Payload accelerate after rocket separation?

[MotoMike]

The USN used to shoot ASROC from box launchers. It was a torpedo with a rocket motor on the back. it was ballistic. The rocket fired and then separated mid flight. the torpedo continued on, a chute was deployed to slow and I think stabilize the water entry after which the torpedo went on about it's business.

I was told by an engineer that was aboard one time that at the point of separation when the motor stopped, and the air-frame separated and the freed torpedo continued on, that the torpedo experienced a bit of further acceleration. It seemed unlikely to me, but I was assured that it was so.

can anyone help me out?

thanks, Mike

 

[berkeman]

The USN used to shoot ASROC from box launchers. It was a torpedo with a rocket motor on the back. it was ballistic. The rocket fired and then separated mid flight. the torpedo continued on, a chute was deployed to slow and I think stabilize the water entry after which the torpedo went on about it's business.

I was told by an engineer that was aboard one time that at the point of separation when the motor stopped, and the air-frame separated and the freed torpedo continued on, that the torpedo experienced a bit of further acceleration. It seemed unlikely to me, but I was assured that it was so.

can anyone help me out?

thanks, Mike

By F=ma, when you stop the force you stop the acceleration. If the torpedo were on a downward trajectory, it might get some additional acceleration due to gravity if it were not already at its terminal velocity.

 

[MotoMike]

Thanks very much Berkeman. That makes sense to me. As I understand it he was alluding to some energy being transferred from the loss of mass. I didn't think it made sense, but he was a rocket scientist after all.

 

[Svein]

I was told by an engineer that was aboard one time that at the point of separation when the motor stopped, and the air-frame separated and the freed torpedo continued on, that the torpedo experienced a bit of further acceleration. It seemed unlikely to me, but I was assured that it was so.

If the separation was brought about by a small explosion, the force of that explosion would affect both the torpedo and the air-frame (but in opposite directions). Thus, the torpedo could very well have gotten a "push" from the separation event.

 

[MotoMike]

The torpedo and rocket motor were held together by a center section. basically an aerodynamic tube split in half lengthwise. It fit over the aft of the torpedo hiding its control surfaces and chute pack. And around the front of the rocket motor. two bands, one in front and one in the back secured it in place. The explosion that takes place that breaks the bands loose is quite powerful. I don't recall just how that worked, but thought the forces would be radial. the rocket motor immediately falls away. while the torpedo continues on. the separation occurs on the upward excursion. attached is an image that is as I recall them.