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Aerostat Payload Protection (APP) System



OBJECTIVE: The objective of the Aerostat Payload Protection (APP) system is to minimize Aerostat payload damage when Aerostat flight operations are terminated and the Aerostat descends back to the ground.

DESCRIPTION: Modern Aerostats carry very sophisticated and expensive Electro-Optic/Infrared cameras, RADAR, and Communications payloads. These Aerostats also possess a Flight Termination System (FTS) that quickly bring the Aerostat to the ground in the event of major events such as a fully severed tether, or deliberate user initiation.Currently, when the FTS is activated, these payloads frequently impact the ground at high velocities. The payloads are often damaged to the point that they become partially or fully Non-Mission Capable (NMC). Mission losses are approximately $ 10 million per year (approximately $ 1,000,000 of payload lost in 10 incidents per year).The typical damage modes of these payloads include:- Impacting the ground with relatively high impact velocities in a direction normal to the ground (i.e. high kinetic energy)- Impacting the ground with a relatively high deceleration rate (i.e. high “g-loading”)- Impacting the ground with a relatively high velocity parallel to the ground (i.e. “scraping”)The APP will be a feature or system on, in, or of the Aerostat, to significantly reduce the level of payload damage and incurred costs.

PHASE I: Generate an APP design concept with a technical feasibility that would lead to an eventual (at Phases 2 and 3) physical manifestation. Multiple (three) concepts are recommended to perform trade-off studies for performance, reliability, and SWAP-C comparisons of the different design concepts. Describe the CONOPS (Concept of Operations) of the design(s). Perform basic, essential Engineering studies that would demonstrate the efficacy of the design (“hand calculations”, MS-Excel worksheets, etc.). Perform simulations or computer modelling (kinematics, kinetics, FEA, CFD, etc.). The main goal of these calculations is to predict the performance of an Aerostat with an APP before it is ever built. For any computations involving actual numbers, sample data can be provided for Aerostats in the 22 to 36 meter range. Some the parameters for these computations will include:- Weight of the Aerostat (W_aerostat)- Lifting capability of Aerostat (L_aerostat)- Weight of the Payload (W_payload)- Weight addition as the result of incorporating an APP system (W_app)- Altitude of Aerostat when activating the APP (z_act)- Prevailing wind velocity at time of APP deployment (v_wind)- Distance from mooring platform (r_MP)To better illustrate the APP objective, several examples of design concepts are presented below. These are for guidance only, and not direction. Furthermore, these in no way shall limit, constrain, or otherwise drive the solution:- Controlled release of Helium to ensure that the Aerostat both touches down at a slow enough velocity but also does not migrate beyond a required distance from the Mooring Platform (i.e. “throttling” of the release valves, using on board GPS and altitude sensors, etc.)- Parachutes, including steerable versions- Inflatable cushions (aka “airbags”)And here is a sample CONOPS:“The Aerostat’s APP system, as the result of an adverse incident or by user input, is triggered. The APP automatically executes an action or sequence of actions which will bring the Aerostat from its initial operating altitude down to ground level, within a defined distance from the Mooring Platform. At the moment that the payloads hit the ground, they have either impacted the ground at a sufficiently low velocity, or have a sufficient deceleration zone so that the g-loading is low and payload damage is minimized. The payloads can be subsequently recovered with a minimum of inspection or repair, re-installed on a new Aerostat, and re-launched to altitude.”As Aerostats are exceedingly weight sensitive airborne vehicles, the total added weight from incorporating an APP shall be less than 10% of the Aerostat’s payload lifting capability. As an example, a typical 36 meter long Aerostat has a payload lifting capability of approximately 1,000 lb.

PHASE II: The Phase II effort would equip and demonstrate a functional APP system on an Aerostat with a minimum 12 m overall length.The following will be some basic functional requirements:- The APP shall be capable of activation both automatically (due to separation of the tether-to-ground connection), or manually from the ground based on user input.- The APP shall ensure that the designated payloads retain Full Mission Capability (FMC) after the APP is activated at an altitude of z_act and the payloads return to an altitude of z = 0 while prevailing winds are at a velocity from 0 to v_wind. For reference, the typical payloads would retain FMC after being subjected to MIL-STD-810 Method 516.8, Procedures IV Transit Drop, VI Bench Handling, and VIII Arrested Landing.- The payloads shall return to the ground within r_MP of the Mooring Platform, in the prevailing winds with a velocity v_wind.- Weight of any new APP components shall be less than W_APP.- The APP shall be capable of protecting payloads up to W_payload.Where mathematical symbols are presented above, the actual values that will be assigned to those symbols will be provided based on the outputs from Phase I.

PHASE III: The goal of Phase III is a fully operational Aerostat equipped with a functional APP system. A full size, 1:1 prototype of the APP shall be constructed and tested. This will be for an Aerostat of approximately 28 m to 36 m overall Aerostat length. PD Aerostats will provide the basic Aerostats, dummy payloads, and the test site for demonstrating APP trials. Values for requirements will be provided at this phase.The commercialization potential for this APP would include military and civilian Aerostats (i.e. tethered balloons and even unmanned airships).An approximate cost for estimate for the APP implementation will be an output from Phase III.

KEYWORDS: Aerostats, airships, survivability, parachutes, inflatable restraints, airbags, controlled descent, impact, shock mitigation

References:;; “Principles of Aerostatics”, John A. Taylor ISBN-13: 978-1494810535; “Technical Manual of Airship Aerodynamics”, TM 1-320, War Department, Feb. 11, 1941

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