Feeds

SPEARS fired up for explosive climax

Ballocket mission control board electrifies LOHAN

  • alert
  • submit to reddit

Bridging the IT gap between rising business demands and ageing tools

Our Low Orbit Helium Assisted Navigator (LOHAN) project reached a major milestone over the weekend with the completion of the first Special Project Electronic Altitude Release System (SPEARS) control board.

Click here for a bigger version of the LOHAN graphicNeil Barnes, who put together LOHAN's silicon heart with the able assistance of Anthony Stirk, reports that the beast is working as advertised. The primary function of SPEARS is to use GPS-determined altitude to fire the solid rocket motor of our Vulture 2 spaceplane, but it'll also log flight data, as well as reporting its position via radio for tracking purposes.

SPEARS is based on Anthony's Swift High Altitude Ballooning (HAB) system, although it has been heavily modified to meet LOHAN mission requirements.

Here's the bare board, as provided in double-quick time by Mitch Davis of Hackvana...

...and here's what that looks like now, complete with some red-hot electronics action:

The assembled SPEARS board

While you can't see the ATMega644 microprocessor and voltage regulator, which sit on the reverse side of the board, here's a breakdown of the principal visible bits:

  • A: Radiometrix NTX2 UHF transmitter
  • B: Crowbar triac
  • C: Ground safety switches and timer start switch
  • D: Timer circuitry and fuse
  • E: Programming connector
  • F: Temperature sensing diode inputs
  • G: 3-axis accelerometer
  • H: uBlox MAX-6 GPS and Sarantel antenna
  • I: Firing relay driver transistors
  • J: Igniter connection contacts
  • K: Firing relay

The brown and red wires apparently emerging from the end of the LOHAN logo's fiery tail are connected to an auxiliary serial data output, which will eventually hook up with the RockBLOCK Iridium satellite comms unit.

That's not an immediate priority, as we're concentrating on SPEARS' primary function, which is a simple enough proposition. At an altitude of [classified], as detected by the uBlox MAX-6, the board triggers the firing relay via the firing relay driver transistors. 12 volts surge from the igniter battery pack to the Vulture 2 custom motor igniter, and Bob's your uncle.

SPEARS is programmed to issue the launch command only if the current altitude is above 20,000 metres (to be clear of air traffic) and we achieve the desired launch height.

Furthermore, SPEARS will hold the launch if the fantastical flying truss bearing the spaceplane is not stable at the predetermined altitude. The accelerometer* will detect any heavy turbulence which might prejudice a successful blast-off .

It's worth noting that in "flight" mode, the uBlox is good to 50,000m (164,000ft). For those of you who haven't seen our previous notes on the matter, GPS chips aren't actually restricted to an altitude of 18,000m (59,00ft) or a velocity of 515m/s (1,152mph), but rather 18,000m and 515m/s.

Before LOHAN heads heavenwards at somewhat less than 515m/s, our crew is protected from accidental motor ignition by the ground safety switches. Neil Barnes explains:

For launching we enable things a step at a time. If at any time, we don't see the lights we expect, and in particular if we see the 'STOP' light, we abort. We start with the power disconnected from the board and the igniter cable disconnected.

  • Set all three switches off - this should give two yellow 'SAFE' lights. It disconnects power from both the relay coil and the relay contacts, and resets and stops the timer.
  • Turn S1 on: this powers the coil side of the relay and sets its red 'LIVE' light.
  • Turn S2 on: this powers the contact side of the relay, and sets its red 'LIVE' light. If there is a contact fault in the relay, this will light the 'STOP' light. That indicates that the igniter contact is live; it's a bad idea to attach the igniter at this point.
  • If we're happy with just two red lights, we can attach the igniter.
  • The final act, just before we launch, is to turn S3 on, which starts the timer - look for a flashing 'TIMER' light.

The timer set-up is intended to completely disable the ignition system after roughly two-and-a-half hours, should the Vulture 2 for any reason return to terra firma with the flying truss. This minimises risk in the unlikely event that some hapless member of the public stumbles across LOHAN before we get to the landing site.

The system is entirely independent to the SPEARS microprocessor, and is powered by the 12V igniter batteries. The timer circuitry starts running as soon as the aforementioned Switch 3 is flipped. Once it times out, it fires the triac which shorts (crowbars) the 12V supply, blowing the fuse.

The position of the flying truss will be sent regularly by the Radiometrix UHF transmitter, which offers standard licence-exempt frequencies of 434.075MHz, 434.650MHz (EU) and 458.700MHz (UK).

If all that wasn't enough, SPEARS records flight data to an SD card, so we'll have a complete record of position/speed/altitude, accelerometer readings, and temperature from three sensors, the exact positioning of which is yet to be decided.

So, SPEARS has scrubbed up pretty well. Now we just need to find out if the thing will deliver the goods under operational conditions... ®

Bootnote

Thanks very much to Babelduck for helping us out with the accelerometers. It's much appreciated chaps.


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.

LOHAN - A Special Projects Bureau production in association with...

  • 3T RPD logo
  • University of Southampton logo
  • Applied Vacuum Engineering logo
  • Escher Technologies
  • Flashpoint Fireworks logo
  • HAB Supplies logo
  • Rock 7 logo

Paper Aircraft Released Into Space

Mobile application security vulnerability report

More from The Register

next story
Bad back? Show some spine and stop popping paracetamol
Study finds common pain-killer doesn't reduce pain or shorten recovery
Malaysian Airlines flight MH17 claimed lives of HIV/AIDS cure scientists
Researchers, advocates, health workers among those on shot-down plane
World Solar Challenge contender claims new speed record
One charge sees Sunswift travel 500kms at over 100 km/h
Mwa-ha-ha-ha! Eccentric billionaire Musk gets his PRIVATE SPACEPORT
In the Lone Star State, perhaps appropriately enough
SMELL YOU LATER, LOSERS – Dumbo tells rats, dogs... humans
Junk in the trunk? That's what people have
All those new '5G standards'? Here's the science they rely on
Radio professor tells us how wireless will get faster in the real world
The Sun took a day off last week and made NO sunspots
Someone needs to get that lazy star cooking again before things get cold around here
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.