Hold a Lock

A one-shot target goes stale as a vessel moves. A controller repeats the same small ritual: read a coherent snapshot, decide, write a fresh command, wait in sim time. It also knows when not to fly.

The loop shape

~/tutorials/hold-lock.py

import math
from gatos_io import read_json, write_vec, write
from gatos_frames import neg, body_to_cci

base = "/sim/vessels/active"
last_seq = None
while True:
    t = read_json(f"{base}/telemetry")
    if t["controllable"] and t["warp"] <= 1 and t["seq"] != last_seq and all(math.isfinite(x) for x in t["pos_cci"]):
        # CCI origin is the parent body. Reverse position to point at it.
        q = body_to_cci(neg(tuple(t["pos_cci"])), tuple(t["pos_cci"]))
        write_vec(f"{base}/ctl/attitude_target", q)
    last_seq = t["seq"]
    write("/sim/time/alarm", t["ut"] + 0.2)
    open("/sim/time/alarm").read()  # park until sim time reaches the target

The script does not write while paused, warped, stale, non-finite, or uncontrollable. Holding the last valid command is safer than manufacturing a new bad one. This example aims at the parent; swap the pure calculation in the middle for your own rule.

/sim (in guest)

cd ~/tutorials
python3 hold-lock.py
# Ctrl-C, then release the hold if you want manual control.
echo manual > /sim/vessels/active/ctl/attitude_mode

HTTP (host)

# The same loop reads GET /v1/vessels/active/telemetry,
# POSTs its quaternion to /v1/fs/vessels/active/ctl/attitude_target,
# then long-polls /v1/time/wait?until=<ut+0.2>.

Keep hand-written loops near 1×

Named modes and scheduled burns are warp-correct inside KSA. Your own loop gets only sampled snapshots, so hold on warp rather than trying to chase it.

Next, add the numbers that make an orbital decision: Orbital math.

Next: Orbital mathUse live body constants instead of hard-coded Earth numbers.