Active debris multi-removal mission concept based on hybrid propulsion

During the last 40 years, the mass of the artificial objects in orbit increased quite steadily at the rate of about 145 metric tons annually, leading to about 7000 metric tons. Most of the cross-sectional area and mass (97% in low Earth orbit) is concentrated in about 4500 intact abandoned objects plus a further 1000 operational spacecraft. Analyses have shown that the most effective mitigation strategy should focus on the disposal of objects with larger cross-sectional area and mass from densely populated orbits. Recent NASA results have shown that the worldwide adoption of mitigation measures in conjunction with active yearly removal of approximately 0.2–0.5% of the abandoned objects would stabilize the debris population. Targets would have typical masses between 500 and 1000 kg in the case of spacecraft, and of more than 1000 kg for rocket upper stages. In the case of Cosmos-3M second stages, more than one object is located nearly in the same orbital plane. This provides the opportunity of multi-removal missions, more suitable for yearly removal rate and cost reduction needs. This paper deals with the feasibility study of a mission for the active removal of large abandoned objects in low Earth orbit. In particular, a mission is studied in which the removal of two Cosmos-3M second stages, that are numerous in low Earth orbit, is considered. The removal system relies on a Chaser spacecraft which performs rendezvous maneuvers with the two targets. The first Cosmos-3M stage is captured and an autonomous de-orbiting kit, carried by the Chaser, is attached to it. The de-orbiting kit includes a Hybrid Propulsion Module, which is remotely ignited to perform stage disposal and controlled reentry after Chaser separation. Then, the second Cosmos-3M stage is captured and, in this case, the primary propulsion system of the Chaser is used for the disposal of the mated configuration. Critical mission aspects and related technologies are investigated at a preliminary level. In particular, an innovative electro-adhesive system for target capture, a mechanical system for the hard docking with the target and a hybrid propulsion system suitable for rendezvous, de-orbiting and controlled reentry operations are analyzed. This is performed on the basis of a preliminary mission profile, in which suitable rendezvous and disposal strategies have been considered and investigated by numerical analysis. A preliminary system mass budget is also performed, showing that the Chaser overall mass is about 1350 kg, including a primary propulsion system of about 300 kg and a de-orbiting kit with a mass of about 200 kg. This system is suitable to be launched with VEGA, actually the cheapest European space launcher

Characterization of nal powders for rocket propulsion

Nanosized metal powders are known to significantly improve both solid and hybrid rocket performance, but have some drawbacks in terms of cost, safety, and possible influence on propellant mechanical properties. Performance enhancement through nanosized metal or metal hydride addition to solid fuels is currently under investigation also for hybrid propulsion. Therefore, a preburning characterization of the powders used in solid propellant or fuel manufacturing is useful to assess their effects on the ballistic properties and engine performance. An investigation concerning the comparative characterization of several aluminum powders having different particle size, age, and coating is presented. Surface area, morphology, chemical species concentration and characteristics, surface passivation layers, surface and subsurface chemical composition, ignition temperature and ignition delay are investigated. The aim of this characterization is to experimentally assess the effect of the nAl powder properties on ballistic characteristics of solid fuels and solidrocket composite-propellant performance, showing an increase in terms of Is caused by the decrease of two-phase losses in solid and a possible significant rf increase in hybrid rockets

Ammonium dinitramide/glycidyl azide polymer (ADN/GAP) composite propellants with and without metallic fuels

Ammonium dinitramide/glycidyl azide polymer (ADN/GAP) composite propellants with or without metallic fuels are most likely candidates for a green alternative to ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) formulations. These ingredients are not only interesting in terms of environmental friendliness but also to overcome the intrinsic performance limitations of AP/HTPB. This paper describes some properties and the burning behavior of ADN/GAP-based propellants, as a function of ADN particles sizes and metallic fuel (Al, AlH3), regarding burning rate, pressure exponent, flame temperatures, particle temperatures, and agglomeration phenomena. Furthermore, aging properties and the formation of pores during sample preparation are discussed. A small-scale motor test of an ADN/GAP/Al propellant demonstrates the basic applicability of ADN/GAP-based formulations

Nanometals in energetic systems: Achievements and future

The characterization of nanometals that are mostly produced by electrical explosion of wires and a comprehensive survey of their usage in different energetic systems are presented. The greatest attention is devoted to nanoaluminum, which is the most common representative of nanometals. The improved kinetic characteristics of chemically reacting systems typical for nanometals (such as burning and detonation rate enhancement for propellants, explosives, and thermites) are studied, and novel paths for chemical reactions are opened (such as nitrides formation in oxygenated media and the catalytic effect on the decomposition of energetic materials). A poor correlation between the powder properties and the slow oxidation parameters was found as a result of very wide scatter in the nanometals characteristics. The burning rate enhancement factor (K) was analyzed for nanoaluminum-loaded solid propellants. The most promising energetic systems are nanometal-loaded solid fuels that are HTPB and ice based with chemically inert matrices

Condensed combustion products from burning of nanoaluminum-based propellants: properties and formation mechanism

The experimental results obtained within a joint international research effort regarding the formation of condensed combustion products from nanoaluminum-based solid propellants (SPs) are reported. Data on the size, structure, chemical composition, and quantity of condensed combustion products (CCPs) as well as conditions of their formation are discussed. On the basis of the collected experimental data, a general physical picture of condensed combustion products formation is portrayed. The results of this study allow carrying out the analysis of good quality propellants using nanoaluminum

Nanometals: Synthesis and Application in Energetic Systems

A survey of metal nanopowders or nanometals (mostly produced by electrical explosion of wires) usage in different energetic systems is carried out with the focus on nanometals combustion efficiency. Improved kinetic characteristics of chemically reacting systems (ignition, burning rate enhancement for propellants, explosives, and thermites) are typical for nanoaluminum, nAl. A weak correlation between nAl properties and the slow oxidation parameters was found as the result of a very wide scatter in powder characteristics. The burning rate enhancement was analyzed for nAl-loaded solid propellants. The most promising energetic systems are nAl-loaded solid fuels (HTPB-based, ice-based, etc.) with chemically inert matrices

New energetic ingredients for solid rocket propulsion

Two metallized solid rocket propellant formulations, based on either the standard AP/HTPB matrix commonly used in space propulsion or the new matrix ADN/GAP, were analyzed. The two formulations in terms of ideal thermochemistry and experimental combustion properties were compared. Thus, a dual-oxidizer system bound by an active binder and loaded with a dual metal fuel was proposed as optimum formulation for space exploration missions. For all configurations, only laboratory level testing was discussed. For motor applications, full-scale testing is needed to ensure a complete mastering of the process