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Elmo Rugged Drives Guide Space Missions

Launching rockets to space missions has always posed one of the greatest engineering challenges.
The servo drives guiding the rocket on its path have to be capable of delivering utmost precision while operating under extreme conditions. Elmo’s servo drives are designed to provide solutions to these challenges while dramatically reducing costs with off the shelf products.

Launching a rocket may appear simple – fixed engines ignite, creating downward thrust that sends the vehicle up into the air. In reality, those engines are not fixed at all. Instead, the angle of the exhaust nozzle for each engine must be constantly adjusted to generate a net downward thrust that keeps the rocket balanced and properly directed from the ground to orbit. This crucial task is entrusted to motion control technology in the form of servo motors, servo drives, actuators, and controllers. Unlike the typical factory floor or science lab locations, launch vehicles expose those components to punishing conditions, including extreme temperatures, severe vibration, heavy shock loads, and contamination. Once the vehicle escapes the atmosphere, add vacuum conditions that boil away volatiles, and electronics-killing levels of radiation. Components need to not just perform but be ruggedized enough to survive.

Performance and environmental factors are not the only challenges. NASA’s estimated cost of moving 1 kg of payload from ground to orbit is roughly $20,000. In response, a number of commercial ventures have sprung up with the goal of making space transport both more broadly available and more affordable. When one such company sought to reduce costs by using commercial-off-the-shelf (COTS) components, they turned to Elmo Motion Control. Elmo’s ExtrIQ line of harsh environment servo drives is rugged enough to handle the rigors of launch conditions, even in a reusable platform. At the same time, they are designed for maximum power density, to deliver the torque needed while minimizing weight and space claim. The results bring the organization one step closer to its goals while minimizing headaches.

Motion control for 10 engines

The launch vehicle consists of three parts:

  • The first stage, which propels the rocket from the launchpad to the upper levels of the atmosphere
  • The interstage, which contains the systems that separate the first stage from the launch vehicle
  • The second stage, which further elevates the payload to the desired orbit

The first stage of the satellite launcher consists of nine engines supplied by a single tank of propellant. The exhaust nozzle of each engine is constantly adjusted in q and f  by a two-axis motion control system, with each axis incorporating a Gold Double Bee servo drive from Elmo. Only 47 mm x 36 mm in size, each of these drives can deliver over 10,000 W of power. Like all ExtrIQ servo drives, the Gold Double Bee drives are built to withstand up to 75G of mechanical shock across an operating temperature range of -40° C to +70° C.

Orbital dynamics vary widely depending upon location, date and time, and designated orbit. Although rockets can, and occasionally do take a vertical path through the atmosphere, they more commonly follow a more gradual ascent along a curved trajectory at a shallow angle to the surface. The ability to make small and continuous adjustments to nozzle angle under the direction of a centralized control or makes it possible for the launch vehicle to follow the most efficient and advantageous path to the top of the atmosphere.

The interstage is a primarily pneumatic element designed to remove the first stage from the rocket, preventing the vehicle from squandering fuel to raise an empty tank into low Earth orbit.

The second stage incorporates a single engine and fuel tank that together push the remaining portion of the satellite launcher, including payload, into the designated orbit. The stage II engine initially ignites after stage separation. As with the engines of the first stage, the engine of the second stage can be adjusted in q and f  by a two-axis motion control system. The engine can be restarted multiple times in order to ensure that the load is deployed in a stable orbit.

As the march toward the commercialization of space continues, private launch companies will continue to focus on COTS components wherever possible. Gold Double Bee servo drives combine high power density and reliability in an ultra rugged package. Elmo stands ready to support this growing industry with motion technology that delivers the performance they need with the pricing and availability they want.

The combination enables private launch companies and space agencies alike to get the performance they need with the pricing and availability they want.

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