Explicit Guidance of Ballistic Entry Using Improved Matched Asymptotic Expansions

2014

Drag-modulation flight control may provide a simple method for controlling energy during aerocapture. Several drag-modulation flight-control system options are discussed and evaluated, including single-stage jettison, two-stage jettison, and continuously variable drag-modulation systems. Performance is assessed using numeric simulation with real-time guidance and targeting algorithms. Monte Carlo simulation is used to evaluate system robustness to expected day-of-flight uncertainties. Results indicate that drag-modulation flight control is an attractive option for aerocapture systems at Mars, where low peak heat rates enable the use of lightweight inflatable drag areas. Aerocapture using drag modulation at Titan is found to require large drag areas to limit peak heat rates to nonablative thermal-protection system limits or advanced lightweight ablators. The large gravity well and high peak heat rates experienced during aerocapture at Venus make drag-modulation flight control unattractive when combined with a nonablative thermal-protection system. Significantly larger drag areas or advances in fabric-based material thermal properties are required to improve feasibility at Venus.

mentioning

confidence: 99%

Drag-Modulation Flight-Control System Options for Planetary Aerocapture

Putnam

2014

“…For example, NASA is currently investigating this technology further through the low-density supersonic decelerator program to land larger payload masses on the surface of Mars [4]. Another use of a SIAD is to provide discrete (or continuous) drag modulation as a means of landing site control [5][6][7][8]. In this case, SIAD deployment reduces the ballistic coefficient β, providing a means to directly control downrange.…”

mentioning

confidence: 99%

Investigation of Drag-Modulated Supersonic Inflatable Aerodynamic Decelerators for Sounding Rocket Payloads

Miller

Steinfeldt

2015

The goal of this investigation is to understand the sizing and performance of supersonic inflatable aerodynamic decelerators for Earth-based sounding rocket applications. The recovery system under examination is composed of a supersonic inflatable aerodynamic decelerator and a guided parafoil system to achieve sub-100 m miss distances. Three supersonic inflatable aerodynamic decelerator configurations (tension cone, attached isotensoid, and trailing isotensoid) are examined using the metrics of decelerator mass, aerodynamic performance, and vehicle integration. In terms of aerodynamic performance, the tension cone is the preferred choice for the sizes investigated. The attached isotensoid was shown to be the most mass efficient decelerator, whereas the trailing isotensoid was found to be the more ideal decelerator for vehicle integration. A three-degree-of-freedom trajectory simulation is used in conjunction with Monte Carlo uncertainty analysis to assess the landed accuracy capability of the proposed architectures. In 95% of the cases examined, the drag-modulated inflatable aerodynamic decelerator provides arrivals within the 10 km parafoil capability region, meeting the sub-100 m landed recovery goals. In 76% of the cases examined, the dragmodulated inflatable aerodynamic decelerator arrives within 5 km of this target zone. Nomenclaturenumber m = mass, kg q = dynamic pressure, N∕m 2 S = area, m 2 s = downrange, m T = reference temperature, K t = time, s u = eastward wind velocity, m∕s V = velocity, m∕s v = northward wind velocity, m∕s β = ballistic coefficient equal to m∕C D A, kg∕m 2 δDR = change in downrange, km λ = launch elevation angle, deg Subscripts D = drag deploy = deployment est = estimate f = areal max = maximum min = minimum para = parafoil ref = reference target = target

“…Rose and Hayes evaluated drag modulation as means for orbit phasing and entry targeting [6]. Kuo et al examined the use of drag modulation to track reference trajectories for ballistic missiles [7]. These studies all assumed that drag could be controlled continuously within a given interval.…”

mentioning

confidence: 99%

Precision Landing at Mars Using Discrete-Event Drag Modulation

Putnam

2014

An entry, descent, and landing architecture capable of achieving Mars Science Laboratory-class landed accuracy (within 10 km of target) while delivering a Mars Exploration Rover-class payload to the surface of Mars is presented. The architecture consists of a Mars Exploration Rover-class aeroshell with a rigid, annular drag skirt. Maximum vehicle diameter, including drag skirt, is limited to be compatible with current launch-vehicle fairings. A single dragskirt jettison event is used to control range during entry. Three-degree-of-freedom trajectory simulation is used in conjunction with Monte Carlo techniques to assess the flight performance of the proposed architecture. Results indicate that landed accuracy is competitive with preflight Mars Science Laboratory estimates, and peak heat rate and integrated heat load are significantly reduced relative to the Mars Exploration Rover entry system. Modeling parachute descent within the onboard guidance algorithm is found to remove range error bias present at touchdown; the addition of a range-based parachute deploy trigger is found to significantly improve landed accuracy. Nomenclature a = acceleration vector, m∕s 2 a axial = axial acceleration magnitude, m∕s 2 a sens = sensed acceleration magnitude, m∕s 2 C A = axial force coefficient= mass, kg P = covariance matrix r = position vector, m S ref = aerodynamic reference area, m 2 t = time, s v = inertial velocity vector, m∕s v rel = planet-relative velocity magnitude, m∕s v wind = wind-relative velocity magnitude, m∕s x = random vector x = random variable β = ballistic coefficient, kg∕m 2 η = Markov process noise ρ = atmospheric density, kg∕m 3 σ = standard deviation τ = time constant, s Δ = change in parameter