What really happened to AMSAT Oscar 40? Allan Copland GM1SXX 12/02/2007
Since the demise of AO40, I've seen a number of postings about what happened to this large and ambitious satellite project. Today, I discovered yet another explanation, in the pages of no less than Wikipedia....
http://en.wikipedia.org/wiki/AO-40
An extract from the article is reproduced below...
'Incident':This outlines yet a different scenario from the 'official' ones I've read to date. Perhaps some day, AMSAT will publish a definitive report on what really happened to AO40. I *do* realise that such work does require very careful analysis and that it is quite possible to jump to the wrong conclusions in the absence of hard facts. You only need draw a parallel with the forensic work of the Air Accident Investigation Board who sometimes have to piece together the facts after an air accident in a situation with little 'hard' information and where the analysis process takes many months of painstaking work to reach a meaningful conclusion.
Here's an extract from an AMSAT report about the same event from ..
http://www.amsat.org/amsat-new/satellites/satInfo.php?satID=15&retURL=satellites/all_oscars.php
Shortly after launch a plugged valve vent on the 400 N motor prevented proper
functioning of the burn valves and had probably allowed build-up of fuel
pressure in the cooling coils around the motor bell housing. These coils
apparently ruptured and in the process damaged one or (less likely) both of the
burn valves. During cycling of the pressurization valve the following day, one
component of the fuel apparently escaped from the damaged burn valve at the
motor housing and mixed with residual second fuel component in the motor,
creating a localised explosion. During this cycling (which should have been safe
since the burn valves were indicated in the telemetry as closed) the spacecraft
suddenly went silent. This pressure wave seems to have vented primarily through
the centre section of the spacecraft, damaging the omni antennas on the opposite
end and perhaps removing part of the covering from the omni end of the
spacecraft. AO-40 was recovered several weeks later but several of the
subsystems were no longer functioning.
In January of 2004, AO-40 suffered suffered a catastrophic failure of the main
battery which is clamping the buss voltage at a low level. This shut off the S2
Tx, and probably crashed the IHU-1. Subsequent efforts to recover the satellite
failed, and although the main and aux. batteries were been tied together there
is not enough voltage at this time to recover the satellite.
Perhaps it will be the case that no final report will even be written because of a lack of observable facts. In the meantime, I imagine that we will just have to wait for more facts on the demise of A-O-40 to trickle out.
Perhaps at some time in the future, AMSAT might publish some sort of meaningful presentation on the subject. I'm sure that would be of great interest and of use in planning future missions. In spacecraft and aviation engineering it's standard practice to tag all items (such as plugs and bungs) that need to be removed before a flight or a mission with bright and conspicuous red RBF 'REMOVE BEFORE FLIGHT' tags to ensure safety and success. Even on a shoestring budget, such things are easily produced with nothing more than an ordinary PC and printer and a cheap laminator. It's easy to criticise of course AFTER such an event but success in complex missions results from good operating practices and strict attention to detail. It's normal practice to build reliability in rather than 'inspecting it out'.
The use of RBF tags is standard practice throughout the aviation and space vehicle industry. here's a typical example.
A typical RBF tag. Cheap to buy and easy to make on a home PC.
One would imagine that a vent line plug or bung would also carry one of these RBF tags. In the photos following, you can see AO40 with the RBF tag used to avoid having debris falling into the main motor nozzle.
| AO40 inside the launch adaptor clearly showing an RBF label attached to the rocket motor | The RBF items being removed before flight. Here the main motor nozzle plug is being removed. |
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The end result of the vent line being blocked was catastrophic for AO40. Unlike most rocket propulsion systems, the apogee kick motor on AO40 used storable hypergolic (self igniting) propellants delivered to the combustion chamber by high pressure inert gas (Nitrogen) so the motor used would have been relatively robust and simple design. Hopefully, in time, AMSAT will release more detailed information in future about the reason for the 'burp' as the anomaly has been called in order that useful lessons might be learned from the loss of AO10.
73 Al.
GM1SXX
Propellant Flow Assembly(AMSAT)
The 400 newton Propulsion system