Nanosatellite manufacturer GomSpace is going from strength to strength, fuelled by the innovative small satellite sector and an increased demand for small satellites that can perform a wider range of missions than ever before. In October 2016, GomSpace acquired nanosatellite propulsion specialist, NanoSpace, after establishing a partnership on several customer projects. SpaceWatch.Global’s COO Torsten Kriening spoke to Tor-Arne Grönland, CEO of NanoSpace, about the nanosatellite propulsion business and the potential for much increased demand for propulsion on small satellites in the future.
Tell us about the recent acquisition of NanoSpace 16 months ago by GomSpace. What attracted GomSpace to your company?
GomSpace saw the opportunity to bring in-house propulsion capability to the company as a subsystem of their satellites. If you look at the past decade of cubesat development, there have been many significant changes. The first cubesat was launched in 2003, and between 2003 and 2013, a great many more have been lofted, but very few -if any- with propulsion. We launched our first cubesat with propulsion in 2015 and now it’s becoming increasingly popular. There is growing activity with companies developing propulsion for cubesats. The main reason for wanting propulsion is obvious. You can do much more with a satellite that has propulsion than with a satellite that doesn’t. As a leading provider of cubesats, GomSpace felt that the business would benefit from adding propulsion as an option to their customers.
What kind of propulsion are you offering and what is the purpose on a cubesat?
Let’s start with the functional benefits of having propulsion on a small satellite. Once a satellite has been dropped off by the launch vehicle it can make good use of a propulsion system. For example, it might be that the satellite is dropped off with a too high spin rate and you can use propulsion to stabilise the spacecraft. Cubesats are often deployed with a large number of other satellites. Let’s say that you have a mission comprising a constellation of cubesats – whether it’s two or two hundred it doesn’t matter. At the moment that they are tipped off from the launcher you will probably want to spread them out into some form of constellation. This is another reason for having propulsion. If you don’t have propulsion you have to rely on differential drag and it will take you months to get your cubesat into the right place.
When the satellite is established in its orbit, you might receive an email warning you of a potential collision -at least if you’re in the popular orbits. With propulsion, you can do something about that. Collision avoidance is something that we are heavily involved with. As soon as you receive a warning, you can start to move out of the way using the satellite propulsion system.
Another reason would be if the orbit requires adjustment. It can be used to adjust the altitude, control the distance to another satellite or compensate for drag or disturbances. In all these cases you need propulsion. Then, at the end of life, you need to de-orbit the satellite and this is something that is becoming more and more important as you don’t want to leave debris up there in orbit. Propulsion is really crucial to get the satellite out of the way.
You mention de-orbiting. Space Situational Awareness (SSA) is becoming even more of an issue today, so how do you manage your last bit of fuel reserve for de-orbiting?
You have to plan that right from the beginning so that you reserve a portion of your propellant for the end of life manoeuvre. This is standard procedure and this is how it has been managed for many years with the big satellites. This is also what we are doing for our upcoming missions. If you look at a typical customer mission, the single biggest fraction of propellant will be used for de-orbit. All the other things such as station keeping, collision avoidance, fine-tuning the orbit; they are relatively cheap to do in terms of consuming propellant. However, de-orbiting takes a lot of propellant.
What percentage does de-orbit consume?
More than half is typically allocated to de-orbit. Propulsion can be a big part of the satellite’s volume and that is driven by the operator’s requirements and, again, more than half of that requirement is for de-orbiting. Let’s take GOMX-4 as an example. This mission comprises two 6U cubesats that were launched on February 2nd, and their propulsion occupies roughly 1U of the spacecraft. That is a relatively small portion of the spacecraft. However, on the other hand, GOMX-4 does not require a huge amount of propellant because the orbit is very low from the start – about 500km – so it will perform a natural de-orbit at the end of life. We would stay within the 25 year limit even without propulsion since the spacecraft are in such a low orbit. De-orbit is more of an issue when you launch to higher orbits.
What about the trends in propulsion? With the big satellites there is a clear tendency to go electric. What kind of propulsion are you using and what are the trends as we go forward?
There is a lot of effort currently going into developing electric propulsion for cubesats. At GomSpace we have R&D projects aiming for electric propulsion. That’s not on the table today, though. What we have today is cold gas which is mature and reliable. We also have resistojet -meaning that we heat the gas to improve the performance, but electric propulsion will come in due course. There is no doubt about it. That will also take cubesats to the next level and this is the point where we can do interplanetary missions and other ambitious projects using nanosatellites.
On the other hand, it’s important to bear in mind that it’s the same for propulsion of smallsats as for big satellites. There is not one technology or one system that that fits all. It’s like buying a car. Cars come with many different power sources such as gasoline, diesel, gas, hybrid, electric. Different missions need various kinds of propulsion so all the different kinds that we use on the large satellites: cold gas, chemical, electrical, bi prop, mono prop, green propulsion; these technologies will most likely appear in miniaturised versions for nanosatellites. Propulsion will be a commodity and the offering will be a full palette of different technologies. We will be there to make that happen.
For 2018, what is the rough number of satellites you are planning?
If you look at what we have announced on our order books, we are on board a couple of large constellations, so already there we are talking about several hundreds of satellites with our propulsion system on board the coming few years.
You earlier spoke about the possibility of small satellites being used for interplanetary missions. What is your vision for the future? Do you have ideas about putting satellites into a lunar orbit or in the orbit of other celestial bodies or is that too far into the future?
No, not at all. That will happen and there are studies that have already been done by ESA, for example, to have cubesats as relay satellites and to perform asteroid missions. However, these are few and very exotic science missions which tend to be very high-profile. At GomSpace, we are very much engaged in the commercial market and that is mainly in Low Earth Orbit (LEO). The real benefit of cubesats is LEO constellations where we can use them to improve services and life on Earth through the provision of communication and data from space. So that is really what we are aiming for. The high profile one-off missions will always be there and they are important to serve as either scientific missions and/or lighthouse projects which keep people inspired.
SpaceWatch.Global thanks Tor-Arne Grönland of GomSpace for the interview.
