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Reaction Wheels for Commercial Constellations


“MSCI Reaction Wheels aren’t just for science missions” explains David Cooper, President and CEO of MSCI.


Increasingly microsatellites are being used for commercial constellations to take advantage of their cost effectiveness and shorter development cycles. These constellation designers are embracing these attributes and seeking to leverage the technology developed in partner companies rather than develop it again. They need off-the-shelf subsystems that have proven flight heritage for risk reduction, and cost and schedule effectiveness to meet demanding programmatic needs. MSCI Reaction Wheels fit this category with excellence.


In the late 1990s, MSCI (formerly Dynacon) was contracted by the Canadian Space Agency to build the MOST microsatellite for an 18 month mission to measure the variation in light coming from distant stars. MSCI needed a low cost, reliable Reaction Wheel that would meet demanding technical requirements but wouldn’t take years to procure. In these early days of microsatellites the only Reaction Wheels available were from traditional big space companies and took years to procure.

So MSCI embarked on a development program to build our own. MSCI set out to find commercial electronics that would meet the goals of at least a 5 year mission life (with ample design margin) and LEO orbit radiation requirements. These readily available commercial electronics were carefully selected through extensive radiation testing. From this effort, the MW 200 Reaction Wheel was created and has gone on to be phenomenally successful. Launched with MOST in June 2003, the first operational MW 200’s have logged over 7 years in space with flawless performance. MSCI produces Reaction Wheels in a fraction of the time and cost of traditional big space companies, but does the quality suffer – not a chance. Since October 2010, the MW 200 has successfully completed more than 47 years and counting of operational wheel-hours in LEO orbit on three separate missions.

Whereas MSCI uses commercial electronics, our Product Assurance procedures and processes are fully space qualified. See our Product Assurance section for more details. Ultimately, the proof is in our unblemished flight heritage. See our Flight Heritage section for more details.

In 2003, MSCI developed the MW 1000, a bigger version based on the MW 200, for application in larger microsatellites and small satellites. This larger Reaction Wheel has also been delivered for numerous spacecraft. See our Flight Heritage section for more details.

What has MSCI learned from these experiences and how can it benefit our Customers? MSCI’s Reaction Wheels have been selected for more microsatellite and small satellite constellations than those of any other company, anywhere.


  • More Capability – MSCI’s Reaction Wheels are optimized for use in smaller satellites by employing electronics and mechanicals that provide high angular momentum storage and torque, but still have low mass and volume and meet the limited power budgets. Every wheel has full closed-loop torque and speed control for ready integration into even basic Attitude Control Systems. This frees the ACS design to focus on satellite control. The encapsulated electronics can also accommodate a high precision Systron Donner angular rate sensor for rate aiding to the ACS

  • Flexibility and Scalability - MSCI’s Reaction Wheels are versatile solutions for satellites from 20 Kg to 250 Kg and more depending on satellite mission requirements. The wheels can operate on as little as 12 Volts bus voltage and are rated up to 34 Volts. They can be used in a single wheel configuration as a momentum wheel, or in configurations of 2 or more wheels for various forms of attitude control

  • Cost Effectiveness – MSCI uses carefully selected and configuration controlled commercial electronics that have been proven through multiple radiation tests and years in orbit to be a very cost effective alternative to full Class S electronics. For those customers looking to use our wheels in more radiation intensive scenarios, MSCI has designed a high reliability version of our electronics.

  • Shorter Implementation Schedules – The use of commercial electronics that are readily available allow MSCI to rapidly procure the parts and perform lot-based radiation and thermal tests up-screening all parts in a much shorter timeframe than Class S parts procurement. This means shorter procurement cycles for our customers and allows MSCI to respond to short term requirements.

  • Reliability – Do any of these cost-effective innovations come at a price in quality? No! MSCI has a solid track record of building Reaction Wheels that last. Our own MOST microsatellite is testament to the approach with over 7 years in LEO orbit and counting. Collectively our wheels have more than 65 years in operation without failure. Similarly, our mechanicals have a proven track record both in accelerated life testing and flight. Our MOST Reaction Wheel bearings show no discernible wear after 7 years. We have never had a mechanical failure in a Customer’s Reaction Wheel. See our Flight Heritage section for more details.


To support our people and enable our capabilities, MSCI has made the investment in state-of-the-art staff facilities, clean room, and the test equipment necessary to produce our quality products. We have also built room for expansion, ensuring our facilities are as scalable as our microsatellites. Come see for yourself! FLIGHT HERITAGE

See our Flight Heritage section to read about the flight history of our Reaction Wheels. QUALITY ASSURANCE

Products lacking in the quality necessary to deliver a sound solution are of no use. MSCI’s exacting, menu-based Product Assurance plan ensures every aspect of a project meets with the highest quality controls, and provides options for tailoring solutions to meet each client’s specific needs.

Like to know more? Please contact us at

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MicroWheel 1000 / MicroWheel 200

The MOST microsatellite's outstanding flight heritage — remaining in orbit four years longer than expected and still going strong — has surpassed all expectations without indication of deterioration. MOST’s longevity has resulted in a prodigious amount of research
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We are proud of our outstanding flight heritage that continues to exceed all expectations. It is a testament to the quality of the minds at MSCI and to the excellence of their creations.
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