Orbital Servicing Tug: Detumble & Graveyard Reboost

1 · Rendezvous

Defunct satellite tumbling in near-GEO orbit.

2 · Detumble (cancel spin)

RCS torque 2.0 N·m

3 · Reboost to Graveyard Orbit

Engine throttle 0%

Time compression 1200×

Telemetry

Spin rate ω

3.00°/s

Altitude vs GEO

−40 km

Δv expended

0.0 m/s

Mission time

0 h

Angular momentum L = Iω

2400 kg·m²/s

How it works

A servicing tug does two distinct physics jobs before it can move a client satellite: cancel its rotation, then raise its orbit.

Detumble (rigid body):
  I dω/dt = -τ · sign(ω)
  L = I ω   (angular momentum)

Low-thrust orbit raise (near-circular spiral):
  ε = v²/2 - μ/r        (specific orbital energy)
  dε/dt = a·v            (tangential low-thrust)
  a = F/m,  v = √(μ/r),  r = -μ/(2ε)

Detumble — a defunct satellite tumbles slowly (a few deg/s) after years without attitude control. The tug's RCS applies torque τ opposing the spin; ω decays linearly until angular momentum L = Iω reaches zero. Firing the main engine on a still-spinning payload would whip it off-axis, so the tow engine stays locked until ω ≈ 0.
Tow burn — with the stack de-spun, a continuous low-thrust electric engine (real GEO tugs use ~mN–N-class Hall or ion thrusters) pushes prograde. Because thrust is tiny compared to the combined mass, the orbit doesn't jump like a chemical Hohmann burn — it spirals outward quasi-circularly, exactly the μ/ε/r relation above integrated over hours.
Graveyard orbit — IADC guidelines call for retiring a GEO satellite roughly 300 km above the operational GEO ring, clearing the slot for a working spacecraft. The simulated Δv to do this (~10–12 m/s) matches real-world mission budgets.
Real numbers, exaggerated view: μ, mass, thrust and the 300 km raise are the true GEO values (μ = 398,600 km³/s²) — only the on-screen ring separation is stretched (~12×) and time is compressed (the Time Compression slider) so an hours-long burn plays out in seconds.

Tug Defunct satellite GEO ring (operational) Graveyard ring (target)

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