• Home
  • Current congress
  • Public Website
  • My papers
  • root
  • browse
  • IAC-05
  • D5
  • 2
  • paper
  • A mass optimization technique to mitigate the radiation environmental risk

    Paper number

    IAC-05-D5.2.06

    Author

    Dr. Giovanni B. Palmerini, University of Rome "La Sapienza", Italy

    Coauthor

    Dr. Francesco Pizzirani, Italy

    Year

    2005

    Abstract

    During hypersonic cruising, the high speed incoming flow will have high temperature after being condensed by the forebody of aerocraft, and part of air will be ionized. So it is necessary to study the influence of Magnetohydrodynamic(MHD) control on the flow field characteristics of supersonic diffuser.

    Supersonic diffuser is supersonic viscous channel flow with near constant cross section. Its complicated flow field includes shock train, boundary layer and their interaction. I introduced conventional diffuser Briefly and analyzed its mechanism. Full Navier-Stokes equations based on low magnetic Reynolds number assumption with Favre weighted average mass are used to simulate the flow field. The outcome of the simulation accords with the experimental result.

    I calculated the transformation of flow field character of supersonic diffuser when its adding certain electric and magnetic field. Compared with conventional diffuser, the deceleration and expansion can be realized in shorter distance when proper electric and magnetic field are added, and part of the kinetic energy is transformed into electric energy. Study shows that the position of first shock wave, the position of second shock wave and the length of shock train in the diffuser when certain magnetic field added are 62.19%, 77.74%, 50.18% to the ones of conventional diffuser respectively.

    The technique of MHD control can shorten diffuser efficiently, and the electric energy abstracted from the flow by non-contact means can be widely used in the components of the aerocraft. The application of the MHD technique has great value in optimizing the constructure of aerocraft, utilizing the energy properly and enhancing thrust.

    Radiation environment poses a serious threat to all kinds of missions, both terrestrial (higher belt of LEOs, GTO) and interplanetary. A correct evaluation of the impinging doses, and the adoption of appropriate countermeasures, is mandatory for manned mission, but also important in unmanned ones to be sure of the accomplishment of the goals, without electronics’ or mechanics’ failures. A powerful help is given by the availability of simulation tools which spread from theoretical analysis and are validated by in-situ measurements. These codes are currently able to offer a confident sketch of the particular environment to be faced, and therefore allow for protection to be tailored to the specific mission needs. In fact, a correct design process ultimately translates in an educated trade-off between the reduction of the risk and the constraints to be added, namely shielding structures and use of rad-hard special (and expensive) components. These two engineering solutions apply to the two different kinds of threats, i.e. continuously increasing of “low energy” doses (leading to TID safety/failure limit) and high energy phenomena (leading to single effect, punctual failures).

    This paper presents a technique to improve the efficiency of the protection shielding design while keeping the same levels of safety and reliability boundaries. Specifically, the contribution to the S/C shielding granted by “structural” components (including not only the bare structure but also massive subsystems as batteries, instrument cases, etc) could be evaluated since the beginning of the design. Then, additional placing of S/C components is driven by radiation protection policies by means of a quantitative index (named “complementary shielding function”) indicating the shielding mass to be added in order to preserve the limits of the total radiation doses received during the expected lifetime. Inclusion of intended attitude information, therefore specifying the preferred impinging direction in case of directional anisotropic flux, enhances the benefits of this selective shielding, leading to mass savings in the order of 10-20% of the conventional protection for unmanned LEOs missions due to shielding mass displacement optimization. The technique is intrinsically able to take into account different tolerance levels for the S/C parts and can be applied on a larger scale for manned missions, where it does match the criteria of S/C volume partition in differentially protected areas. Such a remarkable improvement in the efficiency, and therefore in the quality of the spacecraft design comes out from an “ad hoc” use of the information from advanced simulation (such as the SPENVIS code by ESA). The paper intends to detail this approach, showing the advantages to carry on spacecraft design by taking into account safety/risk reduction criteria, and to discuss its applicability to several classes of spacecraft and space missions operating in different space radiation environment.

    Abstract document

    IAC-05-D5.2.06.pdf

    Manuscript document

    IAC-05-D5.2.06.pdf (🔒 authorized access only).

    To get the manuscript, please contact IAF Secretariat.