The Forward Segment (the forward-most motor segement is not the top segment on the Booster) is what is star-shaped. The star pattern is to supply more surface area for the burn and is not needed on every segment. The motor burns from the inside out and bottom up. As time goes on, the star fins start to burn away (reducing surface area and hence, reducing thrust) - a built in thrust-reduction design. No need for a separate throttling mechanism - the motor does it on its own as it burns.
Guest
04-Jul-2008 03:42
i always thought it had an eleven point star shaped cross section. are they just smooth on the bottom half?