Converting motor N-S to Joules

[jderimig]

Yes.

Well, I think so

Certainly true for the exhaust, but we also need to consider the heating the vehicle itself provides to the atmosphere, but that will be influenced by things like the cd and air density independently of exhaust interactions.

TP

Well if our rocket eventually hits the ground and stops then all the KE gets turned back into heat. But if orbit is achieved then KE is preserved and less rocket motor energy gets converted to heat right? It has to be...

 

[kramer714]

Not certain if this is the right forum - maybe it actually belongs in the restricted area.

Someone at work asked me this question knowing I'm involved in rocketry....

Our company is involved with aircraft electrification.
There is a requirement to use an enclosure with appropriate coatings to withstand a large lithium-ion battery pack cooking off.

A "pod" was developed to perform testing outside the building for safety purposes.
They remotely induce an overload into some batteries with an appropriately coated plate.

They asked me how many joules there are in a rocket motor. The thought is to use rocket motor(s) to emulate the batteries.
The motor would be secured with the nozzle aimed at the plate.

I know I've seen blast deflector plates get a hole burned through them if the rocket hangs on the rod.

I work in 'electric aviation', and was involved in runaway testing. I looked at using a grain as a substitute, I gave up on the idea because,

• We got pretty good at getting cells to blow on demand
• Depending on what we were going for, the battery case rupture was part of the failure mode that we were looking at (hard to test with a grain)
  • the case rupture shrapnel was also part of the test - looking for cascading failures. The internal components came out pretty fast in certain failures. Hard to test with a grain
• The temperature spectrum would have been hard to test with an off the shelf grain
• The electrical conductivity of the 'effluent' would have been hard to simulate

Good thought, I think there could be a pyro substitute for cell failure testing, certainly for sympathetic detonation test.

Mike K

 

[Joel Shepherd]

Off-topic, but if you wanted to test the effectiveness of an enclosure meant to contain a large lithium ion battery cooking off in a potentially flying aircraft… why would you do anything other than cook off a large lithium ion battery in said enclosure?