Designing a space debris removal mission targeting a Cosmos 3M rocket body in LEO using a chemical engine and an elechtrodynamic tether to perform the de-orbiting.
During the past years, several studies have been conducted to depict an image of the current state and future evolution of orbital regions, showing that space debris mitigation is necessary. Amongst others, this led the IADC to develop a series of (passive) mitigation guidelines adopted in a 2007 UN resolution. These studies which evaluate long-term debris evolution have indicated that the debris density has reached such a high level, that there will be an ongoing increase of the number of debris objects, primarily driven by collision activity. This effect will manifest itself mainly in the Low Earth Orbit (LEO) region, due to a combination of high spatial densities, high relative velocities and a large number of object crossings. An analysis of potential collisions enabled the selection of a limited number of large, intact objects imposing the greatest risk for future instability of the LEO environment; in fact, on the long term, the large >10 cm objects will play a more critical role. As they contain such a majority of the mass, they can form the source of giant amounts of new, smaller, debris with a cascade effect. The passive mitigation measures currently used do not suffice as an insurance of a stable debris environment for the next years endangering the future of the space mission not only in LEO and an active removal mission to clean became clearly a necessity.
One of the concepts for an active debris removal system (ADRS) consists on using a satellite or an adapted launch vehicle upper stage to enable the collection and de-orbiting of debris elements. The ADRS should be equipped with various subsystems, including a small propulsion system for approaching the debris through a far-guidance orbital maneuver, a tethered space micro-tug (SMT) for performing the close-range rendezvous and a docking system for establishing physical connection with the debris object. Approaching the space debris has to be performed using a chemical engine, because it can assure a quick rendezvous with a high-velocity object such as a space debris in LEO. After the debris is grabbed, the object has to be de-orbited and burn into the atmosphere, as in LEO there is no such option like a cemetery orbit. This could be performed either by the same chemical engine or by an elechtrodynamic tether. Factors that should be considered in choosing the de-orbiting approach are the mass of the system (included propellant tanks or additional batteries), time of de-orbiting, control authority over the whole system (satellite + space debris) to avoid collision during the final stage of the mission and the efficiency of the system.
In this project, we will use the AGI STK software package to study the difference between the two configurations and eventually reach a decision as to which approach is recommended.
 Valery I. Trushlyakov, Matteo Emanuelli, Alexander Ronse, Claudio Tintori; A Space Debris Removal Mission using the orbital stage of launchers, Heinelin “Flight Into the Future” 2011 contest, Moscow 2011
 D.J. Kessler & B.G. Cour-Palais; Collision Frequency of Artificial Satellites: The Creation of a Debris Belt, Journal of Geophysical Research, Vol 83, June 1978, Pages 2637- 2646
 Trushlyakov V.,Jakovlev M., Shatrov J, Shalay V.V, DeLuca L.T, Galfetti L., Active de-orbiting system of SLC upper stages and spacecraft based on hybrid gas rocket engines, Book of 3-th European Conference on Space Science, Versailles, France, 6-9 July, 2009
 Trushlyakov V, Shalay V., Shatrov J., Jakovlev M., Kostantino A., Аctive de-orbiting onboard system from LEO of upper stages of launchers, Proc. “5th European Conference on Space Debris”, Darmstadt, Germany, 30 March – 2 April 2009, (ESA SP-672, July 2009)
 Claudio Bombardelli, Javier Herrera-Montojo, Ander Iturri-Torrea and Jesus Peláez Electrodynamic tethers for space debris removal, 2010,Technical University of Madrid, Spain
Aim & Steps
Using a satellite or an adapted launch vehicle upper stage to enable the collection and de-orbiting of debris elements.
Investigation on objects that can be tracked and disposed of (size, mass, altitude).
Modeling the satellite and space debris.
Mission phases: far approach(1), close approach(2), de-orbiting(3).
Composition of the system proposed (far approach): satellite (+ tether system + micro tug).
Composition of system proposed (close approach): satellite + tether system (20 km) + micro tug.
Composition of system proposed (de-orbiting): satellite + tether system (20 km) + micro tug + space debris.
How to perform de-orbiting after grabbing?
Chemical engine: one or more burns to reduce altitude and provide de-orbiting of the whole system.
Elechtrodynamic tether: using the interaction of the magnetic field with a current that flows in the tether, to generate a force to pull down the whole system through the atmosphere to the ground.
Investigation on object that can be tracked and dispose (size, mass, altitude).
Modeling the satellite and space debris
Investigation on object that can be tracked and dispose (size, mass, altitude).
Definition of launcher and launch site
Initial simulation of the launch
Definition of the orbit
The identification of the orbital region where the space debris situation is more critical is the starting point of this research.
LEO or GEO?
89%of the ~950 operational satellites are either in a low earth orbit (LEO, 300-2000 km altitude) or a geosynchronous orbit (GEO, ~36000 km altitude). Hence, these two regions form the first focus of our selection.
Figure : Distribution of space debris in different orbits
Both have specific characteristics regarding the presence and evolution of space activities, but in the LEO region, satellites and debris elements are quite widely scattered in terms of altitude, inclination and ascending node. This, in combination with the fact that orbital speeds are considerably higher than in GEO, makes both the amount of crossings and the relative velocities of the bodies during these crossings very high. The wide and random distribution of objects also implies that a system of graveyard orbits (as in the GEO case) is not practical. Another critical issue is that manned space-missions are performed at (low) LEO altitudes, making it essential that the risk of collision is minimized to the greatest possible extent. So, as described in , the combination of a higher debris concentration, a large number of crossings and high relative velocities in the LEO region may lead to an exponential growth of debris objects by a future cascade of collisions.
Once the LEO region is defined as a primary target of our investigation, the most critical orbital parameters must be identified to choose a proper target for the mission.
Studies were performed for predicting the probability of collision in the next centuries using NASA’s LEGEND model, based on the past and current debris environment. These studies form the basis of further orbital selection . The collision probability in the next 50 years is higher at the altitude bands containing the highest fragments concentration caused by the catastrophic events of Fengyun 1c at ~850km and Iridium-Cosmos at ~800km. The critical altitude band is extended to 800-1000 km.
Figure - Normalized distribution of predicted catastrophic collisions as a function of altitude and spatial density (1). (Distributions, for objects 10 cm and larger, at the end of 2005 and 2205)
Higher inclinations (60°-110°) are much more crowded as a direct result of the high number of past and present satellites which use these zones to fulfill their mission goals. The peak between 90° and 100° is due once again to the high amount of fragments of Fengyun 1c. Thus, efforts for actively remove debris should focus on objects in those orbits.
Figure - Amount of detected LEO objects per inclination band for 800-1000km altitudes. Results are based on SSN data of October 2010 (using (2) and (3)) and inclination distribution for objects involved in future LEO collisions (4).
Unlike the semi-major axis and inclination, no particular trend can be seen in the right ascension of the ascending node (RAAN) of the current debris environment and future collisions. This is due to the oblateness of the Earth, which makes space debris RAAN a permanently evolving parameter.
Figure 2: Evolution of debris cloud from Iridium 33 and Cosmos 2251 satellite collision in 2009 (5). Image (a) shows the situation at the time of the collision, (b) depicts the orbits of the various debris objects 6 months later.
Figure - Amount of detected LEO objects a function of eccentricity. Results are based on SSN data of October 2010 (2) (3).