Space launch vehicles and ICBM class missile systems use large quantities of energetic materials as fuel and oxidizer for their propulsion systems. Typically, these propulsion systems contain liquid and/or solid propellants in thousand to million pound quantities. These launch vehicles and missile systems can, under launch conditions, react much more violently than during conditions such as transportation, storage, and handling. Launch conditions include vehicles in a fully pressurized configuration such as during countdowns and rehearsals, and testing on test stands. Pressurized vehicles can present a hazard to a wide area, in some cases miles of exposure. The combination of the potential for large explosions coupled with possible wide dispersion of the threat requires different methods of mitigating explosive hazards than normally utilized for non-dynamic hazards analysis, hazard classification, threat mitigation, and quantity-distance siting.
Support FacilitiesSupport Facilities include those facilities used to store, stage, or process large rocket motors and motor segments. The same facility may be used for both staging and processing these motors. Facility design and operational processing flow must keep the physical movement of these large rocket motors and motor segments to an absolute minimum. Limit the operations performed in these facilities to those associated with the primary function of the facility. There are two basic types of support facilities for large solid rocket motors (LSRM) and motor segments; a Motor Operations and Staging Facility, and a Motor Storage Facility.
The Motor Operations and Staging Facility is primarily used to process and/or assemble LSRMs and motor segments for launch operations. It also has the capability for staging and maintaining motors and/or motor segments. Unlike many explosives operating buildings which exist on military installations, the large motor facilities may have many direct support personnel simultaneously performing different tasks in support of the launch preparation. These personnel must be limited to the minimum number necessary to accomplish the operation. Personnel limits will be established in the operating procedures. Scheduled and unscheduled maintenance may be performed in this facility on motors and segments in the staging area. Limit maintenance of large rocket motors and motor segments in the staging area to periodic maintenance and inspections unless a hazard risk analysis indicates other operations may be safely performed.
The Motor Storage Facility is primarily used for long term storage of motors and/or motor segments. Hazardous operations normally performed in these facilities involve lifting and positioning LSRMs and motor segments. Selected maintenance operations may be performed in these facilities provided they are limited to periodic maintenance inspections using approved procedures.
TheSafety Control Area is an area where personnel and equipment exposure is controlled in order to limit the risk from hazardous explosives operations. For LSRM segments, the Safety Control area is generally a circular area centered where the ordnance task is taking place; it has a radius of inhabited building distance based on the quantity of explosives which may become involved in a mishap. Personnel required to be in the Safety Control Area during an explosives operation will be considered essential personnel; conversely, people who do not meet this definition will be considered nonessential. The large size of motor segments allows multiple operations to be easily conducted simultaneously on a single element, but the potential hazards that one task may present to another task must be carefully assessed before allowing more than one operations to proceed. Personnel performing processing or maintenance tasks on LSRM segments should stay aware of other tasks that may be in progress on the same segment. Test Facilities normally consist of a wide array of test resources to support customers including flight hardware (ballistic, space, sounding rocket launch vehicles and satellites) and ground systems (field test, assembly and storage, launch and on-orbit test facilities). A space test facility typically includes liquid propellant storage tanks or test site instrumentation, facility engineering personnel support buildings and a control center. The facilities normally involve a variety of liquid and/or solid propellants which can produce both mass fire and detonation explosive hazards. System safety engineering hazard analyses of the facilities must be performed to identify the various hazards, their relationships, the safety threat zones, etc. A Launch Complex consists of a group of related facilities used for launching missiles and space vehicles. Facilities generally included are the launch pad(s), liquid propellant storage tanks, site instrumentation facilities, engineering personnel support buildings and a blockhouse. Additional facilities could also include LSRM facilities and spacecraft processing facilities. A launch complex normally involves a variety of explosive hazards, the result of the presence of various quantities of liquid and solid propellants which can produce both mass fire and detonation explosive hazards.
HazardsThe major hazards associated with space launch vehicles and missile prelaunch and propulsion test operations involve large quantities of propellants used in propulsion systems, destruct charges, and high pressure gas systems. In the case of solid propellants, the fuel and oxidizer are already mixed homogeneously and, therefore, the failure scenarios do not have to account for mixing. Liquid propellants, on the other hand, are configured in separate storage or launch vehicle tanks, therefore, the failure scenarios account for the type, amount, and probability of mixing propellants. Liquid propellant scenarios primarily involve leaking or ruptured propellant tanks caused by loss of pressure control, insulation deficiencies, mechanical damage, and/or corrosion. Fuel and oxidizers are normally stored separately, so a maximum credible event would be limited to a fire and/or tank pressure rupture. Normally, differential pressure is used to transfer product from one holding tank to another or to load a launch vehicle. Typical accident events are limited to system leaks, vent and/or scrubber failures, or at worst, a tank rupture caused by over- or under-pressurization. Launch vehicle propellant loading scenarios are discussed in another section. Liquid propellants are loaded serially to further reduce prelaunch mixing hazards.
Solid propellant rocket motors are handled by lifting with cranes or erectors at static test stands, the launch mount, in a processing facility, or by various transportation modes. Typically the maximum credible event (MCE) scenario involves vehicle rollover, or drop impacts during lifting or transportation. Drop impacts on hard surfaces can cause propellant ignition.Launch vehicle assembly processes normally do not involve liquid propellants. Assembly operations for solid propellant rocket motors typically involve the same credible accident scenarios as those listed for handling. Booster checkout normally does not impose additional hazards above and beyond those already listed except that the potential for inadvertent ignition of electro-explosive devices (EEDs) or inadvertent function of propellant system isolation valves is increased during certain electrical system checkouts. At-pad/test stand checkout normally is accomplished after solid propellant and hypergolic propellant stages are assembled and loaded, therefore, multi-faceted threats exist with interaction between hypergolic and solid propellants that can result in fires, pressure ruptures, and propulsive flight. The launch booster, upper stages, and payload final assembly process normally is accomplished on the launch pad. Both solid propellants and hypergolic liquid propellants are present during the final assembly steps. A major threat involves the assembly and encapsulation of spacecraft and upper stages in facilities off the launch complex. These operations normally involve hypergolic propellants loaded in separate propellant tanks. Credible accident scenarios include puncture of one or more of the propellant tanks during assembly or checkout, impact caused by lifting, failure resulting in a dropped system, or over- or under pressurization. Since these propellants are hypergolic; the potential exists for a fire if the fuel comes into contact with an oxidizer. Another major threat involves the toxicity of these propellants. Credible accident scenarios primarily involve handling, lifting, and mating stages with tank rupture accident scenarios the result of impacts caused by improper handling or dropping one or more stages. Ordnance installation may take place in an off-the-pad assembly building or on the launch pad. During and after installation, credible accident scenarios primarily involve inadvertent ignition of EEDs. These devices must not be capable of detonating either the solid or liquid propellant. Inadvertent ignition of these devices can result in significant damage to the vehicle and severe injury or death to personnel. Unless unavoidable, do not load cryogenic liquid propellants on a launch vehicle until after ordnance is installed.
Maximum credible event accident scenarios during propellant loading involve over- or under-pressurization of the propellant tanks and major spills of fuel and/or oxidizer. These scenarios can result in a significant explosive yield.All-Up Vehicle Checkout occurs prior to launch or static firing. During this phase of prelaunch operations the final liquid propellant topping off is completed and in some cases the liquid propellant and high pressure gas systems are brought to flight pressure. All systems are switched to internal power and final systems checks are performed. The MCE involves the fully loaded launch vehicle and payload. Explosive yield is based on static conditions for shock impact on solid propellants and non-dynamic mixing of liquid propellant either by the Confined by Missile (CBM) mode or the Confined by Ground Surface (CBGS) mode.