1 – “Electro-Explosive Device” (EED) vs. “Laser-Initiated Deployment”
Segue abaixo a comparação feita entre os dois principais sistemas de iniciação de detonadores mais utilizados na atualidade, com o objetivo de mostrar que o sistema que utiliza laser é mais seguro (PATEL, 2005).
“12.3.1 Electro-Explosive Device”
“This is the traditional method of deployment, which is also known as the pyro-technique ordnance. It uses an electro-explosive device (EED), in which electrical energy is supplied to ignite the squibb of explosive powder.
The resulting force then deploys the component, typically under a springloaded force. The EED is ignited when a certain current deposits a certain amount of energy in a specified time. For safety reasons, it must withstand a certain minimum energy without igniting. A typical EED is rated at 1A–1W no fire, and 4A–4W sure fire.
The EED requires heavy shielding and great care with regard to EMI pickup. Moreover, the EED explosive is thermal and shock sensitive.
Therefore, installation of sensitive EED explosives is sometimes done at the launch pad, which costs much more than at the factory. A pyro harness is routed separately from the power and signal harness to minimize the EMI concerns for safety. EED deployment technology, although used for several decades, have some disadvantages, such as:
- All spacecraft components must be designed to withstand severe pyro shock excitation.
- High safety related costs in documenting, reporting alerts, and all other stringent regulations on EEDs must be complied with.
- Some manufacturers install EED squibs at the launch pad, while most install at the factory. In the latter case, the spacecraft is transported as a class 1 explosive (sensitive to thermal and shock environments), and this adds expense.”
“12.3.2 Laser-Initiated Deployment”
“Figure 12.3 shows the laser-initiated ordnance schematic, where the light emitted by diode D1 is transmitted to the squib by an optical fiber. The photon energy deposited in the squib fires the explosive. After the firing, a sense light is sent by pulsing D2 and sensing the transmission, reflection or refraction of the sense light. This is to confirm that the squib has been fired. This technology has been space qualified and flown. It has the following advantages over EEDs:
- It is insensitive to EMI, RFI, ESD, EMP, and cross talks. Hence, it eliminates accidental firing and related human safety issues. This reduces the cost not only in flight, but also in the factory, in transportation, and at the launch pad.
- insensitive to harness and explosive placements”
“FIGURE 12.3 Laser-initiated ordnance schematic.”
2 – Comparação de vários sistemas de iniciação de detonadores (BELL et al., 2000).
2.1 – EBW vs. Laser
2.2 – Table I: Electrical Initiation Device Comparisons (Typical).
2.3 – Table II: Electrical Initiation Device System Comparisons (Typical).
2.4 – Table III: Device Characteristics (Typical).
2.5 – Table IV: Approach Selection Factors.
2.6 – Safety Comparison – Laser Diode to EBW System.
BELL, I. Fahey, W. D. e Valenti, R. M. The Changing Pattern of Ordnance Initiation. SAFE (Europe) SYMPOSIUM 2000. Página da Internet. Disponível em < URL: http://www.safeeurope.co.uk/media/2789/fahey_00.pdf >. Acessado em 2013.
PATEL, M. R. Spacecraft power systems. 2005. Página da Internet. Disponível em < URL: http://www.e-reading-lib.org/bookreader.php/135136/Patel_-_Spacecraft_Power_Systems.pdf > p. 322 e 323. Acessado em 2013.