Keith and I have been pretty quiet about TeleMetrum for a while... but that doesn't mean we've been idle!

In recent weeks, I've built up several more flight units and two more ground station boards, as noted in my production log. We're both trusting rockets solely to our boards and Keith's firmware at this point. In fact, we've accumulated a significant number of succesful flights, including a cool drag-race between 4" airframes at NCR Oktoberfest where we both put brand-new, nearly identical rockets fully at risk flying only TeleMetrum boards, and a flight by Keith the same weekend on a full-K Loki K350W moon-burner in which he set a new personal altitude record! I've also flown a board with 100-g accelerometer installed successfully in a flight that peaked at 52.8 g!

We're now hard at work on a "next version" of the hardware, incorporating everything we've learned so far. There are a number of significant changes planned:

  • Fully integrated, on-board GPS receiver and patch antenna, with support for off-board amplified antennas when airframe geometry or materials demand it.

  • A change in the design of the circuit for firing e-matches to ignite ejection charges that will improve mechanical reliability, plus explicit support for using a separate pyro battery if desired.

  • Inclusion of a "companion board interface" that we envision using for a pyro channel expansion board to support staging and air starts, among other things.

  • Dramatic increase in the capacity of the on-board data logging memory.

  • Changes in connector series to eliminate our dependency on expensive crimping tools for making cables.

To make all this fit, I'm stretching the board an extra 1/4 inch to a total outline of 1 by 2.75 inches. We're also moving all the connectors, the GPS patch antenna, and the beeper to the "back side" of the PC board. This is a win on several levels... it will allow us to have silk-screen labels for the connectors, will help protect the baro sensor from sunlight and the various surface mount parts from physical damage during rocket prep, and opens up more board surface area for component placement and routing on the "top side" of the board. In practice, this means that boards will be mounted on standoffs with all the active components facing "down" and the connectors facing "up."

Before we'll be ready to build some of these, we need to get in some more flights to test the various changes we're making. In particular, the change in ejection charge circuit, and the GPS receiver chip and antenna choices we're now favoring. Unfortunately, Keith and I are now both into the time of year where launch opportunities come less frequently, even before we consider the weather.

Meanwhile, Keith's firmware and ground station software are now doing nearly everything we've envisioned wanting from this project. It seems entirely likely that he'll be ready to declare "version 1.0" soon after we obtain and verify the functionality of our next version of the hardware...

In the meantime, our friends at Woot have posted a really funny video combining material from a couple launches this summer of my 10-inch Goblin, on one of which we flew some of their screaming flying monkey dolls... Enjoy!