Interplanetary Distress Beacon
Summary:
The rapid increase in human space flight predicted to take place during the next few years has led me to consider how a common emergency system can be developed:
The information below is a compilation of my thoughts on this subject so far:
Background:
It is likely that human space travel will be restricted to low / high earth orbit, exorbital trips to Luna ('the moon') and possibly Mars.
Therefore, any proposed system has to be capable of operation within this area, with options for future expansion.
Sattellite - based repeater necklace:
It is proposed that a standard, off the shelf, reliable and proven design providing basic voice and data communication links be used. In addition to the standard functionality, the sattellite will provide repeater and logging functions for a dedicated and agreed 'distress' band. 
This sattellite design would be used in the following configuration:
Luna would be provided with three of the sattellites, in secure orbit, preferably at a height where each is in line of sight at all times with the other two. This would provide basic reliable communications to Earth from any part of Luna, and would provide surface to surface Luna based comms links. The distress band would never be utilised for general comms, being exclusively available for emergency situations.
Mars, perhaps at a later date, but BEFORE any manned mission took place, would be provided with the same design of sattellite. However, due to the greater planetary diameter, it is proposed that no fewer than 6 sattellites be placed in orbit. This should provide some measure of redundancy, as any failed sattellite would take a considerable time to replace from Earth.
Basic design:
Upon activation, a simple transponder emits an identy code followed by available additional information.
The additional information may contain any or all of thefollowing:
- Last known health status of craft
- Error messages prior to failure
- Time and date of critical event
- Nature of critical event
- Intended destination of craft
- Count of humans onboard
- Cargo inventory
- Messages from surviving members onboard
- Last known position and trajectory
A seperate power source should be available to the IDB. Solar power is a good option.
Links to onboard systems:
The IDB will monitor the status of the craft on regular (1 second?) intervals, and will be set to activate automatically if a critical state is recognised, or no information is recieved for an extended period - about 60 minutes.
The IDB can also be activated manually (See activation criteria above).
Design detail:
Each IDB would have a unique ID number, similar to a MAC address, and registered against the owner, holding some basic details of the craft size, capability and design purpose. This information would provide important basic data necessary to the planing of any rescue or recovery mission. 
Activation criteria and consequences:
An IDB transponder, once activated, is a call for aid. Huge resource may be invested along with risk to personnel, in order to attept any sort of rescue.
Therefore, it is acceptable that any craft activating an IDB in a non-critical situation, whatever the excuse, suffers the consequence of loss of ownership and the craft and (non-human) cargo become available for salvage.
Activation points should be available in each of the 'safe zones' on a spacecraft.
Earthbound monitoring:
It is expected that monitoring would take place by both professional and goverment bodies, and by interested individuals (Radio hams). 
Other uses:
Satellites could be used to provide GPS positioning information for surface travel and landing craft.
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