Murphy's Law: Orbiting Cubesats On Demand

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August 26, 2020: A New Zealand firm has developed a jet powered Aurora UAV that can fly to an altitude of about 31 kilometers and then launch a rocket carrying small satellites into LEO (low earth orbit). The MK-I Aurora was built and flight tested in 2018. The larger MK-II Aurora has been built and is large enough to carry an expendable rocket-propelled satellite delivery vehicle that can put up to 100 kg (220 pounds) of satellites into LEO. Based on test results the MK-III Aurora will be built and be able to fly several missions a day from any airfield. This allows small satellites to be put into orbit for about $50,000 each. This is several times less than it costs when using multistage rockets. With MK-II and Mk-III Aurora the expendable rocket that puts the satellites into orbit accounts for only about six percent of the aircraft weight. While innovative and economical, Aurora is not a new idea, just a better implementation of it.

Aurora is a novel evolution of earlier efforts that used the same concept to launch ASAT (anti-satellite) missiles from high-flying aircraft. ASAT missiles are not new and back in the 1980s the U.S. developed and tested both ASAT missiles (ASM-135) and air-launched satellite launcher rockets (the Pegasus). Back then the U.S. Air Force developed the ASM-135 for knocking down LEO satellites by using a 1.2 ton missile launched from a high flying jet fighter. This was done in response to news that Russia was developing a similar system. The Russian system relied on killsats and was never that effective. A successful test of ASM-135 was conducted in 1985, but the program was shut down three years later because the Air Force preferred to spend the money elsewhere.

A little later, in the 1990s, a civilian firm (Orbital ATK) developed, tested and built Pegasus air-launched, from a B-52 or modified large airliner, three-stage solid fuel rockets for putting small (up to half a ton) satellites into LEO. The first version of Pegasus weighed 19 tons and the latest one 23 tons. Between 1990 and 2016 Pegasus was launched 43 times and was successful 93 percent of the time. Most of the failed launches were early development models. In other words, Pegasus is still in use and the Air Force has admitted that the ASM-135 could resume production and be even more reliable, effective and cheaper because of advances in missile and guidance tech since the 1980s.

Aurora takes advantage of advances in UAV and small satellite technology. In the late 1990s several countries in the West (especially the U.S.) began developing very small satellites mainly because the technology had improved to the point where small was affordable and useful. The earliest of these ultrasmall satellites developed by the U.S. Department of Defense were called CubeSats. That is, their volume was no more than one liter (10x10cm or 4.1x4.1 inches) and weighed no more than 1.3 kg (three pounds). The military got the idea from the increasing use of commercial nanosatellites (which weigh no more than 6.8 kg/15 pounds). The U.S. military launched its first CubeSats in 2008 (piggybacking with a larger satellite that had unused space in the payload nosecone).

It was quickly proven that CubeSats could be used for photo or electronic surveillance, or communications. The rapid advances in communications and sensor technology in the early 21st century made it possible to build a useful reconnaissance satellite weighing less and less. A tiny satellite like this includes solar panels to provide power. A British firm pioneered this technology in the 1990s and made it possible to get scientific satellites in orbit for a fraction of the usual price. Since 2008 nearly a thousand CubeSats (or similar designs) have been launched and the number is increasing each year. Most of the 173 micro-satellites used in the recent Soyuz and PSLV launches were based on the CubeSat design. That standardization also allowed for the establishment of standards for placing many micro-satellites in a rocket's final stage, another factor in keeping delivery costs down.

Cubesats are now technically U Class spacecraft and have the same weight and dimensions as before. Cubesats come in different sizes depending on how many single (1U) cubesats are used. Larger (6U) cubesats, which weigh 8 kg (6x1.33) can handle a lot of jobs that previously needed a much larger and heavier satellite. Cubesats of all sizes are increasingly popular for science experiments by smaller organizations, or even individuals, who cannot afford a multi-million dollar satellite that is ten or more times larger and heavier than a cubesat. Over 1,200 cubesats have been launched since 1998, with about 93 percent reaching orbit. That number is expected to double in the next few years because more and more commercial satellite launchers are providing unused space and weight on their launcher rockets for carrying and launching some cubesats. In some cases, the cubesat owners pay for this service while in other cases some cubesats are taken up for free, as a public service.

A satellite launcher like Aurora can get satellites weighing up to 100 kg, or dozens of large cubesats into orbit on short notice and at much less cost than a rocket. That is a useful capability.

 


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