On the Commercial Space Executive Leadership Training discussion board…
- Policy regarding orbital debris removal in space is predominantly at a standstill
- It can take tens of years for tumbling debris to stabilize due to gravity gradient
- Technical and financial challenges face those looking to remove orbital debris are considerable but don’t paint an entirely hopeless picture
INSTRUCTOR CHARLES MILLER:
Is there any “conventional wisdom” with regards to orbital debris that you disagree with?
I have a few pieces of “conventional wisdom” (CW) that I would like to challenge. They have to do with the removal of large pieces of orbital debris.
CW: Large pieces of orbital debris can only be removed with expensive satellites as large as the debris or larger. The capture methods are either cast net (favored by ESA at this time), harpoon or some other grappling or attachment mechanism, or robot arm on the chaser.
I think we can use small and nimble nanosats and microsats that work together to perform removal of large pieces of orbital debris. This means either reentry to splashdown in the Pacific or orbit raising to some graveyard orbit. The nanosats and microsats can be tested rapidly and used for other missions such as solar system exploration. I am actually working on a proximity operations 6U at my day job and the result of this work gives me the confidence to make this statement.
CW: A few large debris removal concepts tow the debris in low Earth orbit and let it decay without paying attention to the casualty risk.
These mission concepts neglect the fact that the acceptable casualty risk (NASA, DoD, French Space Law) is of 1:10,000. Analysis shows that objects over 500 kg, either spent upper stages or satellites, violate that law.
CW: The orbital debris of other nations is their property and interfering with it might start a shooting war.
I’m not so sure about this. I wish I had the $ to a hire a good space law lawyer.
Can one take a space agency, national government, or private company, that by UN treaty owns the debris, to the International Court and prove 1) that the piece of debris is no longer under the control of the respective agency, government, or company since it is either a spent upper stage or a defunct satellite; and 2) that the piece of debris presents a clear and present danger to one’s assets in orbit in particular, and to the community in general? If the case stands one can create a precedent by going for it. However, the process might be expensive. I can’t afford it for sure.
Maybe there is a way to pass a space salvage law after setting the precedent.
INSTRUCTOR CHARLES MILLER:
[Addressing “Technical #1”] While smaller s/c can certainly be developed to rendezvous and dock with a larger s/c, that does not mean those small s/c have sufficient performance to A) alter the orbit of the larger s/c sufficient for de-orbit, and B) to target the re-entry (which is even more challenging) of those large s/c over the Pacific Ocean.
[Addressing “Technical #2] It is a straight-forward systems engineering question to answer what level of performance is needed to properly conduct the orbital transfer. How you solve this issue might be part of your secret.
[Addressing “Political #1] The first part of this is not a secret. Whether the debris is the property and responsibility of the launching nation is straightforward knowledge of any good space lawyer. (It is. The treaties are explicitly clear on this.)
While I don’t think it will start a shooting war, you are extremely unlikely to get a license from the licensing nation (definitely not from the US) to conduct an activity in orbit that will violate international treaty. You just won’t get a license to launch. Existing US law and policy is quite clear on this.
About the question of the property of the space junk: Outer Space Treaty and Liability Convention doesn’t precisely state where the ownership of the State Party of both conventions ends. Generally the state’s responsibility ends when space object cannot be tracked and its ownership cannot be confirmed. The recent clarifications made by UN COPUOS are trying to resolve this issue by obligation directed to states parties of space conventions to announce any changes in its space objects status (still in orbit, deorbited, or shifted into graveyard orbit). A very interesting recent example is the ESA Announcement of Opportunity to propose the deorbit mission for a large ESA-owned piece of space junk (previously Envisat) which had been placed in graveyard orbit. It indicates that after the end of its operational life this space junk piece is still owned by ESA.
You are absolutely right about the nanosats not having the capabilities to deorbit a large piece of debris. They are only used for stabilizing its tumbling. For the time being my mission concept includes a minisatellite that performs the deorbit maneuver, including the attitude control during the maneuver.
As for the policies and launch licenses I’m not sure how to apply for one to deorbit a US object. So, that’s the first hurdle to pass. If you know someone who can help I would appreciate an introduction. I don’t seem to get any traction on my own.
My point about taking someone to court over their orbital debris is about finding loopholes in space treaties. Showing that they no longer exercise control of their space objects and that the respective objects present a danger to life and property is similar, in my (non-lawyer) opinion, to the approach taken to institutionalize a dangerous sociopath.
INSTRUCTOR CHARLES MILLER:
If you believe your mini-satellite can de-orbit a large piece of debris, then you should simplify and only go after those pieces of debris that are not tumbling at the start. A lot of the debris is gravity gradient stabilized. Simplifying in this manner will reduce both the risk and cost of your business strategy.
Later, after you have proven you can de-orbit non-tumbling debris—and have made money doing so—you can tackle the tumbling debris problem.
Right now you have larger problems, which you still have not addressed.
A QUESTION: Since there is plenty of non-tumbling debris, and since satellite technology is pretty common (including nanosats, microsats, smallsats and larger s/c), and since rendezvous and docking technology is rapidly becoming “proven technology”… then why isn’t anybody de-orbiting debris?
What is the problem that must be solved?
Excellent point about starting simple with the non-tumbling debris. However, my understanding is that most of the debris is tumbling, with rates from a few degrees to a few tens of degrees per second. After some time the debris become stabilized by gravity gradient, as you mentioned, and by eddy currents. However it can take tens of years.
For example, Envisat is spinning with 2.7 deg/sec right now and the rate is decaying at about 0.0001 (deg/sec)/day. If the decay rate is constant and all my math is correct then it will be stabilized in about 73 years.
The other challenge is the fact that quite a few of the top 10 most dangerous pieces of debris are spent upper stages that have been observed to have rates of up to 20 deg/s.
I have one direct answer to your question. Sadly it is policy related.
There are no policies or processes in place to license a US company for a mission to perform removal/deorbit of a US object. So our policy makers and regulators are kicking the can down the road. Unless something dramatic happens nobody is going to lift a finger.
I strongly believe that the technical challenges can be overcome, just like you say.
INSTRUCTOR CHARLES MILLER:
If you have data on that [the tumbling debris comment], this would be useful.
Quite a bit of the debris has been in orbit for tens of years. So, based on the physics, there should be quite a bit of it that is not tumbling. The bigger pieces, like the Zenit upper stages with engines on one end, have the center of mass towards one end, and should stabilize. But, again, data is king.
I am not sure this [second policy-related issue cited] is a problem. In the U.S., you could ask for a license from the FAA-AST to launch for the specific mission, and they would then start an inter-agency coordination process to decide if they would give you a license for that mission. It is a general license process to make sure that any launches are consistent with US policy.
Bigelow has recently used this process to ask the FAA-AST to establish an exclusion zone around their hypothetical operations on the Moon. You can read up on it.
The USG has a section of the US national space policy that establishes it as policy to encourage development of solutions. This would inform the licensing approval process.
Assuming that you were a trusted US owned and controlled operator, I don’t think that the US regulatory process is a major barrier.
In general, you have much more significant problems than regulatory.
This gets better and better. To be the regulatory barriers seemed like a show stopper. It’s really encouraging to hear that we could ask FAA for a license. I have checked up their commercial space transportation website (http://www.faa.gov/licenses_certificates/commercial_space_transportation/) and none of the topics applied. I’ll pick up the phone and call them.
Here is the paper on Envisat:
Kucharski, D., Kirchner, G., Koidl, F., Cunbo, F., Carman, R., Moore, C., Dmytrotsa, A., Ploner, M., Bianco, G., Medvedskij, M., Makeyev, A., Appleby, G., Suzuki, M., Torre, J. M., Zhang, Z., Grunwaldt, L., and Qu, F. “Attitude and Spin Period of Space Debris Envisat Measured by Satellite Laser Ranging,” IEEE Transactions on Geoscience and Remote Sensing Vol. 52, No. 12, 2014, pp. 7651-7657
Unfortunately no one has performed a systematic survey of spent upper stages until now. Only a bunch of conference papers showing simulation results. However, I’ve been told that rates from a few deg/s to 10 deg/s are typical – from raw data collected by NASA so far. This is not a major problem because once I choose a set of targets for removal I can commission a study to get their rough rotational rates.
Assuming that I can get a license for debris removal the next hurdle is the non-existent market. There are no paying customers right now, either government or private. I have put together a mission cost of $67M, including $32M for a Lock-Mart Athena IIC launch, to remove an Agena-D upper stage from a 900 km orbit. That’s about $100K/kg. Subsequent missions are quite cheaper but the launch cost is still prohibitive.
INSTRUCTOR CHARLES MILLER:
The market is the real problem.
Who is your customer—your qualified customer—and what would they be willing to pay to clean up orbital debris?If you can answer that problem, and find that customer, the rest of the challenges are much easier.
Exactly. No one is willing to pay for orbital cleanup right now, but the system is extremely fragile, to quote Taleb. The situation is somewhat similar to the nuclear power plant industry; the probability of catastrophic events is very low but the consequences of such events are dire. In the case of orbital debris we know it’s going to happen sooner or later. In the meantime I’m applying for SBIR grants to try to develop closely-related technologies.
The encouraging result of this discussion is that the regulatory process is much more approachable than I thought. I’ll pursue that. Thanks!
Removal of debris is a very big policy issue – involves cameras and proximity ops.
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About Charles Miller: Charles Miller is currently the president of NexGen Space LLC, a space and public policy consulting agency providing client services at the juncture between civil, commercial, and national security. Miller is also a former NASA Senior Advisor for Commercial Space, leading half a dozen NASA commercial space teams. He is also a co-founder of NanoRacks and a founder of ProSpace, both of which are major players in the push to make space exploration more accessible to the masses.
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