Simulator
What a session is
The three programs behind every flight, why the first launch of the day is slow, and what to do when one will not start.
When a student opens a lesson, UAVProg starts a session for them: a private machine, running three programs that talk to each other, reached through their browser. It is theirs alone for as long as they are using it.
The three parts
The block editor is where the student assembles their program and presses run.
The simulator is the flight model and the 3D view — the part What the simulator models describes.
A message router sits between them, carrying each command to the drone and each piece of telemetry back. It is the reason the drone reacts as the program runs rather than after it finishes.
All three run together for one student. Nothing is shared between students: a drone flown into a wall affects nobody else’s screen.
What “ready” means
A session goes through three states, and the waiting screen names each one as it happens:
| The screen says | What is happening |
|---|---|
| “Preparing a machine for you…” | A machine is being allocated |
| “Downloading the editor…” | The three programs are being fetched |
| “Starting the drone simulator…” | They are starting up and finding each other |
| “Connected” | All three are running. This is ready |
Ready means all three parts answered, not just that the page loaded. That is why the editor can appear a moment before the drone does — and if it does, the screen says so: “The editor is ready — the drone simulator is still starting…”
Why the first launch of the day is slow
The first session anyone at your school starts that day takes one to two minutes, because a machine has to be woken and the software fetched. Every launch afterwards takes seconds.
The waiting screen says so itself: “First launch of the day boots a dedicated machine for you — this usually takes 1–2 minutes. Later launches take seconds.”
One session per student
A student has one live session at a time. Opening a second lesson in a second tab does not start a second drone; it reuses the one they have. Refreshing, or coming back to a lesson they left, reconnects them to the session they already had.
That is not a licence limit — it is what stops one student quietly holding six simulators open while thirty others wait for a machine.
Sessions close themselves
- After 15 minutes with nothing happening. Two minutes before, the student gets a banner — “Your session will close soon due to inactivity” — with a Stay active button. Anyone actually working never sees it.
- After 4 hours, regardless.
Nothing is lost when a session closes. Completed missions, scores and saved workspaces are all stored on the account, not in the session. Press launch and carry on.
Say this to a class once at the start of term. A student who believes a closed session ate their work will not tell you — they will quietly start again from scratch.
When one will not start
In order of how often each is the answer:
Read the screen and wait
If it is naming a stage and the timer is running, it is working. Give it two minutes. The most common cause of a broken lesson is thirty students pressing Try Again at ninety seconds, which starts each wait over.
Press Try Again — once
A genuine failure says so: “Your simulator session failed to start. This is on us — try again and it will usually work.” That message is accurate. One retry fixes most.
End the session and launch again
If the editor loads but the drone never appears, or the banner says “Connection to your session was lost”, there is a Reconnect button and, beside it, Close session. Closing and relaunching gives a clean one.
Reload the page
Clears a stuck frame.
Suspect the school network
The simulator holds a live connection open to keep the 3D view moving, and some school filters close connections like that.
The symptom is distinctive: everything loads, the drone appears, and then it freezes or never moves. If the same account works on a phone using mobile data, it is the network. The phrase your IT department needs is “WebSocket connections are being closed”.
Report it with two details
Which student, and roughly when. Administrators can look up exactly what happened to that session — every stage it reached, every error, and the logs from inside it. With the name and the time it is usually a two-minute diagnosis; without them it is guesswork.
Related
- What the simulator models
- Missions and scoring
- Running a lesson — the same ground from the teacher’s side