Assessing The Boom In Cubesats

(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

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].

Satellite Systems

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.