The RockBLOCK, pictured above, can "send and receive short messages from anywhere on Earth with a view of the sky", and it's this latter capability which has now become a vital component of our Low Orbit Helium Assisted Navigator (LOHAN) spaceplane mission.
For our Spanish launch, the Agencia Estatal de Seguridad Aérea (State Air Security Agency) and Aeropuertos Españoles y Navegación Aérea (Spanish Airports and Air Navigation), require an emergency balloon cut-down in the event that LOHAN wanders off course.
Fair enough, so cue the RockBLOCK-Arduino sandwich, as served up by LOHAN team member Dave Akerman:
The sandwich comprises:
- RockBLOCK satellite modem
- Arduino Mini Pro 3.3V 8MHz
- 5V regulator
- AAA battery holder
- Four Energizer Lithium AAAs
- MOSFET to fire the release
- Cable with JST connector to connect to cut-down
Dave notes: "At present the circuit assumes a resistor cut-down, for which those batteries are plenty. If the cut-down is a pyro then I'll need to replace the single JST cable with two - one for the pyro and one for the external battery supply."
Whatever we decide, we'll need a cut-down protocol that conserves both hardware battery power and cash. Talking to the RockBLOCK burns juice as well as transmission credits, so Dave has proposed: "I'm thinking of having it poll every five minutes, then if we need it to cut-down I'll send an 'Arm' message at which point it'll poll every 30 seconds for five minutes. If in that time it receives a 'Fire!' message it'll hit the cut-down. Otherwise it'll disarm and go back to polling every five minutes."
Sounds like a plan, but surely we're going to need a box with flashing lights and a big red button on it to command the abort? Yes we are, and Dave is working on something truly preposterous that will, when it's done, require an equally preposterous backronym, in the best SPB tradition.
As is the local custom, we'll leave the matter up to you, our beloved readers, so watch this space. ®
Further LOHAN resources:
- New to LOHAN? Try this mission summary for enlightenment.
- You can find full LOHAN coverage right here.
- Join the expert LOHAN debate down at Reg forums.
- All the LOHAN and Paper Aircraft Released Into Space (PARIS) vids live on YouTube.
- For our SPB photo archive, proceed directly to Flickr.
- We sometimes indulge in light consensual tweeting, as you can see here.