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05 Senior Design · UW
Refueling satellite concept render

Refueling Satellite

2023
Lede

Senior design capstone at UW. Designed and analyzed a concept for refueling satellites in low-earth orbit, before they become space debris.

Results
Satellites per mission
10
Propellant onboard
1000 kg
Launch vehicle
Starship

Problem

Dead LEO satellites are a debris problem with an ozone tail.

Satellites in low-earth orbit go inert when their station-keeping fuel runs out, then take decades to deorbit. The trajectory is bad two ways: they clutter the orbital corridor while they're up there, and their re-entry products contribute to upper-atmosphere chemistry that we'd rather not stress further. Extending working life directly attacks both problems.

Approach

Hydrazine top-ups, ten satellites per launch.

Designed a servicer spacecraft sized to ride to LEO on a SpaceX Starship, carry roughly 1000 kg of hydrazine, and visit up to ten clients per mission. Trade studies covered docking mechanisms, guidance and controls, and propellant transfer under microgravity. CAD and drawings down to assembly level, FEA on the load-bearing structure, a custom robotic-arm analysis, and orbital-mechanics work on the rendezvous sequence.

Scope

What the report actually covers.

Problem significance, customer and market, social impact. Fuel types, launch vehicles, docking, guidance and controls. Subsystems (propulsion, structure, fuel tank, thermal) with finalized CAD and a drawing packet of all parts and assemblies. Orbital mechanics with optimal transfer orbits via Hohmann transfer and plane change. Structural and material analysis (theory plus ANSYS). Custom robotic arm analysis for fuel delivery and motor considerations. Spacecraft dynamics, fluid systems, and assembly considerations. A capstone, but a thorough one.

Detail

Two-semester senior design capstone at UW. The team-of-four problem statement: design a spacecraft that can extend the working life of LEO satellites by topping them up with hydrazine, instead of letting them drift inert and eventually re-enter. Picked the refueling angle because the launch side of the satellite economy gets all the design attention and the on-orbit-servicing side has comparatively little. We did trade studies on docking mechanisms, FEA on the structural members, modeled propellant transfer under microgravity assumptions, and worked through the orbital mechanics of multi-target rendezvous. Mechanical engineering at its most fun and least practical.

Gallery
Final spacecraft concept render
Final concept render of the refueler spacecraft.
Labeled spacecraft render with subsystem callouts
Subsystem callouts on the refueler — propulsion, structure, fuel tank, thermal.
ANSYS vibration analysis
ANSYS vibration analysis on the load-bearing structure.
Stack
  • SolidWorks
  • ANSYS
  • MATLAB
  • Orbital mechanics