Space-based systems are the last bastion of handcrafted, custom-built technology. The unit volumes are small. The intervals between one procurement cycle and another are long. The rigors of launch and the hostile on-orbit environment are severe.
These factors make it hard to take advantage of mass-market economies or gain leverage from previous engineering efforts.
Challenging past practice, though, are Internet standards that are proving to be a capable tool kit for spacecraft designers.
Technologies can evolve at different rates and make quantum leaps at different times, and the vendors that provide a given subsystem can change from one phase of a program to another, but standard protocols and off-the-shelf implementations can mitigate these disruptions.
I spoke with William Ivancic, a senior research engineer at NASAs Glenn Research Center, in Cleveland, about an effort dubbed CLEO, or Cisco router in Low Earth Orbit.
That router is a single circuit board, only 4 inches square, and it required surprisingly little modification for NASAs use.
"All they did was remove wet capacitors and put in dry capacitors, put in lead-based solder, replace the plastic connectors with hard-wiring, and put a heat sink on the router," Ivancic explained.
If the system were more radically redesigned for space use, he added, its modest 10-watt power consumption would be further reduced because line drivers engineered for normal ground use exceed intraspacecraft needs.
By adopting a standard platform, Ivancic said, he achieved considerable schedule improvements, essentially defining an entire combination of space and ground systems in less than 18 months.
Hes sure he couldnt have met this schedule without the leverage he achieved by adopting IP as the foundation.
The major benefits, he said, were IPs "interoperability, peoples understanding of how it works [and] the tools."
An unexpected benefit, Ivancic said, was the full-spectrum support of a general-purpose operating system, Cisco IOS.
This gave him considerable flexibility, and he found himself questioning the conventional wisdom that stripped-down, purpose-built systems are a better choice in space than general-purpose systems with larger resource requirements and more modules that can harbor unexpected problems.
"People are always saying, You want to skinny down IOS; you get more reliable when you take things out, but theres a lot more experience in working with it fully up," he said. "There are all these tools that you can be clever with, things you wouldnt be able to do with nonstandard stuff."
He said he particularly liked the degree of autonomy he was able to put into the spacecrafts systems, with the router redirecting data flows in different situations: "You can use the router to route between assets onboard, even when youre not connected—you can write chronology rules."
There are further advantages that come from commonality of space-based and ground-based systems.
Weve recently seen how fragile ground-based infrastructure can be in the face of natural disaster.
Rick Sanford, director of Ciscos Global Space Initiatives group, hopes the spread of standard protocols and systems into space will lower the barriers between whats up there and whats down here.
"The biggest change is getting people to think differently about the space business," Sanford said, adding that we clearly need something better than what came after Hurricane Katrina: "I saw a picture of two police officers, one holding a ladder while another held up a cell phone looking for a signal."
That has to be replaced, he urged, and I agree, by "making the space assets an integral part of the backbone of the network."
The engineering challenges of ground and space integration arent trivial.
Rapidly moving low-Earth-orbit satellites pose problems of Doppler shift and the continual transfer of signal paths from one satellite to another.
Id rather solve those problems, though, than run optical fiber to Antarctica or defend a cell phone tower from a tornado. Theres plenty of room for network improvements in space.
Peter Coffee can be reached at email@example.com.
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