Low Cost HALO Cargo Airdrop Systems

Transcription

1 2th AIAA Aerodynamic Decelerator Systems Technology Conference and Seminar<BR> 4-7 May 29, Seattle, Washington AIAA Low Cost HALO Cargo Airdrop Systems James Sadeck 1, Justin Riley 2, Kenneth J. Desabrais 3, and Calvin Lee 4 US Army Natick Soldier Research, Development, and Engineering Center, Natick, MA, 176 A low cost high-altitude and low-opening (HALO) cargo airdrop system was developed to airdrop 2,5-1, lb payloads with an objective of providing precision airdrop capabilities. The system consists of the Army standard Low Cost Low Velocity parachutes and Low Cost Container that have been used in humanitarian and other Army airdrop applications. The system was successfully designed, developed and full-scale tested. Performance tests were first conducted to generate Calculated Aircraft Release Point (CARP) data to examine the basic system performance characteristics. Operation Utility Evaluation (OUE) tests were then performed using the CARP data to determine system airdrop accuracy. The mean value of 32 OUE tests was found to be 662 ft (22 m) with an uncertainty of 51 ft (16 m). D ab D bc D cd D bd h c V c V d V windbc V windcd Nomenclature = ground distance from load release to system first vertical = ground distance from first vertical to main parachute deployment = ground distance from main parachute deployment to ground impact = ground distance from first vertical to ground impact = altitude of system at main parachute deployment = system descent velocity at main parachute deployment = system descent velocity at ground impact = range of wind speed from first vertical to main parachute deployment = range of wind speed from main parachute deployment to ground impact I. Introduction urrent research and development of military parachutes and airdrop systems are focused on lowering the threats C to delivery aircraft and ground soldiers, and the costs of one-time use systems for operations in remote areas and for humanitarian relief missions. These requirements are being addressed through the development of precision airdrop systems using guided parafoils deployed from high altitudes over 25, ft above ground level (AGL). Due to the expensive guidance, navigation and control (GNC) systems and the associated computer hardware and software, guided parafoil airdrop systems are costly. They currently cost $6-$4 per pound of payload delivered. Lower cost parachute systems are currently considered for ballistic (non-guided without GNC systems) precision airdrop systems from high altitudes. The Air Force (AF) has been supporting a program to develop a family of Improved Container Delivery Systems 1 (ICDS) ballistic cargo airdrop program in conjunction with the Joint Improvised Explosive Devise Defeat Organization (JIEDDO). The goal of the program is to develop low cost 2,5-1, lb ballistic high altitude airdrop systems. As part of the program, we have developed a low cost system using the Low Cost Cargo Parachutes 2 (LC CP). The other part of the program utilizing the Army G12 and G11 cargo parachutes is being reported in Reference 1. Our low cost ballistic airdrop system is based on the High Altitude Low Opening (HALO) concept. The LC HALO system that we have developed and tested used all Army standard parachutes and equipment, including the 15 ft and 28 ft ring-slot parachute as the drogue parachute, the Low Cost Low Velocity (LC LV) cargo parachute as 1 Senior Research Mechanical Engineer, Airdrop Technology Team, 15 Kansas Street/ RDNS-WPA-T. 2 Research Aerospace Engineer, Airdrop Technology Team, 15 Kansas Street/ RDNS-WPA-T. 3 Research Aerospace Engineer, Airdrop Technology Team, Airdrop Technology Team, 15 Kansas Street/ RDNS- WPA-T, Senior AIAA member. 4 Research Aerospace Engineer, Airdrop Technology Team, Airdrop Technology Team, 15 Kansas Street/ RDNS- WPA-T. 1 This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

2 the main recovery parachutes and the Low Cost Container (LCC) as containers for the load. A modular rigging method was developed to provide payload capacities from 2,5 lbs to 1, lbs. A single module consisted of a 2,5 lbs load and one LC LV parachute and four modules were rigged together for a 1, lb payload. The cost for these LC HALO systems is estimated to be only $2 per pound of payload delivered. The LC HALO systems were successfully developed and full-scale tested from Army cargo aircraft C-13 at Yuma Proving Ground (YPG). Some full-scale field testing (Operation Utility Evaluation) of the system has been conducted and is currently ongoing at YPG. II. System Description and Operation For ballistic precision airdrop from high altitudes, the parachute/payload system has to descend at high speeds toward the ground target to penetrate the wind so that the descent trajectory will be as vertical as possible. At an appropriate altitude close to the ground, the main parachute will then be deployed to minimize dispersion. As mentioned earlier, a 15 ft or 28 ft ring slot parachute is used as the drogue parachute and the LC LV parachute is used as the main recovery parachute. In the last few years, NSRDEC has successfully demonstrated the capability and utility of the 2,2 lb LC LV cargo parachute (similar performance as the G12 parachute) made of polypropylene woven fabric. The Low Cost Container (LCC) made of polypropylene webbing has also been demonstrated. The payloads for high altitude ICDS deployments are rigged in a similar fashion as a standard cargo delivery system (CDS) except that the LCC is utilized. Multiple LCC containers are employed for payloads larger than 2,5 lbs. When the ICDS is deployed from the aircraft at high altitudes, the standard 15 ft or 28 ft ring-slot extraction parachute (depending on payload weight) is deployed and opened (using a static line) immediately upon exit from the aircraft. This drogue canopy stabilizes and turns the payload vertical. The forces from the drogue parachute are transferred to the payload through the drogue bridle, the cutter loop, and the LCC container. The ICDS system remains under drogue falling at a high velocity until it reaches the deployment altitude for the LC LV main recovery parachutes. At this deployment altitude, the cutter loop is activated, releasing the drogue which pulls on the chute deployment bridle lifting the main recovery parachutes off the payload while stripping the deployment bags off the LC LV parachutes. Deployment of the LC LV main recovery canopies begins and decelerates the payload to the final velocity. The schematic in Fig. 1 depicts a 2,5 lb system with the drogue parachute deployed. The drogue drag forces are transferred through the bridle and cutter loop to the LCC. At a predetermined time, a timer unit activates a - second pyrotechnic cutter which releases the cutter loop. As the payload and drogue separate, the chute deployment bridle becomes taut and receives the drogue force, which pulls on two guillotine knives, cutting Type VIII webbing used to secure the LC LV canopy to the payload. The chute deployment bridle then deploys the main recovery parachute. At line stretch, each line group of the LC LV canopy is secured to one of the four sides of the LCC using a ¾ tubular nylon attachment yoke. It should be noted that the LC LV canopy needs to be repacked from the standard canopy-first deployment bag into a custom lines-first deployment bag. The new deployment bag has a similar design as the standard G11 or G12 deployment bag except it is made from polypropylene fabric and was designed to allow for easy transfer from the standard LC LV bag. The larger weight systems function similarly to the single module system with the exception of the addition of sling extensions thereby raising the confluence point and the use of additional LC LV canopies to achieve lower final descent rates. Figure 2 depicts a 5, lb double system with the drogue parachute deployed and two LC LV main recovery parachutes secured to the top of the payload. The 7,5 lb triple system and the 1, lb quadruple system are rigged in a similar fashion with the systems having three and four LC LV parachutes respectively. Images of rigged 7,5 lb and 1, lb loads are shown in Figs 3 & 4. Sling extensions are used to form a confluence point at the cutter loop, due to the increased size of the payload. When the timer unit and cutter are activated, the sling extensions fall to the side as the chute deployment bridle deploys the LC LV canopies. During this deployment, a new Low-V confluence point is formed by a second set of suspension slings attached to a confluence adapter loop. The confluence adapter loop contains risers to each of the LC LV canopies. For a 2,51-5, lb system weight range, two LC LV canopies are used, with an additional canopy for each subsequent 2,5 lb weight range. Images of the operational sequence of the 2,5 lb system are shown in Fig. 5. The first image shows the payload falling under the drogue parachute. When the drogue release cutter activates, the packed LC LV parachute is lifted off the payload and the suspension lines pulled out of the deployment bag (second and third image in Fig. 5). The drogue parachute pulls off the deployment bag and the LC LV parachute inflates, decelerating the system to its final descent velocity. In the final design of the system, the drogue parachute is completely released from the payload but during initial developmental testing it was shown that the drogue 2

3 parachute could be retained with the payload thereby leaving no parachutes in the air if this feature is desired. Similarly the deployment sequence of the quadruple system is shown in Fig. 6a. In this sequence, once the drogue is released, it lifts all four packed LC LV parachutes from the payload. It then deploys a cluster of LC LV parachutes. The Low-V confluence point can be seen in the images of Fig. 6a. Fig. 6b shows a cluster of four LC LV on a quadruple system just prior to landing. Initial developmental testing was performed in Kingman, AZ and successfully demonstrated the HALO concept described above. The concept was scaled from 2,5 lbs to 1, lbs in 2,5 lb increments in testing at Kingman and YPG to ensure all JIEDDO system goals were achieved. After initial developmental testing returned an accurate drag area for the system while under drogue, a timing calculator was developed to aid in determining the correct time to activate the -second pyrotechnic cutter at 1,5 ft AGL. The error in the calculations proved to be minimal during full-scale testing. III. Full-Scale Tests, Results and Discussion For a high altitude ballistic airdrop system, its performance characteristics, including the opening time, rate of descent and its ballistic trajectory as influenced by the wind, are needed by the Air Force to determine the Calculated Aircraft Release Point 3 (CARP). These CARP data will allow the aircraft to release the load at an appropriate location to account for the wind effect in the delivery of a load to the target on the ground. Since it is the first time LC LV cargo parachutes are being used in a HALO application, a series of LC LV HALO tests were conducted to examine their performance characteristics and obtain CARP data. Several preliminary tests were conducted first using Army cargo aircraft C-13 at YPG to improve system reliability and repeatability. Five successful full-scale performance tests from high altitudes were then conducted. Results from these tests were fed back to the CARP computer software to generate CARP data for the operational field testing. The CARP data is described in Reference 1. Drop conditions for the five performance tests are shown in Table 1. A typical operation sequence of a quadruple module (four LC LV parachutes) of 1, lb system is shown in Fig. 6. In these tests, detailed system position and velocity were measured using four Kineto Tracking Mount (KTM) cameras and wind velocity was measured using a YPG provided wind pack. The wind measurements were then used to correct the position and velocity measurements of the system 1. Details of the instrumentation used and wind correction methodology are presented in Reference 1. The wind corrected data are presented in this paper for the five performance tests. Important position and velocity data showing the basic characteristics and performance of this HALO cargo system are shown in Figs 7-9. In all these figures, data are presented from the time when the load was extracted by the drogue parachute to the time when the load impacts the ground. The x-direction is the forward vector of the aircraft, y-direction is perpendicular to the x-direction in the right direction facing forward of the aircraft and z-direction is perpendicular to the xy-plane toward the ground. Test# Table 1. Drop configurations of the five performance tests. suspended weight (lbs) total weight (lbs) drop altitude AGL (ft) 3 # of main parachutes drogue parachute 1 (9-13) 7, 7,65 17, ft. RS 2 (9-78) 7, 7,7 17, ft. RS 3 (8-668) 7,5 8,15 17, ft. RS 4 (8-678) 7,5 8,25 17, ft. RS 5 (9-14) 9,3 9,9 17, ft. RS Figure 7 shows the system velocity versus altitude (above Mean Sea Level) of the five tests. The four important events of the system trajectory are load release from the aircraft, first vertical of the drogue parachute, deployment of the LC LV parachutes and ground impact. These events are indicated in Fig. 7a and designated as a, b, c and d on the Altitude scale (these same symbols are also used in Figs. 8 and 9 as shown later). As expected, after the initial nearly horizontal deployment and inflation of the drogue parachute, the system descends almost vertically at high speeds for over 1, ft under the drogue parachute. At the end of this descent, the main LC LV parachutes then open and decelerate the load to a steady low-speed descent until it impacts the ground. Relevant system velocities and the range of wind velocities are tabulated in Table 2. It is seen that the ground impact velocities are within the safe cargo landing velocity of 28 ft/sec.

4 Table 2. System velocity data of the five performance tests. Test# h c AGL (ft) V c (ft/s) V d (ft/s) 4 V windbc (ft/s) V windcd (ft/s) 1 (9-13) 1, (9-78) 1, (8-668) 1, (8-678) 1, (9-14) 2, The system drift shown as projected ground distance travelled by the system (related to drop accuracy) is visually shown in Figs. 8 and 9. The spatial locations of the four important events a, b, c and d as described earlier are indicated in Fig. 8a, and their ground projections are shown in Fig. 9, using the data from Test 1. The projected ground distance between each point is D, e.g., D bc is the distance between b and c. The D values, their mean values, and standard deviations of the mean for the five tests are tabulated in Table 3. It is seen that it took ~2, ft mainly in the x-direction for the drogue to become fully inflated when the first system vertical position was reached. This distance is quite consistent for the five tests and was conveniently programmed into the CARP for the aircraft to allow for this offset distance for load delivery. The drift of the system, D bc, from its first vertical to main parachutes opening was mostly less than 5 ft. This drift is mainly caused by the flat bottom surface of the load. Considering the high drop altitude of ~17, ft, the drift was only 3% of the drop altitude. This drift was quite random in direction in the five tests as shown in Fig. 9. For the LC LV main parachutes, although they were deployed from ~2, ft, their drift, D cd, was generally higher than those of D bc. Due to the randomness of these two drift components, the total drift of the system, D bd, from its first vertical to ground impact was within 9 ft and its mean value was 627 ft. For a HALO ballistic precision airdrop system, if the CARP allows for the offset distance, D ab, the total drift D bd is the overall system accuracy and the inherent properties of the LC HALO ballistic cargo airdrop system. As shown later in the field testing of the system, this was indeed demonstrated. The drift during the highvelocity descent (under the drogue) can be decreased by designing and dropping with a more streamlined load to lower its drag force and increase its descent velocities as compared to those of the current system with a flat bottomsurface load. The drift during the low-velocity descent (under the LC LV main parachutes) can be decreased by deploying the LC LV parachutes closer to the ground. However, one should note that D bd is the vectorial summation of D bc and D cd (see Figs 8 and 9). The mean of D bc is less (or equal to at the most) than the summation of the means of D bc and D cd as shown in Table 3. Table 3. System ground traverse data of the five performance tests. Test# D ab (ft) D bc (ft) D cd (ft) D bd (ft) 1 (9-13) 1, (9-78) 1, (8-668) 1, (8-678) 1, (9-14) 2, mean = 1, sdom = As mentioned earlier, test data from the five performance tests described above was programmed into the CARP software for the Air Force. The updated CARP data for the LC HALO system was then used to conduct the field Operational Utility Evaluation (OUE) testing at YPG. A total of 32 OUE tests were conducted from altitudes < 17,5 ft AGL using a C-13 aircraft. System positions and velocities were not measured in these tests and only drop accuracy of these tests was measured. Drop accuracy of the system with a cluster of three LC LV parachutes and for the system with a cluster of four is shown in Fig. 1. In this figure, the origin is the target for the delivery. One can see that practically all the drops fall within a circle of 9 ft and some are quite close to the target. The mean of the miss distances is 662 ft and is also shown in Fig. 1.

5 As mentioned earlier, the OUE drops were conducted with the CARP input for the aircraft to release the load at an optimum position, taking into account the effect of wind and the offset distance of the drogue parachute in order to increase drop accuracy. If that was the test condition, the ground target of the OUE tests or the origin of Fig. 1 could be treated as point b in Fig. 9, and point b could be treated as the ground target of the five performance tests. If the CARP data was satisfactory, one would expect the miss distances in Fig. 1 and the D bd (the total inherent property (drift) of the system as shown earlier) to be comparable. Values in Table 3, and their mean values show they are similar. This was indeed the case as shown in Table 4 that the mean of the OUE tests was 662 ft and the mean of the performance tests was 627 ft. The CARP data proved reliable and the aircraft released the loads at optimum locations for the OUE tests, reinforcing the projected maximum performance of 6 ft as the accuracy of this system. This also indicates that system accuracy can be determined from performance tests alone, decreasing the number of OUE tests required, thereby saving additional testing costs. Table 4. System miss distance from intended impact point. Test Number of Drops Mean miss distance (ft/m) Uncertainty (ft/m) OUE / / 16 Performance / / 32 IV. Summary A HALO cargo airdrop system using the Low Cost parachutes has been successfully designed, constructed, and full-scale tested. Payload weights from 2,5 to 1, lbs were airdropped from 17,5 ft AGL using a single to a cluster of four Low Cost Low Velocity parachutes and landed safely. Drop accuracy in Operation Utilities Evaluation tests was generally within a circle of 3 m or 98 ft using reliable CARP data. The mean of the miss distances was 662 ft. Examination of the inherent properties of the system shows that drop accuracy could be further improved by streamlining the geometry of the load and minimizing the drift while descending under the main parchutes. It is suggested that system performance characteristics (position and velocity) during OUE testing should be investigated in the future to correlate with the inherent system properties during performance testing, and further develop guidelines and methods to improve the accuracy of HALO precision airdrop systems for cargos. Acknowledgments The authors would like to thank the Joint Improvised Explosive Device Defeat Organization for their support for this work. The airdrop testing support provided by the US Army Natick Soldier Research Development & Engineering Center, US Army Yuma Proving Ground and the US Force Air Mobility Command is acknowledged. Finally, the system analysis and modeling conducted by Professor J. Potvin of St. Louis University is also acknowledged. References 1 Henry, M., Lafond, K., Noetscher, G., Patel, S. and Pinnell, G., Development of a 2,-1, lbs Improved Container Delivery System, Proceedings of 2 th AIAA Aerodynamic Decelerator Systems Conference and Seminar, Seattle, Washington, May 29, AIAA Paper Bonaceto, B. and Stalker, P., Design and Development of a New Cargo Parachute and Container Delivery System, Proceedings of 18 th AIAA Aerodynamics Decelerator Systems Conference and Seminar, Munich, Germany, May 25, AIAA Paper Computed Air Release Point Procedure, Air Force Instruction , 1 July 1998, publication available on the SAF/AAD website, 5

6 Figure 1. Design schematic of a single module of a 2,5 lb system. Figure 2. Design schematic of a double module of a 5, lb system. 6

7 Figure 3. Picture of a rigged triple module of a 7,5 lb system. Figure 4. Picture of a rigged quadruple module of a 1, lb system. 7

8 Figure 5. Operation sequence of a single module 2,5 lb system during developmental testing 8

9 a) b) Figure 6. a) Operation sequence of a quadruple module of a 1, lb system; b) image showing a quadruple module just prior to landing. 9

10 Test #1 (9-13) 2 18 load release a altitude MSL (1 3 ft/s) first vertical x-velocity y-velocity z-velocity total velocity b a) 4 main parachute deployment c 2 ground impact d velocity (ft/s) Test #2 (9-78) first vertical altitude MSL (1 3 ft/s) x-velocity y-velocity z-velocity total velocity 4 2 main parachute deployment b) velocity (ft/s) Figure 7. System velocity measurements of the five performance tests. 1

11 2 Test #3 (8-668) first vertical altitude MSL (1 3 ft/s) x-velocity y-velocity z-velocity total velocity 4 2 main parachute deployment c) velocity (ft/s) Test #4 (8-678) first vertical altitude MSL (1 3 ft/s) x-velocity y-velocity z-velocity total velocity 4 2 main parachute deployment d) velocity (ft/s) Figure 7. (continued.) 11

12 2 Test #5 (9-14) altitude MSL (1 3 ft/s) first vertical x-velocity y-velocity z-velocity total velocity 4 2 main parachute deployment e) velocity (ft/s) Figure 7. (continued) 12

13 2 altitude (ft MSL) 15 b 1 a 5 1 c d system trajectory a: load release b: first vertical c: main parachute deployment d: impact point y x a) projected system trajectory a: load release b: first vertical c: main parachute deployment d: impact point x b d c 5 a b) Figure 8: a) Three-dimensional trajectory of a triple module system in performance test #1 (note different horizontal and vertical scales); b) projected ground distances travelled in performance test #1. The aircraft flight direction at load release is denoted in the x-direction with the y-direction being orthogonal to it. 13 y

14 3 Test #1 (9-13) 3 Test #2 (9-78) a) b) Test #3 (8-668) Test #4 (8-678) c) d) Test #5 (9-14) e) Figure 9. Projected ground distances travelled of the five performance tests (see Fig. 8 for legend). 14

15 ft xLV LCADS 4xLV LCADS mean distance 27 Figure 1. Impact locations for drops conducted under the OUE tests with the mean miss distance also shown. 15