Rockets to Mars

I've been researching the current state of model rocketry and there is a whole new world of high-performance rockets out there now. When I was a kid, the engines ranged from "fractional A" to "D", with each class doubling the previous letter's Total Impulse*. So a "C" engine has up to twice the impulse of a "B" engine, on average.

 

Now Estes makes an E engine with twice the impulse of a D. The photo shows the Estes range along with a G engine . Yes, G. But that's nothing.

 

The scale now goes to O. While the little Estes engines are fueled by black powder, the larger engines made by specialty companies are composed of the same solid rocket propellant used in the Space Shuttle: the impressive-sounding Ammonium Perchlorate Composite Propellant, or APCP. This composite propellant uses the Ammonium Perchlorate as an oxidizer and powdered aluminum and the binder serve as the fuel.

 

An O engine has 1,000 times the impulse of a D engine. This is a monster. It can lift a rocket weighing almost 300 lbs.

 

As you can imagine, this type of rocketry is fairly well regulated. You need specialized training to handle the fuel and launches, as well as the array of things that can go wrong. You need fire extinguishers, very sophisticated guidance and location systems, and as these rockets can soar as high as 15,000 feet and higher, you also need special clearance from the FAA at the time of your flights. Due to the incredible stress they are subjected to, you can't make these rockets out of cardboard and balsa wood. They are aluminum and fiberglass and they travel very fast - they could do some real damage to an aircraft.

 

But for us, we'll stick to the relatively weak and safe D and E engines. They still provide a spectacular launch and at a fraction of the cost (An E engine costs about $7, the fuel alone for an O engine is about $300).

 

* The Total Impulse of a rocket engine is the average thrust multiplied by the burn time. It's a measure of the maximum momentum that a given engine can impart to a vehicle. Basically it's the area under the curve of the thrust vs time graph of an engine, or if you are Calculus-literate, it's the integral of the thrust function from t=0 to t=tt, where tt is the total time of engine thrust. Total impulse is expressed in Newton-Seconds in the metric system.