Approach and landing simulator for Space Shuttle Orbiter touchdown conditions

Abstract

This study describes a computer simulation that provides an accurate calculation of the touchdown conditions. The program is small enough to operate on a personal computer. The program simulates the Orbiter trajectory from an altitude of 10,000 ft to the Earth's surface. It assumes the Orbiter flies close to its reference altitude profile, with negligible crosswind effects. Flight data have proven both assumptions to be valid. By incorporating these assumptions with the Shuttle guidance logic, a quick approximation can be made of the touchdown speed and downrange distance to an accuracy within 400 ft of the mainframe prediction. Nomenclature= change in C D due to elevens Q?ge = change in C D due to the ground effects Q>i g = change in C D due to the landing gear C Dsb = change in C D due to the speedbrake C £>ref = CD corresponding to reference speedbrake position Q/SB = C D to speedbrake deflection ratio D = ground relative drag Z>oo = drag relative to the freestreem F = total aerodynamic force on the vehicle g = gravitational constants, =32.174ft/s 2 h = vehicle altitude h = vehicle altitude ratê sb = speedbrake control constant, = 2 deg x s/ft sbi = speedbrake integral multiplicative constant, = 0.1 deg/ft L = ground relative lift LOO = freestream lift force m = mass of the vehicle <7<x> = dynamic pressure 5 = vehicle wing area, = 2690 ft 2 SBDEF = commanded speedbrake deflection SB ref = reference speedbrake position, = 65 deg S bi = integral multiplicative factor V = ground relative velocitŷ eas = equivalent airspeed error = equivalent airspeed error, = F eas -490 KOO = freestream Orbiter velocity at altitude V = ground relative deceleration K 2 = updated ground relative velocity V w = velocity of the wind j8 = constant for air density calculation F = landing gear deployment angle 7 = ground relative flight-path angle 7 = ground relative flight-path angle rate 700 = freestream flight-path angle AS = vehicle displacement At = time step 0 = vehicle pitch angle p a = air density of the freestream at altitude P 0 = air density at sea level for 62 standard atmosphere $ = angle between the relative drag and the total aerodynamic force on the vehicle

Launch Vehicle Guidance for Low Energy Re-entry

“…The Space Shuttle A&L guidance scheme uses a reference altitude profile that consists of an initial steep glideslope, followed by a pull-up maneuver to a shallow glideslope [8,9] . This two-phase flight path approach has been proven to be effective for unpowered vehicles (like the Shuttle) with relatively low lift-to-drag ratios (L/D).…”