This article originally appeared in Issue #014, February 2011, of the downloadable PDF magazine.
The EF2 is a flare gun that fires a light emitting disc that also contains a radio transmitter to send a distress message. You can use the standard distress message or record your own.
The EF2 is somewhat larger and heavier than a standard pistol. The muzzle is shaped to accommodate the “flare” discs, and the chamber is larger to accommodate the propellant cartridges. Unlike a pistol, the EF2 does not automatically eject spent propellant cartridges. Additionally, there is an energy cell and a small data transfer unit built in to the butt to facilitate loading the EBD-2 discs with a distress message (and, on the EF2-GPS, location data).
The EF2-GPS variant can be linked to GPS receivers that output location data in standard format. There is no inbuilt GPS capability. A thirty-second voice recording may be stored on all discs that support user-programmable distress messages; discs that support recording of location data can also store up to four hours of it.
The EF2 and EF2-GPS are intended to be used on worlds with atmospheres (very thin or denser); the propellant cartridges are unsuitable for use in vacuum and near-vacuum.
Discs are about 10cm in diameter, and 1.5cm thick. They are loaded into the gun edgewise from the muzzle. Propellant cartridges are loaded into the gun from the breech.
There are a variety of discs available:
The EBD (Emergency Broadcast Disc) can store a thirty-second voice recording as a distress message. These discs are shipped preloaded with a standard message; once activated, they will broadcast continuously for 48 hours. It may be used with the EF2 or EF2-GPS, but it cannot take advantage of the additional capabilities of the EF2-GPS. The EBD emits a bright, actinic light for a maximum of 60 seconds of flight, if activated with a propellant cartridge. If activated without the propellant cartridge, the disc remains in the gun, acting as an emergency radio transmitter only.
The EBD-2 is a modification of the EBD which includes the ability to record up to four hours of location data, if used with the EF2-GPS. When used with the EF2, it is not possible to record location data.
Both the EBD and EBD-2 come in “S” variants (the EBD-S and EBD-2-S) where the light flashes in a stroboscopic pattern, extending the life of the light to a maximum of 120 seconds.
Discs are not self propelled; a single-use propellant cartridge is required for deployment to altitude (and to activate the visible light beacon). If “fired” without a propellant cartridge, the disc will remain in the gun, but the distress transmission, including both recorded voice and location data, will be initiated. The gun can be stored with the Broadcaster Disc inserted but for safety reasons the propellant should not be inserted until the gun is ready for use. Lights indicate the status of the propellant cartridge and disc. A yellow light indicates the disc is inserted; a green light indicates both the disc and the propellant are inserted.
Propellant cartridges come in three variants:
L cartridges are intended for use in low-gravity environments, to a maximum of 0.4g. If used in higher gravity, the disc may not achieve sufficient height to be noticed. Care should be used in gravitational fields of less than 0.1g, as there is increased risk of the disc achieving escape velocity.
S cartridges are intended for use in standard-gravity environments, from about 0.4g to about 1.6g. Use in lighter-gravity environments may allow the disc to drift too far away during flight to act as a reasonable locator beacon (or, in extremely light gravity, the disc may achieve escape velocity); use in heavier gravity may not permit the disc to achieve sufficient altitude to be noticed.
H cartridges are intended for use in environments where gravity is between 1.6g and 3g. Use in very light gravity will cause the disc to achieve escape velocity; use in light gravity may allow the disc to drift too far to be a useful locator; use in heavier gravity, coupled with the increased atmospheric density normal for such environments, risks bursting the chamber at the breech and causing serious injury to the user.