In recognition of his outstanding contributions to space flight safety, Dr. Holger Krag was presented with the 2022 T.S.Kelso award by the Space Data Association (SDA). We previously caught up with Dr Holger Krag to discuss his distinguished career path, the most significant industry developments, and his thoughts on current STM regulation.
We now turn to the topics of industry cooperation, the impact of LEO, and the next steps in managing STM effectively.
Is there enough cooperation amongst countries to manage the sustainability of space?
Yes, I would say so.
First of all, we have the Inter-Agency Debris Coordination (IDC) Committee, which is the source of all mitigation guidelines that are now used. This is a great example of collaboration as this involves all major spacefaring nations on expert level. Within our discussions we are sharing experience and data and jointly propose new sets of guidelines on a consensus base. It is a good model for cooperation.
The European Space Agency is another example for collaboration of more than 20 states – everything we do, we do with the support and industry of our member states, under the same rules, which allows for some harmonisation. We make sure that companies from different countries cooperate on certain topics. That is absolutely necessary.
What do you think the next steps need to be to manage STM?
I always see two aspects when it comes to STM. One is the short-term aspect of avoiding interference during flight, and the other is the long-term aspect of preserving the environment for the future.
For the long-term, I see the mentioned zero debris principle with strong technology developments for active removal, and failsafe mitigation as key. Then, to find these zero debris principles being implemented in international space laws, starting with some going ahead and acting as a role model, and then hopefully others signing in, in a similar harmonised approach.
For the short-term, we have many open ends. Operational collision avoidance used to involve an active payload and a piece of debris that you would avoid, following a collision alert from the surveillance system. Now, with an increase in space traffic, it is becoming more normal to face collision alerts with other active spacecraft, which means coordination is required. We have no obligation to respond to a coordination request, and we have no flight rules, such as who must avoid whom. Is the risk perceived the same on both ends? Do we at all know who is the operator of the other spacecraft? In the case of a critical conjunction, it is fundamental to have clarity on who’s going to manoeuvre and by how much, because the risk reduction achieved might be perceived differently by both. At the moment, all this coordination is done more or less manually by the operators usingpragmatic approaches, but with several dozens of such conjunctions appearing in a day this become impracticable.
Within the Space Data Association, some private companies offeri coordination platforms, based on bilateral agreements. There are several ways of doing it, but it always relies on the pragmatism of the players. There’s no framework that clarifies how things ought to be done.
In the past, we have observed that regulators pick up good working principles that have been established in practice and make them the rule. The same principle has been working for mitigation guidelines, so why not for space traffic management?
How do you see the rollout of LEO impacting STM? Do you think enough is being done prior to launch?
There has been an increase in launch rate by a factor of 15 and this is a multiplier to the problem. However, I don’t want to blame new space traffic for our previous mistakes. We haven’t been good at implementing specific mitigation actions in the past, and we know that the technical problems that we had in the past will probably persist in the future.
My worry is that in the end, the future space traffic will not fully tackle these problems and we will get the same failure rates in implementing space debris mitigation as a result of multiplied space traffic. This is why measures such as the zero debris approach, active removal, and technologies for making mitigation failsafe are really important.
Many of the new space traffic made use of orbit regimes that are in low altitudes, which is very satisfying to see because it means they are failsafe in the sense that they would re-enter in short times even hen the spacecraft is no longer functional, because of the increased atmospheric drag. Still, the sheer amount of spacecraft causes the short-term space traffic issue that we addressed earlier. It’s the interference during operations by collision alerts which needs a pragmatic management solution.
There is one additional effect coming with that, and that is the on-ground risk.
On the one side, the trend goes towards smaller space systems in the future with a smaller propulsion system, which is better for on ground safety. But at the same time, we have tenfold the number of re-entry events because the spacecraft are flying low enough in the atmosphere. We need to see if the current practice is good enough to ensure safety on the ground. Even if individual spacecraft are not significant, the accumulation of re-entries might then cause a meaningful risk.
In the future, we might also have to revisit the practice of uncontrolled re-entries and come to a more systematic application of either design-to-demise principles, which means the spacecraft is designed to disappear during re-entry, or controlled re-entry, which means to focus disposal over an ocean area. And both will come with great effort.
Is the act of debris removal easier in LEO?
Active removal is often thought of as simply cleaning space. But it could also be a way to save us on the ground. There are already non-functional heavy objects which pose a threat of re-entry over the next few years, and active removal could deorbit them in a controlled way.
I’m getting more questions from satellite operators who seem to see that it might be cheaper to buy an active removal service, instead of designing future space missions with the means required for disposal and controlled re-entry. That is an interesting development because it would mean another application case for active removal.
The next 5-6 years will be interesting. In the past, we have never, even with our best efforts, achieved 100% reliability in disposing of our space objects. When the zero debris principle becomes applicable, which will de-facto ask for 100% certainty of the removal, we will see an interesting trade off between investing more in robust mitigation actions or rely on active removal. Therefore, we need to make sure these active removal missions work, and are demonstrated to be affordable and that robust mitigation technology is available. The zero debris principle will stimulate a vibrant ecosystem of active removal service providers and a market for such service that will also influence the space insurance market. The latter is expected to play a role to offer products that cater for failed disposal actions by funding the required active removal.
We also need to consider the option of repairing and reusing space systems instead of disposing of them. This may be something to consider for GEO, where launch costs are high, systems are big, and the mission lifetime is often constrained by the propellant. Refuelling and simple repairs could be done as a commercial service. This is where we need to build up a market and offer services to GEO operators in the future. We need to advance the technology and make it happen.