Skip to content

UC Davis — HDD Reaction Wheels + REALOP CubeSat

FO Project: 106659 — Zero-G Demo of Low-Cost HDD CubeSat Attitude Control
Period: 2020-12-01 – 2023-12-31
TRL: 4→7
Lead Org: UC Davis (PI: Stephen Robinson — NASA astronaut, 4 spaceflights; co-I: Steven Collicott)
Views: 2,671

Summary

Repurposed commercial hard disk drives (HDDs) as CubeSat reaction wheels — reducing cost by 2-3 orders of magnitude ($10-50 vs. $1,000-$10,000+ per wheel). Validated in two parabolic flight campaigns (Jan 2022, Jun 2022), demonstrating 3-axis pointing and stabilization in microgravity. Design openly shared. Technology spreading to other universities: Cornell independently adopted HDD-RWs for ISS CubeSat ("Sailing to the Stars," Crew-11 2025). UC Davis REALOP CubeSat mission (ELaNa) is pending launch in 2026.

Technology

Problem: Commercial reaction wheels are cost-prohibitive for university CubeSat missions ($1K-$10K per unit). University teams that build their own wheels introduce reliability risks.

Solution: COTS HDDs (not the disk; the voice coil motor + spindle assembly) repurposed as a 3-axis reaction wheel system. Cost: $10-50 per wheel. Bidirectional, variable speed. Removes manufacturing risk by using factory-precision components.

Flight Validation

Date Platform What happened
Jan 4, 2022 Zero-G G-Force One parabolic Proved HDD RWs control attitude and angular momentum in microgravity; TRL 4→6
Jun 27, 2022 Zero-G G-Force One parabolic 3-axis stabilization and closed-loop pointing demonstrated; TRL 6→7

Publications

  • Journal of Spacecraft and Rockets (AIAA, 2017): "Hard Disk Drive Based Reaction Wheels for CubeSat Attitude Control" — foundational paper
  • eScholarship: "CubeSat Attitude Control Using Hard Disk Drives as Reaction Wheels"
  • eScholarship: "Computer Vision System and Experiment Design for Parabolic Flight Demonstration of Hard Disk Drives as CubeSat Reaction Wheels" — documents FO parabolic validation

Downstream — Technology Spreading

Cornell — "Sailing to the Stars" (1U CubeSat, ISS deployment)

  • SmallSat 2025 paper: "Hard Disk Drive Reaction Wheel System for CubeSat Architecture" (Sonwalkar, Chalamalasetty, Parina, Bajaj — Cornell)
  • ISS deployment via SpaceX Crew-11, targeted late summer 2025
  • Cornell independently adopted the HDD-RW concept for their 1U ISS CubeSat
  • This is the open-source technology transfer working as intended — design shared, adopted by another university without licensing required

REALOP (UC Davis, ELaNa CubeSat)

  • 2U CubeSat built by 300+ undergraduate students over ~6 years
  • Primary payload: HDD-based reaction wheel demonstration
  • Selected by NASA CubeSat Launch Initiative / ELaNa program in 2018
  • Launch targeted 2026 (ELaNa scheduling delays are common)
  • GitHub: uc-davis-space-and-satellite-systems/efos (flight OS)
  • Secondary: environmental sensors, Earth imaging for K-12 education

Outcome Category

Open-Source Technology Transfer + Educational Pipeline

A new archetype instance: technology proven through FO, design openly shared, adopted independently by other universities. Not commercialized (no spinoff, no SBIR), not infused into a NASA mission — but spreading through the university CubeSat ecosystem. The FO investment generated a public good that is being self-propagating.

Unlike commercial tech transfer (Archetype 3), this doesn't generate royalties. Unlike mission infusion (Archetype 1), there's no direct NASA mission connection. The value is: lower cost barrier for university space research, enabling more CubeSat missions overall.

PI Note

Stephen Robinson (PI) is a former NASA astronaut (STS-85, STS-95, STS-114, STS-130 — 4 spaceflights, 3 EVAs). He joined UC Davis faculty after retiring from NASA. His involvement gives the project credibility and NASA access that a typical university team wouldn't have. The co-I (Collicott) is a fluids expert from Purdue (also worked on propellant management).

Confidence

  • Flight facts: confirmed (parabolic campaigns documented in UC Davis MAE news, eScholarship papers)
  • Cornell adoption: confirmed (SmallSat 2025 conference paper)
  • REALOP launch: pending 2026 (ELaNa schedule)

Key Sources