Assessing the boom in cubesats
By Debra Werner|September 2017
In 1999, professor Jordi Puig-Suari of California Polytechnic State University and his friend Bob Twiggs, then of nearby Stanford University, devised a standard for building miniature satellites and a device to dispense them from other spacecraft. I spoke to Puig-Suari by phone about the surprising transition of cubesats from purely educational tools to potential commercial moneymakers and even interplanetary probes.
In his words
Spawning a global market
[Cubesats were] truly an educational activity when we started. We probably could see the potential earlier than other people once we started to see how well some of the systems were working and what miniaturized electronics could do. But the initial endeavor was purely a way of doing simple educational satellites.
Why cubesats are so popular
The educational piece was critical because it allowed us to develop something with zero risk. It’s hard to understand coming from an industrial perspective, but if we educated students, we had accomplished our goal and that did not require the satellites to work. We were flying commercial off-the-shelf components even though people said, “I don’t think these things are going to work in space.” Once it started working, that’s when things got interesting because you had performance-to-power and performance-to-volume ratios that were completely unheard of. Suddenly, the electronics revolution applied to space, while before everybody was sticking with TRL 9 components [meaning “flight proven” on NASA’s Technology Readiness Level scale].
P-POD or Poly Picosatellite Orbital Deployer
When we were working on student satellites and everybody was doing their own size and interfaces, it was hard and expensive and complicated to figure out how to fit them in a rocket. There were a lot of barriers to entry. Once that interface with the launch vehicle was clean and solved, that really helped a lot.
Why cubesats aren’t a big debris problem
All the International Space Station cubesats get out of orbit in six months to a year. Out of the 600 and something that have been launched, well over 100 have been on station. Of the rest, everybody is meeting the 25-year rule and most cubesats are in orbit in the range of six, seven, eight years. Look at the Chinese missile test. Something like 3,000 objects came out of that. So we are a relatively small number. Our steady state population is not going to be that large even if we keep up the launch rate.
Cubesat Proximity Operations Demonstration
It’s a very challenging mission. It’s the first time that we will dock two cubesats. We will do autonomous navigation onboard the spacecraft. And we will demonstrate a spacecraft with active propulsion. As we move forward and look at these satellites working in clusters or swarms or formations, all of those technologies are going to be necessary.
Propulsion for cubesats
Cubesats are doing the same kind of things the big satellites are doing. So in the same way that propulsion is good for the big guys, it’s good for the little ones. Sometimes when you are a secondary payload, the launch vehicle doesn’t take you where you want to go. You could take that ride and modify the orbit by using your onboard propulsion. People are talking constellations and large numbers of satellites working together in a controlled way. To deploy and maintain those constellations or swarms, propulsion really helps. Another one is deorbit. If you carry propulsion then you can go to higher orbits where drag will not help you meet the 25-year deorbit rule. The other thing that is becoming really interesting is people are trying to send cubesats far away. People are looking at asteroid missions and lunar missions. Those all require propulsion.
Size of propulsion units
Some of the propulsion technologies that are coming out are a little big for cubesats. People will say, “I have a propulsion system that is 1u,” [one that takes up a 10-centimeter cubical unit within the satellite]. That is a big chunk of my 3u spacecraft. 1u is starting to become a standard for cubesat propulsion, which for 6u and 12u is very nice. For 3u, it’s a big percentage. But if you need it, you need it and you use it.
More orbits for cubesats
The cubesats have all been in low Earth orbit. There are plans to leave low Earth orbit though. Recently we’ve started to manifest things like Mars Cube One. That is going to fly with INSIGHT [NASA’s Interior Exploration using Seismic Investigations, Geodesy and Heat Transport] in 2018. The Space Launch System has a few Earth-escape lunar missions on the manifest. There are people talking about sending cubesats to geosynchronous transfer orbit to do radiation experiments and other things.
Pace of progress
Some of the new cubesat technologies, like the propulsion systems proposed by Accion Systems and Phase Four, are brand new. In the past, going from a new idea to flight would have taken a significant amount of time. The speed at which these things are getting tested is really interesting. It’s great.
Investors backing propulsion startups
That’s completely new. We haven’t had that before.
Flight heritage for propulsion technologies
One of the things that the cubesat community is notorious for is taking a little bit more risk than traditional space has in the past. When you have smaller, lower-cost systems, the ability of people to take some risk and try new things is much higher. Which means as soon as these things are ready to fly, people are going to start putting them on cubesats. People are putting them into designs right now assuming they are going to work.