Friday, February 28, 2014

Vanguard & Other Fruit Sized Satellites, Part II

An engineering model of the TRS Mk. II satellite.
Image courtesy Smithsonian Institute, Air & Space Museum
The Vanguard would not be the last small satellite orbited. There would be many others that would follow, though the trend was towards larger, more complex satellites. 
Early on in the Space Age, two sets of satellites bucked the trend.
TRW was contracted by the US Air Force to build a series of small satellites for measuring things like radiation in the Van Allen Belts and the Earth's magnetic field. These were named after the Platonic solids they resembled. 
The first were the TRS, the "Tetrahedral Research Satellites", part of the ERS (Environmental Research Satellites) series. The smallest of the bunch were the TRS Mk. I. They measured 6.5" (162 mm) on a a side. Each face was covered with solar cells, and they had two antennae. Their mass was light, much like the Vanguard 1 satellite, ranging from 1.5 to 3.3 pounds (.9 to 1.5 kg). 
Unlike the Vanguard, there was no specialized launch vehicle; these satellites would be hitchhikers. When they were launched in the early through mid-1960's, they rode up with other USAF payloads, usually on Atlas-Agena rockets. They were not designed to function long, at most only a few weeks, after which they would reenter and burn up in the atmosphere. 
In many ways, these are the ancestors of today's CubeSats, though given the technology for the time, were far simpler. They did seem to start the trend of riding with larger payloads. 
Over time, the TRS Mk.I would be joined by bigger stable mates, starting with the TRS Mk. II, which were larger (around 9"/230mm on a side) and heavier. Other Platonic solid shaped satellites would join them as well, such as the Octahedral Research Satellites (ORS) and others. These would grow in complexity and mass, eventually ceasing to be tiny satellites. As a proof on concept, however, they were something of a success. 
Even smaller, though, were what qualify perhaps as the most unusual satellite system ever conceived, and somewhat controversial at that.
There were concerns during the Cold War about lines of communications being disrupted. As the Space Age began, the only certain way to communicate with Europe and Asia was by means of underwater cables or shortwave radio. Unfortunately, shortwave radio could not always be relied upon; you are bouncing signals off of the Earth's ionosphere, and a direct line of communication could not always be relied upon. Further, the range could vary. The underwater cables were more reliable but were vulnerable to attack.
Even though the idea of geosynchronous satellites had been around since at least 1945 (thanks, Arthur C. Clarke), many felt that this was still an uncertainty. This wasn't the case, mind you; there were groups working on it. However, the paranoia that gripped the United States during that period resulted in some unusual thinking. 
One idea that was popular at the time were passive communication satellites. This is what led to the ECHO balloons, that certainly were not tiny sats. Going to the extreme, it was surmised that perhaps an artificial ionosphere of some sort might be made.
Enter MIT's Lincoln Labs, who worked closely with the Department of Defense. They imagined an artificial ionosphere made up of millions upon millions of tiny dipole antennae, nothing more than .7" (1.78cm) long copper wire "needles". 
This was Project West-Ford.
You, too, can make a full scale model of a West Ford needle!
All you need is #32 gauge copper wire.
Image by Robert Little
There were two launches, one in 1961, the second in 1963. These "needles" would be deployed by a dispenser, which when carrying the tiny copper antennae that would be spun off would have a mass of 88 pounds (40 kg). Only the second one worked, and then not very successfully. In theory, a radio signal could be bounced off this cloud. In practice, not very well. 
There were plenty of concerns about this idea. Radio astronomers were not too pleased, as were their visual cohorts. Those fears proved for naught, pretty much as did the idea. At the time, there was little concern about the notion of orbital debris; by that point in time, there simply wasn't that much of it. Perhaps millions of those little high velocity needles are still in orbit.
A short time later, the first active geosynchronous communication satellite would be launched; Syncom 2, in July of 1963. This ended the idea of passive communication satellites. Considering those tiny high velocity space needles, this was a good thing.
The need for tiny satellites would continue. With improvements in technology, it was getting easier to pack more and more into these small spacecraft. Today, they live on in CubeSats and others. 
Still, most need to "hitchhike". There are some out there who are dreaming of tiny little rockets to lob these very specialized payloads into orbit. This has the potential to truly democratize space.
(Edited - RL)

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