Steerage To The Stars: The Cheapsat Revolution
As the cost of putting small digital satellites in orbit continues to fall, what can these little explorers do? Businesses, agencies, and scientists want in.
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As secondary payloads lower effective launch costs, the "cheapsat" revolution will rapidly expand, diversify, and differentiate the commercial, military, and scientific exploitation of space.
The spacecraft -- variously called cheapsats, small satellites, smallsats, microsatellites, or nanosats -- are dedicated, single-user, and limited-use satellites that fit under some threshold. These are typical but not definitive:
Cost: <$2.5 million from concept to orbiting hardware
Mass: <100 kg of payload with at most 100 kg additional fuel
Needed payload space: <1 cubic meter
Modern electronics and robotics can pack an immense variety of sensing, computing, and communications gear and capabilities within those limits.
Organizations as diverse as a commercial weather forecasting firm, a news service, the military of a small nation, a big university, the National Geographic Society, Greenpeace, the DEA, and the International Maritime Organization could have significant use for these "little satellites that could."
The real barrier to truly cheap cheapsats has been launch cost. SpaceX tried with the Falcon I, losing its only actual paid payload, and four customers with it, before switching its remaining scheduled cheapsats to the big, reliable Falcon 9. Aside from obvious engineering reasons -- it is better to put a payload on a rocket with a record of successfully getting to orbit -- this also fits what is turning out to be a much better business model for cheapsats: secondary launch.
Secondary launch is steerage to the stars. Just as sailing ships crammed the rudder-line operation space full of impoverished immigrants, big launchers carrying large, heavy, expensive primary payloads are increasingly selling their ballast space to cheapsats.
Contemporary big-lifter rockets lack true throttlabilty (big main engines are all on or all off, once), and need full fuel tanks for structural integrity during liftoff. Without the options of "engines to half" or flying mostly empty, they need ballast whenever they lift less-than-maximum loads to lower-than-highest orbits.
Just as steerage space on an Atlantic packet could be sold at far below primary-customer prices, so can ballast mass capacity on a Falcon 9, Atlas, Delta, Ariane, H2, Antares, Dnepr, Molniya, or Soyuz, to name the systems that already routinely carry secondary payloads. The requisite business structure and technology (see the following slides) are increasingly in place.
Of course, as with steerage, the big customer calls the tune: Typically the launching organization isn't liable for putting your satellite into the wrong orbit, launching on schedule, last-minute bumping, or outright losing the satellite by launch accident. Then again, though the budget sailing ship passenger of days gone by got no compensation if he missed his ship or fell overboard, steerage still pushed the cost down far enough to overrun whole new worlds.
Originally developed for the Evolved Expendable Launch Vehicle (EELV) project that created the Delta IV and Atlas V rockets, the ESPA (EELV Secondary Payload Adapter) is a standard interface that sits between the topmost stage and the main payload, and can deploy up to six 180-kg satellites for a fraction of the cost of launching them separately. A commercial derivative, the SSPS, is manufactured by Moog CSA Engineering. Already, a majority of the world's operating big lifters are ESPA-compatible.
Smallest of the small: CubeSats are 1-liter satellites intended primarily for scientific experiments. The first one went into space in 2003; nowadays literally dozens of them go up every year, most as secondary payloads. Besides various scientific experiments and observations, they also relay ham radio, take pictures of Earth, and provide hands-on experiences for undergrad engineering students who design and build them.
Last year, Orbital Science's Minotaur I launch from Wallops Island carried 29 satellites and two suborbital experimental devices aloft on a single launch.
NASA's Edison Demonstration of Smallsat Networks (EDSN) is a set of experiments underway at NASA Ames to explore the capabilities of networks, teams, and even swarms of small satellites working together. Nothing says that small systems can't achieve big things!
Even farther afield, Moon Express is exploring moving from cheapsats to "cheap landers." Its MX-1, designed to make a soft landing on the moon, would be deployed as a secondary payload, and then its own propulsion systems would allow it to reach the moon, nearby asteroids, and eventually much farther. As Robert Heinlein once remarked, Low Earth Orbit is halfway to everywhere (because half the energy for a spacecraft to go from Earth's surface to anywhere else in the solar system, on a ballistic trajectory, is expended just getting to LEO). Within a couple of years, Moon Express hopes to dispatch an MX-1, the first private moon probe, to investigate lunar resources for future economic or technical development.
Even farther afield, Moon Express is exploring moving from cheapsats to "cheap landers." Its MX-1, designed to make a soft landing on the moon, would be deployed as a secondary payload, and then its own propulsion systems would allow it to reach the moon, nearby asteroids, and eventually much farther. As Robert Heinlein once remarked, Low Earth Orbit is halfway to everywhere (because half the energy for a spacecraft to go from Earth's surface to anywhere else in the solar system, on a ballistic trajectory, is expended just getting to LEO). Within a couple of years, Moon Express hopes to dispatch an MX-1, the first private moon probe, to investigate lunar resources for future economic or technical development.
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