btrettel's Nerf blog

random thoughts about the ballistics of foam darts

Archive for the ‘Terminal ballistics’ Category

Nerf Engineering notes

Posted by btrettel on July 8, 2012

I’ve started organizing my writings and thoughts on Nerf ballistics into a set of notes (link corrected). Readers of my blog might be interested.

For the moment my notes are very rough and incomplete. I’ll update the PDF as I make changes. I’d appreciate any feedback, especially corrections and ideas.

Edit (2012-10-02): I’ve removed the notes because they need a lot of work before I’m comfortable distributing them.

Edit (2013-01-19): I’ve readded the notes as I’ve revised them somewhat. They are still a work in progress.

Posted in Design, Exterior ballistics, Interior ballistics, Math, Pneumatics, Safety, Springers, Terminal ballistics | 2 Comments »

Kinetic energy density on NerfEngrWiki

Posted by btrettel on January 10, 2011

Today I nearly finished a page on kinetic energy density for NerfEngrWiki. KED is one of the more important concepts in the safety of Nerf guns (and that much was admitted by chiefthe, a former Hasbro engineer). I detail the most important topics about kinetic energy density, however, I do not make any suggestions about what critical KED value to design for. I do not think enough data is available to make that decision. However, I intend to limit the most powerful blasters I make to a KED of 20\tfrac{\text{mJ}}{\text{mm}^2}.

Posted in NerfEngrWiki, Terminal ballistics | Leave a Comment »