5.5" ATACMS Flight 1

One problem I knew that I was going to have with this flight was a shorter than needed motor delay. Aerotech was not shipping much product and all 54mm motors were shipped with a long delay. I had planned to swap out the delay element with an XL delay but apparently many others had the same idea as I couldn't locate the required part. So I flew anyway knowing that the 14 second (nominal) motor delay was going to hit early. As you can see in this plot of the data, ejection was even earlier than expected.

In this graph the acceleration and blue altitude lines are unfiltered while the velocity and green altitude are Kalman filtered.

The time from motor burnout to deployment was on the order of eight seconds and the rocket was still moving at just under 300 ft/sec. This seemed too early for it to be caused by the motor ejection charge.

Although damage to the rocket was minimal, I decided to modify it slightly so that I could use shear pins. I filled the the volume behind the exposed coupler with some two part urethane foam before drilling two holes. I then pushed short pieces of brass tubing into the holes and locked them in place with some CA. The holes in the mating piece of body tube were strengthened by soaking with thin CA. I could then use a pair of #2-56 nylon screws to hold everything together.

Here is the data in a somewhat more raw form:

AltAcc data file. (binary, 8K)

Processed data (compressed text, 45K)

Kalman filtered data (compressed text, 34K)