MBSAT – A Direct Broadcast Satellite for Mobile Users in Japan and Korea

Paper number

IAC-04-M.1.01

Author

Mr. Robert Prevaux, Space Systems/Loral, United States

Year

2004

Abstract

Aerobraking, and generally speaking aeroassistance, is a potentially interesting technique allowing to perform part of an orbital transfer to a lower-energy orbit with no fuel consumption, using atmospheric forces. This concept originates from the early 60’s, and has been thoroughly studied especially in the 1975-1995 period (e.g. “space tugs” concepts for the Space Shuttle and RLVs). Today, the interest of a space-based reusable Orbital Transfer Vehicle (OTV) as a reusable orbital segment for a space transportation system for satellite launching, has decreased because the economical benefit compared to expandable system is still unclear considering existing technologies. Nevertheless, such vehicles are potentially interesting for new kinds of missions, such as on-orbit servicing, constellation maintenance and space-debris related missions, including cataloguing and identification.
This paper describes a new methodology and presents results for the early design optimization of an aerobraking OTV capable of a two-way transfer between LEO and a high energy orbit. This methodology is a simplified Multidisciplinary Design Optimization (MDO) process using a simple modelisation of the vehicle and mission characteristics with a few parameters. Unlike previous works, which are focused individually on a vehicle in a limited domain for the design parameters, this approach offers a global view of the performance accessible for a vehicle within a large domain of weight. The choice of weight-class is particularly important for an aerobraking vehicle, as it determines – along with the heat shield dimensions and orbit parameters – the level of mechanical and thermal load during the aerobraking leg. The method also offers a convenient way to discuss the feasibility of the vehicle considering simultaneously the following constraints: minimum payload weight, maximum vehicle initial weight, technical feasibility of the heat shield, material temperature constraints and optional limitation of heat shield dimension. The latter constraint discriminates between a rigid, one-piece heat shield and a deployable technology.
The proposed methodology is based on the formulation of the MDO process as a bi-objective optimization process (leading to a Pareto front) and the choice of “reduced variables” which reduces the number of degrees of freedom in the problem. This approach has been performed considering two different missions (LEO-MEO and LEO-GEO), two different propulsion technologies (LOX-LH2 and LOX-CH4) and two levels of heat flux limits (500 kW/m ² and 1 GW/m ²). In each case, we discuss the feasibility and performance of a “heavy” vehicle of 18 tons (the payload being an output) and a “small” one with a mandatory 100 kg payload. We also discuss the interest of aerobraking compared to an all-propulsive vehicle, and the necessity to resort to a deployable shield technology.
The work presented in this paper has been performed in the frame of Onera’s CENTOR project (French acronym for “Reusable Orbital Transfer Vehicle Designs”) whose objective is to prepare tools and methodology for studying and designing future OTVs for new kinds of missions.

Abstract document

IAC-04-M.1.01.pdf

Manuscript document

IAC-04-M.1.01.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.