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Solar-powered space flight: Nomenclature

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We use the following nomenclature throughout these pages:

 

 = angle that first (larger) mirror makes to x-axis at distance  from x-axis

 = angle that tangent at k’th point on i’th mirror makes to x-axis (or 90° if  or )

 = magnification of mirror pair

 = angle that stanchion makes to x-axis if mirror area element only has a single stanchion

 = thickness of mirror

 = drag coefficient of mirror arrangement

 = angle that the line from  to  makes to x-axis

 = energy per unit time available for thrust

 = position along (negative) x-axis of the sun

 = drag force per unit cross-sectional area perpendicular to the velocity vector

 = also . Additional force (in cylindrical polar coordinates) per unit mirror area (area perpendicular to x-axis) provided by stanchions,  = total force per unit mirror area (area perpendicular to x-axis) provided by stanchions in rotationally symmetric case,  = component elements in equations linking  and  with  and

 = acceleration due to gravity (assumed to be 10ms-2 at the surface of the earth)

 = effective acceleration due to thrust

 = (also) iteration increment size for mirror positioning analysis (can be positive or negative)

 = iteration step counter for mirror positioning analysis

 = mass of launcher plus propellant at time

 = rate of change of  with respect to  (is negative)

 = . If  or  then k’th point of i’th mirror in xy-plane. If  then object point of mirror pair, . If  then image point, .

 = mass of mirror

 = upper limit on propellant ejection speed (if applicable)

 = distance between  and

,  = arbitrary real numbers (positive or negative) defining the shape of the mirror layout

 = radius of larger mirror

 = density of material used to make larger mirror

 = density of atmosphere

 = , where  is the angular velocity of the mirror

  =

 = time from commencement of solar-powered propulsion

 =  = Tension per unit cross-sectional area in mirror at ,  being the tension in the transverse direction and  being the tension perpendicular to this and tangential to the mirror surface.  = uniform tension whatever the direction (tangential to mirror) if  ()

 = rate of change of  with respect to  (for mirror defined with )

 = vertically downward speed at which propellant is ejected (relative to launcher)

 = velocity of launcher plus propellant at time

 = rate of change of  with respect to

 = orbital speed (assumed to be 7800ms-1 for low earth orbit)

 = horizontal speed at which propellant is ejected (relative to launcher)

,  = distance between consecutive points in cross-sections of first and second mirrors respectively

 = cylindrical polar coordinates corresponding to Cartesian coordinates

 = a sign factor used in identification of mirror pair positioning

 


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