← All Guides

Voice callouts during flight

When the rocket lifts off, you want to be watching it — not squinting at a phone screen to check altitude. When it comes down and you start walking, you want your eyes on the terrain, not on a compass needle. AltosUI speaks flight data out loud so you can spend your attention where it belongs. This guide covers what the app says, when it says it, and why the speed callouts adapt to what the rocket is actually doing.

Why callouts matter at the field

A rocket flight is short and full of things worth seeing. Ignition, pitch, tilt at motor burnout, the moment the drogue snaps, the main deploying against the horizon — those are the moments you came for. If you are reading numbers on a screen during all of that, you are missing it.

Recovery is the opposite kind of problem. You are walking across uneven ground, possibly through brush, watching for the rocket and watching where you put your feet. Looking at your phone every few seconds to check bearing and distance is both slow and a little dangerous. Having the app tell you those values as you move keeps your eyes where they need to be.

What the app says during ascent

The Flight tab is live during ascent, and voice narration tracks alongside it. You hear two kinds of callouts:

  • State transitions — the AltOS flight state machine moves through pad, boost, coast, apogee, drogue, main, and landed, and the app speaks each transition as it happens. You hear "boost" at liftoff, "coast" at motor burnout, "apogee" at the top of the arc, "drogue" at drogue deployment, "main" at main deployment, and "landed" when the flight state machine decides the rocket is down.
  • Peak values — max height and max speed as they are reached. You are not trying to mentally track the running maximum; the app calls it when it sees a new one.

The result is a narrated flight that matches what you are watching. You do not have to look away from the sky to know what the rocket is doing.

Direction-aware speed callouts

Speed is where callouts get interesting. A flat "speed 40 meters per second" is not useful on its own — you do not know whether the rocket is accelerating upward at motor burn, descending under drogue, or sitting on the ground drifting with a breeze. AltosUI's speed callouts adapt to the sign of the vertical speed:

  • “ascending at N m/s” during boost and coast, when the rocket is still going up.
  • “descending at N m/s” during descent, under drogue and then under main.
  • “speed N” — the neutral form, when vertical speed is below 1 m/s. You hear this at apogee when the rocket is momentarily stationary in the vertical, and on the ground when the rocket has landed and is not moving.

That third case is the one that surprises people first and then becomes obvious in retrospect: without the direction-aware framing, the callout could say "ascending" at apogee (technically true for a moment) or "descending" while the rocket sits on the ground (false in every way that matters). The 1 m/s threshold keeps the app honest at the transitions.

GPS callouts wait for a real fix

Any callout that depends on GPS — bearing and distance during recovery, for example — waits for a valid fix before speaking. The app treats "valid fix" as the flight computer reporting locked with four or more satellites. Fewer than that, or no lock at all, and the GPS-derived announcements stay silent rather than speaking unreliable values.

That is an honest design choice. A bearing from a single-satellite fix is not a bearing — it is a guess. The app would rather be quiet than steer you in the wrong direction. Once the fix comes in, the callouts begin. If the fix is marginal throughout a flight, see GPS uncertainty circle explained for the visual side of the same honesty.

What the app says during recovery

Once the rocket is on the ground and you switch to the Recover tab, the callouts shift job. Instead of narrating a flight you are watching, they guide you across terrain. You hear bearing and distance to the rocket, updated as you move.

This is where the feature earns its keep on foot. You can put the phone in a pocket or hold it down while you walk, and you still hear where the rocket is relative to you. The visual Recovery Map and the AR Recovery HUD give you richer views when you want them; the voice callouts give you the core numbers when you just want to walk. For the full recovery comparison, see walk to your rocket with AR and the Recovery Map.

A typical narrated flight

What you actually hear from the pad to recovery, rough sequence:

  1. Silence on the pad — the rocket is armed, in the pad state, and there is nothing to say.
  2. “boost” at liftoff, followed by periodic "ascending at N m/s" callouts as the motor burns.
  3. “coast” at motor burnout. Speed callouts continue ascending but the number is dropping.
  4. “apogee” at the top. Around here the neutral "speed N" form can appear briefly.
  5. “drogue” when drogue deploys, with "descending at N m/s" callouts under drogue.
  6. “main” at main deployment, still descending but more slowly.
  7. “landed” when the flight state machine sees touchdown. Speed callouts collapse to the neutral form.
  8. Peak callouts sprinkled in throughout — a new max height or max speed when one is reached.
  9. On recovery, bearing and distance, updated as you walk, quiet while GPS is not yet valid.

What this is and is not

Voice callouts are a heads-up assist, not a replacement for the visual displays. The Flight tab is still there, the Map and Recover tabs are still there, and the Flight Report captures the full after-action record. Callouts just mean you do not have to be staring at a screen to know what is happening.

The three-tier analysis story still holds. The voice callouts live at the launch site, on the iOS app, during the flight and the walk back. The deeper work — zoomable multi-channel plots, thrust curves, CSV export — happens later on the desktop with the .telem file and, for records-grade analysis, the .eeprom log from the recovered board.

If a callout sounds wrong or surprising, tell us — the phrasing and the thresholds are the kind of thing that gets tuned by feedback from people using the app in the field. The FAQ covers the other common questions, and support will route anything specific.