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... for the stratosphere drops this rule of thumb does not appear to hold true due to low air density. For simplicity, a third order polynomial is fit to standard atmospheric density data ( Figure 1). Using this data in conjunction with Eq. 1, the mass ratio for each of the three flight configurations can be estimated for an entire mission. ...
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... the air density polynomial fit (Figure 1), the horizontal and vertical velocity components can be readily estimated for a range of altitudes as shown in Figure 10. For this estimate the glide slope was set to two as this is the current estimated glide slope for the Snowflake system at low altitudes. ...
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... the air density polynomial fit (Figure 1), the horizontal and vertical velocity components can be readily estimated for a range of altitudes as shown in Figure 10. For this estimate the glide slope was set to two as this is the current estimated glide slope for the Snowflake system at low altitudes. ...
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... the simple control system is not successful in this best case scenario (non-changing The control system attempts to control the heading, therefore, the horizontal component of the parafoil velocity (in no wind) must be significantly larger than the atmospheric wind to accurately steer the vehicle. The horizontal velocity component is compared with wind data collected from a previous balloon launch in northern Nevada in Figure 11. A ratio of atmospheric wind speed to parafoil horizontal speed is used to assist in analyzing the results. ...
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... ascent each canopy remained semi-inflated; due to the semi-rigid support structure on top of the canopy. As seen in Figure 12, the small canopy successfully inflates immediately after burst. For each of the three flight tests, soon after inflation the payload began to rotate relative to the canopy. ...
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... each of the three flight tests, soon after inflation the payload began to rotate relative to the canopy. Figure 13 shows the collected rotation rates after release for one of the three flight tests. Within the first minute of descent, the payload spin rate increases drastically. ...
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... with the video confirms that there was significant relative rotation between the payload and the canopy. Initially, the leftover balloon shards were thought to cause the problem (as can be seen in Figure 12); however, the latest experiment was performed with the use of a cutdown system (rather than ascending to balloon burst). The most recent drop test yielded the same catastrophic results, with a completely tangled/twisted canopy soon after release. ...
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... twisted, the canopy acts essentially as a very short streamer. As the payload and canopy approach the same drag force, a flat very high rotation rate induced a quite large centripetal acceleration (Figure 15). The large quasi-static centripetal acceleration has a tremendous effect on the calculated orientation angles as shown in Figure 16. ...
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... the payload and canopy approach the same drag force, a flat very high rotation rate induced a quite large centripetal acceleration (Figure 15). The large quasi-static centripetal acceleration has a tremendous effect on the calculated orientation angles as shown in Figure 16. The rotation rates measurements show a very large rotation in all axes for most of the flight; however, the pitch and roll axes oscillate around ∼ 70 • and −50 • , respectively. ...
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... order to successfully stabilize the canopy, software checks must be developed to counteract the influence of centripetal acceleration. Figure 15: Spin rate and total acceleration measured during descent for the small parafoil system. ...
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... greatly improves consistency during inflation. The semi-open canopy shape can be seen during balloon burst in Figure 17. For the single quantitative flight, the control lines were tangled around the video camera during the entire descent. ...
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... the single quantitative flight, the control lines were tangled around the video camera during the entire descent. This can be seen in Figure 18 with the two lines converging towards the camera lens. Both left and right control lines were tangled, causing a symmetric brake deflection. ...
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... controllability was reduced, the vehicle was still able to impose some brake deflection on the canopy. The collected total acceleration and yaw rate data are shown in Figure 19. From a first inspection of the spin rate data, it could be mistakenly postulated that the spin rate is higher at high altitude, and lower and low altitude; however, upon further inspection of the data, the decrease in the spin rate correlates very well with the sudden increase in total acceleration. ...
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... the twisting motion was damped, the canopy quickly entered into a near flat spin ( Figure 21). The timing of the transition from twisting to flat spin match up very closely with the increase in total acceleration. ...
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... prior to the increase in acceleration, the spin rate quickly dampens out, corresponding well with the flight video data. The spin rate data shows a moderate, quasi-static (∼ 150 deg/s) spin rate immediately after the increase in total acceleration (Figure 19). Therefore, the additional acceleration is likely a centripetal acceleration component caused from the quasi-static angular velocity. ...
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Citations
... Several ram-air parafoil-based self-guided aerial delivery systems have been developed over the past 20 years, seeking to provide a low-cost, minimally complex, and accurate precision delivery system [2]. The usage of such a system for the final descent phase of an ISS sample return mission has been investigated; however, the safe and reliable deployment and control poses serious challenges [1,3,4]. ...
The concept of using an autonomous HAHO (high altitude, high-opening) parafoil-based system as a solution to the final descent phase of an on-demand International Space Station (ISS) sample return concept was tailored to meet specific constraints defined by the NASA Ames Research Center SPQR (Small Payload Quick-Return) study. Difficulties in consistently and safely deploying ram-air parafoils at high altitudes needs to be suitably addressed prior to utilization in space sample return applications. This paper presents an alternative to the ram-air parachute SPQR concept. Specifically, the feasibility of using a cruciform-type canopy design modified to enable a limited steering capability, similar to what has been accomplished with the traditional round canopy-based Affordable Guided Aerial Delivery System (AGAS). In contrast to the AGAS system the cruciform canopy approach requires only a single actuator, providing a wider range of possible control actions and therefore a more robust guidance technique. Preliminary design and flight test results are provided from initial low-altitude testing of the cruciform canopy-based SPQR-compatible system.
