We knew to expect a paradigm shift with the end of the space shuttle program, but this is ridiculous. Mason Peck and his group of forward-thinking engineers are taking NASA’s slogan of Faster, Better, Cheaper to the extreme. Their spacecraft will cut down travel time to Alpha Centauri from thousands of years to just a few hundred, and instead of the $1.7 billion it takes to build a space shuttle, Peck’s ships can be built for an amazing $33.
I might mention that there’s no room for astronauts. In fact, if one were to try and board these spacecraft they would crush it.
Okay, maybe Peck’s Sprites, as they’re called, aren’t going to be the next manned space vehicle, but they could be the first of a new breed of satellites that are so cheap and innovative – they don’t need fuel – they could be an important addition to our satellite-based efforts to study the universe.
In stark contrast to the present approach of sending satellites costing tens or hundreds of millions of dollars for single missions, Peck’s team at Cornell’s School of Mechanical and Aerospace Engineering envision a swarm of wafer-sized spacecraft that sense their surroundings together and send data back to the earth in aggregate.
The spacecraft are called Sprites and they weigh about 10 grams each. Integrated circuits 3.8 cm on a side, they’re literally spacefaring computer chips. This past May the space shuttle Endeavour brought three Sprite prototypes to the International Space Station. Fixed to the station’s exterior, they are currently in the early days of a two year test to see how they stand up to the harsh elements of space.
Compared to your typical satellite the faculties of a single miniscule Sprite are severely limited. The Sprites at the station right now are equipped with seven tiny solar cells, a microprocessor with a built-in radio, an antenna, an amplifier, and special circuitry that activates the microprocessor when the solar cells have stored up enough energy to emit a single radio-frequency “beep.” The beeps not only tell operators on Earth that the Sprites are still functional, they’re data that can be used to estimate the angle of sunlight hitting the chip as an oblique angle will take longer to charge the solar cells than direct light that hits at a right angle. Not the most revolutionary sort of space exploration, it’s a proof-of-principle that will show the Sprites can sense their surroundings as a population of individual sensors – albeit a population of three. When they do it will be first tiny steps towards a new paradigm of distributed space exploration.
The Sprites of the future will do more. As Peck describes in an IEEE article, semiconductors will fit the solar cells, energy-storing capacitors, and “all the memory and processing capability you could want” onto a single chip. These will support experimental payloads such as spectrometers that break down the light emitted by stars and planets, for example, and use it to determine the chemicals that make up those stars and planets. A chip equipped with load sensors would be able to measure impacts made by space particles. Chemical sensors and simple CMOS cameras – essentially your common digital camera – can also be added. With these sorts of eyes and ears, tens of thousands of Sprites could explore space in ways impossible with conventional satellites. Peck describes a scenario in which Sprites in orbit between the Earth and the sun would send a signal when the local magnetic field or the number of charged particles that hit the spacecraft exceed some preset value. Each Sprite will be a single detector and provide just one data point. “But a network of these scattered chips could produce 3-D snapshots of space weather, something no traditional spacecraft, no matter how sophisticated, could ever do on its own.”
But don’t expect the Sprite swarm to be anything like the self-organizing nanobots of Michael Crichton’s Prey that were able to take a car ride in the shape of a human. Sprites simply won’t have the power for realtime communication – each will be acting on its own. Sprite swarms should be achievable, however, by harnessing the grouping power of space’s gravitational eddies and currents. The Interplanetary Transport Network is the vast array of virtual highways that arise from the gravitational pull of the planets and other celestial bodies. In the same way the interplanetary satellites of old were flung around Jupiter and Saturn in a gravity assist slingshot, a much smaller spacecraft could be ferried between planets along the much weaker gravitational forces that exist between planets. Another propulsion source is provided by the light given off by the sun. Photons that are continually expelled by the sun carry momentum. Just as they strike dust particles at the speed of light and blow them out of the solar system, photons could strike the dust-like Sprites and push them to the orbits of Jupiter or Saturn and beyond. Yet another way to steer the Sprites is to use a planet’s magnetic field. A charged particle that is moving will feel the tug of a magnetic field. A Sprite isn’t normally charged, but it could give itself a well-timed electrical charge to change its course of direction. If it found itself in the presence of a very large magnetic field, such as Jupiter’s which is 20,000 times as strong as Earth’s, it could literally follow in the paths of the Voyager and Pioneer satellites and get a particle accelerator-type planetary assist rather than a gravity assist.
If you picture a Sprite right now as something akin to a powerless piece of dust being capriciously pushed and pulled by the wind then you’re thinking along the lines of Peck and his team. “The idea goes back at least 15 years, and it has its origins in “smart dust” – tiny microelectromechanical sensor systems that can be used to measure light and temperature, register movement and location, and detect chemical and biological substances.” He and his graduate student, Justin Atchison, set out to see if they could explore space in new ways, and do it way cheaper. Space shuttle payloads costed about $10,000 per pound to fly. And putting a satellite in orbit costs between $50 and $400 million. At 10 grams each, 10,000 Sprites would weigh 100 kg – negligible as far as space payloads go. And Peck wants to get them down between 5 and 50 milligrams so that photons and magnetic fields could propel them that much faster.
If he succeeds in miniaturizing them further, Sprites may just be our ticket to the stars. At such small sizes the Sprites could travel at speeds fast enough to reach our nearest star, Alpha Centauri, in a few hundred years. That may not sound very fast, but our next best option at the moment – solar sails – would take at least a thousand years to get us there, more than likely longer.
The Sprites represent a paradigm shift in space exploration. Their materialization was made possible by advances in integrated circuit and superconductivity technologies. As these technologies advance further and are manufactured on the nanometer scale, spacecraft like Sprites will become faster and more powerful. It’s hard to say right now what their role in space exploration will be in the coming decades, but one can only expect that role to be as unorthodox as the Sprites themselves.