Flight mode is how the Nano spends its time at the launch site: waiting on the pad, detecting the launch, recording the flight and saving the log afterwards. There is nothing to select. Switch the Nano on without a USB cable and it goes into flight mode.
The rest of this page explains in more detail how it all works and what the status LED means.
| Flight mode | USB mode | |
|---|---|---|
| How | Switched on with no USB cable | USB cable connected |
| LED | Amber, then green blips | Slow blue breathing |
| Launch detection | Live once green | Never |
| USB drive | No | Yes |
Plugging in a USB cable restarts the Nano into USB mode, and unplugging it restarts it into flight mode.
Switching on
When you switch it on, you will see in order:
| LED | What it means |
|---|---|
| Dim white, yellow, blue, green, magenta (with a brief red), then orange | Start-up checks. The brief red is normal, and the orange stage is the longest |
| Red and orange alternating | Battery under about 3.70 V. Start-up carries on, but charge it before flying if you can |
| Pink, then the saving pattern | Only if a flight was never saved, for example after a power loss. It is rebuilt and saved, then the Nano restarts |
| Bright blue | Start-up complete |
| Pink, purple and blue sweep | A setting differs from its default |
| Red, then white lead-ins with coloured blinks | The last flight number, then its apogee (see altitude blinking) |
| Dark | Measuring the air pressure to set the pad altitude |
| Amber blips | On the pad and getting ready (next section) |
A solid red that never moves on means the Nano couldn't start up properly. Switch it off and on again; a one-off glitch usually clears on a restart. If it keeps happening, please get in touch with support.
On the pad
| LED | What it means |
|---|---|
| Amber blip every 2 seconds | Getting ready. No launch can be detected yet |
| Green blip every 4 seconds | Ready for launch (empty device) |
| Three green blips every 4 seconds | Ready for launch (flights already stored) |
| Dim red glow between the blips | Start-up lock is holding. Launch detection starts once the glow stops |
| Short blue flash after the blip | Battery 3.68 to 3.74 V |
| Short orange flash after the blip | Battery 3.60 to 3.68 V |
| Short red flash after the blip | Battery under 3.60 V. Charge before flying |
No battery flash means the battery is above 3.74 V.
While it is amber, the Nano is learning the pad altitude, waiting for the readings to settle and filling its record of the last few seconds on the pad. It stays amber a little longer if the rocket is being moved around; on a windy pad that never settles, it turns green anyway after a while. If it never turns green, the barometer couldn't give it a pad altitude, so restart it.
Once it is green there's no rush: on a full charge the Nano waits on the pad for just under 5 hours. While it waits it follows slow changes in air pressure, such as the weather drifting or carrying the rocket uphill, but ignores sudden steps such as fitting a nose cone, closing a bay or a gust of wind. Once the pad has been calm for a while it drops to a lower power rate (see emode), and any movement puts it straight back to full rate.
While the rocket sits still on the pad, the Nano fine-tunes the gyro's calibration, which improves the tilt and angle figures. This only needs about a minute of the rocket being still. With orientation set to 9 (auto) it also works out how it is mounted, and locks that in at launch.
A short press of the button (under 2 seconds) plays the last flight number and apogee, and launch detection pauses while it plays. If no flight is stored, it gives one short purple blink.
Detecting the launch
Once the Nano is green and any start-up lock has passed, it confirms a launch in one of two ways:
launch_protection setting, confirms the launch. The thrust has to still be going at that moment, and a knock, a drop or a sideways jolt doesn't count.Either way the log starts several seconds before the moment the launch was recognised, so nothing of the lift-off is lost. Lift-off time is found by looking back to where the climb began, and the launch and rail angles are taken from the pad readings just before it. The flight info page shows which way the launch was confirmed.
| False trigger | What stops it |
|---|---|
| Handling, knocks or a drop | The thrust must be sustained, along the rocket's axis, and backed by a real climb |
| Wind, a gust, fitting the nose cone or closing a bay | The pad altitude ignores sudden pressure steps, and the height has to be held, not just touched |
| Switching on | A short warm-up after every start, plus startup_lock if you set it |
| Carrying the rocket uphill | The pad altitude follows slow changes |
| A USB cable connected | No launch is ever detected on USB |
Set the launch detect height to suit your flight. As a rough guide, use about a quarter of your expected apogee, so around 50 m for a 200 m flight. We wouldn't go below 25 m, so handling on the pad and changing weather can't trip it, or above 100 m, so it still catches a lower flight in good time. The setting and its range are on the settings page.
Recording
The LED blips purple every 4 seconds while the Nano records, with the battery colour after it if the battery is getting low. The flight is held in the Nano's memory and nothing is written to the drive until the save, but a backup copy is kept in a separate area in case the power is lost.
By default recording stops once the altitude has been steady for 8 seconds after landing. It also stops if the log fills or the battery runs low, and everything recorded so far is saved. Burnout, ejection, landing and any extra stages are worked out afterwards from the whole recording.
There is no LED signal at apogee or landing, and the Nano never shuts down for temperature in flight mode, so an ejection charge warming the board can't stop a flight.
Saving the flight
When recording stops the LED turns pink and the save begins. It can take up to about 2.5 minutes for a long log at 833 Hz, and longer on a low battery, so leave it switched on until it has finished.
| LED | What it means |
|---|---|
| Pink | The save has started |
| Red, green, then white | Combining the barometer and motion sensor data (TrueFuse) |
| Red, green, then orange | Removing spikes and smoothing the altitude (TruePath) |
| Red, green, then blue | Writing and signing the log and its flight info page |
| Solid blue, then 20 fast white flashes | Saved and checked |
If the drive is short of space, the oldest logs are removed first. After writing, the Nano reads the log back to check it. If you don't see the white flashes, the check failed: the backup copy is kept and the save is tried again at the next power-on.
If the power is lost before the save finishes, the next power-on rebuilds the flight from the backup copy at a lower resolution, saves it as a normal log marked Recovered, and restarts. It is signed like any other log, so it can still be verified as genuine. There is more on the processing on the TrueFuse, TruePath and apogee page.
After the flight
By default the Nano gives a short red flash and goes to sleep once the flight is saved. Give it a firm shake for a second or two and it blinks the flight number and apogee, so you can read the result before you open the rocket; each shake gives one readout. Press the button or plug in USB to wake it fully. On a low battery it sleeps without watching for a shake, so only the button or USB will wake it.
The maintain_power setting can make it blink the apogee instead. For reading the blinks see altitude blinking, and for everything once the rocket is back in your hands see after landing.