Use of Class a and Class C Stellar Engines to Control Sun Movement In

Acta Astronautica 58 (2006) 119–129 www.elsevier.com/locate/actaastro

Use of classA and class C stellar engines to control sun movement in the galaxy Viorel Badescua,∗, Richard B. Cathcartb

aCandida Oancea Institute of Solar Energy, Faculty of Mechanical Engineering, Polytechnic University of Bucharest, Spl. Independentei 313, Bucharest 79590, Romania bGeographos, 1300 West Olive Avenue, Suite B, Burbank, California 91506-2225, USA

Received 29 March 2004; received in revised form 7 July 2005; accepted 27 September 2005

Abstract Two particular stellar engines of class A and C, respectively, are described. When the Sun is the energy source, both of them provide practically the same thrust force. A simple dynamic model for Sun motion in the Galaxy is developed. It takes into account the (perturbation) thrust force provided by a stellar engine, which is superposed on the usual gravitational forces. Two different Galaxy gravitational potential models were used to describe Sun motion. The results obtained in both cases are in reasonably good agreement. Three simple strategies of changing the Sun trajectory are considered. For a single Sun revolution the maximum deviation from the usual orbit is of the order of 35–40 pc. Thus, stellar engines of the kind envisaged here may be used to control to a certain extent, the Sun movement in the Galaxy. However, under the constraints of present day technology this solution is not yet realistic. © 2005 Elsevier Ltd. All rights reserved.

1. Introduction events induce perturbations of the Oort comet cloud, known to be sensitive to the particular galactic orbit of One could imagine that, for various reasons, mankind the Sun, leading to possible comet impacts on Earth [3]. will be faced with the problem of changing the Sun The Sun will steadily leave the main sequence in revolution motion. Avoiding nearby supernovae or ordi- a few billion years, as stellar evolution calculations nary star collisions are examples. Diffuse matter clouds show (see e.g. [4]). The consequences will be a “moist could also be a potential danger. Some studies suggest greenhouse” effect on Earth, which is likely to spell a that during its lifetime the Sun has suffered about ten en- deﬁnite end to life on our planet well before the Sun be- counters with major molecular clouds (MMC) and it has comes a red giant [5,6]. In Ref. [7], one estimates that if had close (impact parameter less than 20 pc) encounters ancient extraterrestrial civilizations exist in the Galaxy, with more than 60 MMC of various masses [1,2]. These then between 0.01 and 0.1 would have been forced to vacate their native planet due to the primary star leaving the main sequence. Problems with feasibility and dy- ∗ namics of mass interstellar migrations [8,9] prompted Corresponding author. Tel.: +40 21 402 9428; fax: +40 21 410 4251. some researchers to propose the so-called “interstellar E-mail addresses: [email protected] (V. Badescu), transfer” (or “solar exchange”) solution [10–12]. In this [email protected] (R.B. Cathcart). case, the Earth (or, more generally, the home planet) is

0094-5765/$ - see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2005.09.005 120 V. Badescu, R.B. Cathcart / Acta Astronautica 58 (2006) 119–129 to be transformed into a planet of a different star. First, the interstellar transfer requires a way of controlling Sun (or star) movement in the Galaxy. Mirror In this paper, we study the amplitude of a possible human intervention on Sun revolution motion. A pre- Ψ vious approach of this subject was performed in [12]. Here we improve the early model and bring in original S contributions. In Section 2 we define the concept of stellar engine and give details about various stellar engine r classes. In Section 3 we develop a model for the motion of the Sun in the Galaxy, based on usual Newton dy- namics. The details of Sun movement are complex but (a) an “average” motion can be defined by using appropri- ate global Galaxy gravitational potentials. The movement is then studied in both the normal (unperturbed) Mirror T case and in the perturbed case, when an additional (stel- r lar engine) thrust force is acting on the Sun. To increase the confidence in results, two different global gravita- Sun tional potentials are used. Finally, in Section 5 we sum- Ψ marize the main findings of our work. Note that the Rp h solution proposed here is not accessible to present day technology.

Ts 2. Stellar engines

A stellar engine was defined in [13] as a device that Tp uses a significant part of a star’s resources to generate (b) work. Three types of stellar engines were identified and Fig. 1. (a) A class A stellar engine (Shkadov thruster [12]). r is denoted as class A, B and C, respectively. A class A stel- the distance between star S and the mirror, the mirror rim angle. lar engine uses the impulse of the radiation emitted by (b) The class C stellar engine proposed in [13]. It is a combination a star to produce a thrust force. When acting through a between a class A and class B stellar engine. Rp is the distance finite distance the thrust force generate work. As exam- between star and inner surface, h the distance between inner and T ple of class A stellar engine we refer to the Sun thruster outer surfaces, the mirror rim angle, s the star temperature; Tp,Tr the temperatures of the inner and outer surfaces, respectively. proposed in [12], which consists of a mirror placed at some distance from the Sun (Fig. 1a). The mirror is situated such that the central symmetry of the solar ra- centered on the star. The “shells” do not necessarily diation in the combined mirror–Sun system is violated have continuous boundaries but they could as well be and, as a consequence, a certain thrust force will arise. imaginary envelopes of a very large number of smaller For a mirror of given surface mass density a balance 3D bodies englobing the star. The inner surface acts exists between the gravitational force and the force due as a solar energy collector. The outer surface is a ther- to solar radiation pressure at a certain mirror–Sun dis- mal radiator. The two surfaces have different but rather tance which remains constant. It was proved in [13] that uniformly distributed temperatures, Tp and Tr, respec- the presence of the mirror makes the star photosphere tively. The existing difference of temperature Tp − Tr temperature increase and it is expected that the star will determines a heat flux from the inner towards the outer change gradually to a different steady state. The ampli- surface. This flux enters thermal engines used for power tude of the change depends, of course, on mirror size generation. Note that for an external observer a class B (see Fig. 2 of [13]). stellar engine has a thermal signature (i.e. Tr ) signif- A class B stellar engine uses the energy flux of the ra- icantly different from the thermal signature Tp of the diation emitted by a star to generate mechanical power. more familiar Dyson sphere (see e.g. Fig. 6 of [13]). An example of class B stellar engine was proposed in This should normally be taken into account by future [14]. It consists of two concentric spherical “shells” SETI strategies. Download English Version: https://daneshyari.com/en/article/1717456

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