Cluster air starting. A few answers from the experts needed.

stevethecontractor said:

Prepping my 12ft modified Pterodactyl for a cluster launch. Weighs 20lbs

I have the ability to hold 3 motors. one 54mm and two 38mm.

I want to launch on a large 54mm K and then air start a pair of I motors.

I have flown many 2 stage rockets and I have always set my air start around the burn out time of the booster engine plus 1/2 second.

In this case I am wondering if I should set the air start about 3+ seconds after main engine cutoff as the rocket will still be climbing. Or should I time it for right when the main engine burns out?

Also, since I am air starting two engines, would you suggest I use Cesaroni reloads since I can use electric matches to ignite instead of relying on a dipped aerotech ignitor or it does not really matter?

Lastly,
Moon burner or warps for my airstart motors? or just stay with a standard?

Thanks
Steve

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When setting a certain delay, look at the big picture.
Depending on the motor/propellant type, remind yourself how long the air stat takes it to come up to pressure and hitting the thrust.
If your main motor is a fast burner, you have a long coast phase to light the air starts.
My Patriot on a M-1650 will give me an 11 second coast phase, plenty of time to get er done.

The CTI motors light quite dependably in my experience. The pyro pellet at the top really helps with that.

I like the term "targeting" as the negatory invective. Guidance is too broad a term. Guiding the rocket to go straight up where the recovery system deploys and brings it back to the ground in no predetermined fashion is perfectly fine.
If that's ones idea of guidance of a hobby rocket it's o.k. George, "steering" occurs with active stability or stability augmentation if the boost phase is perturbated by say a gust. The rocket is steered back to proceeding straight upwards.
So boys, it's a matter of semantics. One can't actively guide a rocket to a point for a nefarious landing but they certainly actively guide it so "it's stable" on ascent! Kurt

cerving said:

NFPA 1122 states:

4.7 Model Rocket Flight Paths.

A model rocket shall not be launched on a flight path aimed at a target.

That sure sounds like a prohibition of "guidance" to me. Along with the NAR/TRA rules regarding launch angle, it's pretty clear that the intent is to make the rocket go as vertically as practical, thus Active Stabilization vs. Guidance.

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AIMED at a TARGET, EXACTLY.

THAT RULE has existed in the hobby since almost day one. What it MEANS is, you cannot launch your model in a manner that could hit a target that it is aimed at. So say someone wants to try to hit a target on the ground 1000 feet away, they use a rocket with a plugged motor, capable of ballistically arcing to hit near that target, if given the correct elevation angle (We'll leave wind effect out of this for now). So, they try it, using angle "X", and it overshoots by 200 feet. So, they try again at angle "X" minus 10 degrees and it undershoos by 200 feet. So, they try angle "X" minus 5 degrees and it gets really close to the target.

All three of those flights would be illegal, they were TRYING to hit a target (and yes, also would violate the rule about using a recovery device).

And not one of those would involve any electronic Guidance, or semanticaly silly "Active Stability System".

But yet, indeed, let's use that same rocket but give it an "Active Stability System" that simply keeps it aerodynamically stable, so it won't wobble or be affected much by wind. But since it's not guiding the rockets path, only "stabilizing" it, the rocket still flies ballistically AT THE TARGET, but thanks to the "Active Stability System" it does not have near as much random dispersion as a non-stabilized model does due to rod whip and other random factors that occur with PASSIVE stability (aerodynamically stable), so it would be more likely to be able to hit closer to a target!

So, you cited the Safety Code then invented YOUR PERSONAL INTERPRETATION. You can have whatever opinion you want on what a bunch of words mean. Just as a person can have an opinion that 2+2 = 3

But you cite them as FACT, when your FACTS are wrong.

As I already explained, this hobby has had GUIDANCE for decades, and the NAR and TRA ALLOWS THIS. Such models have flown at many NAR and TRA launches and bene featured in their magazines.

So it is ludicrous for you to claim that the Safety Code does not allow Guidance.

The Safety Code does not allow TARGETING. It says NOTHING about not allowing Guidance.

And, YET AGAIN I will say that TARGETING can be done with BALLISTIC ROCKETS, as has been done for HUNDREDS OF YEARS before "guidance" existed. The "Rocket's Red Glare" during the War of 1812, you think those were celebratory fireworks rockets the British were shooting at various TARGETS in the United States, and NOT dangerous/deadly munitions at those TARGETS because they had no "guidance" system?

THAT is what the Safety Code rule is written for, to ban trying to hit a TARGET. No matter if it is a classic 3FNC passively stabilized rocket, rocket with guidance system, or a semantic A.S.S. rocket.

It's TARGETING or not. Not whatever methods the rocket otherwise use for SAFE flying that does NOT involve trying to hit a target.

- George Gassaway

If I design and fly a rocket to adhere to a flight vector but there is no physical target along that vector is that legal?

jderimig said:

If I design and fly a rocket to adhere to a flight vector but there is no physical target along that vector is that legal?

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As long as that vector is "upwards", not necessarily vertical (as opposed to intersecting the ground), and there is not any (nor should there be any incoming) "target" near its flight path, that's legal.

Of course launching-wise, the launch angle has to be no more than 30 degrees from vertical (for models, 20 degrees for HPR), except for Rocket Boosted Gliders that are controllable in pitch during boost, which are allowed 45 degrees. Of course with guidance onboard, the launch angle does not necessarily define the flight path angle after liftoff, once the guidance system steers the model in the intended manner.

An example of that is this flight, an R&D Demo flight at NARAM in 2013 by Alyssa Stenberg, for her winning R&D guidance project. The guidance system (Eagle Tree Guardian R/C autopilot, which her project tested to prove it could work for rockets) was set to make the model guide itself to fly vertically, but was launched at an angle to prove that it overcame weathercocking, overcame gravity turn, and steered itself to vertical (once it got fast enough for the control fins up front to be effective enough to pull it upwards from that initial angle). Power by D12-0 to E9. Note the NAR Flag at 40 seconds into the video, lest anyone want to claim again that the Safety Code does not allow guidance.


[video=youtube;kTND_wot9zI]https://www.youtube.com/watch?v=kTND_wot9zI[/video]

Here is the gray area I think. The z-vector (vertical target vector) is arbitrarily no different then any other directional vector into airspace, its simply a choice. If I have an active stabilization system that keeps the rocket vertical (along vector 1z), code and mechanism is already in place to put it on any vector ( .2x + .2y + 0.96z)

As an example lets say I want to put the rocket specifically at an upwind point in the sky at apogee for recovery purposes. That point is a "target" although there is no physical object there. It seems to you are suggesting the legality is determined by the intent not necessarily the capability.

jderimig said:

Here is the gray area I think. The z-vector (vertical target vector) is arbitrarily no different then any other directional vector into airspace, its simply a choice. If I have an active stabilization system that keeps the rocket vertical (along vector 1z), code and mechanism is already in place to put it on any vector ( .2x + .2y + 0.96z)

As an example lets say I want to put the rocket specifically at an upwind point in the sky at apogee for recovery purposes. That point is a "target" although there is no physical object there. It seems to you are suggesting the legality is determined by the intent not necessarily the capability.

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And generally that is a good idea, to have a model fly to an area upwind to minimize drift downwind. However some sites might not want to allow that if the upwind area would be over buildings or people.

In any case, the Safety Code rule is about the intent... "Target".

Not about capability, because ANY ballistic model rocket is "capable" of being launched to try to hit a target.

Ironically for a lot of the hobby rockets that are using guidance systems, most of those systems are not 3D Space or GPS coordinate aware, so their effect on the non-ballistic flight paths would be too random to use to try to hit a target (Guidance that tries to fly vertically, if launched first at some angle, the horizontal distance for pull-up to vertical can vary a lot and would tend to be really crappy to use for "targeting" any object in the air or on the ground.

But again as far as the Safety Code goes, it's about the intent, not the capability.

Just like driving a car....... a car is CAPABLE of being used as a deadly weapon, but it is not illegal to drive a car (if you have a license), until the point where you intend to use it as a weapon. Heck, far as that goes, all sorts of things are "capable" of doing serious harm, like a baseball bat or hammer.

Now if I were a terrorist wanting to use some hobby model to do something bad...... with today's technologies it would be more effective to do a lot of bad stuff with R/C Planes/Copters than a rocket (Not going to say how or in what ways). The one thing that a hobby rocket could theoretically be better at..... trying to hit an aircraft, fortunately requires more advanced tech than available for hobby use. That's not to say some sufficiently advanced college students or lone wolf engineer would not be able to come up with a sensor technology that might be effective in some situations (I'm not going to speculate on the possible tech because other than recognizing the possibility of such being created, no good can come from effectively planting ideas or outline ways to do so. That would be irresponsible). But that's way past the point of the Safety Code and rules for hobbyists flying legally.

So how did helping someone with airstarts evolve into Targeting and steering? Start another thread.

Dave A said:

So how did helping someone with airstarts evolve into Targeting and steering? Start another thread.

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Was wondering the same thing.
Appears to me that if clustering/simultaneous ignition works properly, guidance is a non issue.

Where? Did you not read the thread?

Message 12 implies non-existent rules to inhibit air-starts or staging if the angle exceeds a certain degree error. Also implying technology that would be required for such a rule, but only a very handful of people have the kind of onboard technology that can sense an angular error from vertical and most importantly have the programming capability to therefore do an inhibit. Only certain onboard guidance systems, or unique onboard flight computers with suitable sensing technology, could have that capability, nearly all of them homemade with the builder choosing to add an inhibit option. Most other guidance systems do not have any extra options like that .

So not only is there not a rule requirement to inhibit, there is not a general capability for 99%+ of the fliers to do that since there is no off-the-shelf commercial unit that can do that, AFAIK.

Although it is a really neat idea for those who have the technical capability, to choose to add that feature.

Then message #18.

And the ultimate message #24, which stated as though a fact and as though a rule that “"Guidance" is most definitely NOT allowed.”

Pretty much any time anyone starts posting non-existent rules, there’s going to be a response to set the FACTS straight.

Yes, I realize it caused a major thread drift.

You are suggesting that when these errors and mistakes are posted in a thread, that the record NOT be set straight in that same thread? To allow the wrong info to be left alone as though it’s true? Starting a “new thread” would do nothing to solve the errors in the original thread, with that bad info remaining. The moderators would have to agree to move all of the thread drift posts into a new thread, which I could see on a forum like NASAspaceflight forum (where major thread drifts are sometimes moved into a new thread), but not here.

BTW , you do realize that your post caused this thread to drift further?

See also: "Let sleeping dogs lie". You could have posted something about air-starts, as several had done after the guidance related posts had ended.