S1B Altitude Competition Strategies
The following are some random tips on getting the most out of the
models:
- Pay attention to the weight of the model. It really is important to
have as light a first stage as possible and have the sustainer weight
matched to the engine type. - Use a piston to launch these models to get the most out of the first
stage engine. - Use tracking powder that has a color that contrasts well with the
sky during the competition. Red/orange is good almost all the time.
Black is good on a uniform blue or white sky day, but is not good in a
gray or mottled sky. White is good only against a clear blue sky. For
tracking powder competitors use carpenters marking line chalk, tempura
paint powder, copy toner, or whatever they can find that has a good
color, disperses well, and allows the sustainer to have the correct
weight. - Use as much tracking powder as you can! Try to make everything else
in the sustainer as light as feasible to allow as much tracking powder
as possible. A great flight does no good if the trackers can't spot
it and track it. - Launch the model to achieve a sustainer flight that is absolutely
vertical to maximize the altitude of the model. Do not try to launch
anywhere toward the tracking stations, you'll only make getting a
closed track (one which falls within the allowable margin of error)
more difficult. - Use as much power in the sustainer as possible under the rules for
the contest. The current FAI World Spacemodeling event is S1B, which
allows a total engine power of 5 newton-seconds. In the World
Championships the U.S. Team typically has a special batch of engines
made that allow for a lower stage of approximately 0.6Ns (1/4A) and a
sustainer of approximately 4.4Ns. For competitions in the U.S. engines
types are limited by what is determined certified for use in that
contest (usually only standard commercially available engines.) - Be sure the engine in the sustainer is firmly secured. The pressure
of ejecting the tracking powder can easily blow the engine out the
back of the model instead. - The most straight forward method of igniting the sustainer of these
models is through a stuffer tube as shown on the plans. Use a piece
of staging igniter (by Apogee Components) or similar material placed
in the nozzle of the sustainer motor and locate it within the stuffer
tube so that it have a good cross-section exposed to the hot gasses
from the first stage motor at burn through. (This can be done by
coiling the material in a plane parallel to the base of the motor.)
Provide a small (1/8 inch +/-) vent hole in the top of the stuffer
tube assembly to allow the initial 'cold' gasses from the first stage
motor to escape rather than pressurizing the tube and popping off the
sustainer before the hot gasses arrive and ignite the staging igniter. - Use an altitude prediction program to determine the optimum delay
for the sustainer motor. If the available delays are not at this
value, use the next lower delay time. It is better to have the model
eject slightly before apogee rather than after. Especially when you
consider that it is difficult to achieve a perfectly vertical flight
and any altitude loss by going over apogee will only be accentuated by
a longer than optimum delay.