Orbital debris: resource ladder to the stars
by Al Anzaldua
|The good news is that by remedying the orbital debris situation soon, savings and new wealth can be generated while the cislunar “econosphere” expands.|
Although most of the debris is in low Earth orbit (LEO), there is a considerable amount in medium Earth orbit (MEO) and geosynchronous Earth orbit (GSO). Within two LEO altitude bands, 900 to 1000 kilometers (560 to 620 miles) and 1,500 kilometers (930 miles), the density for the initiation of the “Kessler Syndrome,”2 a cascading chain reaction of collisions leading to uncontrollable growth of debris, may have already been reached.3 Prior to 2007, the principal source of debris was from explosions of old launch vehicle upper stages left with residual propellants and high pressure fluids. China, however, in 2007 intentionally destroyed its Fengyun-1C weather satellite, and in 2009 a non-functioning Russian Cosmos 2251 satellite collided with an American Iridium 33 satellite. One-third of all space debris can be traced to just these two collisions.
The satellite industry is already taking tentative steps to at least not create more debris. For instance, some upper rocket stages now automatically release residual propellants to prevent on-orbit explosions. Still more could be theoretically done in this connection, however, as described below. Unfortunately, there exists no international treaty or authority that can mandate such interventions or technologies, and even with such, orbital debris congestion would remain perilous to working satellites and other spacecraft for the foreseeable future.
Everyone in industrialized societies are stakeholders in having unthreatened, long-functioning satellites and other spacecraft in orbit. Therefore, all stakeholders in the short-term will likely have to pay the tab one way or another, perhaps through increased costs of one kind or another. On the other hand, if no action is taken until there are exponentially growing multi-level Kessler cascades, the tab will be much higher in terms direct financial costs for insurance and satellite replacement and the negative impact of service disruption on various industries and businesses, to speak nothing of the negative impact on our modern way of life.
The good news is that by remedying the orbital debris situation soon, savings and new wealth can be generated while the cislunar “econosphere” expands. The first steps can be taken now to create a sustainable solar system infrastructure, new space enterprises, and sustainable outposts throughout our solar system—and eventually beyond. How all of this could possibly be done will be described below.
Future space debris can be greatly reduced by requiring launch and satellite companies to do several things. These include the use of upper stages that, when spent, automatically release residual propellants to prevent on-orbit explosions; stages or satellites that will transfer themselves into decaying orbits after use; and stages and satellites that deploy sails, balloons, or electrodynamic tethers in order to deorbit. Insurance companies could also conceivably offer lower rates to companies putting space structures in bands populated by satellites with deorbit or parking-orbit features. Although there is no international treaty mandating these steps, the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) did publish voluntary guidelines in 2007.
Beyond future reduction through technology fixes, however, key actors in the space community should be able to remove extant debris to safeguard the destruction of expensive satellites; reuse satellite parts such as antennas and solar arrays, after scavenging them from dead satellites; or rehabilitate dead satellites by refueling and/or repairing them, then putting them back in operation. Who, however, would pay for such removal, repurposing, and rehabilitation, and how could it be accomplished? Also, could some of the technologies used for these three interventions be used for other space development purposes?
There are at least two good reasons for starting orbital debris remediation at LEO. First, it is the area most crowded with debris and therefore most likely altitude band to host the next catastrophic collision. Second, dealing effectively with debris in LEO and higher orbits will generate new space industries, while laying down cislunar infrastructure for future space development. In this latter regard, it bodes well to keep in mind Robert A. Heinlein’s famous quotation, “Reach low orbit and you’re halfway to anywhere in the Solar System.” The point of Heinlein’s statement is that the amount of energy it takes to go from Earth’s surface to LEO (9.3 to 10 km/sec) is roughly equivalent to the energy required to travel from LEO to the planets.
|Key actors in the space community should be able to remove extant debris to safeguard the destruction of expensive satellites; reuse satellite parts such as antennas and solar arrays, after scavenging them from dead satellites; or rehabilitate dead satellites by refueling and/or repairing them.|
At altitudes below 600 kilometers, orbital debris will self-remove within a few years due to atmospheric drag.4 Intervention to remove debris above that altitude should therefore be a primary focus. But how can the removal of such orbital debris be carried out, and who will do it? And how does the recent telerobotics revolution fit into this picture? As it turns out, the Swiss Space Center at Ecole Polytechnique Federale de Lausanne (EPFL), in partnership with private company Swiss Space Systems (S3), is planning to build a family of “CleanSpace” satellites specifically designed to clean up LEO space debris.5 EPFL, with other industrial partners, will build the de-orbiting satellites. S3 is building a Suborbital Reusable Shuttle (SOAR), which will ride atop an A300 jetliner to cruising altitude, at which time the SOAR takes off and, when it reaches 80 kilometers altitude, ejects a spacecraft that later releases the de-orbiting satellite at 700 kilometers altitude. Since the aircraft and SOAR are reusable and utilize standard fuels, the system promises to be cost-effective.
The first CleanSpace satellites are being designed to extend a strong gripper to grab the target and lower its altitude to burn up in the atmosphere. EPFL is planning to have S3 launch CleanSpace One, a prototype de-orbiter outfitted with a gripping device, in 2018. To carry all this out, EPFL is designing a new type of ultra-compact motor and an elaborate gripper mechanism, which will also have to deal with the rotation of the target. The development of these new technologies will not be easy, but, if successful, the potential applications are far-reaching. Such technologies, for example could be modified to deal with various types of targets at various altitudes and orbits, such as near Earth asteroids (NEAs).
The “laser broom” and other concepts simply to remove debris also deserve mention. The laser broom would be a ground-based laser powerful enough to ablate the front surface off a debris target to slow and thereby de-orbit it. Although the US Air Force in the late 1990s worked on a ground-based laser broom design named “Project Orion”6 and a testbed device was scheduled to launch on Space Shuttle mission in the early 2000s, numerous international agreements forbidding the testing of powerful lasers in orbit have impeded the program. Other proposed solutions include using giant balls of aerogel or styrofoam, nets, balloons, and electrodynamic tethers to slow or capture space debris.7
Rather than simply de-orbiting debris or dead satellites, another public-private project is aiming at reuse parts of dead satellites in GSO. The Defense Advanced Research Projects Agency (DARPA), under a demonstration project called Phoenix, is teaming up with the private sector to harvest and “repurpose” (i.e. reuse on a different structure) still functional components from nonworking satellites in GSO to create new space systems at greatly reduced cost.8 Beginning in 2016, the project proposes to remove used parts from retired US government and commercial satellites and re-attach them to nanosatellites launched as secondary payloads, making space debris a resource.
Antennas are likely to be among the first targets, because one of the primary drivers of launch costs is their high weight and volume. To deal with antennas and other satellite parts, DARPA and its private sector partners are developing telerobotically enabled Servicer/Tender (ST) spacecraft to be connected wirelessly to ground and space-based human operators. Because all operators will be within the 75,000-kilometer “telepresence window”—the maximum distance that teleoperations can take place with speed-of-light communications without noticeable lag—they will be able to carry out their operations in real time or near real time, a huge advantage.
Bigelow Aerospace has plans for manufacturing four types of space tugs, at least two of which could have a significant impact on our ability to deal with salvaged antennas and other orbital debris.9 For example, Bigelow’s planned Solar Generator Tug is designed to transport large solar panels to Bigelow habitats or other structures. Another Bigelow vehicle, the Spacecraft Capture Tug, is equipped with two multiple-joint grapple arms for capturing various objects in space, including disabled spacecraft and small asteroids. The vehicle will be able to “return the captured object to a designated location for further actions, such as extravehicular servicing of a satellite at a space station.”
Beyond grab-and-plunge removal and grab-and-reuse systems, possibly using “boom electroadhesion”10 for more efficacy in the grabbing, properly designed service/tender spacecraft could theoretically refuel, repair, or upgrade satellites as needed, thus rehabilitating them at a fraction of the cost of constructing a new satellite and putting it into orbit. Recent advances in telerobotics are drastically changing how we might approach the rehabilitation or enhancement of such spacecraft. The Space Infrastructure Services (SIS) project proposed in 2010 by Canadian company MacDonald, Dettwiler and Associates (MDA) envisioned both refueling and otherwise servicing satellites in orbit telerobotically.11 Although MDA and Intelsat in 2012 cancelled their collaborative agreement to develop the SIS, MDA remains interested in the concept. In addition, NASA has carried out a series of telerobotically-operated satellite servicing experiments on a platform on the exterior of the International Space Station.12
Without an adequate international treaty in place, a tangle of legal issues is likely eventually to arise from attempts to remediate orbital debris. Foremost among such issues is the ownership of debris fragments that any mission would gather or otherwise deal with. Article VIII of the Outer Space Treaty vests ownership of any object or components of an object in the “State Party to the Treaty” that launched it into outer space, and therefore gathering such assets raises a legal obligation to either return them or get permission from the state ahead of time (see “A brief look at the legal and political implications of Japan’s space debris removal plans”, The Space Review, January 27, 2014). Identifying the debris could theoretically be done with specific intact but defunct satellites. With 500,000 objects between 1 and 10 centimeters across, and smaller objects exceeding 100 million, the identification of the most dangerous debris is not feasible.
A related legal issue concerns the possibility that a given remediation attempt will misfire and create even more debris or the outright destruction of a working satellite. Insurance companies could play a role in defraying the economic costs of the latter eventuality, but the cost of such insurance for new debris-remediation technologies is likely to be high, unless careful stepwise testing is done first.
|Orbital debris remediation could be the first step in further expanding a cislunar economy and infrastructure, and this step could be taken in a rational incremental fashion—or we can wait until space debris collisions force us to take desperate and costly measures to save our modern way of life.|
It would seem helpful that to deal with the above-mentioned and other legal issues, international stakeholders, both governmental and private, should work within UN COPUOS to expand and evolve the 2007 voluntary guidelines for orbital debris remediation into an international treaty. Such a treaty could also conceivably generate flexible orbital debris mandates for states and private companies to follow. Whether the treaty would also need to establish an authoritative body to monitor or enforce such mandates is a question that could be addressed as well.
Telerobotic technologies for the removal, repurposing, and rehabilitation of orbital debris are obviously in their infancy and will grow in sophistication as time passes—if public and private stakeholders collaborate in a timely fashion to ensure profits and sustainable businesses. Moreover, space debris remediation businesses could be given great impetus by purposely designing satellites to facilitate their future removal, repurposing, and rehabilitation as needed. Sooner or later in this process, antenna and solar array salvage yards and other orbiting depots will evolve into space complexes holding propellant tanks, satellite and spacecraft parts, and idle spacecraft. Large platforms in GSO could theoretically host multiple satellites and thus possibly get around the current 180-slot limit in GSO. It is easy to imagine depot complexes and other structures further evolving into staging areas for in-space tugs, tankers, freighters, and taxis. Orbiting manufacturing and processing sites for lunar and asteroidal materials could follow, as well as hotels and tourist cruise ships in highly elliptical orbits. Orbital debris remediation could be the first step in further expanding a cislunar economy and infrastructure, and this step could be taken in a rational incremental fashion—or we can wait until space debris collisions force us to take desperate and costly measures to save our modern way of life.
We therefore have the plainest of choices: We can wait until our way of life is threatened with destruction and then pay dearly to rectify the situation, or we can deal with it now and use orbital debris remediation to expand Earth’s economy, build solar system infrastructure, and begin our climb to the stars.
1 NASA Orbital Debris Program Office, “Orbital Debris Frequently Asked Questions.”, November 12, 2013.
2 Kessler, D. J., and B. G. Cour-Palais (1978), Collision frequency of artificial satellites: The creation of a debris belt, J. Geophys. Res., 83(A6), 2637–2646, doi:10.1029/JA083iA06p02637.
3 Lisa Grossman, “NASA considers Shooting Space Junk with Laser,” Wired, March 15, 2011; National Research Council, “Orbital Debris: A Technical Assessment,” The National Academies Press, 1995.
4 Dangerous debris exists at lower levels, however. For example, on two occasions, in 2009 and again in 2011, the crew of the ISS, orbiting at an altitude of about 400 kilometers, have been forced to abandon work and take refuge in the Soyuz capsule while a debris threat passed
5 Lionel Pousaz, “The Time Has Come to Destroy Debris”; Emmanuel Barraud, “Cleaning up Earth’s Orbit: A Swiss Satellite to Tackle Space Debris,” Mediacom; and actu.epfl.ch/news/cleaning-up-earth-s-orbit-a-swisss-satellite-to-tac/. S3 is itself partnering with 12 other companies and one major investor/sponsor (Breitling).
7 J.T. Quigley, “Japan will Cast a ‘Magnetic Net’ for Space Junk,” The Diplomat, January 16, 2014; Aviva Hope Rutkin, “Japan’s Huge Magnetic Net Will Trawl for Space Junk,” New Scientist, January 22, 2014.
8 Paul Dykewicz, “DARPA Advances Plans to Salvage Antennas of Retired, In-Orbit Satellites,” 24 November 2013.
9 Yves-A. Grondin, “Affordable Habitats Mean More Buck Rogers for Less Money Says Bigelow,” NASA Spaceflight.com, February 7, 2014.
10 Colorado-based Altius Space Machines is developing a robotic arm system called the “sticky boom,” which can extend to 100 meters. At the end of the boom is a pad induces electrostatic charges onto any material it comes in contact with, facilitating the grip on such an object. See Jeff Foust, “A Sticky Solution for Grabbing Objects in Space”, MIT Technology Review, October 5, 2011.
11 “Intelsat Picks MacDonald, Dettwiler, and Associates Ltd. For Satellite Servicing,” March 15, 2011; Joel Spark, “MDA, Intelsat Cancel On-Orbit Servicing Deal,” Space Safety Magazine, January 20, 2012; Jeff Foust, “The space industry grapples with satellite servicing,” The Space Review, June 25, 2012.
12 Adrienne Alessandro, “NASA’s Robotic Refueling Mission Practices New Satellite-Servicing Tasks,” NASA Goddard Space Flight Center, May 10, 2013.