Bear in mind as you read and consider what I have to say is that every scale judge is an individual and it is up to him to interpret the rules when it gets right down to the nitty gritty. What I am saying is not set in stone and certainly there are some out there who will disagree with me. However, use what you read here as a basis for formulating questions that you might ask of the judges at the next scale meet you attend.
I think there are more discussions and arguments about the very first paragraph of the NAR Sport Scale rules than just about any other in Scale rocketry.
Sport Scale Competition comprises three events open to any model rocket that closely resembles an existing or historical guided missile, rocket vehicle, or space vehicle. The purpose of this competition is to produce a flying replica of a real rocket vehicle that exhibits maximum craftsmanship in construction, finish, and flight performance. Sport Scale Competition differs from Scale Competition (Rule 50) in that the dimensions of the model are not directly measured.
In a nutshell, this rule basically tries to say what a Sport Scale model is…and due to its intentional brevity leaves a lot of room for interpretation. But let’s look at the letter of the rule.
The second sentence of the first paragraph is the most defining element of Sport Scale competition (perhaps a minor Pink Book revision should reverse the order of first and second sentences of this paragraph) "...To produce a flying replica of a real rocket vehicle..." I think the spirit of the rule is clear in that the intention is that you produce a model of a vehicle which uses as its source of power a form of rocket power. It doesn't exclude other forms of power from being included...but it does more or less require that some element of propulsion be powered by a rocket...very simply a reaction device that carries all of its own fuel and moves by ejecting something (likely, the by-products of burned fuel) at high velocity in order to derive motive force. You can bend and nit-pick over definitions all you want, but if some element of propulsion is not that of the rocket, then you just don't fit the requirements of the event.
The first sentence defines the model as a MODEL ROCKET. It states that it should closely resemble an existing or historical guided missile, rocket vehicle, or space vehicle. This is the part that most argument, open interpretation, and disagreement in the event centers on. ‘Nuf said on that one.
Some will want to argue what the word “resembles” really means in the context of the rule. Well, that’s kind of like trying to define what the meaning of the word “is” is. But, it is what the heart of the event is about. The more closely and accurately you come to building a model that is identical to (but it can be smaller [usually], the same size [infrequently], or larger [almost never] than) the real thing. I won’t dwell further on this.
However, the next few words: ” existing or historical guided missile, rocket vehicle, or space vehicle” are the real crux of most arguments. Just what is a guided missile, a rocket vehicle, or a space vehicle? The rule, due to the use of the word “or” in the sentences does not mean that your prototype choice has to fit all of these three categories. It simply means that it should fit at least one of them. Many modelers feel that all three automatically imply that the prototype must be some kind of rocket. If you go by the letter of the rule, only one of the three says anything about “rocket.”
Guided Missiles have had solid rockets, liquid rockets, turbojets, and
ramjets for power. There have been missiles which use combinations of rockets
and jets. Some will argue the rockets are okay but nix the jets. This is not
what the rules say. Further…guided missiles have also utilized internal
combustion piston engines and propellers, turbojet engines, and even no engines
(in the case of gliding missiles). The first recognized guided missile was a
rail-launched, piston-powered biplane in World War I. And there have been
missiles which are piston powered but are launched by rockets. Just don't
try to convince a Scale judge that your replica of that very first biplane that
it qualifies (You figure it out...it didn't have a rocket motor).
Just don't try to convince a Scale judge that your replica of that very first biplane that it qualifies (You figure it out...it didn't have a rocket motor).
Perhaps the one controversial element here is the word "guided." I don't think that the intent is to exclude unguided misiles and rockets but the term "guided missile" is so common that we can just call this a case of being too "generic." It's just like calling any cola soft drink a "coke" (lower case usage is intentional!). Perhaps the rule should more accurately read "missile or guided missile."
Rocket Vehicle is the most vague of the bunch in spite of at first seeming the most obvious. Is the little known liquid rocket powered P-51 a “rocket vehicle”? I’d say so (more because it could and did fly solely under the power of its liquid rocket motor). Is a rocket boosted glide bomb a rocket vehicle? I’d say so. What about the NF-104? Most certainly so. And…here’s a stretch…what about a RATO assisted C-130 Hercules cargo plane? Hmmm…. BIG, BIG Stretch coming here…what about the NASA SR-71 which was to have also fired (and got supplemental thrust as a result) a linear aerospike engine strapped to its back?* There are many more examples.
Space Vehicle really leaves the door open. There are space vehicles which have no propulsion at all (but remember that the second sentence clearly states "real rocket vehicle") so don't try to get by with a Skylab (it had no rockets or maneuvering thrusters but was "maneuvered" by using a series of massive spinning gyro stabilizers.. What about vehicles like the Lunar Module?** I’d say it fits (It also fits the “rocket vehicle” part, but then again, it can be argued that it cannot fly and perform its mission without being launched on top of and might technically be considered a “stage” of the Saturn V…which is the point of yet another Sport Scale rule). What about the Apollo Spacecraft? It does have rocket power and thrusters. It is an autonomous vehicle. But to the mind's-eye of some it suffers the same “is it a ‘stage’ of the Saturn?” problem. Now, the BIG stretch...what about the Shuttle Orbiter? Is it a space vehicle or a stage? Hmmm…
*There's really a sneaky "gotcha" on the SR-71 issue. Though the SR-71 was fitted with and flew with a linear aerospike engine on its back, it never "fired" the engine due to technical issues.
**Precedence is in favor of the Lunar Module as it has been allowed to enter and has placed well in several competitions, including NARAM. By extension of this precedence, space vehicles (particularly if they have a primary rocket propulsion system) should also qualify...Surveyor, Apollo SM/CM, Viking, etc.
Most modelers, particularly those that want to have some assurance of not being disqualified or having their model “discounted” or “minimized” in the mind’s eye of the judge, will play it safe and select prototypes that are obviously rockets in the classic sense in that they tend to be relatively long and slender, usually with fins, and powered by either liquid or solid rockets. You are also safe in extending this to pure rocket aircraft such as the X-1, X-2, X-15 and the like. How far you push it is up to you but be prepared to suffer the “judgment” of the person who is judging your event.
My suggestion is that if you are new or relatively new to Sport Scale, stick with something that is very obviously a “rocket.” This is pretty much a common sense thing. They are generally easier to model successfully and to rake in a high number of points. If you want to push the limits and get into “grey areas” of the definitions of what is allowed in the Sport Scale rules then you will probably have other things to consider in addition to trying to convince the judge that your borderline choice fits the rules because chances are that it will also be of a relatively non-rocket shape that is not easily adapted for flight, have asymmetries and compound curves that are hard to model, and push the limits for reliable and safe flight. The question you have to ask yourself is “Is it worth it?” By selecting borderline prototypes you are probably lowering the number of points that you can get due to falling short in Similarity of Outline (the most important rule), Finish, Color and Markings (which are usually complex and hard to do well in borderline prototype choices), Craftsmanship (more complex shapes and number of components works against you here), Mission (you’d probably just skip and not go for those points), and General Flight (yeah…just TRY to get that asymmetric, forward CG creation to fly straight…).
And remember, when it comes to judging, Scale judges have almost as much “say” over your model during static judging as an RSO has on the flying range. He won’t take favorably to having his valuable judging time (and he has probably spent HOURS looking at models with more to come) arguing with you whether or not your model fits the Pink Book definition.