Wednesday, May 9, 2012

Space Tugboat Could Help Move Inexpensive Payloads in Orbit

Space Tugboat Could Help Move Inexpensive Payloads in Orbit:

Image: Spaceflight Inc.
A Seattle company has announced plans to build a new spacecraft that, like its Earth-bound counterparts, is all about moving other vehicles around. Spaceflight Inc. is designing what it’s calling the Sherpa to fulfill the need for an orbital tugboat that can move payloads, such as satellites, to different orbits around Earth.
Cost is usually the single biggest hurdle for delivering a payload into orbit. To save money, some space-bound payloads will hitch a cheaper ride as a secondary payload on an existing launch if there is space available. The downside to this hitchhike approach is you are stuck going to the same place in orbit as your host, which might not be the ideal spot. The concept behind a space tug is to offer greater flexibility for these secondary payloads to be moved to a better orbit than where the ride is taking them.
Jason Andrews, President and CEO of Spaceflight, says the Sherpa will allow for more access for small and secondary payloads on existing launches. “Sherpa builds on our Spaceflight Secondary Payload System (SSPS) by incorporating a propulsion and power generation system,” according to a press release, ” as well as place them in an orbit other than the primary payload’s orbit.”
The idea of a space tug is not new. A European company tried to build a case for its “orbital life extension vehicle” during the early 2000s. Orbital Recovery planned to add life to satellites — and possibly even the Hubble Space Telescope — that had depleted their onboard propellant and would therefore fall out of the proper orbit, rendering them useless.
In contrast, Spaceflight Inc. is focused on pushing or pulling the burgeoning secondary payload marketplace. The tug itself is little more than a ring frame with enough power and thrust to host and move payloads around in space. The Sherpa is designed to provide as much as 400 meters per second change in orbital velocity for low earth orbit. A second model will be capable of up to 2,200 meters per second changes in velocity for geosynchronous orbit.
The company is aiming for the Sherpa’s first demonstration mission in early 2014 and the first commercial mission later that year. The company will be using SpaceX’s Falcon 9 rocket to launch the space tug into orbit where it will then be ready to perform its duties.

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