More-capable cubesats are attracting commercial and government interest
Small, low-cost satellites are coming into their own as a niche industry serving commercial and government markets, building on the free development work provided by a generation of engineering students at places like California Polytechnic State University and Morehead State University in Kentucky.
It is now clear that smallsat technology is leapfrogging beyond the classroom. No longer just a hands-on teaching tool, miniature spacecraft are in serious development as weather monitors, Earth- and space-observation telescopes and a host of scientific probes.
“The genesis for a lot of the work has been in the universities, but we're now coming to a kind of a cusp, or a knee in the curve,” says Charles S. (Scott) MacGillivray, president of Tyvak Nano-Satellite Systems, a two-year-old startup that is gaining serious traction in the market for cubesat components, engineering services and launch integration. “We can start saying 'hey, we can do real missions with these.'”
Presentations at the 27th annual Small Satellite Conference at Utah State University here last week underscore MacGillivray's point.
During last year's conference Tyvak signed a $13.5 milliontechnology-development contract for the Cubesat Proximity Operations Demonstration (CPOD) mission, which will fly two 3U cubesats (each one comprising three 10-cm “cubes” that are each counted as one “U”) to orbit. Once there, the two tiny spacecraft will use a multi-thruster cold-gas propulsion system to fly a choreographed pattern around each other before docking, accomplishing the task with imagery, a cross-linked GPS signal and sophisticated software running on high-performance onboard processors.
Although most of the small-satellite and miniature instruments covered at this year's conference are still in development, the range of topics suggests the next few years will see a dramatic increase in “real missions” conducted with small spacecraft. Among them are “High-performance Spectroscopic Observation from a Smallsat;” “Star Tracker on a Chip;” “Simultaneous Multi-Point Space Weather Measurements using the Low-Cost EDSN CubeSat Constellation;” “Cicero—A Distributed Small Satellite Radio Occultation Pathfinder Mission,” and “TacSat-4: Military Utility in a Small Communication Satellite.”
Until recently, smallsats were considered too limited for meaningful work in space. Designers have been spending a lot of time working on ways to enhance the capabilities, and the payoff is starting to appear. Presenters from the Space Dynamics Laboratory here andin Mountain View, Calif., displayed dramatically different ways to fold a useful Earth-observation or astronomical telescope into cubesats for deployment on orbit. Miniature atmospheric sounders and other weather instruments were hot, as were propulsion systems.
The cold-gas thrusters on Tyvak's CPOD cubesats may not be the propulsion of choice for future smallsat maneuvering. While last year's conference included a hybrid rocket test banished to an abandoned runway outside of town due to safety concerns (AW&ST Aug. 20, 2012, p. 31), tiny electric and “green” propulsion systems using inert and non-toxic propellants such as Teflon were on display this year.
Those kinder, gentler characteristics, highlighted by specialty houses like Busek Space Propulsion and Systems of Natick, Mass., and Digital Solid State Propulsion (DSSP) of Reno, Nev., should allay the fears of satellite operators hoping to defray their launch costs a little by allowing smallsats to fly with them as secondary payloads.
A case in point is Spinsat, which is set for “soft stowage” launch in the pressurized portion of theDragon headed to the International Space Station (ISS) next April. A station crewmember will carry the 22-in. sphere, essentially packed in a fabric bag, from the Dragon into the station and leave it there until its scheduled deployment through the Japanese module's airlock. NASA safety experts approved the mission because the satellite's 12 thruster-clusters burn an inert solid fuel called Hipep, and only when an electric charge is passed across it.
In space, the Naval Research Laboratory satellite will demonstrate the DSSP thruster technology in a series of maneuvers, and also serve as a reflector for ground-based laser ranging to study atmospheric drag. It is one of two very different spacecraft that will be passed through the Japanese airlock and released from the end of one of the station's robotic arms to test a new NASA deployer known as Cyclops.
Engineers atdesigned Cyclops to handle as many different spacecraft shapes as possible, grappling them with a special fixture, squeezing through the airlock tunnel and attaching to the end of the Canadian or Japanese-built arms to release them down and away from the back of the station to avoid recontact. In addition to the U.S. Navy's Spinsat, the Cyclops test in April will deploy a rectangular satellite—Lonestar-2—built by Texas college students.
Neither of the first two spacecraft to be deployed with Cyclops is a cubesat, but Japan and the U.S. company Nanoracks have launched cubesats from the ISS with special spring-loaded dispensers that essentially work like a jack-in-the-box, squiring the tiny spacecraft out in stacks (see photo).
Dispensers have gone a long way beyond the standard cubesat deployer developed at California Polytechnic State University (Cal Poly) called the P-Pod. Planetary Systems of Silver Spring, Md., drew attention in the exhibit hall with noisy demonstrations of its 6U cubesat deployer, and paper presentations covered a variety of dispensing methods for smallsat packages ranging from multiple cubesats to as many as six satellites in the 180-kg (400-lb.) range riding on Moog CSA Engineering'sSecondary Payload Adapter (ESPA) rings.
In the middle is an “Express” adapter for secondary payloads in the 20-50-kg class—under development at the Johns Hopkins University Applied Physics Laboratory in Columbia, Md.—to fill an unmet need.
“In talks with the community over the past few years we've noticed that a need exists for an intermediary-sized mission between cubesats and ESPA-sized vehicles,” says Clint Apland, who presented a paper on the “Express” work. “We've designed, fabricated and will begin to test this hardware next month.”
While the number of ways to get secondary payloads off their launch vehicles is growing, Tyvak's MacGillivray notes a trend to dedicated launch vehicles for small satellites. One of them is a follow-on to the reusable suborbital human spaceflight businesshopes to kick off next year with its eight-seat SpaceShipTwo. The company has started developing a two-stage, kerosene-fueled “LauncherOne” rocket that it will drop from the same WhiteKnightTwo carrier aircraft that will air-launch its human payloads.
“Secondary opportunities are great for technology demonstrators, they're great for educational missions, but as we've been speaking to you and throughout the community [for a little more than a year], you've told us it is hard to build a business case around secondary launch opportunities,” says William Pomerantz, Virgin Galactic's special projects director. “When you can't specify where you are launching from, where you are launching to, when you are launching . . . that is a constraint.”
Virgin hopes to begin flying 200-kg payloads to low Earth orbit in 2016, dropping the LauncherOne vehicle at an altitude of 50,000 ft. from anywhere that has a 9,000-10,000-ft. runway for WhiteKnightTwo. Pomerantz says the company is developing the rocket in-house, including engines and its “simple, low-cost composites structure.” The price of a mission, he says, will be “less than $10 million.”
That could play well with NASA's open-ended spaceflight-technology development program. With $600 million to invest this year, the space technology mission director is a significant potential customer for the smallsat community, and the associate administrator in charge of the program was invited to deliver the keynote address at this year's smallsat conference.
“We're trying to accelerate and invest where we can to push the whole area forward,” said Mike Gazarik. “. . . [T]here are power limitations, but what we're seeing, just like our flight-opportunities program, is a number of technology payloads that can be flown very inexpensively on a suborbital vehicle, which can be flown on a small spacecraft. We're looking at whatever we can find to be able to get to space.”
Most experts at the conference believe that, ultimately, cubesats and other small satellites will find their greatest utility in constellations that combine the capabilities of “swarms” of the relatively inexpensive spacecraft to do more, in some cases, than a single expensive satellite can accomplish. Weather constellations, to cite one example presented this year, can place sensors over a developing hurricane more frequently than today's polar-orbiting weathersats, and can provide higher-resolution data on rapidly changing conditions than the geostationary environmental platforms.
Jordi Puig-Suari, the Cal Poly professor who, with Bob Twigg of Morehead State, pioneered the cubesat standard, continues to push the envelope as an educator even as he works with Tyvak—founded and staffed by Cal Poly graduates like MacGillivray—on commercial projects. This year he presented an analysis of what it would take to launch a constellation of eight 3U cubesats from an Atlas V. It turns out that even a cold-gas propulsion system would be up to the task of stabilizing the constellation around the planet in a single plane after 40 days, with fairly straightforward deployment from the launch vehicle.
“Forty days is not that long,” Puig-Suari says. “It is kind of a commissioning time. So our conclusion is we are ready to deploy constellations today. We don't have to do anything different—or very little different—than what we have right now. The technology, the infrastructure, the systems are in place where we could have a cubesat constellation, at least a single plane, on the next Atlas V.”