October 19, 2004

Consumer Aerospace

That's a term coined quite a while ago by some rocketry guys to describe what I call hobby rocketry. It takes on a new dimension with the recent successes of SpaceShipOne and the upcoming DaVinci Project, among others.

What follows is a brief explanation of the various types of organized hobby rocketry. Even the federal government weenies at the BATFE muddles the issue by confusing the terminology.

Hobby rocketry falls under three categories: model rocketry, high power rocketry (HPR), and experimental (EX). Model rocketry and HPR can also be described as "airframe engineering", because both include the use of commercially available motors. Model rocketry is up to and includes "G" motors, and HPR is "H" and above.

These motors are manufactured by companies like Estes, Quest, AeroTech, Ellis Mountain, Animal Works, Kosdon, RATT Works, Propulsion Polymers, SkyRipper, Cessaroni (and I'm sure I've forgotten a few). The motors are then tested by one of the national hobby rocketry organizations. The primary ones that in North America are the National Association of Rocketry (NAR), Tripoli Rocketry Association (TRA or just Tripoli), and the Canadian Association of Rocketry (CAR). There are others, but these three groups are the ones that do motor testing and have reciprocal agreements to honor each other's motor certifications.

The motor certifications are critical because it's what allows us to get affordable insurance.

As long as we launch under the guidelines of the organizations using approved motors, we're covered by the group insurance. That coverage also makes it possible to obtain permission from municipal facilities and private landowners to hold rocket launches.

Experimental rocketry is supported by Tripoli (and maybe the CAR, I'm not sure). EX is for those guys who manufacture their own motors. It's not cheap to manufacture homegrown propellant, the basic starter's library and safety equipment alone runs a pretty penny. The old term for those who ignore safety and common sense is "basement bomber" and you still hear about them once in a while when their house becomes a smoking hole in the middle of their neighborhood. Those clowns are *not* doing EX, because you inevitably hear about "large amounts of black powder" and other assorted explosive goodies. It drives us crazy because they get lumped under the "model rocket" umbrella by ignorant press and government officials who don't know the correct terminology, nor do they care who they slander with their inaccuracy.

If the explosion is small, basement bombers might be known afterwards as "lefty" or "two fingers".

EX launches are held around the country during the year, and most of the time what happens is a two or three-day launch is planned, with one day being strictly experimental, and the other day(s) being strictly commercial motors. EX motors don't neccessarily mean big motors either, they can be as small as common Estes-style "C" motors you find at hobby shops and WalMart.

Here's a nice video taken at the recent Whitakers Experimental Launch Days (WELD) in North Carolina. The rocket weighs in at 35lbs. Listen to the soundtrack on the video, and you'll hear some of the safety and technical discussion going on among the launch crew and folks watching.

So now you know more about the subject than the average BATFE agent (and newspaper reporter or Senator for that matter). Personally, I fly model rockets and HPR, I don't do EX. Maybe someday, but I'm in no hurry.

Posted by Ted at October 19, 2004 10:44 AM
Category: Rocketry

This reminded me of something I've been curious about. I know the motors in the Estes rockets I built as a kid are solid-fuel motors. What's a hybrid motor?

Posted by: Victor at October 19, 2004 02:16 PM

Most hobby high power motors are solid too, they just use Ammonium Perchlorate instead of black powder as the basis for the fuel grain (so does the Space Shuttle's side pod engines). These solid motors include an oxydizer in the fuel grain mixture.

A hybrid motor uses a solid fuel grain without any oxydizer added (for instance polypropolene plastic or good ol' PVC). In these motors the oxydizer must be added, and that's where the liquid nitrous oxide comes in. It's injected into the motor as the fuel grain burns to boost thrust to useful levels. Solid fuel + liquid oxydizer = hybrid.

Liquid propellant motors use a liquid fuel and a liquid oxydizer. These tend to be very finicky, but are easily the most powerful by today's technology. Using liquid propellant is outside of "hobby rocketry" and is considered "amatuer rocketry", but is just as accurately called "semi-pro" rocketry. It's for the folks who really know what they're doing. A good example are the UK club MARS: http://www.mars.org.uk/ "Britain's Amateur Space Programme".

Posted by: Ted at October 19, 2004 04:41 PM
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