The Mechanical Components Branch at NASA Glenn Research Center conducted a survey of space mechanisms and transmission systems experts to find the perceived technology needs for space drives.  "Space Drives" refers to transmissions including gears or rollers, bearings, lubricants, seals, etc. used on spacecraft or planetary exploration vehicles.

We asked the experts to give separate ratings within their area(s) of expertise and concern for four types of vehicles:  1) Manned Spacecraft; 2) Unmanned Spacecraft; 3) Planetary Exploration Vehicles; and 4) "Other".

Survey Question:  What will be the most critical technology needs for space drive systems in next 10 to 30 years?

•  What characteristics are most important?
•  What size/power levels are most needed?
•  What speed regimes are most important?
•  What drive concepts should we develop?
•  What technology problems will we face?

Section I -- General Drive Characteristics.

Separate ratings for Manned and Unmanned Spacecraft and Planetary Exploration Vehicles for the highest rated Characteristics.

We included an "Other" category for drive characterstics.  We received the following:

Brush Wear in Vacuum	Stiffness in Actuators	Position Sensors
Life Testing	Launch Load Protection	Elect. Pwr. Trans. Devices
Pitting Under Boundary Lube	Reliability	Cost (small quantity buys)
Linear Motion	Supplier Base

Comments for Section I -- General Drive Characteristics

• Light weight and long-lived mechanisms needed.
• Reliable mechanism hardware (and support) from US based suppliers is problem.
• Test studies about effects of radiation on lubricants is lacking.
• Biggest deficiency in the field of space drives is inadequate life testing, due to ---
  • Limited funds,
  • Lack of time to do unaccelerated life test
  • Lack of recognition of difficulty of making  mechanism last 5+ years.
• Mechanical bearing for aerospace flywheel.
  • Launch while spinning
  • Precision pointing at high speeds, high loads (gimbaled)
  • Magnetic bearings as primary, backup or fault protection.

Comments for Section II -- Needs for Various Size / Power Levels and Speeds

• Nanosat lubrication problems.
• Needs for micro and nano machines still evolving.
• Extreme temperature liquid lubricants.
• Mega-rover needs that far surpass those of the Apollo & Pathfinder rovers
• Small robots for on-board inspection and troubleshooting on Geostationary communications spacecraft/platforms
• Ultra high speed (> 40,000 rpm) for flywheel applications with long life.

Section III -- Needs for Development of Drive Concepts

Comments for Section III -- Needs for Development of Drive Concepts

• Harmonic drives need better lubricants for long life.
• Gear systems could benefit from light, robust, low cost anti-backlash devices.
• Worm drives are unreliable due to lube problems but alternatives exist so no need to solve the problem.
• Alternate cost effective and lighter geartrains are important.  (These must have low ripple and backlash for control applications.)
• Most drive systems need efficient light weight high ratio speed reducers.
• One shot gear and drive lubrication benefits from low contact stresses

Section III -- Technology Problems Anticipated

• Get "Gray Beards" to teach youngsters to design reliability into the product early.
• Life/load capacity issues with reduced sizes and longer mission lives.
• Precision gear sets for fine pointing applications.
• Wide operating temperature ranges will affect drive performance.
• Lightweight designs.
• Technology not ready for long life, high power, hostile environments.
• Micro/nano tribology technology may not advance fast enough to ensure reliability.
• Precise motion control (stepper motor) with high torque capacity.
• Shortened life due to operation in hostile environments.
• Low torque operation over wide temperature range.
• Repair / replacement on planetary surfaces or space station.
• Long duration reliability in extremes -- hot or cold, vacuum of Moon and Mercury.
• Reduce cost while improving performance, mass and reliability.
• Credible accelerated testing for increasing mission & storage life requirements.
• Vendor supply deteriorating as space becomes unprofitable and loses its "cachet".
• Lubrication loss or breakdown.
• Lubrication/Life/Pitting.
• Maintaining lubrication during very long term missions.
• Nanosat lubrication problems.  Extreme temperature liquid lubricants.
• Inadequate lubrication in non-oxygen, dusty environment.
• Sealing liquid lubricants to prevent contamination.
• Liquid lubricant replenishment in a zero G environment.
• Development of "oil free" systems for planetary surfaces.
• Longer lasting dry lubes for cryo / high radiation environments.
• Gear Train Efficiency -- reduces cooling needs.
• Efficient method of cooling gears in zero gravity.
• Seals -- Keep the lubricant in and abrasive dirt out.
• Life of lubricant in space environment (vacuum, thermal cycling, effect on wear).
• Management of liquid lube system.
• Replenishment of solid lubricants.
• Grease lubricant gear pitting life operating in Regime 1 for long life/high load.

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Last modified 28 Nov 2006