The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


Well-Known Member
May 2, 2009
Reaction score
i wanted to see if what happens when a normal rocket motor is used as a booster, i.e. would a normal motor with a delay ignite an upper stage motor.

i designed a static testing apparatus for dual stage testing using 3/8" steel rod driven into the ground, a copper tube to secure the sustainer motor was taped to the steel rod, then the booster was taped into place.

first test involved removing the clay from the forward end of the booster motor

everything was put into position, then a heavy cardboard tube was placed over the whole thing to act as a safety device in case of cato or premature separation of the booster section.

both motors fired flawlessly, right on schedule, though since i taped the booster to the sustainer a bit strongly for the motor size, a new booster had to be fabricated...

second test was with an untouched motor in both mounts.

the booster fired and ejected without ignition of the sustainer.

upon inspection, the sustainer motor was found to be impacted with clay from the booster motor which kept the flames from reaching the propellant.

I learned something today.
thought i'd share.
I know it is against the rules, but it seems like you would get a nice flight by removing the clay from a booster with a short delay. The rocket would coast for a few seconds before the sustainer would ignite. Do you think you might try this, as an experiment?
That is interesting. You also need to test this when both motors are constrained within a tube. Still, I was wondering about the effect of the clay, and this is on the way to answering this question, in that the 'clay clog' was one of my concerns. It may be that removing the clay also alleviates my other concern, about the overly quick pressurization.

You still will need to make sure the delay doesn't allow the rocket to arc over before sustainer ignition.
i'd prefer to use a no-delay motor in EVERY case.

using the motor with the delay gives a lower peak velocity and a higher overall altitude in simulations than a no-delay motor.

i doubt it's anything that could be attempted at a sanctioned launch.

if two of the booster motors fail, it comes in at over 200 mph under power...

nothing i want to be underneath.