From: Trip Barber, NAR# 4322 Email: email@example.com
Type of Proposal: Regular
Brief Summary of the Proposed Change: Prohibit the use of piston or other pressurization-type launching devices that use exhaust gases from the rocket motor to increase its launch velocity and altitude. This restriction has been implemented in international (FAI) competition for altitude-type events starting in 2019.
State Logic and Intent of Change: Years of R&D reports and development have led to the use of increasingly sophisticated piston-type launchers in competition by the most experienced and advanced competitors. These devices substantially improve the flight performance of rockets launched from them. This “arms race” has reached near-ridiculous proportions, with long elaborate devices being erected on the field. This is profoundly discouraging to other competitors, particularly new ones, who do not have the experience or resources to create and use such devices and see that if they do not use them they have little chance of success. If we want to spread the popularity and accessibility of model rocket competition, we need to level the playing field by making events a competition between flight vehicles, not launch systems. I expect experienced competitors who are engaged in this piston-launcher “arms race” will oppose this proposal because they think that with the next step up in their launcher’s complexity they can win. Rocket competition should be about flight vehicle (“rocket”) performance, not launcher performance.
Effect, if any, on current competition and NAR records: Many performance records have been set with use of piston launchers, but they are not specifically identified as such. It will be difficult to exceed these records in future without use of piston launchers, but there is no reason to retire any existing records if this proposal is enacted.
Exact wording for the rule revision as it should appear (include section#):
5.6 Launching Device A launching device must not impart to the entry any velocity or change of momentum by any means. The entry must free- fly from the device.
13 Comments on RCP# 2018-08
I am a reformed piston user.Â They DO impart a (potentially illegal) momentum to the rocket in addition to the 'rated thrust' of the motor.Â That's why they improve performance.
BUT, they distract from the ROCKET side of the competition.Â So I agree with this rule, for existing classes of competition.Â
BUT MORE, if we want, there could be a 'PISTON REQUIRED' set of classes too.Â That would allow those of us that are (or have been) addicted to this technology to continue to show how its done.
PERHAPS, even have scoring be the difference between two flights, one with, one without... just thinking y'all.
I oppose the banning of piston launchers.Â It is an easily implemented idea that has been around for a long, long, long time.Â Also, it is a piece of technology easily used by even an A divisioner.Â Think twice before implementing a total ban.Â Â I do however somewhat agree with placing a limit on the total length of pistons though I not sure about even that.Â How many contestants use really long pistons?Â Lets do a survey at NARAM and see what impact it actually having on competition.Â Mostly its just teams using them I think.
I strongly support this proposal and thank Trip for succinctly capturing the rationale. I am a piston user, myself.Â I understand the significant benefit using pistons provides and the barrier this presents to newcomers. I also understand the angst that many of our seasoned competitors may feel towards sacrificing this performance improving technology.Â
I also believe that the distinction that the launcher not impart any velocity or momentum to the model is a critical difference that separates pistons from all the other competition launcher technologies eg towers, pop lugs. I think this a clear and reasonable delineation.Â
Although not a panacea, I believe that this one move could be the most important step in increasing participation in competition model rocketry.Â
I would support a size restriction (<= 2 meters), an event restriction, or some other carefully thought out use-restriction, but not a total ban.Â
I may think the "arms race" has gotten a little ridiculous, but I also hold the opinion that doing something radical like banning all piston launchers is even more ridiculous.Â We should carefully consider some size restrictions if your main objection is truly the "arms race."
This is what this rule proposal is telling me:Â "We don't like 3-meter pistons, therefore we need to ban all of them..."Â Must we ban even the smaller pistons that so far haven't been a problem?Â Doesn't that seem a little bit like overkill?Â It does to me.Â Storming the castle and burning it down just because you don't like something is not a very sensible approach - and neither is enacting sweeping rule changes because you want to fix one little thing.Â It is rash and imprudent.
And doing things because the FAI did things - irrelevant.
As an occasional competitor who has been to exactly two NARAMs I have only actually tried to use pistons at NARAM-60. The ones I flew were based on an R&D report about smaller motors and they werenât that hard to make or use. That said, I observed the arms race to which Trip refers in action and had to shake my head. As an individual and relatively infrequent competitor, I would never go to such lengths.
The likely need to use pistons to be truly competitive for some of the events scheduled for NARAM-61 is giving me pause (as at least three sizes of pistons will be needed, fabricated, tested, tuned, packed) as I ponder what I will need to build and practice with for that event. Elimination of this complication so I could focus on the actual rockets would be a relief (even though this change, if enacted, will not affect NARAM-61).
I share with Dave Cook the concerns about an outright ban with respect to 1/4A HD or BG/RG since there is only one motor 1/4A currently available and it has a nominal 3s delay, but outside of that, I am on board with this.Â Iâd be more in favor of an exception to the ban for this sort of model than Garthâs suggestion of making it an A division/B division/C division thing. But - that brings to mind this: since the arms race seems to me to be almost exclusively the purview of D division (again, based on what I saw at NARAM-60) - maybe allow pistons only in D division?
Garthâs second suggestion about record trials is intriguing.....
I only have a touch of reluctance voting for this because simple pistons and what they do are kind of cool (at least now that Iâve figured out how to make and use them).
Dave Cook here. I generally support this proposal, despite having been a piston user for about 40 years. The central problem here is that the physics indicates that there are performance gains to be had from really extreme designs where you end up doing a lot more engineering on a 2-3 meter launcher than the model. And thereâs definitely an arms race underway.
That said, I donât buy the complexity objection to pistons in general as you can make a very effective 1 meter piston in less than an hour with exactly one fabricated part.
There are situations in non altitude events where using a more modest piston is a functional benefit, such as very low impulse BG and HD where you need some breathing room to get glide/rotor transition. The piston also reduces the risk of hanging up on the rod when there is very little thrust.Â
My suggestion would be to disallow pistons in altitude events, and limit the effective length in other events by keeping the 2-meter-off-the-ground rule.Â
If pistons are removed from altitude events, then I think all altitude records should definitely be retired, as they will become meaningless and mostly unattainable in a no-piston regime.Â
To answer an issue raised in other comments, I see no indications that rules changes of this kind have any significant effect on participation, so I would not weight that very much here.Â
While the arguments for this change is to level the playing field, all the same arguments could also be made against the use of towers. Everyone has towers, small to large complex one. They add complex to the event, dragging the out. Setting the up, moving them around, but you kind of need them to be competitive in a lot of events. Even pop lugs or flyway guilds. If you wanted a level playing field then maybe the rule change should be every rocket should have rail guilds of some minimum size for the class of motor. If the rule is to make the playing field level, it misses the mark by only disallowing a technology that someone doesn't like, instead of really leveling the playing field.
A couple observations here:
- Â NAR has no requirement to sync up with anything the FAI does.Â These are two different organizations with significantly different rule sets.Â I haven't seen the FAI scramble to do anything the USMRSC has in it, so why the reverse??Â Bad logic here...
- Pistons are cheap and relatively easy to use.Â But more than that, they are somewhat necessary for certain events, such as BG/RG/HD in the 1/4A and A motor classes.Â In FAI, delays are available in 1, 2, 3, 4, 5, 6, 7, 8...etc.Â We don't have that in NAR comp.Â So pistons help to alleviate the problem of too long delays in say A HD or 1/4A BG, where there are no 'short' delays available.Â Pistons also help make those 'heavier' models built for a higher motor class now usable in lower motor class events.Â It further helps those newer competitors that may not have an arsenal of models like the veterans do to use what they have to get qualified.....
This is an interesting proposal on many levels. History shows challenging the status quo is never easy or popular. The key element is the need to make "competition between launch vehicles and not launch systems."Â Do we wish to grow competition rocketry or see it go extinct?
As a CD I have seen many beginning competitors struggle with mastering the art of the piston. It takes a lot of practice and flights to get a repeatable piston launch even for seasoned NAR competitors. The high failure rate for newbies is daunting and discouraging especially for A and B divisioneers to get it. Yes people have walked away from contest rocketry because of not getting it or worse the hobby.
I find it interesting that TARC competition does not need to piston at all concentrating instead on repeatable altitude and duration for the teams. In short concentrating on launch vehicles.
I'm all for this proposal. Yes it is a radical change especially in the low impulse classes such as 1/4 A events. But so was putting our Sun at the center of the solar system. We all are better for it.