One of the biggest problems with sending smaller satellites into interplanetary space is being able to store enough propellant for the extended voyage. Conventional large scale NASA satellites use pressurized gas cylinders that would not be volume or space effective on smaller crafts. Engineers at the University of Michigan are hoping to address this problem and have developed a new propulsion system that could help small satellites explore interplanetary space at 1/1000th
the cost of previous missions. Dr. J.P. Sheehan is a research fellow and science co-lead for the University of Michigan’s CubeSat Ambipolar Thruster (CAT) project. Learn how J.P. and a team of faculty, researchers and students from the University of Michigan Aerospace Engineering Department are using Kickstarter to get the public involved in space exploration.
Meet CAT: CubeSat Ambipolar Thruster
CAT is a new CubeSat propulsion system that uses a liquid fuel and ambipolar diffusion to produce thrust. Unlike previous iterations of plasma thrusters that weigh up to 10 kg (20 lbs) or more, CAT scales down this technology with a thruster and power supply that weighs less than 0.5 kg (1 lb). The heart of the CAT propulsion system lies within its novel thruster design. Propellant is inserted into a quartz plasma chamber surrounded by a solid silver radio frequency (RF) antenna. When RF power is coupled into the plasma chamber, it ionizes the gas to form plasma. The RF antenna excites a Helicon wave within the plasma heating it to temperatures upwards 350,000 °C. A permanent magnetic fixture forms a magnetic nozzle which directs the super-heated plasma out of the chamber via ambipolar diffusion. When using water as fuel, the resulting super-heated plasma stream provides the cubesat a thrust of about 0.2 millinewtons per watt and a specific impulse between 2,000 and 5,000 seconds. The entire system may be powered by conventional space proven solar panels. If all goes according to plan, J.P. hopes to have a CubeSat equipped with CAT launched in 2014 or 2015. The team has applied for a launch date with NASA as the CubeSat needs to be carried into space with a larger satellite.
Advantages and Scalability
Conventional ion thruster propulsion systems use xenon and other noble gases as propellant because the heavier ions can produce larger thrust. A key advantage to using CAT is that it can rely on water vapor or liquid metal as fuel. While the thrust isn’t as large, CAT benefits from a much more efficient thrust that allows the engine to run for much longer durations which in turn accelerates the satellite to much higher velocities than conventional ion thrusters. Water is immediately abundant on comets and asteroids and more readily attainable on Earth than noble gasses like xenon. Furthermore as a liquid it is possible to store more propellant on board and use electrolysis to create the vapor needed for the plasma chamber. Finally one of the greatest limitations for ion thrusters is engine lifetime due to corrosion. CAT avoids this problem by using an RF antenna coiled on the outside of the ionization chamber. As no electrodes are exposed within the chamber, as with conventional systems, corrosion is avoided and a whole new range of propellants becomes available. While CAT is targeted at CubeSats which currently lack a propulsion system, J.P. acknowledges that this technology could be scaled up for larger satellites in the future should they find that water is a feasible propellant and that CAT is successful.
Making Space Exploration More Affordable
While some projects like the Hubble Space Telescope did wonderful things for bringing science to the general public, these projects cost multiple billions of dollars and a little over a decade to complete. The current economic climate makes it difficult to obtain funding for science projects. CubeSats only cost around a million dollars to conceive, develop, build and launch into space. The development cycle takes only 3-5 years, you don’t need the resources of a small country and the development of CAT brings a whole new range of applications into possibility. The new engine would allow smaller satellites to reach the moons of Jupiter or Saturn to scan for signs of life. An array of CubeSats could be used in formation flight to gather spatial data on the ionosphere, solar flares and Earth’s aurora. A fleet of CubeSats could be used as inexpensive network nodes to provide cheap global internet access, better weather data, or even the first interplanetary internet. Need multiple instruments? Simply launch multiple smaller satellites for a fraction of the cost of conventional larger systems in use today. Providing propulsion for smaller crafts brings a whole new range of experiments into possibility. The lower cost means space exploration is now open to the public, and the development cycle for space technology is poised to take off like never before.
Using Kickstarter to Bring Space Exlporation to the Public
J.P. shared with us a few insights on how they were able to set up a Kickstarter campaign for a technologically complex project like CAT. When coming up with a Kickstarter campaign and deciding what rewards to offer for different price levels, they defined a target audience: “People who think space is really cool. Because it is really cool.
” – J.P. There are so many exciting things about space, and they built their rewards around the concept of getting regular people involved within the space program. As homage to the gold record attached to NASA’s Voyager, the campaign allows donors to have their name and personal message laser etched into the gold layer on the exterior spacecraft panels creating the “ultimate interplanetary message in a bottle.
” Other rewards include an engineering model of the CubeSat outfitted with the CAT engine, a mission patch and T-shirt logo. Another way Kickstarter can be used to get people involved in space exploration is in the scale of the program. CubeSats are cheaper and the team is only requesting hundreds of thousands of dollars as opposed to millions. The shorter development cycle means people can fund a particular project and watch it grow, develop and launch into space. They can say “This is the thing that I'm a part of. This aspect of space, this one satellite, that's the one that I'm involved with.”
J.P. acknowledges that gathering public support for a highly technical project like CAT can be an obstacle in and of itself: “No one wants to hear about the electric fields or magnetic instabilities or any of that. And even though that's something that interests me personally, you kind of have to take a step back and say, so what. What is the real important part? What is the end conclusion that you get from those nitty-gritty details?” –J.P.
The end conclusion that J.P. and the team came up with was to distill their project down to the things that people could connect with and relate to. Using water as a propellant is a brand new idea and accelerating a small craft out of Earth’s orbit on water alone is the type of thing that attracts attention. The end conclusion
of CAT is a tiny plasma thruster only 5 cm long that is going to use water to carry a CubeSat into deep space. That’s very cool, and from a marketing standpoint something you can really build a crowd funding campaign around.
Advice for Future DIY Space Projects on Kickstarter
As a final note, J.P. shared with us some key advice about what he wished he knew before attempting to crowd fund CAT. While working on crowd funding CAT they initially started the Kickstarter campaign first and then added Facebook and additional social media platforms as they went along. If they were to do it all again, they would have a concerted effort on all social media fronts at once. Ideally you would want to get social media set up a week or so ahead of time so that when Kickstarter campaign launches you already have a base audience that you can cultivate and grow as the campaign gains momentum. By defining and understanding your target audience, focusing on the core concepts of your project, creating rewards and tying it all together with proper social media coverage, you can give your Kickstarter project the best possible chance for success. Image cc Flickr via Joe Plocki