SITT_DESIGN_CONCEPT_-_INDUSTRY_DAY.docx

Specification for a Minuteman III SI Test Tower (SITT)

PRELIMINARY DESIGN CONCEPT

FOR A

MINUTEMAN III SHOCK ISOLATOR TEST TOWER (SITT)

UNITED STATES AIR FORCE

HILL AIR FORCE BASE

· PRELIMINARY -

· CONCEPTUAL ONLY -

FEBUARY 2016

1. GENERAL

1.1. The following work represents ideas relating to the potential design of a replacement Shock Isolation Test Tower (SITT) to be used in testing Shock Isolator (SI). The following SIs would be tested on the SITT: Missile Suspension System (MSS), Launch Equipment Room (LER) and Launch Control Center (LCC).

NOTE: This is a conceptual design only. It is provided only to stimulate ideas for an improved SITT design, with respect to the existing SITT located at Building 1913 at Hill Air Force Base, Clearfield, Utah. Any contractor who chooses to use any, or all, of this conceptual design shall be fully responsible for the integrity of the design they choose to propose and/or develop.

2. CONCEPTUAL DESIGN

2.1. Following is a list and description of system components that are part of the design concept.

· Tower Structure – The tower structure shall be anchored to a Foundation. It shall provide the structural mounting surfaces for the ULP and LLP linear actuators, the support structure for the LLP in its lowered position, and possibly the support structure for weight slug positioning guides. The tower and its foundation shall together be designed for the worst case static and dynamic loads imposed during the SI tests and for Seismic Zone 3 conditions. The working space inside the structure shall be adequate for operators to perform their needed functions when conducting SI tests.

· Upper Lift Plate (ULP) – The top side of this plate shall be connected to the lower end(s) of the ULP linear actuator(s). The bottom side shall be designed to connect to both the load cell and the drop link. The plate shall transfer the static and dynamic loads from the load cell (used in the MSS and LER tests) and the 2-inch drop link (used in the LCC tests) to the ULP linear actuator(s). – Note: An option to a round plate would be a larger square plate that would be lifted at its corners by 4 linear actuators instead of 1. This may provide greater stability.

· Lower Lift Platform (LLP) – The top side of this platform shall be connected to the lower ends of the 4 LLP linear actuators. The bottom side shall be connected to the top side of an electro magnet. The platform has two purposes. First, it shall transfer the static and dynamic loads from the electro-magnet to the LLP Linear Actuators. Second, it shall provide a working floor surface for the carts that roll SIs into the SITT and for operators to walk on. In its down position, the top of the platform shall be level with the floor. The platform shall have a 26 inch diameter hole through its center to allow SIs to pass through it during drop tests.

· ULP Linear Actuator(s) – Use 1 or 4 of these. The actuator base is supported by the upper tower structure. The actuator is connected to the top of the ULP and has multiple functions. First, it provides the force to extend SI pistons during tests. Second, it holds SI pistons in fixed positions during drop tests. In this function it also carries the weight and dynamic deceleration loads of the SI cylinder/body and the attached weight slug. Third, it is used to lift and lower SIs into needed positions. – Note: It may be possible to perform the required functions with one actuator. However, four actuators (one at each corner of a square ULP) may be required to stabilize the dynamic loading on the ULP during drop tests.

· LLP Linear Actuators – The actuator bases are supported by horizontal cross beams on the lower part of the tower structure. The actuators are connected to the LLP. Their purpose is to raise the LLP, magnet and weight slug into position for each drop test. Following the test, they lower the LLP and magnet to their normal position.

Note for ULP & LLP Linear Actuators: All linear actuators shall be electric driven and shall have positioning control. Stroke lengths and lift capacities shall be determined as part of the design. This design concept is uses jack screws for this purpose.

· Electro Magnet – This magnet, when energized, shall generate sufficient magnetic force to lift the combined 41,000 pound weight slug. It shall be flat on top and bottom and shall have a 26 inch diameter hole through its center to allow SIs to pass through it during drop tests. It shall be designed to permanently connect to the bottom of the LLP. The magnet shall have an electrical power source and controls that will allow it to attach to the UWS for lifting the weight slug(s) and detach from them so they can instantly drop to complete the drop tests. (Reference Note: This concept was discussed with electro-magnet manufacturer: Walker National, Inc., Columbus, Ohio)

· Load Cell and Connecting Links – The purpose of the load cell is to provide continuous feedback to the DAS of the force being applied to MSS and LER pistons during spring rate and damping testing. The load cell shall be connected to the bottom side of the ULP and to the SI piston eyelets via removable connecting links. The links shall provide flexibility above and below the load cell to prevent side or torque loading. The load cell shall have a minimum 100,000 pound load rating and a +/- .05% accuracy. Two identical load cells shall be provided with the TTS to provide backup during calibration downtime. The load cells shall have load rating safety factors of 1.5 and 3.0, based on yield and ultimate respectively.

· LCC 2-Inch Drop Link – The drop link has two functions. First, it connects the SI piston to the ULP. Second, it provides for 2 inches of unrestricted free fall of the LCC SI and UWS at the beginning of the LCC drop test. The link shall be designed to withstand all of the static and dynamic loads imposed during the LCC tests.

· 41,000 Weight Slug – This weight slug is formed by connecting the UWS and LWS together. It has two functions. First, it holds the MSS and LER cylinders in fixed positions while the SI pistons are being extended during spring rate tests. Second, it provides the needed drop weight for the MSS damping test. The height of this slug shall be at least as great as its maximum horizontal dimension to provide for stability during drop tests.

· Upper Weight Slug (UWS) – The total weight of this slug shall be 19,000 pounds. The top-center portion of this slug shall be cylindrical and extend up through the center hole in the electro-magnet and the LLP. SI SI-UWS adapters shall connect to the top of this cylindrical extension. The UWS shall have a 6 inch diameter vertical hole through its center. This will accommodate the retracted MSS and LER pistons when these SIs are mounted to their SI-UWS adapters. The top side of the non-cylindrical portion shall mate up to the bottom side of the electro-magnet and shall be of adequate size and finish so as to provide for needed magnetic connection forces. The bottom side of the UWS shall be configured to mate to the top side of the LWS. A method shall be provided to easily attach and detach the UWS to and from the LWS.

· Lower Weight Slug (LWS) – The total weight of this slug shall be 22,000 pounds. The top side shall be configured to mate to the bottom side of the UWS. Depending on the height of the UWS, this slug may also require a vertical hole to accommodate SI pistons.

Weight Slug Note: An alternate configuration for the weight slugs is to have the UWS mount inside the LWS with vertical mating surfaces.

· SI-UWS Adapters – The function of these adapters is to connect the MSS and LER cylinders and the LCC mounting flanges to the top of the cylindrical portion of the UWS. The design of each adapter and its connection points shall be tailored to the configuration of its SI and shall be rated for the greatest loads imposed during applicable tests. The adapters shall be easily disconnected.

· Weight Slug Guide System – A guide system, which will keep the weight slugs aligned with the tower centerline while they are being raised and dropped, shall be provided. The guide system shall not interfere with the free fall of the slugs.

· LWS Bottom Support – A physical support structure shall be provided for the LWS to rest upon when in it in its lowered position.

· Piston Displacement (D) Potentiometer – The purpose of this device is to provide continuous D feedback to the DAS. Special adapters that mount the potentiometer to each SI cylinder or body and piston eyelet shall be provided.

· Tower Foundation – The tower foundation shall be constructed of reinforced concrete. It shall be designed to support the tower under worst case static and dynamic testing and Zone 3 seismic conditions. Provisions shall be provided for anchoring the tower to the foundation and also leveling the tower. The foundation shall be installed in an existing building at HAFB. Installation shall include site excavation, which will require saw cutting and removal of the existing concrete floor. Because the top of the foundation shall be below floor level, reinforced concrete walls shall close in the space between the top of the foundation and the floor. Over excavated floor that is removed to accommodate the foundation installation shall be replaced. Workspace inside the walls shall be adequate to provide needed work space around the base of the tower.

· Deck Plate – Floor level deck plate and a support structure shall be installed to cover the open pit area between the pit walls and the LLP. The deck plate shall be designed to support personnel traffic and also the SI carts that will be used to load and unload SIs in the tower. Portions of the plate shall be removable to allow access as needed below floor level.

· System Controls – The SITT functions and each specific test shall be controlled by a Programmable Logic Controller (PLC). The operator interface for the PLC shall be a desktop computer with visual human-machine interface software. This interface shall provide the operator with a pictorial representation of the tower, each of its functioning components and the SI that is installed at any given time. Positioning of tower and SI components shall be visually shown along with digital indications of all TTS parameters. The PLC shall be programmed to run each MSS, LER and LCC test per the requirements described in Section 6 and also to independently operate and control each function of the SITT. PLC programming software shall be provided to the USAF following completion of SITT project so that future programming changes may be made as needed. Safety interlocks and emergency stop functions, which will prevent personnel injury and damage to SIs and SITT components, shall be provided.

· Data Acquisition System (DAS) – The DAS shall collect data from the load cell, piston displacement potentiometer and pressure transducers. This shall be done with respect to each other and to time. Data points shall be collected and recorded at a minimum rate of 50 data points per second. HAFB has standardized on the use of LABVIEW software for the collection and manipulation of data. This software shall be provided as part of the system and shall be programmed to accomplish its intended purposes.

· Electrical System – A single point source of 3 Phase / VAC electrical power shall be provided by the Air Force at the site of the tower installation. The voltage is yet to be determined. The contractor shall be responsible for all electrical equipment and installation that will be required to deliver this power from this single point to the tower devices. This shall include but not be limited to: electrical cabinets, disconnects, transformers, switches, lights, relays, wiring, conduit, etc. The electrical system and its installation shall conform to all applicable electrical codes.

2.2. The following figures 1 through 9 provide an illustration of the conceptual design and how it would be used to conduct the SI tests:

FIGURE 1 – CONCEPTUAL DESIGN

(LINEAR ACTUATORS IN LOWERED POSITIONS)

FIGURE 2 – CONCEPTUAL DESIGN

(LINEAR ACTUATORS RAISED – ELECTRO-MAGNET

ENERGIZED – WEIGHT SLUGS DETACHED)

FIGURE 3 – USAF CONCEPTUAL DESIGN

(LINEAR ACTUATORS RAISED – ELECTRO-MAGNET

ENERGIZED – WEIGHT SLUGS ATTACHED)

FIGURE 4 – USAF CONCEPTUAL DESIGN

(MSS SI INSTALLED IN TOWER)

FIGURE 5 – MSS SI TEST SEQUENCE

FIGURE 6 – USAF CONCEPTUAL DESIGN

(LER SI INSTALLED IN TOWER)

FIGURE 7 – LER SI TEST SEQUENCE

FIGURE 8 – USAF CONCEPTUAL DESIGN

(LCC SI INSTALLED IN TOWER)

FIGURE 9 – LCC SI TEST SEQUENCE

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