Supersonic and Transonic Deployment of Ribbon Parachutes at Low Altitudes

Abstract

Results are presented for twenty-nine flight tests of a 22.2-ft (6.8-m) diameter ribbon parachute (reefed for 0.5 sec) with a nominal 2000-lb (907-kg) store. The design, fabrication, and packing of the parachute system are discussed. Low altitude drop tests were made with F-4 and A-4 aircraft at Mach numbers from 0.57 to 1.22, and rocket-boosted tests were made at Mach numbers from 1.62 to 1.70, the latter corresponding to a maximum dynamic pressure of 2720 psf (130 kN/m 2 ). The maximum measured snatch load, reefed stage opening shock, and second stage opening shock were approximately 65 klb (289 kN), 165 klb (734 kN) and 150 klb (667 kN), respectively. The measured load data and sequence of parachute function times are relatively consistent and repeatable. There is no discernible effect of Mach number on the steady-state drag area of the reefed parachute at Mach numbers from 0.7 to 1.50. NomenclatureA t ,'A e = effective canopy inlet and exit areas, respectively, during inflation process C D -drag coefficient based on S c C D S -.= drag area, full open D c = constructed diameter (base of conical ribbon parachute or diameter of reefing line circle) DO = nominal parachute diameter D E = effective reefed parachute diameter g = acceleration L = distance travelled during opening L R -length of reefing line M = Mach number Q = dynamic pressure S c = base area of parachute or area of reefing line circle t = time from tail can ejection A*/ = filling time of nonreefed parachute Afip = time to first peak load, t ip -t L s, or approximate first stage filling time A* 2/ = filling time from disreefing until full open (from optical data) Af 2p = time to second peak load, t 2 p -t DR Ar R = reefing line cutter time delay, t DR -tLs V = vehicle velocity V c = volume of canopy A G = geometric porosity of canopy p c = density inside canopy at full inflation p^. = freestream static density Subs^mpts 0 = conditions at tail can eject 1 = reefed conditions 2 = conditions after disreefing

Analysis of Deployment and Inflation of Large Ribbon Parachutes

“…(2) and (3) and by using the appropriate mass and mass flux equations(m f + p I l 0 )x f = (m f + p t l 0 )g siny --~-(C D S) f x f 2 -T (4) (m* ~ Pi I 0 )x b= fab-Pi I 0 )g siny --y-feS)^2 4-T -P l i 0 (x f -x b }(5)Tension is obtained by solving for strain in the lines and by obtaining the load [(P(e)] from the load-strain diagram of the suspension line material. Tension is then…”

“…= apparent mass coefficient Co = drag coefficient based on inflated diameter CR = radial force coefficient D = drag, Ib e c = ratio of minor axis to major axis for canopy equals 0.6 constant F = force, Ib g -acceleration of gravity, fps 2 LI = arc length along inflated portion of canopy, ft L u = arc length along uninflated portion of canopy, ft / = suspension line length, ft m -mass, slug ra' = apparent mass, slug M = total mass, slug N = number of suspension lines q = dynamic pressure, lb/ft 2 …”