Updated: Mar 22, 2020
(Courtesy of 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
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].
NOTABLE: Created cubesat standard in 1999 with professor Bob Twiggs. Two
cubesats built by his company Tyvak are scheduled for launch in October to carry
out NASA’s Cubesat Proximity Operations Demonstration. These satellites will
dock with each other to show how cubesats might be assembled into structures or
be sent to repair or refuel satellites. Tyvak also is building the first cubesats for
interplanetary travel under NASA’s Mars Cube One, or MarCO, mission. Two
radio-equipped cubesats will be launched toward Mars next year to demonstrate
how cubesats can relay data from a spacecraft on a planet’s surface, in this case
NASA’s InSight Mars lander.
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
“If you carry propulsion [for deorbiting], then you can go to higher orbits where
drag will not help you meet the 25-year deorbit rule.” -Jordi Puig-Suari
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. 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.