannot get power or trip till that switch is flipped again. So you need to do that on your way away from the pad. EVEN incase something happened with that switch to were the relay was on when it was switched, most pad boxeas are 10-15 feet. Away even for an O or P motor safer then right at it.

Ben

If I remember correctly, this was the system used at the HPR pads at NSL this year. One of the ROCI guys would have to chime in to confirm that, as they obviously know their system much better than I do.

 

[Ryan S.]

The thread has been cleaned up from some posts insulting other members directly and indirectly. Anyone who's had a post pulled, please feel free to repost any content that's pertinent to the topic at hand.

I would love to respond again to this thread however it is obvious that my posts will just be deleted.

There are many things I would love to add, however, it takes too much effort to type a post just to have it pulled down.

Thanks for everyone who responded, there is some interesting stuff in here.

 

[KermieD]

Post insults to another member and yes, they will.

 

[Ryan S.]

I didnt insult another member, not that I can prove it since the posts are convienantly gone.

 

[KermieD]

PM sent.

 

[PGerringer]

There are many things I would love to add, however, it takes too much effort to type a post just to have it pulled down.

It also takes too much effort to pull out the statements that violate our guidelines. Please consider them when posting. It will be good for you, the mods as well as the community at large.

 

[cjl]

I generally do the stuff at the pad in the following order:

1) Put rocket on pad
2) Arm electronics
3) Put igniter in motor
4) Touch clips together to check for live wires
5) Hook up clips

 

[xenon]

A lot of people mentioned that they touch the clips together and look for a spark, which is a good practice, however, at some point, someone recommended to me that you touch them to your tounge and see if you feel anything. That way, even if it is sunny, you'll know.
This doesn't work the best for systems that run 12v through the continuity check though, as you can feel it even though it is safe. In that case I hook up the igniter before installing.

 

[ben]

A lot of people mentioned that they touch the clips together and look for a spark, which is a good practice, however, at some point, someone recommended to me that you touch them to your tounge and see if you feel anything. That way, even if it is sunny, you'll know.
This doesn't work the best for systems that run 12v through the continuity check though, as you can feel it even though it is safe. In that case I hook up the igniter before installing.

thats the most interesting thing I have heard. The launch clips at my club are 3 years old and have rust, APCP, BP, ADIS, HPV, etc. anything that has been on teh ground has touched that clip. No sure I want to put them on my tounge!

Ben

 

[DaveHein]

I still say it's crazy to hook up the igniter and then insert it in the motor. You will be seriously injured if the igniter goes off while you are inserting it in the motor.

There are many ways to check if the circuit is live:
- Touch the clips together and look for a spark
- Carry an extra igniter just for testing
- Attach a beeper to the clips
- Test with your tongue? (I wouldn't do that)
- Buy a car horn from a junk yard and test with that (Then everyone will know it's live)

Or you could connect the igniter to see if it blows. If it doesn't go off then disconnect it, insert the igniter and reconnect it. If it does go off when you test it you might want to have a discussion with your LCO or RSO.

 

[the freshman]

thats the most interesting thing I have heard. The launch clips at my club are 3 years old and have rust, APCP, BP, ADIS, HPV, etc. anything that has been on teh ground has touched that clip. No sure I want to put them on my tounge!

Ben

Hmm, perhaps Andrew has accumulated a taste for propellant residue and HCl from too many launches over the years!

Just kidding...

But I think the best way might be to just walk to the pads with a multimeter in your pocket.

 

[DaveCombs]

- Attach a beeper to the clips

I like that one, although it could be carrying enough current for a continuity check (instead of the full-on ignition amps) so you'd kinda get a false positive.

We'll all be out there with voltmeters before long...

 

[m85476585]

Why are we still using relays? It would be relatively easy to design a board for FETS that can switch hundreds of amps. Chips like <a href="https://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=IRF2907ZS-7PPBF-ND">IRF2907ZS-7PPBF-ND</a> can switch 160A@10V (75V max) for as little as $5 each. (There are a few FETs with screw terminals, but they start at $30 each). Heat really shouldn't be an issue with these chips because of their incredibly low on resistance (.0038 ohms for the part I mentioned above compared to about .1 ohms for a random 10A FET I looked up). With 100A@12V it would only dissipate 38W, and the amount of copper a PCB would need to handle the current would be enough of a heatsink.